U.S. patent application number 14/776088 was filed with the patent office on 2016-05-05 for wound dressing sealant and use thereof.
The applicant listed for this patent is SMITH & NEPHEW PLC. Invention is credited to Sarah Jenny Collinson, Nicholas Charlton Fry, Philip Gowans, Edward Yerbury Hartwell, Marcus Damian Phillips.
Application Number | 20160120706 14/776088 |
Document ID | / |
Family ID | 70860445 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160120706 |
Kind Code |
A1 |
Collinson; Sarah Jenny ; et
al. |
May 5, 2016 |
WOUND DRESSING SEALANT AND USE THEREOF
Abstract
Embodiments disclosed herein are directed to sealing
compositions for negative pressure treatment systems and wound
dressing systems, devices containing the same, apparatuses, uses
and methods for creating a main wound dressing portion for use in
wound care, more particularly for sealing a trimmable dressing,
having a main dressing portion or cell in fluid (e.g., gas)
communication with additional dressing portions or cells, for use
in woundcare, more particularly that may be used for the treatment
of wounds. In particular, some embodiments are directed to
compositions for improving the versatility of wound dressings for
wounds of different shapes or sizes.
Inventors: |
Collinson; Sarah Jenny;
(Heslington, GB) ; Fry; Nicholas Charlton;
(Heslington, GB) ; Gowans; Philip; (Heslington,
GB) ; Hartwell; Edward Yerbury; (Heslington, GB)
; Phillips; Marcus Damian; (Heslington, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SMITH & NEPHEW PLC |
London |
|
GB |
|
|
Family ID: |
70860445 |
Appl. No.: |
14/776088 |
Filed: |
March 14, 2014 |
PCT Filed: |
March 14, 2014 |
PCT NO: |
PCT/GB2014/050786 |
371 Date: |
September 14, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61800040 |
Mar 15, 2013 |
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61828604 |
May 29, 2013 |
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61829187 |
May 30, 2013 |
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61906865 |
Nov 20, 2013 |
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61907350 |
Nov 21, 2013 |
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Current U.S.
Class: |
604/319 |
Current CPC
Class: |
A61F 13/0216 20130101;
A61F 13/00068 20130101; A61L 15/58 20130101; A61F 13/0253 20130101;
A61M 1/0088 20130101; A61M 2205/7536 20130101; A61L 15/42 20130101;
A61L 15/58 20130101; C08L 83/04 20130101 |
International
Class: |
A61F 13/02 20060101
A61F013/02; A61M 1/00 20060101 A61M001/00; A61L 15/58 20060101
A61L015/58 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2013 |
GB |
1309662.3 |
May 30, 2013 |
GB |
1309709.2 |
Claims
1. A system for treatment of a wound site, the system comprising: a
dispensable composition for wound care; and a wound dressing
comprising: a backing layer having an upper surface and a lower
surface and defining a perimeter configured to be positioned over
skin surrounding the wound site; one or more transmission layers
configured to be positioned below the backing layer; and a port
configured to transmit negative pressure through the backing layer
for the application of topical negative pressure at the wound site;
wherein the wound dressing is configured for removal of a portion
of the wound dressing directly enclosing the transmission layer to
create a main wound dressing portion with one or more exposed
portions wherein the transmission layer is exposed at a portion
thereof, wherein the dispensable composition is configured to form
a seal at a location of the one or more exposed portions.
2-12. (canceled)
13. The system of claim 1, wherein the dispensable composition
comprises a silicone curing system including one, two or more parts
silicone.
14. (canceled)
15. The system of claim 1, wherein the dispensable composition
comprises an RTV-2 silicone curing system.
16. The system of claim 1, wherein the dispensable composition
comprises, apportioned between at least one Part A and at least one
Part B: one or more alkenyl-group containing polymers (i) having at
least one alkenyl group or moiety per molecule, one or more
SiH-containing polymers (ii) having at least one Si--H unit per
molecule; a catalyst (iii) for curing by addition of
alkenyl-containing polymer (i) to SiH-containing polymer (ii);
wherein the dispensable composition cures to an elastomer which is
fluid-impermeable at an exposed surface thereof.
17. The system of claim 1, further comprising, for dispensing the
dispensable composition, a syringe or static mixer having a nozzle
head comprising a spreader tip with plural nozzles.
18. (canceled)
19. The system of claim 1, wherein the dispensable composition is
selected from compounds including siloxanes, modified siloxanes,
polyester, polyether urethanes, elastomeric polyether polyesters,
polyglycolic acid, ethyl vinyl acetate, polyacrylate, polyacid
derivatives of polysaccharides, carboxyalkylcellulose,
carboxyalkylchitosan and copolymers thereof, and hybrids of the
compounds, the hybrids including copolymers, entangled systems and
mixtures thereof.
20. (canceled)
21. The system of claim 1, further comprising cooperative
dispensing device comprising at least one sealed barrel or at least
one cassette for a static mixer.
22-34. (canceled)
35. A method of treating a wound, comprising: providing a wound
dressing comprising: a backing layer; and one or more transmission
layers positioned beneath the backing layer; removing a portion of
the wound dressing to create a main wound dressing portion with one
or more exposed portions, wherein the one or more transmission
layers is exposed at the one or more exposed portions; positioning
the main wound dressing portion over a wound; sealing the main
wound dressing portion to skin surrounding the wound; and
dispensing a composition to a location at or within the one or more
exposed portions of the main wound dressing portion thereby sealing
the one or more exposed portions.
36. (canceled)
37. (canceled)
38. The method of claim 35, wherein dispensing the composition
comprises internally impregnating the one or more transmission
layers at the one or more exposed portions.
39. (canceled)
40. (canceled)
41. The method of claim 38, further comprising impregnating the one
or more transmission layers to a distance in the range of 0.2 to 25
mm within the one or more transmission layers.
42. The method of claim 35, further comprising applying negative
pressure to the wound through the backing layer of the main wound
dressing portion.
43. The method of claim 42, further comprising drawing the
dispensable composition up to 25 mm within the one or more
transmission layers at the one or more exposed portions via the
negative pressure.
44. The method of claim 42, wherein the wound dressing exhibits no
change or substantially no change in compressibility at the
location of the seal on initiation of the negative pressure.
45. The method of claim 42, further comprising dispensing the
dispensable composition with formation of an air-tight elastomer
which is capable of containing the negative pressure.
46. The method of claim 35, wherein the dispensable composition has
a viscosity in the range of 11 and 14 Pas.
47. The method of claim 35, wherein the dispensable composition,
when cured, is conformable.
48. The method of claim 35, further comprising subjecting the
dispensable composition to shear forces during application to the
one or more exposed portions, wherein the dispensable composition
reduces viscosity when subjected to the shear forces.
49. The method of claim 35, wherein the dispensable composition has
a curing time at 23.degree. C. in the range from 0.5 to 5 min.
50. The method of claim 35, wherein the dispensable composition has
a curing time at 32.degree. C. in the range from 0.5 to 7 min.
51. The method of claim 35, further comprising dispensing the
dispensable composition directly at the exposed portion through an
exposed face of the one or more transmission layers.
Description
[0001] Embodiments described herein relate to compositions, devices
incorporating the same, apparatuses, kits, their uses in wound
care, and methods for the treatment of wounds and for creating a
main wound dressing portion for use in wound dressing, for example
in advanced wound management, particularly, but not exclusively, in
negative pressure therapy (TNP therapy).
[0002] Different types of wound dressing exist for aiding in the
healing process of a human or animal subject in need thereof. These
include different types of materials, for example, gauze and/or
foam with overlying drapes, and composites thereof, provided in
assembled layers and in a selection of sizes or shapes, typically
square or rectangular shapes. Advanced wound management dressings
address specific wound therapies by means of tailored dressing
components, particularly, but not exclusively, TNP therapy
dressings incorporate a means for transmitting negative pressure to
the wound, and a fluid-tight drape for enclosing a negative
pressure, provided as independent components or as a composite
dressing.
[0003] We have found, as a first problem, that certain wounds and
body topography cannot be adequately dressed using the existing
selection of composite TNP dressings, for example vein harvest
wounds extending the length of a subject's leg exceed available
dressing dimensions or diabetic foot ulcers where complex
topography prevents rectangular designs from conforming adequately
to tight body contours.
[0004] We have found, as a further problem, that advanced wound
therapy and in particular TNP therapy, cannot therefore be applied
to those wounds which perhaps have the greatest need for this
therapy, but rather conventional wound care must be relied on.
[0005] We have therefore defined a need for improved dressings,
more particularly but not exclusively composite TNP therapy
dressings, which exhibit enhanced adaptability in wound care.
[0006] It is an aim of certain embodiments to at least mitigate the
above-mentioned problems. Certain embodiments disclosed herein
relate to improved compositions and their use in combination with
dressings to confer enhanced adaptability in wound care, preferably
in TNP wound care. Dressings applied in combination with such
compositions may have advantages over traditionally applied
dressings which may be more difficult to apply, particularly around
wounds such as lengthy incision sites or irregularly shaped wounds.
Dressings applied to such wounds with use of such compositions may
be of comparable effectiveness to dressings applied in traditional
manner to more regular sized or shaped wounds. Wounds dressed with
such dressings in combination with such compositions may enable the
application of TNP therapy. Also disclosed are improved methods of
use and systems for use of the compositions in combination with
dressings, preferably in negative pressure wound therapy.
[0007] It is an aim of certain embodiments to provide means to
enable composite wound dressings to more universally be used on
wounds of different shapes or sizes.
[0008] It is an aim of certain embodiments to provide a dispensable
sealant composition for a composite wound dressing which can more
universally be used on wounds of different shapes or sizes.
[0009] It is an aim of certain embodiments to provide a device
including such composition for dispensing in improved manner to a
composite wound dressing to more universally be used on wounds of
different sizes or shapes.
[0010] It is an aim of certain embodiments to provide a wound
dressing kit including a composite dressing, preferably an advanced
wound management dressing, more preferably a composite TNP therapy
dressing, together with a sealant composition, adapted to be
applied in conjunction at a wound site.
[0011] It is an aim of certain embodiments to provide an apparatus
in the form of a composite wound dressing which can more
universally be used on wounds of different shapes or sizes.
[0012] It is an aim of certain embodiments to provide a method of
treating a wound by sealing a composite dressing which can more
universally be used on wounds of different shapes or sizes.
[0013] In one embodiment, there is provided a dispensable
composition for woundcare, wherein the composition is dispensed
into a wound dressing location, said wound dressing comprising:
[0014] a backing layer having an upper surface and a lower surface,
otherwise termed a backing sheet having two faces, and defining a
perimeter configured to be positioned over skin surrounding a wound
site; [0015] an optional wound contact layer; [0016] one or more
transmission layers provided directly or indirectly to the lower
backing layer surface, or otherwise configured to be positioned
below the backing layer, or otherwise positioned at or on one side
of one face of the backing sheet, [0017] or enclosed between the
backing layer and the wound contact layer, where present; and
[0018] a port configured to transmit negative pressure through the
backing layer for the application of topical negative pressure at
the wound site wherein removing a portion of the wound dressing
directly enclosing the transmission layer to create a main wound
dressing portion with one or more exposed portions wherein the
transmission layer is exposed at a portion thereof, [0019] said
exposed portion(s) being the location as hereinbefore defined, the
dispensed composition seals the exposed portion(s).
[0020] The composition is particularly for creating a main wound
dressing portion for use in wound care more particularly for
sealing a trimmable dressing, having a main dressing portion or
cell in fluid (e.g., gas) communication with additional dressing
portions or cells, for use in woundcare, more particularly for
treatment of a wound site,
[0021] The composition may be dispensed into or onto the exposed
portion or both. By this means the dispensed composition
impregnates or envelopes the exposed portion or both.
[0022] Preferably the dispensed composition impregnates the exposed
portion. This has the advantage of enhanced robustness whereby the
seal forms part of the dressing.
[0023] Alternatively the dispensed composition envelopes the
exposed portion. This more resembles a simple repair applied to the
upper surface of the dressing. Choice of dispensing by impregnation
or enveloping may be selected according to the nature of the
dressing to be sealed, in particular its laminar structure, and
more particularly the laminar structure at the exposed portion
thereof. Optionally the composition impregnates and additionally
envelopes the sealed portion thereby providing a seal operating at
internal surfaces of the transmission layer and external surfaces
of the dressing. Composition may be dispensed directly at the
exposed portion through the exposed face thereof, or indirectly via
the backing layer or backing sheet or via the optional wound
contact layer, thereby internally penetrating the exposed
portion.
[0024] Some embodiments may further comprise a device comprising
the composition, an apparatus in the form of a dressing for use
with the composition, kits thereof, uses and methods of therapy.
Some embodiments may further comprise a source of negative pressure
configured to supply negative pressure through the port. Some
embodiments may further comprise retention strips or sealing strips
configured to hold in place or seal the dressing to skin
surrounding a wound.
[0025] In another embodiment, a method of creating a main wound
dressing portion for use in dressing or otherwise of treating a
wound comprises: [0026] providing a wound dressing as hereinbefore
defined comprising: [0027] a backing layer, otherwise termed a
backing sheet; [0028] an optional wound contact layer; and [0029]
one or more transmission layers as hereinbefore defined [0030]
removing a portion of the wound dressing to create a main wound
dressing portion with one or more exposed portions; [0031]
optionally positioning the main wound dressing portion over a wound
and sealing the main wound dressing to skin surrounding the wound,
[0032] and dispensing a composition as hereinbefore defined to a
location comprising the one or more exposed portions of the main
wound dressing portion thereby sealing the exposed portion(s); and
[0033] optionally applying negative pressure to the wound through
the backing layer of the main wound dressing portion.
[0034] Sealing a wound dressing to skin may be prior to creating a
main wound dressing portion and prior to dispensing composition or
may be subsequent to creating a main wound dressing portion and
prior to or subsequent to dispensing composition. Accordingly the
method may be a method relating to dressing manufacture for use in
dressing wounds or may be a method relating to dressing wounds. As
is used herein the backing layer represents a gas impermeable
membrane. Also referred to herein as wound cover or drape. Some
examples of materials suitable for backing layers included thin
polyurethane films, which may optionally be coated with adhesive.
It is also possible that a number of laminates be brought together
to form multi-laminar backing layers, in such cases the description
of the upper and lower surfaces of the backing layer are taken to
mean the upper and lower surfaces of the complete backing
layer.
[0035] As is used herein, a dressing also comprises one or more
transmission layers and other layers (such as absorbent material)
positioned beneath the backing layer. For example, one or more
transmission layers or other layers may be positioned or enclosed
between a backing layer and an optional wound contact layer, for
example, sealed therebetween. The transmission layer(s) may be in
turn positioned between the backing layer and (optional wound
contact layer and) a wound site over which the dressing is
configured to be positioned, for example sealed therebetween.
[0036] A transmission layer as described herein allows transmission
of fluid such as air, and optionally additionally other gases and
liquids, away from a wound site into upper layer(s) of the wound
dressing, the port, and therefrom to a fluid canister if present
and/or into a negative pressure pump. A transmission layer may
assist in maintaining an open air channel to communicate negative
pressure over the wound area even when the dressing is handling
substantial amounts of exudates. The layer should remain open under
the typical pressures that will be applied during negative pressure
wound therapy. Preferably, a transmission layer remains open over
an area corresponding to the wound site, and thereby ensures that
the whole wound site sees an equalized negative pressure.
Alternatively the transmission layer may comprise one or more
specific air paths which remain open, such as in and between
bridging portions of a wound dressing as described further
below.
[0037] A transmission layer may comprise voids or may comprise one
or more materials which transmit fluid, or may be a combination
thereof. The transmission layer may incorporate other functional
materials provided that it is still capable of transmitting
negative pressure, and preferably also liquid fluids. In some
embodiments, the transmission layer is capable of transmitting
wound exudates and other compositions of matter.
[0038] Some examples of materials suitable for a transmission layer
include a three dimensional structure, for example, a knitted or
woven spacer fabric (for example Baltex 7970 weft knitted
polyester), although other materials such as foam (e.g.,
reticulated foam), nonwoven materials (e.g., an acquisition
distribution layer as described below) could of course be used.
Alternatively or additionally the transmission layer may
incorporate absorbent material and absorb liquid drawn away from
the wound under the applied negative pressure.
[0039] Some embodiments described herein include a trimmable
dressing, having a main dressing portion or cell in fluid (e.g.,
gas) communication with additional dressing portions or cells. As
is used herein, a main dressing portion represents a portion which
has a size or shape or profile or articulation which is compatible
with a wound or wound site to be dressed. One or more additional
portions or cells may be removed to provide a dressing having a
size or shape or profile or articulation which is to be compatible
with a wound or wound site to be dressed. Preferably a large
surface area, or elongate main dressing portion is provided to
dress a similarly large surface area or elongate wound; for example
portions or cells may be retained to provide such a large surface
area, or elongate main dressing portion, or portions or cells may
be removed to dress a correspondingly reduced surface area or
reduced length wound. preferably a shaped main dressing portion is
provided to dress a similarly shaped wound; or a shaped main
portion is provided to dress a wound incorporating or adjacent a
protrusion such as a device, for example a pin, or such as a body
part such as a digit, for example one or more additional portions
or cells may be conformed to provide a shaped dressing; preferably
a profiled main dressing portion is provided to dress a similarly
profiled wound or wound site, such as a wound located on complex
body topography, for example one or more additional portions or
cells may be conformed to provide a profiled dressing; preferably
an articulated main dressing portion is provided to dress a
similarly articulated wound or wound site such as a wound located
on a joint, for example one or more additional portions or cells
may be articulated.
[0040] A main dressing portion or portions and additional portions
or cells as described herein may be connected by one or more bridge
portions including one or more transmission layers as described
above, in other words a bridging portion underneath the backing
layer, or otherwise positioned at or on one side of one face of the
backing sheet, the bridging portion comprising at least one
material layer configured to transmit negative pressure from the
first portion through the bridging portion. In some embodiments,
the at least one material layer in the bridging portion has a
smaller dimension or a different material structure than a
corresponding dimension or material structure of the first portion,
for example the one or more transmission layers comprising one or
more bridging portions having a smaller width than adjacent
portions of the one or more transmission layers or than the main
dressing portion, or the one or more transmission layers comprising
one or more bridging portions having a smaller height than adjacent
portions of the one or more transmission layers or than the main
dressing portion.
[0041] As is used herein, an exposed portion of transmission layer
represents a portion which the backing layer is not configured to
enclose and seal against a surface such as a wound site, for
example the backing layer and optional wound contact layer do not
enclose the transmission layer. For example, a section of
transmission layer and overlying backing layer is absent, whereby
the remaining transmission layer terminates in open-ended manner,
or the backing layer may be partially absent, and additionally the
optional wound contact layer may be partially absent, at which the
transmission layer terminates in open-ended manner. It may be
desired to seal such exposed portion of transmission layer (and
exposed portions of other layers). As is used herein, sealing
represents sealing in manner to contain fluid, more preferably in
manner to contain negative pressure.
[0042] As is used herein, fluid represents liquid and gas. However
it is not intended that "fluid" should encompass "vapour", a
favourable moisture vapour transmission rate (MVTR) being a
requirement of dressings envisaged herein. The backing layer is
impermeable or substantially impermeable to fluids including wound
exudate. The backing layer is air-tight or substantially air-tight,
whereby a negative pressure may be maintained at a wound site to
which the dressing is applied and sealed with the composition.
Wound exudates and other fluids may be contained within the wound
site and/or dressing and any collection means associated
therewith.
[0043] As is used herein, a dispensable composition represents a
composition having viscosity in the range from 5 to 300 Pas,
preferably 10-100 Pas. Viscosity (q) is determined in accordance
with DIN EN ISO 3219:1994, Annex B. For some embodiments viscosity
is in the range 20-80 Pas. The composition parts may be combined
and allowed to partially cure to a suitable viscosity for
application, or may have properties such that a suitable viscosity
reduction is achieved when subject to shear forces during
application. The composition may have flow properties such that it
can be drawn within transmission layer(s) at exposed portion(s) by
the prevailing negative pressure and then cure. The composition ay
for example flow to a distance of up to 25 mm, eg 1 mm to 25 mm.
The cured sealant preferably retains a degree of flow or
conformability, for example extensibility, such that it can
accommodate the dynamic conditions encountered when on the
skin.
[0044] As is used herein a TNP system may be operated with any
suitable source of negative pressure, including and not limited to
pumps, springs (SNaP) and any other functional equivalents.
[0045] As is used herein, a wound dressing represents a composite
wound dressing, preferably an advanced wound management dressing
tailored to include specific wound therapy provision for i.a.
management of wound exudates (eg ALLEVYN Gentle Border, DURAFIBER,
ALLEVYN Life), infection management (eg ACTICOAT, IODOSORB), iv
site care (eg IV3000), management of compromised skin about the
wound, TNP (eg RENASYS F/AB, PICO, KCI Prevena, Kalypto Medical Inc
NPD1000 NP Wound Therapy System), post operative care such as
surgical drapes (eg OPSITE), temporary bioskin dressings (eg
BIOBRANE) and the like, most preferably a TNP dressing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0046] FIG. 1 illustrates an embodiment of a wound treatment
system;
[0047] FIGS. 2A-D illustrates the use and application of an
embodiment of a wound treatment system onto a patient;
[0048] FIG. 3A illustrates an embodiment of a wound dressing in
cross-section;
[0049] FIG. 3B illustrates another embodiment of a wound dressing
in cross-section;
[0050] FIG. 3C illustrates another embodiment of a wound dressing
in cross-section;
[0051] FIGS. 4A and 4C illustrate an exploded view of an embodiment
of a wound dressing;
[0052] FIG. 4sB and 4D illustrate a cross sectional view of an
embodiment of a wound dressing;
[0053] FIGS. A1-A4 and A7 illustrate embodiments of commercially
available wound dressings trimmable for sealing with the present
composition, to size, to profile on complex topography, or to shape
around a fixation device or for puncture repair;
[0054] FIGS. A5-A6 illustrate the use and application and sealing
of embodiments of FIGS. A1-A4 onto a patient;
[0055] FIGS. B1-B2 and C1-C7 illustrate the spacer nozzle
relationship of an applicator for dispensing composition to a
trimmable dressing; [0056] and C1-C3 also illustrate the sealing of
embodiments of wound dressings; and C6 also illustrates a novel
nozzle head for an applicator;
[0057] FIG. 5A illustrates an embodiment of a wound dressing
trimmable at a bridge portion;
[0058] FIG. 5B illustrates another embodiment of a wound dressing
trimmable at a bridge portion;
[0059] FIGS. 5C and 5D illustrate the use and application and
sealing of embodiments of FIGS. 5A-5B onto a patient;
[0060] FIG. 6 illustrates an embodiment of a trimmable wound
dressing comprising a plurality of portions or cells;
[0061] FIG. 6II illustrates the use and application and sealing of
an embodiment of FIG. 6 onto a patient;
[0062] FIG. 7 illustrates an embodiment of a trimmable T-shaped
wound dressing comprising a plurality of portions with multiple
port attachment sites;
[0063] FIG. 7II illustrates the use and application and sealing of
an embodiment of FIG. 7 onto a patient;
[0064] FIG. 8 illustrates an embodiment of a trimmable wound
dressing with multiple port attachment sites; and
[0065] FIG. 8II illustrates the use and application and sealing of
an embodiment of FIG. 8 onto a patient.
[0066] FIGS. 9A and 9B illustrate one embodiment of spacer layer
material;
[0067] FIGS. 10A-10D illustrate one embodiment of acquisition
distribution layer material;
[0068] FIGS. 11A and 11B illustrate one embodiment of absorbent
layer material;
[0069] FIGS. 12A and 12B illustrate one embodiment of obscuring
layer material;
[0070] FIG. 13 illustrates one embodiment of an adhesive spread on
cover layer material;
[0071] FIGS. 14A-14B illustrate one embodiment of a trimmable
dressing having a reduced height bridging portion;
[0072] FIG. 15 illustrates an embodiment of a trimmable wound
dressing comprising a plurality of portions or cells;
[0073] FIGS. 16A and 16B illustrate another embodiment of
acquisition distribution layer material; and
[0074] FIGS. 17A through 17C illustrate another embodiment of
acquisition distribution layer material.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0075] Embodiments disclosed herein relate to compositions,
devices, apparatuses, uses, kits and methods of treating a wound
with reduced pressure, including pump and wound dressing components
and apparatuses. The apparatuses and components comprising the
wound overlay and packing materials, if any, are sometimes
collectively referred to herein as dressings, unless otherwise
indicated or intimated. Throughout the specification, the terms
sealant and composition are hereinafter used interchangeably unless
otherwise indicated or intimated.
[0076] It will be appreciated that throughout this specification
reference is made to a wound. It is to be understood that the term
wound is to be broadly construed and encompasses open and closed
wounds in which skin is torn, cut or punctured or where trauma
causes a contusion, or any other superficial or other conditions or
imperfections on the skin of a patient or otherwise that benefit
from reduced pressure treatment. A wound is thus broadly defined as
any damaged region of tissue where fluid may or may not be
produced. Examples of such wounds include, but are not limited to,
abdominal wounds or other large or incisional wounds, either as a
result of surgery, trauma, stemiotomies, fasciotomies, or other
conditions, dehisced wounds, acute wounds, chronic wounds, subacute
and dehisced wounds, traumatic wounds, flaps and skin grafts,
lacerations, abrasions, contusions, burns, diabetic ulcers,
pressure ulcers, stoma, surgical wounds, cosmetic wounds, trauma
and venous ulcers or the like. Wounds may include readily
accessible and difficult to access wounds, exposed and concealed
wounds, large and small wounds, regular and irregular shaped
wounds, planar and topographically irregular, uneven or complex
wounds, more preferably on a site selected from the torso, limb and
extremities such as heel, sacrum, axial, inguinal, shoulder, neck,
leg, foot, digit, knee, axilla, arm and forearm, elbow, hand or for
sealing a crevice adjacent or adjoining a wound site, selected from
such as sacral cleft, fossa and the like.
[0077] It will be understood that embodiments of the present
disclosure are generally applicable to use in topical negative
pressure ("TNP") therapy systems. TNP therapy sometimes referred as
vacuum assisted closure V.A.C..RTM. or negative pressure wound
therapy (NPWT) using sub-atmospheric pressure is applicable to a
broad range of wounds such as chronic wounds, incisional wounds,
open wounds and abdominal wounds or the like.
[0078] Briefly, TNP assists in the closure and healing of many
forms of wound, by reducing tissue oedema; encouraging blood flow
and granular tissue formation; removing excess exudate and may
reduce bacterial load (and thus infection risk). In addition, the
therapy allows for less disturbance of a wound leading to more
rapid healing. TNP therapy systems may also assist in the healing
of surgically closed wounds by removing fluid and by helping to
stabilize the tissue in the apposed position of closure. A further
beneficial use of TNP therapy can be found in grafts and flaps
where removal of excess fluid is important and close proximity of
the graft to tissue is required in order to ensure tissue
viability.
[0079] During TNP therapy, a suction source such as a vacuum pump
or the like is utilised to create a negative pressure region. That
is to say, a region where an experienced pressure is below that of
the surroundings. The suction source creates a negative pressure
via a dressing or drape positioned over and sealed about or around
the periphery of the wound. Wound exudate and other potentially
harmful material is enclosed under the dressing or drape and
extracted therefrom.
[0080] As is used herein, reduced or negative pressure levels such
as -X mmHg, represent pressure levels that are below standard
atmospheric pressure, which corresponds to 760 mmHg (or 1 atm,
29.93 in Hg, 101.325 kPa, 14.696 psi, etc.). Accordingly, a
negative pressure value of -X mmHg reflects absolute pressure that
is X mmHg below 760 mmHg or, in other words, an absolute pressure
of (760-X) mmHg. In addition, negative pressure that is "less" or
"smaller" than X mmHg corresponds to pressure that is closer to
atmospheric pressure (e.g., -40 mmHg is less than -60 mmHg).
Negative pressure that is "more" or "greater" than -X mmHg
corresponds to pressure that is further from atmospheric pressure
(e.g., -80 mmHg is more than -60 mmHg).
[0081] The negative pressure range for some embodiments of the
present disclosure can be approximately -80 mmHg, or between about
-20 mmHg and -200 mmHg. Note that these pressures are relative to
normal ambient atmospheric pressure. Thus, -200 mmHg would be about
560 mmHg in practical terms. In some embodiments, the pressure
range can be between about -40 mmHg and -150 mmHg. Alternatively a
pressure range of up to-75 mmHg, up to -80 mmHg or over -80 mmHg
can be used. Also in other embodiments a pressure range of below
-75 mmHg can be used. Alternatively, a pressure range of over
approximately -100 mmHg, or even 150 mmHg, can be supplied by the
negative pressure apparatus. In some embodiments of wound closure
devices described here, increased wound contraction can lead to
increased tissue expansion in the surrounding wound tissue. This
effect may be increased by varying the force applied to the tissue,
for example by varying the negative pressure applied to the wound
over time, possibly in conjunction with increased tensile forces
applied to the wound via embodiments of the wound closure devices.
In some embodiments, negative pressure may be varied over time for
example using a sinusoidal wave, square wave, and/or in
synchronization with one or more patient physiological indices
(e.g., heartbeat). Canisterless NPWT (omitting a dedicated canister
to contain wound exudate) has also been considered using negative
pressure values in the same range as conventional NPWT. More
preferably -40 to -200 mmHg. More preferably -40 to -140 mmHg.
[0082] Embodiments address the problem of providing dressings in a
range of sizes and shapes to accommodate irregularly shaped wounds
and body topography, for example vein harvest wound dressings
accommodating variations in height and leg-length of individuals,
which is impractical both to the manufacturer and to the user.
Embodiments enhance adaptability of existing dressings, and of more
recently introduced multisite dressings such as trilobes and
quadrilobes. Embodiments enable a portion of a dressing to be
removed to create a main wound dressing of desired size or shape or
profile or articulation, and sealing exposed portion(s) thereof to
contain a negative pressure.
[0083] Exposed portion(s) as hereinbefore defined are the result of
removing a portion of the wound dressing, which may be by any
envisaged means, for example cutting the wound dressing or tearing
along a weakened line. Composite wound dressings may comprise a
border for affixing around a wound, about a central wound contact
portion. The dressing as hereinbefore defined may include a backing
layer and wound contact layer of similar footprint or surface area
to the transmission layer or other layers enclosed therebetween
(i.e. a borderless dressing) or of greater footprint or surface
area than the transmission layer enclosed therebetween (i.e a
bordered dressing). Exposed portion(s) as hereinbefore defined
result from removing a portion of the wound dressing as
hereinbefore defined directly enclosing the transmission layer, for
example by cutting into or through the backing layer and wound
contact layer and the transmission layer therebetween.
[0084] The portion(s) of the wound dressing may be removed to size
the main wound dressing portion for positioning over a wound as
hereinbefore defined, for example an incisional wound, an elongate
leg wound, an arcuate incisional wound and the like. Similarly the
portion(s) of the wound dressing may be removed to shape the main
wound dressing portion for positioning over a wound as hereinbefore
defined, such as a flap wound, over a protruding device such as a
fixation device or a protruding body part, to profile the main
wound dressing for positioning over a wound as hereinbefore
defined, for example on complex body topography, or to articulate
the main wound dressing for positioning over a wound as
hereinbefore defined for example on a flexing joint.
[0085] Preferably a dressing is skin compatible. Skin compatible as
used herein refers to the ability to apply or reapply a dressing
and in particular a backing layer or wound contact layer to skin
and remove from skin without trauma to the wearer, and without
causing substantial damage to the skin. Skin compatible materials
include adhesive or non-adhesive materials such as pressure
sensitive adhesive (PSA), typically acrylic, hydrocolloid, silicone
and silicone based materials and other materials as hereinbelow
recited. A particularly well known skin compatible material
comprises silicone or is silicone based, and skin compatible
materials are envisaged having properties corresponding to silicone
or silicone based material.
Composition and Method for Dispensing
[0086] The composition may be selected from a curing system and a
non-curing system. Ideally this is a material that will not flow
substantially from its application site but that during application
is either shear thinning or shape conformable when subject to load.
A curing system may be selected from a curable one or more parts
composition, for example silicone curing systems which may include
one, two or more part silicone systems and may include a range of
curing mechanisms, epoxy curing systems, cyanoacrylate curing
systems, polyurethane curing systems, polymeric systems
functionalised with silicone chain linking functional groups,
polymeric system functionalised with polyurethane curing functional
groups, drying system such as an elastomer rendered fluid by the
presence of a volatile solvent, spray on elastomers such as acrylic
in water or solvent base, UV or light curing systems.
[0087] A non-curing system may be selected from a one or more part
composition, for example a putty, a jelly such as petroleum jelly,
grease such as silicone grease, a gel such as a hydrogel, organogel
or xerogel, a paste, a colloidal system such as a hydrocolloid.
[0088] Preferably the composition dispensed to a location as
hereinbefore defined forms an elastomeric seal.
[0089] Curing time of a curable composition is not a limiting
feature. A curing composition usefully has curing time at
23.degree. C. in the range from 0.05 min to 24 hours, eg 0.5 to 20
min, more preferably from 0.5 to 18 min, more preferably from 0.5
to 16 min, most preferably 12 min, most preferably 0.5 to 5 min.
Cure time is manual kinetic as known in the art.
[0090] A number of methods are known in the art to monitor the cure
of liquid polymers and in particular RTV-2 silicones, these vary
from continuous monitoring across the full cure profile of the
material with instruments such as scanning vibrating needle
curemeters (B. G. Willoughby and K. W. Scott, Understanding cure
with the scanning vibrating needle curemeter (scanning VNC),
RTL/2844, Rapra Technology Limited, Shawbury) or differential
scanning calorimeters (L. M. Lopez, A. B. Cosgrove, J. P.
Hernandez-Ortiz, T. A. Osswald, Modeling the Vulcanization Reaction
of Silicone Rubber, Polym. Eng. Sci., 2007, 47, 675-683) through to
empirical single point determinations typically based on clear
physical changes, for example recording the time taken to reach the
gel point.
[0091] During the trials described in the examples it was found
that transfer of uncured sealant from the application site to other
surfaces was a clear disadvantage. For the purpose of defining an
unambiguous single point on the cure profile, cure time is taken to
mean manual kinetic cure time. Manual kinetic cure time is herein
defined as the cure time (at a specified temperature) at which
material is no longer transferred to skin (i.e. a fingertip) when
subject to a light, brief touch.
[0092] Due to the temperature dependence of the cure profile on
addition cure RTV silicones it is important that comparison between
any measurements is carried out at the same temperature and that
the temperature be reported. Guidance set out in Methods of Test
for Surgical Dressings in the British Pharmacopoeia (BP), 1993,
14.sup.th edition, A222, Appendix XX is that the temperature of a
regulated atmosphere is taken as 20.degree. C..+-.2.degree. C.
Within the silicone industry there are many instances where curing
parameters of addition cure RTV-2 silicones are reported at a
nominal temperature of 23.degree. C., this falls in line with
standard test methods for other temperature dependant properties
such as viscosity (when measuring viscosity DIN EN ISO 3219:1994
describes a preferred measurement temperature of 23.0.degree.
C..+-.0.2.degree. C.), examples of this include: Pot Life reported
by Wacker Silicones (at 23.degree. C. on Technical data sheet for
Silpuran.RTM. 2445 A/B, Version 1.3 & Technical data sheet for
Silpuran.RTM. 2450 A/B, Version 1.3, Wacker Chemie A G, Munchen);
Maximum Working Time reported by Bluestar Silicones (at 23.degree.
C. on The Silbione.RTM. Difference, Silicones for Healthcare
Applications, Bluestar Silicones France SAS, Lyon) and Pot Life
reported by Momentive (defined as the time for initial viscosity to
double at 23.degree. C. on Silicone Gels for Healthcare
Applications, 152-053-00E-GL, Momentive Performance Materials Inc.,
Columbus). When considering the temperature of a material applied
to skin, it should be noted that the temperature of skin is
nominally taken as 32.degree. C. In a clinical environment, when a
curing RTV-2 silicone is applied as a thin bead, layer or film in
intimate contact with the skin, it has been assumed that the
material will reach thermal equilibrium with the skin rapidly.
[0093] Within the literature other discrete points along the cure
profile are routinely used, of note are: pot life, this usually
indicates the maximum period of time after which the mixed
silicones may still be worked, poured, spread etc. Where flow is an
important requirement pot life is usually quoted as the time
required for the initial viscosity to double (Elastosil, Processing
RTV-2 silicone rubbers, 6020e/06.06, Wacker Chemie AG, Munchen) and
tack free time, this is an appropriate measure when considering a
rubber (by definition the material must not have any discernible
tack or grab once cured) and may be assessed in a similar way to
manual kinetic.
[0094] Preferably the composition has cure time as hereinbefore
defined at 23.degree. C. in the range from 0.5 min to 20 min, more
preferably from 0.5 to 18 min, more preferably from 0.5 to 16 min,
most preferably 12 min, most preferably 0.5 to 5 min. Cure time is
manual kinetic as hereinbefore defined.
[0095] Values at 32.degree. C. are particularly instructive in the
present application, preferably cure time at 32.degree. C. is in
the range 0.5 to 10 minutes, more preferably 0.5 to 8 minutes, most
preferably in the range 0.5 to 7 minutes.
Tack
[0096] Tack is hereinbelow measured as maximum force required to
separate a probe from cured composition. However for the purpose of
determining tack-free or low tack time, a touch and lift test was
performed at intervals with the finger, on controlled samples, and
tack free or low tack time determined as the time at which the
sample did not adhere to and lift with touch.
[0097] Preferably tack-free time is in the range from 0.5 to 25
minutes, more preferably from 0.5 to 22 minutes. Preferably the
composition has tack as hereinbeforedefined at a period in the
range from 0.5 minutes to 22 minutes after combining such as to not
adhere items such as paper or clothing which contact the
composition. Finger tack is a relatively subjective evaluation
which can be obtained by touching the surface of the dispensed
composition to determine the "stickyness" thereof. Descriptive
terms such as high H), low (L) and moderate (M) can then be
attributed as a preliminary measure.
[0098] Preferably a composition intended for external seal of the
exposed portion forms a substantially tack free seal in a period as
hereinbefore defined. Preferably a composition intended for
internal seal within the bridging portion forms a substantially
tack free to moderate tack seal.
Viscosity
[0099] Preferably as hereinbefore defined, compositions having low
viscosity in the range 11-14 Pa..sup.s-1 are of particular
advantage when dispensed internally.
[0100] A composition may be shear thinning, to assist application,
for example exhibiting change in viscosities with shear rate, for
example as follows:
TABLE-US-00001 Target shear rate (s.sup.-1) viscosity (eg range)
mPa s.sup.-1 1.0 250 (240-270) 2.50 80 (65-94) 5.00 55 (42-63)
10.00 40 (33-51) 25.00 20 (20-25) 50.00 15 (9-21) 100.00 10
(5-13)
[0101] Shear thinning compositions advantageously revert to their
rest viscosity and remain in place once the dispensing force or
applicator force is removed.
[0102] Alternatively a rapid onset of cure stabilises the
composition in position. Preferably composition penetrates within
the transmission layer and optional additional layers to a distance
of from 1 mm to 10 mm, for example substantially 5 mm. Penetration
should not exceed 25 mm.
Extensibility
[0103] A dressing as hereinbefore defined should approximate as
closely as possible to skin, to minimize discomfort and to maximize
the beneficial effects thereof. WO2009/156709 discloses the
properties of skin specifically in relation to extensibility, which
are to be approximate by a dressing. Preferably the composition
cures to a seal which approximates to the extensibility of the
dressing which it seals and/or the extensibility of the skin of the
wearer. Preferably the composition after curing as a sample with a
height of 1 mm has extensibility comparable to or greater than the
main dressing portion, bridging portion, trimming portion(s) or
component layers thereof up to a maximum corresponding to the
backing sheet. For example for the backing sheet the load required
to produce a 20% extension at a rate of extension of 300 mm per
minute is in the range of less than or equal to 1.4 kgf per cm
width (kgfcm.sup.-1), preferably in the range 0.001 to 1.4 kgf
cm.sup.-1 expressed preferably as 0.001 to 14.0 kgf cm.sup.-2 to
produce 20% extension, more preferably in the range 0.001 to 5.0
kgf cm.sup.-2.
[0104] The extensibility of a typical spacer layer is
approximately: 0.08 kgfcm.sup.-1 (Direction A); 0.07 kgfcm.sup.-1
(Direction B)
[0105] The extensibility of a typical superabsorber layer (Laminate
EU33 top film, superabsorbent airlaid (Chemposite 11C/450 airlaid
superabsorbent pad, spacer layer Baltex 7970 and perforated Si
wound contact layer is approximately 0.59 kgfcm.sup.-1 (Direction
A); 0.78 kgfcm.sup.-1 (Direction A).
[0106] Preferably extensibility of seal as hereinbefore defined is
0.04 to 3.00, more preferably 1.00 to 2.50.
Permanent Set
[0107] Permanent set for the cured seal enclosed within the layers
may be substantially 0. In the case of a seal enclosed within the
layers then permanent set is preferably in the range comparable to
Allevyn dressings.
Tensile Strength
[0108] In the case of a seal enclosed within the layers the
composition benefits from the support of the dressing and tensile
strength values may be widely variable. In the case of a seal
enclosed within the layers then tensile strength is preferably in
the range comparable to Allevyn dressings.
Elongation at Break
[0109] In the case of a seal enclosed within the layers the
composition benefits from the support of the dressing and
elongation at break values may be widely variable. In the case of a
seal enclosed within the layers then elongation at break is
preferably in the range comparable to the spacer materials
typically present in dressings. Spacer elongation at break is 115%.
Preferably elongation at break is in the range 5-15%.
Compressibility
[0110] Preferably the composition forms a seal having equal or
greater compressibility than the bridging layer. Further detail is
given herein in relation to preferred compressibility of the
bridging layer and bridging layer materials when subject to
negative pressure. Preferably a seal does not protrude above the
exposed portion which is seals, preferably a protruding seal is
compressible. Compressibility is measured according to penetrometry
ASTM 82137, more preferably is in the range 20-500/10 mm.
[0111] It will be clear that viscosity for each of Parts A and B is
for the as-provided components, prior to mixing. Suitably the
components mix to a dispensible viscosity.
[0112] Preferably the cured composition has elongation at break as
hereinbelow defined, greater than or equal to 50%.
[0113] Preferably the cured composition has tensile strength, as
hereinbelow defined, greater than or equal to 5 kgfcm.sup.-2
Preferably for the cured composition permanent set is in the range
20% to 0%.
[0114] Preferably the composition is a Silpuran composition as
hereinbelow recited, more preferably is Silpuran 2400.TM., or a
functional analogue thereof, optionally incorporating viscosity
and/or cure time modifier providing increased viscosity and reduced
cure time. Preferably the composition has translucent appearance
after curing. Preferably the composition is dispensed within the
transmission layer by the first embodiment method disclosed herein
(FIG. C1).
[0115] In a first embodiment the composition is dispensing into a
location as hereinbefore defined, the location being substantially
internal to or received within the transmission layer at the
exposed portion as hereinbefore defined. In this embodiment,
composition is required to be dispensed from an outlet of a
dispensing device such as a static mixer, said outlet being capable
of being received within the transmission layer at the exposed
portion as hereinbefore defined. Suitably a dispenser comprises a
syringe or static mixer comprising a nozzle having an outlet.
Preferably the nozzle is capable of being received within the
transmission layer at the exposed portion in manner that the
location at which composition is to be dispensed is a short
distance within the exposed portion, for example is up to 25 mm
distant from the exposed portion, more preferably from 2 mm to 20
mm, more preferably from 3 mm to 18 mm, for example in the range
from 5 mm to 12 mm. Composition may be dispensed via the exposed
portion face or via the backing layer or sheet, for example by
injection through the backing layer or sheet. Dispensing may be
before or after trimming a dressing. Dispensing by this means may
be by puncturing the film either singly or in multiple places as
described above. Preferably the film is punctured with use of one
or more resiliently deformable needles, for example a plastic
needle or with use of one or more limited penetration depth
needles. Such needle minimizes risk of skin puncture. Alternatively
the injection could take place prior to dressing placement and
removal of the dressing handle, thus confining the sealant to
between the backing layer or sheet and the handle. Dispensing may
be prior to trimming the dressing alongside or through the cured
sealant to leave a sealed edge. Composition may alternatively be
dispensed to intact skin and exposed portion of the dressing
located thereover. Composition so dispensed flows into or is drawn
into the dressing to the transmission layer thereby sealing.
[0116] Composition so dispensed is dispensed to a location deeper
into the exposed portion distanced from its face. Composition is
dispensed as a band returning back to the face of the exposed
portion as the dispensing device is withdrawn. A seal so generated
is more secure, with more comprehensive blocking of passageways
within the exposed portion of the transmission layer. Such a seal
has a lesser likelihood of presenting leaks when negative pressure
is applied. A suitable nozzle for a dispensing device includes low
aperture nozzles, needles and the like. Nozzles may be formed from
plastic. Such nozzles are disposable and present no hazard, being
non-perforating to human skin. Such nozzles are currently available
for use with pipette tips.
[0117] Composition may be dispensed via multiple point injection at
intervals along the exposed face, for example through the spaces
between the spacer layer struts. Composition may flow to some
extent on initial application, either or both laterally to the
direction of dispensing and advancing and receding, flow becoming
less as composition hardens or cures. This may aid in providing a
continuous lateral seal, whereby dispensing intervals along the
face of exposed portion may be increased. Nozzle insertion distance
within the exposed portion may be selected to confine the seal
spaced a short distance in from the face of the exposed portion, or
to allow some spill of composition out of the exposed portion and
onto surrounding surfaces such as a preparation plate or skin.
Advantages of this embodiment include minimizing the amount of
composition required to be dispensed. This in turn allows use of a
lower capacity dispensing device, for example a 5 ml or 10 ml or 15
ml or 25 ml syringe or static mixer. The back pressure encountered
on dispensing from a static mixer increases with the mixer volume,
which in turn leads to a decrease in the viscosity which the static
mixer is able to dispense. It is generally advantageous to this
embodiment to deliver composition at as high a viscosity as
possible to ensure that composition is confined within the exposed
portion. A further element in the total back pressure or resistance
encountered on dispensing composition is the nozzle aperture of
static mixer. For this embodiment, it is desired to dispense
composition from a small aperture nozzle, and this adds to the back
pressure. The advantage that this embodiment delivers of enabling a
relatively small volume syringe or mixer to be employed, allows
greater freedom to operate a small aperture nozzle.
[0118] Finally we have found that a seal generated by dispensing
composition internally to the exposed portion according to this
embodiment, is highly effective. The dressing should be trimmed, as
hereinbefore described, such that the exposed portion overlies
intact skin about a wound, and does not overly the wound itself. In
the case of a dressing having an adhesive or tacky wound contact
layer, such as a silicone contact layer as hereinbefore described,
the wound contact layer adheres to the skin about the wound and
seals the dressing to skin about the exposed portion and the
dispensed seal. Preferably the exposed portion is bordered by a
border region at the 2 extremities thereof, for example a border of
backing sheet or layer as hereinbefore defined, preferably having
depth in the range 5 mm to 25 mm, more preferably 7 mm to 25 mm,
for example 14 mm to 25 mm. The wound contact layer is perforated
or otherwise porous to allow transmission of fluids to and from the
wound bed, and this may permit flow of composition onto skin
directly proximal to the internal seal. This may beneficially
enhance the seal between the wound contact layer and skin. In the
event that flow of composition to skin directly proximal to the
internal seal is not desired, composition suitably has a
sufficiently high viscosity to restrict flow, alternatively the
wound contact layer may be non-porous or non-permeable in the
region proximal to an envisaged exposed portion, for example at a
bridging portion or trimmable portion as hereinbefore defined.
Composition may be dispensed to a location as hereinbefore defined
in a dressing having no obscuring layer, or having window(s) in
obscuring layer at bridging portions or trimmable portion(s). This
allows visual control of nozzle insertion distance within the
exposed portion of composition, of volume dispensed, and/or of
lateral flow enabling a suitable dispensing interval across the
face of exposed portion to be determined. In the case that no
obscuring layer is present it is preferred that the composition
incorporates ADL as hereinbefore defined as transmission layer,
rather than spacer layer which may pose a risk of penetrating the
backing sheet.
[0119] In this embodiment preferably the dressing does rot comprise
absorbent layer such as ADL in the bridging portion or at the
trimmable portion.
[0120] In a further embodiment of the composition for dispensing
into a location as hereinbefore defined, the location comprises the
backing layer or backing sheet adjacent the exposed portion,
whereby composition flows across and covers the exposed portion. In
some cases composition flows a short distance into or is drawn a
short distance within the exposed portion. It may be desired to
dispense or smooth composition at the perimeters or extremities of
the exposed portion for example adjoining a border region, and for
example directed slightly back along the perimeter or extremity.
This has the advantage of advancing composition a short distance at
the perimeter of the exposed portion, ensuring a total seal and
also securing the seal in place. As composition hardens or cures,
the viscosity typically increases and flow ceases whereby
composition is retained at or in the dispensing location and forms
an effective seal.
[0121] This further embodiment places performance requirements on
the composition and the resulting seal, additional to those of the
first embodiment of sealing and mode of dispensing. Specifically
composition requires a continuous film to be dispensed and formed
across the surface of the backing layer or sheet bridging onto the
exposed portion of any additional layers and the exposed portion of
the transmission layer and bridging onto the skin surface.
Therefore composition must be sufficiently viscous and/or cohesive
to form an intact film. Such film may be thin or may be of
appreciable depth and/or thickness of for example from the order of
depth and/or thickness of the backing sheet to the order of depth
and/or thickness of the dressing or of the component layers at the
exposed portion thereof, for example 1 mm to 5 mm. Should such film
rupture or fail prior to setting or curing of composition then the
seal will fail. After setting or curing of an intact film, the
exposed nature of the seal and its presentation as a film place
additional requirements of robustness, both to external influences
and also, to its ability to retain integrity across interfaces
between adjacent layers. These requirements are likely to be
greater in the case of a thin film. Preferably therefore a seal
according to this further embodiment is characterized by properties
of tensile strength, permanent set, and elongation at break,
optionally also extensibility, in ranges as hereinbefore defined.
In contrast a seal generated according to the first embodiment, as
hereinabove, is supported in large part by the fabric of the
dressing enclosing the seal, whereby requirements of tensile
strength, permanent set, elongation at break, are significantly
lower, also being enclosed within the lower extensibility dressing,
the requirement for extensibility is significantly lower than for
the further embodiment as herein.
[0122] A seal according to this embodiment may be effective from
the backing layer surface across the exposed portion.
[0123] As will be apparent, a seal across the exposed portion alone
is susceptible to failure at the interface of the backing sheet and
exposed portion and any intervening layers.
[0124] This further embodiment is likely to be more effective when
adopted in relation to a dressing comprising no additional layers
as hereinbefore defined, thereby better resisting strains
introduced by separation at the interface of additional layer(s)
and transmission layer. Additional layer(s) if present may
beneficially be secured at their interfaces with each other and
with transmission layer, by needling, stitching and other means as
known in the art.
[0125] The further embodiment moreover requires that a seal have
low profile and/or have compressibility greater than or equal to
the surrounding dressing. This is of advantage in minimizing
discomfort to the wearer imposed by a protruding ridge at the
exposed portion of the dressing.
[0126] In one embodiment the composition may comprise any polymers
that follow a hydrosilylation reaction. One polymer (i) preferably
contains alkenyl groups, the other (ii) preferably contains Si--H
moieties. The group of siloxane polymers is based on a structure
comprising alternate silicon and oxygen atoms with various organic
moieties attached to the silicon. Curing can be defined as a
treatment that decreases the flow of an elastomer. This change is
generally brought about by linking reactions between polymer
molecules. Where the silicon hydride (Si--H) moiety is part of a
polysiloxane, it is possible for the alkenyl group to either be
part of a siloxane polymer or otherwise part of a non-siloxane
polymer. The position of the alkenyl functional group is not
critical and it may be either at the molecular chain terminals or
in non-terminal positions along the molecular chain.
[0127] A curing system is preferably apportioned between at least
one Part A and at least one Part B and comprises: one or more
alkenyl-group containing polymers (i) having at least one alkenyl
group or moiety per molecule, one or more SiH-containing polymers
(ii) having at least one Si--H unit per molecule; and a catalyst
(iii) for curing by addition of alkenyl-containing polymer (i) to
SiH-containing polymer (ii).
[0128] A "unit" as herein referred represents a group or moiety or
part thereof. A "moiety" as herein referred is a group of atoms
having further atoms disposed on two or more sides thereabout, ie
having two or more valencies unspecified.
[0129] A "group" as herein referred represents a group of atoms
having further atoms disposed on one side thereof, ie having one
valency unspecified. Si--H units herein have the same meaning as
SiH units
[0130] Polymers (i) and (ii) as hereinbefore defined are
fluid-phase polymers incorporating reactive groups which cross-link
in presence of catalyst to form a copolymer more preferably a cured
elastomer. Suitably Part A comprises catalyst together with polymer
(i), and Part B comprises polymer (ii) optionally together with any
remaining polymer (i). Suitably polymers, catalyst and optional
further components are apportioned in manner to balance volumes and
viscosities of both Parts. Preferably polymer (i) is an
alkenylsiloxane-containing polymer.
[0131] Preferably the Parts are combined and intimately admixed
prior to or during to dispensing.
[0132] Suitably the components and Parts mix to a dispensible
viscosity.
[0133] Polymers (i) and/or (ii) are commercially available or may
be obtained by known techniques. Suitably polymers (i) and/or (ii)
are independently selected from known and novel fluid phase
homopolymeric, and copolymeric polymers, and their entangled
systems and mixtures thereof. The compositions, in turn, cure to
form copolymers, and may also include their entangled systems and
mixtures with other non-reactive polymers if present in the
composition.
[0134] Copolymeric polymers include all hybrids derived from two or
more monomeric species, including alternating, periodic,
statistical, random, block, linear, branched, star, graft and
pendant copolymers. Entangled systems include interpenetrating
networks (IPNs) and semi-interpenetrating networks (SIPNs). It is
also the case that these polymers can incorporate both organic and
inorganic moieties.
[0135] Preferably polymers (i) and (ii) are selected from
silicones, including siloxanes and modified siloxanes,
polyurethanes (PU) including polyester and polyether urethanes,
elastomeric polyether polyesters, polyglycolic acid, polyacetates
such as ethyl vinyl acetate, polyacrylate, polyacid derivatives of
polysaccharides, such as carboxyalkylcellulose,
carboxyalkylchitosan and copolymers thereof, and their hybrids
including copolymers, entangled systems and mixtures thereof.
[0136] The composition may make use of an addition cure reaction
between organohydrogensiloxane units and organoalkenylsiloxane
units. These units may be incorporated into a wide range of
polymeric, copolymeric, entangled and mixed polymers as
hereinbefore defined. Preferred siloxane polymers (i) and (ii)
therefore include these respective units and are more preferably
polyorganosiloxanes. Polymer (i) is preferably a
polydiorganosiloxane polymer comprising alkenyl-containing units,
more preferably is a polydiorganoalkenylsiloxane polymer.
Preferably polymer (ii) is a polydiorganosiloxane polymer
comprising SiH units, more preferably is a
polydiorganohydrogensiloxane polymer.
[0137] Examples of hybrid organic-inorganic polymeric systems that
have used both siloxane and organic units include: acrylate
functionalized siloxane copolymers, which have found use in contact
lenses (U.S. Pat. No. 3,808,178); hybrid grafts where organic
polymers are grafted onto a polysiloxane chain or where siloxanes
are grafted onto organic polymers, for example in silane graft
technology for cross linkable HDPE (U.S. Pat. No. 3,646,155) where
hybrid grafts have been used to allow the cross linking of organic
polymers through siloxane bond formation; hybrid block copolymers
for example silicone-polycarbonate block copolymers (U.S. Pat. No.
3,274,155); and copolymers of hybrids of silicone and ethylene
copolymers, cross-linked with vinyl-containing silicone copolymers
which have found use in coating textiles (US 2005/0100692);
[0138] IPNs represent a special class of hybrid polymeric systems,
these systems use a combination of mechanical entanglement and
crosslinking in which one polymer is cured about another; these
include thermoplastics entangled with platinum catalyzed addition
cure silicones such as silicone-urethane IPNs and semi-IPNs
including silicone-urethane and silicone-polyamide systems which
are of general application or have found specific use in coating
textiles (U.S. Pat. No. 4,714,739, U.S. Pat. No. 7,543,843);
hydrophilic components immobilised in a silicone polymer (U.S. Pat.
No. 5,397,848) which have found use as contact lens material; and
silicone polymer cured about a non-reactive polymer of comparable
adhesion, which have found use in coating textiles (U.S. Pat. No.
7,132,170).
[0139] Polymers may also be selected from modified silicones (MS)
which find use as adhesives in catheter tubing and the like.
[0140] Preferred compositions comprise a polydiorganosiloxane
polymer (i) and/or (ii) and/or their respective combinations with
the aforementioned polymers. A composition in which polymers
comprise or consist essentially of polydiorganosiloxane polymers
(i) and (ii) has particular advantages, for example in applications
where low toxicity is an advantage, preferably in medical or dental
applications or in non-medical or non-dental applications requiring
low toxicity or favorable biocompatibility.
[0141] Alternatively or additionally polymers (i) and (ii) are as
commercially available (Cavi-Care.TM. A/B, and the like) or
variants thereof, optimised for viscosity and curing to give a
fluid-tight exposed surface (hereinafter skin-formation or
"skinning") as hereinbefore defined.
[0142] Polymer (i) and (ii) may comprise respective
alkenyl-containing units and organohydrogensiloxane units situated
along the length of polymer chains, and/or as polymer chain
end-capping units or a combination thereof. Polymer (i) in-chain
and end-capping alkenyl units preferably comprise alkenyl group or
moiety R.sup.Alk selected from C.sub.2-20 alkenyl optionally
substituted or including one or more aryl groups or moieties.
R.sup.Alk may comprise terminal or non terminal unsaturation, and
may be of the formula i-I:
--R.sup.Alk1--CR.sup.Alk1.dbd.CR.sup.Alk2.sub.2 (i-I)
in which the groups R.sup.Ak1 and R.sup.Alk2 are independently
selected from H, C.sub.1-20 alkyl and C.sub.5-20 aryl groups and
combinations thereof and a moiety R.sup.Alk1 is selected from a
single bond, C.sub.1-20 alkyl and C.sub.5-20 aryl groups and
combinations thereof. One of R.sup.Alk2 may be a moiety linking to
polymer chain. More preferably each R.sup.Alk is independently
selected from vinyl, allyl, propenyl, and from terminally and
non-terminally unsaturated butenyl, pentenyl, hexenyl, heptenyl,
octenyl, nonenyl and decenyl groups, most preferably selected from
vinyl and hexenyl groups.
[0143] Preferably polymer (i) comprises a polydiorganosiloxane
polymer or copolymer comprising alkenyl-containing units of the
formula (i-II):
.dbd.Si--R.sup.Alk, (i-II)
more particularly of the formula (i-Ill) and/or (i-IV):
--O--Si R.sup.1R.sup.Alk--O-- (i-III)
--O--Si R.sup.1.sub.2R.sup.Alk (i-IV)
wherein R.sup.Alk is as hereinbefore defined and one or more groups
R.sup.1 are organo groups suitably independently selected from
alkyl and aryl groups, more preferably C.sub.1-20 alkyl and
C.sub.5-20 aryl groups and combinations thereof, for example from
methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl
and/or decyl groups and moieties.
[0144] More particularly polymer (i) is selected from the formula
i-V and i-VI:
P.sup.i--O--Si R.sup.1R.sup.Alk--O--P.sup.i i-V:
P--O--Si R.sup.1.sub.2R.sup.Alk i-VI
wherein P.sup.i denotes the remainder of the polymer chain which
may incorporate same or different units, and R.sup.1 is as
hereinbefore defined.
[0145] Polymer (i) may also comprise a polyorganosiloxane
exhibiting, per molecule, at least two C.sub.2-C.sub.6 alkenyl
groups bonded to the silicon and having, for example, a viscosity
of between 10 and 300 000 mPas, that is to say 0.01 to 300 Pas,
such that when combined in Part A with further Part A components
and optionally additionally in Part B with further Part B
components, Part A, and Part B as appropriate, is (are) of
viscosity in a range as hereinbefore defined, which can in
particular be formed of at least two siloxyl units of formula:
Y d R e SiO ( 4 - d - e ) 2 ( III ) ##EQU00001##
in which: [0146] Y is a C.sub.2-C.sub.6 alkenyl such as vinyl,
allyl or hexenyl groups, preferably vinyl, [0147] R is a monovalent
hydrocarbon group with no unfavorable effect on the activity of the
catalyst which is generally chosen from alkyl groups having from 1
to 8 carbon atoms inclusive, such as the methyl, ethyl, propyl and
3,3,3-trifluoropropyl groups, cycloalkyl groups, such as the
cyclohexyl, cycloheptyl and cyclooctyl groups, and aryl groups,
such as xylyl, tolyl and phenyl, [0148] d is 1 or 2, e is 0, 1 or 2
and d+e=1, 2 or 3, [0149] optionally all the other units being
units of average formula:
[0149] R f SiO 4 - f 2 ( IV ) ##EQU00002## [0150] in which R has
the same meaning as above and f=0, 1, 2 or 3.
[0151] Examples of polymer (i) are, for example,
dimethylpolysiloxanes comprising dimethylvinylsilyl ends,
(methylvinyl)(dimethyl)polysiloxane copolymers comprising
trimethylsilyl ends or (methylvinyl)(dimethyl)polysiloxane
copolymers comprising dimethylvinylsilyl ends.
[0152] A convention accepted in the art for denoting the units of
silicones according to the number of oxygen atoms bonded to the
silicon is used here. This convention uses the letters M, D, T and
Q (abbreviations for "mono", "di", "tri" and "quatro") to denote
this number of oxygen atoms. This nomenclature of silicones is
described, for example, in the work by Walter Noll, "Chemistry and
Technology of Silicones", Academic Press, 1968, 2nd edition, on
pages 1 to 9.
[0153] Polymer (i) may also be a silicone resin bearing at least
two alkenyl, preferably vinyl groups. Such silicone resin
comprising at least two different siloxane units chosen from those
of M siloxane unit of formula R.sub.3SiO.sub.1/2, D siloxane unit
of formula R.sub.2SiO.sub.2/2, T siloxane unit of formula
RSiO.sub.3/2 and Q siloxane unit of formula SIO.sub.4/2,
[0154] wherein R denotes a monovalent hydrocarbon group, with the
conditions that at least one of these siloxane units being a T or Q
siloxane unit and that at least two of the M, D and T siloxane
units comprises an alkenyl group.
[0155] The silicone resin could be selected from the group
consisting of: [0156] an organopolysiloxane resin of formula
MT.sup.ViQ consisting essentially of: [0157] (a) trivalent siloxane
units T.sup.Vi of the formula R'SiO.sub.3/2; [0158] (b) monovalent
siloxane units M of the formula R.sub.3SiO.sub.1/2, and [0159] (c)
tetravalent siloxane units Q of the formula SiO.sub.4/2 [0160] an
organopolysiloxane resin of formula MD.sup.ViQ consisting
essentially of: [0161] (a) divalent siloxane units D.sup.Vi of the
formula RR'SiO.sub.2/2; [0162] (b) monovalent siloxane units M of
the formula R.sub.3SIO.sub.1/2, and [0163] (c) tetravalent siloxane
units Q of the formula SiO.sub.4/2 [0164] an organopolysiloxane
resin of formula MDD.sup.ViQ consisting essentially of: [0165] (a)
divalent siloxane units D.sup.Vi of the formula RR'SiO.sub.2/2;
[0166] (b) divalent siloxane units D of the formula
R.sub.2SiO.sub.2/2 [0167] (b) monovalent siloxane units M of the
formula R.sub.3SiO.sub.1/2, and [0168] (c) tetravalent siloxane
units Q of the formula SiO.sub.4/2 [0169] an organopolysiloxane
resin of formula M.sup.ViQ consisting essentially of: [0170] (a)
monovalent siloxane units M.sup.Vi of the formula
R'R.sub.2SiO.sub.1/2; and [0171] (b) tetravalent siloxane units Q
of the formula SiO.sub.4/2, and [0172] an organopolysiloxane resin
of formula M.sup.ViT.sup.ViQ consisting essentially of: [0173] (a)
monovalent siloxane units M.sup.Vi of the formula
R'R.sub.2SiO.sub.1/2; [0174] (b) trivalent siloxane units T.sup.Vi
of the formula R'SiO.sub.3/2, and [0175] (c) tetravalent siloxane
units Q of the formula SiO.sub.4/2 [0176] wherein R denotes a
monovalent hydrocarbon group such as methyl and R' denotes a vinyl
group:
[0177] Such resins are well-known branched organopolysiloxane
oligomers or polymers which are commercially available. They are
provided in the form of solutions, preferably siloxane
solutions.
[0178] Polymer (ii) in-chain and end-capping
polyorganohydrogensiloxane units are preferably selected from the
formula ii-I and ii-II:
--O--Si R.sup.2H--O-- ii-I
--O--Si R.sup.2.sub.2H, ii-II
more preferably polymer (ii) is selected from formula ii-III and
ii-IV:
P.sup.ii--O--Si R.sup.2H--O--P.sup.ii ii-III
P.sup.ii--O--Si R.sup.2.sub.2H ii-IV
wherein P.sup.ii denotes the remainder of the polymer chain which
may incorporate same or different units and one or more groups
R.sup.2 are organo groups suitably independently selected from
C.sub.1-20 alkyl, C.sub.5-20 aryl and combinations thereof, for
example from methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl,
octyl, nonyl and/or decyl groups.
[0179] Polymer (ii) preferably comprises a
polyorganohydrogensiloxane-polydiorganosiloxane copolymer,
incorporating one or more units ii-I and/or ii-II:
--O--Si R.sup.2H--O-- ii-I
--O--Si R.sup.2.sub.2H ii-II
and one or more units ii-V and/or ii-VI:
--O--Si R.sup.2.sub.2--O-- ii-V
--O--Si R.sup.2.sub.3 ii-VI
wherein R.sup.2 is as hereinbefore defined, more preferably
copolymer incorporating polyorganohydrogensiloxane end-capping
units, i.e polymer chains terminate with the group or moiety
ii-VII:
.ident.Si--H, ii-VII
more particularly with the unit of formula ii-II:
--O--Si R.sup.2.sub.2H ii-II
as hereinbefore defined. Most preferably polymer (ii) comprises
methylhydrogensiloxane-dimethylsiloxane copolymers.
[0180] Polymer (ii) may also comprises a polyorganosiloxane,
exhibiting, per molecule, at least two hydrogen atoms bonded to the
silicon and preferably at least three .ident.SiH units and having,
for example, a viscosity of between 1 and 5000 mPas, that is to say
between 0.001 and 5 Pas, up to 300 Pas as hereinbefore defined,
such that when combined in Part B with further Part B components,
Part B is of viscosity in a range as hereinbefore defined, which
can in particular be formed of siloxyl units of formula:
H g X i SiO 4 - g - i 2 ( V ) ##EQU00003##
in which: [0181] X is a monovalent hydrocarbon group with no
unfavorable effect on the activity of the catalyst which is
generally chosen from alkyl groups having from 1 to 8 carbon atoms
inclusive, such as the methyl, ethyl, propyl and
3,3,3-trifluoropropyl groups, cycloalkyl groups, such as the
cyclohexyl, cycloheptyl and cyclooctyl groups, and aryl groups,
such as xylyl, tolyl and phenyl, [0182] g=1 or 2, preferably =1,
i=0, 1 or 2 and g+i=1, 2 or 3, optionally all the other units being
units of average formula:
[0182] X j SiO 4 - j 2 ( VI ) ##EQU00004## [0183] in which X has
the same meaning as above and j=0, 1, 2 or 3.
[0184] Examples of polymer (ii) are polymethylhydrosiloxanes or
methylhydrodimethylsiloxane copolymers.
[0185] In the case that polymers include other units additional to
iIII, iIV, iiI and iiII for example, these are suitably not
reactive with the respective polymer at ambient temperature or
under sterilising conditions.
[0186] Suitably the ratio of silicon-bonded hydrogen atoms provided
by (ii) to silicon-bonded alkenyl moieties provided by (i) is at
least 0.5:1, preferably 1:1,
[0187] Preferably embodiments of the curable composition follow the
catalysed addition cure reaction according to the following
scheme:
P.sup.i--R.sup.Alk1--CR.sup.Alk1.dbd.CR.sup.Alk2.sub.2+P.sup.ii--SiHR.su-
p.2R.sup.2/P.fwdarw..sup.[catalyst]
P.sup.i--R.sup.Alk1--CHR.sup.Alk1CR.sup.Alk2.sub.2--SiR.sup.2R.sup.2/PP.-
sup.ii
more preferably:
##STR00001##
wherein integers are as hereinbefore defined and R.sup.1/P is
selected from P.sup.i and R.sup.1 as hereinbefore defined and
R.sup.2/P is selected from P.sup.ii and R.sup.2 as hereinbefore
defined.
[0188] The polymers (i) and (ii) and catalyst (iii) may be
apportioned in at least one Part A and at least one Part B in
manner to provide respective Parts A and B which in isolation are
not reactive at ambient temperature, nor under sterilisation
conditions, such as heat or radiation. Apportioning may also be
determined according to volume and viscosity.
[0189] Polymers (i) and (ii) and catalyst (iii) may be apportioned
in at least one Part A and at least one Part B in manner such that
polymer (ii) is absent from Part A and polymer (i) is absent from
Part B or Part B incorporates a trace amount of polymer (i)
represented as molar ratio (Si--H unit or moiety)/(alkenyl unit or
moiety) of greater than or equal to 2000. Such composition may be
sterilised at effective gamma or radiation dose for example as
disclosed in WO2012/069794, the contents of which are incorporated
herein by reference.
[0190] The at least one Part A and at least one Part B may be of
substantially equal volume and viscosity or of different volume
and/or viscosity. Part A or Part B may incorporate a suitable
viscosity moderator or diluent, in amount to increase or reduce
volume and/or viscosity. By this means Part A and Part B having
different volume and viscosity may be volume and viscosity matched
for improved ease and intimacy of mixing and dispensing. A suitable
diluent is for example a silicone oil which is available in any
desired viscosity for thickening or thinning effect. Alternatively
or additionally at least one Part A and at least one Part B are
sealed in respective receptacles or on respective supports which
are thermally stable at an elevated temperature of 121.degree. C.
or more for a period of up to 28 hours, for example as disclosed in
WO2012/069793, the contents of which are incorporated herein by
reference.
[0191] The composition may thereby be rendered terminally sterile
by being sterilised in its primary packaging and this property may
be characterised by a Sterility Assurance Level (SAL). The SAL is
defined in ISO 11139:2006 as the probability of a single viable
microorganism occurring on an item after sterilization. The term
SAL takes a quantitative value, in the format of 10.sup.-n, where
typically n=3, 4, 5 or 6, preferably SAL=10.sup.-3 or
10.sup.-6.
[0192] A catalyst as hereinbefore defined may be any catalyst which
is effective in catalysing the addition curing reaction as
hereinbefore defined, more preferably as hereinabove illustrated.
Suitable catalysts are selected from any known form of platinum,
rhodium, palladium, nickel and like addition curing hydrosilylation
catalysts, for example as disclosed in U.S. Pat. No. 5,153,231, US
2006/0217016, U.S. Pat. No. 3,928,629 and U.S. Pat. No. 4,529,553
the contents of which are incorporated herein by reference.
[0193] A platinum catalyst may be selected from platinum black
platinum as deposited on carriers including silica such as silica
gel or carbon such as powdered charcoal, platinic chloride or
chloroplatinic acid and alcohol solutions thereof, salts of
platinic and chloroplatinic acids and platinum complexes such as
platinum/olefin, platinum/alkenylsiloxane, platinum/beta-diketone,
platinum/phosphine and the like. Chloroplatinic acid may be the
hexahydrate or anhydrous form. A platinum complex may be prepared
from chloroplatinic acid and its hexahydrate, or from platinous
chloride, platinum dichloride, platinum tetrachloride and their
neutralised complexes with divinyltetramethyldisiloxane, optionally
diluted with dimethylvinylsiloxy endcapped
polydimethylsiloxane.
[0194] A palladium catalyst may be selected from palladium on
carbon, palladium chloride and the like.
[0195] A rhodium catalyst may be selected from rhodium chloride and
one or more complexes of rhodium having the general formula iii-I
or iii-II:
RhX.sub.3(SR.sub.2).sub.3 (iii-I)
Rh.sub.2(CO).sub.4X.sub.2 (iii-II)
wherein each X represents a halogen atom and each R represents an
alkyl or aryl radical or combination thereof having from 1 to 8
inclusive carbon atoms or the R'.sub.3SiQ group in which Q
represents a divalent aliphatic hydrocarbon radical having from 1
to 6 inclusive carbon atoms and R' represents an alkyl or aryl
radical or combination thereof having from 1 to 8 inclusive carbon
atoms or a (CH.sub.3).sub.3Si-- group, not more than one R' per
molecule being (CH.sub.3).sub.3Si--. For example rhodium
chloride/di(n-butyl)sulfide complex and the like.
[0196] A nickel catalyst is preferably a zero valent nickel
selected from M.sub.2Ni.sup.(0) such as
bis(1,5-cyclo-octadienyl)nickel (Ni(COD).sub.2) and from
MNi.sup.(0)G wherein M is a bidentate alkene cyclic hydrocarbon
ring of C.sub.8-12 and G is selected from monodentate and bidentate
phosphorous groups having hydrogen atoms, substituted or
unsubstituted hydrocarbon radicals or mixtures thereof bonded to
the phosphorous atoms of the phosphorous groups.
[0197] The composition may include a catalyst inhibitor. Suitable
inhibitors are known in the art. For example a catalyst inhibitor
may be selected from a polymethylvinylsiloxane cyclic compound and
an acetylenic alcohol, such as methyl butynol for example as in
Cavi-Care or disclosed in U.S. Pat. No. 5,153,231, the contents of
which are incorporated herein by reference.
[0198] Preferably the composition comprises an addition-reaction
retardant or a crosslinking inhibitor chosen, for example, from the
following compounds: [0199] polyorganosiloxanes substituted with at
least one alkenyl that may optionally be in cyclic form,
tetramethylvinyltetrasiloxane being particularly preferred, [0200]
organic phosphines and phosphites, [0201] unsaturated amides,
[0202] alkyl maleates, and [0203] acetylenic alcohols.
[0204] These acetylenic alcohols (see FR-A-1 528 464 and FR-A-2 372
874), which are among the preferred thermal blockers of the
hydrosilylation reaction, have the formula:
(R')(R'')C(OH)--C.ident.CH
in which formula [0205] R' is a linear or branched alkyl radical,
or a phenyl radical; [0206] R'' is H or a linear or branched alkyl
radical, or a phenyl radical; the radicals R', R'' and the carbon
atom alpha to the triple bond possibly forming a ring; and [0207]
the total number of carbon atoms contained in R' and R'' being at
least 5 and preferably from 9 to 20. Examples that may be mentioned
include: [0208] 1-ethynyl-1-cyclohexanol; [0209]
3-methyl-1-dodecyn-3-ol; [0210] 3,7,11-trimethyl-1-dodecyn-3-ol;
[0211] 1,1-diphenyl-2-propyn-1-ol; [0212]
3-ethyl-6-ethyl-1-nonyn-3-ol; [0213] 2-methyl-3-butyn-2-ol; [0214]
3-methyl-1-pentadecyn-3-ol.
[0215] These .alpha.-acetylenic alcohols are commercial products.
Such a retardant is present in a maximum proportion of 3000 ppm
relative to the total weight of the polyorganosiloxanes in the
silicone composition. Methyl butynol could be chosen as in
Cavi-Care.
[0216] The composition may be non-foamable or may be foamable,
comprising (iv) an expansion or "blowing" agent, selected from any
agent which evolves gas or vapour as part of or during the curing
reaction, for example selected from H-donors, OH-containing agents,
H-bonding agents such as: [0217] alcohols including methanol,
ethanol, n-propanol, isopropanol, n-butanol, 2-butanol,
tert-butanol, n-hexanol, n-octanol and benzyl alcohol. n-Propanol,
n-butanol, n-hexanol and n-octanol are particularly preferred,
[0218] polyols such as diols including, 4-butanediol,
1,5-pentanediol and 1,7 heptanediol, [0219] silane or polysilane
having at least one silanol group, or [0220] water.
[0221] The composition forms, after hydrosilylation, a silicone
elastomer which may be foamed or have gel properties. A foamed
composition does not transmit air through the body of the foam or
through the foam surface or both, for example incorporates cells
closed either by chemical or mechanical means. The term "silicone
gel" denotes a crosslinked silicone product characterized by a
degree of penetration of, for example, between 20 and 500 tenths of
a mm (measured by ASTM D 2137 penetrometry, weight of the rod and
of the cone: 62.5 g).
[0222] When the composition is prepared for a silicone gel it may
have at least one nonfunctionalized polyorganosiloxane comprising:
[0223] a) end siloxyl units of type M=(R.sup.6).sub.3SiO.sub.1/2 in
which the R.sup.6 radicals which are identical or different,
correspond to an optionally substituted linear or branched
C1-C.sub.6 alkyl group and/or a substituted or unsubstituted aryl
group, and [0224] b) identical or different siloxyl units of type
D=(R.sup.7).sub.2SiO.sub.2/2 in which the R.sup.7 radicals
correspond to the same definition as R.sup.6.
[0225] The physical properties of these gels are adjusted according
to the use by varying the levels of siloxyl units carrying
Si-alkenyl and SiH functional groups and when it is present by
varying the percentage by weight of nonfunctionalized
polyorganosiloxane, which is well known in the prior art.
[0226] To enhance the adhesive properties of a silicone gel, the
composition may further comprise a monofunctional
polyorganosiloxane carrying a single Si-alkenyl group per molecule
as taught by European patent application EP-1633830-A2.
[0227] Further, a composition may also comprise inorganic filler
such as reinforcing or bulking fillers. These fillers can be
provided in the form of very finely divided products, the mean
particle diameter of which is less than 0.1 .mu.m. These fillers
include in particular fumed silicas and precipitated silicas; their
specific surface is generally greater than 10 m.sup.2/g and
generally lies within the range 20-300 m.sup.2/g.
[0228] These fillers can also be provided in the form of more
coarsely divided products, with a mean particle diameter of greater
than 0.1 .mu.m. Mention may in particular be made, as examples of
such fillers, of ground quartz, calcium carbonate, diatomaceous
silicas, calcined clay, titanium oxide of the rutile type, iron,
zinc, chromium, zirconium or magnesium oxides, the various forms of
alumina (hydrated or nonhydrated), boron nitride, lithopone or
barium metaborate; their specific surfaces are generally less than
30 m.sup.2/g.
[0229] The filler may have a hydrophobic surface, which may be
obtained by treating the filler, e.g. with suitable silanes, short
chain siloxanes, fatty acids or resinous silicone materials.
[0230] Hexamethyldisilazane treated fumed silica may be considered,
or if translucence is to be maintained, vinyl "Q" reinforcing
resins may be used. A filler may be hydroplobic. Suitable materials
and processes for rendering the surface of fillers hydrophobic have
been described in the literature, and are known to the person
skilled in the art. The fillers can also be composed of a mixture
of several types of fillers with different particle sizes.
[0231] The composition may comprise a thixotropic agent. A
thixotropic agent confers on a composition properties whereby it
becomes viscous during application and reverts to higher viscosity
after application when no longer being worked. Thixotropes include
fillers such as silica, and certain silicone-based substances.
[0232] A composition may include additional components including
other adjuvants, preservatives including propyl gallate, extenders,
rheology regulators, adhesion promoters or adhesion reducers,
moisture vapor permeability (MVP) or moisture vapor transmission
rate (MVTR) promoters to prevent maceration of skin having
composition applied thereto, whereby skin can transpire and pass
liquid but still function as a sealant and bacterial barrier, and
the like. Suitably such additional components confer properties as
hereinbefore defined on the composition.
[0233] The composition may comprise active agents, which may have
any desired activity for the intended purpose, and include active
pharmaceutical ingredients (API's) and the like.
[0234] Antimicrobial agents, biocides and disinfectants may be
selected from silver, in particular nano crystalline silver, and
derivatives including silver complexes and salts such as ionic
silvers, silver zeolite, silver oxide, silver nitrate, silver
acetate, silver chloride, silver sulphadiazine), biguanides
including polyhexamethylene biguanide, chlorhexidine digluconate
and its acetate salts chlorhexidine acetate and diacetate, manuka
honey, peroxides (e.g. hydrogen peroxide), iodine (e.g. povidone
iodine), sodium hypochlorite, copper, copper complexes; zinc (e.g.
zinc oxide, zinc pyrithione), gold, gold complexes; phosphates,
amines, amides and sulphonamides (e.g. hexamidine, proflavine,
mafenide, nitrofurazone, norfloxacin); antibiotics (e.g.
gentamicin, bacitracin, rifampicin; alcohols and acids (e.g.
ethanol, phenoxy ethanol, mupirocin).
[0235] Nutrients, pain killers and other pain management techniques
suitably include analgesics and anesthetics and may be selected
from amethocaine, lignocaine, non-steroidal anti-inflammatory
drugs, anti inflammatories such as hydrocortisone, paraffin to
reduce adherence to the skin, urea to reduce dehydration of the
skin; buffering components to promote healing of the skin.
[0236] Heamostats may be selected from chitin, chitosan, kaolin;
antifibrinolytics such as amino acids, aminocaproic acid,
tranexamic acid, aminomethylbenzoic acid; Proteinase inhibitors
including aprotinin, alfa1 antitrypsin, C1-inhibitor, camostat;
Vitamin K and other hemostatics including vitamin K,
phytomenadione, menadione; fibrinogen including human fibrinogen;
local hemostatics including absorbable gelatin sponge, oxidized
cellulose, tetragalacturonic acid hydroxymethylester, adrenalone,
thrombin, collagen, calcium alginate, epinephrine; blood
coagulation factors including coagulation factor IX, II, VII and X
in combination, coagulation factor VIII, factor VIII inhibitor
bypassing activity, coagulation factor IX, coagulation factor VII,
von Willebrand factor and coagulation factor VIII in combination,
coagulation factor XIII, eptacog alfa (activated), nonacog alfa,
thrombin and systemic hemostatics: etamsylate, carbazochrome,
batroxobin romiplostim, eltrombopag.
[0237] Active agents may further include combination materials
including superabsorbers, odour management agents, wovens and non
wovens, gellable fibres; growth factors, wound
debridements--mechanical, autolytic and enzymatic; resorbable
dressings and micro structure to influence cell ingrowth; cells,
tissue (e.g. autologous treatments); indicators; dyes and
colourants and coloured indicators, whiteners such as zinc oxide
and titanium oxide.
[0238] The composition may be in a form that it may be dispensed in
any known manner, such as by pallet knife, syringe, static mixer,
roll-on applicator, spray, wipe, brush, foam, sponge, non-woven,
part integrated or fully integrated into dressing, or manually
applied. An applicator using a sponge is demonstrated with
Chloraprep i.e. http://www.chloraprep.co.uk. For a two part curing
system that requires mixing, a static mixer such as a double
barreled syringe with a mixing head may be used.
[0239] Preferably therefore the curable two part composition is
provided as at least one Part A and at least one Part B sealed in
or on respective receptacles or supports suitable for cooperatively
dispensing from a cooperative dispensing device, preferably sealed
in respective barrels or respective cassettes for a static mixer
such as a double barrel syringe, more preferably provided together
with a cooperating dispensing device such as a static mixer.
[0240] More preferably a syringe with a nozzle to allow insertion
of material into exposed transmission layer, or a spreader tip to
allow spread of material across the severed transmission layer
edge, or a combination thereof (spreader having plural projecting
apertures) may be used (e.g. Double-Syringe Prefilled Delivery
System (L-System), Medmix Systems Ag, fitted with static mixer and
spreader tip http://lwww.medmix.ch/L-SYSTEM.html).
[0241] For certain embodiments there is a clear advantage in using
an applicator with an integral spreader. Where material is applied
directly to the severed dressing edge, particularly in the case of
an extended severed edge, it is advantageous to manipulate this
material to ensure optimal placement. An integral spreader
minimises cross contamination when the sealant is manipulated.
During the manipulation cross contamination could relate to:
contamination of the sealant with a microbiological burden,
contamination of the sealant with foreign bodies, contamination of
the sealant with chemicals (such chemicals may have an influence on
the sealant) and contamination of personnel or equipment with the
sealant. For other embodiments there is advantage in using an
applicator without a spreader, for example for filling body
crevices etc.
[0242] Where the composition is a curing system chemical
contamination may adversely affect the cure process. For example
where the composition is a platinum catalysed RTV-2 silicone,
contact with latex or nitrile containing gloves may affect the
curing. The problem caused by the example given has been documented
in the dental press with regards to the delayed setting of
polyvinyl siloxane dental impression materials when mixed with
certain types of glove (Y. Walid, Z. AI-Ani and R. Gray, Silicone
impression materials and latex gloves. Is interaction fact or
fallacy?, Dent Update, 2012, 39, pp.:39-42).
[0243] In a medical setting an integral applicator with spreader
therefore overcomes the obstacle of a clinician being unable to use
a gloved finger (subject to the chemical composition of the glove)
to manipulate the sealant, overcomes the possibility of using an
ungloved finger, thus eliminating direct hand to patient contact
(not only would this approach be inappropriate for most clinical
settings, it would likely result with transfer of the curing
composition to the clinician's fingertip) and overcomes the
requirement to contaminate any other medical devices or implements
with the curing composition.
[0244] Dispensing may be by means of syringe or static mixer having
a nozzle head comprising a combination of spreader tip with plural
nozzles as hereinbefore and hereinbelow defined, for example a
spreader having plural projecting apertures. Preferably a nozzle
head comprises 2 to 10 nozzles for example 3 to 6 nozzles such as 3
or 5 nozzles. Nozzles preferably have low aperture to dispense
sealant to the interior portion within the exposed portion of
transmission layer. For example the spread of the nozzle head may
match the width of the bridging portion enabling dispensing on a
single insertion. This embodiment of dispenser for and mode of
dispensing composition benefits from a decreased burden and
decreased requirement for accuracy on the part of the operator, an
increase in mechanical accuracy of dispensing location and
continuous seal formation. It may also slightly reduce the
back-pressure at the syringe allowing the use of higher viscosity
composition. A substantial border region as hereinbefore defined
may contribute to seal integrity.
[0245] Preferably a nozzle head has moderate width or spread of
head for dispensing into exposed portion of a transmission layer on
a curve, e.g. a body contour, for example having from 2 to 4
nozzles, such as 2 or 3 nozzles. An alternative multi nozzle head
is flexible or deformable in two locations facilitating dispensing
into exposed portion of a transmission layer on a curve, e.g. a
body contour and/or dispensing into a location having obstructed
access. Such nozzle head comprises a flexible arm or restraint
through which the plural nozzles emerge. The arm is joined to the
main nozzle head and thereby to releasably to the static mixer,
optionally via flexible tubes. The arm may be bent to conform to an
arc. The tubes may similarly be bent to conform to generate an
angled nozzle. The tubes may beneficially increasing the entry
angle for dispensing.
[0246] The flexible arm is typically not elastic, i.e. it retains
the shape conferred for dispensing until bent to return to its
original shape or a different conformation. The flexible arm could
be formed of a deformable polymer or putty or the like or it could
be a mechanical flexible or deformable arm (i.e.
http://snakeclamp.com/or http://joby.com/gorillapod).
[0247] Preferably a dispenser has low profile and can be contained
within an imaginary cone. This dictates the maximum dimensions that
may advantageously be considered in the design of the dispenser to
allow a shallow entry angle relative to the skin to allow a nozzle
to be inserted into an exposed portion of transmission layer in a
dressing adhered to a patient.
[0248] Preferably the sealant is a TNP sealant which generates or
enhances a fluid-tight, preferably an air-tight, seal. In one
embodiment a composition comprises a RTV-2 silicone such as
Silpuran 2445.TM. which may optionally be modified to have
viscosity as hereinbefore defined. Modification of viscosity is as
known in the art and is suitably by incorporating filler such as
for example fumed silica or optionally translucent filler or resin
or reinforcing resin as hereinbefore defined, to achieve the
hereinbefore defined viscosity, or by combining Parts A and B and
allowing to pre-react to the hereinbefore defined viscosity before
application, or the like. Increasing cure rate is as known in the
art, for example increasing the amount of catalyst or reducing the
amount of catalyst inhibitor present, if any.
Method of Preparation
[0249] A further aspect is the preparation of a composition as
hereinbefore defined. Methods for preparing non-curing or curable
compositions as hereinbefore defined in 1 or more Parts are known
in the art. Preferably the method comprises loading composition or
respective parts thereof into an applicator or cassettes therefore
as hereinbefore defined.
[0250] A further aspect is a method for preparing a curable
composition as hereinbefore defined comprising the steps of:
combining polymers (i) and (ii) and catalyst (iii) as hereinbefore
defined to form at least one Part A and at least one Part B; in
manner suitable for cooperatively dispensing, for example for
cooperatively dispensing from a double barrel syringe.
Method of Sterilisation
[0251] A further aspect is a method of sterilising the curable
composition as hereinbefore defined comprising heating the one or
more parts, for example the at least one Part A and at least one
Part B sealed in respective thermally stable receptacles or
supports at an elevated temperature of 121.degree. C. or more for a
period of up to 28 hours, or by irradiating wherein in the case of
a 2 part curable composition the polymers (i) and (ii) and catalyst
(iii) are apportioned in at least one Part A and at least one Part
B in manner such that polymer (ii) is absent from Part A and
polymer (i) is absent from Part B or Part B incorporates a trace
amount of polymer (i) represented as molar ratio (Si--H unit or
moiety)/(alkenyl unit or moiety) of greater than or equal to 2000
with a radiation source selected from the group consisting of
gamma, x-ray, and e-beam radiation in effective sterilising
dose.
Device
[0252] A further aspect is in the form of a device suitable for use
in the field of woundcare, comprising a dispensing device having
one or plural barrel(s) or cassette(s), advancing means and
optional mixing means, said barrel(s) or cassette(s) comprising the
composition as hereinbefore defined, in the case of a two or more
part composition such that Parts A and B are contained in
respective barrels or cassettes, the device having means for
contacting respective Parts.
[0253] Preferably optional mixing means, contacting means and/or
advancing means are provided integral with or separate from the
device. Mixing means may be static or active. The device may
incorporate a dwell chamber for mixed Parts A and B to partially
cure to higher viscosity before being dispensed.
[0254] Preferably the device is disposable comprising integral
barrel(s) or cassette(s).
[0255] Preferably the device comprises an applicator for applying
composition comprising means to configure composition on
application, for example comprising an applicator with nozzle or
integral spreader or a combination thereof.
[0256] Preferably a device comprises a nozzle head comprising a
combination of spreader tip with plural nozzles as hereinbefore and
hereinbelow defined, for example a spreader having plural
projecting apertures. Preferably a nozzle head comprises 2 to 10
nozzles for example 3 to 6 nozzles such as 3 or 5 nozzles. Nozzles
preferably have low aperture to dispense sealant to the interior
portion within the exposed portion of transmission layer. For
example the spread of the nozzle head may match the width of the
bridging portion enabling dispensing on a single insertion. This
embodiment of dispenser for and mode of dispensing composition
benefits from a decreased burden and decreased requirement for
accuracy on the part of the operator, an increase in mechanical
accuracy of dispensing location and continuous seal formation. It
may also slightly reduce the back-pressure at the syringe allowing
the use of higher viscosity composition. A substantial border
region as hereinbefore defined may contribute to seal
integrity.
[0257] Preferably a nozzle head has moderate width or spread of
head for dispensing into exposed portion of a transmission layer on
a curve, e.g. a body contour, for example having from 2 to 4
nozzles, such as 2 or 3 nozzles. An alternative multi nozzle head
is flexible or deformable in two locations facilitating dispensing
into exposed portion of a transmission layer on a curve, e.g. a
body contour and/or dispensing into a location having obstructed
access. Such nozzle head comprises a flexible arm or restraint
through which the plural nozzles emerge. The arm is joined to the
main nozzle head and thereby to releasably to the static mixer,
optionally via flexible tubes. The arm may be bent to conform to an
arc. The tubes may similarly be bent to conform to generate an
angled nozzle. The tubes may beneficially increasing the entry
angle for dispensing.
[0258] The flexible arm is typically not elastic, i.e. it retains
the shape conferred for dispensing until bent to return to its
original shape or a different conformation. The flexible arm could
be formed of a deformable polymer or putty or the like or it could
be a mechanical flexible or deformable arm (i.e.
http://snakeclamp.com/or http://joby.com/gorillapod).
[0259] Preferably a dispenser has low profile and can be contained
within an imaginary cone. This dictates the maximum dimensions that
may advantageously be considered in the design of the dispenser to
allow a shallow entry angle relative to the skin to allow a nozzle
to be inserted into an exposed portion of transmission layer in a
dressing adhered to a patient.
[0260] In a further embodiment there is provided a novel device as
hereinbefore defined comprising a nozzle head comprising a
combination of spreader tip with plural nozzles as hereinbefore and
hereinbelow defined, for example a spreader having plural
projecting apertures. Preferably a nozzle head comprises 2 to 10
nozzles for example 3 to 6 nozzles such as 3 or 5 nozzles. Further
features are as hereinbefore described.
[0261] If required these systems may be used together with a
suitable skin-compatible sealant at the perimeter as defined in PCT
GB2012/000866.
[0262] A dressing as hereinbefore defined may be any wound
dressing, preferably is a wound dressing having a Si wound contact
surface, more preferably is a TNP dressing, optionally modified to
comprise a perimeter region as hereinbefore defined. Known TNP
dressings include: Smith & Nephew Disposable Kits for TNP such
as Smith & Nephew, RENASYS-F/AB, Abdominal Dressing Kit; Smith
& Nephew, RENASYS-F/P, Foam Dressing Kit With Port; Smith &
Nephew, RENASYS-G, Gauze Dressing Kit; Smith & Nephew, PICO.TM.
dressing kit; and KCI Kits for TNP including, V.A.C..TM. GranuFoam
Dressings Kits; and the like. Additional dressings and methods of
treating wounds with negative pressure are disclosed in the
following applications that are hereby incorporated by reference:
U.S. application Ser. No. 13/381,885, filed 30 Dec. 2011 and
published as US2012/0116334; U.S. application Ser. No. 12/886,088,
filed 20 Sep. 2010 and published as US2011/0213287; U.S.
application Ser. No. 13/092,042, filed 21 Apr. 2011 and published
as US2011/0282309; U.S. application Ser. No. 12/744,277, filed 20
Sep. 2010 and published as US2011/0028918; and U.S. application
Ser. No. 12/744,218, filed 20 Sep. 2010 and published as
US2011/0054421, also WO2011/000622, WO 2011i000621, WO2011/135285,
WO2011/135286, U.S. Pat. No. 7,964,766 and U.S. Pat. No. 7,615,036
(all Smith & Nephew) the contents of which are incorporated
herein by reference. Conventional TNP dressings are applied with a
drape placed thereover, of which the second face is air-tight.
[0263] Such dressings can additionally comprise a tissue (wound)
contact layer, a negative pressure distribution and transmission
layer and an optional wound exudate absorbing layer as hereinbefore
defined.
[0264] Preferably the composition is dispensed to a composite TNP
dressing such as the PICO.TM. dressing. A composite dressing
incorporates an integral air-tight backing layer (also referred to
herein as a wound cover or drape), that may be made of a gas
impermeable membrane and integral TNP therapy layers, such as one
or more negative pressure transmission or distribution layers, a
tissue (wound) contact layer, an absorbent material layer such as a
wound exudate absorbing layer or acquisition distribution layer
(ADL) any of these optionally including a superabsorbent polymer
(SAP), said layers positioned beneath the backing layer, and the
backing layer or wound cover optionally allows transpiration or
liquid evaporation from wound exudate, as for example with the
PICO.TM. dressing.
[0265] For example, one or more transmission layers or other layers
may be positioned or enclosed between a backing layer and an
optional wound contact layer. The transmission layer(s) may be in
turn enclosed between the backing layer and (optional wound contact
layer and) a wound site over which the dressing is configured to be
positioned, for example sealed therebetween. The composite dressing
may be supplied together with a number of adhesive strips comprised
of drape material or may omit such strips with sealing by means of
a sealant as disclosed in PCT/GB2012/000866, the contents of which
are incorporated herein by reference.
[0266] The composition may therefore be applied to any dressing
which it is desired to cut to size or shape or to profile or
articulate. Cutting is simply by removing the excess portion and
retaining the required portion including negative pressure
port.
[0267] Preferably the composition is dispensed to a trimmable
dressing, having a main dressing portion in fluid (gas)
communication with additional dressing portions or cells. One or
more additional portions or cells may be removed to provide a
dressing having size or shape or profile or articulation to be
compatible with a wound or wound site to be dressed. Preferably
portions or cells may be retained to provide a large surface area,
or elongate, dressing to dress a similarly large surface area or
elongate wound, or portions or cells may be removed to dress a
correspondingly reduced surface area or reduced length wound;
preferably one or more additional portions or cells may be
conformed to provide a shaped dressing to dress a similarly shaped
wound or to dress a wound incorporating or adjacent a protrusion
such as a fixation device, for example a pin, or such as a body
part such as a digit; preferably one or more additional portions or
cells may be conformed to provide a profiled dressing to dress a
similarly profiled wound or wound site, such as a wound located on
complex body topography; preferably one or more additional portions
or cells may be articulated to dress a similarly articulated wound
or wound site such as a wound located on a joint.
[0268] In an advantage the composition may be used to seal a
trimmable dressing as disclosed in U.S. Provisional Application
Ser. No. 61/800,040, filed Mar. 15, 2013, titled "WOUND DRESSING
AND METHOD OF TREATMENT," the contents of which are incorporated
herein directly and by reference.
[0269] A trimmable dressing is preferably a wound treatment
apparatus for treatment of a wound site comprising: [0270] a
backing layer having an upper surface and a lower surface and
defining a perimeter configured to be positioned over skin
surrounding a wound site; [0271] a transmission layer configured to
be positioned below the backing layer; and [0272] one or more ports
configured to transmit negative pressure through the backing layer
for the application of topical negative pressure at the wound site;
[0273] wherein the apparatus comprises a plurality of cells or
regions separated by one or more trimmable portions. Trimmable
portion(s) may be bridging portions as hereinbefore defined.
[0274] In some embodiments, the plurality of cells forms a
plurality of repeating negative pressure treatment modules.
[0275] In one embodiment, one or more of the modules can be removed
and the removed module(s) can subsequently be used to provide
negative pressure to the wound site. In another embodiment, one or
more modules can be removed and the remaining module(s) can
subsequently be used to provide negative pressure to the wound
site. In further embodiments, the trimmable portions may have a
maximum width of 50 mm (or approximately 50 mm), 40 mm (or
approximately 40 mm), 30 mm (or approximately 30 mm), 20 mm (or
approximately 20 mm), or even 15 mm (or approximately 15 mm). In
some embodiments, the trimmable portion may be from 10 mm to 20 mm
(or approximately 10 mm to approximately 20 mm). The one or more
trimmable portions may comprise one or more bridging portions
having a smaller width as compared to the width of an adjacent cell
or region. For example, the bridging portion may have a maximum
width of 1/8, 1/4, or 1/3 (or approximately 1/8, 1/4, or 1/3) of a
width of an adjacent cell or region. The plurality of cells or
regions may comprise an absorbent material, the absorbent material
positioned between the transmission layer and the backing layer.
The one or more trimmable portions may comprise an absorbent
material, the absorbent material positioned between the
transmission layer and the backing layer. In other embodiments, no
absorbent material is positioned between the transmission layer and
the backing layer. Some embodiments may further comprise an
acquisition distribution layer having a similar footprint to the
transmission layer, the acquisition distribution layer configured
to be positioned above the transmission layer. The apparatus is
preferably as further hereinbelow defined.
[0276] Exposed portion(s) as hereinbefore defined are the result of
removing a portion of the wound dressing, which may be by any
envisaged means, for example cutting the wound dressing or tearing
along a weakened line. Composite wound dressings may comprise a
border for affixing around a wound, about a central wound contact
portion. The dressing as hereinbefore defined may include a backing
layer and wound contact layer of similar footprint or surface area
to the transmission layer or other layers enclosed therebetween,
for example is a borderless dressing) or of greater footprint or
surface area than the transmission layer enclosed therebetween (for
example is a bordered dressing). Exposed portion(s) as hereinbefore
defined result from removing a portion of the wound dressing as
hereinbefore defined directly enclosing the transmission layer or
other layers, for example by cutting into or through the backing
layer and wound contact layer and the transmission layer
therebetween.
[0277] Embodiments of dressings described herein address the
problem of providing dressings in a range of sizes or shapes to
accommodate irregularly shaped wounds or body topography, for
example vein harvest wound dressings accommodating variations in
height and leg-length of individuals, the provision of which is
impractical both to the manufacturer and to the user. Embodiments
enhance adaptability of existing dressings, including more recently
introduced multisite dressings such as trilobes and quadrilobes.
Certain embodiments enable a portion of a dressing to be removed to
create a main wound dressing of desired size or shape or profile or
articulation, and sealing exposed portion(s) thereof to contain a
negative pressure.
[0278] The portion(s) of the wound dressing may be removed to size
the main wound dressing portion for positioning over a wound as
hereinbefore defined, for example an incisional wound, an elongate
leg wound, an arcuate incisional wound and the like. Similarly the
portion(s) of the wound dressing may be removed to shape the main
wound dressing portion for positioning over a wound as hereinbefore
defined, such as a flap wound, about a protruding device such as a
fixation device or a protruding body part, to profile the main
wound dressing for positioning over a wound as hereinbefore
defined, for example on complex body topography, or to articulate
the main wound dressing for positioning over a wound as
hereinbefore defined for example on a flexing joint. The wound
treatment apparatus may be rolled into a tape which can be cut
along the one or more bridging portions. Cutting along the bridging
portion may sever adjacent cells.
[0279] The composition may alternatively be advantageously
dispensed to seal a dressing for treatment of a wound site
comprising: [0280] a backing layer having an upper surface and a
lower surface otherwise a backing sheet as hereinbefore termed and
defining a perimeter configured to be positioned over skin
surrounding a wound site; [0281] a transmission layer configured to
be positioned beneath the backing layer; or otherwise positioned at
or on one side of one face of the backing sheet and [0282] a
plurality of ports configured to transmit negative pressure spaced
apart on the backing layer.
[0283] The wound treatment apparatus may be configured to be rolled
into a tape. The plurality of ports each may comprise an opening in
the backing layer covered with a releasable tab. The transmission
layer may comprise one or more bridging portions having a smaller
width than adjacent portions of the transmission layer. A negative
pressure may be established at a wound site by means of any one of
the plurality of ports, the remainder of which may remain sealed or
may be removed with a section of dressing. The wound treatment
apparatus may be used in any desired length by cutting between
adjacent ports.
[0284] In above dressings, the wound treatment apparatus further
comprises an optional wound contact layer, with the transmission
layer(s) positioned between the backing layer and the wound contact
layer. The transmission layer(s) may be in direct or indirect
contact with a lower surface of the backing layer. In some
embodiments, the one or more transmission layers comprise a first
layer comprising a spacer material configured to vertically wick
fluid. The one or more transmission layers may further comprise a
second layer comprising an acquisition distribution material
configured to horizontally wick fluid, the second layer positioned
above the first layer. One of the first layer and the second layer,
or both, may be present in the one or more bridging portions. In
other embodiments, the one or more transmission layers comprise an
acquisition distribution material configured to horizontally wick
fluid. In some embodiments, the port may comprise an opening in the
backing layer. The port may comprise a port member attached to the
backing layer over an opening in the backing layer. The port member
may be sealed to the upper surface of the backing layer. Some
embodiments may further comprise an absorbent material between the
backing layer and the transmission layer having a similar footprint
to that of the transmission layer(s). Absorbent material may be
present or absent in bridging portion(s) as hereinbefore defined.
Some embodiments of the one or more transmission layers may further
comprise an acquisition distribution layer between the backing
layer and the optional wound contact layer and the transmission
layer and/or absorbent layer having a similar footprint to that of
the absorbent material and/or absorbent layer. The one or more
transmission layers may further comprise a spacer material
configured to distribute negative pressure, the spacer material
having a similar footprint to the acquisition distribution
material, the spacer material configured to be positioned beneath
the acquisition distribution material. Acquisition distribution
layer or material may be present or absent in bridging portion(s)
as hereinbefore defined. The acquisition distribution material may
be provided as the transmission material or layer
[0285] The transmission layer (hereinafter layer(s)) may have a
rectangular shape having a longitudinal axis extend along its
length. The transmission layer may comprise one or more bridging
portions centered on the longitudinal axis. The transmission layer
may comprise three or more bridging portions centered on the
longitudinal axis. The one or more bridging portions may also be
offset from the longitudinal axis. The one or more bridging
portions may have a width that is less than 1/3 the width of
adjacent portions of transmission layer. The one or more bridging
portions may have a width that is less than 1/4 the width of
adjacent portions of transmission layer. The one or more bridging
portions may have a width that is less than 1/8 the width of
adjacent portions of transmission layer. As is used herein, a
smaller width represents a narrowing of or neck or constriction in
transmission layer with respect to adjacent portions thereof. The
transmission layer may have a T-shape with a bridging portion on
each leg of the T. The transmission layer may have a T-shape with
at least one bridging portion on each leg of the T. The
transmission layer may comprise a plurality of cells each separated
by one or more bridging portions. The transmission layer may
comprise a plurality of cells, and wherein each of the plurality of
cells is connected to at least one adjacent cell by one or more
bridging portions, preferably the bridges provide for gas
communication between adjacent cells.
[0286] Some embodiments may further comprise a fluidic connector
configured to supply negative pressure to the port. Some
embodiments may further comprise a source of negative pressure
configured to supply negative pressure through the port. Negative
pressure may be established at a wound site by means of any one of
the plurality of ports, or by means of multiple ports of the
plurality of ports, the remainder of which may remain sealed or may
be removed with a section of dressing. Some embodiments may further
comprise one or more separate or integral adhesive strips or
sealing strips. Strips are configured to retain and seal the
backing layer to skin surrounding a wound after the apparatus is
cut along or across the one or more bridging portions, i.e between
adjacent cells or ports. Strips may be comprised of backing layer
material, such as polyurethane or hydrocolloid, or silicone based
material such as OPSITE.sup..diamond. FLEXIFIX.sup..diamond. or
OPSITE.sup..diamond. FLEXIFIX.sup..diamond. Gentle.
[0287] In a further aspect there is provided a novel apparatus as
hereinbefore defined. Accordingly there is provided a wound
treatment apparatus for treatment of a wound site comprising:
[0288] a backing layer having an upper surface and a lower surface
and defining a perimeter configured to be positioned over skin
surrounding a wound site; [0289] a transmission layer configured to
be positioned below the backing layer; and [0290] one or more ports
configured to transmit negative pressure through the backing layer
for the application of topical negative pressure at the wound site;
[0291] wherein the apparatus comprises a plurality of cells or
regions separated by one or more trimmable portions. Features are
as hereinbefore defined.
[0292] The one or more ports may each comprise an opening in the
backing layer covered with a releasable tab, and negative pressure
may be applied to the backing layer through at least one of the
openings. Some embodiments may comprise multiple ports configured
to transmit negative pressure through the backing layer, each port
corresponding to a separate negative pressure treatment module.
Some embodiments may further comprise a wound contact layer
configured to be positioned beneath the transmission layer, the
wound contact layer further configured to seal to the backing layer
around the perimeter.
[0293] In some embodiments, the plurality of cells may be
approximately the same size, approximately square, and configured
in a grid. In other embodiments, the plurality of cells may be
configured in a T-shape. In other embodiments, the plurality of
cells may be configured into a roll. In other embodiments, the
plurality of cells may be configured in a linear arrangement. In
some embodiments, each of the plurality of cells may be configured
with one of the one or more ports. In other embodiments, at least
two of the plurality of cells may be each configured with one of
the one or more ports. The apparatus may further comprise a source
of negative pressure connected to some or all of the one or more
ports. In some embodiments, the dressing may comprise an exposed
portion of transmission layer. The exposed portion may be sealed
with a sealant or adhesive material. The apparatus is preferably as
further hereinbefore defined.
[0294] In some embodiments, the at least one material layer of the
first portion comprises one or more of a transmission layer such as
reticulated open-cell foam, woven material, non-woven material, 3D
knit fabric, Baltex 7970 weft knitted polyester, acquisition
distribution material, DryWeb TDL2, SlimCore TL4, or the like. The
at least one material of the first portion can additionally or
alternatively comprise an absorbent layer, for example a
superabsorbent pad comprising cellulose fibers and superabsorbent
particles, MH460.101, ALLEVYN.TM. foam, Freudenberg 114-224-4, or
Chem-Posite.TM. 11C-450. In some embodiments, the bridging portion
comprises at least one material layer comprising one or more
of-eticulated open-cell foam, woven material, non-woven material,
3D knit fabric, Baltex 7970 weft knitted polyester, acquisition
distribution material, DryWeb TDL2, SlimCore TL4, or the like. In
some embodiments, the at least one material layer of the bridging
portion should transmit a negative pressure of at least -40 mmHg
against a set point in the range -60 to -200 mmHg with an air leak
of 50 cc/minute. In some embodiments, the at least one material
layer of the bridging portion should experience a pressure
differential of approximately -25 mmHg or less (that is, closer to
zero) at a set point of -200 mmHg with an air leak of 50 cc/minute
over an approximately 20 mm.+-.1 mm distance. In other embodiments,
the at least one material layer of the bridging portion should
experience a pressure differential of approximately -5 mmHg or less
(that is, closer to zero) at a set point of -200 mmHg with an air
leak of 50 cc/minute over an approximately 20 mm.+-.1 mm distance.
In some embodiments, the at least one material layer of the
bridging portion has a height, in an uncompressed state, of at
least 1 mm (or approximately 1 mm), at least 3 mm (or approximately
3 mm), at least 4 mm (or approximately 4 mm), or at least 5 mm (or
approximately 5 mm), and a width of at least 1 mm (or approximately
1 mm), or at least 2 mm (or approximately 2 mm), at least 3 mm (or
approximately 3 mm), at least 4 mm (or approximately 4 mm), or at
least 5 mm (or approximately 5 mm). In some embodiments, the at
least one material layer of the bridging portion has a maximum
height, in an uncompressed state, of 9 mm (or approximately 9 mm)
for purposes of being more easily re-sealable when cut. In some
embodiments in which the dressing is sealed with a sealant, the at
least one material layer can be resilient to compression such that
a height of a sealed portion, in a compressed state, is
substantially the same as the height of the sealed portion in an
uncompressed state. In one embodiment, the at least one material
layer of the bridging portion comprises a spacer material having a
height of at least 2 mm (or approximately 2 mm) and a width of at
least 1 mm (or approximately 1 mm). In one embodiment, the at least
one material layer of the bridging portion comprises a reticulated
open-cell foam having a height of at least approximately 5 mm and a
width of at least approximately 3 mm, which, when wet, may
experience a pressure differential of -8.9 (or approximately -8.9)
mmHg. In another embodiment, the at least one material layer of the
bridging portion comprises an acquisition distribution layer (e.g.,
SlimCore TL4) having a height of at least approximately 2 mm and a
width of at least approximately 4 mm. Such dimensions can represent
an uncompressed dimension of the material layer of the bridging
portion. In one embodiment, the at least one material layer of the
bridging portion is not compressible.
[0295] We have found that a composition when dispensed to seal a
dressing in manner as hereinbefore defined, may provide an
advantageous seal in relation to an exposed trimmed portion or
bridging portion comprising material layer(s) which undergo no
change or substantially no change in compressibility on initiation
of negative pressure, i.e. is resilient to or substantially
resilient to compression induced by negative pressure, or which
undergo a substantially similar compression to or lesser
compression than the composition seal, on initiation of negative
pressure, i.e is substantially equally resilient or less resilient
than the composition seal to compression induced by negative
pressure. In particular in relation to a curing or hardening
system, this relative compressibility is in relation to the cured
elastomer or hardened seal. Preferably a composition forms a seal
which is compressible to touch in relation to material layer(s)
which are substantially non-compressible or compressible to a
lesser degree, on initiation of negative pressure, than the seal.
Preferably the one or more trimmable portions or briding portions
comprise material substantially resilient to the application of
negative pressure, preferably the bridging portion(s) have height
which is substantially unchanged on the application of negative
pressure, preferably having height which is reduced by less than or
equal to 10%, more preferably 8%, most preferably 5%, on the
application of negative pressure. This ensures a smooth surface to
the dressing and minimal discomfort provided to the wearer, if
negative pressure is applied after sealing the dressing, and also
ensures that the seal remains intact and is not ruptured if
negative pressure is applied before sealing the dressing and is
subsequently temporarily interrupted.
[0296] In some embodiments, the bridging portion comprises the same
layer(s) as the first portion. In other embodiments, the bridging
portion comprises fewer layers than the first portion. In some
embodiments, the layer(s) in the bridging portion have a smaller
width than the layer(s) in the first portion. In some embodiments,
the layer(s) in the bridging portion have a dimension that is
smaller than the layer(s) in the first portion (for example, the
individual or combined height of the layer(s) in the bridging
portion is smaller than the height of the layer(s) in the first
portion. In other embodiments, the layer(s) in the bridging portion
have the same width as the layer(s) in the first portion. In some
embodiments, the bridging portion connects the first portion to an
adjacent portion having a similar layered construction and/or width
as the first portion. In some embodiments, there are multiple
bridging portions that may connect a first portion to multiple
adjacent portions, or may connect between multiple adjacent
portions.
Kit and Components Thereof
[0297] A further aspect is a kit for use in the field of wound care
comprising a dressing for overlying a wound and skin thereabout
which may be cut to size or shape as hereinbefore defined together
with a composition as hereinbefore defined.
[0298] Some kits comprise a vacuum pump.
[0299] In a particular advantage, the kit, sealant composition
and/or dressing or wound cover may be terminally sterile.
Techniques are known for sterilising apparatus, such as dry heat,
steam, radiation and the like. GB1020005.3, GB 1019997.4 and
GB1104512.7 disclose terminally sterilisable 2 part compositions
and methods for their sterilisation. Methods include heat
sterilisation and radiation sterilisation, in particular gamma,
e-beam or x-ray radiation sterilisation. Preferably the sealant is
terminally sterilisable or sterile and is sterilized prior to
dispensing by heating the first and second parts in a thermally
stable receptacle or support at an elevated temperature of
121.degree. C. or more for a period of up to 28 hours, or by
irradiating the first and second parts with a radiation source
selected from the group consisting of gamma, x-ray, and e-beam
radiation with a dose that provides an effective sterility
assurance level.
[0300] A further aspect is a method for dispensing or releasing,
and curing a composition as hereinbefore defined, comprising
dispensing into a desired location at curing temperature for curing
time.
[0301] The composition may be manually mixed and dispensed.
Alternatively any form of dispensing device may be employed, for
example the composition may be dispensed by means of a cooperative
dispensing device cooperatively dispensing, for example by means of
a double barrel syringe, for example by activating respective
barrels of a double barrel syringe, or loading respective cassettes
therefore and activating.
[0302] A further aspect is an elastomer comprising a cured
composition as hereinbefore defined,
Method of Use
[0303] A further aspect is a method for dispensing a composition as
hereinbefore defined comprising:
optionally combining Parts A and B of a curable composition as
hereinbefore defined thereby initiating cure; dispensing
composition into a location as hereinbefore defined; after a
suitable period an optionally elastomeric seal is formed.
[0304] A further aspect is a method for sealing a woundcare
dressing comprising:
cutting a dressing to size or shape; positioning the dressing
overlying a wound and skin thereabout; optionally combining Parts A
and B of a curable composition as hereinbefore defined thereby
initiating cure; dispensing composition into a location as
hereinbefore defined; after a suitable period an optionally
elastomeric seal is formed at the severed dressing edge.
[0305] Preferably the composition is dispensed by means of a
syringe for example a cooperative dispensing device as hereinbefore
defined cooperatively dispensing, for example by means of a double
barrel syringe, for example by activating respective barrels of a
double barrel syringe, or loading respective cassettes therefore
and activating, preferably wherein the syringe incorporates
integral means to configure the dispensed sealant, for example an
integral spreader head.
Method of Treatment
[0306] A further aspect is a method for sealing a dressing or for
treating a wound site, of a human or animal subject in need thereof
comprising: [0307] dressing the wound site with a dressing, as
hereinbefore defined, exposing a portion thereof as hereinbefore
defined and [0308] dispensing a composition as hereinbefore
defined.
[0309] Preferably the method comprises: [0310] providing a wound
dressing as hereinbefore defined comprising: [0311] a backing
layer; and [0312] a transmission layer positioned beneath the
backing layer, [0313] removing a portion of the wound dressing to
create a main wound dressing portion with one or more exposed
portions; [0314] positioning the main wound dressing portion over a
wound; [0315] sealing the main wound dressing to skin surrounding
the wound, and further sealing further sealing the one or more
exposed portions of the main wound dressing portion; and [0316]
applying negative pressure to the wound through the backing layer
of the main wound dressing portion.
[0317] In some embodiments of the method, removing a portion of the
wound dressing comprises cutting the wound dressing across at least
one of the one or more bridging portions. At least a portion of the
wound dressing may comprise pre-cut score marks to facilitate
removing of the portion of wound dressing. The dressing may
comprise a plurality of openings in the backing layer covered with
a releasable tab, and negative pressure may be applied to the
backing layer through one of the openings. The dressing may
comprise a plurality of openings in the backing layer covered with
a releasable tab, and negative pressure may be applied to the
backing layer through two or more of the openings.
[0318] The portions of the wound dressing may be removed to size
the main wound dressing portion for positioning over an incisional
wound. The portions of the wound dressing may be removed to size
the main wound dressing portion for positioning over an elongate
leg wound. The portions of the wound dressing may be removed to
size the main wound dressing portion for positioning over an
arcuate incisional wound.
[0319] In another embodiment, a method of treating a wound is
provided, comprising: [0320] providing a wound dressing comprising
a backing layer, a transmission layer beneath the backing layer,
and a plurality of spaced apart openings in the backing layer each
covered with a releasable tab, the wound dressing configured into a
length or roll; [0321] optionally unrolling a portion of the wound
dressing from the roll; [0322] removing a portion of the wound
dressing from the length or roll, the removed portion comprising at
least one opening in the backing layer covered with a releasable
tab; [0323] positioning the removed portion of the wound dressing
over a wound; and [0324] applying negative pressure through at
least one opening in the backing layer after a releasable tab has
been removed.
[0325] Preferably dispensing a sealant composition is by means of a
device as hereinbefore defined.
[0326] Preferably the dressing is adhered over the wound site with
at least an adhesive underside of the dressing or an adhesive
disposed on at least an underside of the dressing.
[0327] Preferably the method further comprises adjusting the
position of the dressing before the composition is dispensed.
[0328] Preferably the sealant is dispensed after dressing the wound
site with the dressing.
[0329] Preferably the wound dressing is adapted to contain a
negative pressure, the method additionally comprising applying
negative pressure to the wound site using a source of negative
pressure connected to the wound site.
[0330] Preferably applying negative pressure is conducted before
and after dispensing sealant.
[0331] Preferably applying negative pressure is by means of a
portable negative pressure source in fluid communication with the
wound dressing located over a wound site.
[0332] Preferably the method includes monitoring transmitted
negative pressure at the wound against generated negative
pressure.
[0333] Preferably a dressing is a combination TNP therapy dressing
incorporating fluid-tight backing layer, functional wound therapy
layers and an integral attachment for a negative pressure source,
preferably a portable and/or periodic negative pressure source by
means of which negative pressure is applied to the wound site
through or under the backing layer. Preferably an aperture is
created into or under the drape so as to connect the wound site to
the source of negative pressure.
[0334] A wound packing material may be located so as to partially
or completely fill the wound site.
[0335] Providing the sealant may be by means of dispensing a
sealant composition as hereinbefore defined by the method as
hereinbefore defined.
[0336] The method may include monitoring transmitted negative
pressure against generated negative pressure. This may be used to
provide the user with feedback during the dressing application.
Typically NP is monitored at the pump, or alternatively at end of
port.
[0337] Preferably the dressing is applied, the NP source activated,
pump down initiated, detecting for alarms indicating NP loss, rub
down dressing to close off any sites of NP loss, apply sealant at
severed edges.
[0338] In an advantage, providing the sealant is by means of
dispensing a sealant composition, wherein the composition is a
fluid that when dispensed forms a material capable of making a
substantially fluid-tight seal.
[0339] Preferably the method comprises combining at least two
pre-polymers to form the sealant.
[0340] Preferably the dressing is part of a portable NPWT system.
The exudate is managed in a portable canister or within the
dressing. The negative pressure source is portable or may be
connected intermittently. Preferably the skin contact layer is an
adhesive silicone gel, other adhesive or combination of adhesive
silicone gel and other adhesive.
[0341] Portable composite TNP dressings are commercially available
and include Prevena (KCI), NPD1000 NP wound Therapy System (Kalypto
Medical Inc), PICO (Smith & Nephew), amongst others, and are
more extensively described in the literature, for example in
PCT/GB2011/000629, the contents of which are incorporated herein by
reference.
[0342] Upon the application of negative pressure with the pump, the
dressing may in some embodiments partially collapse and present a
wrinkled appearance as a result of the evacuation of some or all of
the air underneath the dressing. In some embodiments, the pump may
be configured to detect if any leaks are present in the dressing,
such as at the interface between the dressing and the skin
surrounding the wound site. Should a leak be found, such leak is
preferably remedied prior to continuing treatment.
[0343] Treatment of the wound site preferably continues until the
wound has reached a desired level of healing. In some embodiments,
it may be desirable to replace the dressing after a certain time
period has elapsed, or if the dressing is full of wound fluids.
During such changes, the pump may be kept, with just the dressing
being changed.
[0344] A further aspect provides the use of a composition, kit or
apparatus as hereinbefore defined for dressing wounds, preferably
for negative pressure wound therapy dressing of wounds as
hereinbefore defined. The sealant composition, kit and apparatus
may be useful for example in sealing medical dressings, for example
in restraining egress of wound exudate or ingress of air or
infection, in addition to providing a vacuum seal for TNP
application.
[0345] Such use includes use on wounds selected from chronic,
acute, traumatic, sub-acute and dehisced wounds, ulcers (such as
pressure or diabetic), partial-thickness burns and flaps and
grafts. These include open, moist, granulating wounds, preferably
surgical wounds such as those resulting from excision of ulcers,
cancerous tissue such as perianal and perineal wounds and the like.
For optimum healing of such wounds, the wound should be prevented
from closing in on itself and allowing fluids to accumulate, whilst
at the same time allowing the tissue around the wound to
progressively contract, and the wound to shrink. Wound filling
materials in NPWT therefore function as a type of "stent",
supporting the wound and holding it open.
[0346] A sealant composition, kit or apparatus is particularly
suited for use in clean, aseptic or sterile applications.
Preferably the composition, kit or apparatus is rendered sterile,
as known in the art or as hereinbefore defined, and packaged within
barrier means. Further barrier means provide a barrier to
infection, whereby the composition, kit or apparatus is a double
wrapped item, this allows for the removal of the first layer of
sterile sealed packaging to reveal receptacles or supports such as
cartridges for or incorporated in a syringe, adhesive strips and
the like, which are completely sterile inside and out, facilitating
entry into a sterile environment. The composition omitting a
further barrier means would comprise a non-sterile external surface
of receptacles or supports and associated barrier means. If it is
not possible to sterilise the composition using standard conditions
for medical apparatus as hereinbefore described, it may not be
possible to take such a composition into a sterile field.
[0347] A sealant for medical dressings may be applied in any known
or novel manner. WO 00/74738 (Guyuron) discloses use of silicone
based RTV-2 compositions to seal wounds i.a to minimise potential
infections. The sealant may suitably therefore be used by casting
on top of the wound and surrounding skin and allowing to cure.
[0348] A further aspect provides the medical use of a kit, sealant
or apparatus as hereinbefore defined.
[0349] Embodiments have one or more of the following
advantages:
[0350] Allows severed dressing edges to be sealed readily.
[0351] Sealing of 3-dimensional dressing perimeters following
complex body contours enhancing the ability to remove or reduce
leaks.
[0352] Sealing of custom sized, shaped, contoured, articulated
dressings.
[0353] Sealing of dressings where the borders conform to body
geometries with tight external radii or are otherwise subject to
high levels of deformation.
[0354] Sealing of systems where the dressing will be subject to a
great deal of movement (e.g. neck, shoulder, underarm, elbow,
forearm, wrist, hand, groin, knee, ankle, heel, foot).
[0355] A number of specific embodiments are given hereinbelow,
appropriate for conventional Advanced Wound Dressings, conventional
NPWT Drapes/Dressings or PICO.TM. and a sealant as hereinbefore
defined. General references hereinbelow are however not to be
construed as limiting to the specific figure or embodiment which
they are intended to illustrate, rather for the sake of avoiding
undue duplication such description may be present in the following
section although of equal or greater relevance and equally
pertinent to the foregoing.
[0356] FIG. 1 illustrates an embodiment of a TNP wound treatment
system 100 comprising a wound dressing 110 in combination with a
pump 150. As stated above, the wound dressing 110 can be any wound
dressing embodiment disclosed herein including without limitation
dressing embodiment or have any combination of features of any
number of wound dressing embodiments disclosed herein. Here, the
dressing 110 may be placed over a wound as described previously,
and a conduit 130 may then be connected to the port 120, although
in some embodiments the dressing 101 may be provided with at least
a portion of the conduit 130 preattached to the port 120.
Preferably, the dressing 110 is provided as a single article with
all wound dressing elements (including the port 120) pre-attached
and integrated into a single unit. The wound dressing 110 may then
be connected, via the conduit 130, to a source of negative pressure
such as the pump 150. The pump 150 can be miniaturized and
portable, although larger conventional pumps may also be used with
the dressing 110.
[0357] In some embodiments, the pump 150 may be attached or mounted
onto or adjacent the dressing 110. A connector 140 may also be
provided so as to permit the conduit 130 leading to the wound
dressing 110 to be disconnected from the pump, which may be useful
for example during dressing changes.
[0358] FIGS. 2A-D illustrates the use of an embodiment of a TNP
wound treatment system being used to treat a wound site on a
patient. FIG. 2A shows a wound site 200 being cleaned and prepared
for treatment. Here, the healthy skin surrounding the wound site
200 is preferably cleaned and excess hair removed or shaved. The
wound site 200 may also be irrigated with sterile saline solution
if necessary. Optionally, a skin protectant may be applied to the
skin surrounding the wound site 200. If necessary, a wound packing
material, such as foam or gauze, may be placed in the wound site
200. This may be preferable if the wound site 200 is a deeper
wound.
[0359] After the skin surrounding the wound site 200 is dry, and
with reference now to FIG. 2B, the wound dressing 110 may be
positioned and placed over the wound site 200. Preferably, the
wound dressing 110 is placed with the wound contact layer 2102 over
and/or in contact with the wound site 200. In some embodiments, an
adhesive layer is provided on the lower surface 2101 of the wound
contact layer 2102, which may in some cases be protected by an
optional release layer to be removed prior to placement of the
wound dressing 110 over the wound site 200. Preferably, the
dressing 110 is positioned such that the port 2150 is in a raised
position with respect to the remainder of the dressing 110 so as to
avoid fluid pooling around the port. In some embodiments, the
dressing 110 is positioned so that the port 2150 is not directly
overlying the wound, and is level with or at a higher point than
the wound. To help ensure adequate sealing for TNP, the edges of
the dressing 110 are preferably smoothed over to avoid creases or
folds.
[0360] With reference now to FIG. 2C, the dressing 110 is connected
to the pump 150. The pump 150 is configured to apply negative
pressure to the wound site via the dressing 110, and typically
through a conduit. In some embodiments, and as described above in
FIG. 1, a connector may be used to join the conduit from the
dressing 110 to the pump 150. Upon the application of negative
pressure with the pump 150, the dressing 110 may, in some
embodiments, partially collapse and present a wrinkled appearance
as a result of the evacuation of some or all of the air underneath
the dressing 110. In some embodiments, the pump 150 may be
configured to detect if any leaks are present in the dressing 110,
such as at the interface between the dressing 110 and the skin
surrounding the wound site 200. Should a leak be found, such leak
is preferably remedied prior to continuing treatment.
[0361] Turning to FIG. 2D, additional fixation strips 210 may also
be attached around the edges of the dressing 110. Such fixation
strips 210 may be advantageous in some situations so as to provide
additional sealing against the skin of the patient surrounding the
wound site 200. For example, the fixation strips 210 may provide
additional sealing for when a patient is more mobile. In some
cases, the fixation strips 210 may be used prior to activation of
the pump 150, particularly if the dressing 110 is placed over a
difficult to reach or contoured area.
[0362] Treatment of the wound site 200 preferably continues until
the wound has reached a desired level of healing. In some
embodiments, it may be desirable to replace the dressing 110 after
a certain time period has elapsed, or if the dressing is full of
wound fluids. During such changes, the pump 150 may be kept, with
just the dressing 110 being changed.
[0363] FIGS. 3A-C illustrates cross-sections through a wound
dressing 2100 similar to the wound dressing of FIG. 1 according to
an embodiment of the disclosure. A view from above the wound
dressing 2100 is illustrated in FIG. 1 with the line A-A indicating
the location of the cross-section shown in FIGS. 3A and 3B. The
wound dressing 2100, which can alternatively be any wound dressing
embodiment disclosed herein including without limitation wound
dressing 110 or any combination of features of any number of wound
dressing embodiments disclosed herein, can be located over a wound
site to be treated. The dressing 2100 may be placed to as to form a
sealed cavity over the wound site. In a preferred embodiment, the
dressing 2100 comprises a backing layer 2140 attached to a wound
contact layer 2102, both of which are described in greater detail
below. These two layers 2140, 2102 are preferably joined or sealed
together so as to define an interior space or chamber. This
interior space or chamber may comprise additional structures that
may be adapted to distribute or transmit negative pressure, store
wound exudate and other fluids removed from the wound, and other
functions which will be explained in greater detail below. Examples
of such structures, described below, include a transmission layer
2105 and an absorbent layer 2110.
[0364] As illustrated in FIGS. 3A-C, a lower surface 2101 of the
wound dressing 2100 may be provided with an optional wound contact
layer 2102. The wound contact layer 2102 can be a polyurethane
layer or polyethylene layer or other flexible layer which is
perforated, for example via a hot pin process, laser ablation
process, ultrasound process or in some other way or otherwise made
permeable to liquid and gas. The wound contact layer 2102 has a
lower surface 2101 and an upper surface 2103. The perforations 2104
preferably comprise through holes in the wound contact layer 2102
which enable fluid to flow through the layer 2102. The wound
contact layer 2102 helps prevent tissue ingrowth into the other
material of the wound dressing. Preferably, the perforations are
small enough to meet this requirement while still allowing fluid to
flow therethrough. For example, perforations formed as slits or
holes having a size ranging from 0.025 mm to 1.2 mm are considered
small enough to help prevent tissue ingrowth into the wound
dressing while allowing wound exudate to flow into the dressing. In
some configurations, the wound contact layer 2102 may help maintain
the integrity of the entire dressing 2100 while also creating an
air tight seal around the absorbent pad in order to maintain
negative pressure at the wound.
[0365] Some embodiments of the wound contact layer 2102 may also
act as a carrier for an optional lower and upper adhesive layer
(not shown). For example, a lower pressure sensitive adhesive may
be provided on the lower surface 2101 of the wound dressing 2100
whilst an upper pressure sensitive adhesive layer may be provided
on the upper surface 2103 of the wound contact layer. The pressure
sensitive adhesive, which may be a silicone, hot melt, hydrocolloid
or acrylic based adhesive or other such adhesives, may be formed on
both sides or optionally on a selected one or none of the sides of
the wound contact layer. When a lower pressure sensitive adhesive
layer is utilized may be helpful to adhere the wound dressing 2100
to the skin around a wound site. In some embodiments, the wound
contact layer may comprise perforated polyurethane film. The lower
surface of the film may be provided with a silicone pressure
sensitive adhesive and the upper surface may be provided with an
acrylic pressure sensitive adhesive, which may help the dressing
maintain its integrity. In some embodiments, a polyurethane film
layer may be provided with an adhesive layer on both its upper
surface and lower surface, and all three layers may be perforated
together.
[0366] A layer 2105 of porous material can be located above the
wound contact layer 2102. This porous layer, or transmission layer,
2105 allows transmission of fluid including liquid and gas away
from a wound site into upper layers of the wound dressing. In
particular, the transmission layer 2105 preferably ensures that an
open air channel can be maintained to communicate negative pressure
over the wound area even when the absorbent layer has absorbed
substantial amounts of exudates. The layer 2105 should preferably
remain open under the typical pressures that will be applied during
negative pressure wound therapy as described above, so that the
whole wound site sees an equalized negative pressure. The layer
2105 may be formed of a material having a three dimensional
structure. For example, a knitted or woven spacer fabric (for
example Baltex 7970 weft knitted polyester) or a non-woven fabric
could be used.
[0367] A layer 2110 of absorbent material is provided above the
transmission layer 2105. The absorbent material, which comprise a
foam or non-woven natural or synthetic material, and which may
optionally comprise a super-absorbent material, forms a reservoir
for fluid, particularly liquid, removed from the wound site. In
some embodiments, the layer 2100 may also aid in drawing fluids
towards the backing layer 2140.
[0368] With reference to FIGS. 3A-C, a masking or obscuring layer
2107 can be positioned beneath at least a portion of the backing
layer 2140. In some embodiments, the obscuring layer 2107 can have
any of the same features, materials, or other details of any of the
other embodiments of the obscuring layers disclosed herein,
including but not limited to having any viewing windows or holes.
Additionally, the obscuring layer 2107 can be positioned adjacent
to the backing layer, or can be positioned adjacent to any other
dressing layer desired. In some embodiments, the obscuring layer
2107 can be adhered to or integrally formed with the backing layer.
Preferably, the obscuring layer 2107 is configured to have
approximately the same size and shape as the absorbent layer 2110
so as to overlay it. As such, in these embodiments the obscuring
layer 2107 will be of a smaller area than the backing layer
2140.
[0369] The material of the absorbent layer 2110 may also prevent
liquid collected in the wound dressing 2100 from flowing freely
within the dressing, and preferably acts so as to contain any
liquid collected within the absorbent layer 2110. The absorbent
layer 2110 also helps distribute fluid throughout the layer via a
wicking action so that fluid is drawn from the wound site and
stored throughout the absorbent layer. This helps prevent
agglomeration in areas of the absorbent layer. The capacity of the
absorbent material must be sufficient to manage the exudates flow
rate of a wound when negative pressure is applied. Since in use the
absorbent layer experiences negative pressures the material of the
absorbent layer is chosen to absorb liquid under such
circumstances. A number of materials exist that are able to absorb
liquid when under negative pressure, for example superabsorber
material. The absorbent layer 2110 may typically be manufactured
from ALLEVYN.TM. foam, Freudenberg 114-224-4 and/or
Chem-Posite.TM.11C-450. In some embodiments, the absorbent layer
2110 may comprise a composite comprising superabsorbent powder,
fibrous material such as cellulose, and bonding fibers. In a
preferred embodiment, the composite is an airlaid, thermally-bonded
composite.
[0370] An orifice 2145 is preferably provided in the backing layer
2140 to allow a negative pressure to be applied to the dressing
2100. A suction port 2150 is preferably attached or sealed to the
top of the backing layer 2140 over an orifice 2145 made into the
dressing 2100, and communicates negative pressure through the
orifice 2145. A length of tubing 2220 may be coupled at a first end
to the suction port 2150 and at a second end to a pump unit (not
shown) to allow fluids to be pumped out of the dressing. The port
may be adhered and sealed to the backing layer 2140 using an
adhesive such as an acrylic, cyanoacrylate, epoxy, UV curable or
hot melt adhesive. The port 2150 is formed from a soft polymer, for
example a polyethylene, a polyvinyl chloride, a silicone or
polyurethane having a hardness of 30 to 90 on the Shore A scale. In
some embodiments, the port 2150 may be made from a soft or
conformable material, for example using the embodiments described
below in FIGS. 3A-B.
[0371] Preferably the absorbent layer 2110 and the obscuring layer
2107 include at least one through hole 2146 located so as to
underlie the port 2150. The through hole 2146, while illustrated
here as being larger than the hole through the obscuring layer 2107
and backing layer 2140, may in some embodiments be bigger or
smaller than either. Of course, the respective holes through these
various layers 2107, 2140, and 2110 may be of different sizes with
respect to each other. As illustrated in FIGS. 3A-C a single
through hole can be used to produce an opening underlying the port
2150. It will be appreciated that multiple openings could
alternatively be utilized. Additionally should more than one port
be utilized according to certain embodiments of the present
disclosure one or multiple openings may be made in the absorbent
layer and the obscuring layer in registration with each respective
port. Although not essential to certain embodiments of the present
disclosure the use of through holes in the super-absorbent layer
may provide a fluid flow pathway which remains unblocked in
particular when the absorbent layer 2100 is near saturation.
[0372] The aperture or through-hole 2146 is preferably provided in
the absorbent layer 2110 and the obscuring layer 2107 beneath the
orifice 2145 such that the orifice is connected directly to the
transmission layer 2105. This allows the negative pressure applied
to the port 2153 to be communicated to the transmission layer 2105
without passing through the absorbent layer 2110. This ensures that
the negative pressure applied to the wound site is not inhibited by
the absorbent layer as it absorbs wound exudates. In other
embodiments, no aperture may be provided in the absorbent layer
2110 and/or the obscuring layer 2107, or alternatively a plurality
of apertures underlying the orifice 2145 may be provided.
[0373] The backing layer 2140 is preferably gas impermeable, but
moisture vapor permeable, and can extend across the width of the
wound dressing 2100. The backing layer 2140, which may for example
be a polyurethane film (for example, Elastollan SP9109) or
hydrocolloid film, having a pressure sensitive adhesive on one
side, is impermeable to gas and this layer thus operates to cover
the wound and to seal a wound cavity over which the wound dressing
is placed. In this way an effective chamber is made between the
backing layer 2140 and a wound site where a negative pressure can
be established. The backing layer 2140 is preferably sealed to the
wound contact layer 2102 in a border region 2200 around the
circumference of the dressing, ensuring that no air is drawn in
through the border area, for example via adhesive or welding
techniques. The backing layer 2140 protects the wound from external
bacterial contamination (bacterial barrier) and allows liquid from
wound exudates to be transferred through the layer and evaporated
from the film outer surface. The backing layer 2140 preferably
comprises two layers; a polyurethane or hydrocolloid film and an
adhesive pattern spread onto the film. The film is preferably
moisture vapor permeable and may be manufactured from a material
that has an increased water transmission rate when wet.
[0374] The absorbent layer 2110 may be of a greater area than the
transmission layer 2105, such that the absorbent layer overlaps the
edges of the transmission layer 2105, thereby ensuring that the
transmission layer does not contact the backing layer 2140. This
provides an outer channel 2115 of the absorbent layer 2110 that is
in direct contact with the wound contact layer 2102, which aids
more rapid absorption of exudates to the absorbent layer.
Furthermore, this outer channel 2115 ensures that no liquid is able
to pool around the circumference of the wound cavity, which may
otherwise seep through the seal around the perimeter of the
dressing leading to the formation of leaks.
[0375] As shown in FIG. 3A, one embodiment of the wound dressing
2100 comprises an aperture 2146 in the absorbent layer 2110
situated underneath the port 2150. In use, for example when
negative pressure is applied to the dressing 2100, a wound facing
portion of the port 150 may thus come into contact with the
transmission layer 2105, which can thus aid in transmitting
negative pressure to the wound site even when the absorbent layer
2110 is filled with wound fluids. Some embodiments may have the
backing layer 2140 be at least partly adhered to the transmission
layer 2105. In some embodiments, the aperture 2146 is at least 1-2
mm larger than the diameter of the wound facing portion of the port
2150, or the orifice 2145.
[0376] A filter element 2130 that is impermeable to liquids, but
permeable to gases is provided to act as a liquid barrier, and to
ensure that no liquids are able to escape from the wound dressing.
The filter element may also function as a bacterial barrier.
Typically the pore size is 0.2 .mu.m. Suitable materials for the
filter material of the filter element 2130 include 0.2 micron
Gore.TM. expanded PTFE from the MMT range, PALL Versapore.TM. 200R,
and Donaldson.TM. TX6628. Larger pore sizes can also be used but
these may require a secondary filter layer to ensure full bioburden
containment. As wound fluid contains lipids it is preferable,
though not essential, to use an oleophobic filter membrane for
example 1.0 micron MMT-332 prior to 0.2 micron MMT-323. This
prevents the lipids from blocking the hydrophobic filter. The
filter element can be attached or sealed to the port and/or the
backing layer 2140 over the orifice 2145. For example the filter
element 2130 may be molded into the port 2150, or may be adhered to
both the top of the backing layer 2140 and bottom of the port 2150
using an adhesive such as, but not limited to, a UV cured
adhesive.
[0377] In FIG. 3B, an embodiment of the wound dressing 2100 is
illustrated which comprises spacer elements 2152, 2153 in
conjunction with the port 2150 and the filter 2130. With the
addition of such spacer elements 2152, 2153, the port 2150 and
filter 2130 may be supported out of direct contact with the
absorbent layer 2110 and/or the transmission layer 2105. The
absorbent layer 2110 may also act as an additional spacer element
to keep the filter 2130 from contacting the transmission layer
2105. Accordingly, with such a configuration contact of the filter
2130 with the transmission layer 2105 and wound fluids during use
may thus be minimized. As contrasted with the embodiment
illustrated in FIG. 3A, the aperture 2146 through the absorbent
layer 2110 and the obscuring layer 2107 may not necessarily need to
be as large o-larger than the port 2150, and would thus only need
to be large enough such that an air path can be maintained from the
port to the transmission layer 2105 when the absorbent layer 2110
is saturated with wound fluids.
[0378] With reference now to FIG. 3C, which shares many of the
elements illustrated in FIGS. 3A-C, the embodiment illustrated here
comprises the backing layer 2140, masking layer 2107, and absorbent
layer 2110, all of which have a cut or opening made therethrough
which communicate directly to the transmission layer 2105 so as to
form the orifice 2145. The suction port 2150 is preferably situated
above it and communicates with the orifice 2145.
[0379] In particular for embodiments with a single port 2150 and
through hole, it may be preferable for the port 2150 and through
hole to be located in an off-center position as illustrated in
FIGS. 3A-C and in FIG. 1. Such a location may permit the dressing
2100 to be positioned onto a patient such that the port 2150 is
raised in relation to the remainder of the dressing 2100. So
positioned, the port 2150 and the filter 2130 may be less likely to
come into contact with wound fluids that could prematurely occlude
the filter 2130 so as to impair the transmission of negative
pressure to the wound site.
[0380] FIG. 4A illustrates an exploded view of a dressing 3400 for
use in negative pressure wound therapy. Although this figure
illustrates a dressing having one particular shape, the
construction of the layers can be applied to any of the embodiments
identified below, including FIGS. 5A-8, and any of the dressing
shapes and configurations described in the patent applications
incorporated by reference herein. The dressing 3400 comprises a
release layer 3480, wound contact layer 3460, a transmission layer
3450, an acquisition distribution layer 3440, an absorbent layer
3430, an obscuring layer 3420, and a backing layer 3410. The
dressing 3400 may be connected to a port. At least the wound
contact layer 3460, transmission layer 3450, absorbent layer 3430,
obscuring layer 3420, and backing layer 3410 may have properties as
described with respect to particular embodiments above, such as the
embodiments of FIGS. 3A-C, as well as or instead of the properties
described below.
[0381] The dressing 3400 may comprise a wound contact layer 3460
for sealing the dressing 3400 to the healthy skin of a patient
surrounding a wound area. Certain embodiments of the wound contact
layer may comprise three layers: a polyurethane film layer, a lower
adhesive layer and an upper adhesive layer. The upper adhesive
layer may assist in maintaining the integrity of the dressing 3400,
and the lower adhesive layer may be employed for sealing the
dressing 3400 to the healthy skin of a patient around a wound site.
As described above, in some embodiments with respect to FIGS. 3A-C,
some embodiments of the polyurethane film layer may be
perforated.
[0382] Some embodiments of the polyurethane film layer and upper
and lower adhesive layers may be perforated together after the
adhesive layers have been applied to the polyurethane film. In some
embodiments a pressure sensitive adhesive, which may be a silicone,
hot melt, hydrocolloid or acrylic based adhesive or other such
adhesives, may be formed on both sides or optionally on a selected
one side of the wound contact layer. In certain embodiments, the
upper adhesive layer may comprise an acrylic pressure sensitive
adhesive, and the lower adhesive layer may comprise a silicone
pressure sensitive adhesive. In other embodiments the wound contact
layer 3460 may not be provided with adhesive. In some embodiments,
the wound contact layer 3460 may be transparent or translucent. The
film layer of the wound contact layer 3460 may define a perimeter
with a rectangular or a square shape. A release layer 3480 may be
removably attached to the underside of the wound contact layer
3460, for example covering the lower adhesive layer, and may be
peeled off using flaps 3481. Some embodiments of the release layer
3480 may have a plurality of flaps extending along the length of
the layer 3480.
[0383] Some embodiments of the dressing 3400 may comprise a spacer
or transmission layer 3450. The transmission layer 3450 may
comprise a porous material or 3D fabric configured to allow for the
passage of fluids therethrough away from the wound site and into
the upper layers of the dressing 3400. In particular, the
transmission layer 3450 can ensure that an open air channel can be
maintained to communicate negative pressure over the wound area
even when the absorbent layer 3430 has absorbed substantial amounts
of exudates. The transmission layer 3450 should remain open under
the typical pressures that will be applied during negative pressure
wound therapy as described above, so that the whole wound site sees
an equalized negative pressure.
[0384] Some embodiments of the transmission layer 3450 may be
formed of a material having a three dimensional structure. For
example, a knitted or woven spacer fabric (for example Baltex 7970
weft knitted polyester) or a non-woven fabric can be used. In some
embodiments, the transmission layer 3450 can have a 3D polyester
spacer fabric layer. This layer can have a top layer which is a
84/144 textured polyester, and a bottom layer which can be a 100
denier flat polyester and a third layer formed sandwiched between
these two layers which is a region defined by a knitted polyester
viscose, cellulose or the like monofilament fiber. In use, this
differential between filament counts in the spaced apart layers
tends to draw liquid away from the wound bed and into a central
region of the dressing 3400 where the absorbent layer 3430 helps
lock the liquid away or itself wicks the liquid onwards towards the
cover layer 3410 where it can be transpired. Other materials can be
utilized, and examples of such materials are described in U.S.
Patent Pub. No. 2011/0282309, which are hereby incorporated by
reference and made part of this disclosure. However, the
transmission layer 3450 may be optional, and for example may be
optional in embodiments of the dressing 3400 which comprise the
acquisition distribution layer 3440, described below.
[0385] Some embodiments may comprise a wicking or acquisition
distribution layer (ADL) 3440 to horizontally wick fluid such as
wound exudate as it is absorbed upward through the layers of the
dressing 3400. Lateral wicking of fluid may allow maximum
distribution of the fluid through the absorbent layer 3430 and may
enable the absorbent layer 3430 to reach its full holding capacity.
This may advantageously increase moisture vapor permeation and
efficient delivery of negative pressure to the wound site. Some
embodiments of the ADL 3440 may comprise viscose, polyester,
polypropylene, cellulose, or a combination of some or all of these,
and the material may be needle-punched. Some embodiments of the ADL
3440 may comprise polyethylene in the range of 40-150 grams per
square meter (gsm).
[0386] The dressing 3400 may further comprise an absorbent or
superabsorbent layer 3430. The absorbent layer can be manufactured
from ALLEVYN.TM. foam, Freudenberg 114-224-4 and/or
Chem-Posite.TM.11C-450, or any other suitable material. In some
embodiments, the absorbent layer 3430 can be a layer of non-woven
cellulose fibers having super-absorbent material in the form of dry
particles dispersed throughout. Use of the cellulose fibers
introduces fast wicking elements which help quickly and evenly
distribute liquid taken up by the dressing. The juxtaposition of
multiple strand-like fibers leads to strong capillary action in the
fibrous pad which helps distribute liquid.
[0387] For example, some embodiments of the absorbent layer 3430
may comprise a layered construction of an upper layer of non-woven
cellulose fibers, superabsorbent particles (SAP), and a lower layer
of cellulose fibers with 40-80% SAP. In some embodiments, the
absorbent layer 3430 may be an air-laid material. Heat fusible
fibers can optionally be used to assist in holding the structure of
the pad together. Some embodiments may combine cellulose fibers and
air-laid materials, and may further comprise up to 60% SAP. Some
embodiments may comprise 60% SAP and 40% cellulose. Other
embodiments of the absorbent layer may comprise between 60% and 90%
(or between about 60% and about 90%) celluose matrix and between
10% and 40% (or between about 10% and about 40%) superabsorbent
particles. For example, the absorbent layer may have about 20%
superabsorbent material and about 80% cellulose fibers. It will be
appreciated that rather than using super-absorbing particles or in
addition to such use, super-absorbing fibers can be utilized
according to some embodiments of the present invention. An example
of a suitable material is the Product Chem-Posite.TM. 11 C
available from Emerging Technologies Inc (ETi) in the USA.
[0388] Super-absorber particles/fibers can be, for example, sodium
polyacrylate or carbomethoxycellulose materials or the like or any
material capable of absorbing many times its own weight in liquid.
In some embodiments, the material can absorb more than five times
its own weight of 0.9% WAN/W saline, etc. In some embodiments, the
material can absorb more than 15 times its own weight of 0.9% W/W
saline, etc. In some embodiments, the material is capable of
absorbing more than 20 times its own weight of 0.9% WAN/W saline,
etc. Preferably, the material is capable of absorbing more than 30
times its own weight of 0.9% W/WA saline, etc. The absorbent layer
3430 can have one or more through holes 3431 located so as to
underlie the suction port.
[0389] Some embodiments of the present disclosure may optionally
employ a masking or obscuring layer 3420 to help reduce the
unsightly appearance of a dressing 3400 during use due to the
absorption of wound exudate. The obscuring layer 3420 may be a
colored portion of the absorbent material, or may be a separate
layer that covers the absorbent material. The obscuring layer 3420
may be one of a variety of colors such as blue, orange, yellow,
green, or any color suitable for masking the presence of wound
exudate in the dressing 3400. For example, a blue obscuring layer
3420 may be a shade of blue similar to the shade of blue commonly
used for the material of medical gowns, scrubs, and drapes. Some
embodiments of the obscuring layer 3420 may comprise polypropylene
spunbond material. Further, some embodiments of the obscuring layer
3420 may comprise a hydrophobic additive or coating. Other
embodiments may comprise a thin fibrous sheet of 60, 70, or 80
gsm.
[0390] The obscuring layer may comprise at least one viewing window
3422 configured to allow a visual determination of the saturation
level of the absorbent layer. The at least one viewing window 3422
may comprise at least one aperture made through the obscuring
layer. The at least one viewing window 3422 may comprise at least
one uncolored region of the obscuring layer. Some embodiments of
the obscuring layer may comprise a plurality of viewing windows or
an array of viewing windows.
[0391] The masking capabilities of the obscuring layer 3420 should
preferably only be partial, to allow clinicians to access the
information they require by observing the spread of exudate across
the dressing surface. An obscuring layer 3420 may be partial due to
material properties allowing wound exudate to slightly alter the
appearance of the dressing or due to the presence of at least one
viewing window 3422 in a completely obscuring material. The partial
masking nature of the obscuring layer 3420 enables a skilled
clinician to perceive a different colour caused by exudate, blood,
by-products etc. in the dressing allowing for a visual assessment
and monitoring of the extent of spread across the dressing.
However, since the change in colour of the dressing from its clean
state to a state with exudate contained is only a slight change,
the patient is unlikely to notice any aesthetic difference.
Reducing or eliminating a visual indicator of wound exudate from a
patient is likely to have a positive effect on their health,
reducing stress for example.
[0392] The obscuring layer 3420 can have one or more through holes
located so as to underlie the suction port. Some embodiments may
have a maltese cross 3421 or other shaped cutout underlying the
suction port, wherein the diameter of the maltese cross 3421 is
greater than the diameter of the port. This may allow a clinician
to easily asses the amount of wound exudate absorbed into the
layers beneath the port.
[0393] The dressing 3400 may also comprise a backing layer, or
cover layer 3410 extending across the width of the wound dressing.
The cover layer 3410 may be gas impermeable but moisture vapor
permeable. Some embodiments may employ a polyurethane film (for
example, Elastollan SP9109) or any other suitable material. For
example, certain embodiments may comprise translucent or
transparent 30 gsm EU33 film. The cover layer 3410 may have a
pressure sensitive adhesive on the lower side, thereby creating a
substantially sealed enclosure over the wound in which negative
pressure may be established. The cover layer can protect the wound
as a bacterial barrier from external contamination, and may allow
liquid from wound exudates to be transferred through the layer and
evaporated from the film outer surface.
[0394] The cover layer 3410 can have an orifice 3411 located so as
to underlie the suction port. The orifice 3411 may allow
transmission of negative pressure through the cover layer 3410 to
the wound enclosure. The port may be adhered and sealed to the
cover film using an adhesive such as an acrylic, cyanoacrylate,
epoxy, UV curable or hot melt adhesive. Some embodiments may have a
plurality of orifices for the attachment of multiple ports or other
sources of negative pressure or other mechanisms for distributing
fluid.
[0395] FIG. 4B illustrates a cross sectional view of the wound
dressing 3400, displaying an embodiment of the relative thicknesses
of layers of the dressing 3400. In some embodiments, the wound
contact layer 3460 may be flat and the top film layer 3410 may be
contoured over the inner layers of the dressing 3400. The spacer
layer 3450 may be half as thick as the acquisition distribution
layer 3440 in some embodiments. In some embodiments, the absorbent
layer 3430 may be about 1.5 times thicker than the spacer layer
3450. The obscuring layer 3420 may be about half the thickness of
the spacer layer 3450.
[0396] FIG. 4C illustrates another embodiment of a wound dressing
3900, with the various layers illustrated in an exploded view.
Although this figure illustrates a dressing having one particular
shape, the construction of the layers can be applied to any of the
embodiments identified below, including FIG. 5A-FIG. 8, and any of
the dressing shapes and configurations described in the patent
applications incorporated by reference herein. The wound dressing
may comprise a release layer 3980, wound contact layer 3960, a
transmission layer 3950, an acquisition distribution layer 3940, an
adhesive layer 3970, an absorbent layer 3930, an obscuring layer
3920, and a backing layer 3910. At least the wound contact layer
3960, transmission layer 3950, absorbent layer 3930, obscuring
layer 3920, and backing layer 3910 may have properties as described
with respect to particular embodiments above, such as the
embodiments of FIGS. 3A-3C, as well as or instead of the properties
described below.
[0397] The dressing 3900 may be connected to a port 3990, as
illustrated in FIG. 4D (shown without the release layer 3980). At
least the backing layer 3910, obscuring layer 3920, absorbent layer
3930, and acquisition distribution layer 3940 may have openings
underlying the port 3990, and the port 3990 may comprise a
three-dimensional fabric 3997 and a filter element 3995 overlying
the openings. The absorbent layer 3930 may be configured to absorb
and retain exudate from a patient's wound. The absorbent layer 3930
will preferably be constructed from a material which has good
absorbent qualities under negative pressure. The adhesive layer
3970 may bond an upper surface of the acquisition distribution
layer 3940 to a lower surface of the absorbent layer 3930. In some
embodiments of a trimmable dressing 3900, other layers may be
bonded together to provide consistency with respect to layer
alignment when the dressing is cut on one or more sides, such that
the layers remain together when the sides of the dressing are cut,
and such that there is not vertical separation of the layers at the
cut portions.
[0398] FIGS. A1-A4 illustrate trimming a TNP dressing in various
manners. In FIG. A1, the cut line is a simple truncation of the
dressing, exposing the internal transmission layer; In FIG. A2, a
hole has been cut to receive a fixation device or digit; in FIG.
A3, the dressing has been cut to allow profiling to a curved body
portion; in FIG. A4 the dressing has been articulated to dress a
moving joint such as a knee, and in this case, transmission layer
has been cut away but an amount of border region 2200 has been
retained to assist in retaining and sealing the dressing at its
edge.
[0399] FIGS. A5-A6 illustrate applying the trimmed dressings and
dispensing sealant at the exposed transmission layer portions by
means of syringe A. In FIG. A7. sealant is dispensed via syringe A
to a puncture B in the backing layer 2140.
[0400] FIG. B1 illustrates in detail the means of dispensing
sealant by syringe A. The syringe in this case has a nozzle
aperture which allows sealant to be dispensed within the structure
of the transmission layer, in FIG. B2 a suitable relationship of
transmission layer height or thickness and syringe nozzle cross
section and aperture is shown.
[0401] FIGS. C1-C3 illustrate different modes of dispensing sealant
C: C1--internally to the transmission layer 2105, as was shown in
FIG. B1; C2 and C2a--bridging the exposed portion of transmission
layer 2105 and skin surrounding a wound 200; and C3--bridging the
exposed portion of transmission layer 2105 and retention strips
laid down on skin surrounding a wound, before the dressing has been
applied. Dressings are shown comprising backing layer or sheet and
transmission layer, being spacer layer, at the exposed portion
2105. The dressing may comprise further layer(s) (not shown) as
hereinbefore defined at the exposed portion 2105. The main dressing
portion or module of the dressing pad may contain further layers
(e.g. an absorbent layer above the transmission layer) not shown.
FIG. C1 shows one embodiment of sealing and mode of dispensing of
composition C. In this embodiment syringe A such as a static mixer
is located such that the nozzle penetrates within the exposed
portion 2105. The syringe A nozzle is of cross-section area suited
to be received within the exposed portion 2105 of transmission
layer. Composition C is dispensed internally to the exposed portion
2105. Syringe A nozzle is inserted to penetrate a short distance
within the exposed portion 2105, at intervals along the exposed
face, whereby composition C is dispensed internally as a seal
within the exposed portion 2105. Composition may flow to some
extent on initial application, either or both laterally to the
direction of dispensing and advancing and receding, flow becoming
less as composition hardens or cures. This may aid in providing a
continuous lateral seal, whereby dispensing intervals along the
face of exposed portion 2105 may be increased. Nozzle insertion
distance within the exposed portion 2105 may be selected to confine
the seal spaced a short distance in from the face of the exposed
portion, or to allow some spill of composition C out of the exposed
portion and onto surrounding surfaces such as a preparation plate
or skin 200.
[0402] Advantages of this embodiment include minimizing the amount
of composition C required to be dispensed. This in turn allows use
of a lower capacity syringe or static mixer A. The back pressure
encountered on dispensing from a static mixer increases with the
mixer volume, which in turn leads to a decrease in the viscosity
which the syringe or mixer A is able to dispense. It is generally
advantageous to this embodiment to deliver composition C at as high
a viscosity as possible to ensure that composition C is confined
within the exposed portion 2105. A further element in the total
back pressure or resistance encountered on dispensing composition C
is the nozzle aperture of syringe A. For this embodiment, it is
desired to dispense composition C from a small aperture nozzle, and
this adds to the back pressure. The advantage that this embodiment
delivers of enabling a relatively small volume syringe or mixer A
to be employed, allows greater freedom to operate a small aperture
nozzle.
[0403] Finally we have found that a seal generated by dispensing
composition C internally to the exposed portion 2105, according to
this embodiment, is highly effective. The dressing should be
trimmed, as hereinbefore described, such that the exposed portion
overlies intact skin about a wound, and does not overly the wound
itself. In the case of a dressing having an adhesive or tacky wound
contact layer, such as a silicone contact layer as hereinbefore
described, the wound contact layer adheres to the skin 200 about
the wound and seals the dressing to skin 200 about the exposed
portion 2105 and the dispensed seal C. The wound contact layer is
perforated or otherwise porous to allow transmission of fluids to
and from the wound bed, and this may permit flow of composition C
onto skin directly proximal to the internal seal. This may
beneficially enhance the seal between the wound contact layer and
skin 200. In the event that flow of composition to skin 200
directly proximal to the internal seal is not desired, composition
C suitably has a sufficiently high viscosity to restrict flow,
alternatively the wound contact layer may be non-porous or
non-permeable in the region proximal to an envisaged exposed
portion, for example at a bridging portion or trimmable portion as
hereinbefore defined.
[0404] FIG. B1 may be considered, for one purpose, to illustrate
dispensing composition C to a dressing having an obscuring layer
whereby the dispensed seal is obscured. In contrast, the dispensed
seal is shown beneath the backing layer or sheet in FIG. C1. This
illustrates that dispensing composition C to a dressing having no
obscuring layer, or having window(s) in obscuring layer at bridging
portions or trimmable portion(s) allows visual control of nozzle
insertion distance within the exposed portion 2105, of composition
C volume dispensed, and of lateral flow enabling a suitable
dispensing interval across the face of exposed portion 2105 to be
determined. In the case that no obscuring layer is present it is
preferred that the composition incorporates ADL as hereinbefore
defined as transmission layer, rather than spacer layer which may
pose a risk of penetrating the backing sheet. Figure C2a shows an
extension of FIG. C2 showing the sealant on the top film. Parts are
referred to using the same reference numbering as in FIG. C2. We
have found that an advantageous feature of a further embodiment of
sealing and mode of dispensing is that the composition C is
dispensed to the backing layer or backing sheet adjacent the
exposed portion 2105, whereby composition C flows across the
exposed portion 2105 totally covering the exposed portion 2105. In
some cases composition C flows a short distance into or is drawn a
short distance within the exposed portion 2105. It may be desired
to dispense or smooth composition C onto the perimeter of the
exposed portion 2105 adjoining border region 2200 as shown in FIG.
C2a, and even directed slightly back along the perimeter (not
shown). This has the advantage of advancing composition C a short
distance at the perimeter of the exposed portion 2105, ensuring a
total seal C and also securing the seal C in place. As composition
C hardens or cures, the viscosity typically increases and flow
ceases whereby composition C is retained at or in the dispensing
location 2105 and forms an effective seal C.
[0405] This further embodiment places performance requirements on
the composition C and the resulting seal, additional to those of
the first embodiment of sealing and mode of dispensing.
Specifically composition C requires a continuous film to be
dispensed and formed across the surface of the backing layer or
sheet bridging onto the exposed portion of any additional layers
and the exposed portion 2105 of the transmission layer and bridging
onto the skin surface 200. Therefore composition C must be
sufficiently viscous and/or cohesive to form an intact film. Such
film may be thin or, as illustrated in FIG. C2, C2a and C3 may be
of appreciable depth and/or thickness of for example from the order
of depth and/or thickness of the backing sheet to the order of
depth and/or thickness of the dressing or of the component layers
at the exposed portion 2105 thereof. Should such film rupture or
fail prior to setting or curing of composition C then the seal will
fail. After setting or curing of an intact film, the exposed nature
of the seal and its presentation as a film place additional
requirements of robustness, both to external influences and also,
to its ability to retain integrity across interfaces between
adjacent layers. These requirements are likely to be greater in the
case of a thin film. Preferably therefore a seal according to this
further embodiment is characterized by properties of tensile
strength, permanent set, and elongation at break, optionally also
extensibility, in ranges as hereinbefore defined. In contrast a
seal generated according to the first embodiment, as illustrated in
FIG. C1 above, is supported in large part by the fabric of the
dressing enclosing the seal C, whereby requirements of tensile
strength, permanent set, elongation at break, are significantly
lower, also being enclosed within the lower extensibility dressing,
the requirement for extensibility is significantly lower than for
the further embodiment of FIGS. C2 and C3.
[0406] FIGS. C2a illustrates the need for the seal of this
embodiment to be effective from the backing layer surface across
the exposed portion 2105. As will be apparent, a seal across the
exposed portion alone is susceptible to failure at the interface of
the backing sheet and exposed portion and any intervening
layers.
[0407] The further embodiment illustrated by FIGS. C2 to C3 is
likely to be more effective when adopted in relation to a dressing
comprising no additional layers as hereinbefore defined, thereby
better resisting strains introduced by separation at the interface
of additional layer(s) and transmission layer. Additional layer(s)
if present may beneficially be secured at their interfaces with
each other and with transmission layer, by needling, stitching and
other means as known in the art.
[0408] The further embodiment of FIGS. 2 and 3 moreover requires
that a seal C have low profile and/or compressibility greater than
or equal to the surrounding dressing. This is of advantage in
minimizing discomfort to the wearer imposed by a protruding ridge
at the exposed portion 2105 of the dressing.
[0409] In FIGS. C4 and C5 syringe A is illustrated dispensing
composition C to exposed portion 2105 of transmission layer in
dressing, having border region 2200. In FIG. C6 syringe A is
illustrated with modest nozzle head spread for dispensing
composition C to profiled exposed portion 2105 of transmission
layer. In FIG. C7 syringe A nozzle head is illustrated having
combined spreader tip with plural nozzles, conformable to dispense
to a profiled exposed portion and/or to dispense with obstructed
access to exposed portion. In FIG. C8, an imaginary cone
illustrates maximum dispenser A dimensions to allow a shallow entry
angle to exposed portion 2105 relative to the skin 200.
[0410] FIGS. C4 and C5 illustrate dispensing composition C
according to the first embodiment of sealing and mode of dispensing
of composition C, of FIG. C1, using a syringe or static mixer A
having a combination of spreader tip with plural nozzles as
hereinbefore defined (spreader having plural projecting apertures).
Parts are referred to using the same reference numbering as in FIG.
C1. A dispenser (A) is illustrated having a nozzle head comprising
5 nozzles with small nozzle cross section to deliver sealant to the
interior portion within the exposed portion 2105 of transmission
layer. The spread of the nozzle head matches the width of the
bridging portion shown enabling dispensing on a single insertion.
FIG. C4 illustrates internally dispensing composition C to the
interior portion of the exposed portion 2105 of a bridging portion
in the context of a relatively larger dressing. The main dressing
portion or module of the dressing pad may contain further layers
(e.g. an absorbent layer above the transmission layer) not shown.
FIG. C5 may for example illustrate dispensing to the interior
portion of the exposed portion 2105 of a bridging portion in the
context of any shape or configuration dressing as hereinbefore
defined. This embodiment of dispenser for and mode of dispensing
composition benefits from a decreased burden and decreased
requirement for accuracy on the part of the operator, an increase
in mechanical accuracy of dispensing location and continuous seal
formation. It may also slightly reduce the back-pressure at the
syringe allowing the use of higher viscosity composition. A
substantial border region 2200 is illustrated, which contributes to
seal integrity.
[0411] FIG. C6 illustrates a multi nozzle head syringe A where the
overall width or spread of the head is kept modest so as to allow
dispensing into exposed portion 2105 of a transmission layer on a
curve, e.g. a body contour.
[0412] FIG. C7 illustrates an alternative multi nozzle head
dispenser A that is flexible or deformable in two locations
facilitating dispensing into exposed portion 2105 of a transmission
layer on a curve, e.g. a body contour and/or dispensing into a
location 2105 having obstructed access. There is a flexible arm or
restraint (shown in grey) with four nozzles emerging out of the
arm. This is joined to the main body (with integral static mixer)
via four flexible tubes (also shown in grey).
[0413] The end on view illustrates the nozzle ends and flexible arm
showing how the arm may be bent to conform to an arc. The tubes may
similarly be bent (not shown) to conform to generate an angled
nozzle, beneficially increasing the entry angle for dispensing.
[0414] The flexible arm is typically not elastic, i.e. it retains
the shape conferred for dispensing until bent to return to its
original shape or a different conformation. The flexible arm could
be formed of a deformable polymer or putty or the like or it could
be a mechanical flexible or deformable arm (i.e.
http://snakeclamp.com/or http://joby.com/gorillapod).
[0415] FIG. C8 illustrates an imaginary cone containing the
dispenser A. This shows the maximum dimensions that may
advantageously be considered in the design of the dispenser A to
allow a shallow entry angle relative to the skin 200, to allow a
nozzle to be inserted into an exposed portion 2105 of transmission
layer in a dressing adhered to a patient 200.
[0416] FIGS. 5A and 5B illustrate various embodiments of a wound
dressing 500 which may be trimmable at a bridge portion 530. The
dressing 500 may comprise a backing layer 510, an absorbent layer
and/or transmission layer formed in a main portion 520 and at least
one additional portion 540 separated by a gap 560 and connected by
a bridge portion 530, and a port 550. In some embodiments, the main
portion 520, additional portion 540 and bridge portion 530 comprise
at least a transmission layer such as described above between an
optional wound contact layer and a backing layer 510. In any or all
of these sections, the dressing 500 may further comprise an
optional absorbent material such as described positioned between
the backing layer 510 and the transmission layer. In some
embodiments, the absorbent layer may have a similar footprint to
the transmission layer. In other embodiments, the absorbent layer
may be located at main portion 520 and at least one additional
portion 540, but the absorbent layer may not be included in the
bridge portion 530. As illustrated, the dressing has an elongate,
rectangular shape, though other shapes are also contemplated. The
absorbent layer preferably has a smaller footprint than the backing
layer, so that the absorbent layer is completely surrounded by the
backing layer. It will be appreciated that in some embodiments, the
absorbent layer is an integral, one-piece layer of material that
extends across the main portion 520, the additional portion 540 and
in the bridge portion 530. Some embodiments may be manufactured
without the port 550 and may include at least one area for
attaching a port. For example, the port 550 may simply be an
opening in the backing layer for attaching a separate port
member.
[0417] The dressing 500 may also comprise other layers as discussed
above with respect to FIGS. 3A-4B. For instance, the dressing 500
may comprise a wound contact layer which may be sealed to the
backing layer 510, thereby creating an enclosed chamber for the
absorbent layer and/or transmission layer and any other layers
within the dressing. The wound contact layer and backing layer may
be sealed along a perimeter with a certain distance from the edge
of the sealed perimeter to the edge of the absorbent layer. The
wound contact layer and backing layer may also be sealed together
throughout some or all of the area of a gap 560 between portions of
the inner layers.
[0418] The transmission or wicking layer, as described above, may
be provided for the transmission of negative pressure throughout
the dressing and for drawing wound exudate away from the wound site
and into the upper layers of the dressing 500. Some embodiments of
the transmission layer may comprise the acquisition distribution
layer, as described above with respect to FIG. 4A, for lateral
transmission of fluids such as wound exudate. Some embodiments may
employ both a wicking layer and an acquisition distribution layer.
Use of one or more of these layers may advantageously maintain
fluid transmission through narrow portions of the dressing such as
the bridge portions, and may keep these narrow portions from
partially or completely collapsing under negative pressure.
[0419] As illustrated in FIG. 5B, the absorbent layer and/or
transmission layer may comprise a main portion 520 and a plurality
of additional portions 540. The additional portions may be smaller
than or the same size as the main portion 550. For example, as
measured along the longitudinal length of a rectangular dressing,
the length of the additional portions may be smaller than the
length of the main portion, and each additional portion may have
the same length. As illustrated, the main portion 520 is connected
to the first additional portion 540 by one bridge portion 530
aligned along the center longitudinal axis of the dressing 500, and
each additional portion is connected to the next additional portion
by a similar bridge. The bridge portion may in FIGS. 5A and 5B may
also be located off the center axis, for example at the side of the
dressing. Other embodiments may employ a plurality of bridges for
connecting the portions of the dressing. For example, one
embodiment may employ two bridges to connect adjacent portions,
wherein the bridges are located at the side edges of the adjacent
portions next to the sealed perimeter. Another embodiment may
employ two bridges each located a distance away from the side edges
of the adjacent portions.
[0420] In some embodiments the main portion 520 may be a
precalculated minimum length, and some or all of the additional
portions 540 may have lengths that can be removed for custom sizing
of the dressing to a variety of lengths exceeding the minimum
length. The main portion length may be longer than the additional
portion lengths, or the main portion may have the same length as
the additional portions. Such embodiments may be advantageous for a
long incision such as a leg incision made for a vein harvest. In an
embodiment, the main portion 520 may be a minimum incision length
or minimum leg length, and the additional portions 540 may be
included in the dressing to achieve a length up to a maximum
incision length or a maximum leg length. In use, the dressing may
be trimmed according to the incision or leg length of the patient
across the bridge portions, for example at cut line 570 described
below. In some embodiments, additional ports or port attachment
sites may be located on some or all of the additional portions in
order to maintain a substantially even level of negative pressure
throughout a relatively long dressing.
[0421] The bridge portion 530 in FIGS. 5A and 5B creates a
continuous path for negative pressure delivery between multiple
portions of the dressing. The bridge portion 530 may have a width
that is less than 1/8, 1/4, or 1/3 the width of adjacent portions
of absorbent material and/or transmission layer. A wider bridge
portion allows for greater transmission of negative pressure and
fluids such as wound exudate, however a narrower bridge portion is
advantageous for sealing a dressing trimmed at the bridge portion.
Further, patient comfort may be enhanced if the bridge portion 530
is wide enough to cover a wound or an incision. Embodiments of the
dressings described herein may balance these factors according to a
variety of purposes and/or considerations, and therefore the width
of bridge portion 530 may vary. In some embodiments the bridge
portion 530 may be approximately 15 mm wide, however other
embodiments may be 10 mm to 20 mm (or about 10 mm to about 20 mm)
wide or thinner or thicker. In embodiments employing a plurality of
bridge portions, the bridge portions may all be a uniform width or
may have varying widths. In some embodiments, the bridge portion
530 may comprise a wound contact layer, a transmission layer (which
may be one or both of the wicking layer or acquisition distribution
layers described above with respect to FIG. 4A), and a backing
layer. Some embodiments of the bridge portion 530 may further
comprise an absorbent: or superabsorbent layer. The layers in the
bridge portions 530 may be continuous with layers found in the
portions 520 or 540 of the dressing, or they may be discrete layers
positioned side-by-side.
[0422] In a dressing applied to a nonplanar surface, the bridge
portions may also advantageously provide enhanced flexing of the
dressing for conforming to the nonplanar surface. Further, the
bridge portions may enhance side flexing capabilities of the
dressing for covering a curved or arcuate incision. In some
embodiments, the location and width of the bridge portions may be
selected for both connecting a plurality of trimmable portions as
well as for flexibility of the dressing.
[0423] The dressing 500 may be trimmed at or across the bridge
portion 530. Although the dressing may be trimmed at any portion,
trimming the dressing at bridge portion 530, for example
perpendicular to the length of the dressing, enables easier sealing
as a narrower cross sectional area is exposed, and thus less area
requires sealing after trimming. In some embodiments, the gap 560
may have the same width as the distance from the sealed perimeter
edge to the absorbent layer, such that when the dressing is trimmed
along a trim line 570 adjacent to the additional portion 540 the
sealed perimeter around the inner layer(s) is substantially
unchanged. In some embodiments this width may be approximately 2.5
cm, and in other embodiments may be any width suitable for
maintaining the seal between the backing layer and the wound
contact layer. It will be appreciated that the dressing may be
trimmed at locations other than the illustrated trim line 570,
which is included for illustrative purposes only, for example at a
trim line in the center of the bridge portion 530 or at a diagonal
or curved trim line.
[0424] In some embodiments, the absorbent layer and/or other layers
of the wound dressing may be prescored for sizing. Other layers,
such as the transmission layer or acquisition distribution layer,
may also be prescored. The backing layer may not be scored, as a
through hole may limit the ability of the backing layer to function
as a bacterial barrier or compromise the ability of the dressing to
maintain negative pressure. Other embodiments may include a printed
or indented pattern on some or all of the layers to indicate
possible trim lines.
[0425] After trimming, the dressing 500 may be sealed by an
adhesive strip, a piece of a sealing drape, by another dressing, or
by a sealant. In some embodiments, a retention strip may be applied
at the interface of the dressing edge and the skin. The retention
strips may be applied to cover trimmed dressing borders. In some
embodiments the retention strips may comprise a pressure-sensitive
adhesive on the lower surface, and in other embodiments may be
applied over a sealant. It will be appreciated that any other
adhesive method or mechanism may be used to seal the dressing. For
example, a sealant may be applied with a tool such as a syringe
around the trimmed area in order to reseal the chamber of the
dressing or to seal the dressing to a patient. Some embodiments of
the dressing may be self-sealing.
[0426] FIGS. 5C and 5D illustrate removing a portion of dressing
from the dressings of FIGS. 5A and 5C thereby exposing a bridging
portion of transmission layer 2105 which can be sealed before or
after applying the dressing to a wound site, by means of sealant C
dispensed from syringe A. In the case of FIG. 5C, the dressing may
simply be suited to a particular ulcer size, whilst in the case of
FIG. 5D, the dressing is admirably suited to dressing a vein
harvest wound running the length of a subject's leg.
[0427] FIG. 6 illustrates an embodiment of a trimmable wound
dressing 600 comprising a plurality of portions or cells 620. The
dressing 600 may comprise a sealed perimeter 610 of a backing layer
and a wound contact layer, a plurality of cells 620, a plurality of
bridges 630 connecting adjacent portions, and a port member 640. As
described above, the dressing 600 may be trimmed at the bridge
portions and sealed along the trim line. Each of the cells 620 may
include absorbent material and/or a transmission layer as described
above, along with other optional layers. The bridge portions 630
may comprise a wound contact layer, a transmission layer (which may
be one or both of the wicking layer or acquisition distribution
layers described above with respect to FIG. 4A), and a backing
layer. Some embodiments of the bridge portions 630 may further
comprise an absorbent or superabsorbent layer. The layers in the
bridge portions 630 may be continuous with layers found in the
cells 620, or they may be discrete layers positioned
side-by-side.
[0428] As illustrated, the dressing comprises a 4.times.4 array of
cells 620. Other embodiments may comprise any suitable array of
cells, or may be configured as a long rolled dressing N cells wide.
The cells may be connected by one or more narrow bridge portions
630 and separated by gaps 650. The backing layer and wound contact
layer may be sealed together throughout the gaps. By trimming at
the bridge portions 630, the integrity of the dressing may be
maintained even as the dressing is significantly resized. For
example, the dressing may be trimmed so that only one inner cell or
a group of inner cells remain, and the layers of the dressing will
not separate due to the sealing of the backing layer and wound
contact layer throughout the area of the gaps 650.
[0429] In some embodiments, the center cells of the dressing 600
may be removed. This may provide benefits, for example, when the
dressing is used to cover a grafted skin flap or sutured skin flap.
The dressing may be resized so that the unsutured skin is
substantially uncovered by the dressing. Thus, the removed sections
would otherwise cover the healthy skin of the flap. Covering the
healthy skin with the dressing potentially creates problem such as
exposing the wound to bacteria on the surface of the flap and
exposing the healthy skin of the flap to excess moisture. The
dressing may also be resized accordingly to cover circular, curved,
or otherwise irregularly shaped suture lines.
[0430] The port member 640 may be located, as illustrated, on a
corner cell of the dressing 600. However, in other embodiments the
port may be located on a different cell. Some embodiments may
employ multiple ports, each port connected to a different cell. For
example, a large dressing or longed rolled dressing may comprise a
port at an edge cell of every N rows, such every as four rows or
five rows. Some embodiments may, instead of the illustrated port
member 640, comprise a port attachment site or sites.
[0431] FIG. 6II illustrates removing a portion of dressing from the
dressing of FIG. 6 thereby exposing multiple bridging portions of
transmission layer which can be sealed before or after applying the
dressing to a wound site, by means of sealant C dispensed from
syringe A. It can clearly be seen that the use of bridging portions
dramatically reduces the cross-sectional area of transmission layer
that must be sealed, reducing thereby both dressing time and risk
of leaks.
[0432] FIG. 7 illustrates an embodiment of a trimmable wound
dressing 700 comprising a plurality of portions with multiple port
attachment sites 760. Similar to the dressing 600 described above,
the T-shaped dressing 700 comprises a backing layer and wound
contact layer having a sealed perimeter 710 around a plurality of
cells 720 containing absorbent material and/or a transmission layer
connected by bridge portions 730 and separated by gaps 740. The
bridge portions 730 may comprise a wound contact layer, a
transmission layer (which may be one or both of the wicking layer
or acquisition distribution layers described above with respect to
FIG. 4A), and a backing layer. Some embodiments of the bridge
portions 730 may further comprise an absorbent or superabsorbent
layer. The layers in the bridge portions 730 may be continuous with
layers found in the cells 720, or they may be discrete layers
positioned side-by-side. The backing layer and wound contact layer
may also be sealed together throughout some or all of the area of
the gaps 740. As described above, the dressing 700 may be trimmed
at the bridge portions and sealed along the trim line. Although the
dressing is illustrated as being T-shaped, this is for illustrative
purposes only, and the dressing may be a variety of branched
shapes. Each branch may comprise one or more cells connected by one
or more bridge portions.
[0433] The dressing comprises a plurality of port attachment sites
760. Each attachment site 760 may be a hole in the backing layer
and may be covered with a removable tab 760. The tab may comprise a
suitable backing material with a layer of adhesive on some or all
of the lower surface. Some embodiments may comprise a ring of
adhesive sized to surround the hole 750 in the backing layer. The
tab 760 may be removed so that a port may be attached to the
backing layer over the hole 750 for transmission of negative
pressure into the dressing 700. In some embodiments, port
attachments may be secured at just one port attachment site. In
other embodiments, port attachments may be secured over a plurality
of attachment sites as needed for transmission of negative pressure
throughout the dressing. Some ports may comprise an adhesive on the
lower surface thereof for attachment to the dressing. Some
embodiments of the dressing may comprise an adhesive layer for
attaching the port.
[0434] FIG. 7II illustrates removing a portion of dressing from the
dressing of FIG. 7 thereby exposing a bridging portion of
transmission layer which can be sealed before or after applying the
dressing to a wound site, by means of sealant C dispensed from
syringe A. It car clearly be seen that this form of trimmable
dressing is suitable for difficult to dress wounds which may
require some visual inspection and comparison with dressing
configurations, for example in the case of a flap wound.
[0435] FIG. 8 illustrates an embodiment of a trimmable wound
dressing 800 with multiple port attachment sites 840. The dressing
comprises a backing layer and wound contact layer having a sealed
perimeter 710, an absorbent layer 820, a spacer layer 830 below the
absorbent layer, and a plurality of holes 840 in the backing layer
covered by tabs 850. The spacer layer 830 may be one or both of the
transmission layer and acquisition distribution layer discussed
above. It will be appreciated that in some embodiments, only one of
the absorbent layer or spacer layer may be provided, with the other
layer being optional.
[0436] The dressing 800 is configured as a roll with port
attachment sites 840 spaced a distance apart along the upper
surface. In some embodiments this distance may be uniform between
all port attachment sites, and in other embodiments the distance
may vary. The dressing roll may be custom sized by unrolling a
length of dressing, trimming the dressing, sealing the two sides,
and attaching a port or ports to one or more port attachment sites.
In some embodiments, unused port attachment sites 840 may remain
sealed by adhesive tabs 850. In some embodiments, the spacer layer
830, and optionally the absorbent layer 820, may comprise a bridge
portion or plurality of bridge portions located between each port
attachment site for ease of sealing a trimmed dressing. It will be
appreciated that any of the dressings described above may be
configured as a trimmable roll with a plurality of port attachment
sites located a distance apart on the roll. For example, an
elongate dressing configured as a roll may include narrower
bridging portions spaced along a length of the dressing between
port attachment sites to facilitate trimming of the dressing to a
suitable size.
[0437] FIG. 8II illustrates removing a portion of dressing from the
dressing of FIG. 8 thereby exposing multiple bridging portions of
transmission layer which can be sealed before or after applying the
dressing to a wound site, by means of sealant C dispensed from
syringe A.
[0438] Such adaptable, resizable dressings may provide the
advantage of reducing the inventory of dressings that a hospital or
clinic is required to keep. Rather than maintaining a large
inventory of dressings consisting of a multitude of shapes and
sizes for all possible wound or incision sites, a hospital or
clinic may only require one or several of the dressings described
herein which can be modified to suit any patient needs. Further, it
may be advantageous from a manufacturing perspective to produce
adaptable dressings.
Overview of Example Layer Materials
[0439] FIGS. 9A and 9B illustrate one embodiment of spacer layer,
or transmission layer, material which may be used in any of the
dressing embodiments described above, and which may also be used in
any of the port or fluidic connector embodiments described above.
The spacer or transmission material is preferably formed of a
material having a three dimensional structure, and may have a top
layer and a bottom layer comprising a knit pattern. For example, a
knitted or woven spacer fabric (for example Baltex 7970 weft
knitted polyester) or a non-woven fabric could be used. The top and
bottom fabric layers may comprise polyester, such as 84/144
textured polyester or a flat denier polyester. Other materials and
other linear mass densities of fiber could of course be used. In
some embodiments, the top and bottom fabric layers may be the same
pattern and the same material, and in other embodiments they may be
different patterns and/or different materials. The top fabric layer
may have more filaments in a yarn used to form it than the number
of filaments making up the yarn used to form the bottom fabric
layer, in order to control moisture flow across the transmission
layer. Particularly, by having a filament count greater in the top
layer, that is to say, the top layer is made from a yarn having
more filaments than the yarn used in the bottom layer, liquid tends
to be wicked along the top layer more than the bottom layer. FIG.
9A illustrates one possible knit pattern for a top or bottom fabric
layer.
[0440] As illustrated in the side view of FIG. 9B, between the top
and bottom fabric layers may be a plurality of filaments. The
filaments may comprise a monofilament fiber or a multistrand fiber,
and may be knitted polyester viscose or cellulose. In some
embodiments, a majority of the filaments, by volume, may extend
vertically (that is, perpendicular to the plane of the top and
bottom layers), or substantially or generally vertically. In
another embodiment, 80%-90% (or approximately 80% to approximately
90%) of the filaments or more, by volume, may extend vertically, or
substantially or generally vertically. In another embodiment, all
or substantially all of the filaments, by volume, may extend
vertically, or substantially or generally vertically. In some
embodiments, a majority, 80%-90% (or approximately 80% to
approximately 90%) of the filaments or more, or even all or
substantially all of the filaments, extend upward from the bottom
fabric layer and/or downward from the top fabric layer, and in some
embodiments, such filaments extend over a length more than half the
distance between the top and bottom fabric layers. In some
embodiments, a majority, 80%-90% (or approximately 80% to
approximately 90%) of the filaments or more, or even all or
substantially all of the filaments, span a distance that is greater
in a direction perpendicular to the top and bottom fabric layers (a
vertical direction) than in a direction parallel to the top and
bottom fabric layers (a horizontal direction). The orientation of
such filaments may promote vertical wicking of fluid through the
spacer layer. In some embodiments, the ratio of the amount of fluid
wicked vertically through the spacer material to the amount of
fluid wicked laterally across the spacer material when under
negative pressure may be 2:1 or more, or approximately 2:1 or more,
or may be up to 10:1 or more, or approximately 10:1 or more, in
some embodiments. Such filaments may also keep the top and bottom
layers spaced apart when exposed to compressive forces or negative
pressure. Some embodiments of the spacer layer may have a tensile
strength that substantially prevents tearing by typical force
applied by human hands, and accordingly would need to be severed by
other means, such as being cut or sliced, if implemented in a
trimmable dressing.
[0441] FIGS. 10A-10D illustrate one embodiment of acquisition
distribution layer (ADL) material which may be used in any of the
dressing embodiments described above, and which may also be used in
any of the port or fluidic connector embodiments described above.
To those versed in the art of acquisition distribution layers it
would be obvious that other ADL materials may be used to achieve a
similar effect.
[0442] FIG. 10A illustrates a backscatter scanning electron
microscope (SEM) plan view of a sample portion of acquisition
distribution layer material at 140.times. magnification. FIG. 10B
illustrates an SEM cross sectional view at 250.times.
magnification. As illustrated in FIG. 10B, a majority of the fiber
volume may extend horizontally (that is, parallel to the plane of
the top and bottom surfaces of the material), or substantially or
generally horizontally. In another embodiment, 80%-90% (or
approximately 80% to approximately 90%) or more of the fiber volume
may extend horizontally, or substantially or generally
horizontally. In another embodiment, all or substantially all of
the fiber volume may extend horizontally, or substantially or
generally horizontally. In some embodiments, a majority, 80%-90%
(or approximately 80% to approximately 90%) of the fibers or more,
or even all or substantially all of the fibers, span a distance
perpendicular to the thickness of the ADL material (a horizontal or
lateral distance) that is greater than the thickness of the ADL
material. In some embodiments, the horizontal or lateral distance
spanned by such fibers is 2 times (or about 2 times) or more, 3
times (or about 3 times) or more, 4 times (or about 4 times) or
more, 5 times (or about 5 times) or more, or 10 times (or about 10
times) or more the thickness of the ADL material. The orientation
of such fibers may promote lateral wicking of fluid through the ADL
material. This may more evenly distribute fluid such as wound
exudate throughout the ADL material. In some embodiments, the ratio
of the amount of fluid wicked laterally across the ADL material to
the amount of fluid wicked vertically through the ADL material
under negative pressure may be 2:1 or more, or approximately 2:1 or
more, or may be up to 10:1 or more, or approximately 10:1 or more,
in some embodiments.
[0443] FIG. 10C is a two dimensional microtomographic cross
sectional view of a compressed portion of a sample of ADL material
which is approximately 9.2 mm long. FIG. 10D is an SEM cross
sectional view at 130.times. magnification of the compressed
portion illustrated in FIG. 10C. Such compressed portions may occur
in the ADL material may occur due to the application of pressure to
the material. FIGS. 10C and 10D further illustrate the horizontal
network of ADL fibers.
[0444] FIGS. 11A and 11B illustrate one embodiment of absorbent
material which may be used in any of the dressing embodiments
described above. FIG. 11A illustrates a three dimensional
microtomographic cross sectional view of a sample of absorbent
material, depicting a fibrous composition interspersed with
superabsorbent particles. The absorbent material may, for example,
be any of the materials described in U.S. Patent Pub. No.
2012/308780, titled "Absorbent Structure," filed May 25, 2012, the
contents of which are hereby incorporated by reference in their
entirety.
[0445] FIG. 11B is a cross sectional schematic diagram of an
embodiment of the absorbent material illustrating a plurality of
layers within the absorbent material. The absorbent material may
have a textured layer 4210 on one side of a fibrous network, the
fibrous network defining the bulk of the absorbent material and
comprising layers 4220, 4240, and 4250. Superabsorbent particles
4230 may be dispersed throughout layers 4220, 4240, and 4250. The
textured layer 4210, also referred to as the "tissue dispersant
layer" in above portions of this specification, may be configured
to laterally transmit fluid. Though depicted as the lowermost layer
of the absorbent material, the textured layer 4210 may in some
embodiments be positioned as the uppermost layer of the absorbent
material, and in some embodiments may be positioned as both the
lowermost and uppermost layers of the absorbent material. The
textured layer 4210 may comprise flat fibers 20 .mu.m to 50 .mu.m
in width, or approximately 20 .mu.m to approximately 50 .mu.m in
width. The textured layer 4210 may comprise 1 to 2 or approximately
1 to approximately 2 layers of the flat fibers, and the textured
layer 4210 may have an overall thickness of 0.04 mm, or
approximately 0.04 mm.
[0446] The bulk of the absorbent material, comprising layers 4220,
4240, and 4250, may have a thickness of 1.7 mm, or approximately
1.7 mm, or may have a thickness in the range of 0.5 mm to 5.0 mm,
or about 0.5 mm to about 5.0 mm. The bulk of the absorbent material
may comprise a mix of two fiber types arranged in a fibrous
network, for example the cellulosic fiber having a width of 20
.mu.m to 50 .mu.m, or approximately 20 .mu.m to approximately 50
.mu.m, and the PE/PET composite fiber, described above with respect
to the ADL material. The superabsorbent particles 4230 may be
irregularly shaped and varied in size, and may have a diameter of
up to 1 mm, or approximately 1 mm. The superabsorbent particles
4230 may comprise a sodium acrylate type material. There may be
relatively fewer superabsorbent particles in a portion of the
uppermost surface of the bulk of the absorbent material (the
surface of layer 4250 opposite the textured layer 4210), for
example in an uppermost surface having a thickness of approximately
0.1 mm.
[0447] Layer 4220 may be a liquid absorption layer configured to
draw liquid upward through the material towards layers 4240 and
4250. Layer 4240 may be a storage layer configured to hold absorbed
liquid. Layer 4220 may be a liquid distribution layer configured to
apply a "reverse suction" effect to the liquid storage layer 4240
in order to inhibit (or substantially inhibit) absorbed liquid from
leaking back down through the lower layers of the absorbent
material, a phenomenon which is commonly known as "back
wetting."
[0448] Superabsorbent particles 4230 may be distributed primarily
within the storage layer, may extend partially into the absorption
layer 4220 and liquid distribution layer 4250, or may be
distributed evenly (or substantially evenly) throughout the layers.
The layers 4220, 4240, and 4250 may overlap with a portion of
adjacent layers, and may or may not be separable.
[0449] FIGS. 12A and 12B illustrate one embodiment of obscuring
layer material which may be used in any of the dressing embodiments
described above. FIG. 12A illustrates a photographic plan view of
obscuring material, depicting a material comprising a fibrous
network having a reoccurring regularly spaced criss-cross diamond
pattern. The diamond shaped pattern may, in one embodiment, be 1.2
mm long by 1.0 mm wide, and may have a thickness of approximately
0.04 mm thick, consisting of fibers that are more densely packed
relative to the surrounding area of the material. The diamond
shaped pattern may increase structural stability of the fibrous
network of the material, for example serving as "tacking" points.
FIG. 12B illustrates a three dimensional microtomographic
perspective view of the compressed diamond pattern and the
surrounding uncompressed fibers.
[0450] Some embodiments of the obscuring material may comprise
polypropylene spunbond material. Further, some embodiments of the
obscuring material may comprise a hydrophobic additive or coating,
for example a hydrophobic wash designed to permeate the fibers of
the obscuring material to make the material substantially
waterproof while permitting vapor permeability. Other embodiments
may comprise a thin fibrous sheet of 60, 70, or 80 gsm. The fibers
of the obscuring material may, in one embodiment, comprise layers
of polypropylene (PP) fibers having a smooth surface morphology,
and the PP fibers may have a thickness of approximately 25 .mu.m.
In some embodiments, the obscuring material may have a thickness of
0.045 mm or about 0.045 mm, or may have a thickness in the range of
0.02 mm to 0.5 mm, or about 0.02 mm to about 0.5 mm.
[0451] FIG. 13 illustrates one embodiment of an adhesive spread on
approximately one square centimeter of a film material, which may
be used as the cover or backing layer in any of the dressing
embodiments or fluidic connector embodiments described above. The
adhesive on the film has been covered with carbon powder for ease
of illustrating the spread of the adhesive. The adhesive may
comprise, for example, an acrylate type adhesive, for example K5
adhesive, and may be laid down in a criss cross pattern. In some
embodiments, the adhesive material may cover approximately
45.5%.+-.approximately 1.3% of the film surface. The pattern and
coverage of the adhesive may vary so long as the configuration is
suitable for desired vapor permeability.
I. Overview of Additional Bridged Dressing Embodiments
[0452] FIG. 14A (previously FIG. 17A) illustrates a plan view of a
trimmable dressing 1600 embodiment wherein the number of layers
present in the bridging portions 1620 of the dressing is less than
in an absorbent pad portion 1630 or a secondary absorbent portion
1650 of the dressing. FIG. 14B (previously FIG. 17B) illustrates a
side view of the dressing 1600. Accordingly, the overall height of
the dressing is reduced at the bridging portions 1620 relative to
the absorbent pad portions. In some embodiments, the dressing can
also reduce in width at the bridging portions relative to the
absorbent pad portions. The dressing 1600 also includes a port 1640
for delivery of negative pressure.
[0453] The dressing 1600 includes a spacer layer 1662 in the
absorbent pad portion 1630 and secondary absorbent portions 1650.
An ADL 1664 extends across the length of the dressing through the
absorbent pad portion 1630, secondary absorbent portions 1650, and
bridging portions 1620. The ADL 1664 satisfies the testing criteria
specified above and is capable of negative pressure transmission
through the bridging portions 1620. In some implementations of the
trimmable dressing 1600, the ADL 1664 may be constructed from an
ADL material that is easier to cut than a spacer material, and may
be accordingly selected for the bridging portions 1620. In other
embodiments, the spacer layer 1662 may extend across the length of
the dressing in addition to or instead of the ADL 1664.
[0454] In the absorbent pad portion 1630 and secondary absorbent
portions 1650, the dressing 1600 includes an absorbent layer 1666
and masking layer 1668. In some embodiments, the masking layer 1668
may extend across the bridging portions 1620, and may include
holes, windows, perforations, or other visual indicators for
indicating to a user where to cut the dressing. For example,
perforations may be arranged in a dashed or dotted line
configuration along a location within a bridging portion 1620,
revealing a contrasting color of the ADL 1664 beneath the masking
layer 1668 to visually indicate a potential location for trimming
the dressing 1600. This approach could be extended to include
designs and symbology such as the symbol of a pair of scissors
and/or a dotted line, or notches/chevron on each side of the
masking layer, lettering indicating a "cut here" location, or the
like. The interior layers 1662, 1664, 1666, 1668 are positioned
between a wound contact layer 1672 and a top film layer 1674 that
are sealed together around a perimeter 1610, for example a
perimeter of approximately 2.5 cm in some embodiments.
[0455] This layer arrangement can provide the advantage of
increased flexibility at the bridging points during wear of the
dressing, easy cutting with scissors (or other means) during
fitting and shaping of the dressing to a wound site, and easier
sealing of cut portions. The reduced height of the bridging
portions provides a smaller gap that needs to be sealed. Cut or
trimmed portions can be sealed with a sealant, a sealing strip, a
flexible adhesive drape, or other sealing means. In addition, use
of different top layers in the absorbent pad portions compared to
the bridging portions can result in a color coded dressing, making
the cutting locations clear to the user. Such a dressing can be
convenient for use along long incision wounds where the length
varies from patient to patient, for example incisions resulting
from abdominoplasty procedures, as the dressing can be trimmed
according to specific patient needs.
[0456] Referring now to FIG. 15 (formerly FIG. 21), another
embodiment of a trimmable dressing 2100 is illustrated. The
dressing may comprise, from bottom to top, an optional wound
contact layer (not shown), a transmission layer and/or ADL over the
wound contact layer, a plurality of absorbent cells over the
transmission layer and/or, and a cover layer over the plurality of
absorbent cells. As illustrated in FIG. 15, one embodiment of the
dressing includes a border 2105, a generally rectangular
transmission layer 2110, a number of absorbent cells 2115, a port
2120, and a conduit 2125 for connection of the dressing 2100 to a
source of negative pressure. The border 2105 can include a cover
layer as described above sealed to the healthy skin of a patient
surrounding a wound in one example, or can include a cover layer
sealed to a wound contact layer as described above. This cover
layer may extend over the plurality of absorbent cells 2115. The
port 2120 and conduit 2125 can be configured for transmitting
negative pressure to the dressing 2100 from a source of negative
pressure when in use.
[0457] The transmission layer 2110 can extend across the entire
central pad area, and can be any material described herein, or the
equivalent, having suitable permeability to gas and liquid at a
minimum height and/or width. By having the transmission layer 2110
extend across the central pad area rather than only being placed in
bridging areas, a more comfortable distribution of pressure over
the patient's therapy site can be achieved. Such pressure
distribution can be considered both from the point of view of NPWT
delivery and from the point of view of protecting friable skin,
where (depending on the design of the dressing) blistering can be
caused at pad edges. Therefore, a continuous transmission layer
can, in some embodiments, minimize the number of pad edges (i.e.
using a continuous lower layer) providing an advantage for pressure
distribution.
[0458] A number of absorbent cells 2115 can be included above the
transmission layer 2110, and can be any of the absorbent materials
described herein, for example with respect to FIGS. 3A-4D and
11A-11B. By cutting the dressing 2100 along the areas of
transmission layer 2110 between adjacent cells 2115, the dressing
2100 can be adaptively sized to correspond to the shape of a
patient's wound. The dressing 2100 can be sealed along cut portions
by one or more of re-sealing of the cover layer and wound contact
layer, through a sealant adhesive, and sealing strips in various
embodiments.
[0459] Although the absorbent cells 2115 are illustrated as being
triangular in shape, other variations can include circular, oval,
square, rectangular, hexagonal, or other shaped cells. Further,
although the absorbent cells 2115 are illustrated as being discrete
portions of absorbent material, in other embodiments the absorbent
cells 2115 can be connected by bridging portions.
II. Overview of Additional Layer Materials
[0460] FIGS. 16A and 16B (formerly 22A and 22E) illustrate an
example of Libeltex DryWeb T28F that can be suitable for use as
acquisition distribution layer material (ADL) material which may be
used in any of the dressing embodiments described above, and which
may also be used in any of the port or fluidic connector
embodiments described above. To those versed in the art of
acquisition distribution layers, also known as "surge layers," it
would be obvious that other ADL materials may be used to achieve a
similar effect of laterally wicking fluid. Suitable ADL materials
can allow for full capacity use. Such ADL layers may be composed of
multiple fiber types and be complex in structure and design.
[0461] FIG. 16A illustrates a backscatter scanning electron
microscope (SEM) plan view of a sample portion of ADL material at
70.times. magnification. As illustrated by FIG. 16A, the ADL
material can comprise a number of non-woven fibers extending at
least partially horizontally (that is, parallel to the plane of the
top and bottom surfaces of the material) for laterally/horizontally
wicking fluid through the ADL material.
[0462] FIG. 16B illustrates an SEM cross sectional view of the ADL
material at 1550.times. magnification. In the illustrated
embodiment, the ADL material may consist of a mix of multiple fiber
types. One may be a roughly cylindrical fiber. Another fiber may be
a relatively flatter fiber having a centrally-located negative
space. Another fiber may be a multi-component fiber that has at
least one inner core fiber, in some embodiments three inner core
fibers as in the illustrated sample, and an outer layer surrounding
the inner core.
[0463] FIG. 17A (formerly 23A) 17B (23B) and 17C (formerly 23D)
illustrate an example of Libeltex SlimCore TL4 that can be suitable
for use as acquisition distribution layer material. FIG. 17A
illustrates an SEM cross sectional view of a sample portion of ADL
material at 50.times. magnification. The ADL material can include
an upper layer 2305 and a lower layer 2310 having different
densities, lofts, and thicknesses. For example, the upper layer
2305 can comprise a more dense, less lofted fiber configuration and
can be approximately 730 .mu.m thick in some embodiments. The lower
layer 2310 can comprise a less dense, more lofted fiber
configuration and can be approximately 1200 .mu.m thick in some
embodiments. FIG. 17B illustrates an SEM plan view of a sample
portion of the denser upper layer 2305 at 70.times. magnification,
FIG. 17C illustrates an SEM plan view of a sample portion of the
more lofted lower layer 2310 at 70.times. magnification. As
illustrated by FIGS. 17A-17C, the upper and lower layers 2305, 2310
of the ADL material can comprise different densities of a number of
non-woven fibers extending at least partially horizontally (that
is, parallel to the plane of the top and bottom surfaces of the
material) for laterally/horizontally wicking fluid through the ADL
material.
[0464] As illustrated by FIGS. 17A-17C, the non-woven fibers of the
various illustrated ADL materials can extend more in a horizontal
direction than in a vertical direction to aid in lateral wicking of
fluids through the material. In some embodiments, a majority of the
fiber volume may extend horizontally or substantially or generally
horizontally. In another embodiment, 80%-90% (or approximately 80%
to approximately 90%) or more of the fiber volume may extend
horizontally, or substantially or generally horizontally. In
another embodiment, all or substantially all of the fiber volume
may extend horizontally, or substantially or generally
horizontally. In some embodiments, a majority, 80%-90% (or
approximately 80% to approximately 90%) of the fibers or more, or
even all or substantially all of the fibers, span a distance
perpendicular to the thickness of the ADL material (a horizontal or
lateral distance) that is greater than the thickness of the ADL
material. In some embodiments, the horizontal or lateral distance
spanned by such fibers is 2 times (or about 2 times) or more, 3
times (or about 3 times) or more, 4 times (or about 4 times) or
more, 5 times (or about 5 times) or more, or 10 times (or about 10
times) or more the thickness of the ADL material. The orientation
of such fibers may promote lateral wicking of fluid through the ADL
material. This may more evenly distribute fluid such as wound
exudate throughout the ADL material. In some embodiments, the ratio
of the amount of fluid wicked laterally across the ADL material to
the amount of fluid wicked vertically through the ADL material
under negative pressure may be 2:1 or more, or approximately 2:1 or
more, or may be up to 10:1 or more, or approximately 10:1 or more,
in some embodiments.
[0465] Features, materials, characteristics, or groups described in
conjunction with a particular aspect, embodiment, or example are to
be understood to be applicable to any other aspect, embodiment or
example described herein unless incompatible therewith. All of the
features disclosed in this specification (including any
accompanying claims, abstract and drawings), and/or all of the
steps of any method or process so disclosed, may be combined in any
combination, except combinations where at least some of such
features and/or steps are mutually exclusive. The protection is not
restricted to the details of any foregoing embodiments. The
protection extends to any novel one, or any novel combination, of
the features disclosed in this specification (including any
accompanying claims, abstract and drawings), or to any novel one,
or any novel combination, of the steps of any method or process so
disclosed.
[0466] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of protection. Indeed, the novel
methods and systems described herein may be embodied in a variety
of other forms. Furthermore, various omissions, substitutions and
changes in the form of the methods and systems described herein may
be made. Those skilled in the art will appreciate that in some
embodiments, the actual steps taken in the processes illustrated
and/or disclosed may differ from those shown in the figures.
Depending on the embodiment, certain of the steps described above
may be removed, others may be added. Furthermore, the features and
attributes of the specific embodiments disclosed above may be
combined in different ways to form additional embodiments, all of
which fall within the scope of the present disclosure.
[0467] Although the present disclosure includes certain
embodiments, examples and applications, it will be understood by
those skilled in the art that the present disclosure extends beyond
the specifically disclosed embodiments to other alternative
embodiments and/or uses and obvious modifications and equivalents
thereof, including embodiments which do not provide all of the
features and advantages set forth herein. Accordingly, the scope of
the present disclosure is not intended to be limited by the
specific disclosures of preferred embodiments herein, and may be
defined by claims as presented herein or as presented in the
future.
[0468] Throughout the description and claims of this specification,
the words "comprise" and "contain" and variations of them mean
"including but not limited to", and they are not intended to (and
do not) exclude other moieties, additives, components, integers or
steps. Throughout the description and claims of this specification,
the singular encompasses the plural unless the context otherwise
requires. In particular, where the indefinite article is used, the
specification is to be understood as contemplating plurality as
well as singularity, unless the context requires otherwise.
[0469] Features, integers, characteristics, compounds, chemical
moieties or groups described in conjunction with a particular
aspect, embodiment or example are to be understood to be applicable
to any other aspect, embodiment or example described herein unless
incompatible therewith. All of the features disclosed in this
specification (including any accompanying claims, abstract and
drawings), and/or all of the steps of any method or process so
disclosed, may be combined in any combination, except combinations
where at least some of such features and/or steps are mutually
exclusive. Details of any foregoing embodiments should not be
considered to be limiting unless expressly indicated as such.
Embodiments may relate to any novel one, or any novel combination,
of the features disclosed in this specification (including any
accompanying claims, abstract and drawings), or to any novel one,
or any novel combination, of the steps of any method or process so
disclosed.
[0470] Herein either a full stop or comma is used as the decimal
marker.
[0471] The reader's attention is directed to all papers and
documents which are filed concurrently with or previous to this
specification in connection with this application and which are
open to public inspection with this specification, and the contents
of all such papers and documents are incorporated herein by
reference.
EXAMPLES
[0472] The following Examples are given as non-limiting
illustration.
Compositions Commercially available RTV-2 Si compositions having 2
Parts incorporating i), ii) and iii) as defined above, literature
values of physical properties are publicly available: 1
Cavi-Care.TM. (20 g), Part A and Part B polymers product code 4563
(Smith & Nephew). This is a commercially available open cell
foaming in situ dressing. Guide cure time within 2 minutes 2
Mepiseal.TM. (3 ml), Part A and Part B polymers ref. 283100
(Molnlycke) This is a commercially available dispensable adhesive
sealant intended to seal wound exudates within a wound area from
contacting intact skin. Guide cure time within 20 minutes 3
Elastosil SC870 Part A and B polymers. This is a commercially
available foaming elastomer, black in colour. Guide cure time
within 90 minutes. (pot life 150 s, tack free time 10-15 min,
density 0.35-0.4, Shore hardness 8-12) 4 Silpuran.RTM. 2445 A/B
Part A and B polymers Ref 60063054 and 60063056 (both Wacker Chemie
AG). This is a commercially available elastomer for casting as
alignment, shock, damping members etc in prosthetics. Guide cure
time within 25 minutes 5 Silpuran 2400118 A/B (Wacker) is an
addition-curing RTV-2 silicone rubber curing to a blue coloured
silicone of low hardness. It has application in flexible moulding
applications for prosthetics. Guide cure time 120.degree. C. for 1
hour. 6 Silpuran 2111 A/B (Wacker) is a commercially available
2-part, addition-curing silicone composition curing to a soft,
tacky silicone adhesive. It is suitable for use in wound dressings.
Guide cure time 120.degree. C. for 1 hour. 7 Elastosil SC835 Part A
and B polymers. This is a commercially available foaming elastomer,
reddish brown in colour. Guide cure time within 90 minutes (pot
life 240 s, tack free time 10-15 min, density 0.4-0.45, Shore
hardness 20); 8 Silbione RTV 4511 A/B (Bluestar)--this commercially
available composition is modified to reduce cure time and
temperature for application at or around a wound site. 9 Silbione
LSR 4301 A/B (Bluestar)--this commercially available liquid
silicone rubber composition would not be preferred for application
at or around a wound site.
Procedure A
[0473] A TNP dressing (PICO.TM. 15.times.20 cm) similar (unwaisted)
to that illustrated in FIG. 1 was adhered to an acrylic or glass
plate or aluminium plate, adhesive side down, and connected to a
pump to establish a negative pressure, as illustrated in FIGS. 2B
and 2C. Once it was established that a good seal had formed, the
pump was turned off and the end portion of the dressing opposite to
the pump end was removed by slicing, as shown in FIG. A1. Removing
the dressing portion exposed the transmission layer and other
internal layers as shown in FIGS. 3A-3C.
[0474] Sealant composition was loaded into the cylinders of a
static mixer and dispensed therefrom to coat the exposed edge of
the dressing as in FIG. CII, but with considerable overlap of both
the top surface of the dressing adjacent the exposed edge, and the
plate. After 90 minutes the pump was turned on again to determine
whether a good seal had formed.
Example 1
CaviCare Applied to Dressing Edge
[0475] Procedure A followed as above, applying dressing to acrylic
plate. The composition was dispensed, and cured within 2 minutes.
In this application, the sealed dressing leaked through the open
cells of the foam, although we have observed that the nature of the
foam structure of this composition causes it to perform differently
under different conditions for example an external load may cause
cell collapse with resulting gas impermeability the composition
could well be optimised to achieve cell closure. Dispensing was
acceptable.
Example 2
Elastosil Applied to Dressing Edge
[0476] Procedure A followed as above, applying dressing to acrylic,
glass and aluminium plates. Adhesion was better with glass than
acrylic and better with aluminium than glass. The composition wads
dispensed and cured and after 90 minutes the pump was turned on.
Leak was significant for sealed trimmed dressing on acrylic plate
and low level requiring intermittent pump activity, when sealed to
glass and aluminium plates. This was a factor of adhesion to the
plate, not the dressing to which adhesion was acceptable. Cured
sealant was difficult to remove from acrylic and glass substrates,
less so from aluminum.
Example 3
Silpuran 2445 Applied to Dressing Edge
[0477] Procedure A followed as above, applying dressing to glass
plate. The composition was dispensed and left to cure overnight.
The sealed dressing performed well, with very good seal
established, hardly requiring the pump to come on once a negative
pressure had been established within the sealed trimmed dressing
initially.
Procedure B
[0478] Procedure followed as for A above, applying to glass plate,
but with injection of composition directly into exposed
transmission (spacer) layer as illustrated in FIGS. EI, BII and
CI.
Example 4
CaviCare Injected Directly into Exposed Transmission Layer
[0479] Procedure B was followed. The composition did not appear to
penetrate the dressing, and seemed to be blocked by the dense
superabsorbent polymer (SAP) layer. On starting the pump, a very
poor seal was observed, with continual pump activity unable to
achieve required vacuum.
Example 5
Mepiseal Injected Directly into Exposed Transmission Layer
[0480] Result as for Example 4.
Example 6a
Elastosil SC 870 Injected Directly into Exposed Transmission Layer,
SAP Removed
[0481] Composition was observed to penetrate approx 1 cm within the
transmission layer. On foaming and cure the backing layer top
surface was observed to lift a little. Good seal, although edge of
dressing lifted where composition was present in too great
quantity.
Example 6b
Silpuran 2445 Injected Directly into Exposed Transmission Layer,
SAP Removed
[0482] As Example 6, no dressing lift, good seal and vacuum
established instantly.
Example 7
Mepiseal Injected Directly into Exposed Transmission Layer, SAP
Removed
[0483] As Example 6b, no dressing lift.
Example 8
CaviCare Injected Directly into Exposed transmission Layer, SAP
Removed
[0484] As Example 6b, but penetration was 1.5-2 cm due to foaming
action, no dressing lift. No vacuum due to open cell structure.
CONCLUSION
[0485] Gas impermeable curable sealant dispensed externally to
cover and/or internally to impregnate exposed transmission layer
was surprisingly effective. Seal was absolute, and both modes were
visually effective.
[0486] Further samples.
Example 9
[0487] Procedure a as above was conducted on samples as
follows:
9.1
Ostomy Paste
[0488] Paste block was worked to render supple and pasted to the
dressing edge. Seal was robust. Disadvantages included bioburden
risk due to working before application, seal height exceeds
dressing height.
9.2
Adhesive Gel Strip
[0489] Strip is tacky at both faces, one face applied to dressing
gave good seal; disadvantage of tacky exposed surface, seal
degraded over a few days as strip lost its tack;
9.3
Shaving Gel
[0490] The non-foaming gel was of low viscosity, such that a
substantial amount of gel was pulled into the transmission layer,
the dressing stopped delivering negative pressure, due to the
aqueous component of the gel filling up the superabsorber
layer.
9.4
Germolene
[0491] The cream was of low viscosity, such that an was pulled into
the transmission layer, the seal collapsed and negative pressure
leakage occurred,
9.5
Savlon Spray
[0492] The spray works by forming a liquid film on skin, water
evaporates off to leave the polymer medication. In this example,
the spray was unable to generate a film which could bridge the
interface between absorber and transmission layer to skin. Two
discrete films formed one at the backing layer surface and one at
the wound model representing skin. There was no seal formed.
9.6
Elastosil SC835 (Wacker)
[0493] A foam seal of appreciable height was formed at the exposed
portion, some composition was drawn in to the transmission layer,
to a depth of 1-2 mm. The seal adhered strongly to the wound model
and seemed robust.
9.7
Elastosil SC870 (Wacker)
[0494] A foam seal of appreciable height was formed at the exposed
portion, comparable to 9.6. This composition was however more
viscous to apply and the resulting seal offers lesser resilience
than SC835.
Composition Measurements
[0495] Methods were used as described in WO2013076450, the contents
of which are incorporated herein by reference.
Example 10.1
Viscosity Measurement
[0496] Viscosity is a measure of the resistance of a fluid to
deformation by shear or tensile stress and gives an indication of
the fluidity of a liquid, suspension or slurry. The viscosity of a
sample is measured using a rotational viscometer which
simultaneously measures shear rate and shear stress. Vaseline.RTM.
original, Moisturizing shaving gel Nivea Men Originals and
Germolene, antiseptic cream were independently tested on a cone and
plate rheometer, using a 2.degree. steel cone of diameter 60 mm.
The samples were tested across a shear rate range of 5-15 s.sup.-1,
at 20.degree. C. in accordance with DIN EN ISO 3219: 1994, Annex B.
The viscosity is calculated using the shear stress at a shear rate
of 10 s.sup.-1 and is given in Pas.
TABLE-US-00002 TABLE viscosity Results Mean Viscosity at shear rate
of 10/s, T 23.degree. C. (Pa s) Cavi-Care Part A 1.643 1.653 1.648
Cavi-Care Part B 1.773 1.804 1.7885 Mepiseal part from 42.30 41.97
42.135 chamber with Text Mepiseal part from 34.19 36.10 35.145
chamber without Text Silpuran 2450A 79.40 76.32 77.86 Silpuran
2450B 25.20 24.39 24.795 Silpuran 2445A 26.07 20.39 23.23 Silpuran
2445B 11.81 12.01 11.91 Silpuran 2400 1.8 Elastosil 835 Part A 15
Elastosil 835 Part B 15 Elastosil 870 Part A 50 Elastosil 870 Part
B 35 Viscosity at shear rate of 10 s.sup.-1, T 20.degree. C. (Pa s)
Vaseline .RTM. original, 23.84 pure petroleum jelly, Unilever
Moisturising shaving 11.93 gel, Nivea Men, Originals, Beiersdorf
Germolene, antiseptic 14.12 cream (Phenol and Chlorhexidine
Digluconate), Bayer plc
Example 10.2
Compressibilty Measurements
[0497] Compressibility was determined as a measure of penetration
by a plunger. Using a Setamatic Penetrometer with automatic
release, timing device and standard 47.5 g plunger. The instrument
was fitted with a hollow plastic cone with a stainless steel tip of
mass 15 g. A dwell time of 60 seconds was used.*Measurements were
recorded in triplicate (n=3).
TABLE-US-00003 Relative mass of parts A B Mean penetration/1/10 mm
Silpuran 2400/18 50.0% 50.0% 51 (SD 1) A/B* Silpuran 2111 A/B 50.0%
50.0% 200 (SD 3)
[0498] Subject to the desired performance requirements of the
system these values can be considered acceptable.
Example 10.3
Extensibility, Permanent Set, Tensile Strength, Elongation at
Break
TABLE-US-00004 [0499] Extensibility (kgfcm.sup.-2) Results Mean
Cavi-Care 0.04 0.06 0.04 0.07 0.07 0.06 Mepiseal 0.07 0.06 0.09
0.07 0.08 0.07 Silpuran 2450 2.60 2.41 2.42 2.25 2.70 2.48 Silpuran
2445 1.20 1.39 1.32 1.39 1.60 1.38
TABLE-US-00005 Permanent Set (%) Results Mean Cavi-Care 0 0 0 0 0 0
Mepiseal 0 0 0 0 0 0 Silpuran 2450 0 0 0 0 0 0 Silpuran 2445 0 0 0
0 0 0
TABLE-US-00006 Tensile Strength (kgfcm.sup.-2) Results Mean
Cavi-Care 0.24 0.27 0.26 0.24 0.29 0.26 Mepiseal 1.64 0.95 1.77
1.69 2.00 1.61 Silpuran 2450 47.64 47.64 55.85 44.37 -- 48.87
Silpuran 2445 37.74 39.73 39.98 41.16 37.15 39.15 Elastosil 835 450
Elastosil 870 350
TABLE-US-00007 Elongation at Break (%) Results Mean Cavi-Care 92 90
83 73 120 92 Mepiseal 425 283 463 450 466 418 Silpuran 2450 199 204
234 184 -- 205 Silpuran 2445 322 332 334 342 302 326 Elastosil SC
870 100 Elastosil SC835 80
Example 11
Extensibility Testing of Spacer Layer (Transmission Layer)
Baltex
TABLE-US-00008 [0500] Reference Description A Spacer Layer B
Laminates made with EU33 top film, Chemposite 11C-450 Air Laid
superabsorber pad, Baltex ref: 7970, batch number T0061Spacer layer
and ALLEVYN Gentle Border wound contact layer (non-sterile and hand
manufactured)
Method
SOP/QPM/230 (1003423) Extensibility
Results
TABLE-US-00009 [0501] A Test method Results(kgfcm.sup.-1) Mean
Extensibility (Direction A) 0.07 0.08 0.08 0.08 1003423
Extensibility (Direction B) 0.07 0.08 0.07 0.07 1003423
TABLE-US-00010 B Test method Results(kgfcm.sup.-1) Mean
Extensibility (Direction A) 0.58 0.61 0.59 0.59 1003423
Extensibility (Direction B) 0.79 0.80 0.76 0.78 1003423
Conclusions
[0502] The spacer layer gave good (ie low) extensibility values.
Extensibility was restricted once the material was incorporated
into a dressing with the superabsorber pad.
Example 12
Silpuran 2400
[0503] Silpuran was subject to testing according to procedures A
and B above. The results are shown as follows. This composition has
a very long cure time and low viscosity and it was expected that it
would simply run out of position before curing. In fact the
composition demonstrated a surprisingly effective seal, however
showed a dramatic performance difference depending on dispensing
according to presence or absence of the absorber layer in Procedure
B. The composition gave excellent results when dispensed according
to Procedure B.
[0504] Silpuran 2400 was then dispensed internally according to the
first embodiment procedure illustrated in FIG. C1. The composition
was retained admirably in the transmission layer, and only a small
volume of composition was required. This enables use of a small
volume syringe with associated back-pressure advantages. It was
important to use a small bore nozzle to minimize run off, allowing
as little composition as possible to contact skin. Dispensing again
was ineffective using the Procedure A method with superabsorber
layer, but was highly effective for Procedure B with single
transmission layer in the trimmed portion. The transmission layer
may be spacer or ADL, but with a preference for omitting obscuring
layer to monitor the dispensing and seal formation, the
transmission layer is preferably an ADL-type layer or a combination
of ADL and spacer, minimizing the risk of spacer layer puncturing
the backing layer.
Composition: Silpuran 2400/20, Part A and Part B polymers
(Wacker)
Silpuran 2400
Component A
[0505] Color translucent
Viscosity (Plate/Cone) DIN EN ISO 3219 1800 mPa s
[0506] Density DIN EN ISO 2811 1.00 g/cm.sup.3
Component B
[0507] Color translucent
Viscosity (Plate/Cone) DIN EN ISO 3219 1800 mPa s
[0508] Density DIN EN ISO 2811 1.00 g/cm.sup.3 Product data
(catalyzed A+B) Mix ratio A:B1:1 Color translucent Pot life at
23.degree. C. 21 min Product data (cured)
Hardness Shore A ISO 868 7
Hardness Shore 00 ASTM 2240/Type 00 55
[0509] Tensile strength ISO 37 2.00 N/mm2 Elongation at break ISO
37 600% Tear strength ASTM D 624 B 3.0 N/mm Curing conditions: 10
min/100.degree. C.
[0510] Run 8A
Followed as detailed in procedure A of the patent spec with
application of Silpuran 2400/20. Dressing before application of
Silpuran 2400/20 Dressing immediately after application of Silpuran
2400/20 A torch/flash used to examine the reflection of the
silicone and ensure no pin holes were present in the composition
immediately following application. Cured composition (90 minutes
was allowed to elapse, and cure beyond manual kinetic point
confirmed). Sealant was not effective as there was no cured sealant
across the cut face. Gap demonstrated
Run 8B
[0511] Followed as detailed in procedure B of the patent spec with
application of Silpuran 2400/20. Dressing before application of
Silpuran 2400/20 Dressing immediately after application of Silpuran
2400/20 Cured composition (90 minutes was allowed to elapse, and
cure beyond manual kinetic point confirmed) Sealant was effective
when it had been dispensed into the transmission layer
directly.
[0512] It was noted that whilst the spacer layer was more resilient
to compression when the cured silicone was inside it then the
unfilled spacer; by comparison to run 8A where the same sealant had
been applied across the cut face the profile of the sealant was
less pronounced and (subjectively) the rigidity was significantly
less.
[0513] The following observations were made:
[0514] Significantly less sealant was needed when sealing the
internal space of the transmission layer as opposed to sealing over
the cut end.
[0515] The resulting finish was significantly neater when the
sealant was applied into the internal space of the transmission
layer as opposed to sealing over the cut end. The silicone that
flowed onto the wound model came from the fact that the nozzle
aperture was not sufficient to penetrate the spacer layer deeply
and was thus delivering silicone close to the edge of the cut
transmission layer. A dispensing nozzle with external bore small
enough to penetrate the transmission layer could be inserted into
the transmission layer (to a selected distance) at the time of
dispensing and limit the amount of curing silicone that was able to
travel the distance back out of the transmission layer.
[0516] The absence of an obscuring layer or opaque layer above the
bridge in Run 8B (such as the absorbent layer present in Run 8A)
allowed the user to clearly see the ingress of the sealant into the
bridge during dispensing. This provided control over where to apply
the sealant, how much and allowed the user to ensure that no air
paths remained in the seal.
[0517] The low viscosity of Silpuran 2400/20 was a significant
advantage during dispensing. It flowed well into the transmission
layer and appeared to readily conform to the internal shape of the
transmission layer. A low viscosity material would also have the
added advantage of reducing the back pressure generated in a
dispensing unit. This could be of particular importance if a
dispensing nozzle with narrow aperture was used (as desired to
penetrate the transmission layer) so that the back pressure
generated by the liquid travelling through the resultant narrow
orifice was reduced. To provide an example of the influence of back
pressure, in a dispenser comprising a double barrelled syringe with
integral mixer it would relate to the force that the user needed to
apply to the syringe plunger to eject the liquid.
Example 13
Dispenser Design
[0518] A dispenser with a single nozzle that penetrated the
transmission layer could be an advantage.
[0519] A dispenser with multiple nozzles could be an advantage,
however, subject to the width of this head, injecting the sealant
into a dressing following body contours be limited. Therefore
either the width of the mixing head should be balanced so as to
ensure ease of application (wider better) versus following body
contours (narrower better).
[0520] Or the mixing heads should be conformable so as to be moved
to shape (ideally this would stay in position once moved) to allow
the user to approximate the shape.
[0521] Thought should be given to the clearance of the dispenser
given that it will be entering the transmission at an acute angle
to the skin.
Results of Foregoing Examples are Illustrated as Follows:
[0522] Example 6b results Exp 3 Silpuran 2445
* * * * *
References