U.S. patent application number 15/454490 was filed with the patent office on 2017-09-28 for wound cleansing apparatus.
The applicant listed for this patent is SMITH & NEPHEW PLC. Invention is credited to Patrick Lewis Blott, Clare Green, Bryan Greener, Edward Yerbury Hartwell, Julian Lee-Webb, Robin Paul Martin, Derek Nicolini, Tina Michelle Walker.
Application Number | 20170274195 15/454490 |
Document ID | / |
Family ID | 29725502 |
Filed Date | 2017-09-28 |
United States Patent
Application |
20170274195 |
Kind Code |
A1 |
Blott; Patrick Lewis ; et
al. |
September 28, 2017 |
WOUND CLEANSING APPARATUS
Abstract
An apparatus for cleansing and promoting tissue growth in
wounds, in which irrigant fluid optionally containing cell
nutrients and/or other physiologically active material from a
reservoir connected to a conformable wound dressing and wound
exudate from the dressing are recirculated by a device for moving
fluid through a flow path which passes through the dressing, a
biodegradable scaffold in contact with the wound bed and a means
for fluid cleansing and back to the dressing. The apparatus has
means for supplying thermal energy to the fluid in the wound. The
cleansing means (which may be a single-phase, e.g.
micro-filtration, system or a two-phase, e.g. dialytic system)
removes materials deleterious to wound healing, and the cleansed
fluid, still containing materials that are beneficial in promoting
wound healing, is returned to the wound bed. The dressing and a
method of treatment using the apparatus.
Inventors: |
Blott; Patrick Lewis; (York,
GB) ; Greener; Bryan; (York, GB) ; Hartwell;
Edward Yerbury; (Hull, GB) ; Walker; Tina
Michelle; (York, GB) ; Lee-Webb; Julian;
(York, GB) ; Nicolini; Derek; (Hull, GB) ;
Green; Clare; (Crockey Hill, GB) ; Martin; Robin
Paul; (York, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SMITH & NEPHEW PLC |
London |
|
GB |
|
|
Family ID: |
29725502 |
Appl. No.: |
15/454490 |
Filed: |
March 9, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15043143 |
Feb 12, 2016 |
9616208 |
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15454490 |
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|
14575794 |
Dec 18, 2014 |
9289542 |
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15043143 |
|
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|
12832032 |
Jul 7, 2010 |
8926592 |
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14575794 |
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10575875 |
Feb 1, 2007 |
7794450 |
|
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PCT/GB2004/004564 |
Oct 28, 2004 |
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12832032 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 13/0206 20130101;
A61M 1/0062 20130101; A61M 1/0088 20130101; A61F 13/00068 20130101;
A61F 2013/00357 20130101; A61M 3/0204 20140204; A61M 2205/3653
20130101; A61M 2205/368 20130101; A61F 13/0216 20130101; A61M 27/00
20130101; A61M 3/0229 20130101; A61M 2202/0208 20130101; A61M
3/0212 20140204; A61F 2007/0059 20130101; A61M 1/0058 20130101;
A61M 1/0084 20130101 |
International
Class: |
A61M 35/00 20060101
A61M035/00; A61M 3/02 20060101 A61M003/02; A61M 1/00 20060101
A61M001/00; A61F 13/02 20060101 A61F013/02; A61F 13/00 20060101
A61F013/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 28, 2003 |
GB |
0325126.1 |
Claims
1.-10. (canceled)
11. An apparatus for treatment of a wound, comprising: a wound
dressing comprising: a backing layer capable of forming a
relatively fluid-tight seal or closure over a wound, the backing
layer comprising at least one aperture; a conduit in fluid
communication with the aperture in the backing layer and configured
to communicate negative pressure to a space beneath the backing
layer; and a heating element configured to supply thermal energy to
the wound.
12. The apparatus of claim 11, wherein the wound dressing further
comprises a boss configured to at least support an end portion of
the conduit.
13. The apparatus of claim 11, further comprising a source of
negative pressure in fluid communication with the conduit.
14. The apparatus of claim 11, wherein the wound dressing further
comprises a membrane configured to contact the wound
15. The apparatus of claim 11, wherein the wound dressing further
comprises a reservoir for retaining wound exudate.
16. The apparatus of claim 11, wherein the heating element is
mounted on the wound dressing.
17. The apparatus of claim 16, wherein the heating element is
mounted on the backing layer.
18. The apparatus of claim 16, wherein the heating element is
mounted at the aperture in backing layer.
19. The apparatus of claim 11, wherein the heating element is an
electrical heating element.
20. The apparatus of claim 11, wherein the heating element
comprises a radiative heater.
21. The apparatus of claim 11, wherein the heating element
comprises an inductive heater.
22. The apparatus of claim 11, wherein the heating element supplies
thermal energy to the wound via electromagnetic radiation.
23. The apparatus of claim 22, wherein the electromagnetic
radiation comprises radiofrequency radiation.
24. The apparatus of claim 11, wherein the heating element supplies
thermal energy to wound exudate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/043,143, filed on Feb. 12, 2016, which is a
continuation of U.S. patent application Ser. No. 14/575,794 filed
on Dec. 18, 2014 and now issued as U.S. Pat. No. 9,289,542, which
is a continuation of U.S. patent application Ser. No. 12/832,032
filed on Jul. 7, 2010 and now issued as U.S. Pat. No. 8,926,592,
which is a continuation of U.S. patent application Ser. No.
10/575,875, filed on Feb. 1, 2007 and now issued as U.S. Pat. No.
7,794,450, which is a U.S. National Phase of the PCT International
Application No. PCT/GB2004/04564, filed on Oct. 28, 2004 and which
claims priority to application GB 0325126.1, filed on Oct. 28,
2003. The entirety of these preceding disclosures is hereby
incorporated by reference.
BACKGROUND AND SUMMARY OF INVENTION
[0002] The present invention relates to apparatus and a medical
wound dressing for irrigating, supplying thermal energy to and
cleansing wounds, and a method of treating wounds using such
apparatus for irrigating, supplying thermal energy to and cleansing
wounds.
[0003] It relates in particular to such an apparatus, wound
dressing and method that can be easily applied to a wide variety
of, but in particular chronic, wounds, to cleanse them of materials
that are deleterious to wound healing, whilst retaining materials
that are beneficial in some therapeutic aspect, in particular to
wound healing.
[0004] Before the present invention, aspirating and/or irrigating
wounds and apparatus therefor were known, and tended to be used to
remove wound exudate during wound therapy. In known forms of such
wound therapy, the offtake from the wound, especially when in a
highly exuding state, is voided to waste, e.g. to a collection
bag.
[0005] Materials deleterious to wound healing are removed in this
way.
[0006] However, materials that are beneficial in promoting wound
healing, such as growth factors, naturally occurring
anti-inflammatories, and other physiologically active components of
the exudate from a wound are lost to the site where they can be
potentially of most benefit, i.e. the wound bed, when such therapy
is applied.
[0007] It thus would be desirable to provide a system of therapy
which [0008] a) can remove materials deleterious to wound healing
from wound exudate, whilst retaining materials that are beneficial
in promoting wound healing in contact with the wound bed, and/or
[0009] b) which allows fluids containing active amounts of
materials that are beneficial in promoting wound healing to pass
into and/or through the wound in contact with the wound bed.
[0010] Dialysis is a known method of treating bodily fluids such as
blood ex vivo, to cleanse them of materials that are deleterious to
the body systemically. Retaining materials that are beneficial in
some therapeutic aspect in the treated fluid is not an object of
dialysis.
[0011] This method of treating bodily fluids is also a systemic
therapy, since the treated fluid is returned to within the body.
This is in contrast to a topical therapy in which the treated fluid
is recycled outside the body, e.g. to a wound.
[0012] Dialysis also requires large amounts either of bodily
fluids, such as blood, or of dialysate, and consequently the
relevant devices tend not to be portable.
[0013] Even when in a highly exuding state, chronic wounds produce
relatively little fluid to be treated and relatively little
materials that are beneficial in some therapeutic aspect to be
retained in the wound and/or its environment.
[0014] It is an object of the present invention [0015] a) to
obviate at least some of the abovementioned disadvantages of known
aspiration and/or irrigation therapy systems, and [0016] b) to
provide a system of therapy which can remove materials deleterious
to wound healing from wound exudate, whilst retaining materials
that are beneficial in promoting wound healing in contact with the
wound bed,
[0017] It is a further object of the present invention [0018] a) to
obviate at least some of the abovementioned disadvantages of known
dialysis systems, and [0019] b) to provide a system of therapy
which can remove materials deleterious to wound healing from wound
exudate, whilst retaining materials that are beneficial in
promoting wound healing in contact with the wound bed, [0020] c)
without affecting the body systemically.
[0021] It is a yet further object of the present invention [0022]
a) to obviate at least some of the abovementioned disadvantages of
known dialysis systems, and [0023] b) to provide a system of
therapy which can remove materials deleterious to wound healing
from wound exudate, whilst retaining materials that are beneficial
in promoting wound healing in contact with the wound bed, [0024] c)
without affecting the body systemically, and [0025] d) which is
portable.
[0026] Additionally, it is generally believed that the body's own
metabolic activities are at an optimum at or near the temperature
naturally occurring in the relevant bodily part.
[0027] Examples of metabolic molecules involved in tissue healing
processes that are beneficial in promoting wound healing include
enzymes, growth factors and anti-inflammatories, and other
physiologically active components of the exudate from a wound.
[0028] These are believed to act best at temperatures found in the
relevant bodily part in which they occur, varying between normal
temperatures found at the body surface and those at the body
core.
[0029] The body core is at a higher temperature than the surface,
but surface temperatures at 33.degree. C. and above are still
relatively close to core body temperatures of 36 to 38.degree. C.
(`normothermic temperature`). Wounds, and in particular chronic
wounds, may have a lower temperature, e.g. 24 to 26.degree. C.,
i.e., substantially below the optimum temperature. Thus, the
temperature of the wound itself is deleterious to wound
healing.
[0030] This may result in slow wound healing, loss of cell
proliferation, and/or growth that does not have a strong
three-dimensional structure adhering well to and growing from the
wound bed.
[0031] Conventional wound aspiration and/or irrigation therapy
systems thus often create a wound environment under a backing layer
where [0032] a) not only are beneficial materials lost to the site
where they can be potentially of most benefit, i.e., the wound bed,
when such therapy is applied, but [0033] b) the wound healing
processes, e.g. enzymic activity on tissue growth, are inhibited by
sub-optimal temperatures.
[0034] Heated dressings are known, but such forms of wound dressing
do not simultaneously irrigate the wound environment under the
backing layer. This will result in materials deleterious to wound
healing in wound exudate being retained in the wound environment
and hindering wound healing in spite of any stimulation of wound
healing from wound temperature regulation.
[0035] There would thus be an advantage, in particular in chronic
wounds, in providing means for more than one therapy in a single
dressing [0036] a) which not only removes materials deleterious to
wound healing from wound exudate, whilst retaining materials that
are beneficial in promoting wound healing in contact with the wound
bed, but [0037] b) promotes wound healing by creating a wound
environment under the dressing with temperatures which stimulate
the activity of metabolic molecules that are beneficial in
promoting wound healing, e.g. temperatures near 36 to 38.degree. C.
(`normothermic temperature`).
[0038] It is an object of the present invention [0039] a) to
obviate at least some of the abovementioned disadvantages of known
wound dressing, and [0040] b) to provide a system of therapy which
cleanses wounds, but also supplies thermal energy to the wound, in
particular one which [0041] i) can remove materials deleterious to
wound healing from wound exudate, whilst retaining materials that
are beneficial in promoting wound healing in contact with the wound
bed, and [0042] ii) maintains wounds at or near normothermic
temperature.
[0043] It is an object of the present invention [0044] a) to
obviate at least some of the above-mentioned disadvantages of known
wound dressing, and [0045] b) to provide a system of therapy that
conveniently cleanses wounds, but also maintains wounds at or near
normothermic temperature.
[0046] A disadvantage of known heated wound dressings is that it is
imperative but not easy to avoid the heater, especially an
electrical heater, from scorching the wound and/or surrounding
surfaces. This is especially so when the dressing is in contact
with the wound bed.
[0047] Several devices for applying to the wound to try to do so
have been proposed. In one form, a stiff flange or lip extends
around the periphery of the dressing to space the surface of the
wound in use away from the heater. Such a wound dressing is
cumbersome. Whilst it may be acceptable for hospital use, the stiff
flange does little for patient comfort, and heightens the risk of
inflammation of a wound and/or the leakage of wound exudate. There
would be a further advantage in providing such a wound dressing
that conforms to the shape of the bodily part to which it is
applied.
[0048] It is an object of the present invention [0049] a) to
obviate at least some of the abovementioned disadvantages of known
wound dressing, and [0050] b) to provide a system of therapy which
[0051] i) can remove materials deleterious to wound healing from
wound exudate, whilst retaining materials that are beneficial in
promoting wound healing in contact with the wound bed, [0052] ii)
which supplies thermal energy to and/or through the wound, and
[0053] iii) comprises a conformable wound dressing.
[0054] Thus, according to a first aspect of the present invention
there is provided an apparatus for irrigating, supplying thermal
energy to, and cleansing wounds, characterized in that it comprises
[0055] a) a fluid flow path, comprising [0056] i) a conformable
wound dressing, having a backing layer which is capable of forming
a relatively fluid-tight seal or closure over a wound and at least
one inlet pipe for connection to a fluid supply tube, which passes
through and/or under the wound-facing face, and [0057] and at least
one outlet pipe for connection to a fluid offtake tube, which
passes through and/or under the wound-facing face, the point at
which the or each inlet pipe and the or each outlet pipe passes
through and/or under the wound-facing face forming a relatively
fluid-tight seal or closure over the wound, [0058] at least one
inlet pipe being connected to a fluid recirculation tube, and at
least one outlet pipe being connected to a fluid offtake tube; and
[0059] ii) a means for fluid cleansing having at least one inlet
port connected to a fluid offtake tube and at least one outlet port
connected to a fluid recirculation tube; [0060] b) a fluid
reservoir connected by a fluid supply tube to an integer of the
flow path (optionally or as necessary via means for flow switching
between supply and recirculation); [0061] c) a device for moving
fluid through the wound dressing and means for fluid cleansing, and
optionally or as necessary the fluid supply tube; [0062] d) the
apparatus having means for supplying thermal energy to the fluid in
the wound, and [0063] e) optionally means for bleeding the
flowpath, such that fluid may be supplied to fill the flowpath from
the fluid reservoir via the fluid supply tube (optionally or as
necessary via the means for flow switching) and recirculated by the
device through the flow path.
[0064] Where any pipe is described in connection with the operation
of the apparatus as being connected or for connection to a (mating
end of a) tube, e.g. a fluid supply tube, fluid recirculation tube
or fluid offtake tube, the pipe and the tube may form a single
integer in the flow path through which the circulating fluid from
the wound passes.
[0065] An advantage of such wound dressings is that it is easy to
avoid overheating of the wound and/or surrounding surfaces,
especially by electrical heating, since the heating must always
pass to the wound through a heat transfer medium (the irrigant).
This eliminates direct contact of the wound bed with the heater,
and irrigant may be used as a heat transfer medium in a highly
controllable manner.
[0066] The apparatus is most favourable to the wound healing
process in chronic wounds, and thus for irrigating, supplying
thermal energy to, and cleansing wounds such as diabetic foot
ulcers, and especially decubitus pressure ulcers.
[0067] However, thermal energy may also appropriately be applied
using the apparatus to aid the healing process in other wound
types, such as acute and/or surgical wounds, including burns.
[0068] In a preferred mode, the present invention is used to
provide a system of therapy which conveniently cleanses wounds, but
also maintains them at or near normothermic temperature.
[0069] Accordingly a preferred type of the apparatus of the
invention for irrigating, supplying thermal energy to and cleansing
wounds is provided with means for maintaining the wound at or near
normothermic temperatures.
[0070] As noted above, the apparatus of the present invention for
irrigating, supplying thermal energy to, and cleansing wounds has a
direct effect on active components of fluid in contact with the
wound, in particular solutes or disperse phase species that are
beneficial in promoting wound healing that are in contact with the
wound bed. Additionally, cell mitochondria aid proliferation and
hence wound healing, in particular in chronic wounds, and are
stimulated by near infrared radiation.
[0071] Application of such radiation to the wound resulting in an
increase in cell proliferation in the tissue underlying to the
wound, and in the breaking strength of the new tissue.
[0072] Other physiologically active components of the cells in the
tissue underlying the wound that are beneficial in promoting wound
healing may also be stimulated by radiation on the wound.
[0073] Examples of means for supplying thermal energy to the fluid
in the wound include as may be appropriate conducted thermal
energy, electromagnetic radiation of an appropriate wavelength, or
(less often), as convected thermal energy.
[0074] In the present apparatus, heat will usually be conducted to
the wound bed by the irrigant and/or wound exudate within the
dressing.
[0075] However, thermal energy may as appropriate be supplied to
the irrigant and/or wound exudate within the dressing, and may be
applied to the fluid by any suitable means, at any suitable point,
often depending on particular components and/or materials that are
used.
[0076] Examples of such means include [0077] a) direct conductive
contact of the irrigant and/or wound exudate with a heater and/or
conductively heated component of the apparatus flow path; [0078] b)
direct electromagnetic irradiation at an appropriate wavelength,
e.g. infrared and/or near infrared from a radiative heater of the
irrigant fluid and/or wound exudate; and/or [0079] c)
electromagnetic irradiation from a radiative heater of a component
of the apparatus flow path that absorbs electromagnetic irradiation
at an appropriate wavelength, e.g. infrared and/or near infrared
and is in direct conductive contact with the irrigant and/or wound
exudate.
[0080] Accordingly, one embodiment of the present apparatus for
irrigating, supplying thermal energy to and cleansing wounds
supplying thermal energy to and cleansing wounds is characterized
in that it comprises means for providing thermal energy to the
fluid in the wound.
[0081] Another embodiment of the present apparatus for irrigating,
supplying thermal energy to and cleansing wounds is characterized
in that it comprises means for supplying electromagnetic radiation
of an appropriate wavelength to the fluid in the wound.
[0082] Another embodiment of the present apparatus for irrigating,
supplying thermal energy to and cleansing wounds is characterized
in that it comprises means for supplying electromagnetic radiation
of an appropriate wavelength to the fluid in the wound.
[0083] The heater of the irrigant fluid and/or wound exudate and/or
heated component of the apparatus flow path may be at any
convenient or appropriate position or component of the apparatus
flow path.
[0084] Examples include a heater and/or conductively heated
component of the apparatus flow path [0085] a) mounted distally of
the body on, in or inside of the dressing; [0086] b) mounted in,
on, at or near one or more of the fluid inlet pipe(s) and outlet
pipe(s) that pass through and/or under the wound-facing face of the
backing layer; [0087] c) mounted in, on, at or near one or more of
the connectors in the tubes that form the flow path of the
apparatus; [0088] d) mounted in, on, at or near the reservoir;
and/or [0089] e) mounted in, on, at or near the means for fluid
cleansing.
[0090] As noted above, the irrigant and/or wound exudate fluid in
the interior of the wound dressing is beneficially maintained at a
temperature that is at or near the temperature naturally occurring
in the relevant bodily part and/or normothermic temperature.
[0091] The desired or optimum temperature of the wound will
substantially determine [0092] a) the position along the apparatus
flow path or the component of the apparatus flow path where the
heater and/or conductively heated component of the apparatus flow
path is mounted relative to the dressing; [0093] b) the flow rate
of irrigant fluid and/or wound exudate; [0094] c) the temperature
to which the point of supply of thermal energy to apparatus is
raised; [0095] d) the thermal insulation of the system in which the
fluid recirculates and heat is conducted to the wound; and/or
[0096] e) the nature of the heater.
[0097] In examples of direct conductive contact of the irrigant
and/or wound exudate with a heater and/or conductively heated
component of the apparatus flow path, the heater may be or be
connected to a heat exchanger mounted in conductive contact with
irrigant and/or wound exudate at an appropriate point in the system
in which the fluid recirculates and heat is conducted to the
wound.
[0098] The heat exchanger may comprise an array of thermally
conductive extended surfaces, such as fins, baffles or other like
structures of conductive material in a more convoluted form with a
relatively large surface area.
[0099] These transfer thermal energy when a temperature drop is
applied over them, mounted in conductive contact with irrigant
and/or wound exudate, with spaces therebetween such that wound
irrigant and/or wound exudate may recirculate through the
spaces.
[0100] Alternatively, where appropriate it may be provided in the
form of a like array of conductive hollow structures, such as
pipes, tubes or other like structures in the apparatus flow path,
through which a heat exchanger fluid recirculates and transfers
heat from a heat source to be conducted to the wound.
[0101] The array of conductive hollow structures may consist
essentially of small apertures or pores that may form such bores,
channels, conduits and/or passages through a heated metal sinter,
such as one of e.g. stainless steel, mounted in conductive contact
with irrigant and/or wound exudate in the apparatus flow path,
through which the fluid recirculates, so that heat is conducted to
the wound.
[0102] Such a heat exchanger may be outside the wound space and the
backing layer or within the wound space and under the backing
layer. If outside the wound space and the backing layer, it is
preferably as close to the wound dressing backing layer as
possible.
[0103] This is especially the case where the apparatus of the
invention for irrigating, supplying thermal energy to and cleansing
wounds is intended to maintain the wound at or near normothermic
temperatures, since the heating must always pass to the wound
through heat transfer via the irrigant and/or wound exudate
recirculated through the wound space, and the longer the connection
to the inlet pipe(s) on the wound dressing and the dwell time of
the irrigant therein, the greater the undesired loss of heat from
the irrigant fluid. It may be mounted outside the backing layer,
e.g. 6 to 90 mm from the wound bed, e.g. on an inlet pipe and/or a
fluid recirculation tube.
[0104] Where the heat exchanger is mounted outside the wound space
and the backing layer, and transfers heat from a heat source to
wound irrigant and/or wound exudate recirculating through the
space, to be conducted to wound, the apparatus flow path, through
which irrigant and/or wound exudate recirculates, at an appropriate
point in the heat exchanger may be provided in the form of a
conductive hollow structure in convoluted form with a relatively
large surface area.
[0105] This transfers thermal energy from the heater and/or a heat
exchanger fluid recirculated in conductive contact with it to the
irrigant to be conducted to the wound.
[0106] In examples of such conductive contact of the irrigant
and/or wound exudate with a heater and/or heat exchanger mounted,
the apparatus flow path may be in convoluted form with a relatively
large surface area, such as one or more pipes, tubes or other like
structures, as appropriate `in parallel` and/or with spaces
therebetween, in the form of a spiral, helix or spiral helix, or
loop or a more convoluted form, e.g. a meandering, tortuous,
winding, zigzag, serpentine or boustrophedic (i.e. in the manner of
a ploughed furrow) pattern, in particular a conductive hollow
spiral.
[0107] Such a part of the flow path of the apparatus may be in
direct conductive contact with a heater and/or conductively heated
component, e.g. a conductive hollow spiral part of the flow path of
the apparatus may within a moulded disc-shape housing defined by a
film, sheet or membrane that [0108] a) has a heater and/or
conductively heated component in direct conductive contact with and
on at least one surface of the conductive hollow spiral part of the
flow path, e.g. an electrically heated element mounted in an
insulated so-called clamshell case, or [0109] b) contains a heat
exchanger fluid recirculated between spaces between turns of the
spiral to which it is applied.
[0110] A pre-formed spiral of tubing is housed in the heater case,
which is preferably a rigid integer for convenient handling, which
is then closed.
[0111] An apparatus flow path in a heat exchanger in the form of a
helix or spiral helix, 5 or loop or a more convoluted form, may
also be in direct conductive contact with and within an appropriate
moulded housing similarly provided in a form which transfers
thermal energy from a heater and/or a heat exchanger fluid
recirculated in conductive contact through it.
[0112] Alternatively, where appropriate, a flow path through which
a heat exchanger fluid recirculates, e.g. a pre-formed spiral of
tubing, may lie in spaces between and/or adjacent to turns or `in
parallel` arms of the apparatus flow path, and so transfer heat
from a heat source to the irrigant and/or wound exudate flow. The
whole may be loaded into a heater case, which is then closed. The
flows of the heat exchanger fluid and the irrigant may be in a co-
or preferably countercurrent direction.
[0113] In all embodiments, the case has entry and exit apertures,
holes, openings, orifices, slots, channels and/or conduits, e.g. in
the edge extending between the faces of the case, through which the
irrigant tubing passes, and into which it may be sealed or
otherwise attached, for example by heat-sealing, and where it may
be connected to other integers of the flow path.
[0114] Rather than using tubing, e.g. a conductive hollow spiral to
define a tortuous path through which the irrigant is forced to flow
in part of the flow path of the apparatus within a heat exchanger,
it may be recirculated in conductive contact through one or more
channels, conduits or passages or other like structures, as
appropriate `in parallel` and/or with spaces therebetween.
[0115] It or they may be in the form of a spiral, loop or a more
convoluted form, e.g. a meandering, tortuous, winding, zigzag,
serpentine or boustrophedic (i.e., in the manner of a ploughed
furrow) pattern, as appropriate `in parallel` and/or with spaces
therebetween.
[0116] This shape arrangement may, e.g. be made by sealing two
flexible films, sheets or membranes together along lines of contact
to form a convoluted flow path within a sealed chamber. This flow
path is defined by one or more channels, conduits or passages or
other like structures in a tortuous path through which the irrigant
is forced to flow in part of the flow path of the apparatus, in
particular in a boustrophedic (i.e., in the manner of a ploughed
furrow) pattern. It may be made by sealing by a suitable method
(e.g. radio frequency or impulse heat welding.
[0117] It or each is in conductive contact, preferably throughout
its length, with a heater In at least one surface of the films
defining the part of the flow path, e.g. an electrically heated
element. The whole may be appropriately mounted in a case, bag,
chamber or pouch of conventional type, such as a pouch or other
structure, e.g. of polymer, which can contain the heater and/or
heat exchanger, which is preferably a rigid integer to provide for
convenient handling.
[0118] Alternatively, where appropriate, a flow path through which
a heat exchanger fluid recirculates may be made to lie in spaces
between and/or adjacent to turns or `in parallel` arms of the
apparatus flow path, and so transfer heat from a heat source to the
irrigant and/or wound exudate flow. The whole may be appropriately
housed in a case, bag, chamber or pouch of conventional type, as
above. The flows of the heat exchanger fluid and the irrigant may
be in a co- or preferably counter-current direction.
[0119] In all embodiments, the or each channel, conduit or passage
or other like structure, will as appropriate at its inlet and
outlet communicate with and be connected to a tube, pipe, duct or
other like structure which in turn communicates with and is
connected to other integers of the flow path, e.g. an irrigant feed
pump.
[0120] The case, bag, chamber or pouch of conventional type, as
referred to above has at least one entry and exit aperture, hole,
opening, orifice and/or slot, through which the tubes, pipes, ducts
or other like structures pass, and into which they may be sealed or
otherwise attached, for example by heat-sealing.
[0121] For convenient handling in use, the case, bag, chamber or
pouch of conventional type is adapted to fit as closely as possible
into a receiving aperture, hole, opening, orifice and/or slot in a
heat source to transfer heat to the irrigant in the apparatus flow.
For example, the flat structures described by way of example above
as suitable for use in this integer of the present invention may be
sandwiched between parallel electrically heated plates.
[0122] It is preferably locked in position such that it cannot be
dislodged accidentally in normal use, but can easily be removed
when required.
[0123] For convenient handling in use, the heating device itself,
into which the pouch is inserted, may be mounted securely on the
patient and/or the wound dressing (if it is as close as possible
to, e.g. 6 to 900 mm from the wound bed, e.g. on an inlet pipe
and/or a fluid recirculation tube to reduce undesired loss of heat
from the irrigant).
[0124] The means for providing thermal energy to the fluid in the
wound may suitably comprise one or more such heater and/or heat
exchanger modules connected in series and/or in parallel arms of
the apparatus flow path.
[0125] Some of the factors likely to affect heat transfer in all
embodiments of the exchanger are the temperature of the heater
element, the structure and material appropriate to the heat
exchanger and any heat exchanger fluid, the wall thickness and
surface area in contact with the heater of any pipe, tube, channel,
conduit, passage or other like structure, the length of irrigant
flow path and the irrigant linear flow rate, the length of any heat
exchanger fluid and any heat exchanger fluid flow rate, and whether
any heat exchanger fluid and the irrigant flow are in co- or
countercurrent directions, as will be apparent to the skilled
person.
[0126] The structure for holding irrigant in contact with the
heater may suitably be a pipe, tube, channel, conduit, passage or
the like. Such a structure may be a pipe, tube, channel, conduit,
passage or the like on and integral with a face of the heater,
which may be, e.g. an electrically heated plate, so that the
irrigant and/or wound exudate recirculates in direct conductive
contact with the heater in the heat exchanger. Alternatively or
additionally, it may be in the form of a discrete pipe or tube
permanently or releasably attached to at least one face of the
heater, which again may be, e.g. at least one electrically heated
plate, so that the irrigant and/or wound exudate recirculates in
indirect conductive contact with the heater in the heat
exchanger.
[0127] In either case, the walls of any pipe, tube, channel,
conduit, passage or other like structure for irrigant in contact
with the heater may suitably be no more than 600 micron thick.
Where it is in contact with any pipe, tube, channel, conduit,
passage or other like structure for heat exchanger fluid the
combined thickness of the walls may suitably be 10 to 500 micron.
When heat exchanger fluid and the irrigant flow are in
counter-current directions, the thickness may be increased.
[0128] The surface area of any pipe, tube, channel, conduit,
passage or other like structure for irrigant and! or wound exudate
flow in contact with the heater or any pipe, tube, channel,
conduit, passage or other like structure for a heat exchanger fluid
(including those in a heated metal sinter) may suitably be no less
than 100 mm.sup.2, such as 625 to 2500 mm.sup.2, e.g. up to 6400
mm.sup.2.
[0129] Any pipe or tube, or any films, sheets or membranes sealed
together along lines of contact to form a convoluted irrigant flow
path, such as a channel, conduit, passage or other like structure
may be of thermoplastic polyurethane or PVC but other materials may
be used (e.g. thermoplastic elastomers), provided they are of
suitable strength and flexibility and/or rigidity to provide for
convenient handling, cleared for medical use and fulfill the
desired performance specification.
[0130] The length of irrigant flow path, such as in the structures
described by way of example above as suitable for use in this
integer of the present invention may suitably be no less than 10
mm, such as 25 to 1600 mm, e.g. up to 2500 mm in the case of a
1.5.times.2.7 mm tube with flow rates of up to 400 ml/hr, up to 750
mm in the case of a similar channel defined by two welded films,
and up to 360 mm in the case of a similar channel integral with a
heater face as described hereinbefore, depending on particular
components and/or materials that are used and on the surface area
noted above.
[0131] For larger surface area of any pipe, tube, channel, conduit,
passage or other like structure for irrigant flow, the length of
irrigant flow path, e.g. in the structures described above may
suitably be more than 2500 mm, such as (by way of example only)
4000 mm.
[0132] The volume flow rate of irrigant and/or wound exudate in
recirculation through the means for providing thermal energy to the
fluid in the wound may suitably and typically be the same as in the
rest of the system in which the fluid recirculates, as described
below. That is, of the order of 1 to 10 ml/cm.sup.2/24 hour, where
the cm.sup.2 refers to the wound area, e.g. 1 to 750
ml/cm.sup.2/hour, such as 1 to 500 ml/hr.
[0133] However, the cross-sectional area of any pipe, tube,
channel, conduit, passage or other like structure for irrigant in
the means for providing thermal energy to the fluid may be adjusted
to increase or decrease the irrigant linear flow rate for the
desired performance specification. To achieve the target
temperature at the heater outlet, the irrigant linear flow rate in
a typical heat exchanger with the irrigant flow path in the
structures described above may suitably be 1 to 600 mm/s, e.g. up
to 370 mm/s.
[0134] The surface area and the irrigant linear flow rate and
length of irrigant flow path all depend inter alia on the
particular target wound temperature and temperature at the heater
outlet. Those noted above are generally suitable for use in this
integer, where the temperature of the wound is to be held within a
range of temperatures such as 34 to 40, preferably 35 to 39, and
optimally 36 to 38.degree. C. at the wound bed, preferably at
normothermic temperatures, throughout the use of the present
apparatus for irrigating, supplying thermal energy to and cleansing
wounds.
[0135] Depending inter alia on the particular target wound
temperature and the loss of heat from the irrigant between the
means for providing thermal energy to the fluid and the wound
dressing (especially if it is not as close as possible to, e.g.,
more than 6 to 900 mm from the wound bed), the temperature of
irrigant leaving the heater will often conveniently be fixed at
39.degree. C.+/-3.degree. C., independently of flow rate, in
particular to maintain an at or near normothermic temperature
within the dressing, especially for chronic wounds.
[0136] The exit temperatures may of course be adjusted to increase
or decrease wound temperatures, by adjusting the foregoing
parameters, such as increasing or decreasing the irrigant linear
flow rate for the desired temperature specification.
[0137] For example, with the flat structure heating pouch design
described by way of example above as suitable for use in this
integer and electrical heater (heating from only one side) it was
found possible to maintain an irrigant temperature at the heater
outlet of .about.37.degree. C. at irrigant rates of up to
.about.400 ml/hr.
[0138] This allows the liquid entering the wound to be as close as
possible to the patient core temperature of .about.37.degree. C.,
and so help maintain normothermia. The area of pouch in contact
with the heater was .about.750 mm.sup.2. To achieve the target
temperature at the heater outlet at the highest flow rate, the
heater was required to operate at a temperature of approximately
42.degree. C.
[0139] All the foregoing means for providing thermal energy to the
fluid and the wound dressing are especially (but not exclusively)
suited to direct conductive contact of the irrigant and/or wound
exudate with a heater and/or other conductively heated component.
Various embodiments of heaters as a component of the apparatus flow
path of the present apparatus for irrigating, supplying thermal
energy to and cleansing wounds will now be described in detail
hereinafter.
[0140] Examples of conductive heaters include: [0141] a) an
electric heater mounted in conductive contact with irrigant and/or
wound exudate (but electrically insulated from the fluid and the
system in which the fluid recirculates and heat is conducted to the
wound).
[0142] The heater may inter alia comprise: [0143] i) an array of
electrically resistive but conductive wires, fibres, filaments,
strands or other like structures that generate thermal energy when
a voltage drop is applied over them.
[0144] The array may be a parallel array with spaces therebetween,
and the wound irrigant and/or wound exudate may recirculate through
the spaces.
[0145] Alternatively, where appropriate it may be provided in the
form of nonwoven or woven fabric, such as a woven layer or sheet.
This may as appropriate be used essentially as a flat sheet or
membrane of material in a more convoluted form, e.g. conformed to
the form of other structures such as pipes, tubes, etc. in the
apparatus flow path, as a duct, sheath, or casing, or other like
structure.
[0146] Depending on any pressure differential across it may require
other materials on or in it to stiffen, reinforce or otherwise
strengthen it.
[0147] The material of the heater may have a positive or (less
preferably) a negative thermal coefficient of resistance.
[0148] A control feedback circuit is needed with a negative
coefficient of resistance for temperature regulation.
[0149] Materials that are described by way of example herein to be
suitable for use in this aspect of the present invention will be
capable of this function.
[0150] Depending on other components and/or materials that are
present, examples of suitable materials include carbon fibres and
fabric, such as a woven layer or sheet, which may as appropriate be
made essentially of carbonised acrylate, such as polyacrylonitrile
and copolymers thereof [0151] ii) an electrically insulating flat
sheet or membrane substrate that has sites on its surface that are
connected by an array of electrically resistive but conductive
tracks, traces, outlines, or other like structures, e.g. filled
channels, conduit and the like, and, e.g. etched foil, which
generate thermal energy when a voltage drop is applied over
them.
[0152] The array may be a parallel array with spaces therebetween,
connected together at each end, or comprise or consist essentially
of one or more such integers in a spiral, or in a meandering,
tortuous, winding, zigzag, serpentine or boustrophedic (i.e. in the
manner of a ploughed furrow) pattern.
[0153] Examples of suitable materials for the array of electrically
resistive but conductive tracks, traces, outlines, or other like
structures include carbon and/or metals, such as Thermion.TM., a
nickel-coated non-woven carbon fabric and resistance heating
alloys, such as Kanthal.TM., Alkrothal.TM., Nikrothal.TM., and
Nifethal.TM..
[0154] For the electrically insulating flat sheet or membrane
substrate, suitable materials include PTFE, polyamides, and
materials such as aromatic polysulphones, polyethersulphones,
polyetherether-sulphones, polyketones, polyetherketones; and
polyetherether-ketones, and sulphonated derivatives thereof, and
mixtures thereof; and epoxy resins.
[0155] The array of electrically resistive but conductive tracks,
traces, outlines, or other like structures, may be generated by
etching or engraving, e.g. with electron beam irradiation and/or
with fluid chemicals.
[0156] Alternatively, where appropriate it may be provided by
printing, imprinting, stamping or vapour deposition of conventional
type. [0157] iii) an array of electrically resistive but
conductive, mutually connected thermocouples that are potentially
capable of generating thermal energy by the Peltier effect when a
voltage drop is applied over them.
[0158] The array may be a parallel array, with spaces therebetween,
and the wound irrigant and/or wound exudate may recirculate through
the spaces.
[0159] Alternatively, it may be permanently or releasably attached
to the surface of a substrate of the type described by way of
example under ii) as suitable for use in this aspect of the present
invention.
[0160] Depending on other components and/or materials that are
present, examples of suitable materials include thermoelectric
modules comprising pellets of bismuth telluride doped with selenium
and antimony of different conductivity, the thermocouple pairs
being connected in series and sandwiched between ceramic
substrates.
[0161] In the Peltier effect when a voltage drop is applied over a
thermocouple, one part potentially undergoes heating, and can thus
supply thermal energy to the wound through a heat transfer medium
(the irrigant).
[0162] The other part undergoes cooling and can thus act as a
thermal pump from the ambient to the fluid irrigant and exudate in
the apparatus flow path to the wound.
[0163] However, thermal energy transfer in this highly controllable
manner requires orientation of the thermocouple array such that the
side capable of gaining thermal energy by the Peltier effect is in
conductive contact with the irrigant and/or wound exudate.
[0164] Examples of a) i) & ii) include a foam reservoir
dressing, such as Allevyn (.TM., Smith & Nephew) and Tielle
(.TM., Johnson & Johnson), having an electrical heater, mounted
distally of the body on it. [0165] b) an inductive heater element
mounted in conductive contact with irrigant and/or wound exudate
(but electrically insulated from the fluid and the system in which
the fluid recirculates and heat is conducted to the wound).
[0166] The heater may inter alia comprises a piece of ferromagnetic
material, such as magnetic stainless steel in conductive contact
with irrigant and/or wound exudate, and an inductive source that
will be adjacent (but not necessarily attached) to the dressing in
use, but may otherwise be remote from the wound).
[0167] Examples of the latter include a ferromagnetic coil, spiral,
helix or spiral helix, or loop or a more convoluted form, e.g. a
meandering, tortuous, winding, zigzag, serpentine or boustrophedic
(i.e. in the manner of a ploughed furrow) pattern, in particular in
one plane, of an inductive often highly conductive material,
connected to an alternating electrical potential source.
[0168] This is potentially capable of generating thermal energy in
the core when a varying potential is applied to the coil, spiral or
spiral helix, or loop or a more convoluted form.
[0169] This is often at mains voltage and frequency, although a
range of either may be used. [0170] c) a heater mounted in
conductive contact with irrigant and/or wound exudate to which it
transfers thermal energy to the fluid in recirculation from a heat
source within it, which is a fuel cell.
[0171] In this, atmospheric oxygen and/or other molecules oxidize
one or more species of fuel molecules, often in a catalytic
bed.
[0172] Examples of fuel materials that have a strong oxidation
exotherm include gases, where the gaseous phase of the aerosol
system is air and a fuel gas, such as hydrogen or an alkane, such
as methane, ethane and butane. The catalyst is often solid
particulates, such as composites of copper and rare earth oxides,
such as optionally samaria doped ceria, comprised in a crystalline
material for convenient handling; or platinum powder coated onto
carbon paper or cloth. [0173] d) a heater mounted in conductive
contact with irrigant and/or wound exudate to which it transfers
thermal energy to the fluid in recirculation from a heat source
within it, which is a-material that undergoes a highly exothermal
phase change.
[0174] Examples of d) include [0175] i) a heater containing
materials that undergo a highly exothermal crystallisation or
solidification phase change, such as supersaturated solutions of
chemicals, such as metal ion salts.
[0176] Sodium thiosulphate is a source of a strong crystallisation
exotherm, as is sodium acetate solution.
[0177] The fluid or solid material is often comprised in one or
more conformable hollow bodies.
[0178] These may be defined by, for example a polymer film, sheet
or membrane, such as a bag, chamber, pouch or other structure, of
the backing layer, e.g. of polymer film, for convenient
handling.
[0179] In the case where the heat source is in the form of a
crystallisation system, such as one based on sodium thiosulphate,
the bag, chamber, pouch or other structure is often provided with a
source of mechanical shock that is appropriate for inducing
crystallisation.
[0180] Examples include a catastrophically resiliently flexible or
stiff metal button, such as one of e.g. aluminium or stainless
steel.
[0181] Such heaters are less preferred than an electrical heater,
since electrical heating can give constant heating intensities in a
highly controllable manner. In contrast, a strong crystallisation
or solidification exotherm is less controllable or constant. [0182]
ii) a heater containing materials that undergo an exothermal
condensation phase change, i.e., from gaseous or volatile products,
such as the Freon hydrocarbon series to liquids. Preferred
materials include, in particular those that condense at or near
normothermic temperature. Such a heater of the irrigant fluid
and/or wound exudate may be operated as a heat pump that absorbs
thermal energy, e.g. from the environment of a component of the
apparatus flow path into the component of the apparatus flow
path.
[0183] In examples of [0184] a) direct electromagnetic irradiation
at an appropriate wavelength, e.g., infrared and/or near infrared
from a radiative heater of the irrigant fluid and/or wound exudate;
and/or [0185] b) electromagnetic irradiation from a radiative
heater of a component of the apparatus flow path that absorbs
electromagnetic irradiation at an appropriate wavelength, e.g.
infrared and/or near infrared and is in direct conductive contact
with the irrigant and/or wound exudate.
[0186] The heater usually works at such temperatures as will
deliver 34 to 40, preferably 35 to 39, and optimally 36 to
38.degree. C. at the wound bed.
[0187] Examples of sources of direct or indirect electromagnetic
irradiation of the irrigant fluid and/or wound exudate at an
appropriate wavelength include infrared and/or near infrared from a
radiative heater.
[0188] In the apparatus the type and materials of the heater will
be largely determined by its specific function and the wavelengths
and intensities to be applied to the fluid within the far infrared,
mid infrared or near infrared spectrum, and its position in the
apparatus of the invention.
[0189] Examples of suitable wavelengths to apply to the fluid
include:
[0190] for the far infrared, 4 to 1000 micrometre,
[0191] for the mid infrared, 1.4 to 4 micrometre, and
[0192] for the near infrared, 0.75 to 1.5 micrometre.
[0193] Examples of suitable levels of intensity include those
conventionally used in medical applications and known to the
skilled person.
[0194] The higher end of these ranges are potentially more suitable
for hospital use, where relatively high intensity infrared or near
infrared irradiation at relevant wavelengths may be used safely
under professional supervision.
[0195] Such a device may also suitably be one that is capable of
pulsed, continuous, variable, and/or automated and/or programmable
operation.
[0196] Examples include [0197] a) a radiative heater that is an
incandescent filament lamp, light or other like structure, which
is, a source of radiation at relevant wavelengths to be applied to
the fluid, e.g. infrared or near infrared irradiation. Examples of
a) include a heater that is a small infrared lamp, mounted on an
infra-red transparent dressing backing layer. [0198] b) a radiative
heater that is a high-thermal energy, high-intensity LED (light
emitting diode) or other like structure, which is a source of
radiation at relevant wavelengths to be applied to the fluid, e.g.
infrared or near infrared irradiation. [0199] c) a radiative heater
that is a high-thermal energy, high-intensity source of radiation
at relevant wavelengths to be applied to the fluid, e.g. infrared
or near infrared irradiation.
[0200] The type and materials of the heater will be largely
determined by its specific function and the wavelengths and
intensities to be applied to the fluid within the spectrum, and its
position in the apparatus of the invention. [0201] d) Any r.f.
and/or microwave frequency signal generator may be used provided
temperatures at the wound do not exceed 38 to 40.degree. C., and
optimally 36 to 38.degree. C.
[0202] Examples of sources of direct or indirect electromagnetic
irradiation of the irrigant fluid and/or wound exudate at an
appropriate wavelength also include radio-frequency e.m.r. in a
range of 3 to 300 MHz, such as 10 to 100 MHz, such as 20 to 50
MHz.
[0203] Examples of preferred frequencies include microwave
frequencies, using a microwave magnetron, in a range such as 1 to
300 GHz, such as 1 to 100 GHz, e.g. 1 to 50 GHz.
[0204] It will be appreciated that at these frequencies, in the
range of microwave frequencies in particular, thermal energy is not
just transferred to the fluid by simply being absorbed by the fluid
and conducted to the wound. It is induced in the molecules in the
fluid in the wound by radiation at an optimum frequency for such
materials.
[0205] In all the above radiative heaters of the irrigant fluid
and/or wound exudate, the electromagnetic irradiation from a
radiative heater may pass into the fluid in the flow path directly,
usually through a `window` that is transparent to the relevant
wavelengths to be applied to the fluid.
[0206] Amongst those materials that are suitable are glass; carbon
fibres (which may be in a parallel array with spaces therebetween)
and carbon fabric, such as a woven layer or sheet.
[0207] These may as appropriate be made essentially of carbonised
acrylate, such as polyacrylonitrile and copolymers thereof; and
various well-known polymers.
[0208] The transmissive structures may, alternatively or
additionally, effectively be in the form of optical fibre(s) or
waveguides of conventional type, e.g., a) a tube, pipe, duct,
fibre, filament, strand or other like structure, e.g. of carbon or
the materials mentioned above, which is transparent to the relevant
wavelengths to be applied to the fluid, b) coated, enclosed or
enveloped by a coating, layer, sheet, skin or concentric tube,
pipe, duct, sheath, or casing, or other like structure, of material
on its outer face that is opaque and reflective to the relevant
wavelengths.
[0209] These may pass at any relevant position along the apparatus
flow path into the apparatus flow path where the heat is desired to
be applied.
[0210] In one embodiment, they will pass under and/or through the
backing layer of the dressing.
[0211] The transmissive structures may effectively be in the form
of optical fibre(s) formed by [0212] a) at least one inlet pipe
and/or fluid supply tube and/or at least one outlet pipe and/or
fluid offtake tube, which passes through and/or under the
wound-facing face, and is transparent or translucent to the
relevant wavelengths to be applied to the fluid in the wound, and
preferably to those that are optimum for wound healing. [0213] b)
coated, enclosed or enveloped by a coating, layer, sheet, skin or
concentric tube, pipe, duct, sheath, or casing, or other like
structure, of material on its outer face that is opaque and
reflective to the relevant wavelengths.
[0214] An advantage of such wound dressings is that these optical
fibres may also serve as diagnostic `keyholes` into the dressing to
the wound bed in order to inspect the wound and assess its status.
This is a significant advantage, in particular in chronic
wounds.
[0215] As noted above, radiative energy may be absorbed by a
component of the apparatus flow path that absorbs electromagnetic
irradiation at an appropriate wavelength, e.g. infrared and/or near
infrared and is in direct conductive contact with the irrigant
and/or wound exudate.
[0216] Thus a radiative heater may be radiatively connected to a
component of the apparatus flow path that absorbs electromagnetic
irradiation at an appropriate wavelength, e.g. infrared and/or near
infrared and is in direct conductive contact with the irrigant
and/or wound exudate, e.g. by an air gap, the component containing
a suitable absorbent and transmissive structure, e.g. an aqueous
fluid, such as a hydrogel, that conducts heat through it to the
irrigant fluid.
[0217] The temperature of the wound is generally held within a
range of temperatures such as 34 to 40, preferably 35 to 39, and
optimally 36 to 38.degree. C. at the wound bed.
[0218] However, this may not provide a system for optimum
performance of the wound healing process. It may be desirable, in
particular in chronic wound dialysis, with relatively high
concentrations of materials that are deleterious to wound healing,
that the interior of the wound dressing is more beneficially
maintained at a temperature that degrades such molecules in the
fluid in the wound, e.g. at appropriate optimum degradation
temperatures for such materials, rather than at normothermic
temperature.
[0219] Other molecules involved in wound processes that are
detrimental to wound healing include or gaseous or volatile
by-products, such as carbon dioxide.
[0220] The irrigant may be warmed to a temperature that tends to
degrade and/or outgas such molecules. The degradation or outgassing
temperature of each detrimental gas, such as carbon dioxide, in
aqueous media is either known or may readily be calculated.
[0221] Accordingly, another type of this apparatus of the invention
for irrigating, supplying thermal energy to and cleansing wounds is
provided with means for maintaining the wound at or near a
temperature that is deleterious to molecules that are detrimental
to wound healing.
[0222] As noted above, other physiologically active components of
the wound cells are beneficial in promoting wound healing and may
be stimulated by radiation on the wound under the backing
layer.
[0223] Where these are enzymes, growth factors and
anti-inflammatories, cell mitochondria and other physiologically
active components of the exudate from a wound, examples of suitable
wavelengths and intensities to apply to the fluid in the wound to
favour such materials an cell components will be known to the
skilled person.
[0224] As regards the apparatus flowpath, the means for flow
switching between supply and recirculation may take any form that
enables the wound simultaneously to be [0225] a) put into
communication with the fluid reservoir but [0226] b) closed to the
fluid recirculation tube, and [0227] c) vice versa.
[0228] Thus, if there is only one inlet pipe that passes through
and/or under the wound facing face of the wound dressing, the fluid
reservoir is connected by the fluid supply tube to the flow path
via means for flow switching as desired the into a fluid
recirculation tube or a fluid offtake tube.
[0229] In this case, the means for flow switching between supply
and recirculation may be a regulator, such as a T-valve.
[0230] This is connected in turn to two parts of a fluid
recirculation tube or a fluid offtake tube and the fluid supply
tube, such that the desired flow switching between supply and
recirculation is achieved.
[0231] If there are two or more inlet pipes, these may be connected
respectively to a fluid supply tube or fluid recirculation tube,
respectively having a first regulator and a second regulator, such
as a valve or other control device for admitting fluids into the
wound.
[0232] The desired flow switching between supply and recirculation
is achieved by respectively having the first regulator open when
the second regulator is shut, and vice versa.
[0233] The means for bleeding the flowpath may be situated in any
appropriate part of the apparatus that is in contact with the
irrigant and/or wound exudate, but is usually within the offtake
and/or recirculation tubes.
[0234] However, it is often as far downstream of and away from the
reservoir and the fluid supply tube as possible, so that it may be
used to prime the whole of the flowpath from the fluid reservoir
via the fluid supply tube.
[0235] It may be a regulator, such as a valve or other control
device, e.g. a T-valve that is turned to switch between bleed and
recirculation, for bleeding fluids from the apparatus, e.g. to a
waste reservoir, such as a collection bag.
[0236] Alternatively J flow switching between supply and
recirculation may not be desired, but rather concomitant bleeding
and/or recirculation is desired.
[0237] The latter may occur when the volume of irrigant and/or
wound exudate in recirculation is increased by continuing addition
to it of [0238] a) wound exudate, and/or [0239] b) fluid passing
from a cleansing fluid through a selectively permeable integer, for
example in a system such as a dialysis unit.
[0240] The means for bleeding the offtake and/or recirculation
tubes may then be provided in the form of a regulator, such as a
simple valve or other control device for admitting or blocking the
passage of irrigant and/or exudate through a bleed line branching
from the recirculation path.
[0241] The means for fluid cleansing may as desired be a
`single-phase system`.
[0242] In this, the circulating fluid from the wound and the fluid
reservoir passes through a self-contained system in which materials
deleterious to wound healing are removed and the cleansed fluid,
still containing materials that are beneficial in promoting wound
healing, is returned via the recirculation tube to the wound bed.
Such systems are described in further detail hereinafter in
connection with the means for fluid cleansing.
[0243] Alternatively, where appropriate it may be provided in the
form of a two-phase system, such as a dialysis unit, or a biphasic
liquid extraction unit.
[0244] In this, the circulating fluid from the wound and the fluid
reservoir passes through a system in which the fluid recirculates
in indirect or (less usually, direct) contact with a second fluid
(dialysate) phase, more usually a liquid.
[0245] Materials deleterious to wound healing are removed into the
second phase, and the cleansed fluid, still containing materials
that are beneficial in promoting wound healing, is returned via the
recirculation tube to the wound bed. Such systems are described in
further detail hereinafter in connection with the means for fluid
cleansing.
[0246] In use, typically, the means for flow switching between
supply and recirculation tubes is set to admit fluid into the wound
from the fluid reservoir but to close the wound to the fluid
recirculation tube.
[0247] Then, any means for bleeding the offtake and/or
recirculation tubes are is opened and the device for moving fluid
through the wound and means for fluid cleansing is started.
[0248] The capacity of the apparatus flow path and the flow rate of
irrigant and/or wound exudate from the wound will largely determine
whether it is appropriate to run the device to prime the apparatus
throughout the whole length of the apparatus flow path, i.e. to
displace any existing fluid reservoir (often air) from the fluid
recirculation path, and for how long it should be run.
[0249] Typically, there is a preponderance of irrigant from the
fluid reservoir over wound exudate in recirculation, so that use of
the device for moving fluid through the wound is appropriate for
this purpose.
[0250] It is allowed to run until the apparatus is primed
throughout the whole length of the apparatus flow path.
[0251] Then, typically the means for bleeding the offtake and/or
recirculation tubes is closed, and the means for flow, switching
between supply and recirculation tubes is set to close the wound to
the fluid reservoir but to admit fluid into the wound from the
fluid recirculation tube.
[0252] If the means for fluid cleansing is a two-phase system, such
as a dialysis unit, or a biphasic extraction unit, the cleansing
fluid is typically set in motion in contact with the surface of the
selectively permeable integer, for example the polymer film, sheet
or membrane. Of course, the cleansing fluid may less usually be
static, and then this step is omitted.
[0253] As noted below in more detail, the volume of irrigant and/or
wound exudate from the wound in recirculation may be increased by
continuing addition to it of [0254] a) wound exudate, and/or [0255]
b) fluid passing from a cleansing fluid through a selectively
permeable integer, for example the polymer film, sheet or membrane
of a two-phase system, such as an dialysis unit.
[0256] Additionally or alternatively, it may be desired to apply a
negative pressure to the wound by means of a device for moving
fluid through the wound and means for fluid cleansing applied to
the fluid in recirculation in the fluid recirculation tube
downstream of and away from the wound dressing.
[0257] In such case, it may be desirable to provide a system in
which concomitant bleeding and/or recirculation is possible, and to
make the necessary adjustments to maintain the desired balance of
fluid in recirculation by means of the means for bleeding the
offtake and/or recirculation tubes.
[0258] The volume of irrigant and/or wound exudate from the wound
in recirculation may be decreased by continuing loss from it of
fluid passing from a cleansing fluid through a selectively
permeable integer, for example in a system such as a dialysis
unit.
[0259] Additionally or alternatively, it may be desired to apply a
positive pressure to the wound by means of a device for moving
fluid through the wound and means for fluid cleansing applied to
the fluid in recirculation in the fluid recirculation tube upstream
of and towards the wound dressing.
[0260] The means for flow switching between supply and
recirculation may be similarly provided in a form in which
concomitant supply and/or recirculation is possible, and to make
the necessary adjustments to maintain the desired balance of fluid
in recirculation by means of the means for flow switching.
[0261] It will be appreciated that where a positive or negative
pressure is to be applied to the wound, at least one hollow body in
the recirculation flow path to and from the wound bed should have
sufficient resilience against the pressure to allow any significant
compression or decompression of the irrigant fluid to occur. In all
embodiments of the apparatus, the type and material of such bodies
(which are defined by a film, sheet or membrane) that are described
by way of example herein to be suitable for use in the present
invention will be largely capable of this function.
[0262] Thus, examples of suitable materials for bodies defined by a
film, sheet or membrane, such as inlet or offtake and/or
recirculation tubes and structures such as bags, chambers and
pouches, filled with irrigant fluid, e.g. the backing layer of the
wound dressing are suitably elastically resilient thermoplastic
materials that are potentially capable of this function when
pressure is applied in this way.
[0263] The present invention in this aspect provides several
advantages.
[0264] One is that application of a positive pressure to the wound
under the backing layer may make it possible to flood the tissue
underlying the wound with one or more physiologically active
components.
[0265] This may be effected in therapeutically active amounts, to
promote greater wound healing than by treatment with the fluid
physiologically active component(s) alone.
[0266] Such physiologically active components of the exudate that
are beneficial to wound healing may be e.g. be enzymes or other
species and may be supplied from the dialysate of a dialytic means
for fluid cleansing.
[0267] It is believed that using the apparatus for irrigating,
supplying thermal energy to and/or cleansing wounds of the present
invention cyclically the effects may be further enhanced.
[0268] Such cyclical regimens for such further enhancement may be
applied to [0269] a) the flow direction, rate, positive or negative
pressure, [0270] b) nature of the circulating fluid (such as water,
saline, etc.) and/or [0271] c) the thermal energy applied to the
wound bed over an extended period.
[0272] Circulating wound fluid aids in movement of biological
signalling molecules involved in wound healing to locations in the
wound bed that are favourable to the wound healing process and/or
to cells that would otherwise not be exposed to them, e.g. in a
highly exuding wound.
[0273] This is especially the case in those embodiments of the
apparatus of this first aspect of the present invention for
irrigating, supplying thermal energy to and/or cleansing wounds
where there is an inlet or outlet manifold from which tubules
radiate and run to the wound bed to end in openings that deliver
and collect the fluid directly from the wound bed over an extended
area.
[0274] Such materials include cytokines, enzymes, nutrients for
wound cells to aid proliferation, oxygen, and other molecules that
are beneficially involved in wound healing, such as growth factors,
and others having beneficial effects (which may be further
enhanced) in causing chemotaxis.
[0275] In all embodiments of the apparatus of this first aspect of
the present invention for irrigating, supplying thermal energy to
and/or cleansing wounds, a particular advantage is the tendency of
the wound dressing to conform to the shape of the bodily part to
which it is applied.
[0276] The wound dressing comprises a backing layer with a
wound-facing face which is capable of forming a relatively
fluid-tight seal or closure over a wound and at least one inlet
pipe for connection to a fluid supply tube or recirculation tube,
which passes through and/or under the wound-facing face, and at
least one outlet pipe for connection to a fluid offtake tube, which
passes through and/or under the wound-facing face, the point at
which the or each inlet pipe and the or each outlet pipe passes
through and/or under the wound-facing face forming a relatively
fluid-tight seal or closure.
[0277] The term `relatively fluid-tight seal or closure` is used
herein to indicate one which is fluid- and microbe-impermeable and
permits a positive or negative pressure of up to 50% atm., more
usually up to 15% atm. to be applied to the wound.
[0278] The term `fluid` is used herein to include gels, e.g. thick
exudate, liquids, e.g. water, and gases, such as air, nitrogen,
etc.
[0279] The shape of the backing layer that is applied may be any
that is appropriate to irrigating, supplying thermal energy to
and/or cleansing the wound across the area of the wound.
[0280] Examples of such include a substantially flat film, sheet or
membrane, or a bag, chamber, pouch or other structure of the
backing layer, e.g. of polymer film, which can contain the
fluid.
[0281] The backing layer may be a film, sheet or membrane, often
with a (generally uniform) thickness of up to 100 micron,
preferably up to 50 micron, more preferably up to 25 micron, and of
10 micron minimum thickness.
[0282] Its largest cross-dimension may be up to 500 mm (for example
for large torso wounds), up to 100 mm (for example for axillary and
inguinal wounds), and up to 200 mm for limb wounds (for example for
chronic wounds, such as venous leg ulcers and diabetic foot
ulcers.
[0283] Desirably the dressing is resiliently deformable, since this
may result in increased patient comfort, and lessen the risk of
inflammation of a wound.
[0284] Suitable materials for it include synthetic polymeric
materials that do not absorb aqueous fluids, such as [0285]
polyolefins, such as polyethylene e.g. high-density polyethylene,
polypropylene, copolymers thereof, for example with vinyl acetate
and polyvinyl alcohol, and mixtures thereof; [0286] polysiloxanes;
[0287] polyesters, such as polycarbonates; [0288] polyamides, e.9.
Nylon 6-6 and 6-10, and [0289] hydrophobic polyurethanes.
[0290] They may be hydrophilic, and thus also include hydrophilic
polyurethanes.
[0291] They also include thermoplastic elastomers and elastomer
blends, for example copolymers, such as ethyl vinyl acetate,
optionally or as necessary blended with high-impact
polystyrene.
[0292] They further include elastomeric polyurethane, particularly
polyurethane formed by solution casting.
[0293] Preferred materials for the present wound dressing include
thermoplastic elastomers and curable systems.
[0294] The backing layer is capable of forming a relatively
fluid-tight seal or closure over the wound and/or around the inlet
and outlet pipe(s).
[0295] However, in particular around the periphery of the wound
dressing, outside the relatively fluid-tight seal, it is preferably
of a material that has a high moisture vapour permeability, to
prevent maceration of the skin around the wound.
[0296] It may also be a switchable material that has a higher
moisture vapour permeability when in contact with liquids, e.g.
water, blood or wound exudate. This may, e.g. be a material that is
used in Smith & Nephew's Allevyn.TM., IV3000.TM. and OpSite.TM.
dressings.
[0297] The periphery of the wound-facing face of the backing layer
may bear an adhesive film, for example, to attach it to the skin
around the wound.
[0298] This may, e.g. be a pressure-sensitive adhesive, if that is
sufficient to hold the wound dressing in place in a fluid-tight
seal around the periphery of the wound facing face of the wound
dressing.
[0299] Alternatively or additionally, where appropriate a light
switchable adhesive could be used to secure the dressing in place
to prevent leakage. (A light switchable adhesive is one the
adhesion of which is reduced by photocuring. Its use can be
beneficial in reducing the trauma of removal of the dressing.)
[0300] Thus, the backing layer may have a flange or lip extending
around the proximal face of the backing layer, of a transparent or
translucent material (for which it will be understood that
materials that are listed above are amongst those that are
suitable).
[0301] This bears a film of a light switchable adhesive to secure
the dressing in place to prevent leakage on its proximal face, and
a layer of opaque material on its distal face.
[0302] To remove the dressing and not cause excessive trauma in
removal of the dressing, the layer of opaque material on the distal
face of the flange or lip extending around the proximal wound is
removed prior to application of radiation of an appropriate
wavelength to the flange or lip.
[0303] If the periphery of the wound dressing, outside the
relatively fluid-tight seal, that bears an adhesive film to attach
it to the skin around the wound, is of a material that has a high
moisture vapour permeability or is a switchable material, then the
adhesive film, if continuous, should also have a high or switchable
moisture vapour permeability, e.g. be an adhesive such as used in
Smith & Nephew's Allevyn.TM., IV3000.TM. and OpSite.TM.
dressings.
[0304] Where a vacuum, is applied to hold the wound dressing in
place in a fluid-tight seal around the periphery of the
wound-facing face of the wound dressing, the wound dressing may be
provided with a silicone flange or lip to seal the dressing around
the wound. This removes the need for adhesives and associated
trauma to the patient's skin.
[0305] Where the interior of, and the flow of irrigant and/or wound
exudate to and through, the dressing is under any significant
positive pressure, which will tend to act at peripheral points to
lift and remove the dressing off the skin around the wound.
[0306] In such use of the apparatus, it may thus be necessary to
provide means for forming and maintaining such a seal or closure
over the wound against such positive pressure on the wound, to act
at peripheral points for this purpose.
[0307] Examples of such means include light switchable adhesives,
as above, to secure the dressing in place to prevent leakage.
[0308] Since the adhesion of a light switchable adhesive is reduced
by photocuring, thereby reducing the trauma of removal of the
dressing, a film of a more aggressive adhesive may be used, e.g. on
a flange, as above.
[0309] Examples of suitable fluid adhesives for use in more extreme
conditions where trauma to the patient's skin is tolerable include
ones that consist essentially of cyanoacrylate and like tissue
adhesives, applied around the edges of the wound and/or the
proximal face of the backing layer of the wound dressing, e.g. on a
flange or lip.
[0310] Further suitable examples of such means include adhesive
(e.g. with pressure-sensitive adhesive) and non-adhesive, and
elastic and non-elastic straps, bands, loops, strips, ties,
bandages, e.g. compression bandages, sheets, covers, sleeves,
jackets, sheathes, wraps, stockings and hose, e.g. elastic tubular
hose or elastic tubular stockings that are a compressive fit over a
limb wound to apply suitable pressure to it when the therapy is
applied in this way; and inflatable cuffs, sleeves, jackets,
trousers, sheathes, wraps, stockings and hose that are a
compressive fit over a limb wound to apply suitable pressure to it
when the therapy is applied in this way.
[0311] Such means may each be laid out over the wound dressing to
extend beyond the periphery of the backing layer of the wound
dressing, and as appropriate will be adhered or otherwise secured
to the skin around the wound and/or itself and as appropriate will
apply compression (e.g. with elastic bandages, stockings) to a
degree that is sufficient to hold the wound dressing in place in a
fluid-tight seal around the periphery of the wound.
[0312] Such means may each be integral with the other components of
the dressing, in particular the backing layer.
[0313] Alternatively, it may be permanently attached or releasably
attached to the dressing, in particular the backing layer, with an
adhesive film, for example, or these components may be a
Velcro.TM., push snap or twist-lock fit with each other.
[0314] The means and the dressing may be separate structures,
permanently unattached to each other.
[0315] In a more suitable layout for higher positive pressures on
the wound, a stiff flange or lip extends around the periphery of
the proximal face of the backing layer of the wound dressing as
hereinbefore defined.
[0316] The flange or lip is concave on its proximal face to define
a peripheral channel or conduit.
[0317] It has a suction outlet that passes through the flange or
lip to communicate with the channel or conduit and may be connected
to a device for applying a vacuum, such as a pump or a piped supply
of vacuum.
[0318] The backing layer may be integral with or attached, for
example by heat sealing, to the flange or lip extending around its
proximal face.
[0319] To form the relatively fluid-tight seal or closure over a
wound that is needed and to prevent passage of irrigant and/or
exudate under the periphery of the wound facing face of the wound
dressing, in use of the apparatus, the dressing is set on the skin
around the wound.
[0320] The device then applies a vacuum to the interior of the
flange or lip, thus forming and maintaining a seal or closure
acting at peripheral points around the wound against the positive
pressure on the wound.
[0321] With all the foregoing means of attachment, and means for
forming and maintaining a seal or closure over the wound, against
positive or negative pressure on the wound at peripheral points
around the wound, the wound dressing sealing periphery is
preferably of a generally round shape, such as an ellipse, and in
particular circular.
[0322] To form the relatively fluid-tight seal or closure over a
wound and around the inlet pipe(s} and outlet pipe(s) at the point
at which they pass through and/or under the wound-facing face, the
backing layer may be integral with these other components.
[0323] The components may alternatively just be a push, snap or
twist-lock fit with each other, or adhered or heat-sealed
together.
[0324] The or each inlet pipe or outlet pipe may be in the form of
an aperture, such as a funnel, hole, opening, orifice, luer, slot
or port for connection as a female member respectively to a mating
end of a fluid recirculation tube and/or fluid supply tube
(optionally or as necessary via means for forming a tube, pipe or
hose, or nozzle, hole, opening, orifice, luer, slot or port for
connection as a male member respectively to a mating end of a fluid
recirculation tube and/or fluid supply tube (optionally or as
necessary via means for flow switching between supply and
recirculation) or a fluid offtake tube.
[0325] Where the components are integral they will usually be made
of the same material (for which it will be understood that
materials that are listed above are amongst those that are
suitable).
[0326] Where, alternatively, they are a push, snap or twist-lock
fit, the may be of the same material or of different materials. In
either case, materials that are listed above are amongst those that
are suitable for all the components.
[0327] The or each pipe will generally pass through, rather than
under the backing layer.
[0328] In such case, the backing layer may often have a rigid
and/or resiliently inflexible or stiff area to resist any
substantial play between the or each pipe and the or each mating
tube, or deformation under pressure in any direction.
[0329] It may often be stiffened, reinforced or otherwise
strengthened by a boss projecting distally (outwardly from the
wound) around each relevant tube, pipe or hose, or nozzle, hole,
opening, orifice, luer, slot or port for connection to a mating end
of a fluid recirculation tube and/or fluid supply tube or fluid
offtake tube.
[0330] Alternatively or additionally, where appropriate the backing
layer may have a stiff flange or lip extending around the proximal
face of the backing layer to stiffen, reinforce or otherwise
strengthen the backing layer. The wound dressing may not comprise
any integer under the backing layer in the wound in use, other than
the ribs or ridges mentioned herein.
[0331] However, this may not provide a system to distribute
irrigant over a sufficient functional surface area to irrigate the
wound at a practical rate to be suitable for use, in particular in
chronic wound dialysis, with relatively high concentrations of
materials that are deleterious to wound healing, it may be
advantageous to provide a system where wound irrigant and/or wound
exudate may be distributed more evenly, or pass in a more
convoluted path under the dressing over the wound bed.
[0332] Accordingly, one form of the dressing is provided with a
`tree` form of pipes, tubes or tubules that radiate from an inlet
manifold to the wound bed to end in apertures and deliver the
circulating fluid directly to the wound bed via the apertures.
Similarly, there is an outlet manifold from which tubules radiate
and run to the wound bed to end in openings and collect the fluid
directly from the wound bed.
[0333] The pipes, etc. may radiate regularly or irregularly through
the wound in use, respectively from the inlet or outlet manifold,
although regularly may be preferred. A more suitable layout for
deeper wounds is one in which the pipes, etc. radiate
hemispherically and concentrically, to the wound bed.
[0334] For shallower wounds, examples of suitable forms of such
layout of the pipes, etc. include ones in which the pipes, etc.
radiate in a flattened hemi ellipsoid and concentrically to the
wound bed.
[0335] Other suitable forms of layout of the pipes, etc. include
one which have pipes, tubes or tubules extending from the inlet
pipe(s) and/or outlet pipe(s) at the point at which they pass
through and/or under the wound-facing face of the backing layer to
run over the wound bed. These may have a blind bore with
perforations, apertures, holes, openings, orifices, slits or slots
along the pipes, etc.
[0336] These pipes, etc. then effectively form an inlet pipe
manifold that delivers the circulating fluid directly to the wound
bed or outlet pipe or collects the fluid directly from the wound
respectively.
[0337] It does so via the holes, openings, orifices, slits or slots
in the tubes, pipes, tubules, etc. over most of the wound bed under
the backing layer.
[0338] It may be desirable that the tubes, pipes or tubules are
resiliently flexible, e.g. elastomeric, and preferably soft,
structures with good conformability in the wound and the interior
of the wound dressing.
[0339] When the therapy is applied in this way, the layout of the
tubes, pipes, tubules, etc. may depend on the depth and/or capacity
of the wound.
[0340] Thus, for shallower wounds, examples of suitable forms of
such layout of the tubes, pipes, tubules, etc. include ones that
consist essentially of one or more of the tubes, etc in a
spiral.
[0341] A more suitable layout for deeper wounds when the therapy is
applied in this way may be one that comprises one or more of the
tubes, etc in a helix or spiral helix.
[0342] Other suitable layouts for shallower wounds include one
which have blind-bore, perforated inlet pipe or outlet pipe
manifolds that circulate fluid in the wound when the dressing is in
use.
[0343] One or both of these may be such a form, the other may be,
e.g. one or more straight blind-bore, perforated radial tubes,
pipes or nozzles.
[0344] Another suitable layout is one in which an inlet pipe and/or
outlet pipe manifold that delivers the circulating fluid directly
to the wound bed or collects the fluid directly from the wound
respectively via inlet and/or outlet tubes, pipes or tubules, and
the Inlet manifold and/or outlet manifold is formed by slots in
layers permanently attached to each other in a stack, and the inlet
and/or outlet tubes, pipes or tubules are formed by apertures
through layers permanently attached to each other in a stack.
[0345] As also mentioned herein, the backing layer that is applied
may be any that is appropriate to the present system of therapy and
permits a positive or negative pressure of up to 50% atm., more
usually up to 25% atm. to be applied to the wound.
[0346] It is thus often a microbe-impermeable film, sheet or
membrane, which is substantially flat, depending on any pressure
differential on it.
[0347] It often has a (generally uniform) thickness similar to such
films or sheets used in conventional wound dressings, i.e. up to
100 micron, preferably up to 50 micron, more preferably up to 25
micron, and of 10 micron minimum thickness.
[0348] The backing layer may often have a rigid and/or resiliently
inflexible or stiff area to resist any substantial play between
other components that are not mutually integral, and may be
stiffened, reinforced or otherwise strengthened, e.g. by a
projecting boss.
[0349] Such a form of dressing would not be very conformable to the
wound bed, and may effectively form a chamber, hollow or cavity
defined by a backing layer and the wound bed under the backing
layer.
[0350] It may be desirable that the interior of the wound dressing
conform to the wound bed, even for a wound in a highly exuding
state. Accordingly, one form of the dressing is provided with a
wound filler under the backing layer.
[0351] This is favourably a resiliently flexible, e.g. elastomeric,
and preferably soft, structure with good conform ability to wound
shape.
[0352] It is urged by its own resilience against the backing layer
to apply gentle pressure on the wound bed.
[0353] The wound filler may be integral with the other components
of the dressing, in particular the backing layer.
[0354] Alternatively, it may be permanently attached to them/it,
with an adhesive film, for example, or by heat-sealing, e.g. to a
flange or lip extending from the proximal face, so a not to disrupt
the relatively fluid-tight seal or closure over the) wound that is
needed.
[0355] Less usually, the wound filler is releasably attached to the
backing layer, with an adhesive film, for example, or these
components may be a push, snap or twistlock fit with each
other.
[0356] The wound filler and the backing layer may be separate
structures, permanently unattached to each other.
[0357] The wound filler may be or comprise a solid integer,
favourably a resiliently flexible, e.g. elastomeric, and preferably
soft, structure with good conformability to wound shape. Examples
of suitable forms of such wound fillers are foams formed of a
suitable material, e.g. a resilient thermoplastic. Preferred
materials for the present wound dressing include reticulated
filtration polyurethane foams with small apertures or pores.
[0358] Alternatively or additionally, it may be in the form of, or
comprise one or more conformable hollow bodies defined by a film,
sheet or membrane, such as a bag, chamber, pouch or other
structure, filled with a fluid or solid that urges it to the wound
shape.
[0359] The film, sheet or membrane, often has a (generally uniform)
thickness similar to that of films or sheets used in conventional
wound dressing backing layers.
[0360] That is, up to 100 micron, preferably up to 50 micron, more
preferably up to 25 micron, and of 10 micron minimum thickness, and
is often resiliently flexible, e.g. elastomeric, and preferably
soft.
[0361] Such a filler is often integral with the other components of
the dressing, in particular the backing layer, or permanently
attached to them/it, with an adhesive film, for example, or by
heat-sealing, e.g. to a flange.
[0362] Examples of suitable fluids contained in the hollow body or
bodies defined by a film, sheet or membrane include gases, such as
air, nitrogen and argon, more usually air, at a small positive
pressure above atmospheric; and liquids, such as water, saline.
[0363] Examples also include gels, such as silicone gels, or
preferably cellulosic gels, for example hydrophilic cross-linked
cellulosic gels, such as Intrasite.TM. cross-linked materials.
[0364] Examples also include aerosol foams, where the gaseous phase
of the aerosol system is air or an inert gas, such as nitrogen or
argon, more usually air, at a small positive pressure above
atmospheric; foams, including set aerosol foams, e.g. CaviCare.TM.
foam, and solid particulates, such as plastics crumbs.
[0365] Of course, if the backing layer is a sufficiently
conformable and/or e.g. an upwardly dished sheet, the backing layer
may lie under the wound filler, rather than vice versa.
[0366] In this type of layout, in order for the wound filler to
urge the wound dressing towards the wound bed, it will usually have
to be firmly adhered or otherwise releasably attached to the skin
around the wound. This is especially the case in those embodiments
where the wound filler and the backing layer are separate
structures, permanently unattached to each other.
[0367] In such a layout for deeper wounds when the therapy is
applied in this way, the means for such attachment may also form
and maintain a seal or closure over the wound.
[0368] Where the filler is over the backing layer, and the fluid
inlet pipe(s) and outlet pipe(s) pass through the wound-facing face
of the backing layer, they may run through or around the wound
filler over the backing layer.
[0369] One form of the dressing is provided with a wound filler
under the backing layer that is or comprises a resiliently
flexible, e.g. elastomeric, and preferably soft, hollow body
defined by a film, sheet or membrane, such as a bag, chamber, pouch
or other structure, with apertures, holes, openings, orifices,
slits or slots, or tubes, pipes, tubules or nozzles. It
communicates with at least one inlet or outlet pipe through at
least one aperture, hole, opening, orifice, slit or slot.
[0370] The fluid contained in the hollow body may then be the
circulating fluid in the apparatus.
[0371] The hollow body or each of the hollow bodies then
effectively forms an inlet pipe or outlet pipe manifold that
delivers the circulating fluid directly to the wound bed or
collects the fluid directly from the wound respectively via the
holes, openings, orifices, slits or slots, or the tubes, pipes or
hoses, etc. in the film, sheet or membrane.
[0372] When the therapy is applied in this way, the type of the
filler may also be largely determined by the depth and/or capacity
of the wound.
[0373] Thus, for shallower wounds, examples of suitable wound
fillers as a component of a wound dressing include ones that
consist essentially of one or more conformable hollow bodies
defining an inlet pipe and/or outlet pipe manifold that delivers
the circulating fluid directly to the wound bed or collects the
fluid directly from the wound.
[0374] A more suitable wound filler for deeper wounds when the
therapy is applied in this way may be one which comprises one or
more conformable hollow bodies defined by, for example a polymer
film, sheet or membrane.
[0375] The latter at least partly surround(s) a solid integer,
which may provide a system with better rigidity for convenient
handling.
[0376] The wound filler under the backing layer may effectively
form an inlet or outlet manifold with a direct connection between
the inlet pipe(s) and outlet pipe(s) at the point at which they
pass through and/or under the wound-facing face and the wound
bed.
[0377] If not, in order for aspiration and/or irrigation of the
wound bed to occur, it is appropriate for one or more bores,
channels, conduits, passages, pipes, tubes, tubules and/or spaces,
etc. to run from the point at which the fluid inlet pipe(s) and
outlet pipe(s) pass through and/or under the wound-facing face of
the backing layer through or around the wound filler under the
backing layer.
[0378] Less usually, the wound filler is an open-cell foam with
pores that may form such bores, channels, conduits, passages and/or
spaces through the wound filler under the backing layer.
[0379] Where the filler is or comprises one or more conformable
hollow bodies defined by, for example a polymer film, sheet or
membrane, it may be provided with means for admitting fluids to the
wound bed under the wound dressing.
[0380] These may be in the form of pipes, tubes, tubules or nozzles
running from the point at which the fluid inlet pipe(s) and outlet
pipe(s) pass through and/or under the wound-facing face of the
backing layer through or around the wound filler under the backing
layer.
[0381] All of the suitable layouts for shallower wounds that
comprise blind-bore, perforated inlet pipe or outlet pipe manifolds
that circulate fluid in the wound when the dressing is in use, that
are described hereinbefore, may be used under a wound filler under
the backing layer.
[0382] In brief, suitable layouts include ones where one or both
manifolds are annular or toroidal (regular, e.g. elliptical or
circular, or irregular), optionally with blind-bore, perforated
radial tubes, pipes or nozzles, branching from the annulus or
torus; and/or in a meandering, tortuous, winding, zigzag,
serpentine or boustrophedic (i.e., in the manner of a ploughed
furrow) pattern, or defined by slots in and apertures through
layers attached to each other in a stack.
[0383] The inlet and/or outlet tubes, the fluid recirculation tube
and the fluid supply tube, etc. may be of conventional type, e.g.
of elliptical or circular cross-section, and may suitably have a
uniform cylindrical bore, channel, conduit or passage throughout
their length.
[0384] Depending on the desired fluid volume flow rate of irrigant
and/or wound exudate from the wound, and the desired amount in
recirculation, suitably the largest cross-dimension of the bore may
be up to 10 mm for large torso wounds, and up to 2 mm for limb
wounds.
[0385] The tube walls should suitably thick enough to withstand any
positive or negative pressure on them.
[0386] This is the case in particular if the volume of irrigant
and/or wound exudate from the wound in recirculation is increased
by continuing addition to it of wound exudate, and/or fluid passing
from a cleansing fluid through a selectively permeable integer, for
example the polymer film, sheet or membrane of a two-phase system,
such as an dialysis unit. However, as noted below with regard to
pumps, the prime purpose of such tubes is to convey fluid irrigant
and exudate through the length of the apparatus flow path, rather
than to act as pressure vessels. The tube walls may suitably be at
least 25 micron thick.
[0387] The bore or any perforations, apertures, holes, openings,
orifices, slits or slots along the pipes, etc. or in the hollow
body or each of the hollow bodies may be of small
cross-dimension.
[0388] They may then effectively form a macroscopic and/or
microscopic filter for particulates including cell debris and
micro-organisms, whilst allowing proteins and nutrients to pass
through.
[0389] Such tubes, pipes or hoses, etc. through and/or around the
filler, whether the latter is a solid integer and/or one or more
resiliently flexible or conformable hollow bodies, are described in
further detail hereinbefore in connection with the inlet pipe(s)
and outlet pipe(s).
[0390] The whole length of the apparatus for irrigating, supplying
thermal energy to and/or cleansing wounds should be
microbe-impermeable once the wound dressing is over the wound in
use.
[0391] It is desirable that the wound dressing and the interior of
the apparatus for irrigating, supplying thermal energy to and/or
cleansing wounds of the present invention is sterile.
[0392] The fluid may be sterilised in the fluid reservoir and/or
the rest of the system in which the fluid recirculates, including
the means for fluid cleansing, by ultraviolet, gamma or electron
beam irradiation. This way, in particular reduces or eliminates
contact of internal surfaces and the fluid with any sterilising
agent.
[0393] Examples of other methods of sterilisation of the fluid also
include e.g. the use of ultrafiltration through microapertures or
micropores, e.g., of 0.22 to 0.45 micron maximum cross-dimension,
to be selectively impermeable to microbes; and fluid antiseptics,
such as solutions of chemicals, such as chlorhexidine and povidone
iodine; metal ion sources, such as silver salts, e.g. silver
nitrate; and hydrogen peroxide; although the latter involve contact
of internal surfaces and the fluid with the sterilising agent.
[0394] It may be desirable that the interior of the wound dressing,
the rest of the system in which the fluid recirculates, and/or the
wound bed, even for a wound in a highly exuding state, are kept
sterile after the fluid is sterilised in the fluid reservoir, or
that at least naturally occurring microbial growth is
inhibited.
[0395] Thus, materials that are potentially or actually beneficial
in this respect may be added to the irrigant initially, and as
desired the amount in recirculation increased by continuing
addition.
[0396] Examples of such materials include antibacterial agents
(some of which are listed above), and antifungal agents.
[0397] Amongst those that are suitable are, for example triclosan,
iodine, metronidazole, cetrimide, chlorhexidine acetate, sodium
undecylenate, chlorhexidine and iodine.
[0398] Buffering agents, such as potassium dihydrogen phosphatel
disodium hydrogen phosphate, may be added to adjust the pH, as may
local analgesics/anaesthetics, such as lidocainellignocaine
hydrochloride, xylocaine (adrenoline, lidocaine) and/or
anti-inflammatories, to reduce wound pain or inflammation or pain
associated with the dressing.
[0399] It is also desirable to provide a system in which
physiologically active components of the exudate that are
beneficial to wound healing are not removed before or after the
application of fluid cleansing.
[0400] Examples include the passive deposition of materials that
are beneficial in promoting wound healing, such as proteins, e.g.
growth factors.
[0401] This may occur at any point at least one inlet or outlet
pipe through at least one aperture, hole, opening, orifice, slit or
slot.
[0402] The fluid contained in the hollow body may the deposition of
materials that are beneficial in promoting wound healing, and
consequent coating, a) may be added to the irrigant initially, and
as desired the amount in recirculation increased by continuing
addition, or b) may be used at any point or on any integer in the
recirculation path in direct contact with the fluid, e.g. on the
means for fluid cleansing or any desired tube or pipe.
[0403] Examples of coating materials for surfaces over which the
circulating fluid passes include anticoagulants, such as heparin,
and high surface tension materials, such as PTFE, and polyamides,
which are useful for growth factors, enzymes and other proteins and
derivatives.
[0404] The apparatus of the invention for irrigating, supplying
thermal energy to and/or cleansing wounds is provided with means
for admitting fluids directly or indirectly to the wound under the
wound dressing in the form of a fluid supply tube to a fluid
reservoir.
[0405] The fluid reservoir may be of any conventional type, e.g. a
tube, bag (such as a bag typically used for blood or blood
products, e.g. plasma, or for infusion feeds, e.g. of nutrients),
chamber, pouch or other structure, e.g. of polymer film, which can
contain the irrigant fluid.
[0406] The reservoir may be made of a film, sheet or membrane,
often with a (generally uniform) thickness similar to that of films
or sheets used in conventional wound dressing backing layers, i.e.,
up to 100 micron, preferably up to 50 micron, more preferably up to
25 micron, and of 10 micron minimum thickness, and is often a
resiliently flexible, e.g. elastomeric, and preferably soft, hollow
body.
[0407] In all embodiments of the apparatus the type and material of
the tubes throughout the apparatus of the invention for irrigating,
supplying thermal energy to and/or cleansing wounds and the fluid
reservoir will be largely determined by their function.
[0408] To be suitable for use, in particular on chronic timescales,
the material should be non-toxic and biocompatible, inert to any
active components, as appropriate of the irrigant from the fluid
reservoir and/or wound exudate in the apparatus flow path, and, in
any use of a two-phase system dialysis unit, of the dialysate that
moves into the circulating fluid in the apparatus.
[0409] When in contact with irrigant fluid, it should not allow any
significant amounts of extractables to diffuse freely out of it in
use of the apparatus.
[0410] It should be sterilisable by ultraviolet, gamma or electron
beam irradiation and/or with fluid antiseptics, such as solutions
of chemicals, fluid- and microbe impermeable once in use, and
flexible.
[0411] Examples of suitable materials for the fluid reservoir
include synthetic polymeric materials, such as polyolefins, such as
polyethylene, e.g. high-density polyethylene and polypropylene.
[0412] Suitable materials for the present purpose also include
copolymers thereof, for example with vinyl acetate and mixtures
thereof. Suitable materials for the present purpose further include
medical grade poly(vinyl chloride).
[0413] Notwithstanding such polymeric materials, the fluid
reservoir will often have a stiff area to resist any substantial
play between it and components that are not mutually integral, such
as the fluid supply tube towards the wound dressing, and may be
stiffened, reinforced or otherwise strengthened, e.g. by a
projecting boss.
[0414] The device for moving fluid through the wound and means for
fluid cleansing may be any appropriate for this purpose, and may
act at any appropriate point for this purpose.
[0415] It may apply a positive or negative pressure to the wound,
although its prime purpose is to move fluid (irrigant from the
fluid reservoir and/or wound exudate through the length of the
apparatus flow path, rather than to apply a positive or negative
pressure to the wound.
[0416] If applied to the fluid in recirculation in the fluid
recirculation tube upstream of and towards the wound dressing
and/or the fluid in the fluid supply tube towards the wound
dressing (optionally or as necessary via means for flow switching
between supply and recirculation), it will usually apply positive
pressure (i.e. above-atmospheric pressure) to the wound bed.
[0417] Often the means for fluid cleansing is (most appropriately
for its purpose) downstream of the wound dressing, and provides the
highest resistance in the flow path. This is especially the case
where the means for fluid cleansing is a single-phase system, e.g.
with ultrafiltration through microapertures or micropores, thus
enhancing applied positive pressure to the wound.
[0418] Where the device is app lied to the fluid in recirculation
in the fluid recirculation tube and/or the fluid in the fluid
offtake tube downstream of and away from the wound dressing, it
will usually apply negative pressure (i.e., below-atmospheric
pressure or vacuum) to the wound bed.
[0419] Again, often the means for fluid cleansing is (most
appropriately for its purpose) downstream of the wound dressing,
and provides the highest resistance in the flow path, thus
enhancing applied negative pressure to the wound.
[0420] The following types of pump may be used as desired: [0421]
reciprocating pumps, such as: [0422] shuttle pumps--with an
oscillating shuttle mechanism to move fluids at rates from 2 to 50
ml per minute; [0423] diaphragm pumps--where pulsations of one or
two flexible diaphragms displace liquid while check valves control
the direction of the fluid flow. [0424] piston pumps--where pistons
pump fluids through check valves, in particular for positive and/or
negative pressure on the wound bed; [0425] rotary pumps, such as:
[0426] centrifugal pumps [0427] flexible impeller pumps--where
elastomeric impeller traps fluid between impeller blades and a
moulded housing that sweeps fluid through the pump housing. [0428]
progressing cavity pumps--with a cooperating screw rotor and
stator, in particular for higher-viscosity and particulate-filled
exudate; [0429] rotary vane pumps--with rotating vaned disk
attached to a drive shaft moving fluid without pulsation as it
spins. The outlet can be restricted without damaging the pump.
[0430] peristaltic pumps--with peripheral rollers on rotor arms
acting on a flexible fluid circulation tube to urge fluid current
flow in the tube in the direction of the rotor. [0431] vacuum
pumps--with pressure regulators.
[0432] The type and/or capacity of the device will be largely
determined by [0433] a) the appropriate or desired fluid volume
flow rate of irrigant and/or wound exudate from the wound, and
[0434] b) whether it is appropriate or desired to apply a positive
or negative pressure to the wound bed, and the level of such
pressure to the wound bed for optimum performance of the wound
healing process, and by factors such as) portability, power
consumption and isolation from contamination.
[0435] Such a device may also suitably be one that is capable of
pulsed, continuous, variable, reversible and/or automated and/or
programmable fluid movement. It may in particular be a pump of any
of these types.
[0436] In practice, even from a wound in a highly exuding state,
such a rate of exudate flow is only of the order of up to 75
microlitres/cm.sup.2/hr (where cm.sup.2 refers to the wound area),
and the fluid can be highly mobile (owing to the proteases
present).
[0437] Exudate levels drop and consistency changes as the wound
heals, e.g. to a level for the same wound that equates to 12.5-25
microlitres/cm.sup.2/hr.
[0438] Where materials deleterious to wound healing are removed by
a two-phase system (see below), such as a dialysis unit, fluid is
also potentially lost to the system through the means for fluid
cleansing.
[0439] This may occur, e.g. through a dialysis polymer film, sheet
or membrane which is also permeable to water, in addition to
materials deleterious to wound healing.
[0440] The balance of fluid in recirculation may thus further
decrease, but may be adjusted to minimize this undesired loss in a
routine manner as described hereinbefore.
[0441] Hence, it will be seen that the circulating fluid from the
wound will typically contain a preponderance of irrigant over wound
exudate in recirculation from the fluid reservoir.
[0442] The type and/or capacity of the device will thus be largely
determined in this respect by the appropriate or desired fluid
volume flow rate of irrigant, rather than that of exudate, from the
wound.
[0443] In practice, the `normal` irrigation rate will be different
for each dressing size, but the rate of flow of total irrigant
and/or wound exudate will be of the order of 1 to 10 ml/cm.sup.2/24
hour, where the cm2 refers to the wound area, e.g. 1 to 5
ml/cm.sup.2/24 hour, such as 1 to 3.5 ml hr.
[0444] If wound temperatures a) above normothermic temperature are
required, e.g. a temperature at or above 42.degree. C., e.g. for
the degradative removal of deleterious materials, or b) below
normothermic temperatures are required, e.g. 32.degree. C. to
35.degree. C., e.g. for decreasing the inflammation of a wound, the
necessary target temperature at the heater outlet may be achieved
by adjusting parameters, such as increasing or decreasing the
linear flow rate of the irrigant and/or any heat exchanger fluid or
the temperature of the heater in a routine manner known to the
skilled person.
[0445] It is desirable that the interior of the wound dressing and
the rest of the system in which the fluid recirculates be flushed
cyclically before and/or after use in treatment to cleanse them,
and it is convenient that this is effected by the device for moving
fluid through the wound and means for fluid cleansing. Accordingly,
the device may deliver a flush cycle at an irrigation rate
substantially greater than the `normal` rate; this could typically
be up to 650 ml/hr for the largest dressing size. It may be
desirable therefore that the apparatus adjusts the heat energy
delivered to the wound in accordance with the selected
irrigant/exudate flow rates at any moment in time.
[0446] The volume of irrigant and/or wound exudate in recirculation
may vary over a wide range, but will typically be e.g. 1 to 81 (for
example for large torso wounds), 30 to 300 ml (for example for
axillary and inguinal wounds), and 200 to 1500 ml for limb wounds
when the therapy is applied in this way.
[0447] In practice, suitable pressures are of the order of up to
25% atm. such as up to 10% atm. positive or negative pressure on
the wound bed, the apparatus being operated as a closed
recirculating system.
[0448] The higher end of these ranges are potentially more suitable
for hospital use, where relatively high % pressures and/or vacua
may be used safely under professional supervision.
[0449] The lower end is potentially more suitable for home use,
where relatively high % pressures and/or vacua cannot be used
safely without professional supervision, or for field hospital
use.
[0450] The device may be a peristaltic pump or diaphragm pump, e.g.
preferably a small portable diaphragm or peristaltic pump. These
are preferred types of pump, in order in particular to reduce or
eliminate contact of internal surfaces and moving parts of the pump
with (chronic) wound exudate, and for ease of cleaning.
[0451] It may suitably be one that applies positive pressure to the
wound and/or the means for fluid cleansing.
[0452] A preferred pump when the applied pressure is positive is a
peristaltic pump, e.g. a small, portable peristaltic pump, mounted
upstream of the means for fluid cleansing.
[0453] Where the pump is a peristaltic pump, this may be e.g. an
Instech Model P720 miniature peristaltic pump, with a flow rate: of
0.2-180 ml/hr and a weight of <0.5 k. This is potentially useful
for home and field hospital use.
[0454] The pump may suitably be one that applies negative pressure
to the wound and/or the means for fluid cleansing.
[0455] A preferred pump when the applied pressure is negative is a
diaphragm pump, e.g. a small, portable diaphragm pump, mounted
downstream of the dressing or the means for fluid cleansing.
[0456] Where the pump is a diaphragm pump, and preferably a small
portable diaphragm pump, the one or two flexible diaphragms that
displace liquid may each be, for example a polymer film, sheet or
membrane, that is connected to means for creating the pulsations.
This may be provided in any form that is convenient, inter alia as
a piezoelectric transducer, a core of a solenoid or a ferromagnetic
integer and coil in which the direction of current flow alternates,
a rotary cam and follower, and so on.
[0457] The outlet from the dressing passes to the means for fluid
cleansing for removal of materials deleterious to wound heating
from wound exudate, and in turn to the fluid recirculation
tube(s).
[0458] The apparatus of the invention for irrigating, supplying
thermal energy to and/or cleansing wounds is provided with means
for fluid cleansing, which may be [0459] a) a single-phase system,
such as an ultrafiltration unit, or a chemical absorption and/or
adsorption unit; or [0460] b) a two-phase system, such as a
dialysis unit, or a biphasic extraction unit.
[0461] In the former, circulating fluid from the wound and the
fluid reservoir passes through a self-contained system in which
materials deleterious to wound healing are removed and the cleansed
fluid, still containing materials that are beneficial in promoting
wound healing are returned to the wound.
[0462] The single-phase system may be of any conventional type.
[0463] Examples of such include an ultrafiltration unit, such as a
one in which the cleansing integer is a filter for materials
deleterious to wound healing, for example a high throughput, low
protein-binding polymer film, sheet or membrane which is
selectively impermeable to materials deleterious to wound healing,
which are removed and the cleansed fluid, still containing
materials that are beneficial in promoting wound healing is passed
by it.
[0464] The membrane may preferably be of a hydrophilic polymeric
material, such as a cellulose acetate-nitrate mixture,
polyvinylidene chloride, and, for example hydrophilic
polyurethane.
[0465] Examples of less preferred materials include hydrophobic
materials also including polyesters, such as polycarbonates, PTFE,
and polyamides, e.g. nylon 6-6 and 6-10, and hydrophobic
polyurethanes, and quartz and glass fibre.
[0466] It has microapertures or micropores, the maximum
cross-dimension of which will largely depend on the species that
are to be selectively removed in this way and those to which it is
to be permeable.
[0467] The former may be removed with microapertures or micropores,
e.g. typically with a maximum cross-dimension in the range of 20 to
700 micron, e.g. 20 to 50 nm (for example for undesired proteins),
50 to 100 nm, 100 to 250 nm, 250 to 500 nm and 500 to 700 nm.
[0468] The filter integer may be a flat sheet or a membrane of a
polymeric material in a more convoluted form, e.g. in the form of
elongate structure, such as pipes, tubules, etc.
[0469] The system may be a chemical adsorption unit, for example
one in which a particulate, such as a zeolite, or a layer, e.g. of
a functionalized polymer has sites on its surface that are capable
of removing materials deleterious to wound healing on passing the
circulating fluid from the wound and the fluid reservoir over
them.
[0470] The materials may be removed, e.g. by destroying or binding
the materials that are deleterious to wound healing, by, for
example chelators and/or ion exchangers, degraders, which may be
enzymes.
[0471] Examples of such also include less specific chemical
adsorption units, for example one in which a physical absorbent,
such as activated carbon or a zeolite, has non-specific sites on
its surface that are capable of removing materials deleterious to
wound healing on passing the circulating fluid from the wound and
the fluid reservoir over them.
[0472] The cleansing integer, for example the polymer film, sheet
or other chemical adsorption means, etc should of course be capable
of removing materials deleterious to wound healing at a practical
rate for a given capacity of the apparatus flow path and the flow
rate of irrigant.
[0473] In the two-phase system, circulating fluid from the wound
and the fluid reservoir in indirect or (less usually, direct)
contact with a second fluid (dialysate) phase, more usually a
liquid.
[0474] Thus, in one form, a biphasic liquid extraction unit, the
second fluid phase is (usually) a liquid that is immiscible with
the circulating fluid from the dressing, over a surface of which
the circulating fluid passes in direct contact with the cleansing
fluid. Materials deleterious to wound healing are removed into the
dialysate, and the cleansed fluid, still containing materials that
are beneficial in promoting wound healing, is returned via the
recirculation tube to the wound bed.
[0475] Examples of such means for fluid cleansing include those
wherein the second fluid (dialysate) phase is perfluorodecalin and
like materials.
[0476] Alternatively, where appropriate it may be provided in a
form in which the two fluids (recirculation fluid and dialysate)
are separated by a significantly two-dimensional integer, for
example a polymer film, sheet or membrane or hollow fibre or
filament that is permeable to materials in the circulating fluid in
the apparatus.
[0477] Again, materials deleterious to wound healing are removed
into the dialysate, and the cleansed fluid, still containing
materials that are beneficial in promoting wound healing, is
returned via the recirculation tube to the wound bed.
[0478] In either form in which the two-phase system, such as a
dialysis unit, is provided, in use typically the dialysate moves
past the circulating fluid in the apparatus in a co- or preferably
counter-current direction.
[0479] Pumps, such as peristaltic pumps, and/or valves control the
direction of the two fluid flows.
[0480] However, the cleansing fluid may less usually be static,
although this may not provide a system with sufficient (dynamic)
surface area to remove materials deleterious to wound healing from
wound exudate at a practical rate.
[0481] Typical dialysate flow rates in a dialytic means for flu id
cleansing in the present apparatus for irrigating, supplying
thermal energy to and/or cleansing wounds are those used in the
conventional type of two-phase system, such as a dialysis unit for
systemic therapy.
[0482] The integer may be a film, sheet or membrane, often of the
same type, and of the same (generally uniform) thickness, as those
used in conventional two-phase system, such as a dialysis unit for
systemic therapy.
[0483] The film, sheet or membrane may be substantially flat, and
depending on any pressure differential across it may require other
materials on or in it to stiffen, reinforce or otherwise strengthen
it.
[0484] However, this may not provide a system with sufficient
functional surface area to remove materials deleterious to wound
healing from wound exudate at a practical rate.
[0485] The surface area of any such film, sheet or membrane may be
suitably be no less than 50 mm.sup.2, such 100 mm.sup.2 to 1
m.sup.2, e.g. 500 to 25000 mm.sup.2.
[0486] To be suitable for use, in particular in chronic wound
dialysis, with relatively high concentrations of materials that are
deleterious to wound healing, it may therefore be advantageous to
provide a system in which the film, sheet or membrane of a
polymeric material is in a more convoluted form.
[0487] This may be in the form of elongate structures, such as
pipes, tubes hollow fibres or filaments or tubules of a round
cross-section, e.g. elliptical or circular, e.g. in a parallel
array with spaces therebetween.
[0488] The wound irrigant and/or wound exudate may recirculate
through the inside and the cleansing fluid may pass into the spaces
between adjacent pipes, tubes or tubules in a co- or preferably
counter-current direction, or vice versa.
[0489] Again, materials deleterious to wound healing are removed
into the dialysate, and the cleansed fluid, still containing
materials that are beneficial in promoting wound healing, is
returned via the recirculation tube to the wound.
[0490] Where the means for fluid cleansing is a two-phase system,
e.g. in the form of a dialysis unit, or a biphasic extraction unit,
the circulating fluid from the wound and the fluid reservoir passes
across one surfaces of a significantly two-dimensional integer, for
example a polymer film, sheet or membrane which is selectively
permeable to materials deleterious to wound healing.
[0491] These are removed by passing a cleansing fluid across the
other surface of the integer. The integer may be a film, sheet or
membrane that is selectively permeable to the foregoing materials
deleterious to wound healing.
[0492] These as above include oxidants, such as free radicals, e.g.
peroxide and superoxide; iron II and iron III; all involved in
oxidative stress on the wound bed; proteases, such as serine
proteases, e.g. elastase, trypsin; chymotrypsin and thrombin;
cysteine protease inhibitors; matrix metalloproteases, e.g.
collagenase; and carboxyl (acid) proteases; endotoxins, such as
lipopolysaccharides; redox-sensitive genes that are deleterious to
wound healing; autoinducer signalling molecules, such as homoserine
lactone derivatives, e.g. oxo-alkyl derivatives; inhibitors of
angiogenesis such as thrombospondin-1 (TSP-1), plasminogen
activator inhibitor, or angiostatin (plasminogen fragment)
pro-inflammatory cytokines such as tumour necrosis factor alpha
(TNF.alpha.) and interleukin 1 beta (IL-1.beta.); and
inflammatories, such as lipopolysaccharides, and e.g.
histamine.
[0493] Examples of suitable materials for the film, sheet or
membrane (typically in the form of conformable hollow bodies
defined by the film, sheet or membrane, such as the structures
described hereinbefore) include natural and synthetic polymeric
materials.
[0494] The membrane may be of one or more hydrophilic polymeric
materials, such as a cellulose derivative, e.g. regenerated
cellulose, a cellulose mono-, di- or triesters, such as cellulose
mono-, di- or tri-acetate, benzyl cellulose and Hemophan, and
mixtures thereof.
[0495] Examples of other materials include hydrophobic materials,
such as aromatic polysulphones, polyethersulphones,
polyetherether-sulphones, polyketones, polyetherketones and
polyetherether-ketones, and sulphonated derivatives thereof, and
mixtures thereof.
[0496] Examples of other materials include hydrophobic materials,
such as polyesters, such as polycarbonates and polyactimides, e.g.
Nylon 6-6 and 6-10; polyacrylates, including, e.g. poly(methyl
methacrylate), polyacrylonitrile and copolymers thereof, for
example acrylonitrile-sodium metallosulphonate copolymers; and
poly(vinylidene chloride).
[0497] Suitable materials for the present membranes include
thermoplastic polyolefins, such as polyethylene e.g. high-density
polyethylene, polypropylene, copolymers thereof, for example with
vinyl acetate and polyvinyl alcohol, and mixtures thereof.
[0498] The dialysis membrane should have a molecular weight cut off
(MWCO) chosen to allow selective perfusion of species deleterious
to wound healing that have been targeted for removal from the
wound. For example, perfusion of the serine protease elastase
(molecular weight 25900 Dalton) would require a membrane with
MWCO>25900 Dalton. The MWCO threshold can be varied to suit each
application between 1 and 3000000 Dalton.
[0499] Preferably, the MWCO should be as close as possible to this
weight to exclude interference by larger competitor species.
[0500] For example, such a membrane with MWCO>25900 Dalton does
not allow any significant amounts of the antagonist to elastase,
alpha-1-antitrypsin (AAT) (molecular weight 54000 Dalton), which
occurs naturally in wounds, to diffuse freely out of the wound
fluid into the dialysate. The inhibitor, which is beneficial in
promoting chronic wound healing, remains in contact with the wound
bed, and can act beneficially on it, whilst the elastase that is
deleterious to wound healing is removed.
[0501] Such use of the present apparatus is, e.g. favourable to the
wound healing process in chronic wounds, such as diabetic foot
ulcers, and especially decubitus pressure ulcers.
[0502] As noted hereinafter, antagonists, for example degrading
enzymes, or sequestrating agents for elastase on the dialysate side
of the membrane, may be used to enhance the removal of this
protease from wound exudate.
[0503] Where it is desired to remove several different materials
that are deleterious to wound healing, it may be advantageous to
provide a system of modules in series, each of which removes a
different material.
[0504] This allows incompatible cleansing materials to be used on
the same fluid and/or wound exudates.
[0505] Preferably any such system is a conventional automated,
programmable system which can cleanse the wound irrigant and/or
wound exudate with minimal supervision.
[0506] As noted above in more detail, fluid passes from a cleansing
fluid through a selectively permeable integer.
[0507] This may be the typical permeable polymer film, sheet or
membrane of a two-phase system, such as a dialysis unit.
[0508] Additionally, solutes or disperse phase species will pass
from the dialysate into the irrigant and/or wound exudate through
the dialysis polymer film, sheet or membrane.
[0509] This property may be used to perfuse materials beneficial to
wound healing into the irrigant and/or exudate from a
dialysate.
[0510] In this less conventional type of infusion feed, a broad
spectrum of species will usually pass into the exudate and/or
irrigant fluid from the dialysate.
[0511] These include ionic species, such as bicarbonate; vitamins,
such as ascorbic acid (vitamin C) and vitamin E, and stable
derivatives thereof, and mixtures thereof; to relieve oxidative
stress on the wound bed; pH buffering agents, such as potassium
dihydrogen phosphatel disodium hydrogen phosphate, local
analgesics/anaesthetics, such as lidocaine/lignocaine hydrochloride
and xylocaine (adrenoline lidocaine) and/or anti-inflammatories, to
reduce wound pain or inflammation or pain associated with the
dressing nutrients to aid proliferation of wound cells, such as
amino acids, sugars, low molecular weight tissue building blocks
and trace elements; and other cell culture medium species; and
gases, such as air, nitrogen, oxygen and/or nitric oxide.
[0512] For the purposes of fluid cleansing in the apparatus of the
present invention, both the single-phase system, such as an
ultrafiltration unit, and two-phase system, such as a dialysis
unit, may have captive (non-labile, insoluble and/or immobilised)
species such as the following.
[0513] These are bound to an insoluble and/or immobilised)
substrate over and/or through which the irrigant and/or wound
exudate from, the wound dressing passes in turn to the fluid
recirculation tube(s): antioxidants and free radical scavengers,
such as 3-hydroxytyramine (dopamine), ascorbic acid (vitamin C),
vitamin E and glutathione, and stable derivatives thereof, and
mixtures thereof; to relieve oxidative stress on the wound bed;
metal ion chelators and/or ion exchangers, such as transition metal
ion chelators, such as iron III chelators (Fe III is involved in
oxidative stress on the wound bed), such as desferrioxamine (DFO),
3-hydroxytyramine (dopamine); iron III reductants; protease
inhibitors, such as TIMPs and alpha 1-antitrypsin (AAT); serine
protease inhibitors, such as 4-(2-aminoethyl)-benzene sulphonyl
fluoride (AEBSF, PefaBloc) and N.alpha.-p-tosyl-L-lysine
chloro-methyl ketone (TLCK) and
.epsilon.-aminocaproyl-p-chlorobenzylamide; cysteine protease
inhibitors; matrix metalloprotease inhibitors; and carboxyl (acid)
protease inhibitors; sacrificial redox materials that are
potentially or actually beneficial in promoting wound healing, by
the removal of materials that trigger the expression into wound
exudate of redox-sensitive genes that are deleterious to wound
healing; autoinducer signalling molecule degraders, which may be
enzymes; and anti-inflammatory materials to bind or destroy
lipopolysaccharides, e.g. peptidomimetics
[0514] Other physiologically active components of the exudate that
are deleterious to wound healing may be removed in this way.
[0515] These may be removed with suitable chelators and/or ion
exchangers, degraders, which may be enzymes, or other species.
[0516] The following types of functionalized substrate has sites on
its surface that are capable of removing materials deleterious to
wound healing on passing the circulating fluid from the wound and
the fluid reservoir over them:
heterogeneous resins, for example silica-supported reagents such
as: [0517] metal scavengers, [0518]
3-(diethylenetriamino)propyl-functionalized silica gel [0519]
2-(4-(ethylenediamino)benzene)ethyl-functionalized silica gel
[0520] 3-(mercapto)propyl-functionalized silica gel [0521]
3-(1-thioureido)propyl-functionalized silica gel [0522] triamine
tetraacetate-functionalized silica gel or electrophilic scavengers,
[0523] 4-carboxybutyl-functionalized silica gel [0524] 4-ethyl
benzenesulfonyl chloride-functionalized silica gel [0525] propionyl
chloride-functionalized silica gel [0526]
3-(isocyano)propyl-functionalized silica gel [0527]
3-(thiocyano)propyl-functionalized silica gel [0528] 3-(2-succinic
anhydride)propyl-functionalized silica gel [0529]
3-(maleimido)propyl-functionalized silica gel or nucleophilic
scavengers, [0530] 3-aminopropyl-functionalized silica gel [0531]
3-(ethylenediamino)-functionalized silica gel [0532]
2-(4-(ethylenediamino)propyl-functionalized silica gel [0533]
3-(diethylenetriamino)propyl-functionalized silica gel [0534]
4-ethyl-benzenesulfonamide-functionalized silica gel [0535]
2-(4-toluenesulfonyl hydrazino)ethyl-functionalized silica gel
[0536] 3-(mercapto)propyl-functionalized silica gel [0537]
dimethylsiloxy-functionalized silica gel or base or acid scavengers
[0538] 3-(dimethylamino)propyl-functionalized silica gel [0539]
3-(1,3,4,6,7,8-hexahydro-2H-pyrimido-[1,2-.alpha.]pyrimidino)propyl-funct-
ionalized silica gel [0540] 3-(1-imidazol-1yl)propyl-functionalized
silica gel [0541] 3-(1-morpholino)propyl-functionalized silica gel
[0542] 3-(1-piperazino)propyl-functionalized silica gel [0543]
3-(1-piperidino)propyl-functionalized silica gel [0544]
3-(4,4'-trimethyldipiperidino)propyl-functionalized silica gel
[0545] 2-(2-pyridyl)ethyl-functionalized silica gel [0546]
3-(trimethylammonium)propyl-functionalized silica gel or the
reagents, [0547] 3-(1-cyclohexylcarbodiimido)propyl-functionalized
silica gel [0548] TEMPO-functionalized silica gel [0549]
2-(diphenylphosphino)ethyl-functionalized silica gel [0550]
2-(3,4-cyclohexyldiol)propyl-functionalized silica gel [0551]
3-(glycidoxy)propyl-functionalized silica gel [0552]
2-(3,4-epoxycyclohexyl)propyl-functionalized silica gel [0553]
1-(allyl)methyl-functionalized silica gel [0554]
4-bromopropyl-functionalized silica gel [0555]
4-bromophenyl-functionalised silica gel [0556]
3-chloropropyl-functionalized silica gel [0557] 4-benzyl
chloride-functionalized silica gel [0558]
2-(carbomethoxy)propyl-functionalized silica gel [0559]
3-(4-nitrobenzamido)propyl-functionalized silica gel [0560]
3-(ureido)propyl-functionalized silica gel [0561] or any
combinations of the above.
[0562] The use of such captive (non-labile, insoluble and/or
immobilised) species, such as the foregoing, bound to an insoluble
and immobilised) substrate over and/or through which the irrigant
and/or wound exudate from, the wound dressing passes has been
described hereinbefore as suitable for the means for fluid
cleansing.
[0563] However, they may additionally, where appropriate, be used
in any part of the apparatus that is in contact with the irrigant
and/or wound exudate, but often within the dressing, for removal of
materials deleterious to wound healing from wound.
[0564] A backing layer in the wound dressing with ribs or ridges
may be used to assist in channeling fluid across a larger area over
a longer dwell time, and hence improve the cleansing of the
irrigant in the wound dressing.
[0565] The means for fluid cleansing may additionally, where
appropriate, comprise one or more macroscopic and/or microscopic
filters.
[0566] These are to retain particulates, e.g. cell debris and
micro-organisms, allowing proteins and nutrients to pass
through.
[0567] Alternatively, a less conventional type of two-phase system
(see above), such as a dialysis unit, may be used as the means for
fluid cleansing. In this type, the dialysis polymer film, sheet or
membrane is not an integer selectively permeable to materials
deleterious to wound healing, such as proteases, such as serine
proteases, e.g. elastase, trypsin; chymotrypsin and thrombin;
cysteine protease inhibitors; matrix metalloproteases, e.g.
collagenase; and carboxyl (acid) proteases; endotoxins, such as
lipopolysaccharides; inhibitors of angiogenesis such as
thrombospondin-1 (TSP-1), plasminogen activator inhibitor, or
angiostatin (plasminogen fragment); pro-inflammatory cytokines such
as tumour necrosis factor alpha (TNF.alpha.) and interleukin 1 beta
(IL-1.beta.); and oxidants, such as free radicals, e.g., peroxide
and superoxide; metal ions, e.g. iron II and iron III; all involved
in oxidative stress on the wound bed.
[0568] It will however also permit components of the exudate from a
wound and/or irrigant fluid that may be larger or smaller
molecules, but are beneficially involved in wound healing to pass
into and through it.
[0569] In the dialysate, or preferably in one or more solid
structural integers with at least one surface in contact with the
dialysate, in the means for fluid cleansing, there are one or more
materials that can remove materials deleterious to wound healing
from wound exudate, by being antagonists to such species, for
example enzymes or others, such as protease inhibitors, such as
serine protease inhibitors, such as 4-(2-aminoethyl)-benzene
sulphonyl fluoride (AEBSF, PefaBloc) and N.alpha.-p-tosyl-L-lysine
chloromethyl ketone (TLCK) and
.epsilon.-aminocaproyl-p-chlorobenzylamide; cysteine protease
inhibitors; matrix metalloprotease inhibitors; and carboxyl (acid)
protease inhibitors; peroxide inhibitors, such as catalase; binders
and/or degraders, such as anti-inflammatory materials to bind or
destroy lipopolysaccharides, e.g. peptidomimetics; anti-oxidants,
such as 3-hydroxytyramine (dopamine), ascorbic acid (vitamin C),
vitamin E and glutathione, and stable derivatives thereof, and
mixtures thereof; to relieve oxidative stress on the wound bed; and
chelators and/or ion exchanges, such as desferrioxamine (DFO),
3-hydroxytyramine (dopamine).
[0570] They further include peptides (including cytokines, e.g.
bacterial cytokines, such as .alpha.-amino-.gamma.-butyrolactone
and L-homocarnosine); and sacrificial redox materials that are
potentially or actually beneficial in promoting wound healing, such
as iron III reductants; and/or remove materials that trigger the
expression into wound exudate of redox-sensitive genes, by
degrading them; and other physiologically active components.
[0571] In use of the two-phase system dialysis unit, of this less
conventional type, a broad spectrum of species will usually pass
into the dialysate from the exudate.
[0572] Some (mainly ionic) species will pass from the dialysate
into the irrigant and/or wound exudate through the dialysis polymer
film, sheet or membrane that is not very selectively permeable to
materials deleterious to wound healing.
[0573] The components of the exudate from a wound and/or irrigant
fluid will diffuse freely to and fro through it.
[0574] If (preferably) none of the dialysate is voided to waste,
e.g. to a collection bag, a steady state concentration equilibrium
is eventually set up between the dialysate and the irrigant and/or
wound exudate, which is `topped up` from the wound dressing.
[0575] Circulating, wound fluid aids in the quicker attainment of
this equilibrium of materials beneficial in promoting wound
healing.
[0576] It also returns them to the site where they can be
potentially of most benefit, i.e. the wound bed.
[0577] The target materials deleterious to wound healing also pass
into the dialysate from the exudate through the dialysis polymer
film, sheet or membrane that is not very selectively permeable to
materials deleterious to wound healing.
[0578] Unlike the other components of the exudate from a wound
and/or irrigant fluid, the target materials deleterious to wound
healing come into contact with the dialysate, or preferably with
one or more solid structural integers with at least one surface in
the, dialysate, and are removed by the appropriate antagonists,
binders and/or degraders, chelators and/or ion exchangers and redox
agents, etc.
[0579] The cleansed fluid, still containing some materials that are
beneficial in promoting wound healing, is returned to the
recirculation tube.
[0580] Unlike the other components of the exudate from a wound
and/or irrigant fluid the target materials are constantly removed
from the dialysate, very little of these species will pass from the
dialysate, into the irrigant and/or wound exudate, and a steady
state concentration equilibrium is not set up even if the species
are constantly `topped up` from the wound dressing.
[0581] It is believed that circulating wound fluid aids in removal
from recirculation of the materials deleterious to wound healing
from wound exudate, whilst retaining, materials that are beneficial
in promoting wound healing in contact with the wound.
[0582] A particular advantage of this form of the two-phase system
is where a material that can remove materials deleterious to wound
healing from wound exudate is (cyto)toxic or bioincompatible, or
not inert to any components that are beneficial in promoting wound
healing.
[0583] The system does not allow any significant amounts of
antagonist to diffuse freely out of the dialysate into the irrigant
fluid. The active material can act beneficially on the fluid
however.
[0584] The film sheet or membrane is preferably a dialysis membrane
of molecular weight cut off (MWCO) chosen to allow perfusion of
species targeted for sequestration or destruction.
[0585] For example, sequestration of the serine protease elastase
(molecular weight 25900 Dalton) would require a membrane with
MWCO>25900 Dalton.
[0586] The MWCO threshold can be varied to suit each application
between 1 and 3000000 Dalton. Preferably, the MWCO should be as
close as possible to this weight to exclude sequestering
interference by larger competitor species.
[0587] Both the single-phase system, such as an ultrafiltration
unit, and two-phase system, such as a dialysis unit, may be in
modular form that is relatively easily demountable from the
apparatus of the invention. The system may suitably comprise one or
more such modules.
[0588] The conduits through which respectively [0589] a) the
irrigant and/or wound exudate passes from the wound dressing and
[0590] b) the cleansed fluid, still containing materials that are
beneficial in promoting wound healing, is returned to the
recirculation tube, and [0591] c) (in the case where the means is
provided in the form of a two-phase system, such as an dialysis
unit) through which the cleansing fluid enters and exits the means
preferably have means for, on module disconnection and withdrawal,
[0592] i) switching off the flow and [0593] ii) providing an
immediate fluid-tight seal or closure over the ends of the conduits
and the cooperating tubes in the rest of the apparatus of the
invention so exposed, to prevent continuing passage of irrigant
and/or exudate and cleansed fluid, and cleansing fluid.
[0594] The apparatus of the invention for irrigating, supplying
thermal energy to and/or cleansing wounds is provided with means
for bleeding the offtake and/or recirculation tubes, such as a
regulator, such as a valve or other control device for bleeding
fluids from the wound.
[0595] The device for moving fluid through the wound and means for
fluid cleansing is used to move irrigant to the wound dressing and
apply the desired positive or negative pressure on the wound
bed.
[0596] The desired balance of fluid in recirculation tube will
typically be regulated by means of [0597] a) the means for bleeding
the offtake and/or recirculation tubes, [0598] b) the means for
flow switching between supply and recirculation, and/or [0599] c)
the means for moving fluid over the wound bed and through the means
for fluid cleansing, as appropriate.
[0600] Thus, e.g. if [0601] a) the apparatus for irrigating,
supplying thermal energy to and/or cleansing wounds is a
single-phase system, such as an ultrafiltration unit, [0602] b) the
wound is not in a highly exuding state and [0603] c) it is not
appropriate or desired to admit fluid into the wound from the fluid
reservoir, there is no or negligible change in the balance of fluid
in recirculation.
[0604] Once it has been primed throughout, e.g. to the desired
positive or negative pressure on the wound bed, the apparatus may
be operated as a closed recirculating system.
[0605] The means for flow switching between supply and
recirculation tubes is set to close the wound to the fluid
reservoir via the fluid supply tube, and the means for bleeding the
offtake and/or recirculation tubes are also closed.
[0606] If [0607] a) the apparatus for irrigating, supplying thermal
energy to and/or cleansing wounds is a single-phase system, such as
an ultrafiltration unit, [0608] b) the wound is in a highly exuding
state and/or c} it is appropriate or desired to admit fluid into
the wound from the fluid reservoir, there is a positive change in
the balance of fluid in recirculation.
[0609] Once it has been primed throughout, e.g. to the desired
positive or negative pressure on the wound bed, the apparatus
cannot be operated as a closed recirculating system, without the
pressure to the wound bed increasing, possibly undesirably.
[0610] The means for bleeding the offtake and/or recirculation
tubes must be opened to some extent to relieve positive pressure on
the wound bed. The bleed-off may be voided to waste, e.g. to a
collection bag.
[0611] Materials that are beneficial in promoting wound healing may
be lost to the site where they can be potentially of most benefit,
i.e. the wound bed, when the therapy is applied in this way.
[0612] However, the balance of fluid in recirculation may be
routinely adjusted to minimize this undesired loss.
[0613] The factors that determine the balance of fluid in
recirculation in an apparatus with a two-phase system means for
fluid cleansing in the form of a dialysis unit, or a biphasic
extraction unit have been described in detail hereinbefore in
connection with the operation of the apparatus. It is sufficient to
note here that at some point after steady state recirculation
established through the length of the apparatus flow path, it may
be necessary that any bleed valve is opened, if overall the fluid
level is increasing by transfer from the dialysate to an
undesirable extent.
[0614] Other combinations, and the necessary adjustments to
maintain the desired balance of fluid in recirculation tube by
means of [0615] a) the means for bleeding the offtake and/or
recirculation tubes, [0616] b) the means for flow switching between
supply and recirculation, and/or [0617] c) the means for moving
fluid will be apparent to the skilled person.
[0618] The outlet from the means for bleeding the offtake and/or
recirculation tubes may be collected and monitored and used to
diagnose the status of the wound and/or its exudate.
[0619] The waste reservoir may be of any conventional type, e.g. a
tube, bag (such as a bag typically used as an ostomy bag), chamber,
pouch or other structure, e.g. of polymer film, which can contain
the irrigant fluid that has been bled off. In all embodiments of
the apparatus, the type and material of the waste reservoir will be
largely determined by its function. To be suitable for use, the
material need only be fluid-impermeable once in use, and
flexible.
[0620] Examples of suitable materials for the fluid reservoir
include synthetic polymeric materials, such as polyolefins, such as
poly (vinylidene chloride).
[0621] Suitable materials for the present purpose also include
polyethylene, e.g. high density polyethylene, polypropylene,
copolymers thereof, for example with vinyl acetate and mixtures
thereof.
[0622] In a second aspect of the present invention there is
provided a conformable wound dressing, characterized in that it
comprises a backing layer with a wound-facing face which is capable
of forming a relatively fluid-tight seal or closure over a wound
and has at least one inlet pipe for connection to a fluid supply
tube, which passes through and/or under the wound-facing face, and
at least one outlet pipe for connection to a fluid offtake tube,
which passes through and/or under the wound-facing face, the point
at which the or each inlet pipe and the or each outlet pipe passes
through and/or under the wound-facing face forming a relatively
fluid-tight seal or closure over the wound, the dressing having
means for supplying thermal energy to the fluid in the wound.
[0623] The dressing is advantageously provided for use in a
bacteria-proof pouch. Examples of suitable forms of such wound
dressings are as described by way of example hereinbefore.
[0624] It is an object of the present invention [0625] a) obviate
at least some of the disadvantages of known aspiration and/or
irrigation therapies, and [0626] b) provide a system of therapy
which [0627] i) can remove materials deleterious to wound healing
from wound exudate, whilst retaining materials that are beneficial
in promoting wound healing in contact with the wound bed, and/or
[0628] ii) which allows fluids containing active amounts of
materials that are beneficial in promoting wound healing to pass
into and/or through the wound in contact with the wound bed.
[0629] Thus, in a third aspect of the present invention there is
provided a method of treating wounds to promote wound healing using
the apparatus for irrigating, supplying thermal energy to and/or
cleansing wounds of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0630] The present invention will now be described by way of
example only with reference to the accompanying drawings in
which:
[0631] FIGS. 1A-1B are views of an apparatus for irrigating,
supplying thermal energy to and/or cleansing a wound according to
the first aspect of the present invention. FIG. 1A is a schematic
view of an apparatus for irrigating, supplying thermal energy to
and/or cleansing a wound according to the first aspect of the
present invention. FIG. 1B is a cross-sectional side view of the
wound dressing portion of the apparatus of FIG. 1A.
[0632] It has a single-phase system means for fluid cleansing in
the form of an ultrafiltration unit.
[0633] FIG. 2 is a schematic view of an apparatus for irrigating,
supplying thermal energy to and/or cleansing a wound according to
the first aspect of the present invention.
[0634] It has a two-phase system means for fluid cleansing in the
form of a dialysis unit or a biphasic extraction unit.
[0635] The means for supplying conducted thermal energy are omitted
from the schematics for clarity.
[0636] FIG. 3 is a cross-sectional side view of a conformable wound
dressing, of the second aspect of the present invention for
aspirating and/or irrigating wounds.
[0637] FIG. 4 is a cross-sectional side view of another conformable
wound dressing of the second aspect of the present invention for
aspirating and/or irrigating wounds.
[0638] FIG. 5 is a cross-sectional side view of another conformable
wound dressing of the second aspect of the present invention for
aspirating and/or irrigating wounds.
[0639] FIGS. 6A-6B are views of another conformable wound dressing
of the second aspect of the present invention for aspirating and/or
irrigating wounds. FIG. 6A is a cross-sectional side view of
another conformable wound dressing of the second aspect of the
present invention for aspirating and/or irrigating wounds. FIG. 6B
shows three configurations of the chamber of FIG. 6A.
[0640] FIGS. 7A-7B are views of an apparatus for aspirating,
irrigating and/or cleansing a wound according to the first aspect
of the present invention. FIG. 7A is a schematic view of an
apparatus for aspirating, irrigating and/or cleansing a wound
according to the first aspect of the present invention. It has a
single-phase system means for fluid cleansing in the form of an
ultrafiltration unit. FIG. 7B is a cross-sectional side view of the
wound dressing portion of the apparatus of FIG. 7A.
[0641] FIG. 8 is a schematic view of an apparatus for aspirating,
irrigating and/or cleansing a wound according to the first aspect
of the present invention. It has a two-phase system means for fluid
cleansing in the form of a dialysis unit, or a biphasic extraction
unit.
[0642] FIGS. 9A-9B are views of apparatus for aspirating,
irrigating and/or cleansing a wound according to the first aspect
of the present invention. FIG. 9A is a schematic view of another
apparatus for aspirating, irrigating and/or cleansing a wound
according to the first aspect of the present invention. FIG. 9B is
a cross-sectional size view of the wound dressing portion of the
apparatus of FIG. 9A.
[0643] It has a single-phase system means for fluid cleansing in
the form of an ultrafiltration unit.
DETAILED DESCRIPTION OF THE DRAWINGS
[0644] Referring to FIGS. 1A and 1B, the apparatus (1) for
irrigating, supplying thermal energy to and/or cleansing wounds
comprises a conformable wound dressing (2), having a backing layer
(3) which is capable of forming a relatively fluid-tight seal or
closure (4) over a wound (5) and one inlet pipe (6) for connection
to a fluid supply tube (7), which passes through the wound-facing
face of the backing layer (5) at (8), and one outlet pipe (9) for
connection to a fluid offtake tube (10), which passes through the
wound-facing face at (11), the points (8), (11) at which the inlet
pipe and the outlet pipe passes through and/or under the
wound-facing face forming a relatively fluid-tight seal or closure
over the wound, and means for supplying conducted thermal energy to
the fluid in the wound in the form of an electrical heater (111)
(not shown) on the inlet pipe (6). (In a variant of this apparatus
noted further below, the means for supplying conducted thermal
energy to the fluid in the wound is in the form of an electrical
heat pad mounted on top of the backing layer (3) which is capable
of conducting heat to the wound (5) through the irrigant), the
inlet pipe being connected via means for flow switching between
supply and recirculation, here a T-valve (14), by the fluid supply
tube (7) to a fluid reservoir (12) and to a fluid recirculation
tube (13) having a means for bleeding the tube, here a bleed
T-valve (16) to waste, e.g. to a collection bag (not shown), the
outlet pipe (9) being connected to a fluid offtake tube (15)
connected in turn to means for fluid cleansing (17), here in the
form of an ultrafiltration unit, connected to the inlet pipe (6)
via the fluid recirculation tube (13) and T-valve (14), and a
device for moving fluid through the wound and means for fluid
cleansing (17), here a peristaltic pump (18), e.g. preferably a
small portable peristaltic pump, acting on the fluid circulation
tube (13) with the peripheral rollers on its rotor (not shown) to
apply a low negative pressure on the wound.
[0645] The ultrafiltration unit (17) is a single-phase system.
[0646] In this the circulating fluid from the wound and the fluid
reservoir passes through a self-contained system in which materials
deleterious to wound healing are removed and the cleansed fluid,
still containing materials that are beneficial in promoting wound
healing, is returned via the recirculation tube to the wound
bed.
[0647] (In a variant of this apparatus, there are two inlet pipes
(6), which are connected respectively to a fluid supply tube (7)
and fluid recirculation tube (13), respectively having a first
valve (19) for admitting fluid into the wound from the fluid
reservoir (12) and a second valve (20) for admitting fluid into the
wound from the recirculation tube. Usually in use of the apparatus,
when the first valve (19) is open, the second valve (20) is shut,
and vice versa.)
[0648] In use of the apparatus (1), the valve (16) is opened to a
collection bag (not shown), and the T-valve (14) is turned to admit
fluid from the fluid reservoir to the wound dressing through the
fluid supply tube (7) and inlet pipe (6).
[0649] (In the variant of this apparatus having two inlet pipes
(6), which are connected respectively to a fluid supply tube (7)
and fluid recirculation tube (13), the first valve (19) for
admitting fluid into the wound from the fluid reservoir (12) is
opened and the second valve (20) is shut, and vice versa.)
[0650] The pump (18) is started to nip the fluid recirculation tube
(13) with the peripheral rollers on its rotor (not shown) to apply
a low positive pressure on the wound. It is allowed to run until
the apparatus is primed throughout the whole length of the
apparatus flow path and excess fluid is voided to waste via the
bleed T-valve (16) into the collection bag (not shown).
[0651] The electrical heater (111) on inlet pipe (6) is turned on
to supply conducted thermal energy to the fluid in the wound.
[0652] The T-valve (14) is then turned to switch from supply and
recirculation, i.e. is set to close the wound to the fluid
reservoir (12) but to admit fluid into the wound from the fluid
recirculation tube (13), and the bleed T-valve (16) is
simultaneously closed.
[0653] (In the variant of this apparatus, where there are two inlet
pipes (6), which are connected respectively to a fluid supply tube
(7) and fluid recirculation tube (13), the first valve (19) is
closed and a recirculating system set up by opening the second
valve (20) for admitting fluid into the wound from the
recirculation tube (13)).
[0654] The circulating fluid from the wound and the fluid reservoir
(12) passes through the ultrafiltration unit (17). Materials
deleterious to wound healing are removed and the cleansed fluid
still containing materials that are beneficial in promoting wound
healing, is returned via the recirculation tube (13) to the wound
bed.
[0655] The recirculation of fluid may be continued as long as
desired.
[0656] Switching between supply and recirculation is then reversed,
by turning the T-valve (14) to admit fluid from the fluid reservoir
to the wound dressing through the fluid supply tube (7) and inlet
pipe (6).
[0657] (In the variant of this apparatus having two inlet pipes
(6), which are connected respectively to a fluid supply tube (7)
and fluid recirculation tube (13), the first valve (19) for
admitting fluid into the wound from the fluid reservoir (12) is
opened and the second valve (20) is shut, and vice versa.)
[0658] The bleed valve (16) is simultaneously opened, so that fresh
fluid flushes the recirculating system.
[0659] The running of the pump (18) may be continued until the
apparatus is flushed, when it and the fluid recirculation is
stopped, and the electrical heater (111) on inlet pipe (6) is
turned off.
[0660] If, e.g. the wound is in a highly exuding state, there is a
positive change in the balance of fluid in recirculation. It may be
necessary to bleed fluid from recirculation by opening the bleed
T-valve (16) to bleed fluid from the recirculation tube (13).
[0661] Referring to FIG. 2, the apparatus (21) is a variant of that
of FIG. 1A, with identical, and identically numbered, components,
except for the means for fluid cleansing, which is in the form of a
two-phase system, here a dialysis unit (23).
[0662] In this, there is one system through which the Circulating
fluid from the wound and the fluid reservoir passes and from which
deleterious materials are removed by selectively permeable contact
with a second system, through which passes a cleansing fluid.
[0663] The dialysis unit (23) thus has an internal polymer film,
sheet or membrane (24), selectively permeable to materials
deleterious to wound healing, which divides it into [0664] a) a
first chamber (25), through which passes a cleansing fluid across
one surface of the polymer film, sheet or membrane, and [0665] b) a
second chamber (26), through which passes the circulating fluid
from the wound and the fluid reservoir (12), and from which
deleterious materials are removed.
[0666] The dialysis unit (23) thus has a dialysate inlet pipe (28)
connecting to a dialysate supply tube (29) which passes to a
peristaltic pump (38), e.g. preferably a small portable peristaltic
pump, acting on the dialysate supply tube (29) with the peripheral
rollers on its rotor (not shown) to supply cleansing fluid across
the surface of the polymer film, sheet or membrane (28) in the
first chamber (25) from a dialysate reservoir (not shown) via a
valve (34).
[0667] The dialysis unit (23) also has a dialysate outlet pipe (30)
connecting to a dialysate outlet tube (31) which passes to waste
via a second bleed T-valve (36) into, e.g. a collection bag (not
shown).
[0668] Operation of this apparatus is similar to that of FIG. 1A,
except for the dialysis unit (23), in that at some point after the
irrigation system is primed and steady state recirculation
established through the length of the apparatus flow path, the
valve (34) and second bleed valve (36) are opened.
[0669] The pump (38) is started to nip fluid dialysate tube (29)
with the peripheral rollers on its rotor (not shown) to pump
cleansing fluid to the first chamber from a dialysate reservoir
(not shown) and out to waste via the bleed valve (36) into the
collection bag (not shown).
[0670] The dialysis unit (23) is a module (or scrubbing cartridge)
with a substrate that changes color to indicate the presence of
detrimental factors in the cleansed fluid, and that the scrubbing
cartridge is exhausted and should be renewed.
[0671] Referring to FIGS. 3 to 7, each dressing (41) is in the form
of a conformable body defined by a microbe-impermeable film backing
layer (42) with a uniform thickness of 25 micron, with a
wound-facing face (43) which is capable of forming a relatively
fluid-tight seal or closure over a wound.
[0672] The backing layer (42) extends in use on a wound over the
skin around the wound. On the proximal face of the backing layer
(43) on the overlap (44), it bears an adhesive film (45), to attach
it to the skin sufficiently to hold the wound dressing in place in
a fluid-tight seal around the periphery of the wound-facing face
(43) of the wound dressing.
[0673] There is one inlet pipe (46) for connection to a fluid
supply tube (not shown), which passes through and/or under the
wound-facing face (43), and one outlet pipe (47) for connection to
a fluid offtake tube (not shown), which passes through and/or under
the wound-facing face (43).
[0674] Referring to FIG. 3, one form of the dressing comprises a
circular sheet (70) that lies under a circular backing layer (72)
and is permanently attached to a boss (81), which is e.g.
heat-sealed to the backing layer (72).
[0675] An annular layer of foam (74) formed of a suitable material,
e.g. a resilient thermoplastic, preferably a reticulated filtration
polyurethane foam with small apertures or pores, spaces the sheet
(70) from the backing layer and surrounds the boss (81).
[0676] A downwardly dished membrane (75) with openings (76) is
permanently attached to the sheet (70) by heat-sealing to form a
chamber (77) with the sheet (70).
[0677] An inlet pipe (76) and outlet pipe (77) are mounted
centrally in the boss (81) and pass through the backing layer
(72).
[0678] The inlet pipe (76) is made of a polyurethane tubular core
(not shown) surrounded by an annulus of resistive conductive
material, such as one of the resistive alloys noted hereinbefore,
which generates thermal energy when a voltage drop is applied over
it. It is connected to a cell (78), shown schematically, which
applies a voltage drop over it. The inlet pipe (76) communicates
with the interior of the chamber (77), which thus forms an inlet
manifold that distributes heated fluid directly to the wound when
the dressing is in use.
[0679] The outlet pipe (77) extends radially immediately under the
backing layer (3) and communicates with the inner face of the layer
of foam (74), which forms an outlet manifold.
[0680] This form of the dressing is a more suitable layout for
shallow wounds.
[0681] Another form of dressing is shown in FIG. 4. An inlet pipe
(76) and outlet pipe (77) are mounted centrally in a boss (81) in,
and pass through a backing layer (3). An oblately hemispheroidal
filler (88) with an annular groove (89) may be permanently attached
to the pipes (76) and (77). It is formed of a suitable material,
e.g. a resilient thermoplastic foam, preferably a reticulated
filtration polyurethane foams with small apertures or pores.
[0682] An annular electrical heat pad (90) is mounted around the
boss (81) on top of the backing layer (3), which is capable of
conducting heat to the wound (5) through the irrigant.
[0683] It may be in the form of non-woven or woven fabric, such as
a woven layer or sheet of carbon fibres or a fabric, such as a
woven layer or sheet made essentially of carbonised acrylate, such
as polyacrylonitrile and copolymers thereof, which generate thermal
energy when a voltage drop is applied over it.
[0684] Alternatively, it may be an electrically insulating flat
sheet or membrane substrate that has an electrically resistive but
conductive printed circuit on it. It is connected to a cell (78),
shown schematically, which applies a voltage drop over it.
[0685] The inlet pipe (76) communicates with the wound space at the
lowest point of the filler (88). The outlet pipe (77) communicates
with the groove (89), and effectively collects the fluid from the
wound periphery when the dressing is in use.
[0686] This form of the dressing is a more suitable layout for
deeper wounds.
[0687] In FIG. 5, an inlet pipe (76) and outlet pipe (77) are
mounted centrally in a boss (81) in, and pass through a backing
layer (3).
[0688] An oblately spheroidal conformable hollow body (78) is
defined by a membrane (79) which is filled with a fluid, here air
or nitrogen, that urges it to the wound shape, and is permanently
attached to the pipes (76) and (77). It is formed of a suitable
material, e.g. a resilient thermoplastic, preferably a reticulated
filtration polyurethane foam with small apertures or pores.
[0689] The inflation inlet pipe (350) communicates with the
interior of the hollow body (78), to permit inflation of the body
(78). The inlet pipe (76) extends through the hollow body (78). The
outlet pipe (77) communicates with an outlet manifold formed by a
series of radial apertures in a foam disc (87) immediately under
the backing layer, which collects the fluid from the wound
periphery when the dressing is in use.
[0690] An electrical heater (90) is mounted under the boss (81) on
top of the backing layer (3), which is transparent to radiant heat,
and so permit its transmission to the wound (5) through the
irrigant.
[0691] It may be in the form of a near infrared radiant heater that
generates thermal energy when a voltage drop is applied over it. It
is connected to a cell (78), shown schematically, which applies a
voltage drop over it.
[0692] Referring to FIG. 6A, another form for deeper wounds is
shown. This comprises a circular, or more usually square or
rectangular, backing layer (342) and a chamber (363) in the form of
a deeply indented disc much like a multiple Maltese cross or a
stylized rose.
[0693] This is defined by an upper impervious membrane (361) and a
lower porous film (362) with apertures (364) that deliver the
irrigant fluid directly to the wound bed over an extended area, and
thus effectively forms an inlet manifold. Three configurations of
the chamber (363) are shown in FIG. 6B, all of which are able to
conform well to the wound bed by the arms closing in and possibly
overlapping in insertion into the wound.
[0694] The space above the chamber (363) is filled with a wound
filler (348) under the backing layer (342).
[0695] This comprises an oblately spheroidal conformable hollow
body, defined by a membrane (349) that is filled with a fluid, here
air or nitrogen, that urges it to the wound shape.
[0696] A moulded hat-shaped boss (351) is mounted centrally on the
upper impervious membrane (361) of the chamber (363). It has three
internal channels, conduits or passages through it (not shown),
each with entry and exit apertures.
[0697] The filler (348) is attached to the membrane (361) of the
chamber (363) by adhesive, heat welding or a mechanical fixator,
such as a cooperating pin and socket.
[0698] An inflation inlet pipe (350) inlet pipe (346) and outlet
pipe (347) pass under the edge of the proximal face of the backing
layer (342) of the dressing, and extend radially immediately under
the filler (348) and over the membrane (361) of the chamber (363)
to each mate with an entry aperture in the boss (351).
[0699] An exit to the internal channel, conduit or passage through
it that receives the inflation inlet pipe (350) communicates with
the interior of the hollow filler (348), to permit inflation.
[0700] An exit to the internal channel, conduit or passage that
receives the inlet pipe (346) communicates with the interior of the
chamber (363) to deliver the irrigant fluid via the chamber (363)
to the wound bed over an extended area.
[0701] Similarly, an exit to the internal channel, conduit or
passage that receives the outlet pipe (347) communicates with the
space above the chamber (363) and under the wound filler (348), and
collects flow of irrigant and/or wound exudate radially from the
wound periphery.
[0702] At its distal end furthest from the wound, the inlet pipe
(346) is permanently attached to, and communicate with the interior
of, a recirculation tube (413) in the form of a spiral or loop or a
more convoluted form. This is a meandering tortuous or winding path
(not shown) sandwiched between parallel electrically heated plates
of resistive conductive material, such as a resistive alloys (also
not shown), all within a moulded disc-shape housing case (416).
[0703] This has entry and exit apertures in the edge extending
between the faces of the case, through which the irrigant tubing
passes. The heated plates connected to a cell (419) shown
schematically, which applies a voltage drop over them in use.
[0704] The boss (351) mounted centrally on the upper impervious
membrane (361) of the chamber (363) may also include a lumen
through it (not shown in the Figure) with entry and exit apertures.
A fourth pipe may also pass under the edge of the proximal face of
the backing layer (342) of the dressing, and extend radially
immediately under the filler (348) and over the membrane (361) of
the chamber (363) to mate with the lumen entry aperture in the boss
(351).
[0705] An exit to the internal channel, conduit or passage through
it that receives this pipe may communicate with the space above the
chamber (363) and under the wound filler (348), to permit the
monitoring of wound pressure.
[0706] Referring to FIG. 7A, the apparatus (1) for aspirating,
irrigating and/or cleansing wounds is a variant of the apparatus
(1) of FIG. 1A.
[0707] It has bypass (711) around the pump (17), as a protection of
the pump against any blockage in the system.
[0708] It is activated automatically by appropriate means, e.g. it
is normally blocked by a bursting disc (not shown), or a
pressure-activated motorised valve.
[0709] An alternative to the by-pass (711) is a pressure sensor for
the monitoring of pressure in the system and a control feedback
circuit for its regulation, e.g. a pressure sensor at a point in
the wound space for the monitoring of negative pressure there,
which communicates with a control feedback circuit that will shut
down the pump when the sensor detects excessive negative pressure.
Such a pressure sensor for the monitoring of pressure in the system
and a control feedback circuit for its regulation is depicted in
FIG. 9A.
[0710] Another alternative to the by-pass (711) is a pressure
sensor mounted downstream of the pump for the monitoring of
positive pressure there, which communicates with a control feedback
circuit that will shut down the pump when the sensor detects
excessive positive pressure from resistance, e.g. in the means for
fluid cleansing that is likely to cause the system to fail
catastrophically (e.g. burst tubes).
[0711] Referring to FIG. 8, the apparatus (1) for aspirating,
irrigating and/or cleansing wounds is a variant of the apparatus
(1) of FIG. 2.
[0712] The latter is a two-phase system with a dialysis unit (21),
but is one in which dialytic fluid passes only once across the
surface of the dialytic membrane (28) in the first chamber (25)
from a dialysate reservoir (not shown) to waste via a second bleed
T-valve (36) into, e.g. a collection bag (not shown).
[0713] This variant has a dialysate recirculation tube (811)
running between a first T-valve (816) on the inlet side of the
dialysate pump (23) and a second T-valve (817) to permit the pump
(23) to recirculate the dialysate once the circuit is primed in
multiple passes through the dialysis unit (21).
[0714] The operation of the system will be apparent to the skilled
person.
[0715] Referring to FIG. 9A, the apparatus (1) for aspirating,
irrigating and/or cleansing wounds is a major variant of the
apparatus shown in FIG. 1A.
[0716] The device for moving fluid through the wound and means for
fluid cleansing (17) in FIG. 1A is a peristaltic pump (18), e.g.
preferably a small portable peristaltic pump, acting on the fluid
circulation tube (13) downstream of the dressing (2) to apply an
overall low negative pressure in the wound space.
[0717] In the apparatus (1) shown in FIG. 9A, the peristaltic pump
(18) is replaced by: [0718] a) a peristaltic pump (926) acting on
the fluid supply tube (7) upstream of the dressing (2), and [0719]
b) a vacuum pump assembly (918) with pressure regulating means,
acting on the fluid circulation tube (13) downstream of the
dressing (2), to apply an overall low negative pressure in the
wound space.
[0720] The vacuum pump assembly comprises a tank (911) with an
inlet tube (912) connecting to the fluid circulation tube (13) and
communicating with the upper part of the tank (911), a waste tube
(913) connecting to a waste pump (914) with waste bag (915) and
communicating with the lower part of the tank (911) a pump tube
(917) connecting to a vacuum pump (918) and communicating with the
upper part of the tank (911), and connecting via the fluid
circulation tube (13) to the means for cleansing (17) and
communicating with the lower part of the tank (911).
[0721] The vacuum pump (918) is controlled by a pressure feedback
regulator (919) through an electrical line (920), the regulator
receiving signals from a tank sensor (921) in the upper part of the
tank (911), and a dressing sensor (922) in the wound space
respectively via lines (923) and (924).
[0722] The waste pump (914) is controlled by a waste level feedback
regulator (929) the regulator receiving signals from a tank sensor
with electrical line (930) in the middle part of the tank
(911).
[0723] The vacuum pump (918) either acts as a valve so that the
pump tube 917 connecting to the vacuum pump (918) is normally
blocked to prevent passage of air through it from the upper part of
the tank (911) when the vacuum pump (918) is at rest, or the pump
tube (917) is provided with a manual or motorised, e.g.
pressure-activated motorised, valve (930) {not shown}, so that the
pump tube (917) connecting to the vacuum pump (918) may be blocked
to prevent such passage.
[0724] The operation of the apparatus (1) is similar to that of the
apparatus in FIG. 1A mutatis mutandis.
[0725] In use of the apparatus (1), the valve (16) is opened to a
collection bag (not shown), and the T-valve (14) is turned to admit
fluid from the fluid reservoir to the wound dressing through the
fluid supply tube (7) and inlet pipe (6).
[0726] The pump (926) is started to nip the fluid recirculation
tube (7) with the peripheral rollers on its rotor (not shown) to
apply a low positive pressure on the wound.
[0727] The vacuum pump (918) either acts as a valve since it is at
rest, or the valve (930) (not shown) is closed, so that the pump
tube (917) is blocked to prevent passage of air through it from the
upper part of the tank (911). Irrigant pumped from the wound
dressing (2) through the fluid offtake tube (10) is pumped through
the lower part of the tank (911) up the outlet tube (917) via the
means for cleansing (17) to the bleed T-valve (16) into, e.g. a
collection bag (not shown).
[0728] The peristaltic pump (926) acting on the fluid supply tube
(7) upstream of the dressing (2) is allowed to run until the
apparatus is primed throughout the whole length of the apparatus
flow path and excess fluid is voided to waste via the bleed T-valve
(16) into the collection bag.
[0729] The T-valve (14) is then turned to switch from supply to
recirculation, i.e. is set to close the wound to the fluid
reservoir (12) but to admit fluid into the wound from the fluid
recirculation tube (13), and the bleed T-valve (16) is
simultaneously closed.
[0730] The vacuum pump (918) is then activated, and, if the vacuum
pump (918) does not act as a valve when at rest, the valve (930) in
the pump tube (917) is opened, to apply a low negative pressure to
the wound.
[0731] The circulating fluid from the wound and the fluid reservoir
(12) passes through the cleansing unit (17). Materials deleterious
to wound healing are removed and the cleansed fluid, still
containing materials that are beneficial in promoting wound
healing, is returned via the recirculation tube (13) to the wound
bed.
[0732] The pressure feedback regulator (919) regulates the pressure
at the wound and/or the tank (911).
[0733] If the amount of fluid in circulation becomes excessive,
e.g. because the wound continues to exude heavily, the waste pump
(914) may be started by the waste level feedback regulator (929) on
the regulator receiving signals from the tank sensor with
electrical line (930).
[0734] The recirculation of fluid may be continued as long as
desired.
[0735] The vacuum pump (918) is then deactivated, and, if the
vacuum pump (918) does not act as a valve when at rest, the valve
(930) in the pump tube (917) is closed, and the bleed T-valve (16)
is opened to air to relieve the low negative pressure in the tank
(911) via the means for cleansing (17) and the outlet tube
(917).
[0736] Switching between supply and recirculation is then reversed,
by turning the T-valve (14) to admit fluid from the fluid reservoir
to the wound dressing through the fluid supply tube (7) and inlet
pipe (6).
[0737] The bleed valve (16) is left open, so that fresh fluid
flushes the recirculating system. The running of the pump (918) may
be continued until the apparatus is flushed, when it and the fluid
recirculation is stopped.
[0738] The use of the apparatus of the present invention will now
be described by way of example only in the following Example:
Example 1
[0739] The combination of the removal by dialysis of materials
deleterious to wound healing (H.sub.2O.sub.2) by an enzyme
(catalase) retained in a moving second phase and the transmission
of heat to a moving first phase.
[0740] An apparatus of the present invention was constructed
essentially as in FIG. 2, i.e. one in which the means for fluid
cleansing is a two-phase system dialysis unit. In such an
apparatus, an irrigant and/or wound exudate first phase from the
wound recirculates through a first circuit and passes in through
the dialysis unit in contact across a selectively permeable
dialysis membrane with a second fluid (dialysate) phase. The
dialysis unit was operated with the two phases flowing
counter-current to each other.
[0741] Hydrogen peroxide is produced in conditions of oxidative
stress following reduced blood flow and or the inflammatory
response to bacterial contamination of wounds. It may be removed by
the appropriate antagonists and/or degraders, which include enzymic
or other inhibitors, such as peroxide degraders, e.g. catalase.
[0742] The first circuit comprised a surrogate wound chamber
(Minucells perfusion chamber) in which normal diploid human
fibroblasts were cultured on 13 mm diameter (Thermanox polymer)
cover slips retained in a two-part support (Minnucells Minusheets).
Tissues present in the healing wound that must survive and
proliferate were represented by the cells within the chamber.
[0743] Nutrient medium (DMEM with 10% FCS with 1% Buffer All) to
simulate wound exudate was pumped from a reservoir into the lower
aspect of the chamber where it bathed the fibroblasts and was
removed from the upper aspect of the chamber and returned to the
reservoir.
[0744] The first circuit also comprised [0745] a) Upstream of the
wound chamber, a luer-fitting hollow fibre tangential membrane
dialysis unit (Spectrum.RTM. MicroKros.RTM. X14S-100-04N, 8
cm.sup.2 surface area, 400KD Mol. Wt. cut off) through which a
second cleansing circuit containing nutrient media with between
5,000 and 50,000 units (.mu. moles H.sub.2O.sub.2 degraded per min
at pH7, 25.degree. C.) per ml of catalase (in a circuit with a
reservoir and total volume of between 5.0 mL and 20 mL) at a flow
rate of between 0.5 ml min.sup.-1 and 5.0 ml min.sup.-1 could be
passed in a counter current direction, and [0746] b) upstream of
the wound chamber, a heat exchanger such that the temperature of
the nutrient media bathing the cells reaches between 35.degree. C.
and 37.degree. C.
[0747] The pumps for the two circuits were peristaltic pumps acting
on silicone tubing or equivalent. The internal diameter of the
tubing was 1.0 mm. A total volume for the first circuit including
the chamber and the reservoir at a number of values between 25 and
75 ml was used. The flow rates used were at a number of values
between 0.5 ml min.sup.-1 and 5.0 ml min.sup.-1.
[0748] Experiments were conducted that simulated conditions not
uncommon for healing wounds whereby the chamber simulating the
wound was placed in a room temperature environment (simulating the
low temperatures often experienced in wounds where blood flow is
poor) and the nutrient medium containing a material deleterious to
wound healing, namely hydrogen peroxide, was circulated over the
cells.
[0749] First and second control apparatus were also constructed
essentially as in FIG. 2, but where either [0750] a) the cleansing
membrane dialysis unit is omitted, so that the nutrient flow passes
directly from the reservoir, or [0751] b) the heat exchanger is
omitted, so that the nutrient flow bathing the cells does not reach
between 35.degree. C. and 37.degree. C. and remains at between
18.degree. C. and 20.degree. C.
[0752] In controls where either [0753] a) the passage of the
nutrient flow through the cleansing membrane dialysis unit or
[0754] b) the heat exchanger unit is omitted, and the concentration
of H.sub.2O.sub.2 lies between 5 and 20 mM and the temperature of
the nutrient medium bathing the cells is between 18.degree. C. and
20.degree. C., survival and growth of the fibroblasts is
inhibited.
[0755] However, when the nutrient medium flow in the first circuit
is [0756] c) connected into the ends of the membrane dialysis unit
through which a second cleansing circuit containing catalase (at
the concentrations and flow rates noted above) is passing in a
counter current direction, and [0757] d) passes through a heat
exchanger so that the temperature of the nutrient media bathing the
cells reaches between 35.degree. C. and 37.degree. C., the
fibroblasts survive and proliferate to a greater extent during a 24
hour period than the control circuits.
Example 2
[0758] The combination of the removal by dialysis of materials
deleterious to wound healing (H.sub.2O.sub.2) by an enzyme
(catalase) retained in a static second phase and the transmission
of heat to a moving first phase.
[0759] An apparatus of the present invention was constructed
essentially as in FIG. 2, i.e. one in which the means for fluid
cleansing is a two-phase system dialysis unit. In such an
apparatus, an irrigant and/or wound exudate first phase from the
wound recirculates through a first circuit and passes over the
dialysis unit in contact across a selectively permeable dialysis
membrane with a second static fluid (dialysate) phase.
[0760] Hydrogen peroxide is produced in conditions of oxidative
stress following reduced blood flow and or the inflammatory
response to bacterial contamination of wounds. It may be removed by
the appropriate antagonists and/or degraders, which include enzymic
or other inhibitors, such as peroxide degraders, e.g. catalase.
[0761] The first circuit comprised a surrogate wound chamber
(Minucells perfusion chamber) in which normal diploid human
fibroblasts were cultured on 13 mm diameter (Thermanox polymer)
cover slips retained in a two-part support (Minnucells Minusheets).
Tissues present in the healing wound that must survive and
proliferate were represented by the cells within the chamber.
[0762] Nutrient medium (DMEM with 10% FCS with 1% Buffer All) to
simulate wound exudate was pumped from a reservoir into the lower
aspect of the chamber where it bathed the fibroblasts and was
removed from the upper aspect of the chamber and returned to the
reservoir.
[0763] The first circuit also comprised [0764] a) for the static
second phase, a length of dialysis tubing (Pierce Snake skin 68100
CG 49358B, 10 KD cut off) placed within the first circuit reservoir
in which a second static cleansing circuit containing nutrient
media with between 5,000 and 50,000 units (.mu. moles
H.sub.2O.sub.2; degraded per min at pH7, 25.degree. C.) per ml of
catalase (in a circuit with a reservoir and total volume of between
5.0 ml and 20 ml) [0765] b) upstream of the wound chamber, a heat
exchanger such that the temperature of the nutrient media bathing
the cells reaches between 35.degree. C. and 37.degree. C.
[0766] The pumps for the circuit were peristaltic acting on
silicone plastic tubing or equivalent. The internal diameter of the
tubing was 1.0 mm. A total volume for the first circuit including
the chamber and the reservoir at a number of values between 25 and
75 ml was used. The flow rates used were at a number of values
between 0.5 ml min.sup.-1 and 5.0 ml min.sup.-1.
[0767] Experiments were conducted that simulated conditions not
uncommon for healing wounds whereby the chamber simulating the
wound was placed in a room temperature environment (simulating the
low temperatures often experienced in wounds where blood flow is
poor) and the nutrient medium containing a material deleterious to
wound healing, namely hydrogen peroxide, was circulated over the
cells.
[0768] First and second control apparatus were also constructed
essentially as in FIG. 2, but where either [0769] e) the cleansing
membrane dialysis unit is omitted, so that the nutrient flow passes
directly from the reservoir, or [0770] f) the heat exchanger is
omitted, so that the nutrient flow bathing the cells does not reach
between 35.degree. C. and 37.degree. C. and remains at between
18.degree. C. and 20.degree. C.
[0771] In controls where either [0772] a) the passage of the
nutrient flow past or through the cleansing membrane dialysis unit
or [0773] b) the heat exchanger unit is omitted, and the
concentration of H.sub.2O.sub.2 lies between 5 and 20 mM and the
temperature of the nutrient medium bathing the cells is between
18.degree. C. and 20.degree. C., survival and growth of the
fibroblasts is inhibited.
[0774] However, when the nutrient medium flow in the first circuit
is [0775] c) passed over the membrane dialysis unit in which a
second cleansing circuit containing catalase (at the concentrations
and flow rates noted above) is present, and [0776] d) passes
through a heat exchanger so that the temperature of the nutrient
media bathing the cells reaches between 35.degree. C. and
37.degree. C., the fibroblasts survive and proliferate to a greater
extent during than the control circuits.
[0777] The following results were obtained: A first phase of
nutrient medium containing 10 .mu.M H.sub.2O.sub.2 at a flow rate
of 1.0 ml min.sup.-1 with a 15 ml static second phase containing
7,600 units ml.sup.-1 catalase contained within a length of
dialysis tubing placed within the first circuit reservoir. The
effect of the catalase cleansing unit and the heat exchanger was as
follows:
TABLE-US-00001 Mean level of cell activity Conditions after 43 hrs*
(n = 6) H.sub.2O.sub.2 in media at 18.degree. C. 0.0 H.sub.2O.sub.2
in media with catalase 0.27 second phase dialysis unit at
18.degree. C. Normal medium control at 18.degree. C. 0.40
H.sub.2O.sub.2 in media at 37.degree. C. 0.0 H.sub.2O.sub.2 in
media with catalase at 0.76 37.degree. C. second phase dialysis
unit Normal medium control at 37.degree. C. 0.55 *Cell activity
measured with WST (Tetrazolium based mitochondrial dehdrogenase
activity assay)
CONCLUSIONS
[0778] The combination of the cleansing dialysis unit that removes
and degrades H2O2 and the heat exchanger unit that maintains the
wound chamber between 35.degree. C. and 37.degree. C. enhances the
cell response necessary for wound healing.
* * * * *