U.S. patent application number 17/204548 was filed with the patent office on 2021-07-01 for methods for manufacturing and assembling dual material tissue interface for negative-pressure therapy.
The applicant listed for this patent is KCI Licensing, Inc.. Invention is credited to John ELWOOD, Christopher Brian LOCKE.
Application Number | 20210196524 17/204548 |
Document ID | / |
Family ID | 1000005462789 |
Filed Date | 2021-07-01 |
United States Patent
Application |
20210196524 |
Kind Code |
A1 |
LOCKE; Christopher Brian ;
et al. |
July 1, 2021 |
Methods For Manufacturing And Assembling Dual Material Tissue
Interface For Negative-Pressure Therapy
Abstract
A dressing for treating tissue with negative pressure may be a
composite of dressing layers, including a release film, perforated
gel layer, a perforated polymer film, a manifold, and an adhesive
cover. A method of manufacturing the dressing may comprise
providing a first layer, such as the gel layer, on a substrate,
perforating the first layer on the substrate to create a plurality
of apertures in the first layer, and creating an index of the
plurality of apertures in the first layer. A laser can be
calibrated based on the index. A second layer, such as the polymer
film, may be coupled to the first layer, and a plurality of slots
can be cut in the second layer with the laser. Each of the slots
can be cut through one of the apertures in the first layer based on
the index.
Inventors: |
LOCKE; Christopher Brian;
(Bournemouth, GB) ; ELWOOD; John; (Clarinbridge,
IE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KCI Licensing, Inc. |
San Antonio |
TX |
US |
|
|
Family ID: |
1000005462789 |
Appl. No.: |
17/204548 |
Filed: |
March 17, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16876299 |
May 18, 2020 |
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17204548 |
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15997931 |
Jun 5, 2018 |
10695227 |
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16876299 |
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62623325 |
Jan 29, 2018 |
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62616244 |
Jan 11, 2018 |
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62615821 |
Jan 10, 2018 |
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62613494 |
Jan 4, 2018 |
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62592950 |
Nov 30, 2017 |
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62576498 |
Oct 24, 2017 |
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62565754 |
Sep 29, 2017 |
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62516540 |
Jun 7, 2017 |
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62516550 |
Jun 7, 2017 |
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62516566 |
Jun 7, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 13/00987 20130101;
B32B 2310/0843 20130101; B32B 2375/00 20130101; B32B 2266/06
20130101; B32B 2307/724 20130101; B32B 2255/20 20130101; B32B
27/308 20130101; A61F 13/0216 20130101; B32B 2266/124 20161101;
B32B 7/06 20130101; B32B 2307/73 20130101; B32B 37/12 20130101;
B32B 2255/10 20130101; B32B 2255/205 20130101; B32B 2255/26
20130101; B23K 26/38 20130101; B32B 2323/04 20130101; B32B 2331/04
20130101; B32B 2535/00 20130101; B32B 2307/7265 20130101; A61F
13/00068 20130101; B32B 37/182 20130101; A61M 1/90 20210501; B32B
27/065 20130101; B32B 27/32 20130101; B32B 2329/04 20130101; B32B
7/12 20130101; B32B 2255/24 20130101; B32B 2266/0278 20130101; B23K
26/0006 20130101; B32B 2333/08 20130101; B32B 2305/022 20130101;
B32B 2266/0221 20130101; B32B 5/18 20130101; A61F 13/00995
20130101; B32B 2307/728 20130101 |
International
Class: |
A61F 13/00 20060101
A61F013/00; A61F 13/02 20060101 A61F013/02; B23K 26/00 20060101
B23K026/00; B23K 26/38 20060101 B23K026/38; B32B 5/18 20060101
B32B005/18; B32B 7/06 20060101 B32B007/06; B32B 7/12 20060101
B32B007/12; B32B 27/06 20060101 B32B027/06; B32B 27/30 20060101
B32B027/30; B32B 27/32 20060101 B32B027/32; B32B 37/12 20060101
B32B037/12; B32B 37/18 20060101 B32B037/18 |
Claims
1. A method of manufacturing a dressing for negative-pressure
treatment, the method comprising: perforating a gel layer to create
a plurality of apertures in the gel layer; placing a polymer film
adjacent to the gel layer; and cutting a plurality of slots in the
polymer film, wherein each of the slots is cut through one of the
apertures in the gel layer.
2. The method of claim 1, wherein at least one of the slots is
centered in one of the apertures.
3. The method of claim 1, wherein: each of the slots has a length
not greater than a length or diameter of each of the apertures; and
each of the slots has a width not greater than a width or diameter
of each of the apertures.
4. The method of claim 1, further comprising: bonding the polymer
film to a manifold; and bonding a cover to the gel layer around the
polymer film and the manifold.
5. The method of claim 1, wherein the gel layer comprises a
hydrophobic gel.
6. The method of claim 1, wherein the gel layer comprises silicone
gel.
7. The method of claim 1, wherein the gel layer has an area density
less than 300 grams per square meter.
8. The method of claim 1, wherein the gel layer has a hardness
between about 5 Shore OO and about 80 Shore OO.
9. The method of claim 1, wherein the polymer film is a hydrophobic
polymer film.
10. The method of claim 1, wherein the polymer film has a contact
angle with water greater than 90 degrees.
11. The method of claim 1, wherein the polymer film is a
polyethylene film.
12. The method of claim 1, wherein the polymer film is a
polyethylene film having an area density of less than 30 grams per
square meter.
13. The method of claim 1, wherein: each of the apertures has a
diameter no greater than 2 millimeters; and each of the slots has a
length no greater than the diameter of each of the apertures.
14. The method of claim 1, wherein each of the apertures has a
diameter greater than or equal to a length of each of the
slots.
15. The method of claim 1, wherein: each of the apertures has a
length greater than or equal to a length of each of the slots; and
each of the apertures has a width greater than or equal to a width
of each of the slots.
16. The method of claim 1, wherein: the gel layer has an area
density less than 300 grams per square meter and a hardness of
between about 5 Shore OO and about 80 Shore OO; the polymer film
has a contact angle with water greater than 90 degrees and an area
density of less than 30 grams per square meter; each of the slots
is centered in one of the apertures; each of the slots has a length
not greater than a length or diameter of each of the apertures; and
each of the slots has a width not greater than a width or diameter
of each of the apertures.
Description
RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 16/876,299, filed May 18, 2020, which is a
continuation of U.S. patent application Ser. No. 15/997,931,
entitled "Methods for Manufacturing and Assembling Dual Material
Tissue Interface for Negative-Pressure Therapy," filed Jun. 5,
2018, which claims the benefit, under 35 U.S.C. .sctn. 119(e), of
the filing of U.S. Provisional Patent Application No. 62/623,325,
entitled "Methods For Manufacturing And Assembling Dual Material
Tissue Interface For Negative-Pressure Therapy," filed Jan. 29,
2018; U.S. Provisional Patent Application No. 62/616,244, entitled
"Composite Dressings For Improved Granulation And Reduced
Maceration With Negative-Pressure Treatment," filed Jan. 11, 2018;
U.S. Provisional Patent Application No. 62/615,821, entitled
"Methods For Manufacturing And Assembling Dual Material Tissue
Interface For Negative-Pressure Therapy," filed Jan. 10, 2018; U.S.
Provisional Patent Application No. 62/613,494, entitled "Peel And
Place Dressing For Thick Exudate And Instillation," filed Jan. 4,
2018; U.S. Provisional Patent Application No. 62/592,950, entitled
"Multi-Layer Wound Filler For Extended Wear Time," filed Nov. 30,
2017; U.S. Provisional Patent Application No. 62/576,498, entitled
"Systems, Apparatuses, And Methods For Negative-Pressure Treatment
With Reduced Tissue In-Growth," filed Oct. 24, 2017; U.S.
Provisional Patent Application No. 62/565,754, entitled "Composite
Dressings For Improved Granulation And Reduced Maceration With
Negative-Pressure Treatment," filed Sep. 29, 2017; U.S. Provisional
Patent Application No. 62/516,540, entitled "Tissue Contact
Interface," filed Jun. 7, 2017; U.S. Provisional Patent Application
No. 62/516,550, entitled "Composite Dressings For Improved
Granulation And Reduced Maceration With Negative-Pressure
Treatment" filed Jun. 7, 2017; and U.S. Provisional Patent
Application No. 62/516,566, entitled "Composite Dressings For
Improved Granulation And Reduced Maceration With Negative-Pressure
Treatment" filed Jun. 7, 2017, each of which are incorporated
herein by reference for all purposes.
TECHNICAL FIELD
[0002] The invention set forth in the appended claims relates
generally to tissue treatment systems and more particularly, but
without limitation, to methods of manufacturing a dual material
tissue interface for negative-pressure therapy.
BACKGROUND
[0003] Clinical studies and practice have shown that reducing
pressure in proximity to a tissue site can augment and accelerate
growth of new tissue at the tissue site. The applications of this
phenomenon are numerous, but it has proven particularly
advantageous for treating wounds. Regardless of the etiology of a
wound, whether trauma, surgery, or another cause, proper care of
the wound is important to the outcome. Treatment of wounds or other
tissue with reduced pressure may be commonly referred to as
"negative-pressure therapy," but is also known by other names,
including "negative-pressure wound therapy," "reduced-pressure
therapy," "vacuum therapy," "vacuum-assisted closure," and "topical
negative-pressure," for example. Negative-pressure therapy may
provide a number of benefits, including migration of epithelial and
subcutaneous tissues, improved blood flow, and micro-deformation of
tissue at a wound site. Together, these benefits can increase
development of granulation tissue and reduce healing times.
[0004] There is also widespread acceptance that cleansing a tissue
site can be highly beneficial for new tissue growth. For example, a
wound or a cavity can be washed out with a stream of liquid
solution for therapeutic purposes. These practices are commonly
referred to as "irrigation" and "lavage" respectively.
"Instillation" is another practice that generally refers to a
process of slowly introducing fluid to a tissue site and leaving
the fluid for a prescribed period of time before removing the
fluid. For example, instillation of topical treatment solutions
over a wound bed can be combined with negative-pressure therapy to
further promote wound healing by loosening soluble contaminants in
a wound bed and removing infectious material. As a result, soluble
bacterial burden can be decreased, contaminants removed, and the
wound cleansed.
[0005] While the clinical benefits of negative-pressure therapy
and/or instillation therapy are widely known, improvements to
therapy systems, components, and processes may benefit healthcare
providers and patients.
BRIEF SUMMARY
[0006] New and useful systems, apparatuses, and methods for
treating tissue in a negative-pressure therapy environment are set
forth in the appended claims. Illustrative embodiments are also
provided to enable a person skilled in the art to make and use the
claimed subject matter.
[0007] For example, in some embodiments, a dressing for treating
tissue may be a composite of dressing layers including a release
film, perforated gel layer, a perforated polymer film, a manifold,
and an adhesive cover. The manifold may be reticulated foam in some
examples, and may be relatively thin and hydrophobic to reduce the
fluid hold capacity of the dressing. The manifold may also be thin
to reduce the dressing profile and increase flexibility, which can
enable it to conform to wound beds and other tissue sites under
negative pressure. In some embodiments, the perforations may be
slits or slots.
[0008] The perforation pattern of the polymer film can be aligned
with the perforation pattern of at least a central area of the gel
layer. For example, in some embodiments, the gel layer may be
perforated and indexed on a liner, and the polymer film can loaded
and fixed to the gel layer. The combined laminate can be presented
to a laser. The position of a laser mask can be calibrated to an
underside of the dressing, referencing perforations in the gel
layer to calibrate its position. The laser can then be fired,
creating centrally registered slots in the polymer film within the
perforations of the gel layer.
[0009] More generally, a method of manufacturing a dressing for
negative-pressure treatment may comprise providing a first layer,
such as the gel layer, on a substrate, perforating the first layer
on the substrate to create a plurality of apertures in the first
layer, and creating an index of the plurality of apertures in the
first layer. A laser can be calibrated based on the index. A second
layer, such as the polymer film, may be coupled to the first layer,
and a plurality of slots can be cut in the second layer with the
laser. Each of the slots can be cut through one of the apertures in
the first layer based on the index.
[0010] Objectives, advantages, and a preferred mode of making and
using the claimed subject matter may be understood best by
reference to the accompanying drawings in conjunction with the
following detailed description of illustrative embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a functional block diagram of an example
embodiment of a therapy system that can provide negative-pressure
treatment and instillation treatment in accordance with this
specification;
[0012] FIG. 2 is a graph illustrating additional details of example
pressure control modes that may be associated with some embodiments
of the therapy system of FIG. 1;
[0013] FIG. 3 is a graph illustrating additional details that may
be associated with another example pressure control mode in some
embodiments of the therapy system of FIG. 1;
[0014] FIG. 4 is an assembly view of an example of a dressing that
may be associated with some embodiments of the therapy system of
FIG. 1;
[0015] FIG. 5 is a schematic view of an example of a polymer film
illustrating additional details that may be associated with some
embodiments of the dressing of FIG. 4;
[0016] FIG. 6 is a schematic view of an example configuration of
apertures that may be associated with some embodiments of the
dressing of FIG. 4;
[0017] FIG. 7 is a schematic view of an example of a layer having
the configuration of apertures of FIG. 6 overlaid on the polymer
film of FIG. 5; and
[0018] FIG. 8 is a flow diagram illustrating an example method of
manufacturing some components of dressings that may be associated
with the therapy system of FIG. 1.
DESCRIPTION OF EXAMPLE EMBODIMENTS
[0019] The following description of example embodiments provides
information that enables a person skilled in the art to make and
use the subject matter set forth in the appended claims, but may
omit certain details already well-known in the art. The following
detailed description is, therefore, to be taken as illustrative and
not limiting.
[0020] The example embodiments may also be described herein with
reference to spatial relationships between various elements or to
the spatial orientation of various elements depicted in the
attached drawings. In general, such relationships or orientation
assume a frame of reference consistent with or relative to a
patient in a position to receive treatment. However, as should be
recognized by those skilled in the art, this frame of reference is
merely a descriptive expedient rather than a strict
prescription.
[0021] FIG. 1 is a simplified functional block diagram of an
example embodiment of a therapy system 100 that can provide
negative-pressure therapy with instillation of topical treatment
solutions to a tissue site in accordance with this
specification.
[0022] The term "tissue site" in this context broadly refers to a
wound, defect, or other treatment target located on or within
tissue, including, but not limited to, a surface wound, bone
tissue, adipose tissue, muscle tissue, neural tissue, dermal
tissue, vascular tissue, connective tissue, cartilage, tendons, or
ligaments. A wound may include chronic, acute, traumatic, subacute,
and dehisced wounds, partial-thickness burns, ulcers (such as
diabetic, pressure, or venous insufficiency ulcers), flaps, and
grafts, for example. A surface wound, as used herein, is a wound on
the surface of a body that is exposed to the outer surface of the
body, such as an injury or damage to the epidermis, dermis, and/or
subcutaneous layers. Surface wounds may include ulcers or closed
incisions, for example. A surface wound, as used herein, does not
include wounds within an intra-abdominal cavity. The term "tissue
site" may also refer to areas of any tissue that are not
necessarily wounded or defective, but are instead areas in which it
may be desirable to add or promote the growth of additional tissue.
For example, negative pressure may be applied to a tissue site to
grow additional tissue that may be harvested and transplanted.
[0023] The therapy system 100 may include a source or supply of
negative pressure, such as a negative-pressure source 105, a
dressing 110, a fluid container, such as a container 115, and a
regulator or controller, such as a controller 120, for example.
Additionally, the therapy system 100 may include sensors to measure
operating parameters and provide feedback signals to the controller
120 indicative of the operating parameters. As illustrated in FIG.
1, for example, the therapy system 100 may include a first sensor
125 and a second sensor 130 coupled to the controller 120. As
illustrated in the example of FIG. 1, the dressing 110 may comprise
or consist essentially of a tissue interface 135, a cover 140, or
both in some embodiments.
[0024] The therapy system 100 may also include a source of
instillation solution. For example, a solution source 145 may be
fluidly coupled to the dressing 110, as illustrated in the example
embodiment of FIG. 1. The solution source 145 may be fluidly
coupled to a positive-pressure source such as the positive-pressure
source 150, a negative-pressure source such as the
negative-pressure source 105, or both in some embodiments. A
regulator, such as an instillation regulator 155, may also be
fluidly coupled to the solution source 145 and the dressing 110 to
ensure proper dosage of instillation solution (e.g. saline) to a
tissue site. For example, the instillation regulator 155 may
comprise a piston that can be pneumatically actuated by the
negative-pressure source 105 to draw instillation solution from the
solution source during a negative-pressure interval and to instill
the solution to a dressing during a venting interval. Additionally
or alternatively, the controller 120 may be coupled to the
negative-pressure source 105, the positive-pressure source 150, or
both, to control dosage of instillation solution to a tissue site.
In some embodiments, the instillation regulator 155 may also be
fluidly coupled to the negative-pressure source 105 through the
dressing 110, as illustrated in the example of FIG. 1.
[0025] Some components of the therapy system 100 may be housed
within or used in conjunction with other components, such as
sensors, processing units, alarm indicators, memory, databases,
software, display devices, or user interfaces that further
facilitate therapy. For example, in some embodiments, the
negative-pressure source 105 may be combined with the solution
source 145, the controller 120, and other components into a therapy
unit.
[0026] In general, components of the therapy system 100 may be
coupled directly or indirectly. For example, the negative-pressure
source 105 may be directly coupled to the container 115 and may be
indirectly coupled to the dressing 110 through the container 115.
Coupling may include fluid, mechanical, thermal, electrical, or
chemical coupling (such as a chemical bond), or some combination of
coupling in some contexts. For example, the negative-pressure
source 105 may be electrically coupled to the controller 120
fluidly coupled to one or more distribution components to provide a
fluid path to a tissue site. In some embodiments, components may
also be coupled by virtue of physical proximity, being integral to
a single structure, or being formed from the same piece of
material.
[0027] A distribution component is preferably detachable and may be
disposable, reusable, or recyclable. The dressing 110 and the
container 115 are illustrative of distribution components. A fluid
conductor is another illustrative example of a distribution
component. A "fluid conductor," in this context, broadly includes a
tube, pipe, hose, conduit, or other structure with one or more
lumina or open pathways adapted to convey a fluid between two ends.
Typically, a tube is an elongated, cylindrical structure with some
flexibility, but the geometry and rigidity may vary. Moreover, some
fluid conductors may be molded into or otherwise integrally
combined with other components. Distribution components may also
include or comprise interfaces or fluid ports to facilitate
coupling and de-coupling other components. In some embodiments, for
example, a dressing interface may facilitate coupling a fluid
conductor to the dressing 110. For example, such a dressing
interface may be a SENSAT.R.A.C..TM. Pad available from Kinetic
Concepts, Inc. of San Antonio, Tex.
[0028] A negative-pressure supply, such as the negative-pressure
source 105, may be a reservoir of air at a negative pressure or may
be a manual or electrically-powered device. Examples of a suitable
negative-pressure supply may include a vacuum pump, a suction pump,
a wall suction port available at many healthcare facilities, or a
micro-pump. "Negative pressure" generally refers to a pressure less
than a local ambient pressure, such as the ambient pressure in a
local environment external to a sealed therapeutic environment. In
many cases, the local ambient pressure may also be the atmospheric
pressure at which a tissue site is located. Alternatively, the
pressure may be less than a hydrostatic pressure associated with
tissue at the tissue site. Unless otherwise indicated, values of
pressure stated herein are gauge pressures. References to increases
in negative pressure typically refer to a decrease in absolute
pressure, while decreases in negative pressure typically refer to
an increase in absolute pressure. While the amount and nature of
negative pressure applied to a tissue site may vary according to
therapeutic requirements, the pressure is generally a low vacuum,
also commonly referred to as a rough vacuum, between -5 mm Hg (-667
Pa) and -500 mm Hg (-66.7 kPa). Common therapeutic ranges are
between -50 mm Hg (-6.7 kPa) and -300 mm Hg (-39.9 kPa).
[0029] The container 115 is representative of a container,
canister, pouch, or other storage component, which can be used to
manage exudates and other fluids withdrawn from a tissue site. In
many environments, a rigid container may be preferred or required
for collecting, storing, and disposing of fluids. In other
environments, fluids may be properly disposed of without rigid
container storage, and a re-usable container could reduce waste and
costs associated with negative-pressure therapy.
[0030] A controller, such as the controller 120, may be a
microprocessor or computer programmed to operate one or more
components of the therapy system 100, such as the negative-pressure
source 105. In some embodiments, for example, the controller 120
may be a microcontroller, which generally comprises an integrated
circuit containing a processor core and a memory programmed to
directly or indirectly control one or more operating parameters of
the therapy system 100. Operating parameters may include the power
applied to the negative-pressure source 105, the pressure generated
by the negative-pressure source 105, or the pressure distributed to
the tissue interface 135, for example. The controller 120 is also
preferably configured to receive one or more input signals, such as
a feedback signal, and programmed to modify one or more operating
parameters based on the input signals.
[0031] Sensors, such as the first sensor 125 and the second sensor,
130 are generally known in the art as any apparatus operable to
detect or measure a physical phenomenon or property, and generally
provide a signal indicative of the phenomenon or property that is
detected or measured. For example, the first sensor 125 and the
second sensor 130 may be configured to measure one or more
operating parameters of the therapy system 100. In some
embodiments, the first sensor 125 may be a transducer configured to
measure pressure in a pneumatic pathway and convert the measurement
to a signal indicative of the pressure measured. In some
embodiments, for example, the first sensor 125 may be a
piezo-resistive strain gauge. The second sensor 130 may optionally
measure operating parameters of the negative-pressure source 105,
such as a voltage or current, in some embodiments. Preferably, the
signals from the first sensor 125 and the second sensor 130 are
suitable as an input signal to the controller 120, but some signal
conditioning may be appropriate in some embodiments. For example,
the signal may need to be filtered or amplified before it can be
processed by the controller 120. Typically, the signal is an
electrical signal, but may be represented in other forms, such as
an optical signal.
[0032] The tissue interface 135 can be generally adapted to
partially or fully contact a tissue site. The tissue interface 135
may take many forms and may have many sizes, shapes, or
thicknesses, depending on a variety of factors, such as the type of
treatment being implemented or the nature and size of a tissue
site. For example, the size and shape of the tissue interface 135
may be adapted to the contours of deep and irregular shaped tissue
sites. Moreover, any or all of the surfaces of the tissue interface
135 may have projections or an uneven, coarse, or jagged profile
that can induce strains and stresses on a tissue site, which can
promote granulation at the tissue site.
[0033] In some embodiments, the tissue interface 135 may comprise
or consist essentially of a manifold. A "manifold" in this context
generally includes any substance or structure providing a plurality
of pathways adapted to collect or distribute fluid across a tissue
site under pressure. For example, a manifold may be adapted to
receive negative pressure from a source and distribute negative
pressure through multiple apertures across a tissue site, which may
have the effect of collecting fluid from across a tissue site and
drawing the fluid toward the source. In some embodiments, the fluid
path may be reversed or a secondary fluid path may be provided to
facilitate delivering fluid, such as fluid from a source of
instillation solution, across a tissue site.
[0034] In some illustrative embodiments, the pathways of a manifold
may be interconnected to improve distribution or collection of
fluids across a tissue site. In some illustrative embodiments, a
manifold may be a porous foam material having interconnected cells
or pores. For example, open-cell foam, porous tissue collections,
and other porous material such as gauze or felted mat generally
include pores, edges, and/or walls adapted to form interconnected
fluid channels. Liquids, gels, and other foams may also include, or
be cured to include, apertures and fluid pathways. In some
embodiments, a manifold may additionally or alternatively comprise
projections that form interconnected fluid pathways. For example, a
manifold may be molded to provide surface projections that define
interconnected fluid pathways.
[0035] The average pore size of foam may vary according to needs of
a prescribed therapy. For example, in some embodiments, the tissue
interface 135 may comprise or consist essentially of foam having
pore sizes in a range of 400-600 microns. The tensile strength of
the tissue interface 135 may also vary according to needs of a
prescribed therapy. For example, the tensile strength of foam may
be increased for instillation of topical treatment solutions. In
some examples, the tissue interface 135 may be reticulated
polyurethane foam such as found in GRANUFOAM.TM. dressing or V.A.C.
VERAFLO.TM. dressing, both available from Kinetic Concepts, Inc. of
San Antonio, Tex.
[0036] The tissue interface 135 may further promote granulation at
a tissue site when pressure within the sealed therapeutic
environment is reduced. For example, any or all of the surfaces of
the tissue interface 135 may have an uneven, coarse, or jagged
profile that can induce microstrains and stresses at a tissue site
if negative pressure is applied through the tissue interface
135.
[0037] In some embodiments, the tissue interface 135 may be
constructed from bioresorbable materials. Suitable bioresorbable
materials may include, without limitation, a polymeric blend of
polylactic acid (PLA) and polyglycolic acid (PGA). The polymeric
blend may also include, without limitation, polycarbonates,
polyfumarates, and capralactones. The tissue interface 135 may
further serve as a scaffold for new cell-growth, or a scaffold
material may be used in conjunction with the tissue interface 135
to promote cell-growth. A scaffold is generally a substance or
structure used to enhance or promote the growth of cells or
formation of tissue, such as a three-dimensional porous structure
that provides a template for cell growth. Illustrative examples of
scaffold materials include calcium phosphate, collagen, PLA/PGA,
coral hydroxy apatites, carbonates, or processed allograft
materials.
[0038] In some embodiments, the cover 140 may provide a bacterial
barrier and protection from physical trauma. The cover 140 may also
be constructed from a material that can reduce evaporative losses
and provide a fluid seal between two components or two
environments, such as between a therapeutic environment and a local
external environment. The cover 140 may comprise or consist of, for
example, an elastomeric film or membrane that can provide a seal
adequate to maintain a negative pressure at a tissue site for a
given negative-pressure source. The cover 140 may have a high
moisture-vapor transmission rate (MVTR) in some applications. For
example, the MVTR may be at least 450 grams per square meter per
twenty-four hours in some embodiments, measured using an upright
cup technique according to ASTM E96/E96M Upright Cup Method at
38.degree. C. and 10% relative humidity (RH). In some embodiments,
an MVTR up to 5,000 grams per square meter per twenty-four hours
may provide effective breathability and mechanical properties.
[0039] In some example embodiments, the cover 140 may be a polymer
drape, such as a polyurethane film, that is permeable to water
vapor but impermeable to liquid. Such drapes typically have a
thickness in the range of 25-50 microns. For permeable materials,
the permeability generally should be low enough that a desired
negative pressure may be maintained. For example, the cover 140 may
comprise one or more of the following materials: polyurethane (PU),
such as hydrophilic polyurethane; cellulosics; hydrophilic
polyamides; polyvinyl alcohol; polyvinyl pyrrolidone; hydrophilic
acrylics; silicones, such as hydrophilic silicone elastomers;
natural rubbers; polyisoprene; styrene butadiene rubber;
chloroprene rubber; polybutadiene; nitrile rubber; butyl rubber;
ethylene propylene rubber; ethylene propylene diene monomer;
chlorosulfonated polyethylene; polysulfide rubber; ethylene vinyl
acetate (EVA); co-polyester; and polyether block polymide
copolymers. Such materials are commercially available as, for
example, Tegaderm.RTM. drape, commercially available from 3M
Company, Minneapolis Minn.; polyurethane (PU) drape, commercially
available from Avery Dennison Corporation, Pasadena, Calif.;
polyether block polyamide copolymer (PEBAX), for example, from
Arkema S.A., Colombes, France; and Inspire 2301 and Inpsire 2327
polyurethane films, commercially available from Expopack Advanced
Coatings, Wrexham, United Kingdom. In some embodiments, the cover
140 may comprise INSPIRE 2301 having an MVTR (upright cup
technique) of 2600 g/m.sup.2/24 hours and a thickness of about 30
microns.
[0040] An attachment device may be used to attach the cover 140 to
an attachment surface, such as undamaged epidermis, a gasket, or
another cover. The attachment device may take many forms. For
example, an attachment device may be a medically-acceptable,
pressure-sensitive adhesive configured to bond the cover 140 to
epidermis around a tissue site. In some embodiments, for example,
some or all of the cover 140 may be coated with an adhesive, such
as an acrylic adhesive, which may have a coating weight of 25-65
grams per square meter (g.s.m.). Thicker adhesives, or combinations
of adhesives, may be applied in some embodiments to improve the
seal and reduce leaks. Other example embodiments of an attachment
device may include a double-sided tape, paste, hydrocolloid,
hydrogel, silicone gel, or organogel.
[0041] The solution source 145 may also be representative of a
container, canister, pouch, bag, or other storage component, which
can provide a solution for instillation therapy. Compositions of
solutions may vary according to a prescribed therapy, but examples
of solutions that may be suitable for some prescriptions include
hypochlorite-based solutions, silver nitrate (0.5%), sulfur-based
solutions, biguanides, cationic solutions, and isotonic
solutions.
[0042] FIG. 2 is a graph illustrating additional details of an
example control mode that may be associated with some embodiments
of the controller 120. In some embodiments, the controller 120 may
have a continuous pressure mode, in which the negative-pressure
source 105 is operated to provide a constant target negative
pressure, as indicated by line 205 and line 210, for the duration
of treatment or until manually deactivated. Additionally or
alternatively, the controller may have an intermittent pressure
mode, as illustrated in the example of FIG. 2. In FIG. 2, the
x-axis represents time, and the y-axis represents negative pressure
generated by the negative-pressure source 105 over time. In the
example of FIG. 2, the controller 120 can operate the
negative-pressure source 105 to cycle between a target pressure and
atmospheric pressure. For example, the target pressure may be set
at a value of 125 mmHg, as indicated by line 205, for a specified
period of time (e.g., 5 min), followed by a specified period of
time (e.g., 2 min) of deactivation, as indicated by the gap between
the solid lines 215 and 220. The cycle can be repeated by
activating the negative-pressure source 105, as indicated by line
220, which can form a square wave pattern between the target
pressure and atmospheric pressure.
[0043] In some example embodiments, the increase in
negative-pressure from ambient pressure to the target pressure may
not be instantaneous. For example, the negative-pressure source 105
and the dressing 110 may have an initial rise time, as indicated by
the dashed line 225. The initial rise time may vary depending on
the type of dressing and therapy equipment being used. For example,
the initial rise time for one therapy system may be in a range of
about 20-30 mmHg/second and in a range of about 5-10 mmHg/second
for another therapy system. If the therapy system 100 is operating
in an intermittent mode, the repeating rise time, as indicated by
the solid line 220, may be a value substantially equal to the
initial rise time as indicated by the dashed line 225.
[0044] FIG. 3 is a graph illustrating additional details that may
be associated with another example pressure control mode in some
embodiments of the therapy system 100. In FIG. 3, the x-axis
represents time and the y-axis represents negative pressure
generated by the negative-pressure source 105. The target pressure
in the example of FIG. 3 can vary with time in a dynamic pressure
mode. For example, the target pressure may vary in the form of a
triangular waveform, varying between a negative pressure of 50 and
125 mmHg with a rise time 305 set at a rate of +25 mmH g/min. and a
descent time 310 set at -25 mmH g/min. In other embodiments of the
therapy system 100, the triangular waveform may vary between
negative pressure of 25 and 125 mmHg with a rise time 305 set at a
rate of +30 mmH g/min and a descent time 310 set at -30 mmH
g/min.
[0045] In some embodiments, the controller 120 may control or
determine a variable target pressure in a dynamic pressure mode,
and the variable target pressure may vary between a maximum and
minimum pressure value that may be set as an input prescribed by an
operator as the range of desired negative pressure. The variable
target pressure may also be processed and controlled by the
controller 120, which can vary the target pressure according to a
predetermined waveform, such as a triangular waveform, a sine
waveform, or a saw-tooth waveform. In some embodiments, the
waveform may be set by an operator as the predetermined or
time-varying negative pressure desired for therapy.
[0046] FIG. 4 is an assembly view of an example of the dressing 110
of FIG. 1, illustrating additional details that may be associated
with some embodiments in which the tissue interface 135 comprises
more than one layer. In the example of FIG. 2, the tissue interface
135 comprises a manifold 405, a polymer film 410, and a gel layer
415. In some embodiments, the manifold 405 may be disposed adjacent
to the polymer film 410, and the gel layer 415 may be disposed
adjacent to the polymer film 410 opposite the manifold 405. For
example, the manifold 405, the polymer film 410, and the gel layer
415 may be stacked so that the manifold 405 is in contact with the
polymer film 410, and the polymer film 410 is in contact with the
manifold 405 and the gel layer 415. One or more of the manifold
405, the polymer film 410, and the gel layer 415 may also be bonded
to an adjacent layer in some embodiments.
[0047] The manifold 405 may comprise or consist essentially of a
means for collecting or distributing fluid across the tissue
interface 135 under pressure. For example, the manifold 405 may be
adapted to receive negative pressure from a source and distribute
negative pressure through multiple apertures across the tissue
interface 135, which may have the effect of collecting fluid from
across a tissue site and drawing the fluid toward the source. In
some embodiments, the fluid path may be reversed or a secondary
fluid path may be provided to facilitate delivering fluid, such as
from a source of instillation solution, across the tissue interface
135.
[0048] In some illustrative embodiments, the manifold 405 may
comprise a plurality of pathways, which can be interconnected to
improve distribution or collection of fluids. In some embodiments,
the manifold 405 may comprise or consist essentially of a porous
material having interconnected fluid pathways. For example,
open-cell foam, porous tissue collections, and other porous
material such as gauze or felted mat generally include pores,
edges, and/or walls adapted to form interconnected fluid channels.
Liquids, gels, and other foams may also include or be cured to
include apertures and fluid pathways. In some embodiments, the
manifold 405 may additionally or alternatively comprise projections
that form interconnected fluid pathways. For example, the manifold
405 may be molded to provide surface projections that define
interconnected fluid pathways. Any or all of the surfaces of the
manifold 405 may have an uneven, coarse, or jagged profile.
[0049] In some embodiments, the manifold 405 may comprise or
consist essentially of reticulated foam having pore sizes and free
volume that may vary according to needs of a prescribed therapy.
For example, reticulated foam having a free volume of at least 90%
may be suitable for many therapy applications, and foam having an
average pore size in a range of 400-600 microns (40-50 pores per
inch) may be particularly suitable for some types of therapy. The
tensile strength of the manifold 405 may also vary according to
needs of a prescribed therapy. For example, the tensile strength of
the manifold 405 may be increased for instillation of topical
treatment solutions. The 25% compression load deflection of the
manifold 405 may be at least 0.35 pounds per square inch, and the
65% compression load deflection may be at least 0.43 pounds per
square inch. In some embodiments, the tensile strength of the
manifold 405 may be at least 10 pounds per square inch. The
manifold 405 may have a tear strength of at least 2.5 pounds per
inch. In some embodiments, the manifold 405 may be foam comprised
of polyols such as polyester or polyether, isocyanate such as
toluene diisocyanate, and polymerization modifiers such as amines
and tin compounds. In one non-limiting example, the manifold 405
may be a reticulated polyurethane ether foam such as used in
GRANUFOAM.TM. dressing or V.A.C. VERAFLO.TM. dressing, both
available from KCI of San Antonio, Tex.
[0050] The thickness of the manifold 405 may also vary according to
needs of a prescribed therapy. For example, the thickness of the
manifold 405 may be decreased to relieve stress on other layers and
to reduce tension on peripheral tissue. The thickness of the
manifold 405 can also affect the conformability of the manifold
405. In some embodiments, a thickness in a range of about 5
millimeters to 10 millimeters may be suitable.
[0051] The polymer film 410 may comprise or consist essentially of
a means for controlling or managing fluid flow. In some
embodiments, the polymer film 410 may comprise or consist
essentially of a liquid-impermeable, elastomeric polymer. The
polymer film 410 may also have a smooth or matte surface texture in
some embodiments. A glossy or shiny finish better or equal to a
grade B3 according to the SPI (Society of the Plastics Industry)
standards may be particularly advantageous for some applications.
In some embodiments, variations in surface height may be limited to
acceptable tolerances. For example, the surface of the polymer film
410 may have a substantially flat surface, with height variations
limited to 0.2 millimeters over a centimeter.
[0052] In some embodiments, the polymer film 410 may be
hydrophobic. The hydrophobicity of the polymer film 410 may vary,
and may have a contact angle with water of at least ninety degrees
in some embodiments. In some embodiments the polymer film 410 may
have a contact angle with water of no more than 150 degrees. For
example, in some embodiments, the contact angle of the polymer film
410 may be in a range of at least 90 degrees to about 120 degrees
or in a range of at least 120 degrees to 150 degrees. Water contact
angles can be measured using any standard apparatus. Although
manual goniometers can be used to visually approximate contact
angles, contact angle measuring instruments can often include an
integrated system involving a level stage, liquid dropper such as a
syringe, camera, and software designed to calculate contact angles
more accurately and precisely, among other things. Non-limiting
examples of such integrated systems may include the FT.ANG.125,
FT.ANG.200, FT.ANG.2000 , and FT.ANG.4000 systems, all commercially
available from First Ten Angstroms, Inc., of Portsmouth, Va., and
the DTA25, DTA30, and DTA100 systems, all commercially available
from Kruss GmbH of Hamburg, Germany. Unless otherwise specified,
water contact angles herein are measured using deionized and
distilled water on a level sample surface for a sessile drop added
from a height of no more than 5 cm in air at 20-25.degree. C. and
20-50% relative humidity. Contact angles reported herein represent
averages of 5-9 measured values, discarding both the highest and
lowest measured values. The hydrophobicity of the polymer film 410
may be further enhanced with a hydrophobic coating of other
materials, such as silicones and fluorocarbons, either as coated
from a liquid or plasma coated.
[0053] The polymer film 410 may also be suitable for welding to
other layers, including the manifold 405. For example, the polymer
film 410 may be adapted for welding to polyurethane foams using
heat, radio frequency (RF) welding, or other methods to generate
heat, such as ultrasonic welding. RF welding may be particularly
suitable for more polar materials, such as polyurethane,
polyamides, polyesters and acrylates. Sacrificial polar interfaces
may be used to facilitate RF welding of less polar film materials,
such as polyethylene.
[0054] The area density of the polymer film 410 may vary according
to a prescribed therapy or application. In some embodiments, an
area density of less than 40 grams per square meter may be
suitable, and an area density of about 20-30 grams per square meter
may be particularly advantageous for some applications.
[0055] In some embodiments, for example, the polymer film 410 may
comprise or consist essentially of a hydrophobic polymer, such as a
polyethylene film. The simple and inert structure of polyethylene
can provide a surface that interacts little, if at all, with
biological tissues and fluids. Such a surface may encourage the
free flow of liquid and low adherence, which can be particularly
advantageous for many applications. More polar films suitable for
laminating to a polyethylene film include polyamide, co-polyesters,
ionomers, and acrylics. To aid in the bond between a polyethylene
and polar film, tie layers may be used, such as ethylene vinyl
acetate or modified polyurethanes. An ethyl methyl acrylate (EMA)
film may also have suitable hydrophobic and welding properties for
some configurations.
[0056] As illustrated in the example of FIG. 4, the polymer film
410 may have one or more fluid restrictions 420, which can be
distributed uniformly or randomly across the polymer film 410. The
fluid restrictions 420 may be bi-directional and
pressure-responsive. For example, the fluid restrictions 420 can
generally comprise or consist essentially of an elastic passage
through the polymer film 410 that is normally unstrained to
substantially reduce liquid flow, and the elastic passage can
expand in response to a pressure gradient. In some embodiments, the
fluid restrictions 420 may comprise or consist essentially of
perforations in the polymer film 410. Perforations may be formed by
removing material from the polymer film 410. For example,
perforations may be formed by cutting through the polymer film 410,
which may also deform the edges of the perforations in some
embodiments. In the absence of a pressure gradient across the
perforations, the passages may be sufficiently small to form a seal
or flow restriction, which can substantially reduce or prevent
liquid flow. Additionally or alternatively, one or more of the
fluid restrictions 420 may be an elastomeric valve that is normally
closed when unstrained to substantially prevent liquid flow and can
open in response to a pressure gradient. A fenestration in the
polymer film 410 may be a suitable valve for some applications.
Fenestrations may also be formed by removing material from the
polymer film 410, but the amount of material removed and the
resulting dimensions of the fenestrations may be up to an order of
magnitude less than perforations, and may not deform the edges.
[0057] For example, some embodiments of the fluid restrictions 420
may comprise or consist essentially of one or more slots or
combinations of slots in the polymer film 410. In some examples,
the fluid restrictions 420 may comprise or consist of linear slots
having a length less than 4 millimeters and a width less than 1
millimeter. The length may be at least 2 millimeters, and the width
may be at least 0.4 millimeters in some embodiments. A length of
about 3 millimeters and a width of about 0.8 millimeter may be
particularly suitable for many applications. A tolerance of about
0.1 millimeter may also be acceptable. Slots of such configurations
may function as imperfect valves that substantially reduce liquid
flow in a normally closed or resting state. For example, such slots
may form a flow restriction without being completely closed or
sealed. The slots can expand or open wider in response to a
pressure gradient to allow increased liquid flow.
[0058] The gel layer 415 may comprise or consist essentially of a
fixation layer having a tacky surface and may be formed from a soft
polymer suitable for providing a fluid seal with a tissue site. The
gel layer 415 may be a polymer gel having a coating weight of about
450 g.s.m., and may have a substantially flat surface in some
examples. For example, the gel layer 415 may comprise, without
limitation, a silicone gel, hydrocolloid, hydrogel, polyurethane
gel, polyolefin gel, hydrogenated styrenic copolymer gel, or a
foamed gel. In some embodiments, the gel layer 415 may have a
thickness between about 200 microns (.mu.m) and about 1000 microns
(.mu.m). In some embodiments, the gel layer 415 may have a hardness
between about 5 Shore OO and about 80 Shore OO. Further, the gel
layer 415 may be comprised of hydrophobic or hydrophilic
materials.
[0059] The gel layer 415 may have a periphery 425 surrounding or
around an interior portion 430, and apertures 435 disposed through
the periphery 425 and the interior portion 430. The interior
portion 430 may correspond to a surface area of the manifold 405 in
some examples. The gel layer 415 may also have corners 440 and
edges 445. The corners 440 and the edges 445 may be part of the
periphery 425. The gel layer 415 may have an interior border 450
around the interior portion 430, disposed between the interior
portion 430 and the periphery 425. The interior border 450 may be
substantially free of the apertures 435, as illustrated in the
example of FIG. 4. In some examples, as illustrated in FIG. 4, the
interior portion 430 may be symmetrical and centrally disposed in
the gel layer 415.
[0060] The apertures 435 may have a uniform distribution pattern or
may be randomly distributed in the gel layer 415. The apertures 435
in the gel layer 415 may have many shapes, including circles,
squares, stars, ovals, polygons, slits, complex curves, rectilinear
shapes, triangles, for example, or may have some combination of
such shapes.
[0061] Each of the apertures 435 may have uniform or similar
geometric properties. For example, in some embodiments, each of the
apertures 435 may be circular apertures, having substantially the
same diameter. In some embodiments, the diameter of each of the
apertures 435 may be between about 1 millimeter and about 50
millimeters. In other embodiments, the diameter of each of the
apertures 435 may be between about 1 millimeter and about 20
millimeters.
[0062] In other embodiments, geometric properties of the apertures
435 may vary. For example, the diameter of the apertures 435 may
vary depending on the position of the apertures 435 in the gel
layer 415, as illustrated in FIG. 4. In some embodiments, the
diameter of the apertures 435 in the periphery 425 of the gel layer
415 may be larger than the diameter of the apertures 435 in the
interior portion 430 of the gel layer 415. For example, in some
embodiments, the apertures 435 disposed in the periphery 425 may
have a diameter between about 9.8 millimeters and about 10.2
millimeters. In some embodiments, the apertures 435 disposed in the
corners 440 may have a diameter between about 7.75 millimeters and
about 8.75 millimeters. In some embodiments, the apertures 435
disposed in the interior portion 430 may have a diameter between
about 1.8 millimeters and about 2.2 millimeters. In other
embodiments, the apertures 435 disposed in the interior portion 430
may be slots having a width of about 2 millimeters and a length of
about 3 millimeters.
[0063] At least one of the apertures 435 in the periphery 425 of
the gel layer 415 may be positioned at the edges 445 of the
periphery 425 and may have an interior cut open or exposed at the
edges 445 that is in fluid communication in a lateral direction
with the edges 445. The lateral direction may refer to a direction
toward the edges 445 and in the same plane as the gel layer 415. As
shown in the example of FIG. 4, the apertures 435 in the periphery
425 may be positioned proximate to or at the edges 445 and in fluid
communication in a lateral direction with the edges 445. The
apertures 435 positioned proximate to or at the edges 445 may be
spaced substantially equidistant around the periphery 425 as shown
in the example of FIG. 4. Alternatively, the spacing of the
apertures 435 proximate to or at the edges 445 may be
irregular.
[0064] In the example of FIG. 4, the dressing 110 may further
include an attachment device, such as an adhesive 455. The adhesive
455 may be, for example, a medically-acceptable, pressure-sensitive
adhesive that extends about a periphery, a portion, or the entire
cover 140. In some embodiments, for example, the adhesive 455 may
be an acrylic adhesive having a coating weight between 25-65 grams
per square meter (g.s.m.). Thicker adhesives, or combinations of
adhesives, may be applied in some embodiments to improve the seal
and reduce leaks. The adhesive 455 may be a layer having
substantially the same shape as the periphery 425. In some
embodiments, such a layer of the adhesive 455 may be continuous or
discontinuous. Discontinuities in the adhesive 455 may be provided
by apertures or holes (not shown) in the adhesive 455. The
apertures or holes in the adhesive 455 may be formed after
application of the adhesive 455 or by coating the adhesive 455 in
patterns on a carrier layer, such as, for example, a side of the
cover 140. Apertures or holes in the adhesive 455 may also be sized
to enhance the moisture-vapor transfer rate of the dressing 110 in
some example embodiments.
[0065] As illustrated in the example of FIG. 4, in some
embodiments, a release liner 460 may be attached to or positioned
adjacent to the gel layer 415 to protect the adhesive 455 prior to
use. The release liner 460 may also provide stiffness to assist
with, for example, deployment of the dressing 110. Examples of the
release liner 460 may include a casting paper, a film, or
polyethylene. Further, in some embodiments, the release liner 460
may be a polyester material such as polyethylene terephthalate
(PET), or similar polar semi-crystalline polymer. The use of a
polar semi-crystalline polymer for the release liner 460 may
substantially preclude wrinkling or other deformation of the
dressing 110. For example, the polar semi-crystalline polymer may
be highly orientated and resistant to softening, swelling, or other
deformation that may occur when brought into contact with
components of the dressing 110 or when subjected to temperature or
environmental variations, or sterilization. In some embodiments,
the release liner 460 may have a surface texture that may be
imprinted on an adjacent layer, such as the gel layer 415. Further,
a release agent may be disposed on a side of the release liner 460
that is configured to contact the gel layer 415. For example, the
release agent may be a silicone coating and may have a release
factor suitable to facilitate removal of the release liner 460 by
hand and without damaging or deforming the dressing 110. In some
embodiments, the release agent may be a fluorocarbon or a
fluorosilicone, for example. In other embodiments, the release
liner 460 may be uncoated or otherwise used without a release
agent.
[0066] FIG. 4 also illustrates one example of a fluid conductor 465
and a dressing interface 470. As shown in the example of FIG. 4,
the fluid conductor 465 may be a flexible tube, which can be
fluidly coupled on one end to the dressing interface 470. The
dressing interface 470 may be an elbow connector, as shown in the
example of FIG. 4, which can be placed over an aperture 475 in the
cover 140 to provide a fluid path between the fluid conductor 465
and the tissue interface 135.
[0067] FIG. 5 is a schematic view of an example of the polymer film
410, illustrating additional details that may be associated with
some embodiments. As illustrated in the example of FIG. 5, the
fluid restrictions 420 may each consist essentially of one or more
linear slots having a length of about 3 millimeters. FIG. 5
additionally illustrates an example of a uniform distribution
pattern of the fluid restrictions 420. In FIG. 5, the fluid
restrictions 420 are substantially coextensive with the polymer
film 410 and are distributed across the polymer film 410 in a grid
of parallel rows and columns, in which the slots are also mutually
parallel to each other. In some embodiments, the rows may be spaced
about 3 millimeters on center, and the fluid restrictions 420
within each of the rows may be spaced about 3 millimeters on
center, as illustrated in the example of FIG. 5. The fluid
restrictions 420 in adjacent rows may be aligned or offset. For
example, adjacent rows may be offset, as illustrated in FIG. 5, so
that the fluid restrictions 420 are aligned in alternating rows and
separated by about 6 millimeters. The spacing of the fluid
restrictions 420 may vary in some embodiments to increase the
density of the fluid restrictions 420 according to therapeutic
requirements.
[0068] FIG. 6 is a schematic view of an example configuration of
the apertures 435, illustrating additional details that may be
associated with some embodiments of the gel layer 415. In some
embodiments, the apertures 435 illustrated in FIG. 6 may be
associated only with the interior portion 430. In the example of
FIG. 6, the apertures 435 are generally circular and have a
diameter of about 2 millimeters. FIG. 6 also illustrates an example
of a uniform distribution pattern of the apertures 435. In FIG. 6,
the apertures 435 are distributed in a grid of parallel rows and
columns. Within each row and column, the apertures 435 may be
equidistant from each other, as illustrated in the example of FIG.
6. FIG. 6 illustrates one example configuration of the apertures
435 that may be particularly suitable for many applications, in
which the apertures 435 are spaced about 6 millimeters apart along
each row and column, with a 3 millimeter offset.
[0069] FIG. 7 is a schematic view of an example of the gel layer
415 having the configuration of apertures 435 of FIG. 6 overlaid on
the polymer film 410 of FIG. 5, illustrating additional details
that may be associated with some example embodiments of the tissue
interface 135. For example, as illustrated in FIG. 7, the fluid
restrictions 420 may be aligned, overlapping, in registration with,
or otherwise fluidly coupled to the apertures 435 in some
embodiments. In some embodiments, one or more of the fluid
restrictions 420 may be registered with the apertures 435 only in
the interior portion 430 or only partially registered with the
apertures 435. The fluid restrictions 420 in the example of FIG. 7
are generally configured so that each of the fluid restrictions 420
is registered with only one of the apertures 435. In other
examples, one or more of the fluid restrictions 420 may be
registered with more than one of the apertures 435. For example,
any one or more of the fluid restrictions 420 may be a perforation
or a fenestration that extends across two or more of the apertures
435. Additionally or alternatively, one or more of the fluid
restrictions 420 may not be registered with any of the apertures
435.
[0070] As illustrated in the example of FIG. 7, the apertures 435
may be sized to expose a portion of the polymer film 410, the fluid
restrictions 420, or both through the gel layer 415. In some
embodiments, each of the apertures 435 may be sized to expose no
more than two of the fluid restrictions 420. In some examples, the
length of each of the fluid restrictions 420 may be substantially
equal to or less than the diameter of each of the apertures 435. In
some embodiments, the average dimensions of the fluid restrictions
420 are substantially similar to the average dimensions of the
apertures 435. For example, the apertures 435 may be elliptical in
some embodiments, and the length of each of the fluid restrictions
420 may be substantially equal to the major axis or the minor axis.
In some embodiments, though, the dimensions of the fluid
restrictions 420 may exceed the dimensions of the apertures 435,
and the size of the apertures 435 may limit the effective size of
the fluid restrictions 420 exposed to the lower surface of the
dressing 110.
[0071] FIG. 8 is a flow diagram illustrating an example method 800
of manufacturing some components of the dressing 110. In the
example of FIG. 8, a first layer of the dressing 110 can be
perforated at 805. For example, the first layer may be the gel
layer 415, and the apertures 435 may be formed by a laser or by
other suitable techniques for forming the apertures 435 in the gel
layer 415. The first layer with perforations can be placed on an
assembly substrate at 810. For example, the first layer can be held
on a web and then on a roll or liner. An index of the perforations
may be created at 815, and the laser or other cutting means may be
calibrated at 820 based on the index. A second layer may be coupled
to the first layer at 825. The second layer may be the polymer film
410, for example, which may be cut to a preferred size and shape
and then loaded and fixed to the gel layer 415. Slots (or slits)
may be cut in the second layer through the apertures in the first
layer at 830. For example, a combined laminate of the polymer film
410 and the gel layer 415 may be presented to a laser, where the
laser calibrates the position of a laser mask to the underside of
the combined laminate, referencing the apertures 435 to calibrate
its position. The laser can then be fired, creating the fluid
restrictions 420 in the polymer film 410, centrally registered
within the apertures 435 and having a length substantially equal to
or less than the length or diameter of each of the apertures 435.
In some embodiments, the fluid restrictions 420 may have a length
slightly longer than the length or diameter of the apertures 435
without affecting the performance of the dressing 110.
[0072] One or more of the components of the dressing 110 may
additionally be treated with an antimicrobial agent in some
embodiments. For example, the manifold 405 may be a foam, mesh, or
non-woven coated with an antimicrobial agent. In some embodiments,
the manifold 405 may comprise antimicrobial elements, such as
fibers coated with an antimicrobial agent. Additionally or
alternatively, some embodiments of the polymer film 410 may be a
polymer coated or mixed with an antimicrobial agent. In other
examples, the fluid conductor 465 may additionally or alternatively
be treated with one or more antimicrobial agents. Suitable
antimicrobial agents may include, for example, metallic silver,
PHMB, iodine or its complexes and mixes such as povidone iodine,
copper metal compounds, chlorhexidine, or some combination of these
materials.
[0073] Individual components of the dressing 110 may be bonded or
otherwise secured to one another with a solvent or non-solvent
adhesive or with thermal welding, for example, without adversely
affecting fluid management. Further, the manifold 405 or the
polymer film 410 may be coupled to the border 450 of the gel layer
415 in any suitable manner, such as with a weld or an adhesive, for
example.
[0074] The manifold 405, the polymer film 410, the gel layer 415,
the cover 140, or various combinations may be assembled before
application or in situ. For example, the cover 140 may be laminated
to the manifold 405, and the polymer film 410 may be laminated to
the manifold 405 opposite the cover 140 in some embodiments. The
gel layer 415 may also be coupled to the polymer film 410 opposite
the manifold 405 in some embodiments. In some embodiments, one or
more layers of the tissue interface 135 may coextensive. For
example, the manifold 405 may be coextensive with the polymer film
410, as illustrated in the embodiment of FIG. 4. In some
embodiments, the dressing 110 may be provided as a single,
composite dressing. For example, the gel layer 415 may be coupled
to the cover 140 to enclose the manifold 405 and the polymer film
410, wherein the gel layer 415 is configured to face a tissue
site.
[0075] In use, the release liner 460 (if included) may be removed
to expose the gel layer 415, which may be placed within, over, on,
or otherwise proximate to a tissue site, particularly a surface
tissue site and adjacent epidermis. The gel layer 415 and the
polymer film 410 may be interposed between the manifold 405 and a
tissue site, which can substantially reduce or eliminate adverse
interaction with the manifold 405. For example, the gel layer 415
may be placed over a surface wound (including edges of the wound)
and undamaged epidermis to prevent direct contact with the manifold
405. Treatment of a surface wound, or placement of the dressing 110
on a surface wound, includes placing the dressing 110 immediately
adjacent to the surface of the body or extending over at least a
portion of the surface of the body. Treatment of a surface wound
does not include placing the dressing 110 wholly within the body or
wholly under the surface of the body, such as placing a dressing
within an abdominal cavity. In some applications, the interior
portion 430 of the gel layer 415 may be positioned adjacent to,
proximate to, or covering a tissue site. In some applications, at
least some portion of the polymer film 410, the fluid restrictions
420, or both may be exposed to a tissue site through the gel layer
415. The periphery 425 of the gel layer 415 may be positioned
adjacent to or proximate to tissue around or surrounding the tissue
site. The gel layer 415 may be sufficiently tacky to hold the
dressing 110 in position, while also allowing the dressing 110 to
be removed or re-positioned without trauma to a tissue site.
[0076] Removing the release liner 460 can also expose the adhesive
455, and the cover 140 may be attached to an attachment surface.
For example, the cover 140 may be attached to epidermis peripheral
to a tissue site, around the manifold 405 and the polymer film 410.
The adhesive 455 may be in fluid communication with an attachment
surface through the apertures 435 in at least the periphery 425 of
the gel layer 415 in some embodiments. The adhesive 455 may also be
in fluid communication with the edges 445 through the apertures 435
exposed at the edges 445.
[0077] Once the dressing 110 is in a desired position, the adhesive
455 may be pressed through the apertures 435 to bond the dressing
110 to the attachment surface. The apertures 435 at the edges 445
may permit the adhesive 455 to flow around the edges 445 for
enhancing the adhesion of the edges 445 to an attachment
surface.
[0078] In some embodiments, apertures or holes in the gel layer 415
may be sized to control the amount of the adhesive 455 in fluid
communication with the apertures 435. For a given geometry of the
corners 440, the relative sizes of the apertures 435 may be
configured to maximize the surface area of the adhesive 455 exposed
and in fluid communication through the apertures 435 at the corners
440. For example, as shown in FIG. 4, the edges 445 may intersect
at substantially a right angle, or about 90 degrees, to define the
corners 440. In some embodiments, the corners 440 may have a radius
of about 10 millimeters. Further, in some embodiments, three of the
apertures 435 having a diameter between about 7.75 millimeters to
about 8.75 millimeters may be positioned in a triangular
configuration at the corners 440 to maximize the exposed surface
area for the adhesive 455. In other embodiments, the size and
number of the apertures 435 in the corners 440 may be adjusted as
necessary, depending on the chosen geometry of the corners 440, to
maximize the exposed surface area of the adhesive 455. Further, the
apertures 435 at the corners 440 may be fully contained within the
gel layer 415, substantially precluding fluid communication in a
lateral direction exterior to the corners 440. The apertures 435 at
the corners 440 being fully housed within the gel layer 415 may
substantially preclude fluid communication of the adhesive 455
exterior to the corners 440 and may provide improved handling of
the dressing 110 during deployment at a tissue site. Further, the
exterior of the corners 440 being substantially free of the
adhesive 455 may increase the flexibility of the corners 440 to
enhance comfort.
[0079] In some embodiments, the bond strength of the adhesive 455
may vary in different locations of the dressing 110. For example,
the adhesive 455 may have lower bond strength in locations adjacent
to the gel layer 415 where the apertures 435 are relatively larger
and may have higher bond strength where the apertures 435 are
smaller. Adhesive 455 with lower bond strength in combination with
larger apertures 435 may provide a bond comparable to adhesive 455
with higher bond strength in locations having smaller apertures
435.
[0080] The geometry and dimensions of the tissue interface 135, the
cover 140, or both may vary to suit a particular application or
anatomy. For example, the geometry or dimensions of the tissue
interface 135 and the cover 140 may be adapted to provide an
effective and reliable seal against challenging anatomical
surfaces, such as an elbow or heel, at and around a tissue site.
Additionally or alternatively, the dimensions may be modified to
increase the surface area for the gel layer 415 to enhance the
movement and proliferation of epithelial cells at a tissue site and
reduce the likelihood of granulation tissue in-growth.
[0081] Further, the dressing 110 may permit re-application or
re-positioning to reduce or eliminate leaks, which can be caused by
creases and other discontinuities in the dressing 110 and a tissue
site. The ability to rectify leaks may increase the reliability of
the therapy and reduce power consumption in some embodiments.
[0082] If not already configured, the dressing interface 470 may
disposed over the aperture 475 and attached to the cover 140. The
fluid conductor 465 may be fluidly coupled to the dressing
interface 470 and to the negative-pressure source 105.
[0083] In operation, the dressing 110 can provide a sealed
therapeutic environment proximate to a tissue site, substantially
isolated from the external environment, and the negative-pressure
source 105 can reduce pressure in the sealed therapeutic
environment.
[0084] The fluid mechanics of using a negative-pressure source to
reduce pressure in another component or location, such as within a
sealed therapeutic environment, can be mathematically complex.
However, the basic principles of fluid mechanics applicable to
negative-pressure therapy and instillation are generally well-known
to those skilled in the art, and the process of reducing pressure
may be described illustratively herein as "delivering,"
"distributing," or "generating" negative pressure, for example.
[0085] In general, exudate and other fluid flow toward lower
pressure along a fluid path. Thus, the term "downstream" typically
implies something in a fluid path relatively closer to a source of
negative pressure or further away from a source of positive
pressure. Conversely, the term "upstream" implies something
relatively further away from a source of negative pressure or
closer to a source of positive pressure. Similarly, it may be
convenient to describe certain features in terms of fluid "inlet"
or "outlet" in such a frame of reference. This orientation is
generally presumed for purposes of describing various features and
components herein. However, the fluid path may also be reversed in
some applications, such as by substituting a positive-pressure
source for a negative-pressure source, and this descriptive
convention should not be construed as a limiting convention.
[0086] Negative pressure applied across the tissue site through the
tissue interface 135 in the sealed therapeutic environment can
induce macro-strain and micro-strain in the tissue site. Negative
pressure can also remove exudate and other fluid from a tissue
site, which can be collected in container 115.
[0087] Negative pressure applied through the tissue interface 135
can create a negative pressure differential across the fluid
restrictions 420 in the polymer film 410, which can open or expand
the fluid restrictions 420 from their resting state. For example,
in some embodiments in which the fluid restrictions 420 may
comprise substantially closed fenestrations through the polymer
film 410, a pressure gradient across the fenestrations can strain
the adjacent material of the polymer film 410 and increase the
dimensions of the fenestrations to allow liquid movement through
them, similar to the operation of a duckbill valve. Opening the
fluid restrictions 420 can allow exudate and other liquid movement
through the fluid restrictions 420 into the manifold 405 and the
container 115. Changes in pressure can also cause the manifold 405
to expand and contract, and the interior border 450 may protect the
epidermis from irritation. The polymer film 410 and the gel layer
415 can also substantially reduce or prevent exposure of tissue to
the manifold 405, which can inhibit growth of tissue into the
manifold 405.
[0088] In some embodiments, the manifold 405 may be hydrophobic to
minimize retention or storage of liquid in the dressing 110. In
other embodiments, the manifold 405 may be hydrophilic. In an
example in which the manifold 405 may be hydrophilic, the manifold
405 may also wick fluid away from a tissue site, while continuing
to distribute negative pressure to the tissue site. The wicking
properties of the manifold 405 may draw fluid away from a tissue
site by capillary flow or other wicking mechanisms, for example. An
example of a hydrophilic material suitable for some embodiments of
the manifold 405 is a polyvinyl alcohol, open-cell foam such as
V.A.C. WHITEFOAM.TM. dressing available from KCI of San Antonio,
Tex. Other hydrophilic foams may include those made from polyether.
Other foams that may exhibit hydrophilic characteristics include
hydrophobic foams that have been treated or coated to provide
hydrophilicity.
[0089] If the negative-pressure source 105 is removed or
turned-off, the pressure differential across the fluid restrictions
420 can dissipate, allowing the fluid restrictions 420 to move to
their resting state and prevent or reduce the rate at which exudate
or other liquid from returning to the tissue site through the
polymer film 410.
[0090] In some applications, a filler may also be disposed between
a tissue site and the gel layer 415. For example, if the tissue
site is a surface wound, a wound filler may be applied interior to
the periwound, and the gel layer 415 may be disposed over the
periwound and the wound filler. In some embodiments, the filler may
be a manifold, such as open-cell foam. The filler may comprise or
consist essentially of the same material as the manifold 405 in
some embodiments.
[0091] Additionally or alternatively, instillation solution or
other fluid may be distributed to the dressing 110, which can
increase the pressure in the tissue interface 135. The increased
pressure in the tissue interface 135 can create a positive pressure
differential across the fluid restrictions 420 in the polymer film
410, which can open or expand the fluid restrictions 420 from their
resting state to allow the instillation solution or other fluid to
be distributed to a tissue site.
[0092] In some embodiments, the controller 120 may receive and
process data from one or more sensors, such as the first sensor
125. The controller 120 may also control the operation of one or
more components of the therapy system 100 to manage the pressure
delivered to the tissue interface 135. In some embodiments,
controller 120 may include an input for receiving a desired target
pressure and may be programmed for processing data relating to the
setting and inputting of the target pressure to be applied to the
tissue interface 135. In some example embodiments, the target
pressure may be a fixed pressure value set by an operator as the
target negative pressure desired for therapy at a tissue site and
then provided as input to the controller 120. The target pressure
may vary from tissue site to tissue site based on the type of
tissue forming a tissue site, the type of injury or wound (if any),
the medical condition of the patient, and the preference of the
attending physician. After selecting a desired target pressure, the
controller 120 can operate the negative-pressure source 105 in one
or more control modes based on the target pressure and may receive
feedback from one or more sensors to maintain the target pressure
at the tissue interface 135.
[0093] The systems, apparatuses, and methods described herein may
provide significant advantages over prior art. For example, some
dressings for negative-pressure therapy can require time and skill
to be properly sized and applied to achieve a good fit and seal. In
contrast, some embodiments of the dressing 110 can provide a
negative-pressure dressing that is simple to apply, reducing the
time to apply and remove. In some embodiments, for example, the
dressing 110 may be a fully-integrated negative-pressure therapy
dressing that can be applied to a tissue site (including on the
periwound) in one step, without being cut to size, while still
providing or improving many benefits of other negative-pressure
therapy dressings that require sizing. Such benefits may include
good manifolding, beneficial granulation, protection of the
peripheral tissue from maceration, and a low-trauma and high-seal
bond. These characteristics may be particularly advantageous for
surface wounds having moderate depth and medium-to-high levels of
exudate. The dressing 110 can also be manufactured with automated
processes with high throughput, which can lower part costs. Some
embodiments of the dressing 110 may remain on a tissue site for at
least 5 days, and some embodiments may remain for at least 7 days.
Antimicrobial agents in the dressing 110 may extend the usable life
of the dressing 110 by reducing or eliminating infection risks that
may be associated with extended use, particularly use with infected
or highly exuding wounds.
[0094] While shown in a few illustrative embodiments, a person
having ordinary skill in the art will recognize that the systems,
apparatuses, and methods described herein are susceptible to
various changes and modifications that fall within the scope of the
appended claims. Moreover, descriptions of various alternatives
using terms such as "or" do not require mutual exclusivity unless
clearly required by the context, and the indefinite articles "a" or
"an" do not limit the subject to a single instance unless clearly
required by the context. Components may be also be combined or
eliminated in various configurations for purposes of sale,
manufacture, assembly, or use. For example, in some configurations
the dressing 110, the container 115, or both may be eliminated or
separated from other components for manufacture or sale. In other
example configurations, the controller 120 may also be
manufactured, configured, assembled, or sold independently of other
components.
[0095] The appended claims set forth novel and inventive aspects of
the subject matter described above, but the claims may also
encompass additional subject matter not specifically recited in
detail. For example, certain features, elements, or aspects may be
omitted from the claims if not necessary to distinguish the novel
and inventive features from what is already known to a person
having ordinary skill in the art. Features, elements, and aspects
described in the context of some embodiments may also be omitted,
combined, or replaced by alternative features serving the same,
equivalent, or similar purpose without departing from the scope of
the invention defined by the appended claims.
* * * * *