U.S. patent application number 16/565071 was filed with the patent office on 2020-01-02 for multi-function dressing structure for negative-pressure therapy.
The applicant listed for this patent is KCI Licensing, Inc.. Invention is credited to Brian ANDREWS, Christopher Brian LOCKE, Timothy Mark ROBINSON, David George WHYTE.
Application Number | 20200000955 16/565071 |
Document ID | / |
Family ID | 54289140 |
Filed Date | 2020-01-02 |
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United States Patent
Application |
20200000955 |
Kind Code |
A1 |
ANDREWS; Brian ; et
al. |
January 2, 2020 |
MULTI-FUNCTION DRESSING STRUCTURE FOR NEGATIVE-PRESSURE THERAPY
Abstract
Systems, methods, and apparatuses for forming a multi-function
core for a dressing are described. The multi-function core includes
a contact layer configured to be positioned adjacent to a tissue
site, a wicking layer adjacent to the contact layer, an ion
exchange layer adjacent to the wicking layer, an absorbing layer
adjacent to the ion exchange layer, a blocking layer adjacent to
the absorbing layer, and an odor-absorbing layer adjacent to the
blocking layer. The contact layer, the wicking layer, the ion
exchange layer, the absorbing layer, the blocking layer, and the
odor-absorbing layer are coextensive and formed from a plurality of
fibers disposed in a fibrous web. Methods of manufacturing the
multi-function core are also described.
Inventors: |
ANDREWS; Brian; (Gothenburg,
SE) ; ROBINSON; Timothy Mark; (Shillingstone, GB)
; LOCKE; Christopher Brian; (Bournemouth, GB) ;
WHYTE; David George; (Wareham, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KCI Licensing, Inc. |
San Antonio |
TX |
US |
|
|
Family ID: |
54289140 |
Appl. No.: |
16/565071 |
Filed: |
September 9, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14869731 |
Sep 29, 2015 |
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16565071 |
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62096669 |
Dec 24, 2014 |
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62060098 |
Oct 6, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61L 15/44 20130101;
A61L 15/26 20130101; A61L 15/28 20130101; A61F 2013/00314 20130101;
A61L 15/24 20130101; A61F 13/00987 20130101; A61L 2420/00 20130101;
A61L 2300/106 20130101; A61M 1/0001 20130101; A61L 15/425 20130101;
A61L 15/225 20130101; A61L 15/60 20130101; A61L 15/22 20130101;
A61F 13/0276 20130101; A61L 2300/404 20130101; A61M 1/0088
20130101; A61F 13/00991 20130101; A61L 15/18 20130101; A61L
2300/104 20130101; G05B 19/41865 20130101; A61F 13/022 20130101;
A61F 13/00068 20130101 |
International
Class: |
A61L 15/18 20060101
A61L015/18; A61F 13/00 20060101 A61F013/00; A61M 1/00 20060101
A61M001/00; G05B 19/418 20060101 G05B019/418; A61L 15/26 20060101
A61L015/26; A61L 15/44 20060101 A61L015/44; A61L 15/60 20060101
A61L015/60; A61L 15/24 20060101 A61L015/24; A61L 15/28 20060101
A61L015/28; A61F 13/02 20060101 A61F013/02; A61L 15/22 20060101
A61L015/22; A61L 15/42 20060101 A61L015/42 |
Claims
1-70. (canceled)
71. A method for providing negative-pressure therapy to a tissue
site, the method comprising: positioning a tissue interface
adjacent to the tissue site; placing a sealing member over the
tissue interface and sealing the sealing member to tissue
surrounding the tissue site to form a sealed space; fluidly
coupling a negative-pressure source to the sealed space;
positioning a fluid management apparatus between the tissue
interface and the sealing member, the fluid management apparatus
comprising: a contact layer configured to be positioned adjacent to
the tissue interface; a fluid dispersion layer coupled to the
contact layer; an ion exchange layer coupled to the fluid
dispersion layer; a liquid retention layer coupled to the ion
exchange layer; a liquid blocking layer coupled to the liquid
retention layer; an odor removal layer coupled to the liquid
blocking layer; and operating the negative-pressure source to draw
fluid from the sealed space through the fluid management apparatus
and generate a negative pressure in the sealed space.
72. The method of claim 71, wherein the fluid dispersion layer, the
ion exchange layer, the liquid retention layer, the liquid blocking
layer, and the odor removal layer are coupled to each other so that
each layer is coextensive with adjacent layers.
73. The method of claim 71, wherein the fluid management apparatus
further comprises a rigid layer.
74. The method of claim 73, wherein the rigid layer is coupled
adjacent to the contact layer on a side of the contact layer that
is opposite the fluid dispersion layer.
75. The method of claim 73, wherein the rigid layer is coupled
adjacent to the odor removal layer.
76. The method of claim 71, wherein the contact layer, the fluid
dispersion layer, the ion exchange layer, the liquid retention
layer, the liquid blocking layer, and the odor removal layer are
formed from a plurality of fibers disposed in a fibrous web.
77. The method of claim 76, wherein the plurality of fibers of one
or more of the fluid dispersion layer, the ion exchange layer, the
liquid retention layer, the liquid blocking layer, and the odor
removal layer comprise single-layer fibers formed from a single
material.
78. The method of claim 76, wherein the plurality of fibers of one
or more of the fluid dispersion layer, the ion exchange layer, the
liquid retention layer, the liquid blocking layer, and the odor
removal layer comprise dual-layer fibers formed from two
materials.
79. The method of claim 76, wherein the plurality of fibers of one
or more of the fluid dispersion layer, the ion exchange layer, the
liquid retention layer, the liquid blocking layer, and the odor
removal layer comprise single-layer fibers formed from a single
material and dual-layer fibers formed from two materials.
80. The method of claim 78, wherein the dual-layer fibers comprise
an inner core formed from a first material and an outer sheathing
formed from a second material.
81. The method of claim 71, wherein the contact layer, the fluid
dispersion layer, the ion exchange layer, and the liquid retention
layer each comprise a plurality of dual-layer fibers, each
dual-layer fiber having an inner core formed from a first material
and an outer sheathing formed from a second material.
82. The method of claim 81, wherein the first material of the
dual-layer fibers of the contact layer comprises a hydrophobic
polyurethane and the second material of the dual-layer fibers of
the contact layer comprises a hydrophilic polyurethane.
83. The method of claim 82, wherein the hydrophilic polyurethane
comprises a silicone gel.
84. The method of claim 81, wherein the first material of the
dual-layer fibers of the contact layer comprises an
antimicrobial.
85. The method of claim 81, wherein the second material of the
dual-layer fibers of the contact layer comprises an
antimicrobial.
86. The method of claim 84, wherein the antimicrobial comprises at
least one selected from a group consisting of silver or iodine.
87. The method of claim 81, wherein the first material of the
dual-layer fibers of the fluid dispersion layer comprises a
hydrophobic polyurethane and the second material of the dual-layer
fibers of the fluid dispersion layer comprises a hydrophilic
polyurethane.
88. The method of claim 81, wherein the first material of the
dual-layer fibers of the ion exchange layer comprises a hydrophobic
polymer and the second material of the dual-layer fibers of the ion
exchange layer comprises a hydrophilic polymer having ion exchange
resins disposed therein.
89. The method of claim 81, wherein the first material of the
dual-layer fibers of the liquid retention layer comprises a
superabsorbent polymer and the second material of the dual-layer
fibers of the liquid retention layer comprises a hydrophilic
polymer.
90. The method of claim 89, wherein the superabsorbent polymer is
selected from a group consisting of: polyacrylates, polyacrylics,
and carboxymethyl cellulose.
91. The method of claim 71, wherein the fluid dispersion layer, the
ion exchange layer, the liquid retention layer, the liquid blocking
layer, and the odor removal layer each comprise a plurality of
single-layer fibers.
92. The method of claim 91, wherein the single-layer fibers of the
fluid dispersion layer are formed from a hydrophilic polymer.
93. The method of claim 92, wherein the hydrophilic polymer is
selected from a group consisting of polyurethane, polyester, or
acrylic.
94. The method of claim 91, wherein the single-layer fibers of the
ion exchange layer are formed from a hydrophilic polyurethane
having activated carbon particles disposed therein.
95. The method of claim 91, wherein the single-layer fibers of the
liquid retention layer are formed from an elastic polymer having
superabsorbent polymer disposed therein.
96. The method of claim 95, wherein the elastic polymer comprises
elastane.
97. The method of claim 95, wherein the superabsorbent polymer
comprises superabsorbent fibers.
98. The method of claim 95, wherein the superabsorbent polymer
comprises superabsorbent particles.
99. The method of claim 91, wherein the single-layer fibers of the
liquid blocking layer are formed from a hydrophobic polymer
disposed in an open non-woven fibrous web.
100. The method of claim 99, wherein the hydrophobic polymer
comprises a fluorocarbon.
101. The method of claim 91, wherein the single layer fibers of the
odor removal layer are formed from a gas permeable polymer having
activated carbon particles disposed in an open non-woven fibrous
web.
102. The method of claim 101, wherein the gas permeable polymer is
selected from a group consisting of polyurethane and silicone.
103. The method of claim 76, wherein the fibrous web comprises a
non-woven structure.
104. The method of claim 76, wherein the plurality fibers are
disposed in a woven structure.
105. The method of claim 71, wherein the fluid dispersion layer,
the ion exchange layer, the liquid retention layer, and the odor
removal layer are liquid permeable.
106-133. (canceled)
Description
[0001] This application is a divisional of U.S. patent application
Ser. No. 14/869,731, filed Sep. 29, 2015, which claims priority to
and the benefit of U.S. Provisional Patent Application No.
62/060,098, filed Oct. 6, 2014, entitled "Multi-Function Dressing
Structure for Negative Pressure Therapy," to Robinson et al., and
U.S. Provisional Patent Application No. 62/096,669, filed Dec. 24,
2014, entitled "Ion Exchange Absorbent Systems, Apparatuses, and
Methods, to Locke et al., which are hereby incorporated 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 a multi-function dressing structure 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," and "vacuum-assisted closure," 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] While the clinical benefits of negative-pressure therapy are
widely known, the cost and complexity of negative-pressure therapy
can be a limiting factor in its application, and the development
and operation of negative-pressure systems, components, and
processes continues to present significant challenges to
manufacturers, healthcare providers, and patients.
BRIEF SUMMARY
[0005] New and useful systems, apparatuses, and methods for a
multi-function core 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. For example, a multi-function core is
described herein. The multi-function core may include a contact
layer configured to be positioned adjacent to a tissue site, a
wicking layer adjacent to the contact layer, an ion exchange layer
adjacent to the wicking layer, an absorbing layer adjacent to the
ion exchange layer, a blocking layer adjacent to the absorbing
layer, and an odor-absorbing layer adjacent to the blocking layer.
The contact layer, the wicking layer, the ion exchange layer, the
absorbing layer, the blocking layer, and the odor-absorbing layer
may be formed from a plurality of fibers disposed in a fibrous
web.
[0006] In another example embodiment, a system for providing
negative-pressure therapy to a tissue site is described. The system
may include a manifold configured to be positioned adjacent to the
tissue site and a cover configured to be placed over the manifold
and sealed to tissue surrounding the tissue site to form a sealed
space. A negative-pressure source may be configured to be fluidly
coupled to the sealed space, and a multi-function core may be
configured to be positioned between the manifold and the cover. The
multi-function core may include a wound interface layer configured
to be positioned over the manifold, a fluid dispersion layer
positioned over the wound interface layer, an ion removal layer
positioned over the fluid dispersion layer, a liquid retention
layer positioned over the ion removal layer, a liquid obstruction
layer positioned over the liquid retention layer, and an odor
removal layer positioned over the liquid obstruction layer.
[0007] In still other embodiments, a method for providing
negative-pressure therapy to a tissue site is described. A tissue
interface may be positioned adjacent to the tissue site, and a
sealing member may be placed over the tissue interface and sealed
to tissue surrounding the tissue site to form a sealed space. A
negative-pressure source may be fluidly coupled to the sealed
space. A fluid management apparatus may be positioned between the
tissue interface and the sealing member. The fluid management
apparatus may include a contact layer configured to be positioned
adjacent to the tissue interface, a fluid dispersion layer coupled
to the contact layer, an ion exchange layer coupled to the fluid
dispersion layer, a liquid retention layer coupled to the ion
exchange layer, a liquid blocking layer coupled to the liquid
retention layer, and an odor removal layer coupled to the liquid
blocking layer. The negative-pressure source may be operated to
draw fluid from the sealed space through the fluid management
apparatus and generate a negative pressure in the sealed space.
[0008] In yet another embodiment, a method of manufacturing a
multi-function core for a negative-pressure dressing is described.
One or more plurality of fibers may be formed in respective
workstations of a plurality of workstations. The plurality of
fibers may be disposed into a fibrous web in the respective
workstations of the plurality of workstations. The layers may be
coupled to each other to form a multi-function sheet. The
multi-function sheet having the layers may be subdivided into
multi-function cores.
[0009] 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
[0010] FIG. 1 is sectional view of an example embodiment of a
negative-pressure therapy system that can provide negative-pressure
therapy in accordance with this specification;
[0011] FIG. 2 is a perspective view, with a portion shown in
cross-section, of an example embodiment of a fiber of the
multi-function core of FIG. 1;
[0012] FIG. 3 is a perspective view, with a portion shown in
cross-section, of an example embodiment of a dual-layer fiber of
the multi-function core of FIG. 1;
[0013] FIG. 4 is a perspective view illustrating additional details
of a woven layer of the multi-function core of FIG. 1;
[0014] FIG. 5 is a plan view illustrating additional details of a
non-woven layer of the multi-function core of FIG. 1;
[0015] FIG. 6 is a schematic sectional exploded view illustrating
additional details that may be associated with an example
embodiment of a multi-function core of the negative-pressure
therapy system of FIG. 1; and
[0016] FIG. 7 is a schematic representation of an example
embodiment of a manufacturing process for producing the
multi-function core of FIG. 6.
DESCRIPTION OF EXAMPLE EMBODIMENTS
[0017] 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.
[0018] 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.
[0019] FIG. 1 is a sectional view with a portion shown in elevation
of an example embodiment of a negative-pressure therapy system 100
that can provide negative-pressure therapy in accordance with this
specification. The negative-pressure therapy system 100 may include
a dressing 102 and a negative-pressure source 104. For example, a
dressing 102 may be fluidly coupled to a negative-pressure source
104, as illustrated in FIG. 1. In some embodiments, the
negative-pressure source 104 may be fluidly coupled to the dressing
102 by a tube 106 and a connector 107. A dressing generally
includes a cover and a tissue interface. The dressing 102, for
example, includes a cover 108, and a tissue interface 110. The
dressing 102 may also include a fluid management core, such as a
core 112.
[0020] In general, components of the negative-pressure therapy
system 100 may be coupled directly or indirectly. For example, the
negative-pressure source 104 may be directly coupled to the
connector 107 and indirectly coupled to the dressing 102 through
the connector 107. Components may be fluidly coupled to each other
to provide a path for transferring fluids (i.e., liquid and/or gas)
between the components.
[0021] In some embodiments, for example, components may be fluidly
coupled through a tube. A "tube," as used herein, broadly refers to
a tube, pipe, hose, conduit, or other structure with one or more
lumina 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. In some embodiments,
components may additionally or alternatively be coupled by virtue
of physical proximity, being integral to a single structure, or
being formed from the same piece of material. Coupling may also
include mechanical, thermal, electrical, or chemical coupling (such
as a chemical bond) in some contexts.
[0022] In operation, the tissue interface 110 may be placed within,
over, on, or otherwise proximate to a tissue site. The cover 108
may be placed over the tissue interface 110 and sealed to tissue
near the tissue site. For example, the cover 108 may be sealed to
undamaged epidermis peripheral to a tissue site. Thus, the dressing
102 can provide a sealed therapeutic environment proximate to a
tissue site, substantially isolated from the external environment,
and the negative-pressure source 104 can reduce the pressure in the
sealed therapeutic environment. Negative pressure applied across
the tissue site through the tissue interface 110 in the sealed
therapeutic environment can induce macrostrain and microstrain in
the tissue site, as well as remove exudates and other fluids from
the tissue site, which can be collected in the dressing core 112
and disposed of properly.
[0023] 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 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.
[0024] In general, exudates and other fluids flow toward lower
pressure along a fluid path. Thus, the term "downstream" typically
implies a position in a fluid path relatively closer to a
negative-pressure source, and conversely, the term "upstream"
implies a position relatively further away from a negative-pressure
source. 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 of negative-pressure
therapy systems 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.
[0025] The term "tissue site" in this context broadly refers to a
wound or defect located on or within tissue, including but not
limited to, 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. 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 used in certain tissue areas to grow
additional tissue that may be harvested and transplanted to another
tissue location.
[0026] "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 provided
by the dressing 102. 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.
Similarly, 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.
[0027] A negative-pressure source, such as the negative-pressure
source 104, may be a reservoir of air at a negative pressure, or
may be a manual or electrically-powered device that can reduce the
pressure in a sealed volume, such as a vacuum pump, a suction pump,
a wall suction port available at many healthcare facilities, or a
micro-pump, for example. A negative-pressure source 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 negative-pressure therapy. 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 -75 mm Hg (-9.9 kPa) and -300 mm Hg (-39.9 kPa).
[0028] The tissue interface 110 can be generally adapted to contact
a tissue site. The tissue interface 110 may be partially or fully
in contact with the tissue site. If the tissue site is a wound, for
example, the tissue interface 110 may partially or completely fill
the wound, or may be placed over the wound. The tissue interface
110 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 110
may be adapted to the contours of deep and irregular shaped tissue
sites.
[0029] In some embodiments, the tissue interface 110 may be 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 negative
pressure. For example, a manifold may be adapted to receive
negative pressure from a source and distribute the 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 across a tissue site.
[0030] In some illustrative embodiments, the pathways of a manifold
may be channels interconnected to improve distribution or
collection of fluids across a tissue site. For example, cellular
foam, open-cell foam, reticulated 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 pathways. Liquids, gels, and other foams may also include or
be cured to include apertures and flow channels. In some
illustrative embodiments, a manifold may be a porous foam material
having interconnected cells or pores adapted to uniformly (or
quasi-uniformly) distribute negative pressure to a tissue site. The
foam material may be either hydrophobic or hydrophilic. In one
non-limiting example, a manifold may be an open-cell, reticulated
polyurethane foam such as GranuFoam.RTM. dressing available from
Kinetic Concepts, Inc. of San Antonio, Tex.
[0031] In an example in which the tissue interface 110 may be made
from a hydrophilic material, the tissue interface 110 may also wick
fluid away from a tissue site, while continuing to distribute
negative pressure to the tissue site. The wicking properties of the
tissue interface 110 may draw fluid away from a tissue site by
capillary flow or other wicking mechanisms. An example of a
hydrophilic foam is a polyvinyl alcohol, open-cell foam such as
V.A.C. WhiteFoam.RTM. dressing available from Kinetic Concepts,
Inc. 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.
[0032] The tissue interface 110 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 110 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
110.
[0033] In some embodiments, the tissue interface 110 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 110 may
further serve as a scaffold for new cell-growth, or a scaffold
material may be used in conjunction with the tissue interface 110
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.
[0034] In some embodiments, a sealing member, such as the cover
108, may provide a bacterial barrier and protection from physical
trauma. The cover 108 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 108 may be,
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. In some example embodiments, the
cover 108 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.
[0035] An attachment device may be used to attach the cover 108 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 that extends about a periphery, a
portion, or an entire sealing member. In some embodiments, for
example, some or all of the cover 108 may be coated with an acrylic
adhesive having a coating weight between 25-65 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.
[0036] Tissue sites may produce fluids that can be removed by
negative pressure. Fluids removed from a tissue site can be
collected for subsequent disposal or analysis. For example, a
canister may be fluidly coupled to a dressing to collect fluids
from a wound. Such canisters are readily available and can be
relatively inexpensive. However, canisters can also be cumbersome
and limit patient mobility. Some dressings can absorb fluids, which
can enhance patient mobility, but manufacturing a dressing with
adequate fluid capacity can be complex and expensive.
[0037] A fluid management core such as the core 112 can reduce the
cost and complexity of manufacturing a dressing with fluid storage
capacity. For example, in some embodiments, a multi-function core
may include six or more layers that provide skin contact, fluid
wicking, ion exchange, liquid absorbing, liquid blocking, and odor
absorbing functions in a unitary apparatus. A dressing may be
manufactured by a process that produces each layer as a part and
assembles the multi-function core in a process that reduces
manufacturing time and costs.
[0038] As shown in FIG. 1, the core 112 may be a multi-function
core or fluid management apparatus having multiple layers that can
be configured to accomplish different functions. In some
embodiments, the core 112 may include six layers. For example, the
core 112 may have a wound interface layer or contact layer 114, a
fluid dispersion layer or wicking layer 116, an ion removal layer
or ion exchange layer 118, a liquid retention layer or absorbing
layer 120, a liquid obstruction layer or blocking layer 122, and an
odor removal layer or odor absorbing layer 124. Each layer may be
formed from a plurality of fibers disposed in a fibrous web. In
some embodiments, a fibrous web may include a plurality of fibers
positioned so that individual fibers overlap and are coupled to one
another to form open spaces between adjacent fibers. The fibrous
web may be a woven or non-woven. In some embodiments, the plurality
of fibers may be single-layer fibers. In some embodiments, the
plurality of fibers may be dual-layer fibers. In some embodiments,
the fibers of a particular layer may be both single-layer and
dual-layer fibers. The core 112 may have a high moisture vapor
transfer rate (MVTR) and gas permeability across the structure such
that dry negative pressure, that is, air having little or no
moisture content, may be manifolded across the entire area of the
core 112. In some embodiments, the core 112 may have an MVTR
between about 250 g/m.sup.2/day and about 2000 g/m.sup.2/day when
measured at 37.degree. C. and 50% relative humidity using the
upright cup method. In some embodiments, the core 112 may have a
gas permeability of oxygen of about 50
cm.sup.3/m.sup.2/day/MPa.
[0039] FIG. 2 is a partial sectional view of a single-layer fiber
200, illustrating additional details that may be associated with
some example embodiments. The single-layer fiber 200 may have a
diameter in the range of about 1 micron to about 50 microns. The
single-layer fiber 200 may be a fiber having a substantially
homogenous composition. For example, the single-layer fiber 200 may
be formed from a single material, such as polyurethane, polyester,
acrylic, fluorocarbon, or silicone. In some embodiments, the
single-layer fiber 200 may be associated with additional materials,
such as activated carbon particles or superabsorbent polymer
particles or fibers. For example, the single-layer fiber 200 may be
formed from silicone and have activated carbon particles disposed
within or on the silicone. The single-layer fiber 200 may be formed
by melt-blown fiber formation, melt-spinning fiber formation,
wet-spinning fiber formation, or solution-based electro
spinning.
[0040] Melt blown fiber formation may involve extruding melted
polymers through a spin net or die to produce fibers. Hot air may
be blown over the fibers to stretch and cool the fibers as the
fibers pass out of the spin net or die. Melt spinning may involve
melting a polymer and squeezing the melted polymer through a
spinneret to form a fiber. For example, silicone may be mixed with
glycerol and deionized water to form a solution. The solution may
be fed into an extruder spinning system to form fibers. Wet
spinning may involve dissolving the polymer to form a coagulating
bath having a low pH. Liquid in the coagulating bath may be
evaporated to form a fine fiber. For example, silicone can be
processed by a cylinder spinning system to spin a thread that may
be coagulated in a bath, air dried, and wound on a bobbin.
Electrospinning may subject a polymer solution to an electric field
to induce the accumulation of a charge on the surface of a pendant
drop. The charge accumulation generates a force that directly
opposes the force produced by the surface tension of the drop that,
above a critical value of electric field strength, can cause a
charged jet to eject to form fine filaments. The filaments may then
be cut into standardized lengths to form staple fibers. In some
embodiments, the staple fibers may have a length between about 4 mm
and about 6 mm. The staple fibers may be twisted together and
carded to form the single-layer fiber 200.
[0041] FIG. 3 is a partial sectional view of a dual-layer fiber
300, illustrating additional details that may be associated with
some example embodiments. The dual-layer fiber 300 may have an
inner core 302 and an outer sheathing 304. In some embodiments, the
inner core 302 may be a fiber having a substantially homogenous
composition. For example, the inner core 302 may be formed from a
single material, such as polyurethane, polyester, acrylic,
fluorocarbon, or silicone. In some embodiments, the inner core 302
may be associated with additional materials, such as activated
carbon particles or antimicrobials. For example, the inner core 302
may be formed from silicone and have activated carbon particles
disposed within or on the silicone. The inner core 302 may be
formed by melt-blown fiber formation, melt-spinning fiber
formation, wet-spinning fiber formation, or solution-based electro
spinning. In some embodiments, the inner core 302 may have a
diameter in the range of about 0.75 microns to about 75 microns.
The outer sheathing 304 may be a coating of a material that is
different than the material of the inner core 302. In some
embodiments, the outer sheathing 304 may be formed from a silicone
gel or hydrophilic polyurethane. In some embodiments, the outer
sheathing 304 may have a thickness between about 0 microns and
about 12.5 microns. In some embodiments, the dual-layer fiber 300
may have an overall diameter between about 0.75 microns and about
100 microns.
[0042] FIG. 4 is a perspective view of a portion of a layer that
may be associated with some embodiments of the core 112. For
example, the layer may be the wicking layer 116 having a woven
structure as illustrated in FIG. 4. A woven generally refers to a
fabric-like material formed by weaving, knitting, lace-making,
felting, braiding, or plaiting fibers so that the fibers are
interlaced. Although the wicking layer 116 is illustrated in FIG.
4, any or all of the contact layer 114, the ion exchange layer 118,
and the absorbing layer 120 may also be formed as a woven analogous
to the wicking layer 116. In some embodiments, the fibers of a
woven layer may be single-layer fibers 200. In some embodiments,
the fibers of a woven layer may be dual-layer fibers 300. In some
embodiments, for example, the wicking layer 116 may be formed by
weaving the single-layer fibers 200 to form a regular pattern of
openings or mesh apertures 230. As illustrated in FIG. 4, the
wicking layer 116 may comprise a first plurality of single-layer
fibers 200 aligned substantially parallel to each other and a
second plurality of single-layer fibers 201 also aligned
substantially parallel to each other, wherein the fibers 200 are
disposed adjacent to the fibers 201 at an angle. In some
embodiments, the fibers 200 may be perpendicular to the fibers 201.
The fibers 200 and the fibers 201 may overlap each other to form a
weave or mesh having the plurality of apertures 230. The fibers 200
may intersect with the fibers 201 to form a plurality of
intersections 236. An intersection 236 may be formed by overlapping
fibers. In some embodiments, the fibers 200 and the fibers 201 may
be woven together to form a network or a mesh.
[0043] The first fibers 200 and the second fibers may be separated
from adjacent fibers 200 and fibers 201, respectively, by a
distance 232 and 234, respectively, which may be between about 0.5
mm and about 5 mm. In other embodiments, the distance 232 and 234
may be between about 1.0 mm and about 2.5 mm. In some embodiments,
the distance 232 and the distance 234 may be the substantially
equal. In other embodiments, the distance 232 and the distance 234
may be different.
[0044] In some embodiments, the mesh apertures 230 may have an
average effective diameter of about 2 mm. An effective diameter of
a non-circular area may be a diameter of a circular area having the
same surface area as the non-circular area. For example, the
surface area of a mesh aperture 230 where the distance 232 is 0.5
mm and the distance 234 is 0.5 mm may be 0.25 mm.sup.2. The
diameter of a circular area having a 0.25 mm.sup.2 surface area is
about 0.56 mm; consequently, the effective diameter of the
exemplary mesh aperture 230 is about 0.56 mm. Similarly, if the
distance 232 is about 4 mm and the distance 234 is about 4 mm, the
effective diameter of the mesh aperture 230 may be about 4.51 mm.
In some embodiments, each mesh aperture 230 may have an area formed
by the effective diameter of the mesh aperture 230. In some
embodiments, each mesh aperture 230 may be uniform in area. In
other embodiments, each mesh aperture 230 may not be uniform in
area. If the mesh apertures 230 are not uniform in area, the
average of the areas of the mesh apertures 230 may be between about
0.2 mm.sup.2 and about 20 mm.sup.2. Each of the contact layer 114,
the wicking layer 116, the ion exchange layer 118, the absorbing
layer 120, the blocking layer 122, and the odor absorbing layer 124
may have mesh apertures 230 between about 0.2 mm.sup.2 and about 20
mm.sup.2.
[0045] In some embodiments, each of the single-layer fibers 200,
201 of the wicking layer 116 may have a diameter 228. In other
embodiments, the diameters of the single-layer fibers 200, 201 may
be different. The intersections 236 may have a prominence 241. In
some embodiments, the prominence 241 at the intersections 236 may
be equal to the diameter 228 of the single-layer fibers 200, 201.
In some embodiments, the prominence 241 may be reduced by
compressing the wicking layer 116 following formation of the
wicking layer 116. The prominences 241 may also be reduced by
passing the wicking layer 116 through a calender, which may apply
pressure to the wicking layer 116 to smooth out the wicking layer
116. Each of the contact layer 114, the wicking layer 116, the ion
exchange layer 118, the absorbing layer 120, the blocking layer
122, and the odor absorbing layer 124 may have prominences 241. The
wicking layer 116 may have a thickness 224. In some embodiments,
the thickness 224 may be the combined thickness of the diameters
228 of the single-layer fibers 200, 201.
[0046] FIG. 5 is a schematic view of a portion of a non-woven
layer, such as the wicking layer 116, illustrating additional
details that may be associated with other example embodiments of
the negative-pressure therapy system 100. A non-woven may be a
layer of fabric-like material made from long fibers that may be
bonded together by chemical, mechanical, heat, or solvent
treatment. Non-wovens may be melt blown, air laid, thermo bonded,
and spun bonded, for example. Each of the contact layer 114, the
ion exchange layer 118, the absorbing layer 120, the blocking layer
122, and the odor-absorbing layer 124 may be formed as a non-woven
as described with respect to the wicking layer 116 herein. The
non-woven wicking layer 116 may operate similarly or analogously to
the woven wicking layer 116. Similar elements may have similar
reference numbers that are indexed to 300. In some embodiments, a
plurality of dual-layer fibers 300 may be formed into the non-woven
wicking layer 116. For example, the dual-layer fibers 300 may be
dispersed on a conveyor belt, and spread in a uniform web by a
wetlaid, an airlaid, or a carding/crosslapping process. The
dual-layer fibers 300 may be bonded thermally or by using a resin
to form the mesh of the wicking layer 116. For example, the
dual-layer fibers 300 may overlap and form intersections 336 where
the dual-layer fibers 300 overlap with other dual-layer fibers 300.
The overlapping dual-layer fibers 300 of the wicking layer 116 may
also form openings, such as mesh apertures 330. As shown in FIG. 5,
the mesh apertures 330 may not be uniform in shape. The mesh
apertures 330 of the wicking layer 116 may have an average
effective diameter between about 1 mm and about 5 mm. If the mesh
apertures 330 are not uniform in size the average of the effective
diameters of each of the mesh apertures 330 may be between about 1
mm and about 5 mm.
[0047] In some embodiments, the wicking layer 116 may also be
formed in a spunlaid process. Spunlaid non-wovens may be made in a
continuous process. The dual-layer fibers 300 may be dispersed into
a web by physical deflectors or with air streams as the dual-layer
fibers 300 are produced without further cutting the dual-layer
fibers 300.
[0048] Generally, a thickness of the non-woven wicking layer 116,
the dual-layer fibers 300, a diameter of the dual-layer fibers 300,
the mesh apertures 330, and the intersections 336 may be similar to
and operate as described above with respect to the woven wicking
layer 116, the thickness 224 of the wicking layer 116, the
single-layer fibers 200, 201, the diameter 228, the mesh apertures
230, and the intersections 236, respectively.
[0049] FIG. 6 is a schematic sectional exploded view illustrating
additional details that may be associated with an example
embodiment of the multi-function core 112. In some embodiments, the
contact layer 114, the wicking layer 116, the ion exchange layer
118, the absorbent layer 120, the blocking layer 122, the
odor-absorbing layer 124, and the rigid layer 126 may be
coextensive with one another. In other embodiments, one or more of
the contact layer 114, the wicking layer 116, the ion exchange
layer 118, the absorbent layer 120, the blocking layer 122, the
odor-absorbing layer 124, and the rigid layer 126 may be
coextensive with one another. In still other embodiments, the
contact layer 114, the wicking layer 116, the ion exchange layer
118, the absorbent layer 120, the blocking layer 122, the
odor-absorbing layer 124, and the rigid layer 126 may not be
coextensive with one another. In some embodiments, one or more of
the contact layer 114, the wicking layer 116, the ion exchange
layer 118, the absorbent layer 120, the blocking layer 122, the
odor-absorbing layer 124, and the rigid layer 126 may draw
negative-pressure through the respective layer. In some
embodiments, one or more of the contact layer 114, the wicking
layer 116, the ion exchange layer 118, the absorbent layer 120, the
odor-absorbing layer 124, and the rigid layer 126 may be liquid
permeable.
[0050] The contact layer 114 may be formed from a plurality of
dual-layer fibers 300 formed into a woven or non-woven layer of
material. In some embodiments, the contact layer 114 may have a
thickness between about 0.5 millimeters (mm) and about 2 mm. In
some embodiments, the dual-layer fibers 300 may have the inner core
302 formed from a hydrophobic polyurethane and the outer sheathing
304 formed from a silicone gel. In other embodiments, the inner
core 302 may be a hydrophobic polyurethane core and the outer
sheathing 304 may be a hydrophilic polyurethane. In some
embodiments the hydrophilic polyurethane of the outer sheathing 304
may be a gel. In some embodiments, an antimicrobial, such as
silver, may be dispersed in the outer sheathing 304 of the
dual-layer fibers 300 of the contact layer 114. In some
embodiments, an antimicrobial, such as iodine, may be dispersed in
the inner core 302 of the dual-layer fibers 300 of the contact
layer 114. In some embodiments, if the antimicrobial is disposed in
the inner core 302 rather than the outer core 304, the
antimicrobial may have a time-release property. In still other
embodiments, the outer sheathing 304 may be formed from collagen.
In some embodiments, the contact layer 114 may seal to epidermis
surrounding a tissue site. In some embodiments, the contact layer
114 may be tacky to assist in forming a seal. For example, the
contact layer 114 may have a tackiness or peel adhesion of about
0.2 N/cm on stainless steel substrate at 23.degree. C. at 50%
relative humidity based on the American Society for Testing and
Materials ("ASTM") standard ASTM D3330. In some embodiments, the
dual-layer fibers 300 may have a tensile strength of about 40
Newtons (N) per 5 cm length in the direction of the applied force
with a tolerance of about +/- 15%, and the contact layer 114 may
permit fluid flow at about 0.83 cubic centimeters/hour.
[0051] In some embodiments, the wicking layer 116 may be formed
from a plurality of single-layer fibers 200 formed into a woven or
a non-woven. In some embodiments, the wicking layer 116 may have a
thickness between about 1 mm and about 4 mm. In some embodiments,
the single-layer fibers 200 may be formed from a hydrophilic
polymer such as polyurethane, polyester, or acrylic. In other
embodiments, the wicking layer 116 may be formed from dual-layer
fibers 300. If the wicking layer 116 is formed from dual-layer
fibers 300, the inner core 302 may be formed from hydrophobic
polyurethane, and the outer sheathing 304 may be formed from
hydrophilic polyurethane. The hydrophobic polyurethane of the inner
core 302 may provide more strength than the single-layer fiber 200
formed from the hydrophilic polyurethane alone. Generally,
polyurethane may have a strength inversely proportional to its
volumetric water content. By using a hydrophobic polyurethane to
form the inner core 302, the inner core 302 of the dual-layer fiber
300 of the wicking layer 116 may resist water absorption, thereby
increasing the strength of the dual-layer fiber 300. For example,
the wicking layer 116 formed as a non-woven having the dual-layer
fibers 300 may have a tensile strength of about 40 Newtons (N) per
5 cm length in the direction of the applied force with a tolerance
of about +/- 15%. In some embodiments, the wicking layer 116 may
encourage fluid to spread at an angle to the direction of fluid
flow. For example, if a negative-pressure source is drawing fluid
through the wicking layer 116 parallel to the thickness of the
wicking layer 116, the wicking layer 116 may encourage fluid to
spread perpendicular to the thickness of the wicking layer 116. In
some embodiments, the wicking layer 116 may permit fluid flow at
about 0.83 cubic centimeters/hour or greater.
[0052] In some embodiments, the ion exchange layer 118 may be
formed from a plurality of dual-layer fibers 300. In some
embodiments, the ion exchange layer 118 may have a thickness in the
range of 0.5 mm and about 2 mm, a flow rate of about 0.83 cubic
centimeters/hour, and the dual-layer fibers 300 may have a tensile
strength of about 40 Newtons (N) per 5 cm length in the direction
of the applied force with a tolerance of about +/- 15%.
[0053] The dual-layer fibers 300 of the ion exchange layer 118 may
have an inner core 302 formed from a hydrophobic polymer, such as a
hydrophobic polyurethane and an outer sheathing 304 formed from a
hydrophilic polymer, such as a hydrophilic polyurethane. Ion
exchange media (IEM) may be disposed in the outer sheathing 304.
Generally, IEM may exchange both hydrogen and hydroxyl ions for
cationic and anionic salt ions found in wound fluids, such as
sodium, chloride, and calcium. In other embodiments, the ion
exchange layer 118 may be formed from a single-layer fiber 200
formed from a hydrophilic polymer having activated carbon particles
or fibers for ion exchange functionality.
[0054] IEM may be adapted to provide an exchange of ions between
two electrolytes, or between an electrolyte solution and a complex.
An electrolyte may be a compound that ionizes when dissolved in a
suitable ionizing solvent, such as water. An electrolyte solution
may contain a dissolved salt, such as NaCl. A complex may be an
atom or ion having a surrounding array of bound molecules or anions
known as ligands or complexing agents. IEM replaces cations and
anions in an electrolyte or an electrolyte solution as the
electrolyte or electrolyte solution interacts with the IEM. Cations
are ions having a net positive charge, for example, Na+. Cations
may be replaced in the electrolyte or electrolyte solution with
hydrogen (H+) ions of the IEM. Anions are ions having a net
negative charge, for example, Cl-. Anions may be replaced in the
electrolyte or electrolyte solution with hydroxyl (OH-) ions of the
IEM. The H+ and OH- ions may combine in the electrolyte or
electrolyte solution to form water. The IEM is typically in the
form of porous beads that are formed from crosslinked polymers,
such as polystyrene, that are doped or grafted with acidic
polymers. An example of an acidic polymer may include
poly(2-acrylamido-2-methyl-1-propanesulfonic acid) or polyAMPS. The
polyAMPS exchange positively charged salt ions for H+. Another
example of an acidic polymer may include
poly(acrylamido-N-propyltrimethylammonium chloride) or polyAPTAC.
The polyAPTAC exchange negatively charged salt ions for OH-.
[0055] The IEM may include a mixture of cation absorbing media and
anion absorbing media to form a mixed bed media that simultaneously
absorbs both anions and cations. Non-limiting examples of the mixed
bed media include Amberlite.TM. IRN150 and TMD-8. The IEM may be
formed from ion exchange resins, zeolites, montmorillonite,
bentonites, clay, or soil humus, for example. Ion exchange resins,
also known as ion exchange polymers, are insoluble matrices
normally in the form of small beads fabricated from an organic
polymer substrate. Ion exchange resins may have pores on the
surface that trap and release ions. Ion exchange resins can include
crosslinked polystyrene, for example. Zeolites are microporous,
aluminosilicate minerals. Zeolites have a porous structure that
allow cations, such as Na.sup.+, K.sup.+, Ca.sup.2+, and Mg.sup.2+,
for example, to be accommodated by the zeolite. Common zeolites
include analcime, chabazite, clinoptilolite, heulandite, natrolite,
phillipsite, and stilbite, for example. In addition to the above
materials, other ion exchange media include activated charcoal,
both particulate and in the form of fabrics or non-wovens, for
example, and Zorflex.RTM., also known as Chemviron Carbon.
Chemviron Carbon may also be known as 100% activated carbon. In an
experimental embodiment, a fluid having 0.154 moles/liter of NaCl
was passed through the ion exchange layer 118. In the experimental
embodiment, the ion exchange layer 118 removed Na+ and CL- ions at
a rate of about 0.0026 moles per hour. In some embodiments, the ion
exchange layer 118 may have a similar or greater ion removal
rate.
[0056] In some embodiments, the absorbing layer 120 may be formed
from a plurality of dual-layer fibers 300. The dual-layer fibers
300 of the absorbing layer 120 may have the inner core 302 formed
from a superabsorbent polymer, such as polyacrylates, polyacrylics,
or carboxymethyl cellulose. The outer sheathing 304 may be
hydrophilic. In some embodiments, the absorbing layer 120 may be
formed from single-layer fibers 200 having an elastic polymer such
as an elastane polyurethane with superabsorbent particles disposed
therein. In some embodiments, fibers of the absorbing layer 120 may
be either woven or non-woven. In some embodiments, the absorbing
layer 120 may have a thickness in the range of about 1 mm to about
4 mm. In some embodiments, the single layer fibers 200 and the
dual-layer fibers 300 may have a tensile strength of about 40
Newtons (N) per 5 cm length in the direction of the applied force
with a tolerance of about +/- 15%. In some embodiments, the
absorbing layer 120 may permit a flow rate of about 0.83 cubic
centimeters/hour.
[0057] In some embodiments, the superabsorbent or superabsorbent
particles may be formed from a superabsorbent polymer (SAP).
Generally, relative to their mass, SAPs can absorb and retain large
quantities of liquid, and in particular water. For example, some
SAPs may be able to absorb about 500 times its own weight in water,
or about 30 to 60 times its own volume in water. The ability of an
SAP to absorb water may be based in part on the ionic concentration
of the fluid being absorbed. SAPs may be of the type often referred
to as "hydrogels," "super-absorbents," or "hydrocolloids." SAPs may
be formed into fibers or spheres. Spaces or voids between the
fibers or spheres may allow a reduced pressure to be transferred
within and through the absorbing layer 120.
[0058] SAPs may be formed in several ways, for example, by gel
polymerization, solution polymerization, or suspension
polymerization. Gel polymerization may involve blending of acrylic
acid, water, cross-linking agents, and ultraviolet (UV) initiator
chemicals. The blended mixture may be placed into a reactor where
the mixture is exposed to UV light to cause crosslinking reactions
that form an SAP. The mixture may be dried and shredded before
subsequent packaging and/or distribution. Solution polymerization
may involve a water-based monomer solution that produces a mass of
reactant polymerized gel. The monomer solution may undergo an
exothermic reaction that drives the crosslinking of the monomers.
Following the crosslinking process, the reactant polymer gel may be
chopped, dried, and ground to its final granule size. Suspension
polymerization may involve a water-based reactant suspended in a
hydrocarbon-based solvent. However, the suspension polymerization
process must be tightly controlled and is not often used.
[0059] SAPs absorb liquids by bonding with water molecules through
hydrogen bonding. Hydrogen bonding involves the interaction of a
polar hydrogen atom with an electronegative atom. As a result, SAPs
absorb water based on the ability of the hydrogen atoms in each
water molecule to bond with the hydrophilic polymers of the SAP
having electronegative ionic components. High-absorbing SAPs are
formed from ionic crosslinked hydrophilic polymers such as acrylics
and acrylamides in the form of salts or free acids. In some
embodiments, the absorbing layer 120 may use ionic based SAPs
formed from ester salts such as sodium and potassium of acrylic,
acrylate, and methacrylate copolymers. In some embodiments, the
absorbing layer 120 may retain liquid at a rate greater than about
0.83 cubic centimeters/hour.
[0060] In some embodiments, the blocking layer 122 may be formed
from a plurality of single-layer fibers 200 formed from a highly
hydrophobic polymer such as polyurethane or fluorocarbon.
Hydrophobicity may be measured by a surface energy of the material,
where a lower surface energy corresponds to a higher
hydrophobicity. In some embodiments, the hydrophobic polymer of the
single-layer fibers 200 of the blocking layer 122 may be about 25
milliNewtons/meter or less. Generally, the blocking layer 122 may
prevent liquid flow through the blocking layer 122 by creating a
pressure barrier for liquid movement. For example, the hydrophobic
material of the blocking layer 122 may prevent liquid passage where
the pressure drawing liquid into and through the blocking layer 122
is less than a water breakthrough pressure of the blocking layer
122. Generally, the water breakthrough pressure of a material
increases as the hydrophobicity of the material increases. In some
embodiments, the blocking layer 122 may have a water breakthrough
pressure greater than about 125 mm Hg negative pressure.
[0061] The blocking layer 122 may have a non-woven structure to
provide for the manifolding of air and negative pressure over the
entire area of the structure. Generally, a non-woven structure may
have a porosity or density that permits an air flow for a given
pressure; similar to a woven structure. In some embodiments, a
non-woven may also be referred to as an open non-woven. In some
embodiments, the porosity may be measured by the amount of free
volume of the non-woven, that is how much of the structure is not
occupied by fibers. For example, the blocking layer 122 may have a
free volume of about 85% to about 98%. In some embodiments, the
blocking layer 122 may permit about 0.2 to about 1.0
liters/m.sup.2/minute/Pa of air flow through the blocking layer
122. In some embodiments, the blocking layer 122 may have a
thickness in the range of 0.2 mm and about 0.5 mm, and the
single-layer fibers 200 may have a tensile strength of about 40
Newtons (N) per 5 cm length in the direction of the applied force
with a tolerance of about +/- 15%.
[0062] In some embodiments, the odor-absorbing layer 124 may be
formed from a plurality of single-layer fibers 200 formed from a
highly gas permeable polymer such as a polyurethane or a silicone
that contains a dispersion of activated carbon particles. The
odor-absorbing layer 124 may also have a non-woven structure to
provide for the manifolding of air and negative pressure over the
entire area of the structure. In some embodiments, the
odor-absorbing layer 124 may have a free volume of about 85% to
about 98%. In some embodiments, the odor-absorbing layer 124 may
permit about 0.2 to about 1.0 liters/m.sup.2/minute/Pa of air flow.
In some embodiments, the odor absorbing layer 124 may have a
thickness in the range of about 0.2 mm and about 1 mm. In some
embodiments, the single-layer fibers 200 may have a tensile
strength of about 40 Newtons (N) per 5 cm length in the direction
of the applied force with a tolerance of about +/- 15%.
[0063] In some embodiments, the core 112 may also have a rigid
layer 126. The rigid layer 126 may be a plurality of single-layer
fibers 200 formed from polyurethane or a high hardness polymer.
Generally a high hardness polymer has a hardness rating greater
than or equal to about 70 Shore A. In some embodiments, the high
hardness polymer may have a hardness rating between about 75 Shore
A and about 85 Shore A. In some embodiments, the rigid layer 126
may have a thickness in the range of about 1 mm to about 4 mm. The
rigid layer 126 may be disposed adjacent to the contact layer 114
or the odor absorbing layer 124. In some embodiments, the rigid
layer 126 may resist rucking, folding, or wrinkling of the core
112. In some embodiments, the rigid layer 126 may increase rigidity
between about 25% and about 40% over the core 112 without the rigid
layer 126. In some embodiments, the single-layer fibers 200 may
have a tensile strength of about 40 Newtons (N) per 5 cm length in
the direction of the applied force with a tolerance of about +/-
15%.
[0064] In some embodiments, the contact layer 114 may form a base
of the core 112, and the wicking layer 116 may be stacked adjacent
to the contact layer 114. The ion exchange layer 118 may be stacked
adjacent to the wicking layer 116, and the absorbing layer 120 may
be stacked adjacent to the ion exchange layer 118. The blocking
layer 122 may be stacked adjacent to the absorbing layer 120, and
the odor-absorbing layer 124 may be placed adjacent to the blocking
layer 122 to cap the core 112. As each layer is stacked on the
previous layer, the layers may be coupled to each other. For
example, the wicking layer 116 may be coupled to the contact layer
114 by adhering, welding, or stitching. Each subsequent layer may
be coupled in a similar manner to form the core 112. Generally,
each layer will extend the full length and width of the core 112 so
that a surface area of each layer is substantially the same.
[0065] Referring to FIG. 1, the core 112 may be positioned adjacent
to the manifold 110, and the cover 108 may be placed over the core
112 and the manifold 110 to form a sealed therapeutic environment
or a sealed space. The negative-pressure source 104 may be fluidly
coupled to the sealed space and operated to draw fluid from the
tissue site. In some embodiments, the contact layer 114 may be in
contact with the manifold 110. In other embodiments, the contact
layer 114 may be in direct contact with the tissue site or skin
adjacent to the tissue site. The contact layer 114 may function to
decrease irritation of the skin in contact with the core 112.
[0066] As fluid is drawn from the tissue site by the
negative-pressure source 104, fluid may be drawn through the
contact layer 114 and into the wicking layer 116. The wicking layer
116 may function to aid in the distribution of fluid across the
core 112. In particular, if a portion of the core 112 is blocked,
for example by fluid stored in the absorbing layer 120, the wicking
layer 116 may provide a pathway for fluid to move around the
blockage and further into the core 112. For example, the
hydrophilic properties of the single-layer fibers 200 of the
wicking layer 116, or the hydrophilic properties of the outer
sheathing 304 of the dual-layer fibers 300 of the wicking layer 116
encourage fluid movement through the wicking layer 116.
[0067] Fluid may be drawn from the wicking layer 116 into the ion
exchange layer 118. As fluid moves through the ion exchange layer
118, salts in the fluids may be removed, decreasing the ionic
concentration of the fluids. Fluids may be drawn from the ion
exchange layer 118 into the absorbing layer 120, where the fluids
may be stored in the superabsorbent polymers of the absorbing layer
120. The combination of the ion exchange layer 118 and the
absorbing layer 120 may increase the storage capacity of the core
112 over a core without the ion exchange layer 118.
[0068] The blocking layer 122 may operate to prevent any liquids
not trapped by the absorbing layer 120 from moving beyond the
blocking layer 122 and out of the core 112, thereby limiting the
risk of damage to the negative-pressure source 104. For example,
the hydrophobic properties of the single-layer fibers 200 of the
blocking layer 122 discourage liquid from moving into and through
the blocking layer 122. Finally, fluids, mostly gas, may be drawn
through the odor absorbing layer 124, where foul odors that may be
traveling with the fluids can be absorbed.
[0069] FIG. 7 is a schematic diagram, illustrating a manufacturing
system 500 for the core 112 that may be associated with some
embodiments. The manufacturing system 500 may include a plurality
of work stations. In some embodiments, the manufacturing system 500
may have six work stations: a first work station 502, a second work
station 504, a third work station 506, a fourth work station 508, a
fifth work station 510, and a sixth work station 512. Each work
station may be configured to form a separate layer of the core 112.
For example, the first work station 502 may be configured to form
the contact layer 114, the second work station 504 may be
configured to form the wicking layer 116, the third work station
506 may be configured to form the ion exchange layer 118, the
fourth work station 508 may be configured to form the absorbing
layer 120, the fifth work station 510 may be configured to form the
blocking layer 122, and the sixth work station 512 may be
configured to form the odor absorbing layer 124.
[0070] In some embodiments, each work station 502-512 may form the
fibers of the particular layer manufactured by that work station.
In some embodiments each work station 502-512 may weave or position
the fibers to form the material of the particular layer
manufactured by that work station. In some embodiments, each work
station 502-512 may both form the fibers of the particular layer
and then engage in a process to form the fibers into a particular
layer. The layers may then be fed from the work stations 502-512 to
an assembly station 514. The assembly station 514 may stack the
layers and couple the layers to each other to form a multi-function
sheet. Once formed by the assembly station 514, the multi-function
sheet may be subdivided into smaller portions, such as individual
cores 112, for use with the negative-pressure therapy system 100.
For example, in some embodiments, the multi-function sheet may be
cut into cores 112 of varying sizes for varying tissue site
sizes.
[0071] In some embodiments, more or fewer work stations may be used
with the manufacturing system 500 to create alternative cores
having more or fewer functions. For example, if the core 112
includes the rigid layer 126, the manufacturing system 500 may
include a seventh work station 516 configured to manufacture the
rigid layer 126. Similarly, if the core 112 does not include the
odor absorbing layer 124 or the ion exchange layer 118, the third
work station 506 or the sixth work station 512 may be turned off or
removed from the manufacturing system 500 entirely.
[0072] The systems, apparatuses, and methods described herein may
provide significant advantages. For example, the core 112
simplifies dressing assembly as all of the characteristics of a
wicking and absorbing core can be provided ready for placement at a
tissue site by a clinician or user. A user may only be required to
locate the core 112 at the tissue site and attach a cover over the
core 112. The core 112 may also resist rucking and the formation of
ridges that can result in blisters under the dressing during use.
Furthermore, the core 112 is highly configurable during
manufacturing, allowing the addition or subtraction of layers and
materials to accomplish different functions. For example,
antimicrobial agents may be added to the contact layer 114 to aid
fighting infection. Similarly, collagen may be added to the contact
layer 114 to aid in regulation of matrix metalloproteinase.
[0073] 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. 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.
[0074] 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 herein may also be 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.
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