U.S. patent number 3,709,221 [Application Number 04/878,716] was granted by the patent office on 1973-01-09 for microporous nonadherent surgical dressing.
This patent grant is currently assigned to Pall Corporation. Invention is credited to Phyllis Riely.
United States Patent |
3,709,221 |
Riely |
January 9, 1973 |
MICROPOROUS NONADHERENT SURGICAL DRESSING
Abstract
A composite surgical dressing that is highly absorbent, capable
of preventing leakage or exudation from open wounds and capable of
preventing contamination from entering or escaping from the wound,
comprising an outer microporous, liquid-repellent fibrous layer
having a maximum pore size of 0.5 micron, and a voids volume of at
least 50 percent; an inner macroporous, fibrous layer, the
body-contacting face of which is non-wetted by body fluids; and a
highly absorbent intermediate layer between the outer and inner
layers.
Inventors: |
Riely; Phyllis (Massapequa,
NY) |
Assignee: |
Pall Corporation (Glen Cove,
NY)
|
Family
ID: |
25372664 |
Appl.
No.: |
04/878,716 |
Filed: |
November 21, 1969 |
Current U.S.
Class: |
602/43;
604/385.01 |
Current CPC
Class: |
A61L
15/18 (20130101); A61L 15/425 (20130101); A61L
15/50 (20130101) |
Current International
Class: |
A61L
15/50 (20060101); A61L 15/18 (20060101); A61L
15/42 (20060101); A61L 15/16 (20060101); A61l
015/00 () |
Field of
Search: |
;128/156,155,296 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Pioneering Uses of Fiberglas Materials in Medicine, Owens-Corning
Fiberglas Corp. (3/21/45)..
|
Primary Examiner: Michell; Robert W.
Claims
Having regard to the foregoing disclosure, the following is claimed
as the inventive and patentable embodiments thereof:
1. A composite surgical dressing having a high degree of absorbency
for body fluids exuded from a wound area, capable of preventing
microbiological contamination of the wound area from without, and
nonadherent to the wound during healing, comprising an outer
microporous liquid-repellent fibrous layer having an effective
maximum pore size not in excess of 0.5 micron, inhibiting passage
of body fluids and passage of microorganisms in either direction
therethrough, and having a voids volume of at least 50 percent, an
inner macroporous fibrous layer, the body-contacting face of which
is permeable to but not wetted by body fluids and impregnated so as
to coat the fibers thereof with a nonadherent physiologically inert
liquid-repellent polymer thereby rendering the body-contacting face
nonadherent to the wound, and bonding the fibers of the face
together, and a highly absorbent intermediate layer between the
outer and inner layers capable of absorbing body fluids passing
through the inner macroporous layer.
2. The dressing of claim 1 wherein the outer and the inner layers
are bonded together so as to compress the absorbent layer between
them.
3. The dressing of claim 2 wherein the outer and inner layers are
bonded together by an adhesive tape applied around the edges of the
dressing and folded over each of the outer and inner layers.
4. The dressing of claim 1, including an adhesive applied to the
outside surface of the inner layer of the dressing, around the
periphery thereof, to bond the dressing to a patient.
5. The dressing of claim 1 comprising in addition a
biologically-active ingredient applied to one of the layers of the
dressing.
6. A composite surgical dressing having a high degree of absorbency
for body fluids exuded from a wound area, capable of preventing
microbiological contamination of the wound area from without, and
nonadherent to the wound during healing, comprising an outer
microporous liquid-repellent glass fiber fabric fibrous layer
having an effective maximum pore size not in excess of 0.5 micron,
inhibiting passage of body fluids and passage of microorganisms in
either direction therethrough, and having a voids volume of at
least 50 percent, an inner macroporous fibrous layer, the
body-contacting face of which is not wetted by body fluids and
impregnated so as to coat the fibers thereof with a nonadherent
physiologically inert liquid-repellent polymer thereby rendering
the body-contacting face nonadherent to the wound, and bonding the
fibers of the face together, and a highly absorbent intermediate
layer between the outer and inner layers capable of absorbing body
fluids passing through the inner macroporous layer.
7. The dressing of claim 6 wherein the glass fiber fabric has glass
fibers embedded in the weave thereof.
8. The dressing of claim 6 wherein the glass fiber fabric is coated
with a resinous material imparting liquid repellency to the
fabric.
9. The dressing of claim 6 wherein the inner fibrous layer is a
coarsely woven glass fiber fabric coated with a fluorocarbon resin
imparting liquid repellency to the fabric and improving its
resistance to adhesion to the body, while permitting the passage of
fluids and air through the fabric.
10. The dressing of claim 6 wherein the outer layer is microporous
glass fiber fabric impregnated with glass fibers and a fluorocarbon
resin imparting liquid repellency to the fabric, the intermediate
layer is a layer of absorbent cellulose fibers, and the inner layer
is a macroporous glass fiber fabric having the body-contacting face
impregnated with a fluorocarbon resin imparting liquid repellency
to the fabric and improving its resistance to adhesion to the body,
while permitting the passage of fluids and air through the
fabric.
11. The dressing of claim 1 wherein the microporous layer has an
effective maximum pore diameter of less than 0.2 micron.
Description
Dressings are applied to large area wounds, whether massive
abrasions or burns or deep open wounds, in order to protect the
wound surface, absorb fluids exuded from the wound and to let air
into the surface of the wound. It is important to prevent the
contamination of the wound without impeding the progress of the
natural healing process of the body, and in some cases, to protect
the environment against contamination from the wound.
It is also important to avoid, or at least impede, the formation of
an adherent bond between the wound surface and the bandage; such a
bond can be formed when the body fluids exuded from the wound into
the dressing dry to a crust and the dry crust adheres to the
healing flesh and to the dressing. This makes very difficult the
removal of the bandage without causing great pain to the patient
and, even more important, without reopening a partially healed
wound.
A further problem is absorbing the body fluids which tend to exude
from an open wound or massive burn area, so as to remove the fluids
from the surface of the wound, permitting it to dry; this furthers
the healing process; it is also necessary at the same time to
control the loss of fluid. It is most advantageous, especially when
dealing with massive burns, to insure against shock by preventing
the excessive loss of the salts from the body which generally are
dissolved an any body fluids which may be exuded. Therefore, by
limiting the loss of body fluids, the loss of salts is also
impeded, thereby decreasing the chances of severe shock.
Previous attempts have been made to prepare bandages which are
impermeable to the passage of liquids, but selectively permeable to
specific gases and vapors. In U.S. Pat. No. 3,367,329, patented
Feb. 6, 1968, to Dibelius, there is described a surgical bandage
including a nonporous membrane, impermeable to liquids and
infectious organisms but selectively permeable to specific gases
and vapors. In other words, the material is a membranous material
that permits the diffusion of vapors, which diffusion is "due to
the partial pressure differential and is not related to the
conventional filtering process" (column 2, lines 67 and 68). Such a
material is insufficiently permeable compared to the usual porous
bandage material, and thus fails to provide the necessary
transpiration from the wound surface. Further, there is no
provision for absorption of any body fluids exuded from a wound or
burn area. The Dibelius membrane is indicated as being a thin,
permeable silicone rubber membrane having the desired
permeability.
U.S. Pat. No. 3,426,754, patented Feb. 11, 1969, to Bierenbaum et
al. describes a medical dressing comprising a film having a
pressure-sensitive adhesive applied thereto. The film is described
as a porous material having an open celled structure permeable to
gases. The void or pore sizes of the open cell structure accessible
to the exterior of the film is described as being "under 5,000
angstrom units, e.g., 100 to 500 angstrom units." The film of
Bierenbaum et al. is prepared from a group of relatively
crystalline film-forming polymers having a defined elasticity.
These films are prepared by a special process which forms the open
cell structure in the film. The film can be formed from various
hydrocarbon polymers, acetal polymers or a miscellaneous group of
polymers including polyalkylene sulfides, polyphenylene oxides,
polyamides and polyesters. Films of this type are also relatively
inefficient and fail to provide the necessary amounts of air and
moisture vapor to and from the wound surface; they have a low dirt
capacity, so that the amount of air which can be passed in quickly
decreases once the film is exposed to even a slightly dusty
environment. Bierenbaum et al. further disclose the use of the
porous film in combination with a pad or facing, covered by a
wrapping or cover which functions to hold the facing in
position.
It is an object of the present invention to provide a surgical
dressing which provides all of the usual attributes of a surgical
dressing, including the ability to absorb the body fluids exuded
from the wound, to protect the wound surface, and to permit the
transpiration of air and moisture between the atmosphere and the
wound surface. It is a further object of the present invention to
provide a surgical dressing which, in addition to all of the usual
attributes of a surgical dressing, also prevents the passage of
microorganisms to or from the wound surface while retaining the
ability to permit full transpiration of air and moisture during
use.
It is a further object to provide a surgical dressing which is
highly absorbent and capable of retaining, after absorbing, the
body fluids exuded from the wound, so as to prevent the passage of
the exuded liquid outside of the bandage.
In accordance with the present invention, a composite surgical
dressing is provided comprising an outer microporous, liquid
repellent fibrous layer, an intermediate absorbent layer, and an
inner macroporous layer for separating the absorbent layer from a
wound. The body-contacting face of the inner layer is not wetted by
body fluid and thus has the property of being relatively
non-adherent to a wound surface.
The dressing according to this invention is especially useful for
large open wounds or massive burn areas, where there is heavy
exudation of body fluids from the wound which must be absorbed, and
the loss of which must be controlled and limited, together with a
need for maintaining the wound or burn area aseptic and free from
dirt, dust or other contaminants or irritants. It is further useful
to prevent the influx of liquids from the exterior while permitting
the free passage of air to the wound surface. The surgical dressing
has a large capacity to absorb exuded body liquids without
permitting loss of such liquids through the upper layer of the
dressing, thus controlling the loss of fluids and the salts
dissolved therein from the body.
The three layers of the composite surgical dressing of this
invention can be held together by mechanical means or by a bonding
agent. Optimally, the layers are bonded together around their
periphery, or at the outer edges of the composite. This avoids
obstructing or decreasing the absorbency of the central layer of
the dressing at the central portion which will be over the wound
area. Holding or bonding the layers together around their periphery
so that the edges of the dressing are sealed also serves to prevent
any loss or escape of the central absorbent layer from between the
inner and outer layers; this is especially important where the
absorbent layer is formed of a fluffy fibrous mass in which the
individual fibers are not bonded together. Further, imperviously
sealing the edges prevents the entry of bacteria or other
contaminants into the absorbent layer; this prevents the
circumvention of the protective upper, microporous,
liquid-repellent layer by these contaminants.
The surgical dressing preferably also comprises an adherent layer,
which serves to bond the dressing pad to the flesh of the user; the
adherent layer preferably bonds the dressing pad to the flesh of
the patient, around the periphery of the wound, to complete the
seal around the periphery of the dressing; this further inhibits
the by-passing of the microporous outer layer by organisms or
particles that could contaminate the wound surface.
The outer microporous fibrous sheet of the dressing of the present
invention must be liquid-repellent, to prevent the passage
primarily of water or aqueous fluids therethrough. This serves to
prevent the loss of body exudations as well as to prevent the
ingress of water from the outside. Thus, the fabric serves as a
two-way valve: to control the loss of fluid and to prevent the
entry of septic liquids onto the wound. Further, pores which would
be small enough to prevent the passage of air-borne bacteria may
not be small enough to prevent the passage of bacteria carried by a
liquid, especially water. Thus, if the outer layer were not liquid
repellent, as moisture condenses or is deposited upon the exterior
of the outer layer, bacteria could be carried by the water through
the pores of the outer fabric into the absorbent layer and then to
the open wound or burn surface. It is a well-known fact that
filters can retain air-borne particles of a smaller size than
liquid-borne particles. A large liquid-borne particle can be pushed
through the filter pores by the flowing liquid that could not be
pushed through by dry air. Accordingly, the pores need be no
smaller than the largest dimension of a microorganism or
particle.
The microporous fibrous outer layer of the dressing of the present
invention provides an open passage for the atmosphere to the space
within the dressing, and especially that immediately above the
wound. The outer microporous layer is sufficiently porous to permit
the passage of air at a substantially zero pressure differential
across the surface. The outer layer does not pass the air by a
diffusion process, as in the case of a membrane, but rather by
direct gas flow through open pores. The outer layer must have a
fluid flow capacity sufficient to maintain transpiration over the
wound area. The open structure of the microporous fibrous layer is
obtained by utilizing a filter material having a voids volume of at
least 50 percent and preferably at least 75 percent.
The outer fibrous layer preferably has a pore size which excludes
the passage of air-borne particles of greater than 0.5 micron
diameter and optimally of greater than 0.2 micron diameter. This is
referred to in the claims as "effective maximum pore diameter".
This is sufficiently small to prevent the passage of substantially
all harmful air-borne bacteria or other microorganisms such as
molds, fungi and spores. The liquid-repellent properties of the
outer fibrous layer prevent the passage of liquid and thus a
smaller pore size is unnecessary.
The outer microporous fibrous layer of the present invention must
also be capable of withstanding the abrasion to which it may be
subjected during use. For example, if worn by an ambulatory
patient, who then proceeds to carry out his normal daily activities
wearing the surgical dressing, the outer layer can be subjected to
severe abrasive stress. The outer layer must have sufficient wear
resistance to maintain its usefulness over a period of time when
worn by an active patient.
Accordingly, preferred types of microporous liquid-repellent
fibrous layers are prepared from a woven glass cloth, which gives
the fabric great abrasion resistance and flexibility; the glass
cloth preferably has deposited within the weave glass fibers which
are bonded in place with a fluorocarbon polymer, including a
chlorofluorocarbon polymer, impregnant or a silicone impregnant.
The impregnants are preferably inert and nontoxic to the patient.
These impregnants are liquid-repellent and thus prevent the passage
of aqueous liquids through the microporous fabric. The glass fabric
has great strength and ability to withstand the stresses to which
it would be subjected during a day's wearing by an ambulatory
patient. An example of such a material is described in U.S. Pat.
No. 3,053,762, patented Sept. 11, 1962 to Adiletta.
Examples of suitable fluorocarbon and chlorofluorocarbon polymer
impregnants include polytetrafluoroethylene, fluorinated
ethylenepropylene polymer, polyhexafluoropropylene and
polychlorotrifluoroethylene. Polytetrafluoroethylene is the
preferred impregnant.
The silicone impregnants can be silicone resins or silicone
rubbers. The dimethylsiloxane polymers are preferred because of
their physiological inertness.
The use of a woven glass fiber fabric and deposited glass fibers is
especially preferred, when utilizing a fluorocarbon polymer
impregnant. The fluorocarbon polymers require a relatively high
curing temperature, after impregnating the fabric to cure the
polymer and to bond the fibers in place; glass is especially suited
to withstand such high temperatures. Other impregnating fibers and
woven fiber fabrics, however, can be used including such synthetic
fibers, and fabrics made therefrom, such as polyamides, polyesters,
rayons and polyacrylic resins and even such natural fibers as wool
and cotton. The silicone impregnants are especially useful when the
fabric and the impregnating fibers are not formed of glass because
the silicone impregnants do not require a high curing
temperature.
Nonwoven fabrics can also be utilized for the upper layer of the
dressing of this invention if they are strong enough and have
sufficient abrasion resistance. Excellent microporous woven and
nonwoven fibrous sheet materials can be prepared according to any
of the following U.S. Pat. Nos. 3,238,056 to Pall et al., dated
Mar. 1, 1966; No. 3,246,767 to Pall et al., dated Apr. 19, 1966;
and No. 3,353,682 to Pall et al., dated Nov. 21, 1967, and these
are quite useful in this invention.
The intermediate absorbent layer can be formed of any of a great
number of the soft, highly absorbent fibrous materials commonly
used in, for example, bandages or tampons. The absorbent layer can
be formed of wrapped layers of gauze. However, such wrapped fabrics
would provide only the minimal absorbency required. Preferred
materials include folded crepe tissue of cotton fibers or of wood
pulp fibers, cotton wadding, certain synthetic fibers such as
acetate rayon or regenerated cellulose, pulp fluff fibers (obtained
by disintegrating chemical cellulose pulp prepared by the sulfate
or sulfite methods in such a way that the fibers are set free from
the pulp while at the same time avoiding the formation of fiber
bundles or knots and cutting of the fibers), absorbent cotton
fluff, such as cotton linters, garnetted white cotton waste, and
fibrous layers formed from ramie, jute, hemp and bagasse
fibers.
The absorbent portion can be formed of mats or pads of fibers, such
as a mixture of cotton linters and crimped viscose rayon staple
fibers, e.g. in the proportions of about 60 percent cotton linters
and 40 percent viscose rayon staple fibers by weight. The fibers
can have a denier within the range of from about 3 to about 15.
Cotton linters comprise cotton fibers of short length usually
within the range of one thirty-second to about three-sixteenths of
an inch. The viscose rayon fibers are preferably crimped or
crinkled and generally of longer lengths, for example from about
one-fourth to about three-fourths inch. The viscose fibers tend to
add additional resiliency, if needed, to the absorbent layer to
further protect the wound area. In addition, if the absorbent
material is to be compressed, which results in a greater
absorptivity per volume of absorbent material, the rayon fiber
component permits additional resilience or springiness in the
absorbent pad.
Generally, any highly absorbent, usually cellulosic fibrous
material of a bulky character can be used as the absorbent layer in
the dressing of the present invention. Although noncellulosic
materials can be used, they are not as preferred because the
fibers, per se, are generally nonabsorbent, or if they are
absorbent tend to be far more expensive than the cellulosic
materials.
Certain sponge materials, such as an artificial regenerated
cellulosic sponge as conventionally produced and commercially
available, have suitable properties of texture, porosity,
resilience and absorptivity suitable for use as an absorbent layer
in the dressing of the present invention. Composite fiber-surfaced
sponges, such as are described in U.S. Pat. No. 3,156,242, patented
Sept. 3, 1968, to Crowe, Jr. et al., having hydrophilic fibers
extending from the surface of the sponge into the main body
thereof, are especially useful for forming the absorbent layer of
the dressing of the present invention. Generally, any hydrophilic
material is useful for the absorbent layer, including any
combination of the above fibrous and/or spongy materials.
The inner layer of the dressing of the present invention, which is
intended to contact the wound area, is of a macroporous fibrous
sheet material, preferably woven to obtain increased strength and
greatest porosity, and nonadherent to the wound. The porosity must
be great enough to allow body fluids to pass through the pores with
insufficient pressure drop, despite the non-wetted characteristic,
and small enough to prevent fibers of the absorbent layer from
extending through to contact the wound. It is important that the
inner face of the inner layer, which is intended to rest against
the wound area, be nonadherent to the wound surface. Otherwise,
fibers might be left behind on the wound, causing possible future
complications, and the dressing might tend to pull open a partially
healed wound, when being pulled off. To avoid this problem, the
fibers on the body-contacting face of the inner layer, i.e. the
face intended to rest against the wound, are formed of, or coated
or impregnated with, a material which is not wetted by body fluids,
so that when the body fluids dry, they do not form an adherent bond
to that face of the layer.
The macroporous, non-wetted, physiologically inert inner layer is
preferably formed of a loosely woven glass fiber scrim. Other
fibrous material can be used, including the various fabrics listed
above for the microporous outer layer. The inner fabric is
preferably impregnated, at least on the body-contacting face, with
a nonadherent, physiologically inert, liquid-repellent polymer such
as the fluorocarbon, including the chlorofluorocarbon, polymers or
silicone polymers discussed above as the impregnant for the
microporous outer layer. All of the body-contacting face of the
inner layer must be non-wetted by body fluids, to insure that it is
nonadherent, and macroporous. Hence, any impregnation should cover
the fibers forming the outer face of the fabric, i.e. the face
touching the wound area, but should not block the pores between the
fibers. Generally, polytetrafluoroethylene is the preferred
impregnating agent for the nonadherent lower layer, because of its
inertness, and its ability to form a thin film on the fibers of the
fabric, without blocking the pores.
Alternatively, the fibers forming the coarse fabric can be coated
with the liquid-repellent preliminary to formation of the fabric,
whether by weaving, knitting or laying down to form a nonwoven web
or mat, to insure that all of the fibers are completely coated.
This, however, may render more difficult the fabric forming
process, as the coated fibers may not be as easily handled because
they become too thick.
The use of a polytetrafluoroethylene impregnation on the inner
macroporous layer, as with the upper layer, tends to favor the
utilization of a glass fabric, or other inorganic high
temperature-resistant material. A preferred material for forming
the lower layer is a coarsely woven glass fiber fabric which is
coated with Teflon and then cured at the high temperatures required
for Teflon curing.
Making the inner fabric layer non-wetted by body liquid and
non-adherent to the open wound enables the bandage to be removed
without reopening a large oozing wound. The liquid being exuded
from the wound surface flows through the macroporous inner layer,
to be absorbed by the intermediate layer. The inner layer is not
wetted by the liquid exuded from a wound, and separates the
absorbed liquid in the absorbent layer from the wound surface. The
liquid absorbed by the absorbent layer is thus separated from the
wound area by the non-wetted inner fabric layer, so that when the
absorbed liquid dries, it does not form a continuous scab with the
healing wound; further, the non-wetted fabric is open to and
permits the ready passage of air to the wound surface, to speed the
healing of the wound.
The composite dressing pad can be held together by, for example, an
adhesive tape, folded around the edges of the pad and bonded to the
peripheries of both the upper and lower fabric surfaces.
Preferably, the tape is microporous, as is the upper fabric, or
non-porous to air so as to prevent the passage of
microorganisms.
Alternatively, the upper and lower layers can be bonded together by
applying a bonding agent to the layers and pressing them together,
and curing the bonding agent, if necessary. Preferably, the
microporous layer extends out beyond the absorbent layer and is
folded around and under the inner macroporous layer. This latter
system is desirable, because it protects the absorbent layer from
being contaminated and thus prevents contaminants from being
absorbed by the absorbent layer and passing through the macroporous
layer to the wound surface.
The dressing pad can be attached onto a patient in various ways. An
adhesive layer can be applied to the dressing pad. The adhesive can
be applied around the outer periphery of the lower fabric layer; it
can be applied to the lower side of the tape that is folded around
the edges of the dressing pad, if that is the method used to hold
the composite together; or, it can be applied to a portion of the
upper microporous layer if the upper layer extends out beyond the
main body of the pad or if the upper microporous layer is folded
around and under the lower macroporous layer. Alternatively, the
composite dressing can be applied to a patient and held in place by
a bandage, generally a coarsely woven fabric, or by tape, wrapped
about the patient.
Referring to the drawings,
FIG. 1 is a perspective view of a dressing pad prepared according
to the present invention with portions of the upper microporous
layer and of the middle absorbent layer broken away.
FIG. 2 is a sectional side view of the dressing pad of FIG. 1.
In the drawings, the upper microporous fabric 1 is a woven glass
cloth having glass fibers deposited in the weave and impregnated
with Teflon. The fabric is prepared according to the procedure set
out in the Example in U.S. Pat. No. 3,053,762, utilizing a
polytetrafluoroethylene impregnant. The microporous layer 1 has a
maximum effective pore size of 0.2 microns, as determined by 100
percent removal of the bacteria Pseudomonas Diminutia in air
suspension.
The middle absorbent layer 4 is formed of compressed wood cellulose
fluff deposited as a layer upon the upper microporous fabric and
held in place between the lower macroporous woven glass scrim 3 and
the upper fabric. The scrim 3 is formed of a woven glass fabric
impregnated with polytetrafluoroethylene to insure body liquid
repellency. In forming the dressing, the glass scrim is placed over
the layer of fluff deposited upon the microporous layer 1 and the
composite is compressed to decrease volume and thus increase
unit-volume absorptivity. Finally, the microporous adhesive tape 2
is attached around the periphery of the dressing and folded over to
bind the structure together and to maintain the middle fluff layer
in compression. Folding the tape 2 completely around the periphery
of the pad insures against loss of the middle fluff layer 4.
However, folding the tape around only two of the four sides could
be sufficient.
Alternatively, the middle layer can be formed of folded sheets of
cotton wadding or wood pulp crepe tissue or several layers of a
nonwoven fibrous material interleaved between supporting sheets of
woven fabrics such as gauze; this type of an absorbent layer can be
precompressed and then held between the microporous and macroporous
outer layers; the composite can be then held together as explained
above.
Alternatively, as a substitute for the microporous tape 2, which is
applied around the sides and folded over both the upper and lower
layer as shown in the drawing, the upper and lower macroporous and
microporous fabrics can be bonded together with a bonding agent
applied around the edges of the fabrics and cured subsequent to
placing the absorbent layer between the two outer layers.
To further prevent contamination of the wound area and to prevent
escape of wound exudation, means should be provided for sealing the
periphery of the inner layer of the dressing to the flesh of the
patient. Such sealing means can include an adherent area around the
periphery of the dressing, such as is shown in the drawing in FIG.
1, where the tape 2 folded around the inner and outer layers can
have a portion of its undersurface, 5, i.e. adjacent the outer face
of the inner layer 3, adhesive on two sides, such that when it is
pressed against the patient the outer edges will adhere to the
patient forming an air-tight, or preferably a microporous,
water-resistant bond. Preferably the adhesive material is permeable
or porous to air but nonpermeable to microorganisms. The permeable
or porous adhesive is formed so as to autogenously develop a vast
number of pores producing a microporous, adhesive film that remains
visibly continuous, but provides a microporous adhesive web
suitable to prevent the contamination of the area under the
dressing when the dressing is applied and bonded to a patient. Such
a microporous adhesive is capable of admitting air, even to the
area directly under the adhesive, thereby preventing any maceration
of the wound border area, but prevents the passage of bacteria.
Such maceration of the skin often occurs when a nonporous layer is
applied over the skin, preventing the skin from transpiring
properly. Such maceration is evidenced by a wrinkling and paleness
of the flesh. An especially useful embodiment of such adhesive is
shown in U.S. Pat. No. 3,426,754, to Bierenbaum et al., see
particularly, the portion beginning on column 7, line 57 through
column 8, line 60.
As a further preferred embodiment of the invention, a germicide can
be applied either to the absorbent layer or to the outer
microporous layer of the dressing. Such a germicide would insure
that any microbes which do penetrate the outer layer will be
inactivated or killed. The germicide should, of course, be nontoxic
and non-irritating to the patient. However, if the germicide is
applied to the outer microporous layer or the the upper portion of
the absorbent layer immediately adjacent the outer layer, and it
cannot migrate through the absorbent layer and macroporous inner
layer, to contact the patient, the nonirritating nature of the
germicide becomes less significant.
Antiseptic or medicating agents or other biologically active agents
can be introduced into the dressing, especially into the
macroporous layer or the absorbent layer, by incorporating a liquid
or dry medicating agent and applying it to the desired layer. Such
materials can be coated on the inner layer so as to react with the
fluids exuded from the wound and thus be applied to aid in healing
and disinfecting the wound surface. The germicide is preferably
applied to the outer layer subsequent to curing, especially if the
impregnant in the outer microporous layer is a tetrafluoroethylene
polymer. Such materials require a high curing temperature which
would decompose most organic germicides. Further, a disinfectant or
biocide which is intended to act on the wound surface by reacting
with the body fluids to either disinfect the wound area or to aid
in the healing process can be applied to the inner macroporous
layer, also subsequent to application and curing of the
liquid-repellent coating to impart the non-wetted
characteristic.
The fibrous layers and the composite dressing should be flexible,
so as to be able to conform to the body's surface. Where desirable,
such as where the dressing is to be placed over an area which is
subject to constant flexing, as at a joint in the body, e.g. an
elbow or a knee, so that the dressing would require an added degree
of flexibility, the fibrous layers can be formed only in part of
the microporous or macroporous fabric, having intermediate portions
formed of an impermeable, but elastic, material. In this
construction, the microporous or macroporous fabric material can be
formed in alternating strips along the length of the dressing,
extending in a direction perpendicular to the direction in which
the dressing is to be flexed, with the portions intermediate the
microporous or macroporous material formed of the elastic material.
This increases the elasticity of the dressing subjected to extreme
flexing by the bodily member, while limiting the stress on the
microporous or macroporous material, thereby decreasing the chances
of ripping the microporous or macroporous layers, or of expanding
or warping the pore openings of the layers, and thereby exposing
the wound to exterior contaminants.
The intermediate absorbent layer, if it is highly porous to the
flow of air, can aid to ensure that the air passing through the
permeable portions of the outer layer is distributed over the
entire surface of the wound, through the microporous outer layer
and the macroporous inner layer. Generally, however, to permit the
greatest amount of air to pass over the wound area, it is preferred
that all of the outer layer be formed of the microporous material,
which must, therefore, be sufficiently supple to withstand almost
continuous flexure.
The inner macroporous layer should also be elastic, in this
situation. However, because there is no need to avoid stretching
the pores of the material or to avoid warping it in any way, the
fabric itself may be made elastic, or it can be formed, at least in
part of elastic fibers. Methods of preparing both woven and
non-woven elastic materials are well known to the art.
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