CZ388398A3 - Bandage for wounds - Google Patents

Abstract

A wound dressing (10; 110; 210) for dressing a wound (2; 102; 202) on a tissue structure of a living human or animal body comprising a lower section (1; 101; 201) which when the wound dressing dresses the wound is disposed adjacent the wound, the lower section being fluid permeable and comprising a bioresorbable material which promotes the healing process in the wound, and an upper section (3; 103; 203) which when the dressing dresses the wound overlies the lower section, the upper section being permeable to vapour and impermeable to bacteria. The wound dressing may be an integrally formed structure, an integrated structure or formed when the wound is dressed.

Description

Technical field

The present invention relates to wound dressings for covering wounds in the internal or external tissue structures of living human or animal bodies.

BACKGROUND OF THE INVENTION

Existing wound dressings have a large number of disadvantages. Typically, gauze dressings have been used to treat wounds such as burns, cuts, abrasions and other tissue disruptions. However, such dressings require frequent replacement and application, and subsequent removal of the fresh replacement dressing may be painful to the patient. Some bandages are really so unsatisfactory that they can immobilize the patient.

It is shown in EP-A-0349505 (Astra Meditec. AB) that the healing of soft tissues of mammals including humans can. can be improved by using a porous, flexible, protein-free, bioabsorbable polymer layer having pores of a size permitting the passage of water and salts, while impermeable to cells and other tissue sections. It is shown that such a layer has a specific stimulating effect for soft tissue macrophages that release a growth factor that stimulates tissue healing. Suitable polymeric materials disclosed in EP-A-0349505 for such layers are those based on polyglycolic acid, lactic acid and ε-aminocaproic acid copolymers, lactide polymers, polydesoxazone, poly-3-hydroxybutyric acid, poly3-hydroxybutyric acid copolymers and 3-hydroxyvaleric acid, succinic polyesters and cross-linked hyaluronic acid.

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EP-A-0349505 discloses the formation of a non-woven strip of 3-hydroxybutyric acid with the desired properties by compressing the fibers of 3-hydroxybutyric acid produced according to US-A-4603070 (Steel et al. ), centrifuging from the solution.

Since the pore size of the layer according to EP-A-0349505 is sufficient to allow water to pass through, there is a possibility of bacteria passing through the coating to the wound. Although this might not be so problematic when the layer is for internal use, in other words, for placement in a human or animal body to cover the internal wound, it could be problematic in the case of external wounds such as skin injuries.

GB-A-2166354 (Imperial Chemical Industries. Plc) discloses a wound dressing comprising a poly-3-hydroxybutyric acid polymer dissolved or soaked (swollen) with a volatile solvent such as chloroform, preferably polymerized together with 3-hydroxyvaleric acid units. The substance is coated with a wound as a solution or gel to form a thin polymer film in close contact with the treatment area. Poly-3-hydroxybutyric acid is said to be hydrophilic, eliminating the need for an outer hydrophilic layer. The dressing is said to be particularly suitable for rapidly protecting the wound site with temporary dressing.

The thin layer of poly-3-hydroxybutyric acid described in GB-A-2166354 has a number of disadvantages as a wound dressing. Firstly, it does not allow the removal of excess fluid, since the 3-hydroxybutyric acid layer is not particularly absorbing and will not pass through the wound exudate. Furthermore, it may have been difficult to remove the dressing from the open wound and the volatile solvent in the dressing is often toxic to the cells and could cause irritation at the wound site. In addition, distribution

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The pore size formed by the 3-hydroxybutyric acid layer is such that the pore size closest to the wound is smaller than the pore size distant from the wound. Therefore, there is the possibility of infection of the wound by entering bacteria into the dressing.

In summary, the prior art has not solved the problem of providing a suitable wound dressing for use during gradual wound healing, which can be conveniently applied and, if necessary, easily removed, and which provides thermal insulation to maintain body temperature adjacent the wound surface and maintains the wound is moist but allows excess liquid to be removed from the wound.

The present invention proposes to improve this situation.

SUMMARY OF THE INVENTION

The present invention provides a wound dressing for covering a wound in a tissue structure of a living human or animal body which, when covering the wound, has a lower outer surface positioned adjacent the wound, an upper outer surface separated by a gap from the lower outer surface, a liquid pervious lower portion; which is the Lower Outer Surface and consists of a bio-resorbable material that promotes the wound healing process, and a porous upper portion overlying the lower outer surface representing the upper outer surface, the pore size of the porous upper being less than about 0.25 μτη, whereby the upper portion is permeable to evaporation and impermeable to bacteria.

It is relatively easy to make such a bandage. In addition, the dressing is easy to apply and can be modified to allow easy removal. The dressing further provides thermal insulation to maintain body temperature adjacent the wound surface and keeps the wound moist although it removes excess fluid from the wound.

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Guaranteeing that the upper portion is substantially impermeable to bacteria also means that a barrier is present to prevent infection.

Transport of exudate from the wound could be avoided by:. the exudate has no possibility of escaping after it has accumulated on the upper surface of the lower part distant from the wound. The provision of a vapor-permeable top portion alleviates this problem by allowing the exudate to slowly dissipate by evaporation. In addition, fumes from the tissue surrounding the wound may also pass through the upper portion.

Drainage of the exudate from the wound to the lower part of the dressing and subsequent evaporation of the excess moisture represents the mass flow in the direction of discharge from the wound to the atmosphere. This flow further prevents the bacteria from passing in the opposite direction and thus the occurrence of infection.

The wound dressing of the present invention may be left in place for a relatively long time. This means fewer dressing changes are needed than previously, which prevents disruption of the healing process and means less pain for the patient.

The use of a vapor-permeable top ensures that the wound is kept moist, no matter how effective the removal of excess fluid from the wound is. Preventing the wound from drying out results in pain being controlled.

In a first embodiment of the invention, the wound dressing has an integral structure.

In a second embodiment of the invention, the wound dressing is formed as an integrated structure. For example, the top and bottom portions may be the top and bottom layers of the wound dressing that are joined to each other prior to the wound dressing.

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In a third embodiment of the invention, the wound dressing is formed only when the wound is covered, for example the upper and lower portions are represented by the upper and lower wound dressing layers, which are applied separately to the wound.

The lower part of the wound dressing in the form of a lower wound dressing, for example a flat structure, allows easy placement and use as barriers facilitating the transport of exudate from the wound and keeping it away from the wound.

In an embodiment of the invention, according to its various forms, the wound dressing further comprises an intermediate portion between the upper and lower portions, which is adapted to absorb fluid. This is particularly advantageous where a large amount of exudate is contemplated. For the second and third embodiments of the invention, the intermediate portion may be of any suitable material, such as treated cellulose or polyacrylic acid fibers. However, a hydrocolloid is particularly suitable. The hydrocolloid is normally capable of absorbing a quantity of fluid corresponding to four to six times its volume, and it has been reported that new hydrocolloids absorb 20 times more than their own volume. The hydrocolloids are also adhesive to the skin, so that the hydrocolloid can have the dual function of an intermediate absorbent layer and an adhesive edge for the wound dressing. The middle portion in the second and third embodiments of the invention may be in the form of an intermediate wound dressing layer or instead be part of an upper or lower wound dressing layer. ....

In a first embodiment of the invention, the wound dressing comprises an upper and a lower portion, the upper and lower portions comprising a biosorbable material. The biosorbable material may be in the form of particles or fibers. For example, the wound dressing may comprise particles or fibers of a biosorbable material in the material

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A matrix such as a hyaluronic acid gel matrix or the like. On the other hand, the wound dressing may be a sheet of biosorbable material, for example a layer of nonwoven fibers.

In a second and third embodiments of the invention, the one or more layers of the wound dressing are in the form of one or more flat wound dressing structures.

In a second embodiment of the invention, the wound dressing comprises an upper and a lower layer of the wound dressing, the lower layer of the dressing being adhered to the lower surface of the upper layer of the wound dressing. As an alternative, where the wound dressing comprises an intermediate wound dressing layer, the upper and lower wound dressing layers are adhered to the upper and lower surfaces of the intermediate wound dressing layer, respectively.

In a second embodiment of the invention, the backsheet of the wound dressing is releasably attached to the remainder of the wound dressing. For example, the lower wound dressing layer may be releasably attached to the lower surface of the upper wound dressing layer or to the lower surface of the middle wound dressing layer.

In a preferred embodiment of the invention in its various forms, the bottom of the wound dressing is substantially free of volatile solvent.

In the second and third embodiments of the invention, the backsheet of the wound dressing is a layer of particles of a bioabsorbable material. The particles may be supported by a matrix material, for example a gel matrix containing hyaluronic acid.

In a second embodiment of the invention, the biologically resorbable particulate material of the wound dressing lower layer is adhered to the lower surface of the upper or middle wound dressing layer by mixing the particles in a solvent, coating the lower surface of the mixture, and then evaporating the solvent. Chloroform may be mentioned as a suitable solvent.

In a third embodiment of the invention, the lower part of the dressing, when the wound dressing covers the wound, is represented by a layer of loose particles or fibers of biosorbable material placed on the wound. As an alternative, the wound dressing backsheet may be a gel comprising a biologically resorbable wound dressing material, or one or more of the wound dressing lower surface structures.

In a second and a third embodiment of the invention, the biologically resorbable backsheet material of the wound dressing is in the form of fibers, for example supported by a matrix, such as a gel matrix formed of hyaluronic acid. As an alternative, the wound dressing backsheet may be in the form of one or more lower wound dressing structures of fibers, for example of nonwoven fibers, in which case the bottom surface of the wound dressing backsheet may be preferably roughened to expose the fiber ends .

In various embodiments of the invention, the biosorbable backsheet material is a polymer. For example, the polymer is protein-free, such as poly-3-hydroxybutyric acid (PHB), polylactic acid, polyglycolic acid, glycolic acid and lactic acid copolymers, lactic acid copolymers, and ε-aminocaproic acid, lactide polymers, polydesoxazone, poly-3 copolymers. hydroxybutyric and 3-hydroxyvaleric acids, polyesters of succinic acid and cross-linked hyaluronic acid.

The use of a biologically resorbable protein-free polymer in the lower part of the dressing stimulates the healing process.

Degradation by stimulating macrophages, creating a barrier against the boundaries and acting as a construct for cell growth. Macrophage invasion caused by protein-free polymers covers the tissue wound and effectively controls wound pain for one or two days. Vascularization and microcirculation, again stimulated by the polymer, occur. In addition, degradation of certain protein-free polymers such as PHB has a bacteriostatic and fungistatic effect and facilitates wound healing. Invading macrophages also have a bactericidal effect. The wound dressing can be left in place for extended periods of time due to bacteriostatic and fungistatic properties and the healing environment created for the wound under the wound dressing. Fewer dressing changes mean less disruption of the healing process and less pain for the patient.

Poly-3-hydroxybutyric acid is the preferred material for the lower part of the dressing because the Applicant has found that PHB has the ability to attract macrophages to the wound site to a greater extent than other polymers tested. PHB also appears to lead to increased vascularization, perhaps through the action of PHB-promoted macrophages. In addition, the cover period is further extended with the use of PHBs due to the fact that bacteriostatic and fungistatic properties increase over time with degradation of PHBs.

In addition, when the lower portion is formed as a sheet structure of PHB fibers, for example as a nonwoven layer, the hydrophobic PHB fibers have the property that the structure of this material has a considerable capillary capacity which helps to remove and retain the exudate from the wound. between this structure and the top of the dressing. In addition, the non-woven PHB fiber structure will swell during the first ten days or the like by adding blood components and cells from adjacent tissues due to its construction despite the fibers being hydrophobic. It is possible to conclude that the structure (layer) · fefe fefe fefe fefe fe · fefe feefefe fefe fefe fefe fefe fefe

9 of the PHB fibers as the lower part of the wound dressing will allow the wound to breathe and allow the transport of steam, leaving the wound surface in adequate moisture.

When oligo-3-hydroxybutyric acid, eg containing 3 to 10 monomer units, is selected instead of poly-3-butyric acid, it may also be included in the. the lower portion of the bandage or may form the lower portion.

A variety of other materials may be suitable for the function of the lower part of the dressing, as will be understood by those skilled in the art, but non-limiting examples are polysaccharides such as chitosan, collagen and proteins.

In various embodiments of the invention, the wound dressing is flexible, and this allows the wound dressing to follow the wound profile, for example in the case of a protruding wound.

In a second and a third embodiment of the invention, the wound dressing backsheet is adapted to follow the wound profile, for example by being flexible.

In order to facilitate the healing process in the wound, the lower portion of the various wound dressing forums of the invention may carry one or more growth factors.

In a second and third embodiment of the invention, the top layer of the wound dressing comprises a polymeric material. The polymeric material may be bioabsorbable and may further be protein-free. E.g. the top portion may contain poly-3-hydroxybutyric acid. As an alternative, the top portion may comprise a non-biodegradable and non-biodegradable material, non-limiting examples of polymeric material being polyurethane and polytetrafluoroethylene.

Where the upper and lower portions are both porous, the pore size of the upper portion is smaller than the pore size of the lower portion.

In various embodiments of the invention, the wound dressing has an adhesive edge for releasable adhesion to the tissue surface.

- 10 structures adjacent to the wound. This facilitates application and removal of the dressing or the top thereof.

In the second and third embodiments of the invention, the top wound dressing layer is an adhesive edge, in which case the top wound dressing layer may completely surround the bottom wound dressing layer. The edge for ideal overlap is approximately 10 to 15 mm. Where the top-wound dressing layer comprises an intermediate portion, the adhesive edge may be the middle portion of the top-wound dressing layer.

In a second and third embodiment of the invention, the adhesive edge is the middle layer of the wound dressing.

The present invention also provides a method of treating a wound in a tissue structure of a living human or animal body comprising the steps of applying a wound dressing according to the invention to a wound.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings.

Description of the picture

Giant. 1 is a side cross-sectional view of a wound dressing according to a first embodiment of the present invention.

Giant. 2 is a side cross-sectional view of a wound dressing according to a second embodiment of the present invention.

Giant. 3 is a side cross-sectional view of a wound dressing according to a third embodiment of the present invention.

Examples of embodiments of the invention

Example 1

As can be seen in Fig. 1, the wound dressing 10 of the present invention comprises a layer also of a bio-resorbable material that promotes - healing processes, in this case poly-3-hydroxybutyric acid - (hereinafter PHB), applied to the skin 2. in the form of a nonwoven web substantially free of volatile solvent, and an outer microporous layer 3 of polyurethane polymer. Pores. the outer polymer layers 3 have a size of less than 0.22 µm. This provides a vapor and gas permeable layer 2 while keeping the layer 3 substantially impermeable to bacteria.

The wound dressing 10 can be conveniently applied and removed, and further provides thermal insulation to maintain body temperature adjacent to the wound surface due to the outer polymeric layer 3. The wound dressing 10 also keeps the wound 2 moist but permits moisture vapor permeability. removing excess fluid from the wound 2. Thus, it prevents the nerve endings from drying out in the wound and the accompanying pain of the patient.

To facilitate application and removal of the wound dressing 10, the outer radiused layer 3 has an adhesive edge 4.

The PHB fibers in dressing 10 have hydrophobic properties. The nature of the PHB fibers is such that the exudate is removed from the wound 2 and retained in the PHB layer 1 and in the space between. layer .PHB 1. and outer radius layer 2.

The wound dressing 10 may be left in place for a relatively long time. This means that less dressing changes are required than for the previously proposed dressings. This prevents disruption of the healing process and means less pain for the patient. One possibility to change the dressing 10 would be to remove only the outer layer of polymer 3 and excess liquid, then apply a fresh outer layer 3 in place without breaking the PHB layer 1. As an alternative, most of the PHB layer 1 can also be removed and replaced by a fresh PHB layer. leaving the PHB fibers adhering to wound 2.

Example 2

FIG. 2 shows a second wound dressing 110 according to the present invention comprising a PHB layer 101 applied to a skin wound 102 in the form of a fibrous nonwoven web substantially free of volatile solvent, and an outer microporous layer 103 of polyurethane polymer. The PHB 101 layer is in the form of a patch completely surrounded by the outer polymeric layer 103, leaving a margin (m) of the outer polymeric layer 103 10-15 mm wide around the PHB 101. The PHB size of the patch 101 itself may vary according to wound size 102.

Further, an intermediate absorbent layer 105 of hydrocolloid material is provided. It absorbs exudate which is transported from the wound 102 through the PHB 101 patch and promotes the transport of further exudate. The microporosity of the polyurethane outer layer 103 means that the exudate can be slowly dispersed while the wound 102 is kept wet while not allowing bacteria to enter.

The outer polymeric layer 103 has an adhesive edge 104 for facilitating application and removal of the dressing 110.

Example 3

FIG. 3 illustrates a third wound dressing 210 according to the present invention comprising a PHB layer 201 applied to the skin wound 202 in the form of a fibrous nonwoven fabric.

13 flat structures substantially free of volatile solvent, and an outer microporous layer 203 of polyurethane polymer.

Again, the PHB is in the form of a patch completely surrounded by an outer polymeric layer 203 with a 10 to 15 mm wide polymer (m) edge around the PHB patch. Again, there is an intermediate absorbent layer 205 of hydrocolloid material, but in this case the hydrocolloid layer 205 is integral with the outer polymer layer 203. Thus, the hydrocolloid performs the dual function of the intermediate absorbent layer and the adhesive edge for the outer layer 203.

The reader will appreciate that the invention is not limited to the specific examples of wound dressings described above with reference to the accompanying drawings, but that the invention may be embodied in many forms or forms within the scope of the claims.

The Applicant has found that the wound dressing should meet the following objectives:

• Thermal insulation should maintain the body temperature of the wound surface.

• The wound should be kept moist, but excess fluid should be removed.

• The wound dressing should be vapor permeable, but impermeable to bacteria.

• .Wound dressing by. should absorb and breathe ......

• Pain should be controlled.

• The wound dressing should be easy to apply and, if necessary, easily removed.

• The wound dressing should stimulate healing.

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- 14 • The wound dressing should be consistent with other treatments, such as allowing the application of an external compression bandage and effective separation of dead skin tissue.

• The wound dressing should be biocompatible and non-toxic.

• The wound dressing should not immobilize the patient.

The wound dressings of the present invention described above with reference to the accompanying drawings accomplish these objectives simply and inexpensively.

Example 4

In the comparative test, a wound dressing according to the invention and a wound dressing comprising a layer of polyurethane (Tagerderm) were used to cover the skin wound of the mammalian body. The dressing of the invention consisted of a lower part in the form of a nonwoven sheet of PHB fibers and an upper part of a polyurethane layer. The wound dressing of the invention produced improved wound healing compared to a polyurethane layer wound dressing. This was evident in that the healed wound covered with the wound dressing of the present invention had a thicker and higher quality epithelial cell layer of regenerated tissue than the healed wound covered with the wound dressing with only the polyurethane layer.

Claims (33)

PATENT CLAIMS A wound dressing for covering a wound in a gray human or animal body tissue structure, characterized in that, when the dressing covers the wound, it has a lower outer surface positioned so as to abut the wound. an upper outer surface separated by a gap from the lower outer surface and having a liquid pervious lower portion, said lower portion being a lower outer surface and comprising a bio-resorbable material that promotes a healing process in the wound, and a porous upper portion overlying the lower portion; this upper portion represents the upper outer surface, and wherein the pore size in the porous upper portion is less than about 0.25 μπι, thereby rendering the upper portion vapor permeable and impermeable to bacteria. A wound dressing according to claim 1, wherein the lower portion is liquid pervious. The wound dressing according to claim 1 or 2, wherein the lower portion of the wound dressing is substantially free of volatile solvent. A wound dressing according to any one of claims 1 to 3, wherein the biosorbable material is in the form of particles or fibers. The wound dressing of claim 4, wherein the particles or fibers of the biosorbable material are in the matrix material. «T t * * * * * * * * * · - 16 The wound dressing of claim 5, wherein the matrix is a gel matrix. 7. The wound dressing of claim 5 wherein the gel matrix is hyaluronic acid. A wound dressing according to any one of claims 1 to 7, wherein the biologically resorbable backsheet material comprises a polymer. The wound dressing according to claim 8, wherein the polymer is protein-free. A wound dressing according to claim 9, wherein the polymer is poly-3-hydroxybutyric acid, polylactic acid, polyglycolic acid, glycolic acid and lactic acid copolymer, lactic acid-ε-aminocaproic acid copolymer, lactide polymer, polydesoxazone. , a copolymer of poly-3-hydroxybutyric acid and 3-hydroxyvaleric acid, succinic polyester or cross-linked hyaluronic acid. The wound dressing according to claim 1, wherein the lower portion comprises poly-3-hydroxybutyric acid and oligo-3-hydroxybutyric acid. A wound dressing according to any one of claims 1 to 7, wherein the biologically resorbable backsheet material comprises a polysaccharide such as a lipopolysaccharide, chitosan, collagen or protein. 13. Bandage on wounds according to any one of claims 1 to 12, confesses in c u by that lower part Yippee porous. 14. Bandage on wounds according to claim 13, v y brand ují c í is three m, that the pore size of the top part is smaller than pore size bottom parts. 15, Bandage on wounds according to any one of claims 1 az 12, confesses in c u by that . lower part Yippee perforated. A wound dressing according to any one of the preceding claims, wherein the lower portion carries one or more growth factors. A wound dressing according to any one of claims 1 to 16, wherein the upper portion comprises a non-biosorbable material. The wound dressing of claim 17, wherein the top portion comprises a non-biosorbable polymeric material. A wound dressing according to claim 18, wherein the polymeric material is polyurethane or polyurethane. polytetrafluoroethylene. The wound dressing according to any one of claims 1 to 19, wherein the wound dressing further comprises an intermediate portion between an upper and a lower portion that is adapted to absorb fluid. • · «* 21. Bandage on early according to claim 20, characterized c í s e that middle part contains hydrocolloid. 22nd Bandage on early according to any from claims 1 to 21, v y from us j í c í s by putting a wound dressing Yippee integral structure. 23. Bandage on early according to Claim 22 if it is dependent on claims 1 to 19, characterized in that the wound dressing consists of an upper and a lower part, wherein the wound dressing comprises a wound dressing upper and lower material. parts contain biological resorbovatelný 24. Bandage on early according to claim 2 2 or 23, ..... • her c í s e team that bandage for wounds is in flat form structure. 25. The wound dressing according to claim 23, wherein the wound dressing is a fibrous sheet structure of a biosorbable material. 26. Bandage on wounds according to claim 25, s n a č u j ici by structure. that bandage on early is nonwoven fibrous flat 27 Mar: Bandage for wounds according to claim 25 or 26, v y from us emerging t í m that the bottom surface bandage The wound is roughened to expose the fiber ends. Wound dressing according to any one of claims 22 to 27, characterized in that the wound dressing is ···· - 19 flexible, allowing the dressing to follow the wound profile, such as a protruding wound. A wound dressing according to any one of claims 1 to 21, characterized in that the wound dressing is formed as an integrated structure. 30. The wound dressing of claim 29, wherein the top and bottom portions are the top and bottom layers of the wound dressing, respectively, joined to each other prior to wound coverage. A wound dressing according to any one of claims 1 to 21, characterized in that the wound dressing is only formed when the wound is covered. 32. The wound dressing of claim 31, wherein the top and bottom portions are the top and bottom layers of the wound dressing, respectively, which are applied separately to the wound. 33. The wound dressing of claim 31, wherein when the wound dressing covers the wound, the lower portion is a layer of loose particles or fibers of a biosorbable material disposed on the wound. 34. A wound dressing according to claim 32, wherein when the wound dressing covers the wound, the lower layer of the wound dressing is a gel containing a biologically resorbable material to cover the wound. 44 44 • 4 4 4 • 43 4 4 · · 4 * 4 · 44 • 4 20-2144 44 • 4.4 · 4 4 4 · 444 444 4 4 44 44 35,. A wound dressing according to any one of the claims. 30 or 32 when dependent on any one of claims 20 to 21, wherein the intermediate portion is in the form of an intermediate layer of wound dressing. The wound dressing according to claim 30, 32 or 35, wherein the one or more layers of the wound dressing are in the form of one or more planar wound dressing structures. ' 37. Wound dressing. according to claims 30, 32, 35 or 36, characterized in that the lower layer of the wound dressing is adapted to follow the wound profile. 38. The wound dressing of claim 37 wherein the wound dressing backsheet is flexible. A wound dressing according to any one of claims 30, 32 or 34 to 38, characterized in that the wound dressing is as follows. characterized in that the top layer of the wound dressing comprises a polymeric material. 40. The wound dressing of claim 39, wherein the polymeric material is biosorbable. . ? * 41. The wound dressing of claim 40, wherein the polymeric material is protein-free. 42. The wound dressing of claim 41, wherein the top portion comprises poly-3-hydroxybutyric acid.