GB2526115A

GB2526115A - Wound dressing

Info

Publication number: GB2526115A
Application number: GB1408547.6A
Authority: GB
Inventors: Stephen Cotton
Original assignee: Brightwake Ltd
Current assignee: Brightwake Ltd
Priority date: 2014-05-14
Filing date: 2014-05-14
Publication date: 2015-11-18
Anticipated expiration: 2034-05-14
Also published as: GB201408547D0; GB2526115B

Abstract

A non-adherent wound dressing 1 comprising an adhesive skin or wound contact layer 15 provided with perforations 21,22, wherein the perforations 21,22 comprise a first set of perforations 21 of a first dimension in a centrally central region of the contact layer 15 that, in use, overlies a wound, and a second set or perforations 22 of a second dimension in a peripheral region of the contact layer 15 that in use overlies the peri-wound skin, the first dimension being greater than the second dimension. The skin contact layer 15 may be provided with a skin contact adhesive. The wound dressing 1 further comprises an absorbent body 14 positioned on the side of the contact layer 15 that, in use, is remote from the wound and in fluid communication with the first set of perforations 21. The dressing 1 performs as an atraumatic dressing which provide pain-free removal and the ability to remove a dressing without trauma to the wound.

Description

I

Wound dressing This invention relates to a non-adherent wound dressing, and in particular to such a wound dressing comprising a perforated skin-or wound-contact material.

Different types of wound dressing are required to meet different clinical needs.

However, there are several desirable characteristics that are common to all wound dressings. Pain-free removal and the ability to remove a dressing without trauma to the wound and the surrounding skin are two of the most important characteristics. In order to prevent pain and trauma, the facing layer of a wound dressing needs to maintain a moist layer over the wound to prevent adherence to the drying wound, However, it is also desirable for a wound dressing to include some form of adhesive layer to maintain it in position. However, repeated removal and replacement of such dressings can damage the pen-wound skin, ie the skin adjacent to the wound. The term "atraumatic dressing" is used in relation to products that, upon removal, do not cause trauma either to newly formed tissue or to the pen-wound skin. Dressings that do not adhere to the surface of a wound are (notwithstanding that they adhere to the healthy peri-wound skin) termed "non-adherent" or "low-adherent".

There is an ongoing need to provide improved wound dressings. No single wound dressing product is suitable for use in all wound types or at all stages of healing.

Dressings with adhesives that adhere to dry skin but do not stick to the surface of a moist wound and do not cause damage on removal are known in the art. One well-established class of such dressings has a skin-or wound-contact layer of a soft, hydrophobic silicone gel.

In many embodiments of such dressings, the skin-or wound-contact layer extends across the full extent of the dressing, and is perforated to permit the passage of wound exudate. Typically, the dressing includes an absorbent body, eg a gauze pad or an absorbent foam that takes up the exudate transmitted through the skin-or wound-contact layer. A disadvantage of the perforations that are present to permit passage of the wound exudate, however, is that they reduce the area of adhesive that is in contact with the ped-wound skin and so may diminish the ability of the dressing to remain securely in place.

There has now been devised a non-adherent wound dressing, which overcomes or substantially mitigates some or all of the above-mentioned and/or other

disadvantages of the prior art.

According to a first aspect of the invention there is provided a non-adherent wound dressing comprising an adhesive skin-or wound-contact layer provided with perforations, wherein the perforations comprise a first set of perforations of a first dimension in a generally central region of the contact layer that, in use, overlies a wound, and a second set of perforations of a second dimension in a peripheral region of the contact layer that, in use, overlies the pen-wound skin, the first dimension being greater than the second dimension.

The skin-or wound-contact layer is provided with two sets of perforations: the first set allows the transfer of wound exudate through the contact layer and the second set are small enough to avoid significant loss of adherence to the pod-wound skin, so that the dressing has sufficient adherence to remain securely in place during use. The second set of perforations offers an advantage over a dressing in which the peripheral region is unperforated, however, in that the perforations increase the permeability of the dressing to water vapour and to atmospheric oxygen, so reducing the likelihood of maceration of the skin to which the dressing is applied.

The perforations may also facilitate removal of the dressing, and provide for improved flexibility and conformability.

In many embodiments, the dressing comprises an absorbent body positioned on the side of the contact layer that is remote from the wound and in fluid communication with the first set of perforations, so that wound exudate may pass through the first set of perforations and be taken up by the absorbent body.

The first set of perforations are relatively large (in comparison to the second set) and are located such that they extend across the region of the wound dressing that, in use, is in the proximity of the wound itself. Generally, the first set of perforations are located near the centre of the dressing. Typically, the first set of perforations are circular and have a diameter of from 3mm to 20mm, preferably 3mm to 10mm, or 4mm to 7mm, and most preferably about 5mm.

The second set of perforations are smaller than the first set and are located such that they extend across the border of the dressing on the sections of the dressing that are intended to contact the healthy skin around the wound and not the wound itself. Typically, these perforations are also circular and have a diameter of from 0.5mm to 4mm. preferably from 0.5 to 2mm, and most preferably about 1mm to 2mm.

The presence of different sizes of perforation allows the adhesive dressing to adhere effectively to the healthy skin around the wound whilst also allowing transfer of exudate from the wound through the contact layer, into the absorbent body (if present). If small perforations were present across the full extent of the dressing, transfer of wound exudate may be restricted; if large perforations were present across the full extent of the dressing, adherence of the dressing to the surrounding skin may be reduced.

Other shapes of perforation may alternatively be used, eg square perforations or elongated slits. Some such arrangements of perforations may enhance the extensibility of the dressing in one or more directions, and so improve its conformability to the body.

The surface of the contact layer that, in use, is applied to the wound and ped-wound skin may be coated with an adhesive that extends across the entire extent of the wound dressing. The adhesive layer overlies and contacts the wound itselt rather than just the surrounding healthy skin, and so it is generally preferable that the adhesive that is used is one that is non-adherent and permits the wound dressing to be removed relatively easily and without causing trauma to the wound.

Thus, the adhesive may be, for instance, a hydrocofloid adhesive, a polyurethane adhesive, a hydrogel or, most preferably, a siflcone adhesive, particularly a sHicone gel.

Sihcone adhesives offer numerous advantages. Most preferably, the silicone adhesive is in the form of a silicone gel of the type generally referred to as a soft sHicone".

Soft silicone adhesives are particularly suited for use as skin contact layers in IC) wound dressings. They are soft. tactile and contormable. and exhibit good adhesion to dry skin but low adherence to an underlying wound. Thus, the dressing can be applied to a wound and subsequently removed without causing trauma to the wound. Silicone gels are adhesive but do not leave fibres or residue on a surface/substrate when removed.

ICC

Silicone gels suitable for use as skin contact materials in the present invention may be carried on a layer of meltThlown non-woven material, eg a sheet of melt-blown polyurethane (MBPU), as described in W02007/1 13597. The reverse side of the MBPU may be coated with an adhesive, eg an acrylic adhesive, to affix the silicone gel/MBPU laminate to overlying components of the dressing, eg an absorbent body and/or a backing layer, such as a breathable film of plastics material, for nstance polyurethane.

The wound dressings according to the invention typically comprise an absorbent body, which is intended to he in close proximity to the wound. Any suitable absorbent material may be used in the wound dressing.

The absorbent body may comprise a foam, a gelling material, a superabsorbent material, or a combination of these components.

The foam may be any suitable foam known in the art. Usually, the foam is an opencelled foam. Preferably, the foam is a hydrophihc foam, More preferably, the hydrophilic foam is a polyurethane foam. Most preferably, the foam is an open-celled polyurethane foam. The open cellular structure of the foam allows exudate from a wound to pass through it as well as be absorbed by it. The structure is sufficiently open to allow exudate to pass through it, but not sufficiently open to allow any part, eg a fibre or particle, of another material to pass through it to any substantial degree. The foam typically has a thickness of 0.5mm to 10mm, preferably from 1mm to 7mm, or from 2mm to 7mm, and the foam most preferably has a thickness of 2mm, 3mm, 4mm or 5mm.

By "gelling" material is meant in relation to the invention materials that are capable of absorbing aqueous fluid, such as wound exudate, and which on absorbing liquid become gel-like, moist and slippery. The gelling material is preferably in the form of a non-woven pad. The gelling material may have an absorbency of at least 2 grams 0.9% saline solution per gram of material, as measured by the free swell absorbency test (ie dispersing a known dry weight of material in the test liquid (saline) for sufficient time for the material to absorb liquid, removing the excess liquid by vacuum filtration, and measuring the increase in weight of the fibre). The absorbency may be considerably higher, eg at least 5gIg, or at least I Og/g, or at least lSg/g, or at least 25g1g.

The gelling material may be any suitable gelling material known in the art, including pectin, alginate, materials made from alginate and another polysaccharide, chitosan, hyaluronic acid, other polysacchaiide materials or materials derived from gums, or chemically-modified cellulosic materials, eg carboxymethyl cellulose (CMC). The gelling material may be a combination or blend of different gelling materials.

Currently preferred gelling fibres are alginate fibres and pectin fibres.

Superabsorbent material" in the context of the present invention means a material that is capable of absorbing many times its own mass of water (eg up to 200, 300, 400, 500 or more times its own mass of water).

Although it should be appreciated that the absorbent body of the present invention may comprise any superabsorbent material, preferred superabsorbent materials are polymeric superabsorbent materials and include alginate, polyacrylate (ie a salt of polyacrylic acid), polyacrylamide copolymers, ethylene maleic anhydride copolymer, carboxymethylcellulose, polyvinylalcohol copolymers, polyethylene oxide and starch-grafted copolymers of polyacrylonitrile.

Many such superabsorbent materials may be used in particulate form. In such cases, the particles may be incorporated into a carrier material, for instance by being encapsulated between two layers of carrier material, eg tissue paper or the like.

M alginate superabsorbent may be sodium or calcium alginate. The alginate superabsorbent is preferably in the form of a non-woven mat.

The most preferred superabsorbent material is sodium polyacrylate polymer.

Sodium polyacrylate polymer is a solid crystalline material, and is preferably incorporated into a layer in the form of particles encapsulated between two layers of carder material, such as tissue paper. A specific example of a suitable material is Gelok® 140405/S manufactured by Gelok International Corporation.

Particularly preferable is an absorbent body comprising a combination of one or more components. Typically, the absorbent body comprises two layers of absorbent materials. The absorbent body may comprise a wound facing foam layer and a superabsorbent layer bonded to the foam layer. Preferably the foam layer is an open-celled polyurethane foam. Preferably the superabsorbent layer is a sodium polyacrylate polymer, for example Gelok® 140408/S manufactured by Gelok International Corporation.

The wound dressings according to the invention typically comprise a backing layer, which forms a barrier between the wound and the surrounding atmosphere.

My suitable material known in the art may be used for the backing layer.

The backing layer wiU generafly be impermeable to wound exudate and other quids, but is preferably permeable to air and moisture vapour. In particular, the backing layer preferably exhibits a relatively high moisture vapour transmission rate (MVTR). The MVTR of the hacking layer may he at least 300g1m2/24h, more suitably at least SOOg/m2/24h and preferably at least 700g/m2/24h at 37°C and 100% to 10% relative humidity ditterenca The backing layer is most preferably a plastics film having the desired characteristics. The hacking layer may be a polyurethane film.

The backing layer may be larger in size than the absorbent body (if present), such that it exLends beyond the edge of the absorbent body on one or more sides.

Preferably, the backing layer extends beyond the edge of the absorbent body on all sides, forming a border around the absorbent body and is bonded to the peripheral region of the skin contact layer.

The dressing will generally be supplied with a releasable liner on its underside.

The releasable liner may cover the adhesive portions of the wound dressing prior to use, and be removed from the dressing immediately before application of the dressing to the wound. This reduces the risk of contamination of the wound dressing and facilitates handling of the dressing.

Such releasable liners are commonly used on wound dressings known in the art, and suitable materials which can he employed in the present invention will be familiar to the skilled worker. For example, the releasable liner may be of a suitable plastics sheet or a siliconised paper or the like.

The releasable liner may be a single sheet which covers the underside of the wound dressing! or may be formed of two or more sheets. The releasable liner may further comprise a tab to enable the liner to be easily removed from the dressing before use. n particular, where the releasable liner is formed of two or more parts, the parts may either overlap or abut and extend outwards from the wound dressing! thus providing an easy method for removal of the releasable liner.

The invention will now be described in greater detail, by way of example only, with reference to the accompanying drawings, in which Figure 1 is a plan view of a wound dressing according to the invention; Figure 2 is cross-sectional view of the wound dressing of Figure 1, on the line Il-Il and not to scale; and Figure 3 is an underside view of the wound dressing of Figures 1 and 2, after removal of a releasable liner.

Referring first to Figures 1 and 2, there is shown a wound dressing according to the invention, generally designated 1. The dressing I is generally square in form and comprises a backing layer of microporous, gas-and vapour-permeable polyurethane film 11, to a central portion of the underside of which is affixed an absorbent body 12 (see Figure 2).

The absorbent body 12 comprises a layer of polyurethane foam 13, the upper (as viewed in Figure 2) surface of which is bonded to a sheet of superabsorbent material 14. The sheet of superabsorbent material 14 comprises particles of sodium polyacrylate polymer encapsulated between two layers of tissue paper carrier material.

A perforated skin contact layer 15 extends across the whole extent of the underside of the dressing I, and is covered by a protective release liner I 6a,1 6b.

As can be seen in the underside plan view of Figure 3, the contact layer 15 is formed with two different arrays of perforations: larger perforations 21 and smaller perforations 22, The larger perforations 21 are formed in the central portion of the dressing I and coincide with the absorbent body 12. These perforations 21 have approximate diameter 5mm, to permit wound exudate to pass from the wound into the foam 13 and the superabsorbent material 14. The smaller perforations 22 are formed in the border of the contact layer 15, ie the porfion surrounding, bL!t not extending over, the absorbent body 12. These perforations have a diameter of 1-2mm and permit the passage of water vapour and gas from the surface of the skin surrounding a wound, through the backing layer 11 Maceration of the pen-wound skin is thereby avoided, but the smafler perforations 22 do not substantiafly impair secure retention of the dressing I on the skin. The silicone gel layer 15 contacts not only the healthy skin around the wound, but also the wound itself, with the absorbent body 12 exposed to the wound through the large perforations 21. The non-adherent properties of the sUicone gel skin contact layer IC) 15 permit the dressing I to be removed from the wound without trauma or pain.

The silicone gel skin contact layer 15 comprises a sheet of melt-blown polyurethane that carries a coating of silicone gel. The reverse side of the melt-blown polyurethane is coated with acrylic adhesive by which it is affixed to the border of the backing layer 11 and to the absorbent body 12.

The wound dressing is supplied with a two-part release liner 16a,16b (shown in Figure 2, but not in Figure 3), which is removed from the dressing 1 immediately prior to use.

When the dressing 1 is applied to a wound, wound exudate passes through the larger perforations 21 into the absorbent body 12, the superabsorhent material 14 in particular having a substantial absorptive capacity.

The dressing may be manufactured by the following general method.

First, a pre-laminate comprising the silicone gel layer is produced in the manner described in W020071113597. In general terms, this involves applying silicone gel precursors to a sheet of melt-blown polyurethane (MBPU), the underside of which carries a coating of acryUc adhesive and a temporary protective backing. eg of plastics film or paper. Once the silicone gel precursors have cured, to produce a hydrophobic silicone gel, a temporary cover, again of plastics film or paper materiaL is appUed to the geL Perforaflons corresponding to the larger and smafler perforations 21,22 are then formed in the pre-laminate.

ri a separate operation, the absorbent body is produced by sandwiching sheets of foam and superabsorbent material together. ndMdual squares, or other appropriate shapes, are then cut out.

The squares of the absorbent body are then positioned on a sheet of breathable polyurethane film (which constitutes the backing layer 11 of the finished dressing IC) 1). The temporary protective hacking is removed from the underside of the MBPU to expose the acrylic adhesive and the pre-laminate is appUed to the polyurethane film with the large perforations 21 in registration with the squares of absorbent body 12. Finally, the temporary protective cover is removed from the silicone gel and replaced with appropriately formed release liners 16a,16b, and individual dressings I are punched out and sterile-packaged.

Claims

C'aims I. A non-adherent wound dressing comprising an adhesive skin-or wound-contact gayer prcMded with perforafions, wherein the perforations comprise a first set of perforations of a first dimension n a generafly centra' region of the contact ayer that, in use, overUes a wound, and a second set of perforations of a second dimension in a periphera' region of the contact ayer that, in use, overVes the pen-wound skin, the first dimension being greater than the second dimension.

IC)
2. A wound dressing according to any preceding daim, wherein the first set of perforations are from 3mm to 20mm in diameter.
3. A wound dressing according to C'aim 3. wherein the first set of perforations are about 5mm in diameter.ICC
4. A wound dressing according to any preceding daim, wherein the second set of perforations are from 0.5mm to 4mm in diameter.
5. A wound dressing according to Caim 4, wherein the second set of perforations are about 1mm to 2mm in diameter.
6. A wound dressing according to any preceding daim, wherein the first or second set of perforations are circu'ar.
7. A wound dressing according to any preceding daim, wherein at east part of the surface of the contact ayer that, in use, contacts a patienfs skin is provided with a skin contact adhesive.
8. A wound dressing according to Oaim 7, wherein the skin contact adhesive is a soft sUicone adhesive.
9. A wound dressing according to Caim 8, wherein the soft siUcone adhesive is carried on a ayer of m&t-bown non-woven materiaL
10. A wound dressing according to any preceding claim, wherein the wound dressing further comprises an absorbent body positioned on the side of the contact layer that, in use, is remote from the wound and hi fluid communication with the first set of perforafions.
11. A wound dressing according to Claim 10, wherein the absorbent body comprises two layers of absorbent materials.IC)
12. A wound dressing according to Claim 11, wherein the absorbent body comprises a foam layer and a superabsorbent layer.
13. A wound dressing according to any preceding claim, wherein the dressing comprises a backing layer that has a moisture vapour transmission rate of at least 300g/m2124h at 37°C.
14. A wound dressing according to Claim 13, wherein the backing layer is a polyurethane film.
15. A wound dressing according to any of Claims 7-14, wherein the skin contact adhesive is provided with a releasable liner.
16. A wound dressing according to Claim I, wherein the first set of perforations are from 3mm to 20mm in diameter; and the second set of perforations are from 0.5mm to 4mm ri diameter.
17. A wound dressing according to Claim 16, wherein at least part of the surface of the contact layer that, in use, contacts a patient's skin is provided with a soft silicone skin contact adhesive; and the dressing further comprises an absorbent body positioned on the side of the contact layer that, in use, is remote from the wound and in fluid communication with the first set of perforations.
18. An absorbent component or wound dressing substantially as hereinbefore described and as illustrated in the accompanying Figures 1 and 2.