GB2531345A

GB2531345A - Composite wound dressing

Info

Publication number: GB2531345A
Application number: GB1418454.3A
Authority: GB
Inventors: Stephen Cotton
Original assignee: Brightwake Ltd
Current assignee: Brightwake Ltd
Priority date: 2014-10-17
Filing date: 2014-10-17
Publication date: 2016-04-20
Also published as: GB201418454D0

Abstract

A composite wound dressing 1 comprising a superabsorbent material 12, and a layer of activate carbon cloth 13. The wound dressing may be arranged such that wound exudates passes through the layer of carbon cloth before being absorbed by the superabsorbent material. The activated carbon cloth may be of knitted form and may be position directly below the superabsorbent material and bond or held thereto. The dressing may include a further absorbing body located between the activated carbon cloth layer and the superabsorbent material. The carbon cloth layer may be the wound contacting layer, or an additional wound contact layer may be provided 14, which can be formed of a non-woven blend of polyester and viscose or a melt-blown polyurethane film with a silicone gel. The superabsorbent material may comprise a polymeric superabsorbent material, such as alginate, polyacrylate, polyacrylamide copolymers, ethylene maleic anhydride copolymer, carboxymethylcellulose, polyvinyl alcohol, polyethylene oxide or starch-grafted copolymers of polyacetonitrile. The wound dressing may further comprise antimicrobial, antiseptic, antifungal or anti-inflammatory agents, such as silver, polyhexamethylene biguarnide or honey. The wound dressing may further comprise a backing layer 11 formed of polyurethane film and extend beyond all the edges of the carbon cloth to form a border around said carbon cloth.

Description

Composite Wound Dressing This invention relates to a composite wound dressing, and in particular to a composite wound dressing comprising a layer of carbon cloth and superabsorbent material.

Different types of wound dressing are required to meet different clinical needs, and no single wound dressing product is suitable for use in all wound types or at all stages of healing. There is therefore an ongoing need to provide improved wound dressings.

However, it is a common requirement for wound dressings that wound exudate is absorbed, and that bacteria and other sources of infection are efficiently removed from the wound. It is further important that, particularly in the treatment of chronic wounds, odour-causing molecules are removed in order to improve the comfort and confidence of the patient. Activated carbon cloth has been found to be effective in the removal of excess wound exudate and adsorption of odour-causing molecules, as well as displaying antimicrobial properties, and has been used in wound dressings for these reasons. Carbon cloth has the additional benefit that its durable, flexible structure means it flexes and moves easily with the patient, and can be worn for a number of days without structural deterioration. Activated carbon cloth is particularly used in the treatment of chronic wounds, eg those resulting from bed sores, pressure ulcers, leg ulcers, MRSA, skin grafts, burns, infected cuts and surgical wounds.

Zorflex® is a commercially available activated carbon cloth, known for use in wound dressings. It is a woven or knitted 100% activated carbon cloth with a surface area of 1000-2000 m2/g, which can be laminated to other materials or impregnated with chemical treatments.

Commercially available wound dressings incorporating activated carbon cloth are also available, and include Actisorb® plus (Johnson & Johnson Medical Ltd).

Actisorb® plus is a sterile dressing comprising an activated charcoal cloth, produced by carbonising and activating a knitted viscose rayon fabric, which is enclosed in a sealed, non-adherent nylon sleeve. This dressing has been found to trap odour and bind bacteria and toxins that impair the healing process. It is important that the dressing is not cut, otherwise particles of activated carbon may get into the wound and cause discolouration.

Carbonet is also a multi-component dressing that combines both fluid-and odour-absorbing properties. It consists of a low adherence wound contact layer of knitted viscose backed with an absorbent layer of fibrous cellulose to which is bonded a layer of activated charcoal cloth, the whole of which is sandwiched between two layers of polyethylene net. An outer layer of polyester fleece completes the structure of the dressing. The dressing should be changed when the absorbent material becomes saturated, causing the carbon cloth to become wet, as this reduces the odour-absorbing properties of the carbon cloth.

It is important for many applications that a wound dressing is able to absorb a significant amount of liquid. During the healing process, wounds produce exudate.

This is absorbed by the dressing in order to keep the wound clean and promote healing. A determining factor in how regularly a dressing needs to be changed is how quickly the dressing becomes saturated with exudate. Infrequent dressing changes are preferable as changing a dressing can aggravate a wound, as well as causing pain and/or discomfort for the patient. It is essential for efficient wound healing that the area of the wound be kept moist by the surrounding skin be kept dry to avoid maceration.

Superabsorbent materials, which can absorb many times their own weight in liquid, are known for use in wound dressings due to their high absorption capability. Often, superabsorbent materials are used in particulate form, and a common problem associated with them is the need to prevent particulate matter from the superabsorbent material being transferred into the wound.

There is now provided an improved wound dressing which overcomes and/or substantially mitigates problems associated with the prior art.

According to the invention, there is provided a composite wound dressing comprising a superabsorbent material and a layer of activated carbon cloth.

It has been found that the combination of carbon cloth and a superabsorbent material in a composite wound dressing is particularly advantageous. The superabsorbent material actively draws wound exudate through the carbon cloth.

As the wound exudate is drawn through the carbon cloth, bacteria are adsorbed by the cloth, thus permanently removing them from the wound. In addition, the superabsorbent material can absorb and retain a large quantity of exudate, thereby reducing the required frequency of dressing changes, and increasing the comfort of the patient.

Preferably, the arrangement of the wound dressing is such that wound exudate passes through the layer of carbon cloth before being absorbed by the superabsorbent material. For example, the carbon cloth may be positioned below (ie closer to the wound than) the superabsorbent material, such that wound exudate is drawn through the carbon cloth before passing into the superabsorbent material, enabling the carbon cloth to adsorb and retain bacteria from the wound exudate before the exudate is absorbed by the superabsorbent material.

Activated carbon, also known as activated charcoal, is a form of graphite which has a highly porous, random structure, most commonly formed through heat treatment of a carbon-containing material. The porosity of the charcoal gives it a large surface area enabling it to adsorb a wide range of compounds, and activated carbon has the strongest physical adsorption forces of any known material. This makes it particularly suited for use in a wound dressing, where it is important that bacteria and odour-causing molecules adsorbed onto the surface are retained, and not released back into the wound environment.

Activated carbon can be made from any substance which has a high carbon content, such as coal, cellulose, coconut shells etc, and the nature of the raw material impacts the properties of the activated carbon. It has long been known for use as an antidote to the ingestion of toxic substances, as it can adsorb toxic substances from the GI tract but is not itself digestible. However, granulated or powdered carbon can be difficult to use in wound dressings due to the need to retain it in place and the risk of particulate matter entering the wound.

Activated carbon fabric is activated charcoal in a flexible, microporous fabric form.

It is produced by carbonising a suitable cellulose fabric by heating it under carefully controlled conditions. During this process, the surface of the carbon breaks down to form small pores. The pores provide the dual benefit of greatly increased surface area (eg around 1000-2000 m2/g), which increases the ability of the cloth to adsorb odour-causing molecules, and facilitating the absorption of wound exudate. Activated carbon cloth is commercially available. Any suitable activated carbon cloth may be used in the present invention, and may contain from 95-100% activated carbon, or from 98-100% activated carbon, or 100% activated carbon. Most preferably, the activated carbon cloth is 100% activated carbon. A particularly preferred activated carbon cloth is sold under the tradename Zorflex®.

The activated carbon cloth used in the present invention may be woven, knitted or nonwoven. Preferably, the activated carbon cloth is knitted. The knitting process produces a stretchable, elastic fabric which easily moves with and conforms to the patient, and which does not shed or fray thus reducing the risk of particulate matter entering the wound.

The superabsorbent material is typically positioned directly above the carbon cloth layer, and is bonded to, or held in intimate contact with, the carbon cloth.

Alternatively, an additional layer, eg an absorbent layer, may be positioned between the superabsorbent material and the carbon cloth.

The positioning of the superabsorbent material above the carbon cloth prevents the superabsorbent material from coming into direct contact with the wound, and thus reduces or eliminates the risk of particles of superabsorbent material being transferred into the wound.

In some embodiments, the layer of carbon cloth forms the wound contact layer. In such embodiments, the carbon cloth may be bonded on its upper (ie non-wound-facing) side to an additional support layer. The support layer may be any suitable material known in the art which enhances the structural stability of the carbon cloth whilst permitting the passage of wound exudate. A particularly preferred support layer is a non-woven fabric, in particular a non-woven blend of polyester and viscose, preferably perforated across its whole extent. The perforations are of a size to permit the passage of wound exudate, and are typically between about 0.1mm and 3mm, or about 0.5mm and 2mm, most preferably about 1mm.

Lamination of the carbon cloth to the support layer may be brought about by any suitable means, provided that the passage of wound exudate into the superabsorbent material is not significantly inhibited or impaired.

In order to laminate the carbon cloth to the support layer, one or both of the juxtaposed surfaces of those components may be coated with a suitable adhesive, and the two components then pressed together.

More preferably, however, the two components are laminated using a fusible web material. Such materials are typically of synthetic fibres that melt when heated.

When the fusible web is placed between the carbon cloth and the support layer and heated, the melting action of the web causes it to fuse the carbon cloth and the support layer together.

In some embodiments of the invention, the carbon cloth is located in the interior of the dressing, thereby greatly reducing or eliminating the risk of particles of carbon being released into the wound. The carbon cloth may be bonded to a wound contact layer or to the superabsorbent material eg in the manner described above.

Alternatively, the carbon cloth may be incorporated into the dressing as a loose component (eg retained within a pocket), or the edges of the carbon cloth may be encapsulated within the structure of the dressing (eg captured between a backing layer and a wound contact layer).

"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 wound dressing 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.

Alginate superabsorbent may be sodium or calcium alginate. The alginate superabsorbent is preferably in the form of a non-woven mat, providing a superabsorbent layer suitable for the method of the present invention.

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 carrier material, such as tissue paper. A specific example of a suitable material is Gelok® 14040S/S manufactured by Gelok International Corporation.

The superabsorbent material may be present in combination with another layer of absorbent material. For example, the superabsorbent material may be bonded on its lower side to a layer of polyurethane foam, or a nonwoven alginate, or other absorbent body. Where such a layer of absorbent material is present, the carbon cloth may be separated from the layer of superabsorbent material by the layer of absorbent material.

Where present, the absorbent material may be any suitable material known in the art, and may comprise a foam, a gelling material, or a combination of these components.

The foam may be any suitable foam known in the art. Usually, the foam is an open-celled foam. Preferably, the foam is a hydrophilic 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 Sg/g, or at least 1 Og/g, or at least 15g/g, or at least 25g/g.

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 polysaccharide 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.

Additional agents known to assist or enhance wound healing may also be incorporated into the wound dressing. For example, the dressing may also include antimicrobial agents, antiseptic agents, antifungal agents and/or anti-inflammatory agents, and such agents may be incorporated either into the carbon cloth, into the superabsorbent material, or into the additional absorbent material (if present).

The wound dressing of the present invention may comprise silver. Despite metallic silver being relatively unreactive, ionic silver has been shown to have antimicrobial activity and has been previously used in wound dressings. In use, positively charged silver ions bind to negatively charged sites on proteins and nucleic acids in bacteria. This causes a number of effects, including alteration of the protein structure, rupture of the cell wall and/or cell death. It is believed that silver ions have multiple attack sites, interacting with a number of different functional groups in bacteria, including thiol groups, carboxylates, phosphates, indoles and amines. This makes the development of bacterial resistance to silver unusual.

It is preferable that the incorporation of silver into the wound dressing results in the sustained release of low concentrations of silver ions over time. Such a slow release has been shown to stimulate healing and inhibit the growth of micro-organisms. Methods for incorporating silver into wound dressings are known in the art, as is the form in which silver may be used. Any suitable method or form known in the art may be used in the present invention. For example, the silver may be in the form of silver sulphadiazine. It has been found that the use of silver in combination with carbon cloth is particularly effective, as the carbon cloth draws in and traps bacteria, which are then killed by the silver.

Another antimicrobial that may be incorporated into the wound dressing of to the invention is polyhexamethylene biguanide (PHMB; also known as polyaminopropyl biguanide). PHMB is available as a 20% aqueous solution under the trade name COSMOCIL® CO from Arch Personal Care Products, 70 Tyler Place, South

Plainfield, NJ 07080, USA.

The concentration of antimicrobial agent such as silver or PHMB in the dressing according to the invention may vary between quite wide limits.

The wound dressing of the present invention may comprise honey. Honey has long been known to be effective in treating wounds, with records of such use dating from at least 2000 years ago. More recently, research has shown it to have potent antimicrobial, antifungal and anti-inflammatory properties, and to be able to stimulate lymphocytic and phagocytic activity within the body. Further, honey has been demonstrated to assist in the debridement of necrotic tissue, and to stimulate the growth of new tissue. In terms of its antibacterial activity, honey has been reported to have an antibacterial effect on more than 60 species of bacteria, including aerobes, anaerobes, Gram-positive and Gram-negative bacteria. In particular, honey has been shown to be effective against antibiotic resistant strains of bacteria including MRSA.

Without wishing to be bound by theory, it is believed that the antibacterial activity of honey is partly due to the release of low levels of hydrogen peroxide, a well known antimicrobial agent. As the production of hydrogen peroxide is stimulated by dilution of the honey (eq by wound exudate), honey has the distinctive property of becoming more active on dilution, rather than less.

Many studies have shown that the maintenance of a moist wound environment aids in wound healing. However, a moist environment also promotes the growth of bacteria, and the prevention of infection is therefore a serious concern. The addition of honey to a wound dressing enables the wound to be kept moist whilst inhibiting bacterial growth and reducing the likelihood of infection.

In the present invention, the wound dressing may be supplied impregnated with honey, either in the superabsorbent material, the additional absorbent material (where present) or in the carbon cloth layer, or with honey on the surface of the wound dressing. Alternatively, honey may be applied to the dressing or directly to the wound prior to application of the dressing. Preferably, honey is impregnated into the superabsorbent material or additional absorbent material (where present).

Honey is produced worldwide from many different floral sources, and its antibacterial activity varies with the source of the honey and the processing it has undergone. For example, lotus honey in India is reputed to be good for eye diseases, whereas manuka honey, a monofloral honey produced from pollen from the manuka bush, is known for its antiseptic properties. The manuka plant is part of the genus Jeptospermum, and honeys produced from plants of this genus, such as manuka or jelly bush honey, are known for their particularly strong anti-bacterial properties. Preferably, the honey used in the present invention is produced from plants of the genus leptospermum. More preferably, the honey is manuka honey or jelly bush honey.

The wound dressing may further comprise a backing layer, which forms a barrier between the wound and the surrounding atmosphere, and any suitable material known in the art may be used for the backing layer.

The backing layer will generally be impermeable to wound exudate and other liquids, 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 backing layer may be at least 300g/m2/24h, more suitably at least 500g/m2/24h and preferably at least 700g/m2/24h at 37°C and 100% to 10% relative humidity difference.

The backing layer is most preferably a plastics film having the desired characteristics. The backing layer may be a polyurethane film.

The backing layer may be larger in size than the carbon cloth, such that it extends beyond the edge of the carbon cloth on one or more sides. Preferably, the backing layer extends beyond the edge of the carbon cloth on all sides, forming a border around the carbon cloth.

The wound dressing of the invention may further comprise a wound contact layer.

The wound contact layer may be non-woven, knitted or woven, and may be formed of or coated in a material which adheres to the skin, whilst still permitting easy removal of the wound dressing without damage to the wound or surrounding skin.

The surface of the wound contact layer that, in use, is applied to the wound and pen-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 itself, 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 hydrocolloid adhesive, a polyurethane adhesive, a hydrogel or, most preferably, a silicone adhesive, particularly a silicone gel.

Silicone 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 si Ii cone".

Soft silicone adhesives are particularly suited for use as skin contact layers in wound dressings. They are soft, tactile and conformable, 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.

Silicone gels suitable for use as skin contact materials in the present invention may be carried on a layer of melt-blown 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 a carbon cloth and/or a backing layer, such as a breathable film of plastics material, for instance polyurethane.

Alternatively, the wound contact layer may comprise gelling fibres. Gelling fibres allow the dressing to be non-adherent and enable atraumatic removal of the dressing, as well as helping to absorb wound exudate.

The gelling fibres may be any suitable gelling fibre known in the art, including pectin fibres, alginate fibres, fibres made from alginate and another polysaccbaride, chitosan fibres, hyaluronic acid fibres, fibres of other polysaccharides or derived from gums, or chemically-modified cellulosic fibres, eg carboxymethyl cellulose (CMC). The gelling fibres may be a combination or blend of different gelling fibres. Currently preferred gelling fibres are alginate fibres and pectin fibres.

The wound contact layer may comprise only gelling fibres. However, at least where the wound contact layer is woven or knitted, it is preferred that it comprises a blend of gelling fibres and non-gelling fibres. Preferably the material comprises at least 50% w/w gelling fibres. The material may be formed from a mixture of yarns of gelling fibre and yarns of non-gelling fibre. More preferably, however, the material is formed, most preferably knitted, from a single yarn that is a blend of gelling and non-gelling fibres. Suitable yarns include those disclosed in International Patent Application W0201 3/064831.

The combination of gelling and non-gelling fibre in such blended yarns produces a strong, flexible yarn, even where there is a relatively low proportion of non-gelling fibre.

The non-gelling fibres may be any suitable fibres known in the art, or may be a mixture of two or more non-gelling fibres. The non-gelling fibres may be textile fibres, and may be natural, eg cotton, may be natural fibres which have been modified eg cellulosic fibres such as viscose or lyocell (sold under the tradename TENCEL©), or they may be synthetic, eg polyester, polypropylene or polyamide, or a combination. Preferably, the non-gelling fibres are natural fibres which have been modified. More preferably, the non-gelling fibres are cellulosic fibres.

Thus, in some embodiments, the wound contact layer may comprise a combination of alginate fibres and cellulosic fibres, or a combination of pectin fibres and cellulosic fibres.

The wound contact layer may be a perforated wound contact layer. The perforations in the wound contact layer allow the transfer of wound exudate through the contact layer, and into the carbon cloth and superabsorbent material.

The perforations are typically circular, and have a diameter of from 0.5mm to 20mm, preferably 2mm to 20mm, preferably 3mm to 10mm, or 4mm to 7mm, and most preferably about 5mm.

The wound contact layer may alternatively be a non-woven material. For example, the wound contact layer may be a non-woven blend of polyester and viscose, preferably perforated across its whole extent. Where the wound contact layer is a perforated non-woven material, the perforations will typically be smaller than those described above, and are typically between about 0.1mm and 3mm, or about 0.5mm and 2mm, most preferably about 1mm.

Where the skin contact layer of the dressing carries an adhesive, 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 be 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. In 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 wound dressing according to the invention may be used alone or in conjunction with a secondary dressing. It may be affixed to the patient by means of an adhesive eg a soft silicone adhesive as described above, or may be fixed to the patient by other suitable means, such as tape or a bandage.

Te 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 cross-sectional view of a first embodiment of a wound dressing according to the invention; Figure 2 is a cross-sectional view of a second embodiment of a wound dressing according to the invention; and Figure 3 is a cross sectional view of a third embodiment of the wound dressing according to the invention.

Referring first to Figure 1, there is shown a wound dressing 1 according to the invention. The dressing 1 is generally square in form and comprises a backing layer of microporous, liquid impermeable, gas-and vapour-permeable polyurethane film 11, below which is located a layer of superabsorbent material 12, a support layer 13 and a layer of activated carbon cloth 14 which forms the wound contact layer.

The layer of superabsorbent material 12 comprises particles of sodium polyacrylate polymer encapsulated between two layers of tissue paper carrier material.

The support layer 13 is formed of a non-woven blend of polyester and viscose, perforated across its whole extent with perforations of approximate size 1mm.

The support layer 13 and carbon cloth 14 are laminated together using a fusible web material of synthetic fibres which melt when heated. When the fusible web is placed between the carbon cloth and the support layer and heated, the melting action of the web causes it to fuse the carbon cloth and the support layer together.

The carbon cloth/support layer laminate 13 14 and the backing layer 11 have the same overall shape and dimensions, and are superimposed on top of one another and bonded at the perimeter of the dressing 15. This forms a pocket 16 in the interior of the dressing, which holds the superabsorbent material 12.

When the dressing 1 is applied to a wound, wound exudate is drawn by the superabsorbent material 12 through the carbon cloth 14 and support layer 13. The carbon cloth 14 adsorbs bacteria and odour-causing molecules, while the superabsorbent material 12 may absorb many times, eg several hundred times, its own weight in wound exudate. The backing sheet 11 is impermeable to fluid and permeable to vapour, so that wound exudate is retained within the dressing 1 whilst vapour is allowed to escape.

Figure 2 shows an alternative embodiment of a wound dressing of the invention, generally designated 2. The wound dressing 2 comprises a backing layer of microporous, liquid impermeable, gas-and vapour-permeable polyurethane film 21, below which is located a layer of superabsorbent material 22, a layer of carbon cloth 23 and a wound contact layer 24.

The wound contact layer 24 is formed of a non-woven blend of polyester and viscose, perforated across its whole extent with perforations of approximate size 1mm.

In one embodiment, the wound contact layer 24 and carbon cloth 23 are laminated together using a fusible web material of synthetic fibres which melt when heated.

When the fusible web is placed between the carbon cloth and the support layer and heated, the melting action of the web causes it to fuse the carbon cloth and the support layer together. In such cases, the carbon cloth 23 may extend across the full area of the wound contact layer 24.

In alternative embodiments, the carbon cloth is enclosed in the pocket as a loose component, or is bonded to the underside of the superabsorbent material 22 using a fusible web as described above.

When the dressing 2 is applied to a wound, wound exudate passes through the wound contact layer 24, through the carbon cloth 23 and into the superabsorbent material 22.

The wound contact layer 24 and the backing layer 21 have the same overall shape and dimensions, and are superimposed on top of one another and bonded at the perimeter of the dressing 25. This forms a pocket 26 in the interior of the dressing, which holds the superabsorbent material 22.

Wound exudate is drawn by the superabsorbent material 22 through the wound contact layer 24 and carbon cloth 23. The carbon cloth 23 adsorbs bacteria and odour-causing molecules, while the superabsorbent material 22 may absorb many times, eg several hundred times, its own weight in wound exudate. The backing sheet 21 is impermeable to fluid and permeable to vapour, so that wound exudate is retained within the dressing 2 whilst vapour is allowed to escape.

Figure 3 shows a third embodiment of a wound dressing of the invention, generally designated 3. The wound dressing 3 comprises a backing layer of microporous, liquid impermeable, gas-and vapour-permeable polyethylene film 31, below which is located a layer of superabsorbent material 32, a layer of carbon cloth 33 and a The wound dressing 3 is substantially the same as the wound dressing 2 described above (see Figure 2), except that the carbon cloth 33 is retained in the wound dressing 3 by trapping of the edges of the carbon cloth 33 between the backing layer 31 and the wound contact layer 34, where those components are bonded together about the perimeter of the dressing 35.

Claims

Claims 1. A composite wound dressing comprising a superabsorbent material and a layer of activated carbon cloth.
2. The composite wound dressing of Claim 1, which is arranged such that wound exudate passes through the layer of carbon cloth before being absorbed by the superabsorbent material.
3. The composite wound dressing of Claim 1 or Claim 2, wherein the activated carbon cloth contains 95-100% activated carbon.
4. The composite wound dressing of Claim 3, wherein the activated carbon cloth contains 98-100% activated carbon.
5. The composite wound dressing of any preceding claim, wherein the activated carbon cloth is knitted.
6. The composite wound dressing of any preceding claim, wherein the superabsorbent material is positioned directly above the carbon cloth layer, and is bonded to, or held in intimate contact with, the carbon cloth.
7. The composite wound dressing of any of Claims 1 to 5 which further comprises an absorbent body interposed between the superabsorbent material and the carbon cloth.
8. The composite wound dressing of any preceding claim, wherein the carbon cloth forms the wound contact layer.
9. The composite wound dressing of Claim 8, wherein the carbon cloth is bonded on its upper side to a support layer.
10. The composite wound dressing of Claim 9, wherein the support layer is a non-woven fabric, in particular a perforated, non-woven blend of polyester and viscose.
11. The composite wound dressing of Claim 10, wherein the perforations have a diameter of from 0.1mm to 3mm.
12. The composite wound dressing of any of Claims 9 to 11, wherein the carbon cloth is laminated to the support layer using a fusible web.
13. The composite wound dressing of any of Claims 1 to 7, wherein the carbon cloth is located in the interior of the dressing.
14. The composite wound dressing of Claim 13, which further comprises a wound contact layer.
15. The composite wound dressing of Claim 14, wherein the wound contact layer is a non-woven fabric, in particular a perforated, non-woven blend of polyester and viscose.
16. The composite wound dressing of Claim 14, wherein the wound contact layer is an MBPU film coated on the wound facing side with a silicone gel.
17. The composite wound dressing of any of Claims 13 to 16, wherein the carbon cloth is bonded to the superabsorbent material.
18. The composite wound dressing of any of Claims 13 to 17, wherein the carbon cloth is bonded to the wound contact layer.
19. The composite wound dressing of any preceding claim, wherein the superabsorbent material is a polymeric superabsorbent material.
20. The composite wound dressing of Claim 19, wherein the superabsorbent material is selected from the group consisting of alginate, polyacrylate, polyacrylamide copolymers, ethylene maleic anhydride copolymer, carboxymethylcellulose, polyvinylalcohol copolymers, polyethylene oxide and starch-grafted copolymers of polyacrylonitrile.
21. The composite wound dressing of Claim 20, wherein the superabsorbent material is a sodium polyacrylate polymer.
22. The composite wound dressing of any preceding claim, wherein the superabsorbent material is in particulate form.
23. The composite wound dressing of Claim 22, wherein the particles of superabsorbent material are encapsulated between two layers of carrier material.
24. The composite wound dressing of any preceding claim, which further comprises an antimicrobial agent, antiseptic agent, antifungal agent and/or an anti-inflammatory agent.
25. The composite wound dressing of Claim 24, which comprises silver, PHMB and/or honey.
26. The composite wound dressing of any preceding claim, which further comprises a backing layer.
27. The composite wound dressing of Claim 26, wherein the backing layer is a polyurethane film.
28. The composite wound dressing of Claim 26 or Claim 27, wherein the backing layer extends beyond the edge of the carbon cloth on all sides, forming a border around the carbon cloth.
29. The composite wound dressing of any preceding claim, which further comprises a releasable liner.
30. A composite wound dressing, substantially as described herein and as depicted in Figure 1.
31. A composite wound dressing, substantially as described herein and as depicted in Figure 2.
32. A composite wound dressing, substantially as described herein and as depicted in Figure 3.