WOUND DRESSING

Abstract

A negative pressure wound dressing comprising a backing layer, an adhesive skin contact layer and an absorbent structure arranged between the backing layer and the adhesive skin contact layer, wherein the adhesive skin contact layer is configured to detachably adhere the dressing to a dermal surface, wherein the backing layer comprises a coupling member configured to connect the dressing to a negative pressure source, wherein the absorbent structure comprises a wound contact layer arranged to contact the wound when the adhesive skin contact layer is adhered to the skin adjacent the wound, and the wound contact layer may have a first surface and a second surface, wherein the first surface of the wound contact layer may contact the wound in use, wherein the first surface may comprise warp stitches, and the second surface may comprise warp and weft stitches.

Claims

1. A negative pressure wound dressing comprising a backing layer, an adhesive skin contact layer and an absorbent structure arranged between the backing layer and the adhesive skin contact layer, wherein the adhesive skin contact layer is configured to detachably adhere the dressing to a dermal surface, wherein the backing layer comprises a coupling member configured to connect the dressing to a negative pressure source, wherein the absorbent structure comprises a wound contact layer arranged to contact the wound when the adhesive skin contact layer is adhered to the skin adjacent the wound, the wound contact layer having a first surface and a second surface, wherein the first surface of the wound contact layer contacts the wound in use, wherein the first surface comprises warp stitches, and characterised in that the second surface comprises warp and weft stitches.

2. A negative pressure wound dressing according to claim 1, wherein the first surface does not comprise any weft stitches.

3. A negative pressure wound dressing according to claim 1 or 2, wherein the second surface comprises at least 1.0 weft stitches/cm.

4. A negative pressure wound dressing according to any of claims 1 to 3, wherein the second surface comprises at least 4.0 weft stitches/cm.

5. A negative pressure wound dressing according to any of claims 1 to 4, wherein the second surface comprises about 7.5 weft stitches/cm.

6. A negative pressure wound dressing according to claim 1, wherein the second surface comprises fewer than 1.0 weft stitches/cm.

7. A negative pressure wound dressing according to any preceding claim, wherein the wound contact layer has a weight of between 40 gsm and 250 gsm.

8. A negative pressure wound dressing according to claim 7, wherein the wound contact layer has a weight of between 60 gsm and 200 gsm.

9. A negative pressure wound dressing according to any preceding claim, wherein the wound contact layer has a weight of between 80 gsm and 120 gsm.

10. A negative pressure wound dressing according to claim 9, wherein the wound contact layer has a weight of 100 gsm.

11. A negative pressure wound dressing according to any preceding claim, wherein the warp stitches comprised in the first surface and/or the second surface have a pitch of between 1.0 mm and 30.0 mm.

12. A negative pressure wound dressing according to claim 11, wherein the warp stitches comprised in the first surface and/or the second surface have a pitch of between 6.0 mm and 7.0 mm.

13. A negative pressure wound dressing according to claim 11 or 12, wherein the warp stitches comprised in the first surface and/or the second surface have a pitch of 6.6 mm.

14. A negative pressure wound dressing according to any preceding claim, wherein the wound contact layer comprises sodium carboxymethylcellulose fibres.

15. A negative pressure wound dressing according to claim 14, wherein the sodium carboxymethylcellulose fibres have a degree of substitution of between 0.25 carboxymethyl groups per glucose unit and 0.35 carboxymethyl groups per glucose unit.

16. A negative pressure wound dressing according to claim 15, wherein the sodium carboxymethylcellulose fibres have a degree of substitution of 0.30 carboxymethyl groups per glucose unit.

17. A negative pressure wound dressing according to any preceding claim, wherein the wound contact layer is stitched using lyocell yarn.

18. A negative pressure wound dressing according to any preceding claim, wherein the wound contact layer comprises multiple layers bonded together by stitch bonding or lamination.

19. A negative pressure wound dressing according to claim 18, wherein the multiple layers comprise a first layer and a second layer, wherein a first surface of the first layer contacts the wound in use, further wherein the first surface of the first layer does not comprise any weft stitches.

20. A negative pressure wound dressing according to claim 19, wherein the second layer comprises a first surface and a second surface, the first surface of the second layer being arranged opposite a second surface of the first layer, and further wherein the second surface of the first layer, and the first and second surfaces of the second layer, comprise weft stitches.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0723] In order that the invention may be more clearly understood one or more embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which:

[0724] FIG. 1 is an example embodiment of part of an adhesive skin contact layer for use with a negative pressure wound dressing;

[0725] FIG. 2 is an expanded view of section A of FIG. 1;

[0726] FIG. 3 is an exploded view of a first embodiment of a negative pressure wound dressing;

[0727] FIG. 4 is a plan view of a further example embodiment of a negative pressure wound dressing;

[0728] FIG. 5 is an exploded view of the negative pressure wound dressing of FIG. 4;

[0729] FIG. 6 is a plan view of an example embodiment of a backing layer for use with the embodiment shown in FIG. 4;

[0730] FIG. 7 is a perspective view of the example backing layer shown in FIG. 6;

[0731] FIG. 8 is a plan view of an example embodiment of an absorbent structure for use with the embodiment shown in FIG. 4;

[0732] FIG. 9 is a side view of the example absorbent structure shown in FIG. 8;

[0733] FIG. 10 is a rear view of the example absorbent structure shown in FIG. 8;

[0734] FIG. 11 is a cross-section view along line A-A shown in FIG. 8;

[0735] FIG. 12 is a perspective view of the example absorbent structure shown in FIG. 8;

[0736] FIG. 13 is a plan view of a lower surface of an example embodiment of an adhesive skin contact layer for use with the embodiment shown in FIG. 4;

[0737] FIG. 14 is a perspective view of the example adhesive skin contact layer shown in FIG. 13;

[0738] FIG. 15 is a further plan view of the example embodiment of the negative pressure wound dressing shown in FIG. 4;

[0739] FIG. 16 is a cross-section view along line B-B shown in FIG. 15;

[0740] FIG. 17 is a perspective view of the example embodiment of the negative pressure wound dressing shown in FIG. 4; and

[0741] FIG. 18 is a perspective view of an example embodiment of a release liner for use with the embodiment shown in FIG. 4.

[0742] With reference to FIGS. 1 and 2, there is shown an adhesive skin contact layer 2 for use with a negative pressure wound dressing.

[0743] The adhesive skin contact layer assists in securing the wound dressing to the skin of a patient, in particular to the peri-wound skin adjacent to a wound. The adhesive skin contact layer 2 may have a weight of 200 gsm which provides for a malleable, gelled structure so, in the event of an air leak, the layer can seal the leak more easily than if the layer had a weight below 100 gsm, in particular below 40 gsm. The adhesive skin contact layer 2 is a perforated mesh comprising a plurality of perforations 3 arranged in a plurality of rows. In the present embodiment, 95% of the perforations 3 are arranged in a triangle packed layout. The triangle packed layout comprises adjacent rows 3a, 3b of perforations 3. Row 3a is arranged offset from row 3b. The perforations 3 in row 3a are not arranged adjacent to the perforations 3 in the adjacent row 3b but instead the perforations 3 in row 3a are arranged adjacent to the gap between perforations 3 in row 3b or adjacent to part of the gap and part of a perforation 3 in row 3b.

[0744] Each perforation 3 comprises an opening, which in this embodiment is in the shape of a circle. In this embodiment, the size of each perforation 3 is defined by the diameter of the circle. However, the person skilled in the art will understand that the size of the opening may be defined depending on the shape of the opening. In some embodiments, the size of a circle is the diameter. In other embodiments, the size of an oval is the longer diameter. In further embodiments, the size of a hexagon is the longest diagonal; and the size of a triangle, a square, a rectangle, an octagon or any other polygon perforation may be the longest side. In the present embodiment, each perforation 3 has a diameter of 2.20 mm and are therefore of sufficient size to provide breathability to the wound dressing in the event that some of the perforations reduce in diameter after their formation, for example by the adhesive entering the opening of a perforation. As such, the adhesive skin contact layer maintains an environment optimised for wound healing. Moreover, each perforation 3 is a through hole in the adhesive skin contact layer 2 which can enable fluid to flow through the layer 2. The adhesive skin contact layer 2, therefore, helps to prevent tissue ingrowth into the other material of the wound dressing.

[0745] The perforations 3 have a pitch (i.e., the distance between the centre point of a perforation and the centre point of an adjacent perforation) in a first direction (shown as A in FIG. 2) of 8.0 mm, and a pitch in a second direction (shown as B in FIG. 2) of 5.6 mm. Advantageously, the pitch of the perforations 3 has a ratio of perforation:no-perforation which provides efficient moisture evaporation, prevents pooling and strongly adheres to the peri-wound skin of the patient. Surprisingly, and advantageously, tests have shown that the adhesive skin contact layer 2 remains adhered to a patient for at least seven days.

[0746] The total area of the perforations 3 may be 2100 mm.sup.2 and the total volume of the perforations may be 2100 mm.sup.3. The degree of perforation may be 10.66% of the area of the adhesive skin contact layer 2. The perforations 3 are distributed evenly throughout the adhesive skin contact layer 2. The perforations 3 may be formed by a mechanical punch perforating process which does not result in the formation of a doughnut or volcano structure around the perforations after formation of the perforations 3. The perforations may be formed by mechanical punch perforating the adhesive skin contact layer 2 comprising a release liner (not shown) covering at least one surface of the adhesive skin contact layer 2.

[0747] The adhesive skin contact layer 2 has a thickness of 1.0 mm and a width and length (measured from the periphery of the adhesive skin contact layer 2) each of 130 mm. The adhesive skin contact layer 2 has an outer periphery in the shape of a square. The adhesive skin contact layer 2 comprises an upper surface 2a and a lower surface 2b. The lower surface 2b contacts the dermal surface in use.

[0748] With reference to FIG. 3, there is shown a negative pressure wound dressing 1.

[0749] The wound dressing 1 comprises an adhesive skin contact layer 20 (which is preferably the adhesive skin contact layer 2 described with reference to FIGS. 1 and 2), a wound contact layer 4, a transmission layer 5, a superabsorbent layer 6, a backing layer 7 and an airway 8.

[0750] The adhesive skin contact layer 20 may have a perimetral shape with a central window 9, therefore, the adhesive skin contact layer 20 may bean adhesive skin contact border layer 20. The border layer 20 may comprise an outer periphery which defines the outer shape of the border layer 20, which, in this embodiment, is a square. The border layer 20 may comprise an inner periphery which defines the shape of the window 9. The window 9 may be of the same, or similar shape, to that of the outer periphery of the border layer 20.

[0751] The window 9 is a square through hole in the adhesive skin contact layer 20. The window 9 is located centrally relative to the periphery of the adhesive skin contact layer 20. Each side of the window 9 is arranged parallel to each of the corresponding sides of the adhesive skin contact layer 20. The window may have an area of 12,500 mm2. The skilled person will appreciate that the window 9 may be enlarged by any suitable means, for example by cutting the adhesive skin contact layer 20. The window 9 in the adhesive skin contact layer 20 enables the wound of a patient to contact, or be in fluid communication with, other layers of the wound dressing 1, for example the wound contact layer 4, when the wound dressing 1 is applied to the skin of a patient.

[0752] The adhesive skin contact layer 20 comprises an upper surface 20b and a lower surface 20a. The lower surface 20a contacts the dermal surface in use. In use, the lower surface 20a of the adhesive skin contact layer 20 is detachably adhered to a dermal surface (not shown) of a patient such that the wound site (not shown) is located within the window 9. As such, the adhesive skin contact layer 20 is not in direct contact with the wound site but does wholly surround it. Thus, the adhesive skin contact layer 20 is in contact with intact peri-wound skin only. The upper surface 20b may be outwardly facing away from the patient's body.

[0753] A removable cover or release layer (not shown) may be adhered to the lower surface 20a of the adhesive skin contact layer 20. The removable cover, which may comprise folded grip sections, is removable from the lower surface 20a of the adhesive skin contact layer 20. Thus, the removable cover protects the adhesive skin contact layer 20 when the removable cover is adhered to the adhesive skin contact layer 20, but when the removable cover is removed from the lower surface 20a of the adhesive skin contact layer 20 for use of the wound dressing 1, the lower surface 20a is exposed and able to releasably secure the wound dressing 1 to the skin of a patient.

[0754] The wound contact layer 4, the transmission layer 5 and the superabsorbent layer 6 form an absorbent structure arranged between the adhesive skin contact layer 20 and the backing layer 7.

[0755] The backing layer 7 may comprise a first surface 7a and a second surface 7b. In use, the first surface 7a may be inwardly facing toward the patient's body, and the second surface 7b may be outwardly facing away from the patient's body.

[0756] The absorbent structure 4, 5, 6 may comprise a first surface 4a and a second surface 6b. The first surface 4a of the absorbent structure 4, 5, 6 may be adjacent, and in contact with, the upper surface 20b of the adhesive skin contact layer 20. The peripheral edge of the second surface 6b of the absorbent structure 4, 5, 6 may be adjacent, and in contact with, the first surface 7a of the backing layer 7.

[0757] The wound contact layer 4 may comprise a first surface 4a and a second surface 4b. In use, the first surface 4a may be inwardly facing toward the patient's body, and the second surface 4b may be outwardly facing away from the patient's body. The first surface 4a of the wound contact layer 4 may contact the wound when the wound dressing 1 is adhered to the skin adjacent to the wound (i.e., when in use). The first surface 4a of the wound contact layer 4 is substantially aligned with the window 9 of the adhesive skin contact layer 20. As such, in use, the first surface 4a contacts the wound through the window 9. The second surface 4b of the wound contact layer 4 may be adjacent, and in contact with, a first surface 5a of the transmission layer 5 or a first surface 6a of the superabsorbent layer 6. In the described embodiment, the second surface 4b of the wound contact layer 4 is adjacent, and in contact with, the first surface 5a of the transmission layer 5.

[0758] The transmission layer 5 may comprise a first surface 5a and a second surface 5b. In use, the first surface 5a may be inwardly facing toward the patient's body, and the second surface 5b may be outwardly facing away from the patient's body. The first surface 5a of the transmission layer 5 may be adjacent, and in contact with, the second surface 4b of the wound contact layer 4 or a second surface 6b of the superabsorbent layer 6. The second surface 5b of the transmission layer 5 may be adjacent, and in contact with, a first surface 6a of the superabsorbent layer 6 or the first surface 7a of the backing layer 7. In the described embodiment, the first surface 5a of the transmission layer 5 is adjacent, and in contact with, the second surface 4b of the wound contact layer, and the second surface 5b of the transmission layer 5 is adjacent, and in contact with, the first surface 6a of the superabsorbent layer 6.

[0759] The superabsorbent layer 6 may comprise a first surface 6a and a second surface 6b. In use, the first surface 6a may be inwardly facing toward the patient's body, and the second surface 6b may be outwardly facing away from the patient's body. The first surface 6a of the superabsorbent layer 6 may be adjacent, and in contact with, the second surface 4b of the wound contact layer 4 or the second surface 5b of the transmission layer 5. The second surface 6b of the superabsorbent layer 6 may be adjacent, and in contact with, the first surface 5a of the transmission layer 5 or the first surface 7a of the backing layer 7. In the described embodiment, the first surface 6a of the superabsorbent layer 6 is adjacent, and in contact with, the second surface 5b of the transmission layer 5, and the second surface 6b of the superabsorbent layer 6 is adjacent, and in contact with, the first surface 7a of the backing layer 7.

[0760] The adhesive skin contact layer 20 may radially overlap the absorbent structure 4, 5, 6. The adhesive skin contact layer 20 may comprise an interior portion adjacent to and surrounding the window 9, and an exterior portion radially outwardly from the interior portion. The interior portion and the exterior portion of the first surface 20a of the adhesive skin contact layer 20 may contact and adhere to the skin of a patient in use. The interior portion of the second surface 20b of the adhesive skin contact layer may be adjacent, and in contact with, a portion of the first surface 4a of the wound contact layer 4. The exterior portion of the second surface 20b of the adhesive skin contact layer 20 may be adjacent, and joined with, a peripheral portion of the first surface 7a of the backing layer 7. Beneficially, this helps to prevent wound exudate escaping from the confines of the wound dressing which would be unhygienic and cause discomfort for the user. Moreover, this also helps maintain a negative pressure at the wound site.

[0761] The exterior portion of the second surface 20b of the adhesive skin contact layer 20 may be joined to the peripheral portion of the first surface 7a of the backing layer 7 by heat lamination, adhesive, welding or stitching.

[0762] The exterior portion of the second surface 20b of the adhesive skin contact layer 20 may extend radially beyond the periphery of the absorbent structure by about 27.5 mm.

[0763] At least two of the wound contact layer 4, the transmission layer 5 and the superabsorbent layer 6 may be laminated together. In the described embodiment, each of the wound contact layer 4, the transmission layer 5 and the superabsorbent layer 6 are laminated together. Advantageously, this means that the absorbent structure of the present invention is manufactured without requiring any relatively rigid dressing and binding components. Thus, the present invention provides an absorbent structure which is flexible, therefore benefits user comfort, and which is cheaper to manufacture than absorbent structures and, therefore negative pressure wound dressings, of the prior art. Moreover, lamination does not require any complex equipment or manufacturing techniques. Thus, the present invention is simple to manufacture.

[0764] Each of the wound contact layer 4, the transmission layer 5 and the superabsorbent layer 6 may be laminated together by a scatter-coat adhesive. The scatter-coat adhesive may be a hot melt, scatter-coat adhesive. In the described embodiment, the scatter-coat adhesive is polycaprolactone and has the following properties: [0765] a melt flow index of between 5.2 g/10 min and 11.3 g/10 min, as tested with 2.16 kg, 1 PVC die at 160 C.; [0766] a maximum water content of 0.35%; [0767] a mean molecular weight of 50,000; [0768] a melting point of 60 C.; and [0769] a solubility parameter of 9.34 cal/cm3 to 9.43 cal/cm3.

[0770] The scatter-coat adhesive may comprise particles of which at least 98% have a particle size of 0.6 mm.

[0771] The wound contact layer 4, the transmission layer 5 and the superabsorbent layer 6 may be laminated together by a laminator having the following processing properties: [0772] Heating zone temperature of 125 C.; [0773] Cooling zone temperature of 25 C.; [0774] Web tension (for each unwind reel) of 125 N; [0775] Crush roller pressure of 1000 N; and [0776] Web speed of 10 m/min.

[0777] The wound contact layer 4 further comprises a central region 4c and a peripheral region 4d. The central region 4c is substantially square and is bordered on each side by the peripheral region 4d.

[0778] In the described embodiment, the first surface 4a, which contacts the wound in use, may comprise warp stitches (longitudinal to the plane of the wound contact layer 4) only, i.e., the first surface 4a does not comprise any weft stitches (transverse to the plane of the wound contact layer 4). Advantageously, this means that the amount of non-gelling fibres (which may include weft stitches) at the wound contact surface is minimised. Thus, there is a greater ratio of gelling fibres to non-gelling fibres at the wound contact surface in contact with the wound and, therefore, wound exudate. Thus, the absorption capacity of the wound contact layer is increased. As such, pooling of wound exudate at the wound site is prevented, or at least significantly reduced and an environment optimised for wound healing is maintained at the wound site.

[0779] The warp stitches of the first surface 4a may have a pitch of 6.6 mm and a stitch density of 7.5 stitches/cm.

[0780] The second surface 4b, which is laminated to the first surface 5a of the transmission layer 5, comprises warp stitches and weft stitches. Each of the warp stitches and the weft stitches of the second surface 4b have a pitch of 6.6 mm and a stitch density of 7.5 stitches/cm.

[0781] In other embodiments, the central region 4c of the first surface 4a may comprise warp stitches only and the peripheral region 4d of the first surface 4a may comprise warp and weft stitches.

[0782] The wound contact layer 4 may have a weight of 100 gsm and a thickness of 3.0 mm.

[0783] Between the first surface 4a and the second surface 4b, which are joined about their periphery, the wound contact layer 4 may comprise a plurality of gel-forming fibres which, upon the uptake of wound exudate, become moist, slippery or gelatinous. Specifically, in this embodiment, the gel-forming fibres are hygroscopic fibres which upon the uptake of wound exudate become gelatinous. The gel-forming fibres may be of the type which retain their structural integrity on absorption of exudate. In the present embodiment, the fibres are sodium carboxymethylcellulose fibres having a degree of substitution of 0.30 carboxymethyl groups per glucose unit, as measured by IR spectroscopy (as defined in WO00/01425). The absence of weft stitches at the first surface 4a means that a greater amount of gel-forming fibres, as described above, are exposed at the first surface and, therefore, in contact with the wound. As such, the wound contact layer is higher gelling, i.e., has a significantly greater absorbency capacity and is more retentive, than gel-forming fibres of the prior art. As such, the wound contact layer 4 absorbs a greater amount of wound exudate. Thus, pooling of wound exudate at the wound site is prevented, or at least significantly reduced.

[0784] The sodium carboxymethylcellulose fibres are made by carboxymethylating a non-woven cellulosic fabric having an absorbency of 18 g/g of Solution A (sodium/calcium chloride solution), as measured by the method described in BS EN 13726-1 (2002) Test methods for primary wound dressings, section 3.2 Free swell absorptive capacity. The carboxymethylation is performed by contacting the fabric with an alkali and a carboxymethylating agent such as chloroacetic acid in a combined alcohol and aqueous system. The cellulosic fabric comprises solely of cellulosic fibre and comprises continuous filament yarn.

[0785] The gel-forming fibres have an absorbency of 2 grams 0.9% saline solution per gram of fibre (as measured by the free swell method).

[0786] The wound contact layer 4 is stitched using lyocell yarn (produced under the trade name Tencel yarn).

[0787] The transmission layer 5 is substantially square, as is the wound contact layer 4 and the superabsorbent layer 6, and has a thickness of 1.8 mm and is made of a polyurethane foam. The transmission layer 5 may have a density of between 26 Kg/M.sup.3 and 28 Kg/M.sup.3 and a tensile strength of 150 kPa. The transmission layer 5 may have an elongation at break value of 300% and a cell count of between 17 and 26/cm. Moreover, the transmission layer 5 may have a 40% CLD hardness of between 2.5 and 4.5 kPa.

[0788] The superabsorbent layer 6 comprises an upper layer having the second surface 6b, and a lower layer having the first surface 6a. Between the upper layer and the lower layer, there is enclosed a first material comprising non-woven fibres, an absorbent material and a hot melt binder.

[0789] The hot melt binder may be present in an amount of 70 g/m.sup.2. The hot melt binder may be a copolymer and, in the described embodiment, may be ethylene-vinyl acetate (EVA). In manufacture of the superabsorbent layer, the superabsorbent layer may be heated to melt the hot melt binder and bind the non-woven fibres of the first material together. Advantageously, this prevents, or at least significantly limits, the amount of shedding of the fibres of the superabsorbent layer when in use. Thus, the presence of the hot melt binder in the superabsorbent layer significantly increases the strength of the layer, preventing dissociation of the absorbent structure.

[0790] The absorbent material may be a superabsorbent material, capable of absorbing wound exudate while allowing the passage of fluid through it. The superabsorbent material may be sodium polyacrylate and in the form of a powder which, advantageously, increases the surface area to volume ratio of the superabsorbent material, therefore enhancing the absorbent property of the material.

[0791] The non-woven fibres may be cellulose fibres. The cellulose non-woven fibres may be arranged as a cellulosic non-woven matrix of fibres and may be a support onto which the absorbent material may be incorporated, for example, in the described embodiment, the absorbent material is dispersed upon the cellulosic non-woven matrix. The absorbent material may be dispersed evenly, or substantially evenly, throughout or upon the non-woven fibres, for example the cellulosic non-woven matrix.

[0792] The upper layer and the lower layer of the superabsorbent layer 6 may each be a cellulosic fabric layer. The upper fabric layer and the lower fabric layer may be joined around their entire periphery to enclose the first material.

[0793] The superabsorbent layer 6 may comprise a plurality of fenestrations (not shown). Each of the plurality of fenestrations may be openings in the form of slits in the superabsorbent layer 6. Each fenestration may have a length equal to 80% of the length of the superabsorbent layer 6. Each of the upper layer and the lower layer may comprise a plurality of fenestrations. The fenestrations may be arranged in a direction planar to a longitudinal axis and transverse to a longitudinal axis of the superabsorbent layer 6. Advantageously, this arrangement aids in managing a flow of exudate through the superabsorbent layer 6 of the wound dressing 1. The fenestrations encourage or enable wound exudate to travel laterally on the superabsorbent layer 6, as opposed to axially, and assist in negative pressure transmission through the superabsorbent layer 6.

[0794] The superabsorbent layer 6 may have a basis weight of 460 g/m2, a thickness of 2.55 mm and a density of 0.255 g/cm3. Moreover, the superabsorbent layer 6 may have a tensile strength (dry) of 45 N/50 mm, an absorbent capacity of 25 g/g 10 min, and an absorbency under compression capacity of 0.85 g/cm2.

[0795] Each of the wound contact layer 4, transmission layer 5 and superabsorbent layer 6 are substantially planar.

[0796] In use, the wound dressing 1 forms part of a negative pressure wound exudate management system comprising the wound dressing 1 and further comprising a source of negative pressure (not shown) and a coupling member (for example, airway 8) for providing negative pressure to the wound dressing from an internal lumen of a conduit or tube (not shown) and through an opening (not shown) in the wound dressing. The source of negative pressure comprises a pump for generating negative pressure and the tube connects the pump and wound dressing 1 via the airway 8. In the present embodiment, the source of negative pressure may comprise a one-way valve (not shown) in-line between the pump and the wound dressing 1 to maintain a negative pressure within the wound dressing 1 when the pump is disconnected from the tube.

[0797] In use, the adhesive skin contact layer 20 is adhered to the intact peri-wound skin around a wound. The wound is located within the window 9 of the adhesive skin contact layer 20. The wound dressing 1 is connected to a source of negative pressure before or after application of the dressing to the wound. Upon leaving the wound, wound exudate contacts the first surface 4a of the wound contact layer 4 and wicks upwardly, away from the wound site, toward the transmission layer 5. The high gelling ability of the wound contact layer 4 facilitates absorption and retention of the wound exudate. Lamination of the wound contact layer 4, transmission layer 5 and superabsorbent layer 6 means each of these layers form a consolidated, absorbent and retentive structure. The wound exudate wicks from the upper surface 4b of the wound contact layer 4 to the transmission layer 5. Lateral movement of the exudate occurs in the transmission layer 5 to spread the wound exudate across the surface area of the dressing. The exudate then wicks upwardly to the superabsorbent layer 6 where it is absorbed and retained prior to being transmitted out of the dressing 1 via vapour transmission through the backing film 7.

[0798] With reference to FIGS. 4 to 18, there is shown a further example embodiment of a negative pressure wound dressing 10.

[0799] The wound dressing 10 comprises an adhesive skin contact layer 200 (which is preferably the adhesive skin contact layer 200 described with reference to FIGS. 13 and 14), a wound contact layer 40, a transmission layer 50, a superabsorbent layer 60, a backing layer 70 and an airway 80. The wound contact layer 40, transmission layer 50 and superabsorbent layer 60 together form an absorbent structure 11 arranged between the adhesive skin contact layer 200 and the backing layer 70.

[0800] The adhesive skin contact layer 200 assists in securing the wound dressing 10 to the skin of a patient, in particular to the peri-wound skin adjacent to a wound. The adhesive skin contact layer 200 may have a weight of 200 gsm which provides for a malleable, gelled structure so, in the event of an air leak, the layer can seal the leak more easily than if the layer had a weight below 100 gsm, in particular below 40 gsm.

[0801] With reference to FIGS. 13 and 14, the adhesive skin contact layer 200 may be a perforated mesh comprising a plurality of perforations 30 arranged in a plurality of rows. In the present embodiment, 95% of the perforations 30 are arranged in a triangle packed layout. The triangle packed layout comprises adjacent rows 30a, 30b of perforations 30. Row 30a is arranged offset from row 30b. The perforations 30 in row 30a are not arranged adjacent to the perforations 30 in the adjacent row 30b but instead the perforations 30 in row 30a are arranged adjacent to the gap between perforations 30 in row 30b or adjacent to part of the gap and part of a perforation 30 in row 30b.

[0802] Each perforation 30 comprises an opening, which in this embodiment is in the shape of a circle. In this embodiment, the size of each perforation 30 is defined by the diameter of the circle. However, the person skilled in the art will understand that the size of the opening may be defined depending on the shape of the opening. In some embodiments, the size of a circle is the diameter. In other embodiments, the size of an oval is the longer diameter. In further embodiments, the size of a hexagon is the longest diagonal; and the size of a triangle, a square, a rectangle, an octagon or any other polygon perforation may be the longest side. In the present embodiment, each perforation 30 has a diameter of 2.20 mm and are therefore of sufficient size to provide breathability to the wound dressing in the event that some of the perforations reduce in diameter after their formation, for example by the adhesive entering the opening of a perforation. As such, the adhesive skin contact layer maintains an environment optimised for wound healing. Moreover, each perforation 30 is a through hole in the adhesive skin contact layer 200 which can enable fluid to flow through the layer 200. The adhesive skin contact layer 200, therefore, helps to prevent tissue ingrowth into the other material of the wound dressing.

[0803] The perforations 30 may have a pitch (i.e., the distance between the centre point of a perforation and the centre point of an adjacent perforation) in a first direction (shown as A in FIG. 2 and applicable to the perforations 30 shown in FIGS. 13 and 14) of 8.0 mm, and a pitch in a second direction (shown as B in FIG. 2 and applicable to the perforations 30 shown in FIGS. 13 and 14) of 5.6 mm. Advantageously, the pitch of the perforations 30 has a ratio of perforation:no-perforation which provides efficient moisture evaporation, prevents pooling and strongly adheres to the peri-wound skin of the patient. Surprisingly, and advantageously, tests have shown that the adhesive skin contact layer 200 remains adhered to a patient for at least seven days.

[0804] The total area of the perforations 30 may be 2100 mm.sup.2 and the total volume of the perforations may be 2100 mm.sup.3. The degree of perforation may be 10.66% of the area of the adhesive skin contact layer 200. The perforations 30 are distributed evenly throughout the adhesive skin contact layer 200. The perforations 30 may be formed by a mechanical punch perforating process which does not result in the formation of a doughnut or volcano structure around the perforations after formation of the perforations 30. The perforations may be formed by mechanical punch perforating the adhesive skin contact layer 200 comprising a release liner (not shown) covering at least one surface of the adhesive skin contact layer 200.

[0805] The adhesive skin contact layer 200 may have a thickness of 1.0 mm and a width and length (measured from the periphery of the adhesive skin contact layer 200) each of 130 mm. The adhesive skin contact layer 200 has an outer periphery in the shape of a square. The adhesive skin contact layer 200 comprises an upper surface 200a and a lower surface 200b. The lower surface 200b contacts the dermal surface in use.

[0806] The adhesive skin contact layer 200 may have a perimetral shape with a central window 90, therefore, the adhesive skin contact layer 200 may be an adhesive skin contact border layer 200. The border layer 200 may comprise an outer periphery which defines the outer shape of the border layer 200, which, in this embodiment, is a rectangle. The border layer 200 may comprise an inner periphery which defines the shape of the window 90. The window 90 may be of the same, or similar shape, to that of the outer periphery of the border layer 200. In other embodiments, the window may have a different to that of the outer periphery of the border layer 200. For example, in embodiments comprising a border layer having an outer periphery which is square, the window may be, for example, a square or a rectangle. In embodiments, comprising a border layer having a square outer periphery and a window which is a rectangle, there may be greater overlap between the absorbent structure and the adhesive skin contact layer, therefore, allowing for a greater surface area for adhesion between the adhesive skin contact layer and the absorbent structure.

[0807] In this embodiment, the window 90 has a perimeter which is a rectangle, therefore, the length of the transverse sides of the window is less than the length of the longitudinal sides of the window 90. The window 90 is a rectangle through-hole in the adhesive skin contact layer 200. The shape of the window 90 provides for greater overlap of the absorbent structure 11 and the adhesive skin contact layer 200, especially at the corresponding corner portion of the absorbent structure 11 and the adhesive skin contact layer 200. This is beneficial not least because it allows for a greater surface area for adhesion between the adhesive skin contact layer 200 and the absorbent structure 11, therefore, providing greater structural integrity to the wound dressing 10. The greater structural integrity means that the absorbent structure 11 maintains its position within the wound dressing 10 with reduced possibility of the absorbent structure 11 becoming dislodged from its position within the wound dressing 10 when in use, in particular when in use when the wound dressing 10 is wet with exudate or other fluids.

[0808] The window 90 is located centrally relative to the periphery of the adhesive skin contact layer 200. Each side of the window 90 is arranged parallel to each of the corresponding sides of the adhesive skin contact layer 200. Each longitudinal side of the window 90 may have a length of about 210 mm and each traverse side of the window 90 may have a length of about 160 mm. The window may have an area of about 33,600 mm.sup.2. The skilled person will appreciate that the window 90 may be enlarged by any suitable means, for example by cutting the adhesive skin contact layer 200. The window 90 in the adhesive skin contact layer 200 enables the wound of a patient to contact, or be in fluid communication with, other layers of the wound dressing 10, for example the wound contact layer 40, when the wound dressing 10 is applied to the skin of a patient.

[0809] The adhesive skin contact layer 200 comprises an upper surface 200b and a lower surface 200a. The lower surface 200a contacts the dermal surface in use. In use, the lower surface 200a of the adhesive skin contact layer 200 is detachably adhered to a dermal surface (not shown) of a patient such that the wound site (not shown) is located within the window 90. As such, the adhesive skin contact layer 200 is not in direct contact with the wound site but does wholly surround it. Thus, the adhesive skin contact layer 200 is in contact with intact peri-wound skin only. The upper surface 200b may be outwardly facing away from the patient's body.

[0810] A removable cover or release layer 21 may be adhered to the lower surface 200a of the adhesive skin contact layer 200. The removable cover 21, which may comprise folded grip sections 21a, is removable from the lower surface 200a of the adhesive skin contact layer 200. Thus, the removable cover protects the adhesive skin contact layer 200 when the removable cover 21 is adhered to the adhesive skin contact layer 200, but when the removable cover 21 is removed from the lower surface 200a of the adhesive skin contact layer 200 for use of the wound dressing 10, the lower surface 200a is exposed and able to releasably secure the wound dressing 10 to the skin of a patient.

[0811] The airway 80 may comprise a connector 82 at its distal end. The connector 82 may connect the airway 80 to an internal lumen of a conduit or tube (not shown) which in turn is connected to a source of negative pressure. The source of negative pressure may comprise a pump (not shown) for generating negative pressure and the conduit or tube may connect the pump and wound dressing 10 via the airway 80. The pump may provide negative pressure to the wound dressing 10 via the internal lumen of the conduit or tube, along the airway 80, and through an opening 12 in the wound dressing 10. In the present embodiment, the source of negative pressure may comprise a one-way valve (not shown) in-line between the pump and the wound dressing 1 to maintain a negative pressure within the wound dressing 1 when the pump is disconnected from the tube.

[0812] The airway may further comprise an adhesive layer 81 at its proximal end for adhering the proximal end of the airway 80 to a second surface 7b0 (outer facing surface) of the backing layer 70. The adhesive layer 81 may comprise an opening 12a for allowing a flow of air from the wound dressing 10 into the airway 80.

[0813] The opening 12 may comprise an opening in each of the backing layer 70 and absorbent structure 11. The backing layer 70 may comprise an opening 12b, and the absorbent structure 11 may comprise an opening 12c. Openings 12b and 12c may be arranged off-centre relative to the periphery of the backing layer 70 and the absorbent structure 11, respectively. Opening 12c may comprise corresponding openings in each of the superabsorbent layer 60, transmission layer 50 and wound contact layer 40. Opening 12c may be in fluid communication with the window 90 and, therefore, the wound site. The openings 12a, 12b and 12c may provide a fluid pathway between the wound site and the airway 80. Thus, in use, the openings 12a, 12b and 12c allow for the flow of air from the wound site, through the absorbent structure 11, through the backing layer 70, along the airway 80 and along a tube or conduit (not shown) toward a source of negative pressure (not shown).

[0814] The backing layer 70 may comprise a first surface 7a0 and the second surface 7b0. In use, the first surface 7a0 may be inwardly facing toward the patient's body, and the second surface 7b0 may be arranged opposite the first surface 7a0, outwardly facing away from the patient's body.

[0815] The absorbent structure 11 may comprise a first surface and a second surface. In use, the first surface of the absorbent structure 11 may predominantly comprise a wound facing surface of the wound contact layer 40. In use, the second surface of the absorbent structure 11 may predominantly comprise an outwardly facing surface of the superabsorbent layer 60. The first surface of the absorbent structure 11 may be adjacent, and in contact with, the upper surface 200b of the adhesive skin contact layer 200. In particular, the peripheral portion of the first surface of the absorbent structure 11 may be in contact with the upper surface 200b of the adhesive skin contact layer 200. The peripheral edge of the second surface of the absorbent structure 11 may be adjacent, and in contact with, the first surface 7a0 of the backing layer 70.

[0816] The wound contact layer 40 may comprise a first surface arranged opposite a second surface. In use, the first surface may be inwardly facing toward a patient's body, and the second surface may be outwardly facing, away from the patient's body. The first surface of the wound contact layer 40 may contact the wound when the wound dressing 10 is adhered to the skin adjacent to the wound (i.e., when in use). The first surface of the wound contact layer 40 may be substantially aligned with the window 90 of the adhesive skin contact layer 200. As such, in use, the first surface contacts the wound through the window 90. The second surface of the wound contact layer 40 may be adjacent, and in contact with, a first surface of the transmission layer 50 or a first surface of the superabsorbent layer 60. In the described embodiment, the second surface of the wound contact layer 40 is adjacent, and in contact with, the first surface of the transmission layer 50.

[0817] The transmission layer 50 may comprise a first surface arranged opposite a second surface. In use, the first surface may be inwardly facing toward a patient's body, and the second surface may be outwardly facing away from the patient's body. The first surface of the transmission layer 50 may be adjacent, and in contact with, the second surface of the wound contact layer 40 or a second surface of the superabsorbent layer 60. The second surface of the transmission layer 50 may be adjacent, and in contact with, a first surface of the superabsorbent layer 60 or the first surface 7a of the backing layer 70. In the described embodiment, the first surface of the transmission layer 50 is adjacent, and in contact with, the second surface of the wound contact layer 40, and the second surface of the transmission layer 50 is adjacent, and in contact with, the first surface of the superabsorbent layer 60.

[0818] The superabsorbent layer 60 may comprise a first surface arranged opposite a second surface. In use, the first surface may be inwardly facing toward a patient's body, and the second surface may be outwardly facing away from the patient's body. The first surface of the superabsorbent layer 60 may be adjacent, and in contact with, the second surface of the wound contact layer 40 or the second surface of the transmission layer 50. The second surface of the superabsorbent layer 60 may be adjacent, and in contact with, the first surface of the transmission layer 50 or the first surface 7a of the backing layer 70. In the described embodiment, the first surface of the superabsorbent layer 60 is adjacent, and in contact with, the second surface of the transmission layer 50, and the second surface of the superabsorbent layer 60 is adjacent, and in contact with, the first surface 7a of the backing layer 70.

[0819] The adhesive skin contact layer 200 may radially overlap the absorbent structure 11. The adhesive skin contact layer 200 may comprise an interior portion adjacent to and surrounding the window 90, and an exterior portion radially outwardly from the interior portion. The interior portion and the exterior portion of the first surface 20a of the adhesive skin contact layer 200 may contact and adhere to the skin of a patient in use. The interior portion of the second surface 200b of the adhesive skin contact layer 200 may be adjacent, and in contact with, a portion of the first surface of the wound contact layer 40. The exterior portion of the second surface 200b of the adhesive skin contact layer 200 may be adjacent, and joined with, a peripheral portion of the first surface 7a0 of the backing layer 70. Beneficially, this helps to prevent wound exudate escaping from the confines of the wound dressing which would be unhygienic and cause discomfort for the user. Moreover, this also helps maintain a negative pressure at the wound site.

[0820] The exterior portion of the second surface 200b of the adhesive skin contact layer 200 may be joined to the peripheral portion of the first surface 7a0 of the backing layer 70 by heat lamination, adhesive, welding or stitching.

[0821] The exterior portion of the second surface 200b of the adhesive skin contact layer 200 may extend radially beyond the periphery of the absorbent structure by about 27.5 mm.

[0822] At least two of the wound contact layer 40, the transmission layer 50 and the superabsorbent layer 60 may be laminated together. In the described embodiment, each of the wound contact layer 40, the transmission layer 50 and the superabsorbent layer 60 are laminated together, therefore forming a consolidated absorbent structure 11. Advantageously, this means that the absorbent structure 11 of the present invention is manufactured without requiring any relatively rigid dressing and binding components. Thus, the present invention provides an absorbent structure 11 which is flexible, therefore benefits user comfort, and which is cheaper to manufacture than absorbent structures and, therefore negative pressure wound dressings, of the prior art. Moreover, beneficially lamination does not require any complex equipment or manufacturing techniques. Thus, the present invention is simple to manufacture.

[0823] Each of the wound contact layer 40, the transmission layer 50 and the superabsorbent layer 60 may be laminated together by a scatter-coat adhesive. The scatter-coat adhesive may be a hot melt, scatter-coat adhesive. In the described embodiment, the scatter-coat adhesive is polycaprolactone and has the following properties: [0824] a melt flow index of between 5.2 g/10 min and 11.3 g/10 min, as tested with 2.16 kg, 1 PVC die at 160 C.; [0825] a maximum water content of 0.35%; [0826] a mean molecular weight of 50,000; [0827] a melting point of 60 C.; and [0828] a solubility parameter of 9.34 cal/cm.sup.3 to 9.43 cal/cm.sup.3.

[0829] The scatter-coat adhesive may comprise particles of which at least 98% have a particle size of 0.6 mm.

[0830] The wound contact layer 40, the transmission layer 50 and the superabsorbent layer 60 may be laminated together by a laminator having the following processing properties: [0831] Heating zone temperature of 125 C.; [0832] Cooling zone temperature of 25 C.; [0833] Web tension (for each unwind reel) of 125 N; [0834] Crush roller pressure of 1000 N; and [0835] Web speed of 10 m/min.

[0836] The wound contact layer 40 may further comprise a central region and a peripheral region. The central region may be substantially square and is bordered on each side by the peripheral region.

[0837] In the described embodiment, the first surface, which contacts the wound in use, of the wound contact layer 40 may comprise warp stitches (longitudinal to the plane of the wound contact layer 40) only, i.e., the first surface does not comprise any weft stitches (transverse to the plane of the wound contact layer 40). Advantageously, this means that the amount of non-gelling fibres (which may include weft stitches) at the wound contact surface is minimised. Thus, there is a greater ratio of gelling fibres to non-gelling fibres at the wound contact surface in contact with the wound and, therefore, wound exudate. Thus, the absorption capacity of the wound contact layer is increased. As such, pooling of wound exudate at the wound site is prevented, or at least significantly reduced and an environment optimised for wound healing is maintained at the wound site.

[0838] The warp stitches of the first surface may have a pitch of 6.6 mm and a stitch density of 7.5 stitches/cm.

[0839] The second surface of the transmission layer 50, which is laminated to the first surface of the transmission layer 50, comprises warp stitches and weft stitches. Each of the warp stitches and the weft stitches of the second surface of the transmission layer have a pitch of 6.6 mm and a stitch density of 7.5 stitches/cm.

[0840] In other embodiments, the central region of the first surface of the wound contact layer 40 may comprise warp stitches only and the peripheral region of the first surface of the wound contact layer 40 may comprise warp and weft stitches.

[0841] The wound contact layer 40 may have a weight of 100 gsm and a thickness of 3.0 mm.

[0842] Between the first surface of the wound contact layer 40 and the second surface pf the wound contact layer 40, which are joined about their periphery, the wound contact layer 40 may comprise a plurality of gel-forming fibres which, upon the uptake of wound exudate, become moist, slippery or gelatinous. Specifically, in this embodiment, the gel-forming fibres are hygroscopic fibres which upon the uptake of wound exudate become gelatinous. The gel-forming fibres may be of the type which retain their structural integrity on absorption of exudate. In the present embodiment, the fibres are sodium carboxymethylcellulose fibres having a degree of substitution of 0.30 carboxymethyl groups per glucose unit, as measured by IR spectroscopy (as defined in WO00/01425). The absence of weft stitches at the first surface of the wound contact layer 40 means that a greater amount of gel-forming fibres, as described above, are exposed at the first surface and, therefore, in contact with the wound. As such, the wound contact layer 40 is higher gelling, i.e., has a significantly greater absorbency capacity and is more retentive, than gel-forming fibres of the prior art. As such, the wound contact layer 40 absorbs a greater amount of wound exudate. Thus, pooling of wound exudate at the wound site is prevented, or at least significantly reduced.

[0843] The sodium carboxymethylcellulose fibres may be made by carboxymethylating a non-woven cellulosic fabric having an absorbency of 18 g/g of Solution A (sodium/calcium chloride solution), as measured by the method described in BS EN 13726-1 (2002) Test methods for primary wound dressings, section 3.2 Free swell absorptive capacity. The carboxymethylation is performed by contacting the fabric with an alkali and a carboxymethylating agent such as chloroacetic acid in a combined alcohol and aqueous system. The cellulosic fabric comprises solely of cellulosic fibre and comprises continuous filament yarn.

[0844] The gel-forming fibres may have an absorbency of 2 grams 0.9% saline solution per gram of fibre (as measured by the free swell method).

[0845] The wound contact layer 40 may be stitched using lyocell yarn (produced under the trade name Tencel yarn).

[0846] The transmission layer 50 is substantially square, as is the wound contact layer 40 and the superabsorbent layer 60, and has a thickness of 1.8 mm and is made of a polyurethane foam. The transmission layer 50 may have a density of between 26 Kg/M.sup.3 and 28 Kg/M.sup.3 and a tensile strength of 150 kPa. The transmission layer 50 may have an elongation at break value of 300% and a cell count of between 17 and 26/cm. Moreover, the transmission layer 50 may have a 40% CLD hardness of between 2.5 and 4.5 kPa.

[0847] The superabsorbent layer 60 comprises an upper layer having the second surface, and a lower layer having the first surface. Between the upper layer and the lower layer, there is enclosed a first material comprising non-woven fibres, an absorbent material and a hot melt binder.

[0848] The hot melt binder may be present in an amount of 70 g/m.sup.2. The hot melt binder may be a copolymer and, in the described embodiment, may be ethylene-vinyl acetate (EVA). In manufacture of the superabsorbent layer, the superabsorbent layer may be heated to melt the hot melt binder and bind the non-woven fibres of the first material together. Advantageously, this prevents, or at least significantly limits, the amount of shedding of the fibres of the superabsorbent layer when in use. Thus, the presence of the hot melt binder in the superabsorbent layer significantly increases the strength of the layer, preventing dissociation of the absorbent structure.

[0849] The absorbent material may be a superabsorbent material, capable of absorbing wound exudate while allowing the passage of fluid through it. The superabsorbent material may be sodium polyacrylate and in the form of a powder which, advantageously, increases the surface area to volume ratio of the superabsorbent material, therefore enhancing the absorbent property of the material.

[0850] The non-woven fibres may be cellulose fibres. The cellulose non-woven fibres may be arranged as a cellulosic non-woven matrix of fibres and may be a support onto which the absorbent material may be incorporated, for example, in the described embodiment, the absorbent material is dispersed upon the cellulosic non-woven matrix. The absorbent material may be dispersed evenly, or substantially evenly, throughout or upon the non-woven fibres, for example the cellulosic non-woven matrix.

[0851] The upper layer and the lower layer of the superabsorbent layer 60 may each be a cellulosic fabric layer. The upper fabric layer and the lower fabric layer may be joined around their entire periphery to enclose the first material.

[0852] The superabsorbent layer 60 may comprise a plurality of fenestrations (not shown). Each of the plurality of fenestrations may be openings in the form of slits in the superabsorbent layer 60. Each fenestration may have a length equal to 80% of the length of the superabsorbent layer 60. Each of the upper layer and the lower layer may comprise a plurality of fenestrations. The fenestrations may be arranged in a direction planar to a longitudinal axis and transverse to a longitudinal axis of the superabsorbent layer 60. Advantageously, this arrangement aids in managing a flow of exudate through the superabsorbent layer 60 of the wound dressing 10. The fenestrations encourage or enable wound exudate to travel laterally on the superabsorbent layer 60, as opposed to axially, and assist in negative pressure transmission through the superabsorbent layer 60.

[0853] The superabsorbent layer 60 may have a basis weight of 460 g/m.sup.2, a thickness of 2.55 mm and a density of 0.255 g/cm.sup.3. Moreover, the superabsorbent layer 60 may have a tensile strength (dry) of 45 N/50 mm, an absorbent capacity of 25 g/g 10 min, and an absorbency under compression capacity of 0.85 g/cm.sup.2.

[0854] Each of the wound contact layer 40, transmission layer 50 and superabsorbent layer 60 are substantially planar.

[0855] In use, the wound dressing 10 forms part of a negative pressure wound exudate management system comprising the wound dressing 10 and further comprising a source of negative pressure (not shown) and a coupling member (for example, airway 80) for providing negative pressure to the wound dressing from an internal lumen of a conduit or tube (not shown) and through an opening 12 in the wound dressing 10. The source of negative pressure comprises a pump for generating negative pressure and the tube connects the pump and wound dressing 10 via the airway 80. In the present embodiment, the source of negative pressure may comprise a one-way valve (not shown) in-line between the pump and the wound dressing 10 to maintain a negative pressure within the wound dressing 10 when the pump is disconnected from the tube.

[0856] In use, the folded grip sections 21a of the removable cover 21 are separated and peeled in opposite directions to remove the removable cover 21 from the lower surface 200a of the adhesive skin contact layer 200. The adhesive skin contact layer 200 is therefore exposed and is then adhered to the intact peri-wound skin around a wound. The wound is located within the window 90 of the adhesive skin contact layer 200. The wound dressing 10 is connected to a source of negative pressure before or after application of the dressing to the wound. Upon leaving the wound, wound exudate contacts the first surface of the wound contact layer 40 and wicks away from the wound site, toward the transmission layer 50. The high gelling ability of the wound contact layer 40 facilitates absorption and retention of the wound exudate. Lamination of the wound contact layer 40, transmission layer 50 and superabsorbent layer 60 means each of these layers form a consolidated, absorbent and retentive structure 11. The wound exudate wicks from the upper surface of the wound contact layer 40 to the transmission layer 50. Lateral movement of the exudate occurs in the transmission layer 50 to spread the wound exudate across the surface area of the dressing. The exudate then wicks to the superabsorbent layer 60 where it is absorbed and retained prior to being transmitted out of the dressing 10 via vapour transmission through the backing film 70.

[0857] The one or more embodiments are described above by way of example only. Many variations are possible without departing from the scope of protection afforded by the appended claims.