GB2404861A - Absorbant layers for use in wound dressings - Google Patents

Abstract

A wound dressing 1 comprising an absorbent sheet 4, wherein the absorbent sheet comprises a barrier 6 region to block lateral transport of liquid through the absorbent sheet to an edge of the absorbent sheet. The barrier 6 layer may be a hydrophobic region, or a region of pore blocking by heat and/or compression, adhesive gel blocking or the like. The absorbent sheet 4 can be laminated directly to a liquid permeable top sheet 5 of the same dimensions, since the barrier region prevents leakage of wound exudate out of the edges of the dressing. In the case of the adhesive gel blocking barrier layer, this permeates through the absorbent layer to bond the permeable top sheet, absorbent sheet and backing sheet together. Also provided are methods of making wound dressings according to the invention.

Description

IMPROVED ABSORBENT SHEETS FOR USE IN WOUND DRESSINGS

The present invention relates to absorbent sheet materials for use in wound dressings, and to the manufacture of wound dressings containing such materials.

Absorbent dressings are commonly used in medical practice. They frequently comprise an "island" of absorbent sheet material laminated to a central region of a larger, adhesive-coated, semipermeable backing sheet, whereby an adhesive coated margin of the backing sheet extends around the absorbent material for It) adhering the dressing to the skin of a patient around the wound being treated. In many cases the absorbent island is itself covered by a liquid-permeable wound facing sheet, for example a perforated plastic film sheet or a sheet of liquid- permeable foam or a sheet of hydropolymer. The wound facing sheet may provide a more wound-friendly and non-adherent surface than the absorbent layer material. The wound contacting sheet can be useful to prevent wet- back from the absorbent layer to the wound and/or to prevent excessive drying out of the wound by the absorbent layer, and may provide other advantages.

It has not hitherto been conventional for the wound facing layer of absorbent dressings to be made coterminous with the absorbent layer in such dressings, because of certain problems. A first problem is leakage of wound fluid from the edges of the absorbent layer. Such leakage can soil clothes or bedding. In the case of absorbent island dressings, such leakage can cause loss of adhesion between the adhesive-coated backing sheet and the skin around the wound.

Another problem is poor adhesion of the wound contacting sheet to the absorbent layer and/or to the backing sheet when wet, which can result in delamination of the wound facing sheet when the absorbent layer is wet. For these reasons, the wound contacting layer is usually made with a larger area than the absorbent layer so that it extends beyond the absorbent layer and is bonded directly to the adhesive-coated backing sheet around the absorbent layer. In these embodiments, the absorbent layer is in effect received in an envelope defined by the backing sheet and the wound facing sheet. In certain other embodiments, for example as described in GB-A-2348136, the wound contacting sheet is wrapped around the absorbent layer to form an envelope, and then this envelope is adhered to the backing sheet.

However, it will be appreciated that the above constructions using a wound contacting layer that is larger than the absorbent sheet entail some additional expense in terms of materials and manufacturing complexity. Relatively large amounts of backing material and wound facing material are needed to achieve a desired liquid absorbency. The problem of delamination of the dressing can still arise due to wound fluid leaking out of the edges of the absorbent layer.

In a first aspect, the present invention provides a wound dressing comprising an absorbent sheet, wherein the absorbent sheet comprises a barrier region to block lateral transport of wound fluid through the absorbent sheet to an edge of the absorbent sheet.

The absorbent sheet may comprise any of the materials conventionally used for absorbing wound fluids, serum or blood in the wound healing art, including gauzes, nonwoven fabrics, hydrophilic foams, freeze-dried or solvent-dried sponges, superabsorbents, hydrogels and mixtures and combinations thereof.

In certain embodiments, the absorbent sheet may be a woven, knitted or nonwoven fabric, for example a nonwoven web of fibers such as viscose staple fibers. The web may optionally contain superabsorbent fibers or particles. In these embodiments, the fabric may comprise thermoplastic fibers such as bicomponent fibers, whereby the liquid blocking region can be formed by application of heat and pressure to form a thermally bonded region of low porosity.

The area of the absorbent sheet is typically in the range of from 1cm2 to 200cm2, more preferably from 4cm2 to 100cm2. The basis weight of the absorbent layer may for example be in the range of 50-50Ogim2, such as 10040Og/m2. The uncompressed thickness of the absorbent layer may be in the range of from 0.5mm to 1 Omm, such as 1 mm to 4mm. The free (uncompressed) liquid absorbency measured for physiological saline may be in the range of 5 to 30 g/g at 25 C.

The barrier region normally comprises one or more barrier strips located proximate to an edge of the absorbent sheet. The barrier strips are typically from about 1 mm to about 5mm wide and extend along at least one side of the absorbent sheet, and preferably along all sides of the sheet. The outer edge of the barrier region is typically from about O to about 20mm from the edge of the absorbent sheet, for example about 1 to about 10 mm from the edge of the absorbent sheet. The lO barrier regions may be made by any convenient means, but these generally fall into one or more of (a) making the material of the absorbent sheet hydrophobic in the region, for example by applying a hydrophobic finish; and/or (b) reducing the porosity of the absorbent sheet in the barrier region, for example by blocking the pores of the material with a resin such as a silicone adhesive or by permanently compressing the absorbent sheet in the barrier region by thermal, ultrasonic or compressive bonding.

The wound dressing according to the present invention normally further comprises a liquid-permeable wound facing layer over the absorbent sheet. The wound facing layer may be any medically acceptable wound facing sheet, including woven and nonwoven textile materials. In certain embodiments, the wound facing sheet comprises a layer of absorbent foam, such as an open celled hydrophilic polyurethane foam prepared in accordance with EPA-0541391, the entire content of which is expressly incorporated herein by reference. In other embodiments, the wound facing layer comprises an apertured thermoplastic film. Suitable thermoplastics include polyolefins such as polyethylene, copolymers such as ethylene methyl acrylate, or fluoropolymers such as polyvinylidene fluoride. In yet other suitable embodiments the wound facing layer comprises an apertured film of waterinsoluble hydrogel material. For example, the apertured sheet may be a self-supporting sheet of such a hydrogel material as described in WO03/011352, the entire content of which are incorporated herein by reference.

For the embodiments wherein the wound facing sheet comprises an apertured film, the apertures typically make up from about 0.1% to about 50% of the area of the film, more typically from about 1% to about 30% of the area of the apertured film, and preferably from about 10% to about 25% of the area of the apertured film.

Typically, the apertured film has from about 1 to about 30 apertures per square cm, for example from about 4 to about 15 apertures per square cm or from about 5 to about 10 apertures per square cm. In certain embodiments the apertures are uniformly distributed over the surface of the film, preferably in a regular pattern.

lO The mean area of each aperture may for example be from about 0.01 to about 10 mm2, preferably from about 0.1 to about 4 mm2, and more preferably from about 1mm2 to about 2mm2. In certain embodiments, the apertures have a ratio of maximum length to maximum width of from about 1 to about 10, preferably from about 1 to about 3, and more preferably from about 1 to about 1.5. Suitable aperture shapes include round, oval or regular polygonal The wound facing sheet may be coated on either, or both, surfaces with a layer of hydrogel, which may be apertured, to provide improved control of wound moisture levels and to provide a more wound-friendly dressing. Suitable hydrogel coatings are described in W002/38097 and W003/045294, the entire contents of which are incorporated herein by reference.

The wound facing sheet may also consist of, or comprise, or be occlusively coated by, a composition that is soluble in a component of wound exudate, whereby the permeability of the wound facing sheet is dependent on the amount and/or the composition of wound exudate. For example, the composition may be soluble in water to provide increased absorption rates for highly exuding wounds, as described in GB-A-2379392 The composition may be soluble in the presence of enzymes that are markers for wound chronicity, such as protease enzymes, as described in W003/047643. The composition may be soluble in the presence of enzymes that are markers for wound infection, such as Iysozyme, as described in GB0221064.9 filed 11th September 2002. The composition may be soluble in the presence of enzymes that are markers for pain, or other wound conditions. The contents of all of the above applications are hereby incorporated by reference.

It is an advantage of the present invention that an edge of the wound facing sheet may coincide with the edge of the absorbent sheet adjacent to the barrier region, since the barrier region overcomes the problem of liquid leaking out of that edge of the absorbent layer. In certain embodiments, the barrier region extends substantially all around the absorbent layer to block liquid transport to substantially ail edges of the absorbent layer. The wound contacting layer can then be made substantially coterminous with the absorbent layer. Such embodiments are especially easy to make in a continuous process by laminating the wound facing sheet to the absorbent sheet, followed by cutting or die cutting the dressings.

The wound facing sheet may be bonded to the absorbent sheet by any suitable means, including melt bonding, needling, or entanglement. In certain embodiments, the wound facing sheet may be adhesively bonded to the absorbent sheet, for example by an adhesive applied in a margin between the barrier regions and the edge of the absorbent layer. In certain preferred embodiments, the barrier regions comprise a layer of adhesive extending through the absorbent layer to fix the wound facing layer, the absorbent layer and the backing layer. It is a further advantage of the present invention that the barrier layer, by keeping a marginal area of the absorbent sheet dry, prevents loss of adhesion in that region and hence delamination of the wound facing sheet when the absorbent layer is saturated with wound exudates.

Suitably, the wound dressing according to the present invention further comprises a backing sheet extending over the absorbent sheet opposite to the wound facing side of the absorbent layer. Suitably, the backing sheet is larger than the absorbent layer such that a marginal region of width 1mm to 50 mm, for example 5mm to 20mm extends around the absorbent sheet and optional wound facing sheet to form a so-called island dressing. In such cases, the backing sheet is suitably coated with a pressure sensitive medical grade adhesive in at least its marginal region.

Preferably, the backing sheet is substantially liquid-impermeable. The backing sheet is preferably semipermeable. That is to say, the backing sheet is preferably permeable to water vapour, but not permeable to liquid water or wound exudate.

Preferably, the backing sheet is also microorganism-impermeable. Suitable continuous conformable backing sheets will preferably have a moisture vapor transmission rate (MVTR) of the backing sheet alone of 300 to 5000 gim2124hrs, preferably 500 to 2000 gim2124hrs at 37.5 TIC at 100% to 10% relative humidity difference. The backing sheet thickness is preferably in the range of 10 to 1000 l 0 micrometers, more preferably 100 to 500 micrometers.

The MVTR of the dressing according to the present invention as a whole is lower than that of the backing sheet alone, because the absorbent sheet and wound facing sheet partially obstruct moisture transfer through the dressing. Preferably, ]5 the MVTR of the dressing (measured across the island portion of the dressing) is from 20% to 80% of the MVTR of the backing sheet alone, more preferably from 20% to 60% thereof, and most preferably about 40% thereof. It has been found that such moisture vapor transmission rates allow the wound under the dressing to heal under moist conditions without causing the skin surrounding the wound to macerate.

Suitable polymers for forming the backing sheet include polyurethanes and poly alkoxyalkyl acrylates and methacrylates such as those disclosed in GB-A- 1280631. Preferably, the backing sheet comprises a continuous layer of a high density blocked polyurethane foam that is predominantly closed-cell. A suitable backing sheet material is the polyurethane film available under the Registered Trade Mark ESTANE 5714F.

The adhesives useful in the wound dressings of the present invention are suitably moisture vapor transmitting and/or patterned to allow passage of water vapor therethrough. The adhesive is suitably a moisture vapor transmitting, medical grade pressure-sensitive adhesive layer of the type conventionally used for island- type wound dressings, for example, a pressure sensitive adhesive based on acrylate ester copolymers, polyvinyl ethyl ether and polyurethane as described for example in GB-A-1280631. The basis weight of the adhesive layer is preferably to 250 g/m2, and more preferably 50 to 150 g/m2. Polyurethane-based pressure sensitive adhesives are especially suitable.

It is a further advantage of the present invention that an edge of the backing layer may coincide with the edge of the absorbent sheet adjacent to the barrier region, since the barrier region overcomes the problem of liquid leaking out of that edge of the dressing to soil clothes or bedclothes. In certain embodiments, the barrier l O region extends substantially all around the absorbent layer to block liquid transport to substantially all edges of the absorbent layer. The backing layer can then be made substantially coterminous with the absorbent layer and the wound facing layer, where present. Such dressings are referred to as borderless dressings, and may be especially easy to manufacture in a continuous process by simply laminating the absorbent, wound facing, and backing sheets together and then cutting or die-cutting the dressings from the laminate. It will be appreciated that, in such embodiments, it may be especially advantageous to have a layer of medically acceptable adhesive on the wound facing side of the wound facing sheet. The adhesive may be coated uniformly on the wound facing surface, or it may be coated around the edges of the wound facing sheet to form an adhesive margin.

The wound facing surface of the dressing is typically protected before use by a removable cover sheet. The cover sheet is normally formed from flexible thermoplastic material or a release-coated paper. Suitable materials include polyesters and polyolefins. The adhesive- facing surface of the cover sheet is usually a release surface. That is to say, a surface that is only weakly adherent to any adhesive on the backing sheet and/or on the wound contacting layer. For example, the cover sheet may be formed from a non-adherent plastic such as a fluoropolymer, or it may be provided with a release coating such as a silicone or fluoropolymer release coating.

The wound dressing according to the present invention may be medicated. For example a medicament may be dispersed in the absorbent sheet, or it may be applied to the wound facing sheet, for example in a layer coated on the wound facing sheet. Suitable medicaments include one or more therapeutic agents suitable for the treatment of wounds. In certain embodiments the therapeutic agents are selected from the group consisting of antiseptics, antibiotics, analgesics, steroids, growth factors, and mixtures thereof. Suitable therapeutic agents are the antimicrobials, in particular antibiotics and antiseptics such as colloidal silver, silver sulfadiazine, povidone iodine, chlorhexidine, and mixtures lO thereof. Suitably, the wound dressing material according to the present invention comprises from about 0.001mg to about 100mg of the one or more therapeutic substances, more preferably from about 0.05mg to about 20mg.

The wound dressing according to the present invention may be sterile and packaged in a microorganism-impermeable container.

In a second aspect, the present invention provides a method of manufacture of a wound dressing comprising the steps of: providing a strip of absorbent material; forming a plurality of transverse barrier regions for blocking liquid flow through the absorbent material at intervals along the strip; laminating the strip of absorbent material to a strip of liquid permeable sheet material; and cutting the strip transversely at intervals to form a plurality of wound dressing laminated pieces.

The method may further comprise forming at least one longitudinal barrier region in the absorbent strip, and further comprising cutting the strip longitudinally to form said plurality of wound dressing laminated pieces. The longitudinal barrier region may be continuous or interrupted, and it may be a straight line parallel to the long axis of the strip, or it may be a serpentine or zig-zag line, for example if the strip is being cut in a tessellation such as hexagonal tessellation.

The step of laminating could comprise thermal bonding, but more usually it will comprise adhesive bonding between the absorbent sheet, the liquid permeable layer and adhesive backing sheet. The adhesive layer may be continuous or interrupted. In certain embodiments, strips of adhesive are used both to form the barrier regions in the absorbent sheet and to bond the wound facing sheet, the absorbent sheet and the backing sheet together. The thermal laminating, if used may be provided in the same step as forming the barrier regions by thermal bonding.

The method according to this aspect of the invention may further comprise applying each of said absorbent pieces to an adhesive-coated backing sheet such that the absorbent layer contacts the adhesive-coated backing sheet. In these embodiments, the method usually comprises making up the absorbent pieces into island-type dressings. In which there is a margin of adhesive-coated backing material around each absorbent island.

In certain embodiments the method of the present invention may be adapted to prepare borderless dressings. In these embodiments, a strip of the wound facing sheet material is laminated to the strips of absorbent sheet and backing sheet and the resulting strip of laminate comprising all three sheets is then cut into a plurality of borderless dressings.

The processes of the present invention may, of course, comprise steps of applying further layers to the dressing, for example an adhesive layer on the wound facing surface of the wound facing sheet and/or a releasecoated protective cover sheet, both as described above.

The wound dressings according to this invention provide at least the following advantages: a) the barrier region bonds and holds the 3 pieces of the dressing together even when wet and b) the barrier region helps to retain and disperse wound fluid within the absorbent layer that would otherwise leak out from the edge of the absorbent layer prior to saturation.

Specific embodiments of the present invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a bottom plan view of an island wound dressing according to a first embodiment of the invention with the liquid permeable top sheet partially cut away to show the absorbent layer; Figure 2 shows a bottom plan view of an island wound dressing according to a second embodiment of the invention with the liquid permeable top sheet partially cut away to show the absorbent layer; Figure 3 shows a bottom plan view of a borderless wound dressing according to a lO third embodiment of the invention with the liquid permeable top sheet partially cut away to show the absorbent layer; Figure 4 shows a schematic cross- sectional view through the dressing of Figure 3; Figure 5 shows an enlarged detail of Figure 4; and Figure 6 shows an enlarged detail similar to that of Figure 5, for a further, alternative embodiment of the invention.

Referring to Figure 1, the island wound dressing 1 comprises a backing sheet 2 of microporous, semipermeable polyurethane foam coated with a layer 3 of medical- grade, pressure-sensitive polyurethane adhesive. The dressing 1 further comprises an absorbent layer 4. The layer 4 is a nonwoven carded web of viscose stable fibers. The dressing further comprises a wound facing sheet 5 of hydrophilic polyurethane foam approximately 1mm thick, prepared in accordance with EP-A-0541391. The porous foam layer 5 provides a hydrophilic, non- adherent and wound-friendly surface for application to the wound. Island wound dressings of this general type are commercially available from Johnson Johnson Medical Limited of Gargrave, UK, under the registered trademark TIELLE.

The novel features of the dressing according to the present invention include barrier regions 6 and 7 in the form of narrow strips extending across the absorbent sheet 4 approximately 3mm from opposed edges 8, 9 of the sheet. The barrier regions 6, 7 are produced by impregnating the absorbent sheet 4 in the barrier region with a hydrophobic silicone glue. Alternatively, the barrier regions can be applied directly to the backing sheet. The adhesive gel, or similar, is metered to a suitable nozzle, at a suitable flowrate and applied either to the absorbent layer or; to the backing sheet as it travels through the process. Alternatively the absorbent layer, or backing sheet, is held stationary whilst the nozzle, or similar applicator, is moved via an X - Y traverse system. The barrier regions make it possible for the edges 8, 9 of the absorbent sheet adjacent to the barrier regions to be coterminous with the edges of the wound facing sheet 5 on those opposed sides.

There is no leakage of wound fluid from edges 8, 9 of the absorbent layer because leakage of the wound fluid is blocked by barrier regions 6, 7.

It will be appreciated that the wound dressings shown in Figure 1 are especially easy to manufacture, because the absorbent island 4 can be formed from a continuous strip of the absorbent nonwoven fabric by applying the barrier regions 6, 7 transversely to the strip at intervals, followed by cutting the strip into pieces.

The strip of absorbent fabric may be laminated to a strip of the wound facing foam ] 5 sheet 5 before or aver the step of providing the barrier regions, and the laminated strips may then be cut at intervals to form the absorbent islands for application to the backing sheet 2. The islands are held in place on the backing sheet 2 by adhesion of the absorbent layer 4 and edges of the wound facing layer 5 to the adhesive 3 on the backing sheet 2.

The embodiment shown in Figure 2 comprises an adhesive-coated backing sheet 10, an absorbent sheet 11, and a hydrophilic polyurethane foam wound facing sheet 12, each having similar composition to the respective layers described in connection with Figure 1. The absorbent sheet 11 has a barrier region 13 similar to that of the embodiment shown in Figure 1, but extending around the whole of I the absorbent sheet proximate to the edges of the absorbent sheet 11. The barrier region 13 prevents leakage of absorbed wound exudate from the absorbent sheet 11 to all edges of the absorbent sheet 11. Consequently, the wound facing layer 12 in Figure 2 can be made coterminous with the absorbent sheet 11. That is to say, the wound facing layer is the same size and shape as the absorbent sheet and is superimposed upon the absorbent sheet 11 in alignment therewith.

Since the wound facing sheet 12 is no longer directly adhered to the backing sheet in the embodiment of Figure 2, it is indirectly adhered thereto by means of the hydrophobic silicone adhesive used to form the barrier region 13.

It will be appreciated that the embodiment of Figure 2 is especially easy to manufacture, by providing the barrier regions 13 in a continuous strip or sheet of the absorbent nonwoven fabric 11, laminating the wound facing sheet 12 onto the absorbent sheet 11 either before or after the step of forming the barrier regions, followed by cutting (e.g. die cutting) the laminate into the pieces having coterminous absorbent and wound facing sheets, and then adhering those pieces l0 to the adhesive-coated backing sheet 10. Alternatively, the barrier region 13 is applied to the backing sheet and the laminated pieces 11 & 12 are cut and applied to the backing. The barrier region 13 is permeates through 11 and 12 to bond the trilaminate dressing together.

IS The embodiment shown in Figures 3 to 5 is a so-called borderless dressing in accordance with the present invention. The borderless dressing 15 comprises a microporous, semipermeable polyurethane backing sheet 16 as described for the embodiment of Figures 1 and 2. The borderless dressing 15 further comprises a nonwoven textile absorbent layer 17 as described for the embodiments of Figures 1 and 2, but in the embodiment of Figure 3 the textile layer 17 is coterminous with the backing sheet 16. A barrier strip 18 of width about 3mm (multiple strips could be used) extends around all sides of the absorbent layer 17 a few millimeters from the edge of a dressing. The barrier layer 18 is formed from a hydrophobic silicone adhesive as previously described. An outer margin 19 of width about 3mm is defined in the absorbent layer by the barrier strips and extends all around the edges of the absorbent layer 17 outside the barrier region.

In this embodiment, a wound facing layer 20 of hydrophilic polyurethane foam as described above in connection with the embodiments of Figures 1 and 2 extends coterminously with the backing sheet 16 and the absorbent sheet 17.

Optionally, a margin 21 of medical-grade, pressure-sensitive polyurethane adhesive extends around the inside of the dressing 15 on the wound facing sheet 20. It can be seen from Figure 5 that the adhesive 21 is located above the barrier region 18 and the margin 19 of the absorbent layer. Since these regions remain dry during use of the dressing, the adhesive 21 retains its adherency when the dressing is in use on exuding wounds.

The embodiment shown in partial cross-section in Figure 6 is similar to that of Figures 3 to 5, except that the absorbent sheet 23 includes thermoplastic fibers, and the barrier region 24 has been formed by compressing and heating the absorbent layer 23 to form a compressed and bonded barrier region 24 of low I lO porosity that tends to block the flow of liquid towards the edges of the absorbent layer 23. Since the silicone adhesive 18 of the embodiments of Figures 3 to 5 is; no longer present, the embodiment of Figure 6 further comprises optional adhesive layers 25, 26 to bond the absorbent sheet 23 to the polyurethane backing sheet and the polyurethane foam wound facing sheet. Alternatively bonding of 20 to 23 could be a natural bond due to the adhesive nature of the materials used. Fixing of these 2 components could also be achieved through needling or other methods.

It will be appreciated that the borderless dressing embodiments of Figures 3 to 6 can be manufactured especially easily in continuous processes by laminating the t component layers and cutting out the borderless dressings from a continuous strip! or sheet. ! All of the above-described embodiments normally further comprise a release- t coated protective cover sheet or sheets over the wound facing surface and t adjacent adhesive surfaces of the dressing, to protect the surfaces prior to use.

The above embodiments have been described by way of example only. Many other embodiments falling within the scope of the accompanying claims will be apparent to the skilled reader.

Claims (13)

CLAIMS I

1. A wound dressing comprising an absorbent sheet, wherein the absorbent sheet comprises one or more barrier regions to block lateral transport of liquid through the absorbent sheet to an edge of the absorbent sheet.

2. A wound dressing according to claim 1, wherein the wound dressing further comprises a liquid permeable wound facing sheet over the absorbent sheet.

lO

3. A wound dressing according to any preceding claim, wherein the barrier region or regions extend substantially all around the absorbent layer to block liquid transport to substantially all edges of the absorbent layer.

4. A wound dressing according to claim 4, wherein the wound dressing further 3 l 5 comprises a liquid permeable wound facing sheet that is substantially coterminous with the absorbent layer.

5. A wound dressing according to claim 4 or 5, wherein the wound dressing further comprises a liquid impermeable backing sheet that is substantially coterminous with the absorbent layer.

6. A wound dressing according to any of claims 2 to 5, further comprises a layer of adhesive on a wound facing surface of the wound facing sheet.

7. A wound dressing according to any preceding claim, wherein the barrier region or regions comprise a hydrophobic material in the absorbent sheet or a region of low porosity in the absorbent sheet.

8. A wound dressing according to any preceding claim, wherein the barrier region or regions comprise an adhesive material extending through the absorbent layer to bond together the absorbent layer with a wound facing layer and a backing sheet.

9. A method of manufacture of a wound dressing comprising the steps of: providing a strip of absorbent material; forming a plurality of transverse barrier regions for blocking liquid flow through the absorbent material at intervals along the strip; laminating the strip of absorbent material to a strip of liquid permeable sheet material; and cutting the strip transversely at intervals to form a plurality of wound dressing laminated pieces.

l0 10. A method according to claim 9, further comprising forming at least one longitudinal barrier region in the absorbent strip, and further comprising cutting the strip longitudinally to form plurality of wound dressing laminated pieces having coterminous absorbent and liquidpermeable wound facing material layers.

11. A method according to claim 9 or 10, wherein said step of laminating comprises adhesive bonding between the absorbent sheet and the liquid permeable wound facing sheet.

12. A method according to any of claims 9 to 11, wherein the method further comprises applying each of said absorbent pieces to an adhesivecoated backing sheet such that the face of the absorbent sheet opposite the wound contacting sheet contacts the adhesive-coated backing sheet.

13. A method according to any of claims 9 to 11, wherein the method comprises laminating the strip of absorbent material and the strip of wound facing material to a strip of liquid impermeable backing sheet material prior to said step of cutting the strip transversely at intervals.