DRESSINGS FOR EXTENDED WEAR

Abstract: The invention provides an adhesive dressing comprising: an adhesive-coated backing sheet having one or more straight edges; and an absorbent island adhered to the backing sheet by the adhesive, wherein the absorbent island has an elongated shape with a long axis oriented at an oblique angle to at least one straight edge of the backing sheet. The relative orientation of the island and the backing sheet provides extended wear time for dressing when it is applied to common wounds.

Description: DRESSINGS FOR EXTENDED WEAR The present invention relates to dressings for extended wear, and in particular to wound dressings for extended wear. It is known to provide so-called island dressings for the treatment of a wide variety of wounds, including chronic wounds and ulcers. Island dressings are also used in stoma care and in patches for transdermal administration of active agents. The island dressings typically comprise an adhesive-coated backing sheet having an absorbent island of smaller size centered on the backing sheet and adhered thereto by the adhesive. An adhesive-coated margin of the backing sheet extends around the island to secure the dressing to the skin of the patient around the area to be treated. The adhesive island is normally of symmetrical shape, such as round, square or rectangular, and is fully oriented with a similarly symmetrical backing sheet shape. The center of gravity of the absorbent island is centered on the center of gravity of the backing sheet. Many common wounds such as sacral ulcers or surgical incisions are aligned with an axis of the trunk or limbs of a patient. As a result, island dressings are normally applied to these wounds with the straight edges of the typical rectangular backing sheet aligned parallel or perpendicular to an axis of the trunk or limb. The present invention is based on the principle devised by the present inventors that extended wear times can be achieved by providing a dressing in which the island is rotated out of alignment with the backing sheet, whereby the backing sheet is out of alignment with the axes of the body when the dressing is applied correctly with the island covering the area to be treated. The dressings according to the present invention are also easy to apply to certain areas of the body, and can provide enhanced protection against leakage of liquids such as wound fluid. The present invention provides an adhesive dressing comprising: an adhesive- coated backing sheet having one or more straight edges; and an absorbent island adhered to the backing sheet by the adhesive, wherein the absorbent island has an elongated shape with a long axis oriented at an oblique angle to least one straight edge of the backing sheet. Preferably, the backing sheet has two straight edges that are substantially parallel. For example, it may be in the shape of a polygon, a rhombus or a trapezium. More preferably, the backing sheet is substantially rectangular, and it may be square. The absorbent island is elongated. That is to say it has a long axis, which is preferably also an axis of symmetry, and a short axis perpendicular to, and significantly shorter than, the long axis. The aspect ratio of the absorbent island, defined as the ratio of the longest axis to the shortest perpendicular axis, is preferably at least 1.25, and more preferably at least 1.5. Preferably, the absorbent island is rectangular, oval, lozenge shaped, or elliptical. More preferably, the absorbent island is substantially rectangular. Preferably, the long axis of the absorbent island is oriented at an angle of from 25° to 65° to the straight side of the backing sheet. More preferably, the long axis of the absorbent island is oriented at an angle of from 35° to 55° to the straight side of the backing sheet, and most preferably it is oriented at about 45° to the straight side of the backing sheet. In particularly preferred embodiments, the backing sheet is substantially rectangular, the absorbent island is substantially rectangular, and the long axis of the absorbent island is substantially aligned with a diagonal of the backing sheet. In certain preferred embodiments of the invention, the centre of gravity of the absorbent island is offset from the centre of gravity of the backing sheet. For example, the center of gravity of the absorbent island may be displaced along a diagonal of the backing sheet. The area of the absorbent layer is typically in the range of from 1cm 2 to 200cm 2 , more preferably from 4cm 2 to 100cm 2 . The adhesive-coated margin around the absorbent layer preferably has a mean width of from 0.5 to 5 cm, preferably from 1 to 3 cm. The absorbent island may comprise any of the layers conventionally used for absorbing wound fluids, serum or blood in the wound healing art, including gauzes, nonwoven fabrics, superabsorbents, hydrogels and mixtures thereof. Preferably, the absorbent island comprises a layer of absorbent foam, such as an open celled hydrophilic polyurethane foam prepared in accordance with EP-A- 0541391 , the entire content of which is expressly incorporated herein by reference. In other embodiments, the absorbent island may comprise a layer of a nonwoven fibrous web, for example a carded web of viscose staple fibers. The basis weight of the absorbent layer may be in the range of 50-500g/m 2 , such as 100-400g/m 2 . The uncompressed thickness of the absorbent layer may be in the range of from 0.5mm to 10mm, 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 absorbent island may comprise a layer of such absorbent material enclosed or covered by a liquid-permeable film or sheet, such as a perforated thermoplastic film. The backing layer supports the absorbent island and preferably provides a barrier to passage of microorganisms through the dressing. Preferably, the backing layer is substantially liquid-impermeable. The backing layer is preferably semipermeable. That is to say, the backing layer is preferably permeable to water vapour, but not permeable to liquid water or wound exudate. Preferably, the backing layer is also microorganism-impermeable. Suitable continuous conformable backing layers will preferably have a moisture vapor transmission rate (MVTR) of the backing layer alone of 300 to 5000 g/m 2 /24hrs, preferably 500 to 2000 g/m 2 /24hrs at 37.5 °C at 100% to 10% relative humidity difference. The backing layer thickness is preferably in the range of 10 to 1000 micrometers, more preferably 100 to 500 micrometers. Suitable polymers for forming the backing layer include polyurethanes and poly alkoxyalkyl acrylates and methacrylates such as those disclosed in GB-A- 1280631. Preferably, the backing layer comprises a continuous layer of a high density blocked polyurethane foam that is predominantly closed-cell. A suitable backing layer material is the polyurethane film available under the Registered Trade Mark ESTANE 5714F. Also suitable are elastomeric polymeric esters such as Du Pont HYTREL (Registered Trade Mark). The adhesive should preferably be moisture vapor transmitting and/or patterned to allow passage of water vapor therethrough. The adhesive layer is preferably a continuous moisture vapor transmitting, 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, polyvinyi ethyl ether and polyurethane as described for example in GB-A-1280631. The basis weight of the adhesive layer is preferably 20 to 250 g/m 2 , and more preferably 50 to 150 g/m 2 . Polyurethane-based pressure sensitive adhesives are preferred. Preferably, the island dressing according to the present invention further comprises at least one removable cover sheet to cover the absorbent island and the adhesive coated margin of the backing sheet around the absorbent island. The cover sheet covers and protects the absorbent island and prevents premature adhesion of the adhesive layer. The cover sheet is removed by the care giver immediately before application of the dressing. The cover sheet may comprise a film of polyethylene, polypropylene or fluorocarbons and papers coated with these materials. Preferably, the cover sheet is a release-coated paper sheet, such as a silicone release-coated paper sheet. Examples of silicone-coated release papers are POLYSLIK (Registered Trade Mark) supplied by H.P. Smith & Co., offered in various formulations to control the degree of adhesion of the paper to the adhesive surface. Preferably, the dressing comprises a first removable cover sheet having a first edge and a second removable cover sheet that meets the first cover sheet along the first edge, wherein the first edge extends obliquely to at least one straight edge of the backing sheet. The directional alignment of the cover sheet edges can be helpful to assist the care giver in achieving accurate alignment of the absorbent layer with the area to be treated. For this reason, preferably at least one of the edges along which the cover sheets meet is substantially straight. Certain preferred dressings have a central cover sheet with first and second opposed edges, and two side cover sheets that meet the central cover sheet along the opposed edges, wherein the opposed edges extend obliquely to at least one straight edge of the backing sheet. Preferably, the opposed edges are substantially parallel. This arrangement of three cover sheets is especially suitable for positioning of relatively large dressings, such as sacral dressings, as described in detail in EP-A-0117632, the entire content of which is incorporated herein by reference. Preferably, along each of said edges where the cover sheets meet, one of the cover sheets is folded back to provide a folded-back margin, and the other cover sheet overlaps the said folded-back margin. This provides an easy-to-grasp margin on each cover sheet in the region of overlap to assist removal of the cover sheets by the care giver. In the case of the embodiment comprising three cover sheets described above, each side cover sheet is preferably folded back along each of said edges where the cover sheets meet to provide a folded-back margin, and the central cover sheet overlaps the said folded-back margin, preferably as described in EP-A- 0117632. Preferably, at least one of the edges along which the cover sheets meet is substantially parallel or perpendicular to the long axis of the island. This enables the care giver to orient the absorbent island in position by reference to the cover sheets without reference to the backing sheet. This is especially useful when the backing sheet is not transparent or translucent. In particularly preferred embodiments: the backing sheet is substantially rectangular; the absorbent island is substantially rectangular, and the long axis of the absorbent island is oriented substantially diagonally to the backing sheet; and at least two cover sheets are provided that meet along an edge that extends substantially diagonally to the backing sheet and substantially perpendicular or parallel to the long axis of the absorbent island. The term "substantially diagonally" as used herein signifies an orientation substantially parallel, though not necessarily coincident with, a diagonal of the backing sheet. For example, the orientation may preferably be within 20° of the diagonal, more preferably within 10° of the diagonal, defined as a line draw between opposite vertices of the backing sheet. Preferably, the adhesive dressing according to the present invention is a sacral dressing. Preferably, the adhesive dressing according to the present invention is sterile and sealed in a microorganism-impermeable package. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a bottom plan view of the dressing with the cover sheets in place; and Figure 2 shows a bottom plan view of the dressing with the cover sheets removed. Referring to Figure 1, the wound dressing 1 is an island-type self-adhesive wound dressing comprising a backing layer 2 of microporous liquid-impermeable polyurethane foam, such as ESTANE 5714F (Registered Trade Mark). The backing layer is permeable to water vapor, but impermeable to wound exudate and microorganisms. The backing layer 2 is coated with a substantially continuous layer 3 of pressure- sensitive polyurethane adhesive. An absorbent island 4 is adhered to a central region of the adhesive-coated backing sheet 2. The absorbent island 4 comprises a highly absorbent layer 6 covered by a wound contacting top layer 5 that extends over and beyond the edges of the highly absorbent layer 6 so that edges 7 of the top layer 5 are adhered to the adhesive layer and enclose the highly absorbent layer 6. The top layer is formed of hydrophilic polyurethane foam prepared as described in EP-A-0541391 and having a basis weight of about 350g/m 2 and a thickness of about 1.5 mm. The highly absorbent layer 6 is formed from a nonwoven fabric of mixed viscose and superabsorbent fibers sold under the registered trade mark OASIS. The wound facing surface of the dressing shown in Figure 1 is protected by three silicone-coated release papers 9,10,11. Release papers 10 and 11 extend obliquely from opposite corners of the backing sheet and each cover approximately 25% of the dressing area. Flaps 12,13 of the cover sheets 10, 1 are folded back along the substantially parallel substantially straight edges of the release paper 10, these edges extending obliquely across the lower surface of the island dressing in line with the sides of the rectangular absorbent island. Intermediate the release papers 10 and 11 is a central release paper 9 which covers approximately 50% of the surface area o the film and is provided on opposed sides with edge flaps that overlap the folded-back edge flaps 12,13 of the release papers 10,11. The dressing is packaged in a microorganism-impermeable pouch (not shown), and sterilised using gamma radiation. In use, the dressing is removed from the pouch and may then be cut to size or cut to shape for a particular application or a particular patient. The central release paper 9 is then removed and discarded by the care giver preparatory to applying the dressing. The dressing is grasped by the opposed corners still covered by the release papers 10,11 and the central region of the dressing is then adhered over the area to be treated. The orientation of the release papers 10,11 provides a sensory guide to enable the care giver to apply the dressing with the absorbent island in the desired orientation, even though the island may not be visible through the backing sheet. Once the center portion of the dressing has been secured, the release paper of each opposed corner is removed in turn by grasping the end flaps 12,13 and withdrawing the release paper while pressing downward on the backing sheet to secure the adhesive attachment of the end portion to the patient. The above embodiment has 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: CLAIMS 1. An adhesive dressing comprising: an adhesive-coated backing sheet having one or more straight edges; and an absorbent island adhered to said backing sheet by said adhesive, wherein the absorbent island has an elongated shape with a long axis oriented at an oblique angle to least one straight edge of the backing sheet. 2. An adhesive dressing according to claim 1 , wherein the backing sheet has two straight edges that are substantially parallel. 3. An adhesive dressing according to claim 2, wherein the backing sheet is substantially rectangular. 4. An adhesive dressing according to any preceding claim, wherein the absorbent island is substantially rectangular. 5. An adhesive dressing according to any preceding claim, wherein the island has an aspect ratio of at least 1.25. 6. An adhesive dressing according to any preceding claim, wherein the long axis of the absorbent island is oriented at an angle of from 25° to 65° to the straight side of the backing sheet. 7. An adhesive dressing according to claim 6, wherein the long axis of the absorbent island is oriented at an angle of from 35° to 55° to the straight side of the backing sheet 8. An adhesive dressing according to claim 1 , wherein the backing sheet is substantially rectangular, the absorbent island is substantially rectangular, and the long axis of the absorbent island is aligned with a diagonal of the backing sheet. 9. An adhesive dressing according to any preceding claim, wherein the centre of gravity of the absorbent island is offset from the centre of gravity of the backing sheet. 10. An adhesive dressing according to any preceding claim, further comprising at least one removable cover sheet to cover the absorbent island and the adhesive coated margin of the backing sheet around the absorbent island. 11. An adhesive dressing according to claim 10, comprising a first removable cover sheet having a first edge and a second removable cover sheet that meets the first cover sheet along the first edge, wherein the first edge extends obliquely to at least one straight edge of the backing sheet. 12. An adhesive dressing according to claim 10, comprising a central cover sheet having first and second opposed edges, and two side cover sheets that meet the central cover sheet along the opposed edges, and wherein the opposed edges extend obliquely to at least one straight edge of the backing sheet. 13. An adhesive dressing according to claim 12, wherein the opposed edges are substantially parallel. 14. An adhesive dressing according to any one of claims 10 to 13, wherein at least one of the edges along which the cover sheets meet is substantially straight. 15. An adhesive dressing according to any one of claims 10 to 13, wherein, along each of said edges where the cover sheets meet, one of the cover sheets is folded back to provide a folded-back margin, and the other cover sheet overlaps the said folded-back margin. 16. An adhesive dressing according to claim 12 or 13 wherein, along each of said edges where the cover sheets meet, the side cover sheet is folded back to provide a folded-back margin, and the central cover sheet overlaps the said folded-back margin. 17. An adhesive dressing according to any one of claims 11 to 16, wherein at least one of the edges along which the cover sheets meet is substantially parallel or perpendicular to the long axis of the island. 18. An adhesive dressing according to claim 1 , wherein: the backing sheet is substantially rectangular; the absorbent island is substantially rectangular, and the long axis of the absorbent island is aligned substantially diagonally to the backing sheet; at least two cover sheets are provided that meet along an edge that extends substantially diagonally to the backing sheet and substantially perpendicular or parallel to the long axis of the absorbent island. 19. An adhesive dressing according to any preceding claim which is a sacral dressing. 20. An adhesive dressing according to any preceding claim which is sterile and sealed in a microorganism-impermeable package. 21. An adhesive dressing substantially as hereinbefore described with reference to the accompanying drawings.

Inventors: KIRKWOOD ANDREW JAMES, KIRKWOOD, ANDREW, JAMES
Applicants: JOHNSON & JOHNSON MEDICAL LTD, KIRKWOOD ANDREW JAMES, JOHNSON & JOHNSON MEDICAL LIMITED, KIRKWOOD, ANDREW, JAMES
Application year: 2001
Main classification: A61F13
IPC codes: A61F13, A61L15