WOUND DRESSINGS

Abstract: A wound dressing (1) comprising a wound covering element (2) provided with adhesive on a face thereof. In a marginal region (3) of said face, extending around the periphery of the element, the percentage of adhesive coverage is greater than in a central region of the face bounded by the marginal region (3). The percentage coverage in said marginal region (3) is greater than 20 % of the area of said marginal region and the percentage coverage in said central region is a maximum of 50 % of the area of the central region.

Description: WOUND DRESSINGS The present invention relates to wound dressings. Wound dressings frequently comprise a wound covering component (e.g. a synthetic polymeric film or membrane) and an adhesive for locating the wound covering component in position on a wound. The wound covering component may be intended to be located in direct contact with the wound or to locate a further dressing component (e.g. a hydrogel or an alginate) in position between itself and the wound. The wound covering element will not only cover the wound itself but at its marginal edges will overlie-, and be adhered to. the intact skin surrounding the wound so as to locate the element in place. Conventional wound covering elements are generally provided with a uniform amount of adhesive (provided as a continuous or discontinuous layer) across the entire face of the covering element. In other words, the amount per unit area of adhesive is constant across the surface ofthe wound covering element. " We are however of the view that such uniform amounts are not appropriate to the areas ofthe intact skin and the area ofthe covering element overlying the wound. Thus, for example, a uniform amount which is sufficiently high to allow for secure attachment of the wound covering element to intact skin around the wound may not be appropriate for the area of the element covering the wound itself. Similarly an amount of adhesive appropriate for the area of the element covering the wound may not provide the required degree of securement ofthe element to intact skin. It is an object of the invention to obviate or mitigate the above mentioned disadvantages. According to the present invention there is provided a wound dressing comprising a wound covering element provided with adhesive on a face thereof wherein in a marginal region of said face extending around the periphery of the element the percentage of adhesive coverage is greater than in a central region ofthe face bounded by the marginal region, the percentage coverage in said marginal region is greater than 20% ofthe area of said marginal region and the percentage coverage in said central region being a maximum of 50% o the area of said central region. Therefore in the dressing of the invention there is a marginal edge region of the wound covering element having a greater amount of adhesive coverage than in the central region. This marginal region is used for secure fixing of the wound covering element to intact skin around the wound whereas the lower amount of adhesive coverage in the central area is more beneficial for the area over the wound. Within the marginal region, the adhesive coverage may be continuous (100% coverage) or discontinuous (so as to give greater than 20% but less than 100% coverage). Preferably the adhesive coverage in the marginal region is at least 30%, more preferably 50% to 80%. Preferably the marginal region extends inwardly of the peripheral edge of the wound covering element by a distance of 0.5 to 2cm, more preferably 0.75 to 1.25cm. In the central region of the wound covering element the adhesive is provided as a discontinuous layer so as to provide an overall coverage, in the central region, of less than 50%, more preferably less than 40%. e.g. less than 30%. Thus for example the coverage in the second region may be less than 20%. The wound covering element may be one which is intended to be located in direct contact with the wound or to locate a further component between itself and the wound. If the wound covering element is to be in direct contact with the wound, then it is preferred that the adhesive in the central region of the element is provided as lines of adhesive defining a number of cells in which there is no adhesive at all. In a preferred embodiment of this arrangement, the lines of adhesive define hexagonal cells arranged in a honeycomb pattern. It is not however essential that the individual cells be hexagonal since other configurations are possible, e.g. quadrilateral shaped cells. Thus it is possible for the adhesive in the central region to be provided as a cross-hatch pattern. A further possibility is for the cells to be square. The advantage of having such a pattern of lines defining cells is that, for those areas where the covering element contacts the wound, cell growth is promoted. If however the central region of the wound covering element is intended to locate a further dressing component (e.g. a hydrogel or an alginate) in position, then it is preferred that the adhesive in the central region of the element is provided as a plurality of concentric rings, e.g. circles, ovals and the like, (and possibly also part- rings) centred on the mid-point of the central area of the covering element. Such concentric rings provide for control of exudate flow from the wound. For preference the spacing between the rings (or part rings) decreases in a direction going away from the mid-point ofthe covering element. The wound covering element may be a membrane or, more preferably, a film. The film is preferably a breathable film which is of increased MVTR capability in the presence of liquid water as compared to moisture vapour only. MVTR in the presence of liquid water may be measured by ASTM E96BW whereas MVTR in the presence of moisture vapour alone may be measured by ASTM E96B. Preferably the value ofthe breathability in the presence of liquid water is at least twice and preferably at least three times that in the presence of moisture vapour alone. The value may be up to 10 or 20 times that for moisture vapour alone. Typically .the film will be of a material which has an MVTR in the presence of moisture vapour alone (ASTM E96B) of 1,000 to 5,000 g m "2 24 hr *1 and an MVTR in the presence of liquid water (ASTM E96BW) in the range 3.000 to 30,000 g '2 24hr "1 . Typically the film will have a thickness of 20-70 microns more preferably 30-50 microns, e.g. about 40 microns. The film may for example be of polyurethane. Examples of suitable films are available from Innovative Technologies Limited under designations B53-2, C54-2, D56-2. The adhesive is preferably a pressure sensitive adhesive. Obviously the adhesive will be a medically acceptable adhesive. An example of a suitable adhesive is a pressure sensitive adhesive available from Innovative Technologies under the designation IT PSA HT or PSA LT. The invention is further described by way of example only with reference to the accompanying drawings, in which: Fig 1. illustrates one embodiment of wound dressing in accordance with the invention viewed from the adhesive side thereof; and Fig 2. illustrates a second embodiment of wound dressing in accordance with the invention again viewed from the adhesive side thereof. Referring to Fig. 1, the illustrated dressing 1 comprising a moisture permeable film 2 provided on one face thereof (i.e. the face seen in Fig. 1) with an adhesive laid down in two distinct areas. A first area of adhesive is provided at the marginal edge regions 3 extending around the periphery of the. film 2. In these regions 3, the adhesive is provided at a coverage of greater than 20%, e.g. 50% upwards. The other region of adhesive is that area ofthe film 1 bounded by the marginal edge regions 3 which is intended to come into direct contact with a wound. In this central area, the adhesive is provided in lines 4 defining hexagonal cells 5 in a honeycomb pattern. The dressing illustrated in Fig. 1 is suitable for treatments in which the central region is in direct contact with the wound since the honeycomb pattern in the central region promotes cell growth. Referring now to Fig. 2, the dressing 20 illustrated therein includes adhesive laid down at a marginal region 21 extending around the periphery of the dressing. In this marginal region, the adhesive is provided at a coverage of > 20%, e.g. 50%. In the central region of the dressing, the adhesive is provided as concentric circles 22 and part-circles 23 centred on the mid-point of the central region. There is no adhesive coverage between adjacent circles 22 or part circles 23 so that in the central region the overall coverage is less than 20%. The circles and part circles are of decreasing spacing going in the radial direction away from the centre ofthe dressing. The dressing illustrated in Fig. 2 is particularly suitable for location of a further dressing component (e.g. a hydrogel or alginate) between itself and the wound. The concentric circles are effective for prevention of exudate leakage.

Claims: CLAIMS 1. A wound dressing comprising a wound covering element provided with adhesive on a face thereof wherein in a marginal region of said face extending around the periphery of the element the percentage of adhesive coverage is greater than in a central region of the face bounded by the marginal region, the percentage coverage in said marginal region is greater than 20% of the area of said marginal region and the percentage coverage in said central region being a maximum of 50% of the area of said central region. 2. A dressing as claimed in claim 1 wherein, in the marginal region, the adhesive coverage is at least 30%. 3. A dressing as claimed in claim 2 wherein, in the marginal region, the adhesive coverage is 50%-80%. 4. A dressing as claimed in any one of claims 1 to 3 wherein the marginal region extends inwardly of the peripheral edge of the wound covering element by a distance of0.5 to 2cm. 5. A dressing as claimed in claim 4 wherein the marginal region extends inwardly of the peripheral edge of the wound covering element by a distance of 0.75 to 1.25 cm. 6. A wound dressing as claimed in any one of claims 1 to 5 wherein in the central region the percentage of adhesive coverage is less than 40%. 7. A wound dressing as claimed in claim 6 wherein in the central region the percentage of adhesive coverage is less than 30%. 8. A wound dressing as claimed in claim 7 wherein in the central region the percentage of adhesive coverage is less than 20%. 9. A dressing as claimed in claim 8 wherein in the central region of the wound covering element the adhesive is provided at an overall coverage of 10%-20%. 10. A dressing as claimed in any one of claims 1 to 9 wherein in the central region of the element the adhesive is provided as lines defining a plurality of cells. 11. A dressing as claimed in claim 10 wherein the cells are hexagonal and arranged in a honeycomb pattern. 12. A dressing as claimed in any one of claims 1 to 9 wherein the adhesive in the central region of the element is provided as a plurality of concentric rings (and possibly also part-rings) centred on the mid point on the central area of the covering element. 13. A dressing as claimed in any one of claims 1 to 12 wherein the wound covering element is a breathable film. 14. A dressing as claimed in any one of claims 1 to 12 wherein the covering element is a membrane.

Inventors: DIXON SIMON ASHLEY, GILDING DENIS KEITH, DIXON, SIMON, ASHLEY, GILDING, DENIS, KEITH
Applicants: DIXON SIMON ASHLEY, GILDING DENIS KEITH, INNOVATIVE TECH LTD, DIXON, SIMON, ASHLEY, GILDING, DENIS, KEITH, INNOVATIVE TECHNOLOGIES LIMITED
Application year: 1996
Main classification: A61F13
IPC codes: A61F13