GB2308308A - Metal detectable wound dressing - Google Patents

Abstract

A metal detectable wound dressing comprises a backing layer 10 with an adhesive coating 11, an absorbent pad 13 and a metal detectable means between the pad and the adhesive layer. To enable X-ray detection, an iron loaded film layer may be disposed on the backing, attached to the absorbent pad by means of a pressure sensitive adhesive. Alternatively, a tungsten loaded adhesive material and/or the iron loaded film may be used. Induction detectable means may comprise an aluminium foil layer, between the iron loaded film and tungsten loaded adhesive layers. Providing the thin backing layer, enables the detectable dressing to be both conformable and breathable, thus enabling good adhesion.

Description

DETECTABLE DRESSING The present invention relates to detectable tapes, eg. for contaminant discrimination by metal or x-ray detection equipment in manufacturing industries such as the food industry. The present invention is particularly applicable to industries employing automated detection processes operating at fast manufacturing process line speeds.

Dressings, and first aid dressings in particular, wom by personnel employed in food manufacturing industries are potential contaminants and there has therefore long been a need for such dressings to be detectable. Contaminant discrimination equipment advantageously can include ferrous and non ferrous metal detectors, x-ray equipment and electrical induction detection systems.

British Patent No. 1381855 describes dressings which may be screened by a metal detector. Such dressings comprise a backing material of microporous polyvinyl chloride having a pressuresensitive adhesive on one surface thereof, with an electromagnetically detectable particulate ferrous material incorporated in the backing material. Dressings of this type are usually coloured bright blue to enable them to be detected visually and are commonly used as first-aid dressings for workers in the food industry.

One problem with such dressings is that they are less conformable and breathable than many newer types of dressing available currently. The conformability of a dressing has a direct effect on the ability of the dressing to adhere effectively to the body and so it is advantageous to use relatively conformable films in wound dressings. The incorporation of iron powder in the backing material tends to limit the materials which can be used for the backing layer and thus the physical properties of the dressing are also limited.

It is an object of the present invention to provide a metaldetectable dressing which overcomes some of the above problems.

According to the invention, a dressing comprises a backing layer having upper and lower surfaces, an adhesive layer over the lower surface of the backing layer, an absorbent pad located on the adhesive coated side of the backing layer and a metal-detectable material which is located between the wound facing surface of said pad and said adhesive layer. In this way, the material of the backing layer may be selected from a wide range of materials which are conventionally usedfor dressing manufacture.

The backing layer is selected from the wide range of materials which are conventionally used in wound dressings. Examples of suitable materials include woven or non-woven fabrics, polymeric films such as polyurethanes. The backing layer is preferably a conformable elastomeric polymer film which is preferably relatively thin, e.g. less than about 1 00zm in thickness. The backing layer is very preferably breathable i.e. it preferably has a moisture vapour transmission rate of greater than 250gmday" at 370c and 10% relative humidity, measured by the Payne Cup method described hereinafter. Suitable materials for forming the backing layer include those described in United Kingdom Patent No. 1280631, European Patents Nos. 51935, 91800 and 178740.Particularly apt materials are polyurethanes, for example polyester or polyether polyurethanes sold under the ESTANE trade mark. Other-apt materials are elastomeric polyether polyesters, for example those sold as HYTREL (trade mark) and polyether polyamides, for example those known as PEBAX (trade mark). Other favoured materials include hydrophilic polymers such as hydrophilic polyurethanes including those described in United Kingdom Patent No. 20931 90B, especially the polyurethane described in Example 1 therein.

The preferred backing layer materials are breathable. The backing layer may be transparent or may be opaque and coloured.

For example a film material may contain a pigment, pacifier and/or dye or may be printed with a coloured, opaque layer. A dressing for use in the food industry may be coloured blue by any of the above methods.

The moisture vapour transmission rate of the materials employed in the present invention may be measured by a procedure known as the Payne Cup method. The method uses a cup 1.5cm deep with a flanged top. The inner diameter of the flange is such to provide an area for moisture vapour transmission of 10cm2. In this method 1 Oml of distilled water is added to the cup and a sample of the material under test, large enough to completely cover the flange, is clamped over the cup. The complete assembly is then weighted and placed in a cabinet where the temperature and relative humidity are maintained at 370c and 10% respectively. After 17 hours the cup is removed from the cabinet and allowed to cool at room temperature.After re-weighing, the mass of water lost by vapour transmission is calculated and the result expressed as in glum2124 hrs at 370c at 100% to 10% relative humidity difference.

The backing layer is coated over one surface with a layer of adhesive which is skin-compatible and preferably pressuresensitive. Suitable pressure-sensitive adhesive compositions include polyvinyl alkyl ether adhesive and acrylate ester copolymer adhesives. Suitable adhesives are described in GB-A-1280631, EP-A-35399 and EP-A-51 935. Preferably the adhesive is a polyvinyl ether adhesive or an acrylate ester copolymer adhesive formed by the copolymerisation of 2-ethylhexyl acrylate, butyl acrylate and acrylic acid.

The dressing preferably comprises an absorbent pad which may be located approximately centrally on the adhesive layer. The pad is preferably of such a size that it is surrounded by adhesive material so that the dressing may be adhered to the skin all around the pad. The absorbent pad may be formed from any suitable absorbent material which is suitable for medical use. Preferably the pad is non adherent to the surface of a wound. A suitable absorbent pad may be formed from the non-adherent absorbent dressing material sold under the trade mark MELOLIN by Smith and Nephew Healthcare Limited. The pad may, optionally, be impregnated with an antibacterial compound or other medicament.

The dressing may also comprise a support layer to provide support for a thin film backing layer during application of the dressing so that it can be handled easily and applied with minimal risk of rucking or creasing. The support layer is preferably a relatively stiff polymeric film formed of e.g. polypropylene, polyester or a laminate construction. The support film is preferably transparent. The support layer is releaseably attached to the nonadhesive side of the backing layer by e.g. a weak or peelable adhesive or by static charge so that it can be removed from the backing layer when the dressing has been adhered to the skin of the patient.

The metal detectable material may be in the form of a strip, foil, particles or other piece or pieces. The metal detectable material is preferably detectable by electromagnetic detection means, and is most preferably a ferrous compound such as iron metal. In one form the metal detectable material is a polymeric film such as polyvinyl chloride which has iron powder incorporated within it. One such film has hitherto been used as a backing layer for a detectable dressing and comprises a microporous polyvinyl chloride film having an electromagnetically detectable particulate ferrous material incorporated within the film and a pressuresensitive adhesive coated on one side, as-described in GB1381855.

A suitable such film is obtainable from Porvair Plc and sold as KYRODERM (trade mark).

The detectable material is located between the wound-facing surface of the pad and the adhesive layer of the backing material. It may therefore be adhered to the backing layer or it may be contained within the absorbent pad.

The dressing may additionally contain material to enable it to be detected by different detection means. One form of the dressing may be x-ray detectable, in addition to being metal-detectable. This is preferably achieved by incorporating tungsten in the dressing, tungsten being a good absorber of x-rays. The tungsten may be added to the backing layer or to the adhesive layer as a powder but it is preferred to apply the material as a strip so that it can be present in an effective thickness. In a particularly preferred form1 the tungsten powder is dispersed in a carrier material, which is advantageously an adhesive material. The carrierltungsten mixture may then be applied in a narrow strip across the length of the dressing. The strip is preferably applied to the dressing in the region of the absorbent pad.

A further embodiment of the dressing may be inductiondetectable. One form of this embodiment incorporates aluminium metal in the dressing as a thin foil. Altematively particles of aluminium or other suitable metal may be incorporated into the backing layer or into the pressure-sensitive adhesive layer.

However, it is preferred that the metal is present in the region of the absorbent pad so that the properties of the backing layer are unaffected over the remaining part of the dressing. Another alternative is to incorporate the aluminium powder in a carrier material and apply the carrier/aluminium as described above. The carrier could also incorporate a second metal such as tungsten.

The invention will now be further described, by way of example only, with reference to the accompanying drawings which are: Fig 1 a longitudinal section through one form of dressing according to the invention and Fig 2 a longitudinal section through a second embodiment.

The drawings are schematic and not to scale.

The dressing shown in Fig 1 comprises a backing layer of a transparent conformable elastomeric breathable polyurethane film 10 coated on its lower surface with a layer of pressure-sensitive, skin-friendly adhesive 11. A support layer 12 of polypropylene film which is relatively stiff compared with the polyurethane film 10 is lightly adhered to film 10 by means of the static charge between the two films. Film 12 extends beyond one edge of film 10 to enable it to be removed easily when required. An absorbent pad 13 is provided in the central region of the dressing. Between pad 13 and adhesive 11 is a layer 14 of blue pigmented porous pvc film containing iron powder dispersed throughout the film and coated with pressure-sensitive adhesive 16. An adhesive protector layer 15, comprising a release-coated paper material is adhered over the adhesive.

The blue iron-filled layer 14 enables the dressing to be detected by electromagnetic detection equipment and also to be visually detected because, in use, the blue colour of layer 14 is visible through the transparent film 10. If the area of layer 14 is thought to be too small for easy visual detection, e.g. for small dressings then the backing layer 10 may be printed blue or patterned to increase the area of blue material present. In this case the coloured material applied to the upper surface of film 10 should preferably be selected to be breathable or printed in such a way as to leave parts of film 10 free of coloured material.

The dressing is used by first removing the protector layer 15 and then securing the dressing to the skin over a wound by means of the adhesive 11. The support layer 12 is removed when the dressing has been applied.

Fig 2 shows an altemative embodiment. The dressing comprises a backing layer 20 of a fabric material having a pressuresensitive adhesive 21 on its lower surface. A pad 22 comprises a non-woven absorbent material 23, a strip of tungsten powder loaded adhesive material 24, a layer of aluminium foil 25 and a layer of adhesive-coated pvc film 26 filled with iron powder. The layers 2326 are covered by a net material 27 which has low adherency to wounds. The pad 22 is adhered to the adhesive layer 21 approximately centrally. Adhesive protector layer 28 is formed in two parts 28a and 28b to assist removal from the dressing when required.

The pad 22 is manufactured by adhering the foil layer 25 to the adhesive layer 28 of pvc film 26. Adhesive carrier 24 containing tungsten powder is then applied to the foil 25 and a layer of nonwoven absorbent material 23 laid over the other layers. The pad is then wrapped in a non-adherent net material 27.

The tungsten-loaded carrier strip 24 provides a means for the dressing to be detected by x-ray detection equipment. The aluminium foil 25 enables the dressing to be detected by induction methods. The iron present in layer 26 provides electromagnetic detectability.

These examples show that the feature of providing electromagnetically detectable material in the region of the absorbent pad allows the backing layer of the dressing to be made from any suitable material. Thus, a modern conformable and breathable film or a traditional fabric may be used to form the backing layer of the dressing. The combination of detectable materials shown in Fig 2 may of course be used as a pad for a dressing having a thin polyurethane backing film, as shown in Fig 1.

Claims (10)

1. A dressing comprising a backing layer having upper and lower surfaces, an adhesive layer over the lower surface of the backing layer, an absorbent pad located on the adhesive-coated side of the backing layer and a metal-detectable material which is located between the wound-facing surface of said pad and said adhesive layer.

2. A dressing as claimed in claim 1 wherein said backing layer is a conformable, breathable film of a polymeric material.

3. A dressing as claimed in either claim 1 or claim 2 wherein said metal detectable material comprises a metal strip, foil, particles or pieces.

4. A dressing as claimed in either claim 1 or claim 2 wherein said metal detectable material comprises a polymeric film having iron powder incorporated within it.

5. A dressing as claimed in any of the preceding claims, further comprising means to enable it to be detected by x-ray detection equipment.

6. A dressing as claimed in claim 5 wherein said means comprises tungsten.

7. A dressing as claimed in claim 6 wherein said means comprises tungsten powder dispersed in a carrier material.

8. A dressing as claimed in any preceding claim, further comprising induction-detectable means.

9. A dressing as claimed in claim 8 wherein said means comprises aluminium metal.

10. A dressing as hereinbefore described with reference to and as shown in the accompanying drawings.