WOUND DRESSINGS, AND YARN USEFUL THEREIN

Abstract

Described herein are wound dressings, methods for their production and components for use therein. Described herein are a knitted structure including a blend of gelling fibres and non-gelling fibres wherein the yarn includes at least 50% w/w gelling fibres, a three-dimensional textile material including gelling fibres, and a yarn including a blend of gelling and non-gelling fibres which may be used in their production, the knitted structure and three-dimensional textile material being suitable for use as wound dressings or as components of composite wound dressings. The wound dressings may be adapted for use in negative pressure wound therapy (NPWT). It has been found that the incorporation of gel-forming fibres provides a material which has a high absorbency, enabling good transfer of exudates away from a wound, which retains structural integrity, and which is non-adherent and easily removed from the wound.

Claims

1. A three-dimensional textile spacer fabric, which is formed of a yarn comprising a blend of gelling fibres and non-gelling fibres, wherein the yarn comprises at least 50% w/w gelling fibres.

2. The three-dimensional textile spacer fabric of claim 1, wherein the gelling fibres are pectin, alginate or carboxymethyl cellulose (CMC) fibres, or any combination thereof.

3. The three-dimensional textile spacer fabric of claim 1, wherein the non-gelling fibres are cellulosic fibres.

4. The three-dimensional textile spacer fabric of claim 1, wherein the cellulosic fibres are lyocell.

5. The three-dimensional textile spacer fabric of claim 1, wherein the non-gelling fibres comprise less than 20% of the three-dimensional textile material.

6. The three-dimensional textile spacer fabric of claim 1, which has a thickness of from 1 mm to 60 mm.

7. The three-dimensional textile spacer fabric of claim 6, which has a thickness of from 2 mm to 10 mm.

8. The three-dimensional textile spacer fabric of claim 1, which is knitted.

9. A wound dressing comprising a three-dimensional textile spacer fabric according to claim 1.

10. The wound dressing of claim 9, wherein the three-dimensional textile fabric constitutes the wound-contacting component of the dressing.

11. The wound dressing of claim 10, wherein the wound dressing consists of the three-dimensional spacer fabric.

12. A composite wound dressing comprising the three-dimensional spacer fabric of claim 1.

13. The composite wound dressing of claim 12, which further comprises a backing layer having a moisture vapour transmission rate of at least 300 g/m.sup.2/24 h.

14. The composite wound dressing of claim 13, wherein the backing layer is a polyurethane film.

15. The composite wound dressing of claim 13, wherein the backing layer extends beyond the edge of the three-dimensional textile material on all sides, forming a border around the three-dimensional textile material.

16. The composite wound dressing of claim 13, wherein the backing layer carries an acrylic adhesive on its underside.

17. The composite wound dressing of claim 12, wherein the entire underside of the wound dressing carries an adhesive layer.

18. The composite wound dressing of claim 17, wherein the adhesive layer comprises perforations having a diameter of 4-10 mm.

19. The composite wound dressing of claim 12, wherein the underside of the wound dressing carries an adhesive layer formed with a central opening through which the three-dimensional material is exposed.

20. The composite wound dressing of claim 19, wherein the adhesive layer comprises perforations.

21. The composite wound dressing of claim 19, wherein the adhesive layer is a silicone gel.

22. The composite wound dressing of claim 21, wherein the silicone gel is carried on a layer of melt-blown polyurethane (MBPU).

23. The composite wound dressing of claim 22, wherein the reverse side of the MBPU is coated with an acrylic adhesive.

24. The composite wound dressing of claim 12, which further comprises an absorbent body.

25. The composite wound dressing of claim 24, wherein the absorbent body is selected from a foam pad and a polymeric superabsorbent material.

26. The composite wound dressing of claim 12, wherein the wound dressing further comprises a releasable liner.

27. The composite wound dressing of claim 12, further comprising one or more additional agents selected from antimicrobial agents, antiseptic agents, antifungal agents and/or anti-inflammatory agents.

28. A wound dressing for use in negative pressure wound therapy, the wound dressing comprising an occlusive backing layer fitted with a drainage port, and the three-dimensional spacer fabric of claim 1.

29. The wound dressing of claim 28, wherein said wound dressing is a composite wound dressing.

30. The wound dressing of claim 29, wherein the drainage port is affixed to the upper layer of the wound dressing, the upper layer having an opening below the port to allow material to pass from the interior of the dressing through the drainage port.

Description

[0117] The invention will now be described in greater detail, by way of example only, with reference to the accompanying drawings, in which

[0118] FIGS. 1(a) and 1(b) are lapping diagrams showing the structure of a fabric knitted using a yarn according to the invention;

[0119] FIG. 2 shows a first, substantially square, embodiment of a wound dressing according to the invention;

[0120] FIG. 3 shows a second, square, wound dressing similar to that of FIG. 2, which has been impregnated with honey;

[0121] FIG. 4 shows a third, tubular, embodiment of a wound dressing according to the invention;

[0122] FIG. 5 shows a fourth embodiment of a wound dressing according to the invention, in the form of an alginate foam reinforced with a knitted scrim comprising a yarn according to the invention;

[0123] FIG. 6 is a perspective view, schematic and not to scale, of a spacer fabric according to the invention, comprising gelling fibres that constitutes a fifth embodiment of a wound dressing according to the invention;

[0124] FIG. 7 is a perspective view from above of a sixth embodiment of a wound dressing according to the invention, incorporating a gelling spacer fabric of the form shown in FIG. 6;

[0125] FIG. 8 is an underside plan view of the wound dressing of FIG. 7;

[0126] FIG. 9 is across-sectional view, not to scale, on the line VIII-VIII in FIG. 8;

[0127] FIG. 10 is a view similar to FIG. 9 of a seventh embodiment of a wound dressing according to the invention, incorporating a gelling spacer fabric and adapted for use in negative pressure wound therapy (NPWT);

[0128] FIG. 11 is a view similar to FIG. 10 of a eighth embodiment of a wound dressing suitable for NPWT, with a silicone gel skin contact layer that extends across the full extent of the underside of the dressing;

[0129] FIG. 12 is an underside plan view of the wound dressing of FIG. 11, with the release liners removed; and

[0130] FIG. 13 is a view similar to FIGS. 11 and 12 of an ninth embodiment of a wound dressing according to the invention, again suitable for NPWT, and

[0131] FIG. 14 is an underside plan view of the wound dressing of FIG. 13, with the release liners removed.

[0132] Referring first to FIG. 1(a), there is shown a lapping diagram 1 of the pattern for a warp-knitted fabric. The lapping diagram is formed of a grid of dots. Each dot represents a needle head 2, and the lines 3 and 4 represent the path of the yarn in the knitted fabric. Each horizontal row of needle heads represents one course, ie a single stitch forming process. Each vertical column of needle heads is related to an individual yarn 3 (a warp yarn), and each of these individual yarns travels vertically up the column, forming a closed loop 5 about each needle head 2. The lapping diagram also includes a single weft yarn 4 which runs horizontally across each course, interlocking with the closed loops 5 of the warp yarn 3 and thereby forming the fabric structure. The resulting fabric has a crochet stitch pattern.

[0133] FIG. 1(b) is a lapping diagram showing an alternative structure for a warp-knitted fabric, formed in a closed tricot stitch pattern with a two needle warp. Each vertical column of needle heads is related to an individual yarn 6 (a warp yarn). The yarn forms a closed loop 7 around the first needle head in the column. It then travels upwards, and forms a closed loop around a needle head in the row above, but in the adjacent column 8. The yarn then travels up, and forms a closed loop around a needle head in the third row, but in the first column. The yarn continues upward in this manner, forming a zig-zag pattern. The lapping diagram also includes a single weft yarn 9 which runs horizontally across each course, interlocking with the closed loops of the warp yarn and thereby forming the fabric structure. It is the system of interlocking loops that gives the knitted fabric its tensile strength, as well as a degree of elasticity.

[0134] The lapping diagrams of FIG. 1 can be used to produce a knitted fabric. As shown in FIG. 2, such a knitted fabric may be produced as a square, and forms a 10 cm10 cm square wound dressing 10.

[0135] FIG. 3 shows a further embodiment of the invention in which a square wound dressing 20 (similar to the dressing 10 of FIG. 2) has been dosed with 25 g of manuka honey 21. The honey 21 is deposited on the surface of the wound dressing 20, and is substantially fully absorbed into the knitted substrate. The honey extends irregularly over the extent of the wound dressing 20, covering a substantial portion of the surface area.

[0136] FIG. 4 shows a tubular dressing 30, of the type worn on an arm or a leg, produced using fabric knitted to the pattern of FIG. 1(a) or 1(b). The tubular dressing 30 has been produced by knitting in the round, so that there is no seam running lengthways down the dressing.

[0137] Alternatively, the tubular dressing 30 may be produced from a flat sheet of knitted material which is sewn together along opposite edges to form a tube. The tubular dressing may be produced as an individual unit, or as an extended tube which may be cut to the desired size.

[0138] FIG. 5 shows a further embodiment of a wound dressing according to the invention, in this case an alginate foam dressing 40. The dressing 40 comprises first and second layers 41,42 of alginate foam that are reinforced by a sheet of knitted fabric 43 (similar to the sheet 10 of FIG. 2) that is sandwiched between the layers 41,42 of foam.

[0139] The dressing 40 is manufactured by casting a first quantity of alginate solution (typically containing sodium alginate, a source of calcium ions, and a sequestering agent to prevent premature precipitation of calcium alginate) into a rectangular mould. The solution is allowed to partially cure and the sheet of knitted fabric 43 is laid on top of the partially cured solution. A second quantity of alginate solution is then cast on top of the knitted fabric 43, and curing of both quantities of solution is allowed to continue until hydrogels are formed on both sides of the knitted fabric 43. The product is then subjected to lyophilisation to remove water from the hydrogels and to create the foam layers 41,42.

[0140] Referring now to FIG. 6, a spacer fabric 50 comprises an upper face layer 52, a lower face layer 53, and a connecting layer 54 which comprises connecting threads 55 that extend between the upper face layer 52 and lower face layer 53. The spacer fabric is knitted by a conventional process suitable for the production of such a knitted structure, using a yarn that comprises a blend of gelling fibres and non-gelling cellulosic fibres. The gelling fibres are present in a major proportion (approximately 90%), the minor proportion of non-gelling fibres serving to maintain the integrity of the fabric even after gelling of the gelling fibres.

[0141] If necessary or desired, for instance to minimise risk of fibre fragments being lost from the fabric 50 in use, at the edges of the spacer fabric 50, the upper face layer 52, the lower face layer 53 and the connecting layer 54 may be fused together to create a seal.

[0142] The spacer fabric 50 of FIG. 6 may be used as a simple form of wound dressing, in the manner of a conventional gelling dressing, such as those that have the form of a non-woven pad of gelling alginate or carboxymethylcellulose fibres. Such dressings are simply applied to the wound surface and absorb wound exudate. As the exudate is absorbed, the fibres are transformed into a gel that maintains a moist environment at the wound surface and is non-adherent, which enables the dressing to be removed without trauma to the wound.

[0143] Alternatively, the spacer fabric 50 of FIG. 1 may form a component of a composite wound dressing. FIGS. 7 to 14 illustrate embodiments of such composite wound dressings.

[0144] The wound dressing of FIGS. 7 to 9 is generally designated 60 and is generally square in form and comprises a backing layer 61 of microporous polyurethane film, having a central portion 62 and a border 63. The central portion 62 overlies a composite body comprising a square piece of three-dimensional textile material 65 similar to that shown in FIG. 6 and an absorbent foam pad 66. The textile material 65 and foam pad 66 are affixed to each other by any suitable means, eg by adhesive. The three-dimensional textile 65 is shown as hidden detail in FIG. 8 and the composite is visible in FIG. 9.

[0145] The underside of the backing layer 61 carries a coating of adhesive 67, eg an acrylic adhesive, by means of which the backing layer is affixed at its central portion 62, to the absorbent pad 66. The adhesive coating 67 on the border 63 serves to attach the dressing 60 to the skin surrounding a wound, so that in use the three-dimensional textile 65 overlies the wound. The wound dressing 60 is supplied with a two-part release liner 64, which is removed from the dressing immediately prior to use, in order to expose the three-dimensional textile material 65 and the adhesive 67 on the underside of the border 63. The underside of the wound dressing 60 is depicted in FIG. 8, in which the three-dimensional textile material 1652 is shown in broken lines as hidden detail.

[0146] FIG. 9 is a cross-sectional view of the wound dressing 60 described above. The wound dressing includes a composite body that comprises the three-dimensional textile material 65 and absorbent foam pad 66. The three-dimensional textile material 65 and the absorbent pad 66 are overlaid by the backing layer 61 of polyurethane film, the absorbent pad 66 being secured to the underside of the backing layer 61 by the coating of adhesive 67. The backing layer 61 extends beyond the edges of the three-dimensional textile material 65 and the absorbent pad 66 on all sides to form the border 63 that is also coated with the adhesive 67. The releasable liner 64, which comprises two sheets of suitable plastics film or other conventional material that overlap to form tabs to facilitate removal of the liner 64, covers the adhesive 67 and the exposed face of the three-dimensional textile material 65. The releasable liner 64 is removed immediately prior to use.

[0147] FIG. 10 shows a further embodiment of a wound dressing, generally designated 70, according to the invention that is suitable for use in negative pressure wound therapy. This dressing 70 is broadly similar in construction to that of FIGS. 7 to 9, and corresponding components of the dressing are denoted by the same reference numerals. Thus, the dressing 70 is generally square in form and comprises a backing layer 61 of microporous polyurethane film, having a central portion 62 and a border 63. The central portion 62 overlies a composite body comprising a square piece of three-dimensional textile material 65 similar to that shown in FIG. 6 and an absorbent foam pad 66. The textile material 65 and foam pad 66 are affixed to each other by any suitable means, eg by adhesive. The three-dimensional textile 65 is shown as hidden detail in FIG. 8 and the composite is visible in FIG. 9.

[0148] The underside of the backing layer 61 carries a coating of adhesive 67, eg an acrylic adhesive, by means of which the backing layer is affixed at its central portion 62, to the absorbent pad 66. The adhesive coating 67 on the border 63 serves to attach the dressing 60 to the skin surrounding a wound, so that in use the three-dimensional textile 65 overlies the wound. The wound dressing 60 is supplied with a two-part release liner 64, which is removed from the dressing immediately prior to use, in order to expose the three-dimensional textile material 65 and the adhesive 67 on the underside of the border 63.

[0149] The wound dressing 70 includes a composite body that comprises the three-dimensional textile material 65 and absorbent foam pad 66. The three-dimensional textile material 65 and the absorbent pad 66 are overlaid by the backing layer 61 of polyurethane film, the absorbent pad 66 being secured to the underside of the backing layer 61 by the coating of adhesive 67. The backing layer 61 extends beyond the edges of the three-dimensional textile material 65 and the absorbent pad 66 on all sides to form the border 63 that is also coated with the adhesive 67. The releasable liner 64, which comprises two sheets of suitable plastics film or other conventional material that overlap to form tabs to facilitate removal of the liner 64, covers the adhesive 67 and the exposed face of the three-dimensional textile material 65. The releasable liner 64 is removed immediately prior to use.

[0150] The dressing 70 differs from the dressing 60 in that the backing layer 61 is provided with a central opening 76 and a drainage port 75 is affixed to the backing layer 61 directly above the opening 76. The drainage port 75 is formed by injection moulding in plastics material and includes an upstand with a central bore 75a that is aligned with the opening 76.

[0151] The dressing 70 is applied to a wound in the same manner as the dressing 60. The dressing 70 can be used in NPWT by attaching (by means of a flexible tube) the drainage port 75 to a source of reduced pressure, such as a pump. The pressure within the interior of the dressing 70 is thereby reduced to less than the ambient air pressure. Excess wound exudate is drawn through the three-dimensional textile material 65, the absorbent pad 66 and the drainage port 75, and is collected in a suitable receptacle in a conventional manner.

[0152] A further embodiment of a wound dressing, generally designated 80 and again suitable for use in NPWT, is shown in FIGS. 11 and 12. This dressing 80 is broadly similar to the dressing 70 of FIG. 10, and again corresponding components of the dressing are denoted by the same reference numerals.

[0153] In the dressing 80, however, a silicone gel skin contact layer 88 extends across the whole extent of the underside of the dressing 80. The skin contact layer 88 comprises a sheet of melt-blown polyurethane that carries a coating of silicone gel. The reverse side of the melt-blown polyurethane is coated with acrylic adhesive by which it is affixed to the border 63 of the backing layer 61 and to the underside of the three-dimensional textile material 65. The skin contact layer is formed with a regular array of perforations 89 with approximate diameter 5 mm that permit wound exudate to pass from the wound into the three-dimensional textile material 65.

[0154] Finally, an embodiment of a wound dressing, generally designated 90 and again suitable for use in NPWT, is shown in FIGS. 13 and 14. This dressing 90 is broadly similar to the dressing 80 of FIG. 11, and corresponding components of the dressing are denoted by the same reference numerals.

[0155] In the dressing 90, however, the silicone gel layer 91 is present around the border 63 of the dressing 90 and partially overlaps the three-dimensional textile material 65. In other words, the silicone gel layer 91 is formed with a central opening that is slightly smaller in size than the three-dimensional textile material 65, so that the majority of the textile material 65 is exposed and, in use, directly contacts the wound. The composition of the silicone gel layer 91 is the same as that of the skin contact layer 88 as described in relation to FIG. 11, with the exception that the perforations 92 are of smaller diameter. In use, the silicone gel layer 91 contacts the skin around the edge of the wound, and the three-dimensional textile material 65 contacts the wound directly.