WO2001013853A1

WO2001013853A1 - Dressing

Info

Publication number: WO2001013853A1
Application number: PCT/GB2000/003252
Authority: WO
Inventors: Reginald Michael Tait; Tina Michelle Walker; Paul Bolton
Original assignee: Smith & Nephew Plc
Priority date: 1999-08-24
Filing date: 2000-08-23
Publication date: 2001-03-01
Also published as: AU6711500A; GB9919904D0

Abstract

A conformable cavity wound dressing comprising a flexible, apertured bag having a plurality of at least three faces adjacent faces being differentiated from each other by edges, and containing an absorbent material, characterised in that the faces form a polyhedron. It conforms to the contours of the wound, is absorbent and soft, and permits passage of exudate into the absorbent. Preferred dressings are non-adherent to the healing wound.

Description

DRESSING

The present invention relates to an absorbent medical dressing and, in particular, to such a dressing that is conformable so that it can be easily applied over contoured cavity wound surfaces.

Absorbent cavity wound dressings in the form of a bag filled with an absorbent means that demonstrate a certain degree of conformability are known. These however often do not optimally contact all internal surfaces of a cavity wound and/or are subject to rucking, which can occur due to the relative inflexibility of conventional absorbent material or the dressing shape. Many dressing embodiments of the prior art have a bag formed from only two faces, held together in the unfilled state in an essentially mutually parallel planar conformation by, for example a heat weld or an adhesive bond. Even when filled with absorbent means the bag is significantly two-dimensional with no significant third dimension.

This can lead to poor fitting of the dressing (especially in deeper wounds with relatively steep walls, such as those within the body cavity of the patient), discomfort, and leakage of wound exudate and can increase the risk of infection of a wound. Even if moulded initially in a wound to try to match the wound contours, on absorbing exudate it will tend to expand to regain its original form, potentially leading to the same problems.

The present invention seeks to obviate at least some of the abovementioned disadvantages. Thus, it has now been found that by using a wound dressing comprising an absorbent in a porous bag with a significant three-dimensional structure, a cavity wound dressing is obtained with the following advantageous properties: It conforms to the contours of the wound, is absorbent and soft, permits passage of exudate into the absorbent, preferably between individual pieces of foam, is non-adherent to the healing wound, and does not need to be provided in a wide variety of shapes and sizes in order to fit a wide variety of cavity wounds. According to the present invention there is provided a conformable cavity wound dressing comprising a flexible, apertured bag having a plurality of at least three effective faces and containing an absorbent material, characterised in that the faces form a polyhedron.

The term 'bag' is used herein merely to indicate a container, pocket, pouch, purse or like receptacle for containing absorbent material in the dressing.

The term 'effective faces' is used to indicate the faces effectively presented by the filled bag. This is regardless of whether adjacent faces are differentiated from each other by edges, each of which may be a clear, distinct and perceptible, sharp or marked fold optionally in a single sheet, film or membrane that forms a bag wall, or with a seam, joint or like union along the edge, or a curvature in such a sheet, film or membrane between the faces.

It is to be read as clearly different from any face of any such sheet, film or membrane. For example, a tetrahedral bag with four effective faces may be made from one sheet, film or membrane with one face corresponding to external faces of the bag. This may be effected by suitably folding or doubling over the material, fixing two edges together, and reconfiguring the third edge so that it is skewed at right angles to its original conformation. The edge is then fixed its final conformation to produce a diagonal, fold, or curve in two planar faces, thus defining four effective faces.

The term 'polyhedron' herein includes polyhedra with planar faces and/or straight boundaries, for example straight edges and/or curves along a straight line, between effective faces. It also includes those with convexly or concavely curved faces and/or edges or curves along curved lines.

It includes polyhedra that are totally convex. It also includes those with re-entrant angles between effective faces, for example those with a cross-section resembling a double axehead, formed by tucking or pleating a bag wall.

An advantage of the present invention is that the dressings may be useful in the treatment of cavity wounds.

A particular advantage is their usefulness in absorbing wound exudate therefrom, and in maximising contact of all internal surfaces of a cavity wound with the dressing and hence access to the absorbent material therewithin.

The apertures in the bag that contains the absorbent assist in dispersing wound exudate so that it can be absorbed across a larger portion of the absorbent material.

The increased three-dimensional nature of the bag (relative to a generally planar bag form of the prior art) can assist in ensuring good conformability to contact all internal surfaces of a cavity wound. It can hence improve the efficiency with which exudate can be absorbed.

In view of the relative flexibility of the bag, the effective faces may readily vary in conformation to provide the dressing with a significant variable three-dimensional profile.

Desirably the effective faces form a polyhedron. The effective faces may, for example form a polyhedron of effective faces each of which is of regular geometric form. These may be planar or curved and/or may have straight or curved edges and/or curves along straight or curved lines between them. They may be, for example triangular, square, rectangular, pentagonal, hexagonal, circular, part circular, part annular, kite-shaped and the shape of an arched doorway.

Preferred effective faces are those with at least one curved edge and/or with at least one curve between them, particularly at least one curve along a curved line between them. Such faces and corresponding polyhedra are preferred since the curved integers tend to reduce the number of sharp edges and/or corners on the corresponding polyhedra, and hence potential trauma to the wound bed.

The effective faces may be all of the same size and shape. However, the scope of the present invention includes dressings where the effective faces are of mixed sizes and shape.

Preferably, there are at least four effective faces but there may be in excess of ten such effective faces.

Corresponding polyhedra thus include tetrahedra, square and rectangular pyramids, triangular prisms, cubes and cuboids, and octahedra, and cylinders, and truncated and polytruncated versions of such solid figures, and truncated cones. They also include bisphenoids with two opposed curved edges and/or curves along a curved line between adjacent effective faces (thus corresponding to tetrahedra with two opposed curved edges and/or curves along a curved line between adjacent effective faces).

Preferred bag shapes include those of higher symmetry, for example tetrahedra, pyramids, cubes and cuboids. Particularly preferred bag shapes include cylinders, truncated cones, and bisphenoids with two opposed curved edges and/or curves along a curved line between adjacent effective faces (thus corresponding to tetrahedra with two opposed curved edges and/or curves along a curved line between adjacent effective faces). A further form of the dressing is in the form of an elongate cylinder or truncated cone, in which the ratio of length to width may be up to 6:1 , more suitably 2:1 - 5: 1 , and preferably 3:1 - 4:1.

Suitably the largest cross-dimension of the bag may be up to 400mm (for example for large abdominal wounds), such as up to 200mm (for example for auxiliary and inguinal wounds), and suitably 20mm to 100mm for medium sized wounds. The bag may be formed of a single piece of perforate material in the desired shape. This can be done for example by heat forming the perforate material in the desired shape in situ in a preshaped mould.

Alternatively or additionally, where appropriate the bag may be made from a single piece of perforate material in the appropriate shape, for example by a) suitably folding or doubling over the material, and then b) skewing, twisting or distorting the configuration of an edge or the structure prior to fixing it in its final conformation, for example by heat sealing or an adhesive bond.

This method is noted for a tetrahedral bag hereinbefore. A single, suitably shaped sheet, film or membrane may be used to form the 'curved edge tetrahedron, noted above.

Alternatively, the bag can be formed by cutting effective faces to shape and heat welding them along their edges to form the bag.

In the latter case, the bag may be a flexible, apertured bag having a plurality of at least three effective faces, at least two of which may be planar or of a very shallow convex or concave "V" shaped or "U" shaped cross-section.

To permit access of exudate to the absorbent, at least part of the bag must be apertured, for example provided with at least one, and preferably a multiplicity of, apertures, such as holes, openings, orifices, perforations or slits. Exudate passes through these in use to the absorbent inside the bag.

The perforate bag material may be any perforate material suitable for cavity wound use. Desirably the perforate bag material is resiliency deformable. It is desirable that the bag material has a tensile strength of 400, preferably 500, in particular 600gf/cm minimum. Its elongation at break is suitably 250%, preferably 350%, preferably 450% minimum. Aptly the material forming the perforate bag will comprise a perforate polymeric film, sheet or membrane, such as an integral net, for example one formed by the fibrillation of an embossed film, sheet or membrane of a polymeric material or by casting the material onto an embossed former.

Polymeric material that is suitable for the present nets includes thermoplastic elastomers and elastomer blends.

Apt perforate bag integral net materials include polymeric material such as thermoplastic elastomers and elastomer blends, for example copolymers, such as ethyl vinyl acetate polystyrene and elastomeric polyurethane, for example EU40 (trade mark), particularly polyurethane nets formed by solution casting or the fibrillation of a corresponding film, sheet or membrane.

Suitable nets may be prepared by casting a solution of the material forming the net onto an embossed film and wiping the embossed film to make sure that the tops of the embossments are not covered by the casting solution.

The temperature, pressure and time required for the process will depend on the properties of the polymer film, but must allow the polymer to flow into the troughs between the embossments leaving their tops uncovered.

Particularly preferred nets and their manufacture are those described in European Patent No. 171 268.

Suitably the net will have a (usually uniform) thickness of 5gsm to

400gsm, preferably 10gsm to 200gsm, preferably 20gsm to 80gsm. The size of the apertures will be chosen not only to prevent pieces of absorbent protruding from the dressing and abrading the wound surface or adhering to it, but also to prevent any particles of it escaping from the bag. The apertures may be any convenient shape. Suitably the apertures will be 0.03mm to 6mm, more suitably 0.1mm to 2mm, and preferably 0.3 - 0.6mm in mean cross-dimension.

In one embodiment of the present dressing, the bag is formed from a material that comprises a plurality of perforate polymeric films, such as integral nets, each for example formed by the fibrillation of an embossed film.

Each film is fixed to at least one other film, for example by heat sealing or an adhesive bond, at a plurality of locations, for example by so-called point sealing.

Suitably, two such films, membranes or sheets may be used to form the bag, being mutually point sealed, in particular by spot welding. The nets may be conveniently made from the same materials as indicated as suitable for the material of the bag hereinbefore.

Such a multiple-layer construction provides several advantages. One is increased strength; the danger of the dressing spilling its contents if one layer is ripped (by forceps, for example) is reduced.

Also, movement between the layers prevents clotting of blood and exudate by providing a built in 'break-point' between them. Drying out by evaporation is diminished.

The absorbent material may be any absorbent material suitable for cavity wound use. The absorbent should not be stiff or rigid. Desirably the absorbent material is resiliently deformable.

Preferred materials are hydrophilic materials, by which will be understood materials that absorb aqueous fluids such as water, blood, wound exudate and other body fluids.

Apt absorbent materials include non-woven materials. These include synthetic polymeric materials, such as polypropylene, polyamide and polyester, and reconstituted natural polymers, such as viscose and rayon, all typically spun-bonded; and natural polymers, such as compressed cotton, for example cotton wool.

Apt absorbent materials also include synthetic and natural super- absorbent materials, including super-absorbent paper, and hydrogel precursors (xerogels), including natural materials, particularly alginates, and hydrophilic gels.

These also include synthetic and hydrophilic foams, including elastomeric foams, particularly polyurethane foams, and polymer blend foams.

Materials for the last-named type of absorbent include blends of synthetic polymeric materials, such as polypropylene, polyamide and polyester, and reconstituted natural polymers, such as viscose and rayon.

These include viscose and polyester blends, such as Melolin (trade mark of Smith & Nephew).

Aptly any foam will be a resilient open-cell foam. One favoured foam may be formed by foaming, for example by blowing or reticulating, a hydrophilic polyurethane, as described in UK 2 093 190.

In use, a conformable dressing of the present invention is placed with the bag in a cavity wound.

Thus, the bag of the dressing may then be moved to allow the bag in the dressing to conform to the shape of a cavity wound effective faces to which it is applied.

By varying the extent to which the bag is filled, conforming deformation of the bag can be enhanced.

Only partly filling the internal space of the bag with absorbent, for example only 20% to 80%, in particular 40% to 60%, is advantageous. It reduces the likelihood of there being insufficient conformability to contact all internal surfaces of a cavity wound or of rucking of the walls of the bag.

It is particularly useful for application to cavity wounds if the absorbent material is particulate, for example strips, bands, ribbons, tapes, fibres, filaments, nets, ropes, strings, yarns, crumbs, fragments, grains or granular pieces.

It is especially useful for use in relation to highly contoured cavity wound surfaces if it is in the form of crumbs, fragments, grains or granular pieces. These allow good conformation of the dressing bag to the cavity wound faces. Suitable and preferred materials for such particulates are as so described hereinbefore. Preferred materials for such particulates are foams and cotton wools.

Particularly preferred foams are those disclosed in European Patent No. 171 268. The pieces in those cases have a preferred mean cross-dimension of 2mm to 5mm, but need not be of uniform size or of regular shape.

Suitably the ratio between the mean cross-dimension of an aperture and a piece of foam is at least 1 :4, and is preferably 1 :6. There is then little or no propensity for the pieces of foam to be shed or protrude from the bag.

It is envisaged that such foams may be used dry or may be wetted and squeezed out, whereupon they retain sufficient moisture to remain soft and flexible.

The absorbent may contain a physiologically acceptable surfactant, for example a non-ionic surfactant, favoured such surfactants being oxypropylene - oxyethylene copolymers, such as the Pluronics (trade mark of BASF). An x-ray detectable filament may be added to the absorbent to decrease risk of a dressing being left in the wound unnoticed.

In one embodiment of the present dressing, the bag comprises a net that comprises a plurality of inwardly projecting bosses, and a particulate absorbent.

The bosses may be conveniently made by impressing the outside surface of the material of the bag.

The irregular packing of particulate absorbent that this engenders may be advantageous in allowing wound exudate better access to more internal pieces of absorbent.

In another embodiment, the dressing is provided with a fleece between the bag and the absorbent.

Suitable materials for the fleece include polyethylene, polypropylene, polyesters and polyamides.

In a further embodiment of the invention, the bag comprises other integers, which are connected to the bag.

For example, the bag may have at least one substantially flat effective face distal to the wound-facing effective faces of the bag. The or each such distal effective face may optionally be covered by a backing layer, which may be adhered to it.

The backing layer may extend beyond the distal effective face or effective faces, and may bear an adhesive film, for example a pressure sensitive adhesive film on a proximal face. Thus, the backing layer may act as an adhesive retaining member.

The bag may have a trailing band, ribbon, strip or tape attached to it, for example by heat sealing, to aid removal of the dressing, and to indicate the number of dressings in the wound. The band, ribbon, strip or tape must be of a non-absorbent material, to prevent bacterial infection by capillary action.

A band, ribbon, strip or tape integral with the material of the bag is preferred.

The wound dressings of the present invention may also contain (usually in the absorbent) physiologically active components in therapeuticaliy active amounts, such as 0.2 to 20, more usually 0.3 to 10, and preferably 0.5wt.% to 5wt.% wrt absorbent.

It may thus contain for example local anaesthetics; hormones, such as growth hormones; and enzymes.

It may also or alternatively contain antimicrobials. Examples of such include antibacterial agents, for example triclosan, iodine, metronidazole, cetrimide, chlorhexidine acetate, chlorhexidine gluconate, iodine and silver sulphadiazine. Examples of such also include antifungal agents, for example sodium undecylenate, chlorhexidine and iodine.

It may also or alternatively contain debriding agents; and, less favourably, lubricating and barrier chemicals, such as silicones.

The physiologically active component(s) may be incorporated into the absorbent during the manufacture of the absorbent or by soaking the bag in a solution and/or dispersion of the component(s).

The backing layer is preferably moisture vapour permeable to allow exudate/sweat to evaporate through the dressing.

It is desirable that the wound dressing of the present invention is sterile. It is advantageously provided for use in a bacteria-proof pouch. In a further aspect, the present invention provides a method of treating a cavity wound by applying the bag of a dressing of the first aspect of the present invention into the wound.

The present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figs. 1 to 6 are perspective views of a tetrahedral dressing of the invention (Fig. 6) and its manufacture.

Figs. 7 to 12 are perspective, elevation and plan views of a curved-ended bisphenoid dressing of the invention, and (Fig. 7) of the sheet from which it is manufactured.

Fig. 13 is a perspective view of a dressing of the invention depicted in Figs. 8 to 12 in a cavity wound.

Referring to Figs. 6 and 8 to 12, a cavity wound dressing (1 ) comprises a flexible, apertured bag (2) having a plurality of (at least three) effective faces (11 , 11 , 11 , 11).

The bag (2) contains an absorbent material (3) (shown in Fig. 4), for example particulate foam.

Referring to Figs. 1 to 6 a rectangular portion of Allevyn Quantum

(trade mark of Smith and Nephew) polyurethane film (Fig. 1 ) is doubled over (Fig. 2).

Edges (12, 13) are welded with a heat seal, forming a bag (21 ) open along the edge (14) (Fig. 3). The open bag (21 ) is then half filled with a particulate absorbent material (Fig. 4). The open bag (21 ) is then reconformed so that the upper end (23) of the edge (13) lies in contact with the upper end (24) of the edge (15) (Fig. 5).

The edge (14) in its new conformation is then heat sealed to form the tetrahedral bag (1). Referring to Figs. 7 to 12 a portion of Allevyn Quantum (trade mark of Smith and Nephew) polyurethane film is shaped (Fig. 7). Edges (72, 73) are welded with a heat seal, forming a bag (not shown) open along the edge (74), which bag is then half filled with a particulate absorbent material. The edge (74) is then heat sealed to form the curved-ended bisphenoid bag (71 ).

Referring to Fig. 13, the bag (71) has been moulded to shape within a cavity wound to provide the proximal effective faces (84) of the bag (81 ) with good contact with the walls at different depths in the cavity wound.

The distal end (85) of the bag (81 ) can be covered with a water impermeable moisture vapour permeable adhesive film (not shown).

Claims

1. A conformable cavity wound dressing comprising a flexible, apertured bag having a plurality of at least three faces adjacent faces being differentiated from each other by edges, and containing an absorbent material, characterised in that the faces form a polyhedron.

2. A dressing according to claim 1 wherein at least one edge is a clear, distinct and perceptible, sharp or marked fold optionally in a single sheet, film or with a seam, joint or like union along the edge.

3. A dressing according to claim 1 wherein at least one edge is a curvature in a sheet, film or membrane between adjacent faces.

4. A dressing according to claim 1 wherein at least one edge is a straight edge and at least one edge is a curved edge.

5. A dressing according to claim 1 wherein at least one face is triangular, square, rectangular, pentagonal, kite-shaped or the shape of an arched doorway.

6. A dressing according to claim 1 wherein the bag is a tetrahedron, pyramid, cube or cuboid, or a bisphenoid with two opposed curved edges, or an elongate cylinder or truncated cone, in which the ratio of length to width is up to 6:1.

7. A dressing according to claim 1 wherein the absorbent material is particulate in the form of strips, bands, ribbons, tapes, fibres, filaments, nets, ropes, strings, yarns, crumbs, fragments, grains or granular pieces.

8. A dressing according to claim 1 wherein the internal space of the bag is 40% to 60% filled with absorbent.