Wound dressing

Abstract

Wound dressings suitable for negative pressure wound therapy are disclosed. The wound dressings may include a body of porous material, the body of porous material may include a plurality of cuts which provide regions of flexibility within the body. Also disclosed are methods of manufacturing and methods of using such wound dressings. In addition, such wound dressings can include a retaining mechanism removably coupled to the material and configured to retain the material in the expanded conformation.

Claims

1. A wound dressing apparatus, comprising: an absorbent layer configured to transfer contractile forces to a wound site to promote wound closure, the absorbent layer having a first dimension and a second dimension, the second dimension perpendicular to the first dimension, the absorbent layer comprising a plurality of slits arranged in a pattern of separate parallel rows, wherein the plurality of slits comprise first slits extending parallel to the first dimension and second slits extending parallel to the second dimension, wherein the parallel rows comprise a first row extending along the second dimension across the absorbent layer and a second row adjacent to the first row extending along the second dimension, the first row comprising alternating first slits and second slits and the second row comprising at least second slits, wherein the second slits of the second row are staggered with respect to the second slits of the first row such that every first slit of the first row is directly adjacent to a second slit in both a first direction parallel to the first dimension and a second direction parallel to the second dimension; and a backing layer configured to be positioned over the absorbent layer.

2. The wound dressing apparatus of claim 1, wherein the first dimension corresponds to a length of the absorbent layer.

3. The wound dressing apparatus of claim 1, wherein the second dimension corresponds to a width of the absorbent layer.

4. The wound dressing apparatus of claim 1, wherein the absorbent layer comprises a carboxymethylcellulose-based hydrofibre.

5. The wound dressing apparatus of claim 1, wherein the absorbent layer is opaque.

6. The wound dressing apparatus of claim 1, wherein the absorbent layer is configured to become transparent when wet.

7. The wound dressing apparatus of claim 1, wherein the slits are sized and configured as a result of being formed by a cutter.

8. The wound dressing apparatus of claim 1, wherein the absorbent layer comprises a foam.

9. The wound dressing apparatus of claim 1, wherein the slits are configured to be positioned in a plane parallel to a wound.

10. The wound dressing apparatus of claim 1, wherein each first slit and each second slit pass entirely through a depth of the absorbent layer, wherein the depth is perpendicular to the first dimension and the second dimension.

11. The wound dressing apparatus of claim 1, wherein each first slit of the plurality of first slits is directly adjacent a second slit in both a first direction parallel to the first dimension and a second direction parallel to the second dimension.

12. The wound dressing apparatus of claim 1, wherein the second row comprises alternating first slits and second slits.

13. The wound dressing apparatus of claim 1, wherein each second slit is spaced apart from each adjacent first slit.

14. A wound dressing apparatus, comprising: an absorbent layer configured to transfer contractile forces to a wound site to promote wound closure, the absorbent layer comprising a pattern of separate parallel rows comprising a first row comprising slits oriented in a first direction and a second row comprising slits oriented in a second direction, the second direction perpendicular to the first direction; and a backing layer configured to be positioned over the absorbent layer.

15. The wound dressing apparatus of claim 14, wherein the first row comprises slits oriented in the first direction alternating with slits oriented in the second direction.

16. The wound dressing apparatus of claim 14, wherein the slits oriented in the first direction are staggered between adjacent first and second rows.

17. The wound dressing apparatus of claim 14, wherein the absorbent layer comprises a carboxymethylcellulose-based hydrofibre.

18. The wound dressing apparatus of claim 14, wherein each slit oriented in the second direction is directly adjacent a slit oriented in the first direction.

19. The wound dressing apparatus of claim 14, wherein each of the slits oriented in the first direction and each of the slits oriented in the second direction pass entirely through a depth of the absorbent layer, wherein the depth is perpendicular to the first direction and the second direction.

20. The wound dressing apparatus of claim 14, wherein each slit oriented in the second direction is spaced apart from each slit oriented in a first direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the present invention will be apparent from the following detailed description of the invention, taken in conjunction with the accompanying drawings of which:

(2) FIG. 1 demonstrates the extension of a slit, in three stages, under an extensive force, indicated by the arrows F, and in a direction perpendicular to the longitudinal axis of the slit. The intermediate or second stage shows that the slit has been expanded to form a circle.

(3) FIG. 2 is a plan view of a cutter for use in the manufacture of a first embodiment of lattice according to the invention.

(4) FIG. 3 is a plan view of the lattice formed using the cutter of FIG. 2, the lattice shown here in the open lattice or second conformation on application of a uni-directional extensive force applied perpendicular to the longitudinal axis of the slits.

(5) FIG. 4 is a plan view of a further cutter having a different cutting profile to the cutter of FIG. 2 for use in the manufacture of a second embodiment of lattice according to the invention.

(6) FIG. 5 is a plan view of the lattice formed using the cutter of FIG. 4, the lattice shown here in the open lattice or second conformation on application of a bi-directional extensive force applied perpendicular and parallel to the longitudinal axis of the slits.

(7) FIG. 6 is a schematic in plain view of yet a further a cutter, having an alternative cutting profile to the cutter of FIGS. 2 and 4, for use in the manufacture of a third embodiment of the lattice according to the invention.

(8) FIG. 7 is a plan view of the cutter manufactured according to the schematic of FIG. 6.

(9) FIG. 8 is a plan view of the lattice formed using the cutter of FIG. 7, the lattice shown here in the open lattice or second conformation on application of a bi-directional extensive force applied perpendicular and parallel to the longitudinal axis of the slits.

(10) FIG. 9 is a plane view of the lattice in the first conformation where the slits are substantially closed. The lattice is opaque and the slits allow for no or substantially no visual inspection across the lattice.

(11) FIG. 10 shows an array of blades adapted to form slits in a body of a wound dressing material according to the present invention;

(12) FIG. 11 shows a body according to the present invention curved in a first direction;

(13) FIG. 12 shows a body according to the present invention curved in a second direction;

(14) FIG. 13 shows a comparison of a body of foam according to the present invention with an un-cut body of foam;

(15) FIG. 14 shows a second array of blades adapted to form cuts in a body of a wound dressing material according to the present invention;

(16) FIG. 15 shows a body according to the present invention cut with the array of blades of FIG. 14; and

(17) FIG. 16 shows the body of FIG. 15 curved in two dimensions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(18) Like reference numbers refer to corresponding parts throughout the drawings, description and examples.

Example 1

(19) To create the wound dressing of example 1, a perforated sheet of polyurethane film was applied to the wound contact surface of a sheet of 4 mm depth polyurethane foam (Allevyn, Smith & Nephew Medical Limited).

(20) The wound contact surface is that surface which is placed adjacent to or in direct contact with the wound. The non-wound contact surface is that surface which is remote from or opposite the wound contact surface.

(21) A cutter of specification shown in FIG. 2 (Cutter blade with 15 mm length blades, linear spacing 5 mm, vertical spacing 5 mm) was used to cut slits in the sheet of polyurethane foam to form a lattice. The cutting action also formed slits in the polyurethane film.

(22) Following cutting, an extensive force was applied to the lattice in a direction perpendicular to the longitudinal axis of the cuts or slits to produce an open lattice as shown in FIG. 3. A moisture permeable top-film was heat laminated to the non-wound contact layer or surface of the open lattice. To the top-film, a polymeric film release sheet of sufficient mechanical stiffness to resist the contractile force of the open lattice was applied. After applying the release sheet the extensive force applied to the lattice was removed and the extended or open lattice was retained in the open lattice conformation by the release sheet.

Example 2

(23) To create the wound dressing of example 2, a perforated sheet of adhesive polyurethane film was applied to the wound contact surface of a sheet of 4 mm depth polyurethane foam (Allevyn, Smith & Nephew Medical Limited). The adhesive surface of the film was covered by a siliconised release paper. A cutter of specification shown in FIG. 2 (Cutter blade with 15 mm length blades, linear spacing 5 mm, vertical spacing 5 mm) was used to cut slits in the sheet of polyurethane foam to form a lattice. The cutting action also formed slits in the polyurethane film and siliconised release paper.

(24) The wound contact surface is that surface which is placed adjacent to or in direct contact with the wound. The non-wound contact surface is that surface which is remote from or opposite the wound contact surface.

(25) Following cutting, the siliconised release paper was removed and an extensive force was applied to the lattice in a direction perpendicular to the longitudinal axis of the cuts or slits to produce the open lattice pattern as shown in FIG. 3. A new sheet of siliconised release paper was then attached to the wound contact surface of the perforated adhesive film. A moisture permeable top-film was heat laminated to the non-wound contact layer or surface of the open lattice. To the top-film, a polymeric film release sheet of sufficient mechanical stiffness to resist the contractile force of the open lattice was applied. After applying the release sheet the extensive force applied to the lattice was removed and the extended or open lattice was retained in the open lattice conformation by the release sheet.

Example 3

(26) To demonstrate the effectiveness of the wound dressing of example 2, the siliconised release paper was removed from the perforated adhesive film and placed, adhesive side down, upon intact skin. The polymeric film release sheet was then removed. A uni-directional contractile force was generated on the skin, upon removal of the polymeric film release sheet, and in a direction perpendicular to the axis of the cuts.

Example 4

(27) To create the wound dressing of example 4, a perforated sheet of polyurethane film was applied to the wound contact surface of a sheet of 4 mm depth polyurethane foam (Allevyn, Smith & Nephew Medical Limited). A cutter of specification shown in FIG. 4 (Cutter blade with 15 mm length blades, linear spacing 5 mm, vertical spacing 2.5 mm) was used to cut slits in the sheet of polyurethane foam to form a lattice. The cutting action also formed slits in the polyurethane film and siliconised release paper.

(28) The wound contact surface is that surface which is placed adjacent to or in direct contact with the wound. The non-wound contact surface is that surface which is remote from or opposite the wound contact surface.

(29) Following cutting, the lattice was extended along two axes, x and y, as shown in FIG. 4. The extensive force was applied perpendicular and parallel to the longitudinal axis of the slits to produce an open lattice structure. A moisture permeable top-film was heat laminated to the non-wound contact surface of the open lattice. To the top-film, a polymeric film release sheet of sufficient mechanical stiffness to resist the contractile force of the open lattice was applied. After applying the release sheet the extensive force applied to the lattice was removed and the extended or open lattice was retained in the open lattice conformation by the release sheet.

Example 5

(30) To create the wound dressing of example 5, a perforated sheet of adhesive polyurethane film was applied to the wound contact surface of a sheet of 4 mm depth polyurethane foam (Allevyn, Smith & Nephew Medical Limited). The adhesive surface of the film was covered by a siliconised release paper. A cutter of specification shown in FIG. 4 (Cutter blade with 15 mm length blades, linear spacing 5 mm, vertical spacing 2.5 mm) was used to cut slits in the sheet of polyurethane foam to form a lattice. The cutting action also formed slits in the polyurethane film and siliconised release paper.

(31) The wound contact surface is that surface which is placed adjacent to or in direct contact with the wound. The non-wound contact surface is that surface which is remote from or opposite the wound contact surface.

(32) Following cutting, the siliconised release paper was removed and the lattice was extended along two axes, x and y, as shown in FIG. 4. The extensive force was applied perpendicular and parallel to the longitudinal axis of the slits to produce an open lattice structure. A new sheet of siliconised release paper was then attached to the wound contact surface of the perforated adhesive film. A moisture permeable top-film was heat laminated to the non-wound contact layer or surface of the open lattice. To the top-film, a polymeric film release sheet of sufficient mechanical stiffness to resist the contractile force of the open lattice was applied. After applying the release sheet the extensive force applied to the lattice was removed and the extended or open lattice was retained in the open lattice conformation by the release sheet.

(33) The lattice of the wound dressing of example 5, having the polymeric film release sheet removed, it shown in FIG. 5.

Example 6

(34) To demonstrate the effectiveness of the wound dressing of example 5, the siliconised release paper was removed from the perforated adhesive film and placed, adhesive side down, upon intact skin. The polymeric film release sheet was then removed. Upon removal of the polymeric film release sheet, a contractile force was generated on the skin acting towards the centre of the dressing.

Example 7

(35) A similar process to that described for the wound dressing of example 5 is employed to create the wound dressing of example 7. However, in this case, a cutter of specification shown in FIGS. 6 and 7 was used to cut the slits. As can be seen from FIG. 6, the blades have three cutting edges. A long cutting edge of 15 mm in length bridging two shorter cutting edges of 7 mm in length. The two shorter cutting edges being parallel to each other and perpendicular to the longer cutting edge. Each blade has a spacing with an adjacent blade which describes a square area having a side length of 3.75 mm. This spacing is demonstrated by the shaded square portion in FIG. 6.

(36) The lattice of the wound dressing of example 7, having the polymeric film release sheet removed, it shown in FIG. 8.

(37) An array of blades (10) mounted on a board is shown in FIG. 10. Each blade (12) is a straight thin blade 30 mm long, and having a depth of approximately 30 mm. The blades are arranged in 20 parallel linear series of blades (16,18), each series comprising a row of blades (12) arranged longitudinally, with a gap (14) of 3 mm between each blade (12) in the series. Each series is spaced from the adjacent series by a 3 mm spacing (15). Furthermore, adjacent series (16,18) are staggered relative to one another such that the gap between the blades on one series (16) aligns with the midpoint in the adjacent series (18). Accordingly, the blades within the array (10) are arranged like the bricks in a wall. Given this offset arrangement, it is convenient that at the end of a series where a full 30 mm blade would extend beyond the dimension to be cut, blades of 15 mm length are provided; this allows for a neater arrayonce more, this is akin to half bricks at the end of a row in a wall. Full length blades could be used at the ends, provided they would not be problematic in the cutting process.

(38) A body of NPWT foam (20) measuring 20012530 mm is cut using the array (10). It is cut by driving the array of blades (10) through the body (20) in a die cutting operation. This can be achieved using a press, typically a hydraulic press (not shown), also known as a clicker press. The blades are driven perpendicularly into and through the largest face of the body (20), and perpendicular thereto, to form a plurality of slits therein. The slits (21) formed are arranged in a plurality of parallel linear series (26,28) of slits, each comprising slits (21) 30 mm long separated by gaps (22), where material is left un-cut, which are 3 mm long. Each series is separated by a spacing (24) 3 mm in width. When the body (20) is curved, as shown in FIG. 11, the slits (21) open up to form a lattice structure. Tension in the outer region of the body (20) as a result of the curving process is relieved through deformation of the body (20) which is facilitated by the slits (21) provided therein. The arrangement of parallel offset linear series of linear slits is particularly suited to this as it form a regular lattice structure, as shown in FIG. 11.

(39) In the embodiment shown in FIG. 11, an additional partial cut (30) has been made running the length of the middle of the largest face of the body (20), perpendicular to the slits. This allows the body (20) to be easily split in two if this is desirable.

(40) FIG. 12 shows another body (40) cut using the array of blades of FIG. 10, this time without the additional cut (30). The body has been curved in a different manner to that in FIG. 11. In this case the body has been bent back on itself along its longest side, i.e. the 200300 mm face has been curved back on itself. The body (40) has opened via the slits (42) into an open lattice structure (44). This type of curving of the body (40) is not generally useful for a wound dressing application, but does serve to demonstrate the flexibility and strength of the body (40).

(41) FIG. 13 further demonstrates the ability of a body according to the present invention (40) to drape over a surface, in this case a leg, when compared to an uncut body (46).

(42) FIG. 14 shows an array (50) of blades adapted to form cuts in a body of foam in two orientations, the orientations being perpendicular to each other. As with the array (10) in FIG. 10, the blades have a depth of 30 mm. However, in the array (50) comprises H-shaped blades (52) comprising a first blade element 30 mm long (54) (also termed cross-piece), with second (56) and third (58) blade elements (also termed sides) 15 mm long located at the end of the first blade element (54), each end of the first blade element intersecting with the midpoint of the second and third blade elements, thus defining a wide H-shaped blade. The array is made up of first set of eleven parallel linear series of H-shaped blades in a first orientation (called X for convenience) and a second set of eleven parallel linear series of H-shaped blades in a second, perpendicular orientation (called Y for convenience). Adjacent series within each set are offset in exactly the same manner as for linear blades. As can be seen from FIG. 14, the blades are spaced and arranged such that a close packing of the blades as achieved, but each blade is always approximately 5 mm or so from the nearest neighbouring blade. It can be seen that the side of a blade in the X-orientation nests within the region defined by the cross-piece and sides of a blade in the Y-orientation. Such an array is suited to forming slits in a body to allow draping in two planes.

(43) FIG. 15 shows a body (60) formed by cutting with the array of FIG. 14. The slits (62) are formed by pressing the array of blades (50) through the body (60) in the same manner as described above. H-shaped slits (62) are formed in the body (60) corresponding to the array of blades (50). As shown in FIG. 16, the body (60) is well adapted to curving in complex shapes.

(44) It should be noted that the present description has focused on bodies formed by a batch die cutting process. There are of course numerous ways of forming cuts in a body of porous material (e.g. laser cutting, high pressure liquid cutting), or the cuts could formed when the body itself is formed (e.g. during a moulding process). Furthermore, these methods could be applied in a flow process rather than a batch; this might be more efficient for large production runs. All such variations are within the scope of the present invention.

(45) Furthermore, it should be noted that, while the exemplified embodiments form particularly preferred embodiments with excellent drapeability, it is quite possible that other arrangements of cuts will provide satisfactory results.