RESILIENT WOUND DRESSING

Abstract

The present invention relates to a resilient wound dressing and absorbent articles for a resilient wound dressing. The present invention also relates to a method of manufacturing a resilient wound dressing as well as method of manufacturing a resilient absorbent article for a wound dressing.

Claims

1. A resilient wound dressing comprising: an absorbent layer comprising a non-woven resilient sheet of elastomeric material bonded to a non-woven absorbent material; an elastomeric backing layer; and an elastomeric adhesive layer located between the absorbent layer and the backing layer to adhere the absorbent layer to the backing layer.

2. The resilient wound dressing according to claim 1, wherein the non-woven resilient sheet comprises a melt-blown polymer web.

3. The resilient wound dressing according to claim 2, wherein the melt-blown polymer web comprises polyurethane fibres.

4. The resilient wound dressing according to claim 1 wherein the absorbent non-woven material is an absorbent non-woven fabric, preferably a needled felt.

5. The resilient wound dressing according to claim 4 wherein the fabric comprises gelling fibres.

6. The resilient wound dressing according to claim 5, wherein the gelling fibres comprise an alginate, carboxymethylcellulose (CMC), carboxymethyl viscose, gelatine, pectin, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, sulphonated cellulose (SC), sulphonated viscose, carboxymethyl chitosan, polyvinyl alcohol or any combination thereof.

7. (canceled)

8. The resilient wound dressing according to claim 1 wherein the non-woven absorbent material further comprises an anti-microbial agent and/or anti-biofilm agent.

9. The resilient wound dressing according to claim 8 wherein the anti-microbial agent and/or anti-biofilm agent is selected from the group consisting of silver, silver compounds, iodine compounds, monoguanides, biguanides, cationic surfactants, biocides, dispersing agents or combination thereof.

10. (canceled)

11. The resilient wound dressing according to claim 9 wherein the absorbent non-woven material is an absorbent non-woven fabric comprising gelling fibres, the anti-microbial agent and/or anti-biofilm agent is a silver compound, and the gelling fibres comprise an alginate, carboxymethylcellulose (CMC) and the silver compound, preferably wherein the alginate, carboxymethylcellulose (CMC) and silver compound are co-spun to form fibres which each comprise the alginate, carboxymethylcellulose (CMC) and silver compound, preferably wherein the silver compound is silver carbonate.

12. The resilient wound dressing according to claim 1 wherein the elastomeric backing layer is a polyurethane backing film, preferably a perforated polyurethane backing film.

13. The resilient wound dressing according to claim 1 further comprising a further elastomeric adhesive layer located on a proximal surface of the dressing for adhering the proximal surface of the dressing to the skin of a user, preferably wherein the further elastomeric adhesive layer is windowed.

14. The resilient wound dressing according to claim 1 wherein the elastomeric adhesive layer and/or a further elastomeric adhesive layer independently comprises a hydrocolloid.

15. (canceled)

16. The resilient wound dressing according to claim 1, wherein the non-woven resilient sheet and the non-woven absorbent material are bonded by needle bonding.

17. The resilient wound dressing according claim 1, wherein the non-woven absorbent material is in a fluted configuration.

18. A method of manufacturing a resilient wound dressing according to claim 1 comprising: (a) bonding the non-woven resilient sheet to the non-woven absorbent material to form the absorbent layer; and (b) adhering the absorbent layer to the elastomeric backing layer using the elastomeric adhesive layer.

19. A method of manufacturing a resilient absorbent article for a wound dressing comprising: expanding a non-woven resilient sheet of elastomeric material from a pre-expanded state to an expanded state; and bonding a non-woven absorbent material to the expanded non-woven resilient sheet, preferably by needle bonding; and allowing the non-woven resilient sheet to return from the expanded state towards the pre-expanded state (e.g. by retraction) to provide the resilient absorbent article.

20-34. (canceled)

35. A resilient absorbent article obtained or obtainable according to a method according to claim 19.

36. A resilient absorbent article comprising an absorbent non-woven material bonded to a resilient sheet of elastomeric material such that the absorbent layer adopts a fluted configuration when the absorbent article is not under tension and is able to adopt a substantially flattened configuration when the absorbent article is under tension.

37-38. (canceled)

39. The wound dressing according to claim 1 comprising an absorbent layer, an elastomeric polyurethane backing film; and an elastomeric hydrocolloid adhesive layer located between the absorbent layer and the backing layer to adhere the absorbent layer to the backing layer, the absorbent layer comprising a melt-bonded sheet of elastomeric material needle bonded to an absorbent needled felt comprising gelling fibres, preferably wherein the fibres comprise alginate, carboxymethylcellulose (CMC) and particles of silver carbonate co-spun together to form fibres which each comprise the alginate, carboxymethylcellulose (CMC) and silver carbonate particles.

40. The wound dressing according to claim 39 wherein the elastomeric backing layer is porous (e.g. perforated and the absorbent layer is orientated in the dressing such that the resilient melt-bonded elastomeric sheet is positioned distal to the wound in use relative to the absorbent needled felt and the absorbent needled felt is configured so as to be able to be in direct contact with the wound in use.

41. The wound dressing according to claim 40 comprising an absorbent layer, an elastomeric porous polyurethane backing film; and an elastomeric hydrocolloid adhesive layer located between the absorbent layer and the backing film to adhere the absorbent layer to the backing film, the absorbent layer consisting of a melt-bonded web of an elastomeric polyurethane which is needle bonded to an absorbent needled felt comprising gelling fibres, wherein the fibres comprise alginate, carboxymethylcellulose (CMC) and particles of silver carbonate co-spun together to form fibres which each comprise the alginate, carboxymethylcellulose (CMC) and silver carbonate particles), wherein the absorbent layer is orientated in the dressing such that the resilient melt-bonded elastomeric web is positioned distal to the wound when in use relative to the absorbent needle felt which is positioned relatively more proximal to the wound when in use and the dressing is configured such that the absorbent needled felt is useable to be in direct contact with the wound in use, the dressing further comprising a further elastomeric hydrocolloid adhesive layer located on a proximal surface of the dressing for adhering the proximal surface of the dressing to the skin of a user, wherein the further elastomeric hydrocolloid layer is windowed so as to allow the absorbent layer to be directly contactable with the wound in use.

Description

DESCRIPTION OF THE FIGURES

[0110] The present invention will be described with reference to the following non-limiting examples and figures, which show:

[0111] FIG. 1: A schematic view of the steps of carding and needle bonding a non-woven absorbent material (felt) to the non-woven resilient sheet of elastomeric material according to the present invention.

[0112] FIGS. 2a and 2b: A side view of an absorbent layer as provided in preferred embodiments of the first aspect of the invention, or an absorbent article according to the fourth or fifth aspects of the invention and producible according to the method of the second aspect of the invention.

[0113] FIG. 3: A plan view of a wound dressing according to the present invention depicting a windowed elastomeric adhesive layer applied to the proximal surface of the absorbent layer.

[0114] FIG. 4: A figurative cross-sectional view of a resilient wound dressing of the present invention.

[0115] FIG. 5: A stretch force plot (i.e. Force (N) vs Strain (%)) for an exemplary wound dressing of the invention stretched in the longitudinal direction.

[0116] FIG. 6: A stretch force plot (i.e. Force (N) vs Strain (%)) for a comparative Surgical wound dressing not according to the invention stretched in the longitudinal direction.

[0117] FIG. 7: A stretch force plot (i.e. Force (N) vs Strain (%)) for an exemplary wound dressing according to the invention stretched in the lateral (cross) direction.

[0118] FIG. 8: A stretch force plot (i.e. Force (N) vs Strain (%)) for a comparative Surgical wound dressing not according to the invention stretched in the lateral (cross) direction.

METHODS AND DETAILED DESCRIPTION

[0119] Preparation of the Resilient Wound Dressing

[0120] An exemplary method of manufacturing a resilient wound dressing according to the present invention is provided below.

[0121] Manufacture of the Non-Woven Absorbent Material

[0122] An aqueous spinning dope was prepared containing a formulation of sodium alginate, CMC and dispersed particles of silver carbonate. The dope was prepared by initially mixing the silver carbonate particles with water until the silver compound is fully dispersed. The CMC and sodium alginate components were then added before undergoing high shear mixing until a uniform dope mixture was obtained. The resulting dope mixture was then allowed to degas to let air bubbles in the mixture escape. The degassed dope mixture was then filtered to remove large particles (i.e. to remove particles over 35 microns). The filtered dope was then pumped through a spinnerette (e.g. hole size 70 microns) into a coagulant bath containing of 2%-4% w/w calcium chloride dehydrate coagulant solution to form coagulated fibres. The resulting fibres (i.e. the tow) were then orientated by stretching the tow in hot water (90 C.) before then washing with water to remove residual salts formed via ion exchange during coagulation. A solvent wash was then performed using suitable solvents (acetone/water mixtures). The washed fibres were then dried in a hot air oven and may be optionally finished using a finishing agent (such as Polyethylene GlycolPEG400). The fibres were then cut into staple lengths, carded and needled using techniques known in the art to form a non-woven absorbent felt material via fibre entanglement.

[0123] Manufacture of the Absorbent Layer by Needle Bonding of the a Non-Woven Absorbent Material (Felt) to the Non-Woven Resilient Sheet of Elastomeric Material

[0124] A sheet of melt-blown resilient non-woven polyurethane (M1630 White 500/1550 Stretch Non-Woven supplied by Freudenberg) was laid under tension and needle bonded to the non-woven absorbent felt material described above to form an absorbent layer.

[0125] FIG. 1 illustrates an exemplary in line method of carding and needle bonding the a non-woven absorbent material (felt) to the non-woven resilient sheet of elastomeric material according to the present invention. As shown in FIG. 1 a needling line (1) using two needle looms (3) and (7) (needle bonding stations) is used to manufacture the absorbent layer of the present invention. Firstly, a layered fibrous web (2) produced as a result of the carding (described above) is fed into the first needle loom (3) and the absorbent fibres are needled to form the non-woven absorbent felt (4) material via fibre entanglement also described above.

[0126] Subsequently, a sheet of melt-blown resilient non-woven polyurethane (e.g. M1630 White 500/1550 Stretch Non-Woven supplied by Freudenberg) (5) is introduced under tension on top of the non-woven absorbent felt material (4). The applied tension ensures that the material is stretched at least in the longitudinal direction in this embodiment. The tension control is achieved using a tension control unwind and a nip roller set up (6). The tensioned sheet is then needle bonded in the second needle loom (7) to create laminate stretchy absorbent layer (8) with a fluted appearance once relaxed. The absorbent layer is rewound to form a roll. It will be appreciated that the needle felting of the absorbent layer may alternatively be performed separately in a remote location.

[0127] FIGS. 2a and 2b illustrate a stretchy absorbent layer obtainable using the method described above, such as using the production equipment as illustrated in FIG. 1. The fluted configuration (8a) of the wound dressing can be seen. The distance between each flute is represented by distance x and the flute height is represented by distance y. In use, when typically forming part of the overall resilient wound dressing as described herein, the fibrous fluted configuration (8a) can stretch (or expandas depicted by the double-headed arrows in FIGS. 2a and 2b) together with the resilient non-woven polyurethane (8b) web to which it is needle bonded in response to a stretching force applied. This can occur when the resilient dressing of the present invention is applied to a wound located at a joint of the body (e.g. knee or elbow) wherein motion of the joint can apply a stretching force to the dressing. This force causes the lengthening of the bonded layers (8a) and (8b) as well as flattening of the flutes (8a) during the stretching process. Once the force is removed or subsides, the bonded layers (8a) and (8b) then contract to their pre-stretched or pre-expanded state, leading to the re-gathering of the absorbent material into a fluted configuration again. This stretching mechanism enhances the conformability of the dressing to the anatomy and profile of the wound when located at a joint.

[0128] Manufacture of the Elastomeric Adhesive Layer

[0129] A suitable hydrocolloid roll stock (e.g. sodium carboxymethylcellulose, polysaccharides and pectin containing hydrocolloid roll stocks) is mixed at a temperature of 80 C.-120 C. to form a hydrocolloid dope. This may be done, for example, using a Z-blade mixer. The hydrocolloid dope is then shaped into hydrocolloid logs for downstream processing. The hydrocolloid logs are then extruded through a heated die with a set aperture at 90 C.-120 C. onto a suitable carrier liner (e.g. paper or film) to form a flexible hydrocolloid sheet matrix. The suitable elastomeric adhesive layer (9) (e.g. hydrocolloid sheet matrix) is then cast onto a suitable elastomeric backing layer (10) (e.g. a polyurethane backing film) ready for adhering to the absorbent layer during the assembly of the dressing. The elastomeric adhesive layer and elastomeric backing layer are depicted bonded together in FIG. 4. Preferably, the backing layer has waterproof and bacterial barrier properties.

[0130] Manufacture of the Resilient Wound Dressing Assembly

[0131] The elastomeric backing layer (10) with the elastomeric adhesive layer (9) in the form of cast hydrocolloid sheet matrix cast thereon (as described above) is laid onto a conversion line. A fluted absorbent layer (8) as described above is cut to shape and placed onto the elastomeric backing layer (10) with the cast hydrocolloid sheet matrix (9) cast thereon to adhere the backing layer (10) to the absorbent layer (8) via the hydrocolloid sheet to form the resilient wound dressing assembly. Preferably the resilient sheet of elastomeric material is orientated to face the adhesive surface such that the absorbent needled felt is facing away from the adhesive in a proximal (ultimately wound facing) direction.

[0132] A further elastomeric adhesive layer in the form of a second hydrocolloid sheet matrix (produced as described above) may then be used to form a windowed or apertured hydrocolloid sheet matrix. If provided, such an elastomeric adhesive layer (11) is then laid over the resilient wound dressing assembly described above to form a laminated structure (depicted by layers 8, 9, 10 and 11 in FIG. 4). Optional, handle or release liners (12) are also included as shown in FIG. 4.

[0133] A plan view of the laminate structure is illustrated in FIG. 3. Here, the fluted configuration (8a) can be seen through the window or central aperture (13) formed in the elastomeric adhesive layer (11). During use, the fluted configuration (8a) is configured to be directly exposed to the wound whilst the elastomeric adhesive layer (11) is able to adhere the dressing to the area around the wound. This way, the fluid (e.g. wound exudate) can directly flow onto the flutes before being retained by the overall absorbent layer (8).

[0134] FIG. 4 illustrates a figurative cross-sectional view of an exemplary wound dressing of the present invention. As shown, the wound dressing includes a laminate structure having an elastomeric backing layer (10) adhered, via an elastomeric adhesive layer (9), to an absorbent layer (8), which comprises a non-woven absorbent layer (8a) bonded to a non-woven resilient sheet of elastomeric material (8b) wherein the resilient sheet is positioned distal portion of the absorbent layer (8) thus allowing the non-woven absorbent material (8a) to be proximal to the wound, and preferably configured to be in direct contact with the wound. The absorbent layer includes, on its distal (wound facing) surface, a further elastomeric adhesive layer (11) in the form of windowed hydrocolloid sheet matrix which is protected prior to use with a release or handle liner (12). During use the operator removes the handle or release liner (12) before carefully placing the wound dressing onto the wound site to be dressed. The wound dressing adheres and attaches to the skin surrounding the wound via the windowed second hydrocolloid sheet matrix (11). In the depicted embodiment, the central aperture (13) created by the windowed hydrocolloid sheet matrix exposes a fluted absorbent layer (8) to the wound site. This allows direct contact between fluted absorbent layer (8) and the wound exudate whilst at the same time ensuring that the dressing is firmly securely to the wound site.

[0135] Experimental Tests

[0136] A series of test were performed to measure the performance of an exemplary resilient wound dressing of the present invention against a comparative commercial wound dressing not according to the invention (i.e. Aquacel Ag Surgical wound dressing marketed by ConvaTec). The Aquacel Ag Surgical wound dressing includes a backing layer, absorbent layer and two hydrocolloid layers. One hydrocolloid layer adheres the absorbent layer to the backing layer and the other adheres the absorbent layer to the wound site during use. The absorbent layer contains a non-woven material made 100% CMC with silver. Elastic yarns are stitched through the absorbent layer in the longitudinal direction (warp) and non-elastic yarns are stitched in the cross direction (weft).

[0137] All test methods and procedures used to obtain the test data are provided herein and, unless specified otherwise, are known to the person skilled in the art.

[0138] The exemplary resilient wound dressing of the present invention used for the purposes of the following tests is referred to herein as the AMS wound dressing. The AMS wound dressing may be manufactured using the exemplary method of manufacturing a resilient wound dressing provided above and the material described below. The dope mixture used to provide the non-woven absorbent material is described below in Table 1 with the sheet of melt-blown resilient non-woven polyurethane being M1630 White 500/1550 Stretch Non-Woven supplied by Freudenberg.

TABLE-US-00001 TABLE 1 Component % By Weight Sodium Alginate (M:G ratio 60:40) 92 CMC (Carboxymethyl Cellulose) 4.25 Silver Carbonate 99.9% 3.75

[0139] The hydrocolloid used in the AMS wound dressing may be manufactured and formulated using techniques and procedures known in the art. An exemplary hydrocolloid for use in the embodiments of the invention is described in Table 2 below.

[0140] This hydrocolloid composition was the elastomeric adhesive layer used in the tested AMS wound dressing described herein.

TABLE-US-00002 TABLE 2 Hydrocolloid Component Amount (wt %) Polyisobutylene 28.36 Carboxymethylcellulose 29.63 Poly(styrene-butadiene-styrene) Block 16.29 Copolymer Hydrocarbon Resin 10.40 Purified Powdered Cellulose, Flock 8.44 Pectin 6.35 Other ingredients (including preservative 0.53 and liquid phase oil)

[0141] The elastomeric backing layer used in the AMS wound dressing described herein was 15 m Polyurethane Pink film (Inspire 2150) supplied by Coveris.

[0142] A series of tests were performed on the AMS wound dressing and the resulting Absorbency Free Swell, Retention under Load, MVTR, Total Fluid Handling, Extensibility, Permanent Set (%), Peel Adhesion (N/2.5 cm), Coefficient of Friction, Waterproofness and ConformabilityBending (mm) data can be found presented in Table 3 below.

TABLE-US-00003 TABLE 3 AMS wound Performance of Test dressing AMS wound dressing Absorbency Free Swell 33.8 Good absorbency performance (g/100 cm.sup.2) Retention under Load 25.8 Good retention performance (g/100 cm.sup.2) MVTR (g/m.sup.2/24 hrs) 2288 Excellent breathability performance Total Fluid Handling 8.3 AMS dressing demonstrates (g/10 cm.sup.2/24 hrs) excellent fluid handling Extensibility (N/cm) 3.0 Good extensibility force demonstrated Permanent Set (%) 1% Good elasticity Peel Adhesion (N/2.5 cm) 15.4 AMS dressing demonstrates good peel adhesion Thickness (mm) 2.48 AMS dressing has a slim and lightweight design Coefficient of Friction (N) 1.09 AMS dressing demonstrates a low friction profile (i.e. reduced rucking and pulling under clothing or bedsheets) Waterproofness YES AMS dressing is waterproof and prevents ingress of water or leakage of wound fluids Conformability - 19.1 AMS dressing demonstrates Bending (mm) low bending length trans- lating into excellent conformability around anatomical contours.

[0143] Table 4 presents certain test data for the AMS dressing for comparison against the Aquacel Ag Surgical dressing.

TABLE-US-00004 TABLE 4 Aquacel Ag AMS wound Test Surgical dressing Comparison comments MVTR 531 2288 AMS dressing (g/m.sup.2/24 hrs) demonstrates significantly improved breathability as compared to Aquacel. Total Fluid 6.3 8.3 AMS dressing Handling demonstrates improved (g/10 cm.sup.2/24 hrs) fluid handling Peel Adhesion 10.50 15.4 AMS dressing (N/2.5 cm) demonstrates improved adhesion (i.e. the dressing remains in place for intended wear time) as compared to Aquacel. Thickness (mm) 3.18 2.48 AMS dressing has a slimmer design and profile as compared to Aquacel. Longitudinal stretch Failure before No failure even AMS dressing shows test 100% stretch at 100% stretch significantly improved stretch properties Lateral stretch test Failure before No failure even AMS dressing shows 50% stretch at 100% stretch significantly improved stretch properties

[0144] As illustrated by the data in Table 4, the AMS wound dressing embodiment according to the present invention possesses at least superior MVTR, Total Fluid Handling, Peel Adhesion, thickness and stretch parameters as compared to the Aquacel Ag Surgical dressing.

[0145] Absorbency Free Swell

[0146] The absorbency free swell (i.e. the absorbency under no-load) data in Table 3 was obtained using a method which is aligned with BS EN13726-1:2002 Test method for primary wound dressings, part 1: aspects of absorbency, section 3.2, for use in R&D and QC laboratories. The procedure required the AMS wound dressing to be cut into 5 cm by 5 cm squares using a cutting die. A Petri dish was placed on a balance and the balance is tared. The sample of AMS dressing was then placed in the Petri dish and its mass recorded (W.sub.1). Then, 40 times the mass of the dressing of Solution A (a standard test solution used in wound care containing 142 millimoles of sodium ions and 2.5 millimoles of calcium ions dissolved in distilled water (made as per ISO 13726-1:2002)), pre-warmed to a temperature of 371 C., was added to the Petri dish.

[0147] The sample, in its Petri dish, was then placed into an environmental chamber at 371 C. for 301 minutes, recording the temperature at the start and end of the incubation. The samples were removed from the chamber and suspended by one corner for 30 seconds using forceps. The sample was weighed and the mass recorded (W.sub.2).

[0148] The absorbency of the AMS wound dressing sample was calculated according to the following formula:

Absorbency=(W.sub.2W.sub.1)4 (Units: g/100 cm.sup.2)

[0149] Retention Under Load

[0150] The retention under load data in Table 3 is a measure of how effectively the wound dressing retains wound exudate under pressure as it may be in use (e.g. under compression bandaging). The weight applied to the samples is between 1366.4 g and 1374.0 g and corresponds to a minimum pressure of 40 mmHg (equal to that applied by a compression bandage at the ankle in the case of venous leg ulcers). The procedure begins as described under Absorbency Free Swell, above. After W.sub.2 is obtained, the sample is placed in a tray with a mesh base, which is in turn placed in a larger collection tray. A 5 cm by 5 cm Perspex plate is placed squarely on the sample, onto which a stainless steel weight is placed for a period of 302 seconds. After removing the weight and Perspex plate, the sample is weighed to obtain W.sub.3.

[0151] The retention under load of the AMS wound dressing sample was calculated according to the following:

Retention=(W.sub.3W.sub.1)4 (Units: g/100 cm.sup.2)

[0152] Total Fluid Handling

[0153] The Total Fluid Handling (TFH), Moisture Vapour Transmission Rate (MTVR) and Fluid Absorbance data presented in Table 3 was obtained using a method which is aligned with ISO 13726-1:2002 Test Methods for Primary Wound DressingsPart 1: Aspects of Absorbent section 3.3 Fluid Handling Capacity. The procedure requires a circle of the AMS wound dressing to be cut to have a 55 cm diameter. The circle of AMS wound dressing was then attached to the flange of a Paddington Cup (a hollow cup with a 10 cm2 cross section) and secured in place with a retaining ring (e.g. screw top). The weight of the AMS wound dressing and the Paddington Cup is measured (W1) and recorded using a calibrated balance. Then 20m1 of Solution A is added to the Paddington Cup and the screw top applied. Solution A is a standard test solution used in wound care contains 142 millimoles of sodium ions and 2.5 millimoles of calcium ions dissolved in distilled water (made as per ISO 13726-1:2002). The Paddington Cup is positioned such that the adhesive side of the AMS wound dressing is in contact with Solution A. The Paddington Cup is then weighed again (W2) and the weight is recorded. The Paddington Cup is placed into a 37 C. environmental chamber for 24 hours. Upon removal, the Paddington Cup is left to stand for 30 minutes and the weight recorded (W3). The solution is drained and the Paddington Cup is inverted for 15 minutes before having the weight of the cup measured and recorded for the final time (W4).

[0154] The Moisture Vapour Transmission Rate (MVTR) and Fluid Absorbance for the AMS wound dressing sample was calculated according to the following.

MVTR=W2W31000 (Units: g/m2/24 hrs)

Fluid Absorbance=W4W1 (Units: g/10 cm2/24 hrs)

[0155] The total fluid handling is the sum of MVTR and Fluid absorbance values.

[0156] Peel Adhesion

[0157] The peel adhesion data was obtained using a method which is aligned with ASTM D6282-11.

[0158] A sample of the AMS wound dressing was cut to 25 mm100 mm using a cutting press and die. The sample was tape wrapped around one end to form a tab for use with the tensometer. A stainless steel plate was then cleaned with isopropyl alcohol wipes or acetone. The release liner of the cut sample is removed and the sample is applied to the stainless steel plate. The sample and plate were placed on a calibrated roll down machine at a speed of 12 inch/min. The stainless steel plate was mounted onto the test rig of a tensometer (Zwick model) so that the tab created is secured in the upper jaw at a 90 degree angle. The upper jaw was moved up, peeling the adhesive from the stainless steel plate at a rate of 254 mm/min. The maximum force and the average force are measured by the tensometer in Newtons.

[0159] Thickness Tests

[0160] The total thickness of the wound dressing is measured using a calibrated digital calliper and the measurement is recorded at three points on the dressing. The measurement is taken with release liners on wound facing surface of the dressing in order to avoid the equipment becoming tacky. This also reduces the risk of the calliper compressing the adhesive layer and thus giving a false lower reading. The release liners are then removed and measured using the same calliper at three points on the release liner. The final thickness of the wound dressing is calculated as the average thickness of the dressing (as measured with the release liners) minus the average thickness of the release liners.

[0161] Conformability Tests

[0162] The conformability data presented in Tables 3 above was obtained using the following method.

[0163] The method used to obtain the conformability presented herein is aligned with ISO EN 13426-4:2003 Test methods for primary wound dressingsPart 4: Conformability. This method sees a sample of the wound dressing cut in to a rectangular strip. For the AMS dressing the strip was cut from the fluted section of the wound dressing having a width of 2.5 cm. The strip then marked (i.e. has two pieces of tape wrapped around either of its ends) approximately 100 mm apart. The release liners of the dressing are then removed, if necessary, and the product is left to relax for a minimum of 300 seconds. The distance between the two pieces of tape is measured using a digital calliper and recorded as L1. The sample is then mounted into a tensometer (a Zwick Roell machine was used) and clamped into the jaws of the machine via the taped ends (the jaws are set to be 10 mm wider than the marks). The sample is extended by 20% at a rate of 300 mm/min and is held at the maximum extension for 60 seconds. The force to extend by 20% is recorded by the tensometer as the Fmax/Maximum force (Newtons). After 60 seconds the sample is released from the jaws of the tensometer and left to relax for a further 300 seconds. The distance between the taped ends is measured again using the digital callipers and recorded as L2.

[0164] Extensibility

[0165] Extensibility is defined as the force required to stretch a wound dressing sample to a known extension. To calculate the extensibility the Fmax is divided by 2.5 cm.

[0166] Permanent Set

[0167] Permanent set is defined as the increase in length of a sample after the stretching and relaxing expressed as a percentage of the original length. The permanent set is calculated as follows:

Permanent Set (%)=((L2L1)/L1)100

[0168] Conformability is an important factor for wound dressings that are in contact with the skin in the region of moveable joints, such as the elbow and knee, as the higher the conformability the better the ability of the wound dressing to adapt to the shape and movement of the body. The measurement of the permanent set provides an assessment of the memory of a wound dressing and ability of a wound dressing to flex and contract. The force required to stretch the wound dressing is also represented by the Fmax.

[0169] ConformabilityBending Length

[0170] Bending length is defined as the length of sample material of predetermined width that is pushed through the cantilever conformability tester (Shirley stiffness tester) when the tester reaches a bending angle of 41.5. The bending length data in Table 3 was obtained using a method aligned with ASTM D1388 Standard Test Method for Stiffness of Fabrics option ACantilever Test. A sample of the AMS dressing was cut to 25 mm wide and 140 mm long using a die cutter. The mass of the sample was determined using a calibrated balance and recorded (M).

[0171] The sample is aligned with the line scribed on the edge of the platform of the Shirley stiffness tester and the removable slide placed on the sample. The clamped sample is then moved by hand at a rate of approximately 120 mm/min 5% until the edge of the sample touches the knife edge, which is set at an incline of 41.5. The overhang length of the sample from the linear scale is measured to the nearest 0.1 cm and recorded.

[0172] The bending length of the AMS wound dressing sample was calculated according to the following equation:

Bending length=length of overhang/2 (Units: mm)

[0173] Stretch Force Tests

[0174] Stretch force tests were performed on the AMS wound dressing and the Aquacel Ag Surgical samples both in the longitudinal and cross direction. This was done to investigate the multidirectional stretching ability of the respective wound dressings.

[0175] Test rectangles 25 mm60 mm were cut from the samples ensuring that the central absorbent areas of the dressings were used. Any release liners were removed. The samples were then mounted onto a tensometer (a Zwick Roell machine was used) before then being stretched in the cross direction and the longitudinal direction. The strain profiles for each of the samples when stretched in the cross (lateral) direction and the longitudinal directions are measured as Force vs % Strain (see FIGS. 5-8). Each samples was tested twice.

[0176] As illustrated in FIG. 5, when stretched in the longitudinal direction, the AMS wound dressing exhibits a gradual increase in the force require to reach a 50% strain, which then plateaus and maintains substantially constant until a 100% strain is achieved. The maximum force achieved during the longitudinal stretching of the AMS wound dressing averaged at 21.3N. In contrast, as seen in FIG. 6, the Aquacel Ag Surgical sample in the longitudinal direction required lower forces during initial stretching to cause an increase in the strain. However, the Aquacel Ag Surgical ultimately required dramatic increase in the force above 60% strain before then reaching material failure. It is believed that this shows that the Aquacel Ag Surgical reached the elastic limit of its stitch-bonded configuration leading to the material failure.

[0177] As illustrated in FIG. 7, when stretched in the cross direction, the AMS wound dressing required a moderate force to effect strain in the initial period but without any material failure. The maximum force achieved during the cross direction stretching of the AMS wound dressing averaged at 28.2N. The gradual increase and decrease of the force required to achieve 100% strain suggests that an initial structural separation of fibres within the dressing occurred but without material failure. The Aquacel Ag Surgical sample in the cross (lateral) direction, as shown in FIG. 8, requires a rapid increase in force until the point of material failure which occurs before 50% strain has been achieved.

[0178] The data illustrated in FIGS. 5-8 illustrate the superior multidirectional stretching characteristics of the AMS wound dressing. FIGS. 5 and 7 show that the wound dressings of the present invention are able to reach 100% both in the longitudinal and lateral (cross) directions, requiring a moderate amount of force and without experiencing any material failure.

[0179] Coefficient of Friction The coefficient of friction of the exterior surface (i.e. outward or non-wound facing surface) of the backing layer within the AMS wound dressing was measured using a Zwick Roell Tensometer equipped with a 50N load cell and utilising the testXpert II software and method: WI-405 Coefficient of Friction. A sample of the AMS wound dressing was cut using a 63 by 100 mm rectangular die. The sample was wrapped around the metal plate with the surface to be analysed facing outwards, and clamped into place. The load cell was then connected to the metal plate via the thread. The force was then zeroed and the test begun. On completion of the measurement, the metal plate was removed and the sample disposed of.

[0180] Waterproofness

[0181] The waterproofness data presented in Table 3 above was obtained using the following method. The method used to obtain the waterproofness presented herein is aligned with standard method BS EN 13726-3:2003 Non-active medical devicestest methods for primary wound dressingsPart 3: Waterproofness. The procedure determines if the dressing is waterproof, waterproof being defined as being able to withstand a hydrostatic head of 500 mm of water for 5 minutes. The procedure requires a circle of the AMS wound dressing to be cut to have a diameter of 90 mm.

[0182] A rubber ring is placed on the circular opening of the cell, which is connected to a burette using appropriate tubing. The cell is filled with distilled/deionized water at 212 C. (dispensed at this temperature) to the top of the rubber ring using the burette. Any water present on the cell or rubber ring is then dried and any air bubbles in apparatus removed to ensure there are no impediments to the flow of water. The dressing was slid onto the rubber ring with the external side in contact with the rubber ring. A clean, dry filter paper was attached to the wound contact side of the dressing and a second rubber ring placed over the top. A metal ring was placed over the second rubber ring and secured with four G-cramps.

[0183] The burette was filled with water and the system left for 5 minutes. After this time the filter paper was examined for water penetration. If water was present on the filter paper, the dressing had failed the test as water had penetrated it. If water was not present on the filter paper, the dressing has passed the test as water had not penetrated it.

[0184] It will be appreciated that numerous modifications to the above described wound dressing and use may be made without departing from the spirit and scope of the invention, for instance, the scope of the invention as defined in the appended claims. Moreover, it is intended that any one or more of the above described embodiments could be combined with one or more features of the other embodiments and all such combinations are intended within the present disclosure.

[0185] Optional and/or preferred features may be used in other combinations beyond those explicitly described herein and optional and/or preferred features described in relation to one aspect of the invention may also be present in another aspect of the invention, where appropriate.

[0186] The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the scope of the inventions as defined in the claims are desired to be protected.

[0187] It should be understood that while the use of words such as preferable, preferably, preferred or more preferred in the description suggest that a feature so described may be desirable, it may nevertheless not be necessary and embodiments lacking such a feature may be contemplated as within the scope of the invention as defined in the appended claims. In relation to the claims, it is intended that when words such as a, an, or at least one, are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim.