Wound dressing

Abstract

A negative pressure wound dressing having a backing layer, an adhesive border skin contact layer, and an absorbent structure arranged between the backing layer and the adhesive skin contact layer wherein the absorbent structure comprises a plurality of absorbent layers and a transmission layer, and at least two of the layers in the absorbent structure are laminated together, wherein a first absorbent layer comprises a non-woven fabric having 60 to about 95 wt% gelling fibres and 5 to about 40 wt% non-gelling fibres, of the absorbent layer and wherein a second absorbent layer is located between the first absorbent layer and the transmission layer. Manufacturing processes and applications of said dressing are also described.

Description

WOUND DRESSINGFIELD

[0001] The present disclosure relates generally to textile compositions, and more particularly to nonwoven textile compositions for use in negative pressure wound dressings.BACKGROUND

[0002] Owing to an aging population and growing prevalence of vasculopathy, the incidence of chronic wounds is increasing worldwide. Chronic wounds are a major burden on healthcare systems and patient quality of life, often leading to loss of function and amputation. Although their treatment accounts for approximately 3% of total healthcare costs in developed countries, a 2018 cohort study found that fewer than 50% of chronic wounds managed by the UK National Health Service healed within a year. Moreover, chronic wounds recur in up to 60-70% of patients. This poor prognosis underlines the need for new approaches to chronic wound care.

[0003] Normal wound healing comprises four intricate and overlapping phases: haemostasis, inflammation, proliferation, and remodelling. After the formation of a thrombus, leukocytes infiltrate the wound and remove bacteria and debris, preparing the wound for healing. This enables the formation of new connective tissue and blood vessels, known as granulation tissue, and subsequent wound closure and re-epithelialisation. A wound is classed as chronic if it fails to progress through this sequence within 4-6 weeks. Wound chronicity is often attributed to diabetes and vascular diseases. The resulting nerve damage and poor perfusion to extremities alter the wound microenvironment and delay healing. Chronic wound healing stalls in the inflammatory phase due to an imbalance of cytokines, proteases, and their inhibitors. Prolonged inflammation leads to the accumulation of slough, a fibrinous substance composed of dead leukocytes and degraded proteins.

[0004] Microbial infection occurs in almost all wounds and is a significant cause of chronicity. Bacteria adhere to necrotic tissue in the wound bed and form microcolonies that secrete extracellular polymeric substances (EPS). The bacteria become encased in an EPS matrix which eventually matures into a complex biofilm composed of proteins, polysaccharides, nucleic acids, metal ions, and lipids. Biofilm sequesters antimicrobials and inhibits the activation of phagocytes, providing resistance to both antimicrobials and the host immune system. Moreover, biofilm in the wound bed impedes the migration and function of keratinocytes, leukocytes, and fibroblasts, preventing the normal inflammatory response and subsequent healing processes. The recalcitrant biofilm perpetuates aninflammatory cycle wherein tissue is degraded more quickly than it is produced, preventing the progression of healing.

[0005] Biofilm is believed to exist in up to 80% of chronic wounds and is a direct cause of wound chronicity. Slough, and other non-viable matter, delays the formation of granulation tissue and facilitates the development of biofilm. It is evident that for any wound to successfully heal, biofilm and necrotic tissue must be removed from the wound bed. Ideal wound management involves the reduction of microorganisms and necrotic tissue to levels that can be managed by the host immune system, without inducing damage to healthy tissues nor bacterial resistance. Standard wound care involves cleansing the wound to remove loosely attached debris and bacteria, followed by the removal of necrotic tissue (debridement), and finally dressing application. Dressings optimise the healing environment by balancing moisture levels, preventing infection, and removing debris. However, wounds should be irrigated between dressing changes to remove any debris and biofilm that may have sloughed off onto the dressing. With little clinical evidence supporting the use of more specialised cleansing materials, normal saline is often used to irrigate wounds due to its high biocompatibility. However, saline is non-antimicrobial and is ineffective at removing biofilm from necrotic wounds. Broad-spectrum antiseptics are frequently used to control wound infection but are often cytotoxic due to their lack of selectivity. Selective antibiotics may be more effective at preserving host tissue, but their repeated use catalyses antibiotic resistance. Moreover, owing to the sequestration properties of EPS, the single use of antimicrobials to combat wound infection has been largely unsuccessful.

[0006] WO 2021 / 186188 Al describes a wound dressing comprising an absorbent layer impregnated or coated with a composition comprising a chelating agent, an amphoteric surfactant, and an anionic surfactant.

[0007] However, there remains a need for further improvements in wound dressings that are able to promote autolytic (spontaneous, biochemically-mediated) debridement of non-viable tissue, while having physical modes of action against biofilms and the microorganisms comprised therein. In particular, there is a need for wound dressings that are simple, economical and safe to use while maintaining efficacy and suitability for use in wound dressings for the purposes discussed above. Moreover, there is also a need for wound dressings with good stability, e.g. during storage, prior to application on a wound dressing to ensure good uniformity and consistency in manufactured articles, and during use, for example when saturated with wound exudate.

[0008] Negative pressure has been used to treat a range of chronic and acute wounds. Negative pressure may facilitate wound healing through a number of mechanisms, including removal of excessexudate, reduction in periwound edema and increased perfusion. Combined with the physical forces exerted by the negative pressure which draw the wound edges together, this can result in improved wound outcomes.

[0009] Wound dressings typically comprise an adhesive skin contact layer for detachably adhering the dressing to a dermal surface. Conventionally, the adhesive skin contact layer comprises a plurality of perforations (i.e., through holes in the adhesive skin contact layer) which enable fluid, for example wound exudate, to flow through the layer but which prevent tissue ingrowth into other material comprised in the wound dressing. Typically, the perforations have a diameter of no more than 1.2mm to facilitate adhesion of the skin contact layer to the dermal surface and to provide a skin contact layer with sufficient breathability, i.e., allowing water vapour and gas to pass through the layer. Typically, the skin contact layer comprises a silicone adhesive. Disadvantageously, some of the perforations are prone to closing, or at least reducing in diameter, after formation due to the silicone adhesive entering and, therefore, blocking the perforations. While this may increase adhesion of the layer to the dermal surface, this adversely affects the breathability of the skin contact layer, causing an accumulation of bodily fluid at and in proximity to the skin or wound site, therefore, preventing the formation of an environment optimised for wound healing. Conversely, it is known to increase the size of perforations in an adhesive skin contact layer to aid breathability. However, this is achieved at the expense of adhesion of the skin contact layer to a dermal surface and in such cases, the skin contact layer may only weakly adhere to a dermal surface such that movement of a patient while the wound dressing is adhered may cause the wound dressing to partially or completely detach from the patient, adversely affecting the dressing to transmit a negative pressure to the wound site.

[0010] Conventional techniques to form the perforations in the adhesive layer include using a hot pin process. However, disadvantageously, this results in the formation of 'slugs' around the perforation (i.e., the material intended to be removed to form the perforation is not wholly disconnected from the main body of material and, therefore, partially obstructs the perforation and results in a non-planar surface of the skin contact layer). To overcome this, ultrasound may be used to create the perforations. However, this process disadvantageously forms doughnut / volcano structure around the perforations.

[0011] Portable systems have been developed which include a means to manage the exudate produced by the wound by collecting exudate within the wound dressing, typically in an absorbent material, and by evaporation through the dressing. Such systems mean that a separate collection canister may not be an essential part of the system. An advantage of not needing a canister is that the device is less bulky and more portable. A disadvantage with such devices is that if the dressingexceeds its fluid handling capacity, exudate may be drawn from the absorbent material(s) and enter the pump. The presence of exudate in the pump will eventually cause it to fail and require its replacement. The therapy provided by the system may also be less than optimal due to the potential for excess exudate to collect, or pool, at the wound interface. In order to prevent fouling of the pump with exudate, it is known to provide a barrier layer between the absorbent material and the pump. However, the liquid barrier layer does not improve the ability of the absorbent material(s) to absorb exudate.

[0012] Wound contact layers are known to comprise a mixture of gelling and non-gelling fibres. Gelling fibres form a gel upon contact with exudate. However, upon forming a gel, many wound contact layers weaken and in some cases partially dissociate from other layers comprised in an absorbent structure. To overcome this, it is known to provide non-gelling fibres as part of the wound contact surface of the wound contact layer. Such arrangements aim to strike a balance between providing a sufficient amount of gelling fibres and preventing dissociation of the wound contact layer when it becomes wet with exudate.

[0013] However, known wound contact layers fail to adequately strike this balance and such layers either do not adequately prevent pooling of exudate at the wound contact surface or do not adequately adhere to other layers within the wound dressing when the wound contact layer becomes wet with exudate.

[0014] During negative pressure therapy, air as well as wound exudate material is removed from a wound site. The wound exudate must be collected remotely from the wound site. Some known negative pressure therapy systems comprise a waste canister connected to a pump unit for the collection and storage of wound exudate material. However, the use of a canister can result in the therapy system itself being bulky and expensive to manufacture. Also, replacing a canister or a container in a canister in which wound exudate is collected can be a time consuming and a relatively unhygienic process.

[0015] Some negative pressure wound dressings have been produced which comprise an absorbent layer to absorb wound exudate in an attempt to remove the need for a canister and pump system. However, such wound dressings often fail to sufficiently meet two requirements of an absorbent layer in a wound dressing, i.e., that the absorbent layer has a high absorbance capacity and remains flexible (i.e., does not stiffen) when it absorbs wound exudate which subsequently dries.

[0016] Known absorbent layers with a relatively low absorbance capacity cause pooling of wound exudate at the wound site. This is both uncomfortable and unhygienic for the patient and for ahealthcare professional who replaces the wound dressing. Moreover, there is a risk that the wound and / or surrounding skin will become macerated if in prolonged contact with excess wound exudate.

[0017] Moreover, known absorbent layers often become relatively stiff when wound exudate has been absorbed and subsequently dried. This results in the fabric of the absorbent layer 'doming' which, disadvantageously, provides a tunnel effect of air transfer and causes air to leak from the wound dressing, thereby adversely affecting the negative pressure transmitted to the wound site.

[0018] Conventional negative pressure wound dressings often comprise relatively rigid dressing and binding components which adversely affects system utility and which provides a relatively rigid wound dressing which is disadvantageous in respect of user comfort. Moreover, such components require individual manufacturing steps to incorporate them into the wound dressing, therefore, increasing the time of manufacture and cost.

[0019] The purpose of such components is to attempt to increase the integrity of the wound dressing to prevent, or at least reduce, dissociation of one or more of the layers comprised therein. However, the advantages of such components often do not outweigh the disadvantages associated with the additional manufacturing steps, complex processing and the rigidity of the final wound dressing. Further, the rigid dressing and binding components often have an adverse effect on the wicking, or movement, of wound exudate through the wound dressing away from the wound site. Additionally, existing negative pressure wound dressing systems do not utilise absorbent materials and additional wound dressing components arranged to maximise the management of wound exudate within the dressing.

[0020] It is known to provide a wound dressing comprising a wound contact layer, a transmission layer and an absorbent layer, arranged such that the transmission layer overlies the wound contact layer, and the absorbent layer overlies the transmission layer. This arrangement is disclosed in US 10,507,141. However, such an arrangement does not provide a significant absorbency capacity. This means that the arrangement suffers from unnecessary pooling of wound exudate at the wound site. As such, the hygiene of the wound dressing and of the wound site could be improved which in turn would increase comfort for the user.

[0021] The present disclosure seeks to address these needs with the various aspects and embodiments defined herein.SUMMARY

[0022] In a first aspect, there is provided a negative pressure wound dressing, the dressing comprising:a backing layer, an adhesive border skin contact layer, and an absorbent structure arranged between the backing layer and the adhesive skin contact layer; wherein the adhesive skin contact layer is configured to detachably adhere the dressing to a dermal surface; wherein the backing layer comprises a coupling member configured to connect the dressing to a negative pressure source; wherein the absorbent structure comprises a plurality of absorbent layers and a transmission layer, and at least two of the layers in the absorbent structure are laminated together; wherein a first absorbent layer comprises a non-woven fabric, wherein the non-woven fabric comprises gelling fibres and non-gelling fibres, wherein the gelling fibres are present in an amount of from about 60 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 40 wt% of the first absorbent layer; and wherein a second absorbent layer is located between the first absorbent layer and the transmission layer or the transmission layer is arranged between the first absorbent layer and the second absorbent layer.

[0023] In a further aspect, there is provided a process for preparing a negative pressure wound dressing as defined herein, wherein the process comprises the steps: (a) Providing an adhesive skin contact layer and a backing layer; (b) Providing a first absorbent layer, a transmission layer and a second absorbent layer; (c) Adhering together at least two of the first absorbent layer, the transmission layer and the second absorbent layer to form an absorbent structure; and (d) Arranging the absorbent structure between the adhesive skin contact layer and the backing layer; wherein, in step c, each of the first absorbent layer, the transmission layer and the second absorbent layer are adhered together by lamination.

[0024] In a further aspect, there is a kit comprising a backing layer and an absorbent structure for a negative pressure wound dressing as defined herein.

[0025] In a further aspect, the use of the wound dressing as defined herein is provided for negative pressure wound therapy.

[0026] These aspects and embodiments are set out in the appended independent and dependent claims and discussed further herein. It will be appreciated that features of the dependent claims may be combined with each other and with features of the independent claims in combinations other than those explicitly set out in the claims. Furthermore, the approaches described herein are not restrictedto specific embodiments such as those set out below, but include and contemplate any combinations of features presented herein.

[0027] The foregoing and other objects, features, and advantages of the present disclosure will appear more fully hereinafter from a consideration of the detailed description that follows along with the accompanying drawings. It is to be expressly understood, however, that the drawings are for illustrative purposes and are not to be construed as defining the limits of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Fig. 1: Scatter graph -Textile Performance (Trial 2): Absorbency vs Wet Tensile Strength

[0029] Fig. 2: Scatter graph - Textile Performance (Trial 3): Absorbency vs Wet Tensile Strength (Machine Direction).

[0030] Fig. 3: Scatter graph - Textile Performance (Trial 4): Absorbency vs Wet Tensile Strength (Machine Direction).

[0031] Fig. 4: Fluid Handling Comparative Study - Fluid Absorbance and Fluid Retention

[0032] Fig. 5: Wicking Distance Comparative Study

[0033] Fig. 6: Tensile Strength (Wet) Comparative Study

[0034] Fig. 7: Absorption under Compression Comparative Study

[0035] Fig. 8: Tensile Strength (Dry) Comparative Study

[0036] Fig. 9: Tensile Strength Variation Graph - Effect of Carboxymethylcellulose (Hydrofibre) Content

[0037] Fig. 10: Dimensional Shrinkage Comparative Study

[0038] Fig. 11: Exploded view of an exemplary negative pressure wound dressing

[0039] Fig. 12: Plan view of an exemplary negative pressure wound dressing

[0040] Fig. 13: Exploded view of the negative pressure wound dressing of Fig. 12

[0041] Fig. 14: Negative pressure wound simulation apparatus - schematic diagram

[0042] Fig. 15: Exudate flow illustration (Backing side)

[0043] Fig. 16: Exudate flow illustration (Wound side)Fig. 17: Exudate flow illustration (Wound side)DETAILED DESCRIPTION

[0044] While various exemplary embodiments are described or suggested herein, other exemplary embodiments utilizing a variety of methods and materials similar or equivalent to those described or suggested herein are encompassed by the general inventive concepts. Those aspects and features of embodiments which are implemented conventionally may not be discussed or described in detail in the interests of brevity. It will thus be appreciated that aspects and features of apparatus and methods described herein which are not described in detail may be implemented in accordance with any conventional techniques for implementing such aspects and features.

[0045] As used in this specification and the claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Unless otherwise stated, the term "about" modifying the quantity of a component refers to variation in the numerical quantity that can occur, for example, through typical measuring and handling procedures used for making concentrates, mixtures or solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the materials employed, or to carry out the methods; and the like. The term "about" also encompasses amounts that differ due to different equilibrium conditions for a composition or substance resulting from a particular initial mixture. Whether or not modified by the term "about", the claims include equivalents to the quantities. As used herein, the term "at least" includes the end value of the range that is specified. For example, "at least 10 wt%" includes the value 10 wt%.

[0046] As used in this specification and the claims, "gel-forming fibres" and "gelling fibres" may be used interchangeably. Similarly, references in this specification and the claims to "non-gel forming fibres" and "non-gelling fibres" can be used interchangeably.

[0047] The ranges provided herein provide exemplary amounts of each of the components. Each of these ranges may be taken alone or combined with one or more other component ranges.

[0048] As used herein, wt% means "weight percentage" as the basis for calculating a percentage. Unless indicated otherwise, all % values are calculated on a weight basis, and are provided with reference to the total weight of the product in which the substance is present. As used herein, w / w means "weight by weight" as the basis for calculating a percentage. Unless otherwise indicated,reference to "% by weight" (or "% by weight") of a product, substance or composition reflects the total wet weight of the product or composition (i.e., including water).

[0049] In various embodiments described herein, amounts may be described as an area density using the units g / m2. In such embodiments, the area density refers to the area of a first absorbent layer as further described herein and the weight of the specified component comprised in or on said first absorbent layer. For example, in various embodiments the composition may be applied to a negative pressure wound dressing as described herein with an area density of 30 g / m2or 15 g / m2. An exemplary negative pressure wound dressing may comprise a first absorbent layer of dimensions 10 x 10 cm, giving an area of 0.01 m2. Thus, for the example wherein the first absorbent layer has an area of 0.01 m2, 0.3 g of a composition as described herein would be applied to the first absorbent layer to obtain an area density of 30 g / m2. The composition may be applied to a single surface of the first absorbent layer, for example in embodiments wherein the first absorbent layer is comprised in a multilayer negative pressure wound dressing. Alternatively, the composition may be applied to a first surface of the first absorbent layer and to a second surface of the first absorbent layer opposite to the first surface of the first absorbent layer. In such embodiments wherein the composition is applied to a first and second surface of the first absorbent layer, the composition may be applied to the negative pressure wound dressing as described herein to contribute 15 g / m2on each of the first and second surfaces, i.e. such that the total area density applied to the first absorbent layer is 30 g / m2. In other words, the area densities recited herein refer to the total area density of composition applied to the first absorbent layer, calculated on the basis of the area defined by the dimensions (width and length) of the first absorbent layer and the total amount of the composition applied thereto, whether applied only to a single surface of the first absorbent layer or applied to both a first surface and a second surface of the first absorbent layer. Thus, for the example wherein the first absorbent layer has an area of 0.01 m2(10 x 10 cm), 1.5 g of a composition as described herein could be applied to the first surface of the first absorbent layer and 1.5 g of the composition applied to the second surface of the first absorbent layer to obtain a total area density of 30 g / m2.

[0050] As used herein, "substantially free" means no more than trace amounts, i.e. the amount of the substance(s) concerned is negligible. In various embodiments, "substantially free" means no more than 1000 ppm, preferably no more than 100 ppm, more preferably no more than 10 ppm, even more preferably no more than 1 ppm of the substance(s) concerned.

[0051] In all aspects of the present disclosure, the disclosure includes, where appropriate, all enantiomers and tautomers of the compounds disclosed herein. A person skilled in the art will recognise compounds that possess optical properties (one or more chiral carbon atoms) or tautomericcharacteristics. The corresponding enantiomers and / or tautomers may be isolated / prepared by methods known in the art.

[0052] Some of the compounds disclosed herein may exist as stereoisomers and / or geometric isomers - e.g. they may possess one or more asymmetric and / or geometric centres and so may exist in two or more stereoisomeric and / or geometric forms. The present disclosure contemplates the use of all the individual stereoisomers and geometric isomers of those compounds, and mixtures thereof. The terms used in the claims encompass these forms.

[0053] As used in this description and the claims, the phrase "wound contact layer" is used in a broad manner to describe a negative pressure wound dressing layer that is suitable for contacting a wound bed in part or in its entirety. It is well known that further layers and / or components may optionally exist between a wound site and the wound contact layer, for example an adhesive layer to aid in application of the negative pressure wound dressing to the wound site. Thus, wound contact layers do not preclude the use of further dressing layers and / or components between said wound contact layer and the wound bed.

[0054] For the avoidance of any doubt, reference to "wound contact layer" is used interchangeably with "first absorbent layer", i.e. the first absorbent layer comprising a non-woven fabric.

[0055] As used herein the expression "wound" may include an injury to living tissue and may be caused by a cut, blow, or other impact, abrasion, pressure, heat or chemical; typically, one in which the skin is cut or broken. A wound may often be described as chronic or acute. Acute wounds may occur as a result of surgery or trauma. Typically, when not too severe and where the victim is otherwise in good health, wounds progress through well-defined stages of healing within a predicted timeframe. Chronic wounds begin as acute wounds. An acute wound can become a chronic wound when it does not follow the normal healing pathway resulting in a lengthened recovery. It is believed that the transition from acute to chronic wound can be due to an inadequate immune response for example: the patient being immuno-compromised, the wound being insufficiently perfused or being highly contaminated.

[0056] Chronic wounds may include for example: venous ulcers (such as those that occur in the legs due to venous insufficiency), which account for the majority of chronic wounds and mostly affect the elderly; diabetic ulcers (for example, foot or ankle ulcers), arterial ulcers (due to peripheral arterial disease); and pressure injuries due to immobility.

[0057] Wounds may also include a deep tissue injury. Deep tissue injury is a term proposed by the National Pressure Ulcer Advisory Panel (NPUAP) to describe a unique form of pressure ulcers. These ulcers have been described by clinicians for many years with terms such as purple pressure ulcers, ulcers that are likely to deteriorate and bruises on bony prominences.

[0058] The term "slough" is known to the skilled person and may be defined as a layer or mass of dead tissue separated from surrounding living tissue, or tissue that is adhered to a wound but capable of being removed as in a wound, sore, or inflammation.

[0059] Reference to a "second absorbent layer" is used interchangeably with "superabsorbent layer", i.e. the layer located between the first absorbent layer / wound contact layer and the transmission layer or between the transmission layer and the backing layer. It will, however, be understood that the present disclosure is not limited to a superabsorbent layer as the second absorbent layer, just that this represents a preferred embodiment thereof.

[0060] Reference herein to a "wound dressing" generally is to be construed as a dressing that is suitable for use in negative pressure wound therapy.NEGATIVE PRESSURE WOUND DRESSING

[0061] Acute wounds occur as a result of surgery or trauma, typically when not too severe and where the subject is otherwise in good health. Wounds progress through well-defined stages of healing. Chronic wounds begin as acute wounds. For example, an acute wound can become a chronic wound when it does not follow the normal healing pathway resulting in a lengthened recovery. It is believed that the transition from acute to chronic can be due to an inadequate immune response, for example the patient being immuno-compromised, the wound being insufficiently perfused or being highly contaminated. Chronic wounds may include venous ulcers, diabetic ulcers, arterial ulcers, and pressure injuries due to immobility. Wounds may also include a deep tissue injury; this is an expression used to describe a unique form of pressure ulcers.

[0062] Negative pressure wound dressings are articles suitable for placement in direct contact with a wound and subject to the application of negative pressure. A wound may typically debride by autolysis. Autolytic debridement refers to the lysis or breakdown of necrotic debris and devitalised tissues from a wound through the body's own mechanisms, such as moist environments and endogenous enzymes. As described herein, the substances and compositions of the present disclosure are useful for the treatment of wounds, including initial treatment in first response settings, as well as in ongoing wound management such as in primary care settings.

[0063] In various embodiments, the negative pressure wound dressing comprises at least one layer comprising a foam, fabric (preferably a nonwoven fabric), or technical substrate. For example, the substrate may be a nonwoven or woven fibrous layer, a gel-forming fibre, or gauze. Gauze may be made from a cellulose, such as cotton or viscose. In preferred embodiments the first absorbent layer comprises one or more gel-forming fibres.

[0064] The use of nonwoven fabrics in wound dressings is well known, with several products available on the market, such as the AQUACEL® Extra™ range of dressings manufactured and sold by Convatec Ltd and Convatec Inc. For optimum performance the fabric structure requires a flat surface to ensure a controlled dose of excipients can be applied to and delivered by the fabric surface, while the fabric should also maintain a high degree of wet and dry tensile strength, absorbency, and conformability. However, a compromise typically has to be struck when seeking to provide a negative pressure wound dressing with the aforementioned properties, on the basis that a solution to improving one property, such as tensile strength, often impacts another property of the nonwoven fabric material, such as absorbency and / or conformability, and the wound dressing must also be suitable for use with negative pressure. The skilled person understands that fabric conformability relates to the ability of a fabric material to conform to a contoured area, such as a wound site. By way of illustration, nonwoven fabrics can be strengthened by using stitchbonding, as is the case with AQUACEL® Extra. AQUACEL® Extra is a nonwoven dressing with longitudinal warp stitching and internal transverse weft stitching. Stitchbonding requires that a textile yarn is knitted throughout the nonwoven fabric, a process that can reduce manufacturing efficiency. Furthermore, such bonding results in an irregular fabric surface, due to the formation of creases along the stitchbonding axis. This, effects the uniform application of substances to the fabric surface, which results in the uncontrolled dose of excipients to the nonwoven fabric.

[0065] As disclosed herein, the inventors arrived at an optimal nonwoven textile composition that provided good wet and dry tensile strength, absorbency, and conformability, yet did not require stitchbonding. According to the present invention, a wound dressing is provided comprising an first absorbent layer, wherein the first absorbent layer comprises a nonwoven fabric, the nonwoven fabric comprising gelling fibres and non-gelling fibres, wherein the gelling fibres are present in an amount of from about 60 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 40 wt% of the first absorbent layer.

[0066] In various embodiments, the gelling fibres are present in an amount of from about 65 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 35 wt% of the first absorbent layer. In various embodiments, the gelling fibres are presentin an amount of from about 70 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 30 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 75 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 25 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 80 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 20 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 85 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 15 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 90 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 10 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 65 to about 90 wt% of the first absorbent layer and the nongelling fibres are present in an amount of from about 10 to about 35 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 70 to about 90 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 10 to about 30 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 75 to about 90 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 10 to about 25 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 80 to about 90 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 10 to about 20 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 85 to about 90 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 10 to about 15 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 65 to about 85 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 15 to about 35 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 70 to about 85 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 15 to about 30 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 75 to about 85 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 15 to about 25 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 80 to about 85 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 15 to about 20 wt% of the first absorbent layer. In various embodiments, the gelling fibresare present in an amount of from about 90 to about 85 wt% of the first absorbent layer and the nongelling fibres are present in an amount of from about 15 to about 10 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 65 to about 80 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 20 to about 35 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 70 to about 80 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 20 to about 30 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 75 to about 80 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 20 to about 25 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 85 to about 80 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 20 to about 15 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 90 to about 80 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 20 to about 10 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 65 to about 75 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 25 to about 35 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 70 to about 75 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 25 to about 30 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 80 to about 75 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 25 to about 20 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 85 to about 75 wt% of the first absorbent layer and the nongelling fibres are present in an amount of from about 25 to about 15 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 90 to about 75 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 25 to about 10 wt% of the first absorbent layer.

[0067] By gelling fibres or gel forming fibres it is meant hygroscopic fibres that upon the uptake of wound exudate become moist slippery or gelatinous. The gel forming fibres can be of the type that retain their structural integrity on absorption of exudate or can be of the type that lose their fibrous form and become an amorphous or structureless gel. The gel forming fibres are typically sodium carboxymethylcellulose fibres, chemically modified cellulosic fibres, alkyl sulphonate modified cellulosic fibres, such as those described in WO2012 / 061225, pectin fibres, alginate fibres, chitosanfibres, hyaluronic acid fibres, or other polysaccharide fibres or fibres derived from gums, as well as non-cellulose synthetic fibres such as poly(vinyl alcohol) and polyacrylate.

[0068] The gelling fibres are typically chemically modified cellulosic fibres in the form of a fabric and in particular carboxymethylated cellulose fibres, as described in PCT WO00 / 01425. Sodium carboxymethylcellulose fibres typically have a degree of substitution of at least 0.05 carboxymethyl groups per glucose unit. The gelling fibres typically have an absorbency of at least 2 grams (or at least 8 grams, or at least 10 grams), 0.9% saline solution (Solution A) per gram of fibre (as measured by BS EN 13726-1 (2002) " Test methods for primary wound dressings", section 3.2 " Free swell absorptive capacity"). The carboxymethylated cellulosic fabrics typically have a degree of substitution between 0.12 to 0.35 (as defined in WO00 / 01425), more typically a degree of substitution of between 0.20 and 0.30, such that the absorbency of a fabric produced from is increased when compared to the unmodified cellulose. Particular useful fabrics have an absorbency of from about 10 g / g to about 30 g / g of isotonic aqueous solution as measured by the method described in BS EN 13726-1 (2002).

[0069] In various embodiments, the gelling fibres are selected from: carboxymethylcellulose fibres and derivatives thereof, modified cellulosic fibres, alkyl sulphonate modified cellulosic fibres, pectin fibres, alginate fibres, chitosan fibres, hyaluronic acid fibres, fibres derived from gums, non-cellulose synthetic fibres, superabsorbent fibres, such as polyacrylate fibres, and combinations thereof.

[0070] In a preferred embodiment, the gelling fibres are carboxymethylcellulose fibres or derivatives thereof (e.g. HYDROCEL™).

[0071] In various embodiments, the non-gelling fibres are selected from synthetic fibres, semisynthetic fibres, non-synthetic fibres or combinations thereof.

[0072] In various embodiments, the non-gelling fibres are selected from: cellulosic fibres, modified cellulosic fibres, polyester fibres, polypropylene fibres, polyamide fibres, or combinations thereof.

[0073] In a preferred embodiment, the non-gelling fibres are cellulosic fibres, modified cellulosic fibres (such as viscose / rayon), or a combination thereof. Highly preferred non-gelling fibres are lyocell fibres (e.g. LYOCELL™).

[0074] In various embodiments, the gelling fibres and non-gelling fibres are present in the non-woven fabric at a weight ratio of from about 85:15 to about 65:35. In a various embodiments, the gelling fibres and non-gelling fibres are present in the non-woven fabric at a weight ratio of about 80:20 toabout 70:30. In a preferred embodiment the gelling fibres and non-gelling fibres are present in the non-woven fabric at a weight ratio of about 75:25.

[0075] In various embodiments, the first absorbent layer(s) has a basis weight of about 150 - 200 gsm. In various embodiments, the first absorbent layer(s) has a basis weight of about 160 - 185 gsm.

[0076] In various embodiments, the nonwoven fabric has a basis weight of about 150 - 200 gsm. In various embodiments, the nonwoven fabric has a basis weight of about 160 - 185 gsm.

[0077] In various embodiments, the first absorbent layer disclosed herein may have a thickness between about 0.5mm to about 20mm. In various embodiments, the first absorbent layer disclosed herein may have a thickness between about 1mm to about 10mm. In various embodiments, the first absorbent layer disclosed herein may have a thickness between about 1.5mm to about 7 mm.

[0078] In various embodiments, the first absorbent layer(s) has a bulk density of about 25 - 100 kg / m3. In various embodiments, the first absorbent layer(s) has a bulk density of about 35 - 90 kg / m3. In various embodiments, the first absorbent layer(s) has a bulk density of about 40 - 80 kg / m3.

[0079] In various embodiments, the nonwoven fabric has a bulk density of about 25 - 100 kg / m3. In various embodiments, the nonwoven fabric has a bulk density of about 35 - 90 kg / m3. In various embodiments, the nonwoven fabric has a bulk density of about 40 - 80 kg / m3.

[0080] In various embodiments, the first absorbent layer has a fluid absorbency of about 0.05g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.10g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.15g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.20g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.25g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.30g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.35g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.40g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.45g / cm2or more.

[0081] In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.05g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.10g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.15g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.20g / cm2ormore. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.25g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.30g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.35g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.40g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.45g / cm2or more.

[0082] In various embodiments, the first absorbent layer has a fluid retention of at least about 45%. In various embodiments, the first absorbent layer has a fluid retention of at least about 55%. In various embodiments, the first absorbent layer has a fluid retention of at least about 65%. In various embodiments, the first absorbent layer has a fluid retention of at least about 75%. In various embodiments, the first absorbent layer has a fluid retention of at least about 85%. In various embodiments, the first absorbent layer has a fluid retention of at least about 90%. In various embodiments, the first absorbent layer has a fluid retention of at least about 95%.

[0083] In various embodiments, the nonwoven fabric has a fluid retention of at least about 45%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 55%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 65%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 75%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 85%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 90%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 95%.

[0084] In various embodiments, the first absorbent layer has a lateral wicking distance of no more than about 40 mm in the machine direction and in the transverse direction. In various embodiments, the first absorbent layer has a lateral wicking distance of no more than about 30 mm in the machine direction and in the transverse direction. In various embodiments, the first absorbent layer has a lateral wicking distance of no more than about 25 mm in the machine direction and in the transverse direction. In various embodiments, the first absorbent layer has a lateral wicking distance of no more than about 20 mm in the machine direction and in the transverse direction.

[0085] In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.10 g / cm2. In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.12 g / cm2. In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.14 g / cm2. In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.16 g / cm2. In variousembodiments, the first absorbent layer has an absorption under compression of at least about 0.18 g / cm2. In various embodiments, the absorbent layer has an absorption under compression of at least about 0.20 g / cm2. In various embodiments, the absorbent layer has an absorption under compression of at least about 0.22 g / cm2. In various embodiments, the absorbent layer has an absorption under compression of at least about 0.24 g / cm2. In various embodiments, the absorbent layer has an absorption under compression of at least about 0.26 g / cm2.

[0086] In various embodiments, the absorbent layer(s) has a dimensional shrinkage of no greater than about 25 % in the machine direction and in the transverse direction. In various embodiments, the absorbent layer(s) has a dimensional shrinkage of no greater than about 20 % in the machine direction and in the transverse direction. In various embodiments, the absorbent layer(s) has a dimensional shrinkage of no greater than about 15 % in the machine direction and in the transverse direction. In various embodiments, the first absorbent layer(s) has a dimensional shrinkage of no greater than about 10 % in the machine direction and in the transverse direction.

[0087] In various embodiments, the first absorbent layer(s) has a wet tensile strength of at least about 1.0 N / cm. In various embodiments, the first absorbent layer(s) has a wet tensile strength of at least about 2.0 N / cm. In various embodiments, the first absorbent layer(s) has a wet tensile strength of at least about 3.0 N / cm. In various embodiments, the first absorbent layer(s) has a wet tensile strength of at least about 4.0 N / cm. In various embodiments, the first absorbent layer(s) has a wet tensile strength of at least about 5.0 N / cm.

[0088] In various embodiments, the nonwoven fabric has a wet tensile strength of at least about 1.0 N / cm. In various embodiments, the nonwoven fabric has a wet tensile strength of at least about 2.0 N / cm. In various embodiments, the nonwoven fabric has a wet tensile strength of at least about 3.0 N / cm. In various embodiments, the nonwoven fabric has a wet tensile strength of at least about 4.0 N / cm. In various embodiments, the nonwoven fabric has a wet tensile strength of at least about 5.0 N / cm.

[0089] In various embodiments, the first absorbent layer(s) has a dry tensile strength of at least about 5.0 N / cm. In various embodiments, the first absorbent layer(s) has a dry tensile strength of at least about 9.0 N / cm. In various embodiments, the first absorbent layer(s) has a dry tensile strength of at least about 13.0 N / cm. In various embodiments, the first absorbent layer(s) has a dry tensile strength of at least about 17.0 N / cm. In various embodiments, the first absorbent layer(s) has a dry tensile strength of at least about 21.0 N / cm.

[0090] In various embodiments, the first absorbent layer(s) is needle punched. In various embodiments, the first absorbent layer(s) has a needle punch density of about 25 to about 150 per cm2. In various preferred embodiments the first absorbent layer(s) has a needle punch density of about 30 to about 80 per cm2.

[0091] In various embodiments, the first absorbent layer(s) has a needle punch depth of about 1mm to about 20mm. In various embodiments, the first absorbent layer(s) has a needle punch depth of about 5mm to about 20mm. In various embodiments, the first absorbent layer(s) has a needle punch depth of about 5mm to about 15mm. In various embodiments, the first absorbent layer(s) has a needle punch depth of about 5mm to about 10mm.

[0092] In various embodiments, the first absorbent layer(s) consists of the nonwoven fabric.

[0093] In various embodiments, the nonwoven fabric consists of the gelling fibres and the non-gelling fibres.

[0094] In a highly preferred embodiment, the first absorbent layer consists of the nonwoven fabric and the non-woven fabric consists of the gelling fibres and the non-gelling fibres; preferably wherein the gelling fibres are present in an amount of from about 60 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 40 wt% of the first absorbent layer.

[0095] In some embodiments the wound dressing does not comprise a stitch (i.e. the wound dressing is not stitchbonded). In some embodiments the first absorbent layer does not comprise a stitch, i.e. is not stitch bonded.

[0096] In some embodiments the negative pressure wound dressing comprises a stitch (i.e. the wound dressing is stitchbonded). In some embodiments the first absorbent layer comprises a stitch (i.e. the first absorbent layer is stitchbonded). In some embodiments the stitch is formed from nongelling fibres. In some embodiments the stitch is formed from modified cellulose (Lyocell) fibres.

[0097] In some embodiments the wound dressing does not comprise a scrim.

[0098] In some preferred embodiments the first absorbent layer has (i) a basis weight of about 150 - 200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, and (iii) a fluid retention of at least about 45%.

[0099] In some preferred embodiments the nonwoven fabric has (i) a basis weight of about 150 -200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, and (iii) a fluid retention of at least about 45%.

[0100] In some preferred embodiments the first absorbent layer has (i) a basis weight of about 150 - 200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, (iii) a fluid retention of at least about 45%, and (iv) a wet tensile strength of at least about 3.0 N / cm.

[0101] In some preferred embodiments the nonwoven fabric has (i) a basis weight of about 150 -200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, (iii) a fluid retention of at least about 45%, and (iv) a wet tensile strength of at least about 3.0 N / cm.

[0102] In some preferred embodiments the first absorbent layer comprises a nonwoven fabric, the nonwoven fabric comprising gelling fibres and non-gelling fibres, wherein the gelling fibres are present in an amount of from about 60 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 40 wt% of the first absorbent layer, wherein the first absorbent layer has (i) a basis weight of about 150 - 200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, (iii) a fluid retention of at least about 45%, and (iv) a wet tensile strength of at least about 3.0 N / cm.

[0103] In some preferred embodiments the nonwoven fabric comprises gelling fibres and non-gelling fibres that are present in the non-woven fabric at a weight ratio of from about 85:15 to about 65:35 and wherein the nonwoven fabric has (i) a basis weight of about 150 - 200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, (iii) a fluid retention of at least about 45%, and (iv) a wet tensile strength of at least about 3.0 N / cm.

[0104] In some embodiments, the nonwoven fabric is a homogenous fibre blend comprising gelling fibres and non-gelling fibres. In some embodiments, the nonwoven fabric is a homogenous fibre blend consisting of gelling fibres and non-gelling fibres.

[0105] In some preferred embodiments the adhesive skin contact layer provides an adhesive border. In some preferred embodiments the adhesive skin contact layer comprises a window. In some preferred embodiments the adhesive skin contact layer is configured to detachably adhere the dressing to a peri-wound dermal surface.

[0106] In some preferred embodiments each of the first absorbent layer, the transmission layer and the second absorbent layer (e.g. the superabsorbent layer) are laminated together. In some preferredembodiments each of the first absorbent layer, the transmission layer and the second absorbent layer (e.g. the superabsorbent layer) are laminated together by a scatter-coat adhesive, preferably wherein the scatter-coat adhesive is polylactic acid or polycaprolactone.

[0107] In some preferred embodiments the transmission layer is arranged between the first absorbent layer and the second absorbent layer.

[0108] In some preferred embodiments the second absorbent layer is a non-woven material. In some preferred embodiments the second absorbent layer comprises sodium polyacrylate.

[0109] In some preferred embodiments the transmission layer of the negative pressure wound dressing is a polyurethane foam, a polyester foam, a hydrophilic polyurethane, silicone, gelatine, polypropylene, nitrile or EVA foam. In some preferred embodiments the transmission layer of the negative pressure wound dressing is a polyurethane foam.

[0110] In some preferred embodiments the backing layer of the negative pressure wound dressing is a film material. In some preferred embodiments the backing layer of the negative pressure wound dressing is a polyurethane film material.

[0111] In some preferred embodiments the at least two of the first absorbent layer, the transmission layer and the second absorbent layer are laminated together by heat lamination.

[0112] In some preferred embodiments, the second absorbent layer is superabsorbent layer.

[0113] With reference to Figure 11, there is shown a negative pressure wound dressing 1. The negative pressure wound dressing 1 comprises an adhesive skin contact layer 20, a wound contact layer 4 (a first absorbent layer), a transmission layer 5, a superabsorbent layer 6 (a second absorbent layer), a backing layer 7 and an airway 8.

[0114] The adhesive skin contact layer 20 may have a perimetral shape with a central window 9, therefore, the adhesive skin contact layer 20 may be an adhesive skin contact border layer 20. The border layer 20 may comprise an outer periphery which defines the outer shape of the border layer 20, which, in this embodiment, is a square. The border layer 20 may comprise an inner periphery which defines the shape of the window 9. The window 9 may be of the same, or similar shape, to that of the outer periphery of the border layer 20.

[0115] The window 9 is a square through hole in the adhesive skin contact layer 20. The window 9 is located centrally relative to the periphery of the adhesive skin contact layer 20. Each side of thewindow 9 is arranged parallel to each of the corresponding sides of the adhesive skin contact layer 20. The window may have an area of 12,500mm2. The skilled person will appreciate that the window 9 may be enlarged by any suitable means, for example by cutting the adhesive skin contact layer 20. The window 9 in the adhesive skin contact layer 20 enables the wound of a patient to contact, or be in fluid communication with, other layers of the negative pressure wound dressing 1, for example the wound contact layer 4, when the negative pressure wound dressing 1 is applied to the skin of a patient.

[0116] The adhesive skin contact layer 20 comprises an upper surface 20b and a lower surface 20a. The lower surface 20a contacts the dermal surface in use. In use, the lower surface 20a of the adhesive skin contact layer 20 is detachably adhered to a dermal surface (not shown) of a patient such that the wound site (not shown) is located within the window 9. As such, the adhesive skin contact layer 20 is not in direct contact with the wound site but does wholly surround it. Thus, the adhesive skin contact layer 20 is in contact with intact peri-wound skin only. The upper surface 20b may be outwardly facing away from the patient's body.

[0117] A removable cover or "release layer" (not shown) may be adhered to the lower surface 20a of the adhesive skin contact layer 20. The removable cover, which may comprise folded grip sections, is removable from the lower surface 20a of the adhesive skin contact layer 20. Thus, the removable cover protects the adhesive skin contact layer 20 when the removable cover is adhered to the adhesive skin contact layer 20, but when the removable cover is removed from the lower surface 20a of the adhesive skin contact layer 20 for use of the negative pressure wound dressing 1, the lower surface 20a is exposed and able to releasably secure the negative pressure wound dressing 1 to the skin of a patient.

[0118] The wound contact layer 4, the transmission layer 5 and the superabsorbent layer 6 form an absorbent structure arranged between the adhesive skin contact layer 20 and the backing layer 7.

[0119] The backing layer 7 may comprise a first surface 7a and a second surface 7b. In use, the first surface 7a may be inwardly facing toward the patient's body, and the second surface 7b may be outwardly facing away from the patient's body.

[0120] The absorbent structure 4, 5, 6 may comprise a first surface 4a and a second surface 6b. The first surface 4a of the absorbent structure 4, 5, 6 may be adjacent, and in contact with, the upper surface 20b of the adhesive skin contact layer 20. The peripheral edge of the second surface 6b of the absorbent structure 4, 5, 6 may be adjacent, and in contact with, the first surface 7a of the backing layer 7.

[0121] The wound contact layer 4 may comprise a first surface 4a and a second surface 4b. In use, the first surface 4a may be inwardly facing toward the patient's body, and the second surface 4b may be outwardly facing away from the patient's body. The first surface 4a of the wound contact layer 4 may contact the wound when the negative pressure wound dressing 1 is adhered to the skin adjacent to the wound (i.e., when in use). The first surface 4a of the wound contact layer 4 is substantially aligned with the window 9 of the adhesive skin contact layer 20. As such, in use, the first surface 4a contacts the wound through the window 9. The second surface 4b of the wound contact layer 4 may be adjacent, and in contact with, a first surface 5a of the transmission layer 5 or a first surface 6a of the superabsorbent layer 6. In the described embodiment, the second surface 4b of the wound contact layer 4 is adjacent, and in contact with, the first surface 5a of the transmission layer 5.

[0122] The transmission layer 5 may comprise a first surface 5a and a second surface 5b. In use, the first surface 5a may be inwardly facing toward the patient's body, and the second surface 5b may be outwardly facing away from the patient's body. The first surface 5a of the transmission layer 5 may be adjacent, and in contact with, the second surface 4b of the wound contact layer 4 or a second surface 6b of the superabsorbent layer 6. The second surface 5b of the transmission layer 5 may be adjacent, and in contact with, a first surface 6a of the superabsorbent layer 6 or the first surface 7a of the backing layer 7. In the described embodiment, the first surface 5a of the transmission layer 5 is adjacent, and in contact with, the second surface 4b of the wound contact layer, and the second surface 5b of the transmission layer 5 is adjacent, and in contact with, the first surface 6a of the superabsorbent layer 6.

[0123] The superabsorbent layer 6 may comprise a first surface 6a and a second surface 6b. In use, the first surface 6a may be inwardly facing toward the patient's body, and the second surface 6b may be outwardly facing away from the patient's body. The first surface 6a of the superabsorbent layer 6 may be adjacent, and in contact with, the second surface 4b of the wound contact layer 4 or the second surface 5b of the transmission layer 5. The second surface 6b of the superabsorbent layer 6 may be adjacent, and in contact with, the first surface 5a of the transmission layer 5 or the first surface 7a of the backing layer 7. In the described embodiment, the first surface 6a of the superabsorbent layer 6 is adjacent, and in contact with, the second surface 5b of the transmission layer 5, and the second surface 6b of the superabsorbent layer 6 is adjacent, and in contact with, the first surface 7a of the backing layer 7.

[0124] The adhesive skin contact layer 20 may radially overlap the absorbent structure 4, 5, 6. The adhesive skin contact layer 20 may comprise an interior portion adjacent to and surrounding the window 9, and an exterior portion radially outwardly from the interior portion. The interior portionand the exterior portion of the first surface 20a of the adhesive skin contact layer 20 may contact and adhere to the skin of a patient in use. The interior portion of the second surface 20b of the adhesive skin contact layer 20 may be adjacent, and in contact with, a portion of the first surface 4a of the wound contact layer 4. The exterior portion of the second surface 20b of the adhesive skin contact layer 20 may be adjacent, and joined with, a peripheral portion of the first surface 7a of the backing layer 7. Beneficially, this helps to prevent wound exudate escaping from the confines of the negative pressure wound dressing which would be unhygienic and cause discomfort for the user. Moreover, this also helps maintain a negative pressure at the wound site.

[0125] The exterior portion of the second surface 20b of the adhesive skin contact layer 20 may be joined to the peripheral portion of the first surface 7a of the backing layer 7 by heat lamination, adhesive, welding or stitching.

[0126] The exterior portion of the second surface 20b of the adhesive skin contact layer 20 may extend radially beyond the periphery of the absorbent structure by about 27.5 mm.

[0127] At least two of the wound contact layer 4, the transmission layer 5 and the superabsorbent layer 6 may be laminated together. In the described embodiment, each of the wound contact layer 4, the transmission layer 5 and the superabsorbent layer 6 are laminated together. Advantageously, this means that the absorbent structure of the present invention is manufactured without requiring any relatively rigid dressing and binding components. Thus, the present invention provides an absorbent structure which is flexible, therefore benefits user comfort, and which is cheaper to manufacture than absorbent structures and, therefore negative pressure wound dressings, of the prior art. Moreover, lamination does not require any complex equipment or manufacturing techniques. Thus, the present invention is simple to manufacture.

[0128] Each of the wound contact layer 4, the transmission layer 5 and the superabsorbent layer 6 may be laminated together by a scatter-coat adhesive. The scatter-coat adhesive may be a hot melt, scatter-coat adhesive. In the described embodiment, the scatter-coat adhesive is polycaprolactone and has the following properties:- a melt flow index of between 5.2 g / 10min and 11.3 g / 10min, as tested with 2.16 kg, 1" PVC die at 160°C;- a maximum water content of 0.35%;- a mean molecular weight of 50,000;- a melting point of 60°C; and- a solubility parameter of 9.34 cal / cm3to 9.43 cal / cm3.

[0129] The scatter-coat adhesive may comprise particles of which at least 98% have a particle size of 0.6mm.

[0130] The wound contact layer 4, the transmission layer 5 and the superabsorbent layer 6 may be laminated together by a laminator having the following processing properties:- Heating zone temperature of 125°C;- Cooling zone temperature of 25°C;- Web tension (for each unwind reel) of 125 N;- Crush roller pressure of 1000 N; andWeb speed of 10 m / min.

[0131] The wound contact layer 4 further comprises a central region 4c and a peripheral region 4d. The central region 4c is substantially square and is bordered on each side by the peripheral region 4d.

[0132] The wound contact layer is described in detail above.

[0133] The transmission layer 5 is substantially square, as is the wound contact layer 4 and the superabsorbent layer 6, and has a thickness of 1.8mm and is made of a polyurethane foam. The transmission layer 5 may have a density of between 26 Kg / M3and 28 Kg / M3and a tensile strength of 150 kPa. The transmission layer 5 has an elongation at break value of 300% and a cell count of between 17 and 26 / cm. Moreover, the transmission layer 5 has a 40% CLD hardness of between 2.5 and 4.5 kPa.

[0134] The superabsorbent layer 6 comprises an upper layer having the second surface 6b, and a lower layer having the first surface 6a. Between the upper layer and the lower layer, there is enclosed a first material comprising non-woven fibres, an absorbent material and a hot melt binder.

[0135] The hot melt binder may be present in an amount of 70 g / m2. The hot melt binder may be a copolymer and, in the described embodiment, may be ethylene-vinyl acetate (EVA). In manufacture of the superabsorbent layer, the superabsorbent layer may be heated to melt the hot melt binder and bind the non-woven fibres of the first material together. Advantageously, this prevents, or at least significantly limits, the amount of shedding of the fibres of the superabsorbent layer when in use. Thus, the presence of the hot melt binder in the superabsorbent layer significantly increases the strength of the layer, preventing dissociation of the absorbent structure.

[0136] The absorbent material may be a superabsorbent material, capable of absorbing wound exudate while allowing the passage of fluid through it. The superabsorbent material may be sodiumpolyacrylate and in the form of a powder which, advantageously, increases the surface area to volume ratio of the superabsorbent material, therefore enhancing the absorbent property of the material.

[0137] The non-woven fibres may be cellulose fibres. The cellulose non-woven fibres may be arranged as a cellulosic non-woven matrix of fibres and may be a support onto which the absorbent material may be incorporated, for example, in the described embodiment, the absorbent material is dispersed upon the cellulosic non-woven matrix. The absorbent material may be dispersed evenly, or substantially evenly, throughout or upon the non-woven fibres, for example the cellulosic non-woven matrix.

[0138] The upper layer and the lower layer of the superabsorbent layer 6 may each be a cellulosic fabric layer. The upper fabric layer and the lower fabric layer may be joined around their entire periphery to enclose the first material.

[0139] The superabsorbent layer 6 may comprise a plurality of fenestrations (not shown). Each of the plurality of fenestrations may be openings in the form of slits in the superabsorbent layer 6. Each fenestration may have a length equal to 80% of the length of the superabsorbent layer 6. Each of the upper layer and the lower layer may comprise a plurality of fenestrations. The fenestrations may be arranged in a direction planar to a longitudinal axis and transverse to a longitudinal axis of the superabsorbent layer 6. Advantageously, this arrangement aids in managing a flow of exudate through the superabsorbent layer 6 of the negative pressure wound dressing 1. The fenestrations encourage or enable wound exudate to travel laterally on the superabsorbent layer 6, as opposed to axially, and assist in negative pressure transmission through the superabsorbent layer 6.

[0140] The superabsorbent layer 6 may have a basis weight of 460 g / m2, a thickness of 2.55 mm and a density of 0.255 g / cm3. Moreover, the superabsorbent layer 6 may have a tensile strength (dry) of 45 N / 50mm, an absorbent capacity of 25 g / g lOmin, and an absorbency under compression capacity of 0.85 g / cm2.

[0141] Each of the wound contact layer 4, transmission layer 5 and superabsorbent layer 6 may be substantially planar.

[0142] In use, the negative pressure wound dressing 1 forms part of a negative pressure wound exudate management system comprising the negative pressure wound dressing 1 and further comprising a source of negative pressure (not shown) and a coupling member (for example, airway 8) for providing negative pressure to the negative pressure wound dressing from an internal lumen of a conduit or tube (not shown) and through an opening (not shown) in the negative pressure wounddressing. The source of negative pressure comprises a pump for generating negative pressure and the tube connects the pump and negative pressure wound dressing 1 via the airway 8. In the present embodiment, the source of negative pressure may comprise a one-way valve (not shown) in-line between the pump and the negative pressure wound dressing 1 to maintain a negative pressure within the negative pressure wound dressing 1 when the pump is disconnected from the tube.

[0143] In use, the adhesive skin contact layer 20 is adhered to the intact peri-wound skin around a wound. The wound is located within the window 9 of the adhesive skin contact layer 20. The negative pressure wound dressing 1 is connected to a source of negative pressure before or after application of the dressing to the wound. Upon leaving the wound, wound exudate contacts the first surface 4a of the wound contact layer 4 and wicks upwardly, away from the wound site, toward the transmission layer 5. The high gelling ability of the wound contact layer 4 facilitates absorption and retention of the wound exudate. Lamination of the wound contact layer 4, transmission layer 5 and superabsorbent layer 6 means each of these layers form a consolidated, absorbent and retentive structure. The wound exudate wicks from the upper surface 4b of the wound contact layer 4 to the transmission layer 5. Lateral movement of the exudate occurs in the transmission layer 5 to spread the wound exudate across the surface area of the dressing. The exudate then wicks upwardly to the superabsorbent layer 6 where it is absorbed and retained prior to being transmitted out of the dressing 1 via vapour transmission through the backing film 7.

[0144] With reference to Figures 12 and 13, there is shown a further example embodiment of a negative pressure wound dressing 10.

[0145] The wound dressing 10 comprises an adhesive skin contact layer 200 (which is preferably the adhesive skin contact layer 20 described with reference to Figure 11), a wound contact layer 40 (a first absorbent layer), a transmission layer 50, a superabsorbent layer 60 (a second absorbent layer), a backing layer 70 and an airway 80. The wound contact layer 40, transmission layer 50 and superabsorbent layer 60 together form an absorbent structure 11 arranged between the adhesive skin contact layer 200 and the backing layer 70.

[0146] The adhesive skin contact layer 200 assists in securing the wound dressing 10 to the skin of a patient, in particular to the peri-wound skin adjacent to a wound. The adhesive skin contact layer 200 may have a weight of 200gsm which provides for a malleable, gelled structure so, in the event of an air leak, the layer can seal the leak more easily than if the layer had a weight below 100gsm, in particular below 40gsm. With reference to Figure 13, the adhesive skin contact layer 200 may be a perforated mesh comprising a plurality of perforations 30 arranged in a plurality of rows. In the1present embodiment, 95% of the perforations 30 are arranged in a triangle packed layout. The triangle packed layout comprises adjacent rows 30a, 30b of perforations 30. Row 30a is arranged offset from row 30b. The perforations 30 in row 30a are not arranged adjacent to the perforations 30 in the adjacent row 30b but instead the perforations 30 in row 30a are arranged adjacent to the gap between perforations 30 in row 30b or adjacent to part of the gap and part of a perforation 30 in row 30b.

[0147] Each perforation 30 comprises an opening, which in this embodiment is in the shape of a circle. In this embodiment, the size of each perforation 30 is defined by the diameter of the circle. However, the person skilled in the art will understand that the size of the opening may be defined depending on the shape of the opening. In some embodiments, the size of a circle is the diameter. In other embodiments, the size of an oval is the longer diameter. In further embodiments, the size of a hexagon is the longest diagonal; and the size of a triangle, a square, a rectangle, an octagon or any other polygon perforation may be the longest side. In the present embodiment, each perforation 30 has a diameter of 2.20mm and are therefore of sufficient size to provide breathability to the wound dressing in the event that some of the perforations reduce in diameter after their formation, for example by the adhesive entering the opening of a perforation. As such, the adhesive skin contact layer maintains an environment optimised for wound healing. Moreover, each perforation 30 is a through hole in the adhesive skin contact layer 200 which can enable fluid to flow through the layer 200. The adhesive skin contact layer 200, therefore, helps to prevent tissue ingrowth into the other material of the wound dressing.

[0148] The perforations 30 may have a pitch (i.e., the distance between the centre point of a perforation and the centre point of an adjacent perforation) in a first direction of 8.0mm, and a pitch in a second direction of 5.6mm, the first and second directions being perpendicular to one another. Advantageously, the pitch of the perforations 30 has a ratio of perforation: no-perforation which provides efficient moisture evaporation, prevents pooling and strongly adheres to the peri- wound skin of the patient. Surprisingly, and advantageously, tests have shown that the adhesive skin contact layer 200 remains adhered to a patient for at least seven days.

[0149] The total area of the perforations 30 may be 2100mm2and the total volume of the perforations may be 2100mm3. The degree of perforation may be 10.66% of the area of the adhesive skin contact layer 200. The perforations 30 are distributed evenly throughout the adhesive skin contact layer 200. The perforations 30 may be formed by a mechanical punch perforating process which does not result in the formation of a doughnut or volcano structure around the perforations after formation of the perforations 30. The perforations may be formed by mechanical punchperforating the adhesive skin contact layer 200 comprising a release liner (not shown) covering at least one surface of the adhesive skin contact layer 200.

[0150] The adhesive skin contact layer 200 may have a thickness of 1.0mm and a width and length (measured from the periphery of the adhesive skin contact layer 200) each of 130mm. The adhesive skin contact layer 200 has an outer periphery in the shape of a square. The adhesive skin contact layer 200 comprises an upper surface and a lower surface. The lower surface contacts the dermal surface in use.

[0151] The adhesive skin contact layer 200 may have a perimetral shape with a central window, therefore, the adhesive skin contact layer 200 may be an adhesive skin contact border layer 200. The border layer 200 may comprise an outer periphery which defines the outer shape of the border layer 200, which, in this embodiment, is a rectangle. The border layer 200 may comprise an inner periphery which defines the shape of the window. The window may be of the same, or similar shape, to that of the outer periphery of the border layer 200. In other embodiments, the window may have a different to that of the outer periphery of the border layer 200. For example, in embodiments comprising a border layer having an outer periphery which is square, the window may be, for example, a square or a rectangle. In embodiments, comprising a border layer having a square outer periphery and a window which is a rectangle, there may be greater overlap between the absorbent structure and the adhesive skin contact layer, therefore, allowing for a greater surface area for adhesion between the adhesive skin contact layer and the absorbent structure.

[0152] In this embodiment, the window has a perimeter which is a rectangle, therefore, the length of the transverse sides of the window is less than the length of the longitudinal sides of the window. The window is a rectangle through-hole in the adhesive skin contact layer 200. The shape of the window provides for greater overlap of the absorbent structure 11 and the adhesive skin contact layer 200, especially at the corresponding corner portion of the absorbent structure 11 and the adhesive skin contact layer 200. This is beneficial not least because it allows for a greater surface area for adhesion between the adhesive skin contact layer 200 and the absorbent structure 11, therefore, providing greater structural integrity to the wound dressing 10. The greater structural integrity means that the absorbent structure 11 maintains its position within the wound dressing 10 with reduced possibility of the absorbent structure 11 becoming dislodged from its position within the wound dressing 10 when in use, in particular when in use when the wound dressing 10 is wet with exudate or other fluids.

[0153] The window is located centrally relative to the periphery of the adhesive skin contact layer 200. Each side of the window is arranged parallel to each of the corresponding sides of the adhesive skin contact layer 200. Each longitudinal side of the window may have a length of about 210mm and each traverse side of the window may have a length of about 160mm. The window may have an area of about 33,600mm2. The skilled person will appreciate that the window may be enlarged by any suitable means, for example by cutting the adhesive skin contact layer 200. The window in the adhesive skin contact layer 200 enables the wound of a patient to contact, or be in fluid communication with, other layers of the wound dressing 10, for example the wound contact layer 40, when the wound dressing 10 is applied to the skin of a patient.

[0154] The adhesive skin contact layer 200 comprises an upper surface and a lower surface. The lower surface contacts the dermal surface in use. In use, the lower surface of the adhesive skin contact layer 200 is detachably adhered to a dermal surface (not shown) of a patient such that the wound site (not shown) is located within the window. As such, the adhesive skin contact layer 200 is not in direct contact with the wound site but does wholly surround it. Thus, the adhesive skin contact layer 200 is in contact with intact peri- wound skin only. The upper surface may be outwardly facing away from the patient's body.

[0155] A removable cover or "release layer" 21 may be adhered to the lower surface of the adhesive skin contact layer 200. The removable cover 21, which may comprise folded grip sections 21a, is removable from the lower surface of the adhesive skin contact layer 200. Thus, the removable cover protects the adhesive skin contact layer 200 when the removable cover 21 is adhered to the adhesive skin contact layer 200, but when the removable cover 21 is removed from the lower surface of the adhesive skin contact layer 200 for use of the wound dressing 10, the lower surface is exposed and able to releasably secure the wound dressing 10 to the skin of a patient.

[0156] The airway 80 may comprise a connector 82 at its distal end. The connector 82 may connect the airway 80 to an internal lumen of a conduit or tube (not shown) which in turn is connected to a source of negative pressure. The source of negative pressure may comprise a pump (not shown) for generating negative pressure and the conduit or tube may connect the pump and wound dressing 10 via the airway 80. The pump may provide negative pressure to the wound dressing 10 via the internal lumen of the conduit or tube, along the airway 80, and through an opening 12 in the wound dressing 10. In the present embodiment, the source of negative pressure may comprise a one-way valve (not shown) in-line between the pump and the wound dressing 10 to maintain a negative pressure within the wound dressing 10 when the pump is disconnected from the tube.

[0157] The airway may further comprise an adhesive layer 81 at its proximal end for adhering the proximal end of the airway 80 to a second surface 7b0 (outer facing surface) of the backing layer 70. The adhesive layer 81 may comprise an opening 12a for allowing a flow of air from the wound dressing 10 into the airway 80.

[0158] The opening 12 may comprise an opening in each of the backing layer 70 and absorbent structure 11. The backing layer 70 may comprise an opening 12b, and the absorbent structure 11 may comprise an opening 12c. Openings 12b and 12c may be arranged off-centre relative to the periphery of the backing layer 70 and the absorbent structure 11, respectively. Opening 12c may comprise corresponding openings in each of the superabsorbent layer 60, transmission layer 50 and wound contact layer 40. Opening 12c may be in fluid communication with the window 90 and, therefore, the wound site. The openings 12a, 12b and 12c may provide a fluid pathway between the wound site and the airway 80. Thus, in use, the openings 12a, 12b and 12c allow for the flow of air from the wound site, through the absorbent structure 11, through the backing layer 70, along the airway 80 and along a tube or conduit (not shown) toward a source of negative pressure (not shown). The backing layer 70 may comprise a first surface 7a0 and the second surface 7b0. In use, the first surface 7a0 may be inwardly facing toward the patient' s body, and the second surface 7b0 may be arranged opposite the first surface 7a0, outwardly facing away from the patient's body.

[0159] The absorbent structure 11 may comprise a first surface and a second surface. In use, the first surface of the absorbent structure 11 may predominantly comprise a wound facing surface of the wound contact layer 40. In use, the second surface of the absorbent structure 11 may predominantly comprise an outwardly facing surface of the superabsorbent layer 60. The first surface of the absorbent structure 11 may be adjacent, and in contact with, the upper surface of the adhesive skin contact layer 200. In particular, the peripheral portion of the first surface of the absorbent structure 11 may be in contact with the upper surface of the adhesive skin contact layer 200. The peripheral edge of the second surface of the absorbent structure 11 may be adjacent, and in contact with, the first surface 7a0 of the backing layer 70.

[0160] The wound contact layer 40 may comprise a first surface arranged opposite a second surface. In use, the first surface may be inwardly facing toward a patient' s body, and the second surface may be outwardly facing, away from the patient's body. The first surface of the wound contact layer 40 may contact the wound when the wound dressing 10 is adhered to the skin adjacent to the wound (i.e., when in use). The first surface of the wound contact layer 40 may be substantially aligned with the window of the adhesive skin contact layer 200. As such, in use, the first surface contacts the wound through the window. The second surface of the wound contact layer 40 may be adjacent, and incontact with, a first surface of the transmission layer 50 or a first surface of the superabsorbent layer 60. In the described embodiment, the second surface of the wound contact layer 40 is adjacent, and in contact with, the first surface of the transmission layer 50.

[0161] The transmission layer 50 may comprise a first surface arranged opposite a second surface. In use, the first surface may be inwardly facing toward a patient' s body, and the second surface may be outwardly facing away from the patient's body. The first surface of the transmission layer 50 may be adjacent, and in contact with, the second surface of the wound contact layer 40 or a second surface of the superabsorbent layer 60. The second surface of the transmission layer 50 may be adjacent, and in contact with, a first surface of the superabsorbent layer 60 or the first surface 7a of the backing layer 70. In the described embodiment, the first surface of the transmission layer 50 is adjacent, and in contact with, the second surface of the wound contact layer 40, and the second surface of the transmission layer 50 is adjacent, and in contact with, the first surface of the superabsorbent layer 60.

[0162] The superabsorbent layer 60 may comprise a first surface arranged opposite a second surface. In use, the first surface may be inwardly facing toward a patient' s body, and the second surface may be outwardly facing away from the patient's body. The first surface of the superabsorbent layer 60 may be adjacent, and in contact with, the second surface of the wound contact layer 40 or the second surface of the transmission layer 50. The second surface of the superabsorbent layer 60 may be adjacent, and in contact with, the first surface of the transmission layer 50 or the first surface 7a of the backing layer 70. In the described embodiment, the first surface of the superabsorbent layer 60 is adjacent, and in contact with, the second surface of the transmission layer 50, and the second surface of the superabsorbent layer 60 is adjacent, and in contact with, the first surface 7a of the backing layer 70.

[0163] The adhesive skin contact layer 200 may radially overlap the absorbent structure 11. The adhesive skin contact layer 200 may comprise an interior portion adjacent to and surrounding the window, and an exterior portion radially outwardly from the interior portion. The interior portion and the exterior portion of the first surface of the adhesive skin contact layer 200 may contact and adhere to the skin of a patient in use. The interior portion of the second surface of the adhesive skin contact layer 200 may be adjacent, and in contact with, a portion of the first surface of the wound contact layer 40. The exterior portion of the second surface of the adhesive skin contact layer 200 may be adjacent, and joined with, a peripheral portion of the first surface 7a0 of the backing layer 70. Beneficially, this helps to prevent wound exudate escaping from the confines of the wound dressing which would be unhygienic and cause discomfort for the user. Moreover, this also helps maintain a negative pressure at the wound site. The exterior portion of the second surface of the adhesive skincontact layer 200 may be joined to the peripheral portion of the first surface 7a0 of the backing layer 70 by heat lamination, adhesive, welding or stitching.

[0164] The exterior portion of the second surface of the adhesive skin contact layer 200 may extend radially beyond the periphery of the absorbent structure e.g. by about 27.5 mm.

[0165] At least two of the wound contact layer 40, the transmission layer 50 and the superabsorbent layer 60 may be laminated together. In the described embodiment, each of the wound contact layer 40, the transmission layer 50 and the superabsorbent layer 60 are laminated together, therefore forming a consolidated absorbent structure 11. Advantageously, this means that the absorbent structure 11 of the present invention is manufactured without requiring any relatively rigid dressing and binding components. Thus, the present invention provides an absorbent structure 11 which is flexible, therefore benefits user comfort, and which is cheaper to manufacture than absorbent structures and, therefore negative pressure wound dressings, of the prior art. Moreover, beneficially lamination does not require any complex equipment or manufacturing techniques. Thus, the present invention is simple to manufacture.

[0166] Each of the wound contact layer 40, the transmission layer 50 and the superabsorbent layer 60 may be laminated together by a scatter-coat adhesive. The scatter-coat adhesive may be a hot melt, scatter-coat adhesive.

[0167] In some embodiments a kit can be provided comprising a backing layer and an absorbent structure for a negative pressure wound dressing according to the present invention.

[0168] In some embodiments a negative pressure wound exudate management system can be provided comprising the negative pressure wound dressing according to the present invention, a source of negative pressure, and a coupling member for providing negative pressure to the negative pressure wound dressing.

[0169] In some preferred embodiments a process for manufacturing a negative pressure wound dressing comprises the following steps:(a) Providing an adhesive skin contact layer and a backing layer;(b) Providing a wound contact layer, a transmission layer and a superabsorbent layer;(c) Adhering together at least two of the wound contact layer, the transmission layer and the superabsorbent layer to form an absorbent structure; and(d) Arranging the absorbent structure between the adhesive skin contact layer and the backing layerwherein, in step c, each of the wound contact layer, the transmission layer and the superabsorbent layer are adhered together by lamination or by stitchbonding.

[0170] This process can be combined with the following processes and methods for preparing first absorbent layers of the present invention.PROCESS

[0171] A process for preparing a negative pressure wound dressing comprising a first absorbent layer, as disclosed herein, wherein the first absorbent layer comprises a nonwoven fabric, the nonwoven fabric comprising gelling fibres and non-gelling fibres, wherein the gelling fibres are present in an amount of from about 60 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 40 wt% of the first absorbent layer;the process comprising the following steps:(a) opening and carding the gelling fibres and non-gelling fibres to provide a fibre web; (b) cross lapping and drafting the fibre web to provide a cross lapped fibre web;(c) needle punching the cross lapped fibre web.

[0172] In various embodiments, the gelling fibres are present in an amount of from about 65 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 35 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 70 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 30 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 75 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 25 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 80 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 20 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 85 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 15 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 90 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 10 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 65 to about 90 wt% of the first absorbent layer and the nongelling fibres are present in an amount of from about 10 to about 35 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 70 to about 90 wt%of the first absorbent layer and the non-gelling fibres are present in an amount of from about 10 to about 30 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 75 to about 90 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 10 to about 25 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 80 to about 90 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 10 to about 20 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 85 to about 90 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 10 to about 15 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 65 to about 85 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 15 to about 35 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 70 to about 85 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 15 to about 30 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 75 to about 85 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 15 to about 25 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 80 to about 85 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 15 to about 20 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 90 to about 85 wt% of the first absorbent layer and the nongelling fibres are present in an amount of from about 15 to about 10 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 65 to about 80 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 20 to about 35 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 70 to about 80 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 20 to about 30 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 75 to about 80 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 20 to about 25 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 85 to about 80 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 20 to about 15 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 90 to about 80 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 20 to about 10 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of fromabout 65 to about 75 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 25 to about 35 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 70 to about 75 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 25 to about 30 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 80 to about 75 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 25 to about 20 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 85 to about 75 wt% of the first absorbent layer and the nongelling fibres are present in an amount of from about 25 to about 15 wt% of the first absorbent layer. In various embodiments, the gelling fibres are present in an amount of from about 90 to about 75 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 25 to about 10 wt% of the first absorbent layer.

[0173] In various embodiments, the first absorbent layer(s) is needle punched. In various embodiments, the first absorbent layer(s) has a needle punch density of about 25 to about 150 per cm2. In various preferred embodiments, the first absorbent layer(s) has a needle punch density of about 30 to about 80 per cm2.

[0174] In various embodiments, the first absorbent layer(s) has a needle punch depth of about 1mm to about 20mm. In various embodiments, the first absorbent layer(s) has a needle punch depth of about 5mm to about 20mm. In various embodiments, the first absorbent layer(s) has a needle punch depth of about 5mm to about 15mm. In various embodiments, the first absorbent layer(s) has a needle punch depth of about 5mm to about 10mm.

[0175] In various embodiments, the drafting set value (V) of the feeding and discharging of the web is at least about 30%; preferably wherein the drafting set value ratio (V) of the feeding and discharging of the web is at least about 40%.

[0176] The gelling forming fibres are typically chemically modified cellulosic fibres in the form of a fabric and in particular carboxymethylated cellulose fibres, as described in PCT WO00 / 01425. Sodium carboxymethylcellulose fibres typically have a degree of substitution of at least 0.05 carboxymethyl groups per glucose unit. The gel forming fibres typically have an absorbency of at least 2 grams (or at least 8 grams, or at least 10 grams), 0.9% saline solution (Solution A) per gram of fibre (as measured by BS EN 13726-1 (2002) " Test methods for primary wound dressings", section 3.2 " Free swell absorptive capacity"). The carboxymethylated cellulosic fabrics typically have a degree of substitution between 0.12 to 0.35 (as defined in WO00 / 01425), more typically a degree of substitution of between0.20 and 0.30, such that the absorbency of a fabric produced from is increased when compared to the unmodified cellulose. Particular useful fabrics have an absorbency of from about 10 g / g to about 30 g / g of isotonic aqueous solution as measured by the method described in BS EN 13726-1 (2002).

[0177] In various embodiments, the gelling fibres are selected from: carboxymethylcellulose fibres and derivatives thereof, modified cellulosic fibres, alkyl sulphonate modified cellulosic fibres, pectin fibres, alginate fibres, chitosan fibres, hyaluronic acid fibres, fibres derived from gums, non-cellulose synthetic fibres, superabsorbent fibres, such as polyacrylate fibres, and combinations thereof.

[0178] In a preferred embodiment, the gelling fibres are carboxymethylcellulose fibres or derivatives thereof (e.g. HYDROCEL™).

[0179] In various embodiments, the non-gelling fibres are selected from synthetic fibres, semisynthetic fibres, non-synthetic fibres or combinations thereof.

[0180] In various embodiments, the non-gelling fibres are selected from: cellulosic fibres, modified cellulosic fibres (such as viscose / rayon), polyester fibres, polypropylene fibres, polyamide fibres, or combinations thereof.

[0181] In a preferred embodiment, the non-gelling fibres are cellulosic fibres, modified cellulosic fibres, or a combination thereof. Highly preferred non-gelling fibres are lyocell fibres (e.g. LYOCELL™).

[0182] In various embodiments, the gelling fibres and non-gelling fibres are present in the non-woven fabric at a weight ratio of from about 85:15 to about 65:35. In a various embodiments, the gelling fibres and non-gelling fibres are present in the non-woven fabric at a weight ratio of about 80:20 to about 70:30. In a preferred embodiment the gelling fibres and non-gelling fibres are present in the non-woven fabric at a weight ratio of about 75:25.

[0183] In various embodiments, the first absorbent layer(s) has a basis weight of about 150 - 200 gsm. In various embodiments, the first absorbent layer(s) has a basis weight of about 160 - 185 gsm.

[0184] In various embodiments, the nonwoven fabric has a basis weight of about 150 - 200 gsm. In various embodiments, the nonwoven fabric has a basis weight of about 160 - 185 gsm.

[0185] In various embodiments, the first absorbent layer disclosed herein may have a thickness between about 0.5mm to about 20mm. In various embodiments, the first absorbent layer disclosed herein may have a thickness between about 1mm to about 10mm. In various embodiments, the first absorbent layer disclosed herein may have a thickness between about 1.53mm to about 7 mm.

[0186] In various embodiments, the first absorbent layer(s) has a bulk density of about 25 - 100 kg / m3. In various embodiments, the first absorbent layer(s) has a bulk density of about 35 - 90 kg / m3. In various embodiments, the first absorbent layer(s) has a bulk density of about 40 - 80 kg / m3.

[0187] In various embodiments, the nonwoven fabric has a bulk density of about 25 - 100 kg / m3. In various embodiments, the nonwoven fabric has a bulk density of about 35 - 90 kg / m3. In various embodiments, the nonwoven fabric has a bulk density of about 40 - 80 kg / m3.

[0188] In various embodiments, the first absorbent layer has a fluid absorbency of about 0.05g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.10g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.15g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.20g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.25g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.30g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.35g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.40g / cm2or more. In various embodiments, the first absorbent layer has a fluid absorbency of about 0.45g / cm2or more.

[0189] In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.05g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.10g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.15g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.20g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.25g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.30g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.35g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.40g / cm2or more. In various embodiments, the nonwoven fabric has a fluid absorbency of about 0.45g / cm2or more.

[0190] In various embodiments, the first absorbent layer has a fluid retention of at least about 45%. In various embodiments, the first absorbent layer has a fluid retention of at least about 55%. In various embodiments, the first absorbent layer has a fluid retention of at least about 65%. In various embodiments, the first absorbent layer has a fluid retention of at least about 75%. In various embodiments, the first absorbent layer has a fluid retention of at least about 85%. In variousembodiments, the first absorbent layer has a fluid retention of at least about 90%. In various embodiments, the first absorbent layer has a fluid retention of at least about 95%.

[0191] In various embodiments, the nonwoven fabric has a fluid retention of at least about 45%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 55%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 65%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 75%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 85%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 90%. In various embodiments, the nonwoven fabric has a fluid retention of at least about 95%.

[0192] In various embodiments, the first absorbent layer has a lateral wicking distance of no more than about 40 mm in the machine direction and in the transverse direction. In various embodiments, the first absorbent layer has a lateral wicking distance of no more than about 30 mm in the machine direction and in the transverse direction. In various embodiments, the first absorbent layer has a lateral wicking distance of no more than about 25 mm in the machine direction and in the transverse direction. In various embodiments, the first absorbent layer has a lateral wicking distance of no more than about 20 mm in the machine direction and in the transverse direction.

[0193] In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.10 g / cm2. In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.12 g / cm2. In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.14 g / cm2. In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.16 g / cm2. In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.18 g / cm2. In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.20 g / cm2. In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.22 g / cm2. In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.24 g / cm2. In various embodiments, the first absorbent layer has an absorption under compression of at least about 0.26 g / cm2.

[0194] In various embodiments, the first absorbent layer(s) has a dimensional shrinkage of no greater than about 25 % in the machine direction and in the transverse direction. In various embodiments, the first absorbent layer(s) has a dimensional shrinkage of no greater than about 20 % in the machine direction and in the transverse direction. In various embodiments, the first absorbent layer(s) has a dimensional shrinkage of no greater than about 15 % in the machine direction and in the transversedirection. In various embodiments, the first absorbent layer(s) has a dimensional shrinkage of no greater than about 10 % in the machine direction and in the transverse direction.

[0195] In various embodiments, the first absorbent layer(s) has a wet tensile strength of at least about 1.0 N / cm. In various embodiments, the first absorbent layer(s) has a wet tensile strength of at least about 2.0 N / cm. In various embodiments, the first absorbent layer(s) has a wet tensile strength of at least about 3.0 N / cm. In various embodiments, the first absorbent layer(s) has a wet tensile strength of at least about 4.0 N / cm. In various embodiments, the first absorbent layer(s) has a wet tensile strength of at least about 5.0 N / cm.

[0196] In various embodiments, the nonwoven fabric has a wet tensile strength of at least about 1.0 N / cm. In various embodiments, the nonwoven fabric has a wet tensile strength of at least about 2.0 N / cm. In various embodiments, the nonwoven fabric has a wet tensile strength of at least about 3.0 N / cm. In various embodiments, the nonwoven fabric has a wet tensile strength of at least about 4.0 N / cm. In various embodiments, the nonwoven fabric has a wet tensile strength of at least about 5.0 N / cm.

[0197] In various embodiments, the first absorbent layer(s) has a dry tensile strength of at least about 5.0 N / cm. In various embodiments, the first absorbent layer(s) has a dry tensile strength of at least about 9.0 N / cm. In various embodiments, the first absorbent layer(s) has a dry tensile strength of at least about 13.0 N / cm. In various embodiments, the first absorbent layer(s) has a dry tensile strength of at least about 17.0 N / cm. In various embodiments, the first absorbent layer(s) has a dry tensile strength of at least about 21.0 N / cm.

[0198] In some embodiments the first absorbent layer does not comprise a stitch (i.e. the first absorbent layer is not stitchbonded).

[0199] In some embodiments the negative pressure wound dressing comprises a stitch (i.e. the wound dressing is stitchbonded). In some embodiments the first absorbent layer comprises a stitch (i.e. the first absorbent layer is stitchbonded). In some embodiments the stitch is formed from nongelling fibres. In some embodiments the stitch is formed from modified cellulose (Lyocell) fibres.

[0200] In some embodiments the negative pressure wound dressing does not comprise a scrim.

[0201] In some preferred embodiments the first absorbent layer has (i) a basis weight of about 150 - 200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, and (iii) a fluid retention of at least about 45%.

[0202] In some preferred embodiments the nonwoven fabric has (i) a basis weight of about 150 -200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, and (iii) a fluid retention of at least about 45%.

[0203] In some preferred embodiments the first absorbent layer has (i) a basis weight of about 150 - 200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, (iii) a fluid retention of at least about 45%, and (iv) a wet tensile strength of at least about 3.0 N / cm.

[0204] In some preferred embodiments the nonwoven fabric has (i) a basis weight of about 150 -200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, (iii) a fluid retention of at least about 45%, and (iv) a wet tensile strength of at least about 3.0 N / cm.

[0205] In some preferred embodiments the first absorbent layer comprises a nonwoven fabric, the nonwoven fabric comprising gelling fibres and non-gelling fibres, wherein the gelling fibres are present in an amount of from about 60 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 40 wt% of the first absorbent layer, wherein the first absorbent layer has (i) a basis weight of about 150 - 200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, (iii) a fluid retention of at least about 45%, and (iv) a wet tensile strength of at least about 3.0 N / cm.

[0206] In some preferred embodiments the nonwoven fabric comprises gelling fibres and non-gelling fibres that are present in the non-woven fabric at a weight ratio of from about 85:15 to about 65:35 and wherein the nonwoven fabric has (i) a basis weight of about 150 - 200 gsm, (ii) a fluid absorbency of about 0.15g / cm2or more, (iii) a fluid retention of at least about 45%, and (iv) a wet tensile strength of at least about 3.0 N / cm.

[0207] In various embodiments, the negative pressure wound dressing consists of one or more first absorbent layers. In various embodiments, the negative pressure wound dressing consists of a plurality of first absorbent layers. In various embodiments, the negative pressure wound dressing consists of the first absorbent layer.

[0208] In various embodiments, wherein process step (a) is configured to blend the gelling fibres and non-gelling fibres.

[0209] In various embodiments, the process comprises process step (d) wherein the first absorbent layer is adhered or affixed to one or more functional layers selected from: an outer cover layer, a transmission layer, an adhesive layer, a support layer, a distribution layer, a soluble medicated filmlayer, an odour-absorbing layer, a spreading layer, a keying layer, a superabsorbent layer or combinations thereof. In a preferred embodiment, the one or more further functional layers is selected from: a wound contacting layer, a transmission layer, an adhesive layer, a superabsorbent layer or combinations thereof.

[0210] In various embodiments, the first absorbent layer(s) consists of the nonwoven fabric.

[0211] In various embodiments, the non-woven fabric consists of the gelling fibres and the nongelling fibres.

[0212] In a preferred embodiment, the negative pressure wound dressing consists of the first absorbent layer, where the first absorbent layer consists of the nonwoven fabric.

[0213] In a highly preferred embodiment, the negative pressure wound dressing consists of the first absorbent layer, where the first absorbent layer consists of the non-woven fabric and the non-woven fabric consists of the gelling fibres and the non-gelling fibres; preferably wherein the gelling fibres are present in an amount of from about 60 to about 95 wt% of the first absorbent layer and the nongelling fibres are present in an amount of from about 5 to about 40 wt% of the first absorbent layer.

[0214] In some embodiments, the nonwoven fabric is a homogenous fibre blend comprising gelling fibres and non-gelling fibres. In some embodiments, the nonwoven fabric is a homogenous fibre blend consisting of gelling fibres and non-gelling fibres.

[0215] In various embodiments, the first absorbent layer(s) is a wound contact layer.

[0216] In various embodiments, the process comprises process step (e) wherein one or more substances are at least partially impregnated or coated on at least one surface of the absorbent layer(s) (preferably the first absorbent layer). In various embodiments, the one or more substances are at least partially impregnated or coated on at least one surface of the absorbent layer(s) (preferably the first absorbent layer) by printing, such as screen printing, gravure printing, rotary pad printing and needle dosing.

[0217] In various embodiments, the one or more substances are selected from those disclosed above.

[0218] In various embodiments, the one or more substances is selected from: a medicament, an adhesive, a deodorant, a chelating agent, a surfactant, an amphoteric surfactant, an anionic surfactant, a cationic surfactant, a thickening agent, an electrically conductive formulation, a thermoresponsive agent, an exothermic agent, an endothermic agent, or a combination thereof;preferably wherein the medicament comprises one or more agents selected from the group consisting of: antimicrobials, analgesics, coagulants, anti-inflammatories or a combination thereof.

[0219] In various embodiments, the one or more substances comprises a wound cleansing or debridement composition; preferably wherein the composition comprises:i. a chelating agent;ii. an amphoteric surfactant;iii. an anionic surfactant; andiv. a thickening agent, wherein the thickening agent comprises at least one poly(meth)acrylic acid and / or salt thereof.

[0220] In various embodiments, the one or more substances comprises a non-antimicrobial composition, said composition comprising (i) glycerol, triglycerol or a combination thereof, and (ii) one or more C1.4 alcohol, wherein the weight ratio of (i) to (ii) in the composition is from about 2:1 to about 5:1.

[0221] In various embodiments, the one or more substance is applied in the form of a solid, a gel, a wax, a liquid, a suspension, or an emulsion; preferably wherein the substance is applied in the form of a liquid.APPLICATION METHODS

[0222] In various embodiments, a substance or composition described herein is comprised in a negative pressure wound dressing as defined herein, wherein said negative pressure wound dressing comprises a first absorbent layer at least partially impregnated or coated with said substance or composition. Various methods by which the substance or composition is at least partially impregnated or coated in or on the first absorbent layer are known in the art and the present disclosure is not limited in this respect.

[0223] Inclusion of the disclosed technology in a negative pressure wound dressing can be achieved by addition to the material from which the dressing or device is constructed or by addition to the finished dressing / device. For example, where the first absorbent layer comprises fibres, the substance or composition may be added to the dope (the liquid from which the fibres are spun (extruded)). In other embodiments, the substance or composition may be co-extruded in a hot melt process. The substance or composition may be washed into the fibre by a soaking process. The substance or composition may be coated onto the formed fibre by passing through a bath containing the technology in a liquid or solution form (where the solute may be removed by a drying process knownin the art, such as by forced air or any other gas, particularly nitrogen if flammable solvents are involved, or by heat, or by heat and forced air) or as a molten liquid. The substance or composition may be sprayed onto the formed fibre in a liquid form or from a solution (where the solute may be removed by a drying process known in the art such as by forced air or any other gas, particularly nitrogen if flammable solvents are involved, or by heat, or by heat and forced air) or as a molten liquid in a hot-melt inkjet process. The substance or composition may be added as a powder coating where adhesion could be encouraged by electrostatic effects or by increasing the adhesive tack properties of the receiving fibre (say by partial hydration using humidity or by pre-treating the fibre with a viscous liquid such as an alcohol (for example hexanol), a polyol (for example propan-1, 2-diol or glycerol), a hydrophilic hydrocarbon (for example a polyethylene oxide) or by the order of addition of the substance or composition itself (for example a liquid surfactant such as liquid fatty acid or fatty acid salt or a liquid fatty acid that will form the salt in situ).

[0224] When the absorbent structure is pre-formed the technology may be added via similar washing, coating, spraying or powder coating. Additionally, the substance or composition may be added by suspending the substance or composition in a non-solvent and passing this through the such that the suspended technology is mechanically trapped (i.e. positively added by filtration).

[0225] In further embodiments, the substance or composition may be added as an ink or pigment by a printing process, for example a screen-printing process, where the addition can be closely controlled by use of the screen. The print could be a continuous, for example as achieved by flood-coating, or, more preferably as a discontinuous coating (regular or random patterned) as it has less impact on porosity / breathability, flexibility and ability to contour to the complex topography of the wound bed and both the macroscopic (physiology) and microscopic (cellular) levels.

[0226] The substance or composition may be added as a separate layer, for example as a gel coating directly onto the first absorbent layer, for example by way of a knife- over-roll or gravure coating technique. In further embodiments, the substance or composition may be cast as a film by a similar coating technique and then adhered to the wound device by tackifying the device or the film by, for example humidification, or by the addition of an adhesive.

[0227] It is generally known that printing on fabrics or other sheet-based materials may be carried out in a substantially direct or indirect manner, by discharge or by resist independently of the type of process used. The direct printing method consists of applying a formulation directly onto the material and subsequently fixing said formulation onto the fibres of the material. Particularly, direct printing may be carried out by using conventional roller printing or flat screen-printing procedures.

[0228] Generally, with reference to roller printing methods (e.g. flexographic, serigraphic and intaglio techniques), the method utilises equipment generally consists of a plurality of cylinders and / or rollers on which a number of engraved rollers may apply a particular formulation to an interceding material, such as a fabric material or other sheet-based materials.

[0229] In the case of the roller printing methods, such as a Gravure printing process or a Rotary Pad printing process, there are typically at least two rollers, one used for transporting a formulation (i.e. a printing roller) and the other acts as an impression member. Passing between the rollers is the substrate material to be printed on. The formulation is typically provided to the printing roller by passing through an underlying tray, where the printing roller takes up the formulation from the underlying tray, while a doctor blade eliminates any excess ink. This printing typology allows the application of substances on a material in a rapid and economical manner.

[0230] The aforementioned techniques are often used for applying substances onto fabrics, such as woven or nonwoven fabrics, and sheet-based materials, such as foams or plastic sheet materials. As discussed above, the substance or compositions of the present disclosure are particularly suited for the above discussed processes, and in particular processes for producing discontinuous coatings such as regular or random patterns such as dot arrays. For example, the substance or compositions of the present disclosure are particularly suitable for screen-printing.

[0231] Further, the substance or compositions of the present disclosure are also specifically adapted for novel printing processes, such as the process referred to herein as "hybrid printing". In said hybrid printing process,

[0232] It is known in the art to use solvent flooding to manufacture first absorbent layers for wound dressings because it is efficacious in the delivery of excipients to the dressing. This process may involve saturating the first absorbent layer with an excipient-containing solution, and removing excess solution. With gel-forming fibres in the first absorbent layer, the water content of the excipientcontaining solution may be minimised in order to avoid premature gelling of the fibres or reduction in absorbency of the first absorbent layer. Consequently the solvent used in the flooding process is primarily organic, e.g. an alcohol, and this can limit its application for large-scale manufacture both because of cost implications for infrastructure design and process controls, and safety implications surrounding the use of high volumes of volatile solvents. It would be desirable to manufacture first absorbent layers on a large scale with improved considerations for safety, feasibility and efficacy. Printing processes, such as Gravure, rotary pad and screen printing techniques, are attractive for thispurpose because a reduced volume of solvent can be used to apply the excipients via a predesigned mesh or transfer cylinder.

[0233] The process of screen printing involves pressing an ink or pigment through a stencilled mesh using a rubber blade or squeegee. The mesh is stretched over a frame and remains under tension in order to act as the 'screen'. A design or pattern may be created by making areas of the mesh impermeable to the ink. This may be carried out using an emulsion as is known in the art. During use, the blade or squeegee is moved across the screen to fill the open mesh apertures with ink (excipients fully dissolved in a liquid) or pigment (particles suspended in a liquid carrier), and a reverse stroke causes the screen to touch the substrate momentarily along a line of contact. This causes the ink or pigment to wet the substrate and be pulled out of the mesh aperture as the screen springs back after the blade or squeegee has passed. However, application of substances using screen printing relies heavily upon both the process and the starting materials. In particular, the substances should be formulated into a liquid with specific viscosity and surface tension characteristics to allow reproducible printing. Thus, it is not always possible to use this technique, depending on the substance to be applied.

[0234] Rotary printing techniques, such as Gravure or rotary pad printing techniques, are widely used for applying substances to medical devices. However, there are often problems associated with using these techniques when it is desirable to apply specific quantities of one or more substances to a substrate material. There are also associated problems with the aforementioned printing techniques in that the application of the substances may lack uniformity in the surface application of the substance. This is particularly prevalent when the substrate materials have uneven surfaces, such as is the case for nonwoven fabrics, for example. Furthermore, similar problems faced by screen printing were also associated with rotary-type printing techniques, where the viscosity of a formulation can have detrimental impacts on the final print finish. In particular, during the transfer of substances from a Gravure cylinder to a substrate surface, either directly or indirectly via an interim cylinder, some substance is often retained in the recessed cells, likely due to characteristics associated with the substance itself, such as the surface tension of the substance, and / or the surface energy of the cells. Similar problems are observed in other techniques used in the medical device industry, such as Flat Screen printing, Rotary Screen printing and Needle Dosing. This problem is particularly acute where the pattern to be printed is particularly fine, such as less than 0.75mm2.

[0235] Accordingly, the present invention provides a solution, where a method of applying one or more substance(s) to one or more first absorbent layers of an article is provided, wherein the method comprises:(a) providing at least one transfer means comprising an impression member and a transfer member, wherein the transfer member comprises one or more cells with outward facing apertures, and wherein the transfer member is provided on the exterior of the impression member;(b) introducing the one or more substance(s) into the one or more cells of the transfer member; and(c) contacting the first absorbent layer with the transfer member as the first absorbent layer is conveyed along a transport path in a machine direction, wherein force applied by the impression member to at least the one or more cells comprised within the transfer member causes the one or more substance(s) comprised within the one or more cells to transfer to the first absorbent layer.TRANSFER MEANS

[0236] According to the present invention, the transfer means comprises of an impression member and a transfer member.

[0237] As described herein, impression members are configured to apply a force to an opposing member or substrate, whereas the transfer member comprises one or more cells with outward facing apertures that are capable of being loaded with one or more substances, which can be transferred to a substrate material. The configuration of a transfer member provided on the exterior of the impression member results in a force being applied to at least the one or more of the cells comprised within the transfer member, causing the substance(s) comprised within the cells to transfer to the first absorbent layer.

[0238] The one or more cells are constructed such that they can contain a substance described herein. The cell construction is compressible, preferably reversibly compressible, such that the boundary of each cell collapses when force is applied and reverts to it original configuration when force is removed. The action of the cell boundary forces all of the substance contained within the cell through the outward facing apertures and on to the substrate material, i.e. substantially no substance remains in the cell after step (c). This is advantageous because precise quantities of substance can be deposited on the substrate surface in a uniform manner.

[0239] The properties of the substrate upon which the substance is to be applied must also be considered carefully. For example, a substrate material with an irregular surface structure, i.e. an uneven surface, such as nonwoven fibres are notoriously difficult to apply precise and uniform amounts of a substance to using traditional printing techniques.

[0240] The inventors found that by using a transfer member comprising collapsible cells, one or more substances could be forced from the cells, through the outward facing apertures, and on to the substrate surface. The results were found to be particularly good for nonwoven fabrics. Traditional techniques were found to produce a diffuse pattern when printed onto nonwoven fabrics, whereas the method of the invention produced a well resolved print pattern in a uniform manner.

[0241] In various embodiments, the transfer means consists of an impression member and a transfer member. In various embodiments the transfer means consists of the impression member and the transfer member wherein the transfer member is in the form of a layer of the one or more cells.

[0242] In various embodiments at least two transfer means are provided. In various embodiments at least two transfer means are provided, each comprising an impression member and a transfer member. In various embodiments at least two transfer means are provided, each comprising an impression member and a transfer member, wherein each of the transfer members comprise one or more cells with outward facing apertures and are provided on the exterior of the impression members. In various embodiments at least two transfer means are provided, each comprising an impression member and a transfer member, wherein each of the transfer members comprise one or more cells with outward facing apertures and are provided on the exterior of the impression members, and wherein the transfer means are positioned in proximity to each other such that pressure is formed on each transfer member by the corresponding impression members as the first absorbent layer is conveyed along a transport path in a machine direction.

[0243] In various embodiments two transfer means are provided. In various embodiments two transfer means are provided, each comprising an impression member and a transfer member. In various embodiments two transfer means are provided, each comprising an impression member and a transfer member, wherein each of the transfer members comprise one or more cells with outward facing apertures and are provided on the exterior of the impression members. In various embodiments two transfer means are provided, each comprising an impression member and a transfer member, wherein each of the transfer members comprise one or more cells with outward facing apertures and are provided on the exterior of the impression members, and wherein the transfer means are positioned in proximity to each other such that pressure is formed on each transfer member by the corresponding impression members as the first absorbent layer is conveyed along a transport path in a machine direction.

[0244] Where two transfer means are provided, they can be provided in opposing positions and a substrate material can be fed between them in a machine direction. Such an embodiment permits thesimultaneous printing on both sides of the substrate material. This can be advantageous where, for example, different concentration of substances or different types of substance are required on a single piece of substrate material. Alternatively, such a configuration can aid the production of articles have a multilayer construction, thereby increasing efficiency and speed of the manufacturing process.

[0245] In some embodiments the transfer means is a cylinder. In some embodiments the transfer means is stadium-shaped.

[0246] In various embodiments the transfer means comprises an impression member and a transfer member, wherein the transfer member is provided on the exterior of the impression member and wherein the transfer member partially surrounds the impression member in a longitudinal direction of the impression member. In various embodiments the transfer means comprises of impression member and a transfer member, wherein the transfer member completely encompasses the impression member in a longitudinal direction.TRANSFER MEMBER

[0247] As described herein, the transfer member comprises one or more cells with outward facing apertures that are capable of being loaded with one or more substances, which can be transferred to a substrate material. Force applied by the by the impression member to the cells comprised within the transfer member causes the substance(s) contained within the cells to transfer to the first absorbent layer, for example when the force compresses the cells that are formed from an elastomeric material.

[0248] In various embodiments, the one or more cells of the transfer member reversibly compress under force applied by the impression member to at least the one or more cells in step (c) of the above detailed method, so as to cause the one or more substance(s) comprised within the one or more cells to transfer to the first absorbent layer.

[0249] In various embodiments, the transfer member comprises an elastomeric material. In a preferred embodiment, the transfer member consists of an elastomeric material.

[0250] In various embodiments, the transfer member comprises a silicone-based material, an ethylene propylene diene monomer (EPDM) based material, a polypropylene material, a polyethylene terephthalate material, a thermoplastic polyurethane material or combinations thereof. In various embodiments, the transfer member comprises a silicone-based material, an ethylene propylene diene monomer (EPDM) based material, or combinations thereof. In various embodiments, the transfermember comprises a silicone-based material. In various embodiments, the transfer member consists of a silicone-based material. In various embodiments, the transfer member comprises an ethylene propylene diene monomer (EPDM) based material. In various embodiments, the transfer member consists of an ethylene propylene diene monomer (EPDM) based material. In various embodiments, the transfer member comprises a silicone-rubber foam material. In various embodiments, the transfer member consists of a silicone-rubber foam material.

[0251] As described herein, the transfer member has certain characteristics that ensure its suitability as a material for the transfer member(s) of the present invention, particularly for reversible compressibility of the one or more cells comprised within the transfer member(s).

[0252] In some embodiments, the transfer member(s) have a Shore A hardness value of from about 5 to about 30. In some embodiments, the transfer member(s) have a Shore A hardness value of from about 5 to about 25. In some embodiments, the transfer member(s) have a Shore A hardness value of from about 5 to about 20. In some embodiments, the transfer member(s) have a Shore A hardness value of from about 7 to about 20. In some embodiments, the transfer member(s) have a Shore A hardness value of from about 7 to about 15.

[0253] Shore A hardness values can be determined, for example, using an industry standard Durometer in accordance with ASTM D2240.

[0254] In some embodiments, the transfer member(s) have a density of from about 100 to about 500 g / cm3. In some embodiments, the transfer member(s) have a density of from about 100 to about 400 g / cm3. In some embodiments, the transfer member(s) have a density of from about 150 to about 400 g / cm3. In some embodiments, the transfer member(s) have a density of from about 200 to about 300 g / cm3.

[0255] In some embodiments, the transfer member(s) have a compressive stress 40% strain of from about 30 to about 150 KPa. In some embodiments, the transfer member(s) have a compressive stress 40% strain of from about 50 to about 90 KPa. In some embodiments, the transfer member(s) have a compressive stress 40% strain of from about 70 to about 110 KPa.

[0256] In some embodiments, the transfer member(s) have a compression set value (22 hours @ 70°C) of about 20% or less. In some embodiments, the transfer member(s) has a compression set value (22 hours @ 70°C) of about 15% or less. In some embodiments, the transfer member(s) has a compression set value (22 hours @ 70°C) of about 12% or less.

[0257] In some embodiments, the transfer member(s) have a tensile strength of about 0.5 N / mm2or more. In some embodiments, the transfer member(s) have a tensile strength of about 0.6 N / mm2or more. In some embodiments, the transfer member(s) have a tensile strength of about 0.7 N / mm2or more.

[0258] In some embodiments, the transfer member(s) have an elongation to failure of at least about 80%. In some embodiments, the transfer member(s) have an elongation to failure of at least about 100%. In some embodiments, the transfer member(s) have an elongation to failure of at least about 150%.

[0259] In some embodiments, the transfer member(s) have:(a) a Shore A hardness value of from about 5 to about 30;(b) a density of from about 100 to about 500 g / cm3;(c) a compressive stress 40% strain of from about 30 to about 150 KPa;(d) a compression set value (22 hours @ 70°C) of about 20% or less;(e) a tensile strength of about 0.5 N / mm2or more;(f) an elongation to failure of at least about 80%.

[0260] A pattern or design can be provided in the transfer member(s), which will dictate the pattern or design that will be conveyed to the substrate material. In various embodiments, a pattern can be provided in the transfer member(s) by acid etching, laser etching, injection moulded or mechanical engraving. Preferably, a pattern can be provided in the transfer member(s) by laser etching or injection moulded. In various embodiments, a pattern can be provided in the transfer member(s) by 3D printing the transfer member(s).SUBSTANCES & COMPOSITIONS

[0261] To cleanse a wound means to use fluid to remove loosely adherent debris and necrotic tissue from the wound surface. A wound cleanser maybe an aid in debridement -removing deeply adherent, dead or contaminated tissue from a wound - but a debridement solution is not a wound cleanser. Dakin's solution, a buffered 0.5 percent solution of sodium or potassium hypochlorite, is for example a debridement agent rather than a cleansing one because it is injurious to tissues. A desirable wound cleanser should be biocompatible and physiologically compatible with the body tissue. Wound irrigation is the act of flushing a wound with a stream or flow of a solution across an open wound surface. A wound cleanser may also provide additional benefits such as moisturising, which may occur during irrigating or rinsing a wound with the cleanser.

[0262] As described herein, the substances and compositions of the present disclosure disrupt and lift the loose components of wounds from the surface. Surprisingly the substances and compositions further disrupt one or more biofilms. The latter is advantageous because the presence of microbes in wounds is an additional and common impediment to the healing of wounds and can lead to clinical complications.

[0263] As used herein, "microbe" means bacteria, protozoa, fungi, algae, amoeba, and slime molds.

[0264] In various embodiments, the bacterial infection is associated with Staphylococcus aureus or Pseudomonas aeruginosa.

[0265] It has surprisingly been found that substance according to the present disclosure are effective at disrupting biofilms while cleansing and / or irrigating wounds even in the absence of an antimicrobial agent. As used herein, "biofilm" means a syntrophic consortium of microorganisms in which cells stick to each other and optionally also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances (EPSs).

[0266] Thus, in various embodiments, the wound comprises one or more biofilms, wherein "biofilm" is as defined herein. In various embodiments of the wound cleansing dressing for use as described herein, the wound comprises one or more biofilms and treating the wound comprises disrupting said one or more biofilms. As used here, "disrupting" in the context of the one or more biofilms means loosening, softening, and detaching the biofilm from the wound bed.

[0267] The substances of the present invention are advantageous for the treatment of all wounds. Wounds suitable for treatment may, for example, be acute, surgical, or traumatic wounds. Such wounds may be irrigated by the substances of the present invention to remove contamination and debris, and to clean the surrounding skin so that suitable dressings may be applied. Throughout the entire healing pathway, wounds may be cleansed e.g. between dressing changes, to remove excess exudates, debris, non-viable tissues, and to reduce the surface / skin bioburden (e.g. bacteria, thereby reducing infection risk). The substance of the present invention may be used to cleanse a wound that appears to be on a healing pathway in order to prevent opportunistic pathogens from forming biofilm. Cleansing with the substances of the present invention is particularly advantageous after debridement. Wound cleansing may also be performed to assist appropriate inspection and diagnosis. Cleansing with the substances of the present invention is particularly advantageous for the treatment of long-standing, non-healing, so-called chronic wounds.

[0268] According to the present invention, the one or more substance(s) can be applied in the form of a solid, a gel, a wax, a liquid, a suspension, or an emulsion. In a preferred embodiment, the substance(s) are applied in the form of a liquid.

[0269] A wide variety of substances are envisaged for the present invention, which are determined based upon, for example, application of the article, substrate material and printing pattern or design. In various embodiments, the one or more substance(s) are selected from: one or more of a medicament, an adhesive, a deodorant, a chelating agent, a surfactant, an amphoteric surfactant, an anionic surfactant, a cationic surfactant, a thickening agent, an electrically conductive formulation, a thermoresponsive agent, an exothermic agent, an endothermic agent, or a combination thereof.

[0270] In a preferred embodiment, the medicament comprises one or more agents selected from: antimicrobials, analgesics, coagulants, anti-inflammatories or a combination thereof.

[0271] In various embodiments, the one or more substance(s) comprises a wound cleansing or debridement composition. In various embodiments, the one or more substance(s) comprises a wound cleansing or debridement composition comprising a chelating agent, an amphoteric surfactant, and an anionic surfactant.

[0272] In a preferred embodiment, the one or more substance(s) comprises a wound cleansing or debridement composition, preferably wherein the composition comprises:i. a chelating agent;ii. an amphoteric surfactant;iii. an anionic surfactant; andiv. a thickening agent, wherein the thickening agent comprises at least one poly(meth)acrylic acid and / or salt thereof.

[0273] In the present disclosure, the chelating agent may be selected from citrates, tartrates, tartramides, tartrimides, gluconates, lactates, glycolates, oxalates, phosphates, salts of ethylenediaminetetraacetic acid, and mixtures thereof. In some embodiments, the chelating agent may be selected from citrates, phosphates, oxalates, salts of ethylenediaminetetraacetic acid, and mixtures thereof. In various embodiments the salts are metal ion or ammonium salts. The metal ion of said salts is not limited. In various embodiments, metal ion salts are preferred and may be selected from sodium and / or potassium salts. In particularly preferred embodiments, the salts are sodium salts.

[0274] In preferred embodiments the chelating agent comprises a salt of ethylenediaminetetraacetic acid. The ethylenediaminetetraacetate salt may be a mixture of di-, tri-, or tetra-basic salts ofethylenediaminetetraacetate (EDTA). The EDTA salt may, for instance, be a di-sodium salt of EDTA, or calcium di-sodium salt of EDTA, or tetra-sodium salt of EDTA. In various embodiments, the salt of EDTA is a mixture of salts of EDTA. It is believed that EDTA, when present, will have a form which is dependent on the pH of the wound site. In preferred embodiments, EDTA may be added to the wound cleansing or debridement composition as a tetra-basic salt of EDTA such as tetrasodium EDTA. In some embodiments, EDTA is not in the form of the disodium salt.

[0275] The citrate salt may similarly be a mono-, di- or tri-citrate salt. In various embodiments the citrate salt may be mono-, di- or tri-potassium citrate or mono-, di- or tri-sodium citrate. In preferred embodiments, the citrate salt is a tri-citrate salt such as trisodium citrate.

[0276] The tartrate may be a mono-, or di-tartrate salt. In various embodiments, the tartrate salt may be mono- or di-potassium tartrate; or mono- or di-sodium tartrate. In specific embodiments, the tartrate salt is a di-tartrate salt such as disodium tartrate.

[0277] The gluconate may be potassium gluconate or sodium gluconate. In specific embodiments, the gluconate salt is sodium gluconate. Similarly, the lactate may be potassium lactate or sodium lactate. In specific embodiments, the lactate salt is sodium lactate. The glycolate may be potassium glycolate or sodium glycolate. In specific embodiments, the glycolate salt is sodium glycolate.

[0278] The oxalate may be a mono-, or di-oxalate salt. In various embodiments, the oxalate salt may be mono- or di-potassium oxalate; or mono- or di-sodium oxalate. In specific embodiments, the oxalate salt is a di-oxalate salt such as disodium oxalate.

[0279] The phosphate salt may be an ortho-phosphate, a pyrophosphate, a tripolyphosphate or a derivatised phosphate. The phosphate is typically in the form of a potassium or sodium salt. Examples include potassium phosphate dibasic, potassium pyrophosphate, tri-sodium ascorbate phosphate, disodium phosphate and sodium tripolyphosphate. In preferred embodiments the phosphate salt is a di-phosphate salt such as disodium phosphate.

[0280] The chelating agent may be present in the substance in an amount of up to about 10 wt%, up to about 8 wt%, or up to about 6 wt% of the total weight of the substance. In various embodiments, the chelating agent may be present in the substance in an amount of at least about 0.5 wt%, at least about 1.0, or at least about 1.2 wt% of the total weight of the substance.

[0281] In various embodiments, the amphoteric surfactant is selected from hydrocarbyl-amphoacetates, alkenyl-amphoacetates, hydrocarbyl-amphodiacetates, alkenyl-amphodiacetates,hydrocarbylampho-propionates, hydrocarbylampho-diproprionates, hydrocarbylamphohydroxypropyl sultaines, and mixtures thereof. In various embodiments, the hydrocarbyl and alkenyl groups are C6 to C24, C8 to C24, or CIO to C20, hydrocarbyl or alkenyl groups. Typically, the amphoteric surfactant has a counter-ion of an alkali metal such as sodium or potassium, or an ammonium ion. In preferred embodiments, the amphoteric surfactant has an alkali metal counter-ion, and more preferably the counter-ion is sodium.

[0282] As used herein, the term "hydrocarbyl" includes a group such as alkyl, aryl, aralkyl, alkaryl, cycloalkyl or alkenyl, which may be linear or branched, and / or saturated or unsaturated. In one embodiment, the hydrocarbyl may be a linear or branched alkyl or alkenyl group.

[0283] In various embodiments the amphoteric surfactant is a hydrocarbyl-amphoacetate salt, preferably a fatty acid amphoacetate. The fatty acid or salt thereof may be a C6-C24 fatty acid or salt thereof, or a mixture thereof. The fatty acid or salt thereof may be saturated or unsaturated. When unsaturated, the unsaturated fatty acid or salt thereof may be mono- or di-unsaturated. The unsaturated fatty acid or salt thereof may comprise cis- or trans- double bonds or mixtures thereof. In further embodiments, the fatty acid or salt thereof is a C12-C18 monounsaturated fatty acid or salt thereof. Examples of fatty acids include stearic acid, ricinoleic acid, oleic acid, eladic acid, petrolselinic acid, palmitic acid, erucic acid, behenic acid, lauric acid, myristic acid, or linoleic acid.

[0284] In preferred embodiments, the amphoteric surfactant comprises a cocoamphoacetate. The counter-ion of the cocoamphoacetate is preferably sodium. Sodium cocoamphoacetate is commercially available, for example under the trade name Dehyton® MC (BASF) or Amphosol® 1C (Stepan®). Such commercial preparations are typically solutions of sodium cocoamphoacetate, typically containing from about 30 to about 40 wt% sodium cocoamphoacetate on an actives basis.

[0285] In various embodiments, the metal ions of the salt of the chelating agent and the salt of the amphoteric surfactant are the same. Preferably, both the chelating agent and surfactant are sodium salts.

[0286] The amphoteric surfactant may be present in the substance in an amount of up to about 15 wt%, up to about 10 wt% or up to about 5 wt% of the total weight of the substance. In various embodiments, the amphoteric surfactant may be present in the substance in an amount of at least about 1 wt% of the total weight of the substance.

[0287] The anionic surfactant may include all forms of lipophilic oligomeric hydrocarbon and / or polyethoxylate with a negatively charged hydrophilic head group such as carboxylate, sulphate,sulphonate, sulphonated ester, sulphated ester, sulphated amide, carboxylated amide, or phosphate anionic head group. For example, including a fatty acid or fatty acid salt. The fatty acid may comprise 6 to 24 carbon atoms, such as 10 to 20 carbon atoms, preferably 12 to 18 carbon atoms.

[0288] In various embodiments, the anionic surfactant comprises a fatty acid or salt thereof. The fatty acid may comprise 6 to 24 carbon atoms, such as 10 to 20 carbon atoms, preferably 12 to 18 carbon atoms. Examples of fatty acids include stearic acid, ricinoleic acid, oleic acid, eladic acid, petrolselinic acid, palmitic acid, erucic acid, behenic acid, lauric acid, myristic acid, or linoleic acid.

[0289] In some embodiments, the anionic surfactant may be a fatty acid or salt thereof which is a C6-C24 fatty acid or salt thereof, or a mixture thereof. The salt may be an alkali metal or alkaline earth metal salt, preferably an alkali metal salt. In preferred embodiments, the alkali metal is sodium or potassium, more preferably sodium. The fatty acid or salt thereof may be saturated or unsaturated. When unsaturated, the unsaturated fatty acid or salt thereof may be mono- or di-unsaturated. The unsaturated fatty acid or salt thereof may comprise cis- or trans- double bonds or mixtures thereof. In further embodiments, the fatty acid or salt thereof is a C12-C18 monounsaturated fatty acid or salt thereof.

[0290] In particularly preferred embodiments, the fatty acid or salt thereof is oleic acid or a salt thereof. The salt of oleic acid is not limited and may be a metal salt of oleic acid. In various embodiments the salt of oleic acid may be sodium oleate. In various embodiments, the salt of oleic acid may be formed by adding oleic acid to the substance such that the metal ions, e.g. sodium ions, are provided by provided by the chelating agent, the thickening agent and / or the amphoteric surfactant.

[0291] The amount of anionic surfactant in the substance is not necessarily limited. The anionic surfactant may, for example, be present in the substance in an amount of up to about 15 wt%, up to about 10 wt%, or up to about 8 wt% of the total weight of the substance. The anionic surfactant may be present in an amount of at least about 1 wt%, or at least about 1.5 wt% of the total weight of the substance.

[0292] In various embodiments, the anionic surfactant is present in the substance in an amount of from about 1 wt% to about 15 wt%, preferably from about 1 wt% to about 10 wt%, more preferably from about 1.5 wt% to about 8 wt% of the total weight of the substance.

[0001] According to the above description, poly(meth)acrylic acids may be homopolymers, copolymers, or interpolymers. For example, homopolymeric poly(meth)acrylic acids comprise a polymer backbone consisting of repeat units formed from (meth)acrylic acid.

[0002] Poly(meth)acrylic acid copolymers comprise repeat units formed from (meth)acrylic acid and may comprise further repeat units derived from other monomers. Non-limiting examples of such monomers include (meth)acrylate esters, (meth)acrylamides, olefins, maleic anhydrides, vinyl esters, vinyl ethers, and styrenics; as well as unsaturated carboxylic acids other than (meth)acrylic acid. For instance, a poly(meth)acrylic acid copolymer may comprise repeat units formed from (meth)acrylic acid and at least one alkyl acrylate. A non-limiting example of a commonly used alkyl acrylate in such copolymers is C10-C30 alkyl acrylate.

[0003] In various embodiments the poly(meth)acrylic acid and / or salt thereof is an interpolymer. As used herein, the term "interpolymer" refers to a complex comprising at least two polymers. In such interpolymers, one or more of the constituent polymers may be a homopolymer or a copolymer. For example, at least one of the constituent polymers of the interpolymer may be a copolymer of acrylic acid and C10-C30 alkyl acrylate. In various embodiments, and without wishing to be bound by theory, the complex between the at least two polymers arises due to non-covalent interactions. For example one polymer may be entangled within the other and / or be associated via hydrogen bonding. In various embodiments the at least one poly(meth)acrylic acid and / or salt thereof is an interpolymer that comprises a block copolymer comprising polyethylene glycol and a fatty acid ester. In specific embodiments, the fatty acid ester is 12-hydroxystearic acid.

[0004] In any of the embodiments of the at least one poly(meth)acrylic acid and / or salt thereof described above, the poly(meth)acrylic acid and / or salt thereof may be cross-linked. Common crosslinking agents are known in the art. In particular, the at least one poly(meth)acrylic acid and / or salt thereof may be cross-linked with an allyl ether cross-linking agent. In specific embodiments, the allyl ether cross-linking agent is selected from allyl sucrose and allyl pentaerythritol. Interpolymeric polyacrylic acids and / or salts thereof are described in e.g. US Patent Nos. 5,288,814 and 5,349,030, the contents of both being incorporated herein by reference.

[0005] Examples of commercially available interpolymeric polyacrylic acids and / or salts thereof suitable for use in the present disclosure include Carbopol® ETD 2020 and Carbopol® Ultrez 10.

[0006] The salts of the at least one poly(meth)acrylic acid are not limited. Poly(meth)acrylic acids are polyanionic polymers, i.e. the carboxylic acid side-groups of the polymer chain can be deprotonated and thereby acquire negative charge. Accordingly, the at least one poly(meth)acrylic acid whendeprotonated may be associated with any compatible cation, for example when supplied in salt form, or when formulated in the substance or composition as described herein such that cationic species are provided by other components present in the substance or composition. In various embodiments, the poly(meth)acrylic acid and / or salt thereof comprises a sodium salt of poly(meth)acrylic acid. In specific embodiments, counter-ions such as sodium ions may be provided by the chelating agent, the amphoteric surfactant and / or the anionic surfactant. The skilled person will understand that the degree of deprotonation of the poly(meth)acrylic acid will depend on various factors including the pH of the substance or composition, and thus the poly(meth)acrylic acid may be present in the substance or composition of the present disclosure in varying proportions of free acid and (poly)anionic forms thereof. In various embodiments, the pH of the substance or composition is from about pH 4 to about pH 10, from about pH 5 to about pH8, or from about pH 5.5 to about pH 6.5.

[0007] In various embodiments, the at least one poly(meth)acrylic acid and / or salt thereof is present in the substance of the present disclosure in an amount of at least about 0.1 wt%, at least about 0.2 wt%, or at least about 0.3 wt% of the total weight of the substance.

[0008] In various embodiments, the at least one poly(meth)acrylic acid and / or salt thereof is present in the substance of the present disclosure in an amount of up to about 2 wt%, up to about 1.5 wt%, up to about 1 wt%, or up to about 0.5 wt% of the total weight of the substance.

[0009] In various embodiments, the at least one poly(meth)acrylic acid and / or salt thereof is present in the substance of the present disclosure in an amount of from about 0.1 to about 2 wt%, from about 0.2 to about 1.5 wt%, or from about 0.3 to about 1 wt% of the total weight of the substance.

[0293] In a further preferred embodiment, the one or more substance(s) comprises a nonantimicrobial composition, said composition comprising (i) glycerol, triglycerol or a combination thereof, and (ii) one or more C1.4 alcohol, wherein the weight ratio of (i) to (ii) in the composition is from about 2:1 to about 5:1.

[0294] In some embodiments, (i) is glycerol or a combination of glycerol and triglycerol. The combination of glycerol and triglycerol may have a parts by weight ratio of about 99:1 to about 50:50 parts. This range may be combined with the above weight ratio ranges for (i):(ii) as well as the concentration ranges described herein. For example, the non-antimicrobial composition may comprise (i) and (ii) at a weight ratio of from about 2.5:1 to about 4:1, wherein (i) is glycerol or a combination of glycerol and triglycerol, the combination having a parts by weight ratio of about 99:1 to about 50:50.

[0295] In particularly preferred embodiments, (i) in the non-antimicrobial composition is glycerol.

[0296] The concentration of (i) glycerol, triglycerol, or combination thereof is not critical to the present disclosure. As will be appreciated from the scope of the appended claims and the Examples, it is the relative amount of (i) to (ii) the one or more C1-4 alcohol which is important (from about 2:1 to about 5:1, preferably from about 2.5:1 to about 4:1, more preferably from about 13:4 to about 4:1), and the concentrations of (i) and (ii) will depend on the concentration of the one or more excipients. Should the skilled person require a lower limit for (i), (i) may be included in the non-antimicrobial composition in an amount of at least about 50 wt% and preferably about 55 wt%. Should the skilled person require an upper limit for (i), (i) may be included in the non-antimicrobial composition in an amount of no more than about 90 wt% and preferably no more than about 85 wt%. Combining these lower and upper limits provides a general range of at least about 50 wt% to no more than about 90 wt%, and a preferred range of at least about 55 wt% to no more than about 85 wt%.

[0297] In some embodiments, the carrier (i) is glycerol or a combination of glycerol and triglycerol, wherein the combination has a parts by weight ratio of about 99:1 to about 50:50, and wherein (i) is present in the non-antimicrobial composition in an amount of at least about 50 wt% to no more than about 90 wt%. Preferably (i) is glycerol, and glycerol is present in the non-antimicrobial composition in an amount of at least about 50 wt% to no more than about 90 wt%.

[0298] In some embodiments, (i) in the non-antimicrobial composition is glycerol or a combination of glycerol and triglycerol, wherein the combination has a parts by weight ratio of about 99:1 to about 50:50, and wherein (i) is present in the non-antimicrobial composition in an amount of at least about 55 wt% to no more than about 85 wt%. Preferably (i) is glycerol, and glycerol is present in the non-antimicrobial composition in an amount of at least about 55 wt% to no more than about 85 wt%.

[0299] The one or more C1.4 alcohol is included in the non-antimicrobial composition to assist the glycerol, triglycerol, or combination thereof, in the solubilisation of the one or more excipients. As the alcohol is volatile, it can be evaporated off the first absorbent layer after printing. In some embodiments, the one or more C1-4 alcohol is selected from methanol, ethanol and propanol, or isomers and mixtures thereof, preferably wherein the one or more C1-4 alcohol comprises ethanol. In the examples, industrial denatured alcohol is employed but the present disclosure is not limited to this specific form of the one or more C1-4 alcohol.

[0300] In some embodiments, (i) in the non-antimicrobial composition is glycerol or a combination of glycerol and triglycerol, wherein the combination has a parts by weight ratio of about 99:1 to about 50:50; wherein (i) is present in the non-antimicrobial composition in an amount of at least about 50wt% to no more than about 90 wt%; and wherein (ii) the one or more C1-4 alcohol is selected from methanol, ethanol and propanol, or isomers and mixtures thereof. Preferably (i) is glycerol, and glycerol is present in the non-antimicrobial composition in an amount of at least about 50 wt% to no more than about 90 wt%. Particularly preferably, (i) is glycerol, present in the non-antimicrobial composition in an amount of at least about 50 wt% to no more than about 90 wt% and the one or more C1.4 alcohol comprises ethanol.

[0301] In some embodiments, (i) in the non-antimicrobial composition is glycerol or a combination of glycerol and triglycerol, wherein the combination has a parts by weight ratio of about 99:1 to about 50:50; wherein (i) is present in the non-antimicrobial composition in an amount of at least about 55 wt% to no more than about 85 wt%; and wherein the one or more C1-4 alcohol comprises ethanol. Preferably (i) is glycerol, and glycerol is present in the non-antimicrobial composition in an amount of at least about 55 wt% to no more than about 85 wt%. Particularly preferably, (i) is glycerol, present in the non-antimicrobial composition in an amount of at least about 55 wt% to no more than about 85 wt% and the one or more C1-4 alcohol comprises ethanol.

[0302] In any of the above embodiments, the weight ratio of (i) to (ii) in the non-antimicrobial composition may be from about 2.5:1 to about 4:1, preferably from about 13:4 to about 4:1.

[0303] In some embodiments, it may be preferable to avoid use of an non-antimicrobial agent, for example to avoid the risk of resistance to said antimicrobial agent, and / or due to intolerance to the antimicrobial agent in the subject whose wound is to be treated. Wound cleansers that do not contain antimicrobial agents may also be preferable in certain applications because they may not be classed as medicaments.

[0304] Thus, in various embodiments the substances of the present disclosure are non-antimicrobial. For instance, in various embodiments the substances of the present disclosure do not comprise an antimicrobial agent. The non-antimicrobial agent is not limited and includes silver compounds, hypochlorous acid, polyhexamethylene biguanide (also known as polyhexanide biguanide), chlorhexidine and salts thereof.

[0305] The generally accepted criterion for an non-antimicrobial cleanser solution is a 3-loglO reduction in microbial cell number in a given contact time period. Thus, in various embodiments, the non-antimicrobial wound cleansing compositions described herein cause less than about a 3-loglO reduction in the number of microbial cells in the wound when contacted with the wound for about 10 minutes. Preferably, the non-antimicrobial wound cleansing compositions described herein cause less than about a 2-logl0 reduction in the number of microbial cells in the wound when contacted withthe wound for about 10 minutes. More preferably, the non-antimicrobial wound cleansing compositions described herein cause less than about a 1-Iogl0 reduction in the number of microbial cells in the wound when contacted with the wound for about 10 minutes.

[0306] In various embodiments, the substances may be thickened with a thickening agent. Exemplary thickening agents include gums, polysaccharides such as starch, agar, carboxymethylcellulose, hydroxyethylcellulose, gelatin, pectin, chitosan, alginate, clay, synthetic thickeners such as polyethylene glycols, poloxamers (as defined herein above), polyvinyl alcohol / acetate, polyvinylpyrrolidone, polyacrylates, silicates / silica, carbomers. Any of the preceding forms may alternatively be prepared extemporaneously, e.g. by a clinician, healthcare practitioner, or pharmacist. In various embodiments, the substances may be supplied as a concentrate for dilution, e.g. prior to application in a care setting, such as in a bath or bucket for application.

[0307] In various embodiments, the substances of the present invention do not contain further components other than those already described above. In such embodiments, the substances are preferably supplied as a sterile solution, e.g. wherein such solutions are prepared from sterilised components in a sterile environment, or wherein the final solution is sterilised by methods commonly known in the art. In alternative embodiments, the substances of the present invention may comprise one or more additional components selected from preservatives, anti-oxidants, osmotic adjusters and surfactants.

[0308] Suitable preservatives are known in the art, such as polyhexamethylene biguanide (PHMB). Preservatives may advantageously have a mild bacteriostatic effect in the wound. Anti-oxidants are also well known and a person skilled in the art of the present invention will be able to select suitable anti-oxidants. Anti-oxidants may advantageously aid preservation and reduce the prevalence of reactive oxygen species in the wound environment that are typically elevated in chronically inflamed wounds and associated with retarded healing.

[0309] Osmotic adjusters may be included in the solutions of the present invention to adjust the tonicity (ionic strength) of said substances. For example, pain can be minimised by the use of isotonic substances (i.e. having an osmolality similar to plasma). Plasma osmolality typically falls within 0.285 to 0.300 Osmol / kg. Alternatively, hypotonic (i.e. having an osmolality less than plasma) substances may be advantageous to increase surfactancy potential. Conversely, hypertonic (i.e. having an osmolality greather than plasma) solutions may confer bactericidal effects that may be advantageous in various applications. The skilled person will be able to select suitable osmotic adjusters and obtain a desired tonicity as a matter of routine.

[0310] In various embodiments, the wound cleansing composition is an isotonic or hypertonic solution. In various embodiments, one or more surfactants in addition to those described above may be included, e.g. as "secondary surfactants" to boost the primary surfactant as described above. Such secondary surfactants may be any of the surfactants described hereinabove, but do not include cationic surfactants. The wound cleansing composition may have a surface tension of less than about 35 mN / m to facilitate loosening and cleansing.

[0311] In various embodiments, one substance is applied to the first absorbent layer.

[0312] In various embodiments, multiple substances are applied to the first absorbent layer.

[0313] In various embodiments, the one or more substance(s) are applied to a single surface of the first absorbent layer.

[0314] In various embodiments, different substances are applied to different surfaces of the first absorbent layer.

[0315] In various embodiments, a combination of substances are applied to a single surface of the first absorbent layer.

[0316] In various embodiments, a combination of substances are applied to multiple surfaces of the first absorbent layer and / or the absorbent structure.

[0317]

[0318] In some embodiments, the one or more substance(s) transferred to the first absorbent layer is at least partially impregnated within the first absorbent layer.

[0319] In some embodiments, the one or more substance(s) transferred to the first absorbent layer is coated on or at least partially impregnated within the first absorbent layer. In some embodiments, the one or more substance(s) transferred to the first absorbent layer is at least partially impregnated within the first absorbent layer. In some embodiments, the one or more substance(s) transferred to the first absorbent layer is coated on the first absorbent layer.USES

[0320] As described herein, the negative pressure wound dressings of the present disclosure are useful for the treatment of wounds, including initial treatment in first response settings, as well as inongoing wound management such as in primary care settings. The negative pressure wound dressing described herein may be used in cleansing and / or irrigating a wound.

[0321] According to the present invention, the use of the negative pressure wound dressing as disclosed herein may prevent or minimise slough accumulation in a wound or to de-slough a wound, the use comprising contacting said negative pressure wound dressing with said wound or contacting said wound with said negative pressure wound dressing, preferably wherein the wound is a chronic wound, acute wound, or burn.

[0322] In some embodiments the wound is a chronic wound. In some embodiments the wound is a acute wound. In some embodiments the wound is a burn.EXAMPLES

[0323] According to the present invention, the following methods can be used to determine the key characterising features and parameters:

[0324] [Base Weight]Base weight can be calculated using the following formulae:: aie ahi t i «>n of Weight.per Unit AreaMass (M ~ Weight of the sample (g) without the release linerWeight per Unit Area can be calculated from the following equations:per tOty.4 rea (g / cm 2 I ~Orx 10000If'erg / tf perUttf Area {g? m2) -

[0325] [Bulk Density]Bulk density can be calculated using the following formula: / s \Basis Weight jtyJ -s- 1000Bulk DensityThickness (mm) -i- 1000

[0326] [Fluid Absorbency]Fluid absorbency can be determined in accordance with BS EN 13726-1:2002; Test methods for primary wound dressings - Part 1: Aspects of absorbency, Section 3.2.

[0327] [Fluid Retention]Fluid retention can be calculated using the following formulae:§ m mFiuiif Upt &e per wjut area ( — ) = - — -1V3 - H'lF n.iS ifetamerf per t tt area f — =• I = - ' ' 41Percentage Fiuid Petamed = — r— r - — x 100Al = Area of the dressing sample (cm2)W1 = Dressing sample mass (g)W2 = Dressing sample mass + test solution (g)W3 = Dressing sample re-weighed mass (g)For fluid retention, the hydrated sample is placed onto a perforated metal sheet and a compression load (a weight equivalent to 40 mmHg) is applied to the sample for 1 minute. Any unbound liquid is allowed to drain, the sample is then re-weighed (W3).

[0328] [Lateral Wicking Distance]Lateral wicking distance can be determined in accordance with ISO 9073-6:2000 'Textiles - Test methods for nonwovens - Part 6: Absorption'.

[0329] [Absorption Under Compression]This in-vitro test method for determining 'absorption under compression' was carried out based upon standard Pharmacopoeia method (BP 1993, Volume II, Appendices A222, Appendix XX, T. Water Retention Capacity). The method has been developed further to differentiate a dressing's ability to retain and lock away fluid when compression is applied. Based on the measurements taken in this test, the GSM can be calculated for each sample.The area [Al] of the dressing sample is 25cm2. This area is used to calculate the weight required to exert 40mmHg of compression over the dressing pad.The test sample is weighed [Wl] and placed onto a perforated plate within absorption container. A compression load (a weight equivalent to 40 mmHg as commonly applied with a high compression bandage therapy) is applied evenly over the surface of the test sample. Warmed hydrating fluid (Solution A at 37°C ±2°C) is added to the container at a volume such that the perforated plate is covered. Samples are then incubated for 24 hours at 20°C(±2°C). After incubation, the hydrating fluid is drained off prior to removing the weights. Each sample is removed from the solution and the sample is weighed again [W2],Absorption under compression can subsequently be determined using the following formula:# I- 2 - Fluid Dpta g w unit area i - 1 = -.41

[0330] [Dimensional Shrinkage]This in-vitro test method for determining 'dimensional shrinkage' was carried out based upon BS ISO 1817:2015 'Rubber Vulcanized or Thermoplastic-Determination of the Effect of Liquids', although the method has been developed further. This in-vitro test method was carried out by measuring the dry dimensions [LI, Wl] and area [Al], hydrating each sample with an excess of Solution A (ref: BS EN 13726-1:2002 Test methods for primary wound dressings - Part 1: Aspects of absorbency, Section 3.2.2.3) until fully hydrated, then measuring the wet dimensions [L2, W2] and area [A2] and calculating the percentage shrinkage. All samples cut using a standard 5x5cm cutting die. Accordingly, dimensional shrinkage (in the machine direction) can be calculated using the following formula:LI — £2Dimensional shrinkage (%) x 100£1The same formula can be used to determine dimensional shrinkage in the transverse direction by replacing the [LI] and [L2] values with [Wl] and [W2],

[0331] [Wet Tensile Strength]Wet tensile strength can be determined in accordance with the test method provided in ISO 9073-3:1989; Textiles - Test method for nonwovens - Part 3: Determination of tensile strength and elongation.

[0332] [Dry tensile strength]Wet tensile strength can be determined in accordance with the test method provided in ISO 9073-3:1989; Textiles - Test method for nonwovens - Part 3: Determination of tensile strength and elongation.

[0333] [Lap Draft]Lap Draft is defined as:Web Speed Out (VJ Web Mass In (Mt)Draft (V) =Web Speed In (Vt) ~ Web Mass Out (Mo)Draft can be expressed as a ratio or percentage increase factor.

[0334] [Needle Punch Density]Needle Punch density is defined as:nnnnSf- x n„=~A=P i ~ P / SfWhere:Pci= Needle punch density (punches / cm2)nn= Number of needles per unit width (cm ~1jA = Advancement per stroke (cm)P = Production Rate (cm / miri)Sf = Punch (stroke) f requency (punches / min)Example 1 - Textile Process

[0335] The specification of the equipment that forms the process is as follows:Table 1Machine Name Make MedelOpener! DUo [Temafa] Custom BuiltChute Clio (Spinnbau) Custom BuiltBelt Weigher Olio (SpinnbauJ MEZ 2149-WLBA-2CQS-ENGQCard Olla ^Spinnbau] C4P 215S-K1-BA-20G9-ENQ0^2^Web^raSsr DiMSphmbau) vsio'mNeedle Loom Olio 01-LOOM 00-1820LI eta I Detector Erhardt * Lei mar MDT003Accumulator T Diio

[0336] Fibre Feeder & Opener

[0337] The staple fibre is manually deposited into a hopper, from which it is sheared and conveyed by an inclined spiked lattice infeed. At the top of the lattice infeed, a pair of levelling and back stripping rollers removes a consistent amount of fibre from the spiked lattice, while the remaining fibres return to the hopper based on the design of the equipment.

[0338] Next, the fibre is conveyed by a flat belt into the opener, which is of single roll wired roll design. The primary function of the opener is to perform a low level of fibre opening, which does not result in high levels of blending or mixing, as this was not part of the original equipment design scope.

[0339] The opened fibre is then transported via a fan through a fibre separation device, which effectively removes fine particulate matter, such as broken fibres.

[0340] Chute, Condenser & Weighing

[0341] The chute infeed is designed to ensure an even distribution of incoming fibres across the width of the condenser. The condenser allows for the accumulation and condensing of opened fibres, resulting in a consistent density for discharge onto the weigh belt. Fibre is dispensed from the condenser onto a belt weighed, which is used to precisely control the weight of fibre entering the card.

[0342] Card

[0343] A fibre blend of the invention employs a single section and single cylinder arrangement card. At the card, fibres are fed by a "licker-in" on the main cylinder, and they are repeatedly "worked" off and "stripped" by alternately counter-rotating rollers dressed in toothed card wires onto the main cylinder until they reach the doffer. This process has the effect of opening the fibres further, but its primary purpose is to re-orient the fibres along the machine direction.

[0344] Once the fibres reach the doffer, they are doffed onto a conveyor belt, resulting in a web with fibre orientation predominantly in the machine direction and a consistent weight of approximately 14gsm, finish, and quality.

[0345] Cross Lapper

[0346] After leaving the card, the single layered lightweight web undergoes a process called cross lapping, where layers of the doffed web are laid in a zigzag pattern at 90° to the card path. The basis weight of the finished textile can be adjusted by increasing or decreasing the number of cross-lapped layers per linear distance. Once cross-lapped, the fibres are predominantly oriented in the transverse direction of the machine path.

[0347] Web Drafter

[0348] Due to its preferential transverse fibre orientation, the resulting web is anisotropic in terms of tensile strength. However, web drafting can partially re-orient fibres from the transverse direction to the machine direction by stretching the textile web, thereby reducing anisotropic tensile properties.

[0349] The level of draft can be adjusted to optimize tensile strength directionality ratios, textile thickness, and density. This process involves the stretching or drafting of the textile web, which allows for the partial re-orientation of fibres from the transverse direction to the machine direction.

[0350] Needle Loom

[0351] At this point, the textile possesses moderate levels of tensile strength in the x and y directions, but very little in the z direction (between layers). The needle loom process involves mechanical bonding, which interlocks fibres across multiple cross-lapped layers through the use of barbed needles, achieving a high degree of fibre entanglement. Process parameters at the needle loom can be modified to influence the textile's tensile strength, thickness, and density.Example 2.1 - Textile Trial 1

[0352] The lOOgsm fabric is processed with Lap Drafter settings at 71% and Needle Punch Density (NPD) of 45 / cm2. Textiled nonwoven fabrics at a heavier weight of 150gsm, with a blend of carboxymethylcellulose and modified cellulose (Lyocell) were trialled. The draft and needle punch density were varied to affect the physical properties of the textile fabric. 20 different fabrics were made during the trial, with wet tensile strength testing performed at the time of production.Table 2 -Trial 1Roll no RM Number wt% Lyocell Needle Punch Density Lap Drafter Settings1 RM01552 / 20 0 45cm2 NPD: Standard 74.58% LD: Standard 2 RM 01553 / 20 0 65cm2 NPD: Increased 59.54% LD: Reduced 3 RM01554 / 20 0 28cm2 NPD: Reduced 59.54% LD: Reduced 4 RM01555 / 20 0 45cm2 NPD: Standard 91.61% LD: Increased 5 RM01556 / 20 0 65cm2 NPD: Increased 91.61% LD: Increased 6 RM01557 / 20 10 45cm2 NPD: Standard 74.58% LD: Standard 7 RM01558 / 20 10 65cm2 NPD: Increased 59.54% LD: Reduced 8 RM01559 / 20 10 28cm2 NPD: Reduced 59.54% LD: Reduced 9 RM01560 / 20 10 45cm2 NPD: Standard 91.61% LD: Increased 10 RM01561 / 20 10 65cm2 NPD: Increased 91.61% LD: Increased 11 RM01562 / 20 15 45cm2 NPD: Standard 74.58% LD: Standard 12 RM01563 / 20 15 28cm2 NPD: Reduced 59.54% LD: Reduced 13 RM01564 / 20 15 65cm2 NPD: Increased 59.54% LD: Reduced 14 RM01565 / 20 15 45cm2 NPD: Standard 91.61% LD: Increased 15 RM01566 / 20 15 45cm2 NPD: Standard 59.54% LD: Reduced 16 RM01567 / 20 20 45cm2 NPD: Standard 74.58% LD: Standard 17 RM01568 / 20 20 65cm2 NPD: Increased 74.58% LD: Standard 18 RM01569 / 20 20 45cm2 NPD: Standard 59.54% LD: Reduced 19 RM01570 / 20 20 65cm2 NPD: Increased 59.54% LD: Reduced 20 RM01571 / 20 20 28cm2 NPD: Reduced 59.54% LD: ReducedTable 3 - Trial 1Roll Mean Wet Tensile Strength (N / cm) Mean Fluid Absorbed Mean Fluid Retained Number Machine Direction Transverse Direction per unit area (g / cm2) per unit area (g / cm2) 1 0.86 2.18 0.2135 0.18682 1.14 2.66 0.2049 0.18163 0.45 2.29 0.2516 0.22084 0.73 1.66 0.2173 0.19215 0.91 1.57 0.2168 0.18806 0.88 2.44 0.2354 0.20447 1.73 3.82 0.2167 0.19098 0.44 1. T1 0.2712 0.22559 0.98 4.20 0.2260 0.195410 1.03 2.46 0.1920 0.169111 1.93 7.44 0.2348 0.206112 0.94 5.69 0.2698 0.212413 2.18 6.68 0.2009 0.180014 1.59 5.31 0.2163 0.184715 1.49 6.10 0.2366 0.207916 1.34 4.40 0.2253 0.197117 2.04 6.36 0.2009 0.175018 1.72 7.09 0.2360 0.205219 2.46 7.00 0.2123 0.189220 0.87 5.83 0.2778 0.2236

[0353] 12 of these fabrics reached the wet tensile strength specification of >lN / cm with 8 not reaching lN / cm. Ideally, the nonwoven blended fabrics need to match the actual wet tensile strength of AQUACEL® Extra (2.4N / cm), which was only achieved by roll 19.

[0354] Absorbencies for all fabrics exceeded the AQUACEL® Extra specification of >0.17g / cm2, and 16 also achieved the AQUACEL® Extra actual absorbency of 0.21g / cm2. However, it is predicted that the absorbency and wet tensile strength properties have an inverse effect on each other.Example 2.2 - Textile Trial 2

[0355] 15 different runs were selected in the Design of Experiments (D of E) which estimated where the outer limitations of the setting combinations would be in relation to the physical performance of the blended fabrics. An extra run of 'mid-point' settings aiming to produce a 200gsm fabric was added to determine if increasing the basis weight increased the strength of the fabric. Rolls 7, 8 and 9 were produced with identical settings as the mid-point of the D of E, and assessed to prove repeatability of the fabric's physical properties. The needle punch density and lap drafter settings were rounded to set mid points, and then set to lower and higher limits evenly from these.Table 4 -Trial 2wt% Needle PunchRoll no RM Number gsm target Lap drafter settings Lyocell DensityRoll 1 RM01587 / 20 150gsm 10 25 65Roll 2 RM01588 / 20 150gsm 10 45 50Roll 3 RM01589 / 20 150gsm 10 45 80Roll 4 RM01590 / 20 150gsm 10 65 65Roll 5 RM01591 / 20 150gsm 20 25 50 Roll 6 RM01592 / 20 150gsm 20 25 80Roll 7 RM01593 / 20 150gsm 20 45 65Roll 8 RM01594 / 20 150gsm 20 45 65Roll 9 RM01595 / 20 150gsm 20 45 65Roll 10 RM01596 / 20 150gsm 20 65 50Roll 11 RM01597 / 20 150gsm 20 65 80Roll 12 RM01598 / 20 150gsm 30 25 65Roll 13 RM01599 / 20 150gsm 30 45 50Roll 14 RM01600 / 20 150gsm 30 45 80Roll 15 RM01601 / 20 150gsm 30 65 65Roll 16 RM01602 / 20 200gsm 20 45 65Table 5 - Trial 2Roll Mean Wet Tensile Strength (N / cm) Mean Fluid Absorbed Mean Fluid Number Machine Direction Transverse Direction per unit area (g / cm2) Retained per unit area (g / cm2) 1 0.46 2.48 0.2741 0.21512 1.11 4.3 0.2161 0.18583 1.36 4.48 0.2141 0.17544 1.27 4.22 0.1941 0.16825 0.86 6.54 0.2893 0.22266 0.79 2.87 0.2440 0.19267 1.81 6.46 0.2155 0.17668 1.56 5.18 0.2233 0.18969 1.84 6.48 0.2110 0.175110 2.8 9.79 0.1954 0.175211 1.9 5.29 0.1802 0.154012 0.65 3.05 0.2533 0.185613 1.5 6.14 0.2236 0.192114 1.86 5.39 0.2058 0.171915 2.48 6.1 0.1908 0.172516 1.51 5.18 0.2368 0.2104

[0356] Two of the fabrics reached the actual wet tensile strength of AQUACEL® Extra of 2.4N / cm. Both these fabrics were made with a NPD of 65 and roll 10 had 80 / 20 wt% carboxymethylcellulose / modified cellulose (Lyocell), 50%LD settings and roll 15 had 70 / 30 wt% carboxymethylcellulose / modified cellulose (Lyocell), 65% LD settings.

[0357] 11 out of the 16 fabrics exceeded actual AQUACEL® Extra absorbency of 0.21g / cm2. Three of the rolls had absorbencies of more than 0.25g / cm2, which were all textiled with a needle punch density of 25 - this suggests that a lower NPD allows a fabric to have more absorbent properties due to less needling and loftier fabric.

[0358] The scatter graph presented in Figure 1 provides a plot of the roll's performances in relation to absorbency versus wet tensile strength. There is a pattern showing the higher strength fabrics have a lower absorbency and vice versa. The results which have the best compromise are aligned with the midpoint settings chosen by the design of experiments. These rolls (7, 8 and 9) had settings of 80 / 20 wt% carboxymethylcellulose / modified cellulose (Lyocell), 45NPD and 65%LD (also the mid settings for the NPD and LD settings).Example 2.3 - Textile Trial 3

[0359] This trial was aimed at producing higher weight fabrics (200gsm) to determine if the is a correlation between gsm and the wet tensile strength and absorbency properties. Four runs were selected with two different percentages of modified cellulose (Lyocell) and two different needle punch densities. It was determined from Trial 2 that the Needle Punch Density is a key influencing factor of the fabric's physical properties. An additional roll of higher weight 100% AQUACEL® was also produced for comparison.Table 6 - Trial 3gsm wt% Needle Punch Lap drafterRoll no RM Numbertarget Lyocell Density settings1 RM01611 / 20 200 25 55 502 RM01612 / 20 200 25 50 503 RM01613 / 20 200 30 55 504 RM01614 / 20 200 30 50 505 RM01615 / 20 250 0 55 50Table 7 - Trial 3Roll Mean Wet Tensile Strength (N / cm) Mean Fluid Absorbed Mean Fluid Retained Number Machine Direction Transverse Direction per unit area (g / cm2) per unit area (g / cm2) 5 2.64 7.60 0.2617 0.24431 7.14 26.03 0.2423 0.22062 2.72 9.61 0.2466 0.22563 7.07 25.33 0.2483 0.22714 7.07 25.97 0.2430 0.2208

[0360] Three of the fabrics textiled were over 7N / cm wet tensile strength in the weaker direction, which is 3 times the actual result of standard AQUACEL® Extra. These fabrics were quite stiff due to density of the fabric, therefore lost some of the conformability and loft.

[0361] All fabrics had better absorbencies than AQUACEL® Extra. Surprisingly, the very strong fabrics, also have increased absorbency, so this was not compromised. This could be due to the increasedamount of carboxymethylcellulose present (200gsm fabric, 20 wt% modified cellulose (Lyocell) = 160gsm; 30 wt% modified cellulose (Lyocell) = 140gsm) which may be providing the absorbent properties of the fabric. The 100% carboxymethylcellulose fabric (around 250gsm) had the best absorbency of 0.26g / cm2.

[0362] The scatter plot provided in Figure 2 shows three of the four blended fabrics have a very high wet tensile strength of 7N / cm (consisting of 70 / 30 wt% carboxymethylcellulose / modified cellulose (Lyocell) or made with 55 NPD). The other blend had a lower wet tensile strength with 75 / 25 wt% carboxymethylcellulose / modified cellulose (Lyocell) and 50NPD. All of the fabrics had equivalent or better wet tensile strength, and all had improved absorbency.Example 2.4 - Textile Trial 4

[0363] This trial lowered the gsm to 180gsm and 160gsm with very similar settings to Trial 3. There were slight variations in Needle Punch Density and targeted gsm. The lap drafter settings were not changed due to not having an influence on the results.Table 8 - Trial 4Roll gsm Needle Punch Lap drafter settingsRM Number wt% Lyocellno target Density1 RM 01647 / 21 180 25 55 502 RM01648 / 21 180 25 52 503 RM01649 / 21 160 25 55 504 RM01650 / 21 160 25 52 50Table 9 - Trial 4Roll Mean Wet Tensile Strength (N / cm) Mean Fluid Mean Fluid Number Machine Direction Transverse Direction Absorbed per unit Retained per unit area (g / cm2) area (g / cm2)1 2.574 8.652 0.2192 0.18712 2.896 10.695 0.2210 0.19843 2.384 8.894 0.2145 0.18704 2.149 7.894 0.2179 0.1951

[0364] Reducing the gsm of the blended fabrics affects the tensile strength quite considerably, as 3 were equal or better than AQUACEL® Extra for wet tensile strength, whereas one of the 160gsm fabrics has not matched the AQUACEL® Extra tensile strength.

[0365] The absorbencies of the blended fabrics were all improved compared with AQUCAEL® Extra. The results were all very similar, with the best absorbency and retention for the fabric produced with75 / 25 wt% carboxymethylcellulose / modified cellulose (Lyocell), 52NPD and 50% LD settings at 180gsm target weight.

[0366] The scatter plot provided in Figure 3 shows the two 180gsm blended fabrics both have better wet tensile strength and absorbency compared with AQUACEL® Extra. This suggests that the weight of the blended nonwoven fabric is an important parameter. The NPD was only changed marginally, which didn't alter the results to a significant degree.Example 3 - Comparative Testing vs AQUACEL® Extra

[0367] A textile material according to the present invention (" TL5") was prepared for comparative testing relative to a commercially available alternative (AQUACEL® Extra; Convatec Ltd).The textile material of the invention comprised:- Carboxymethylcellulose (Hydrofiber) content: 75 wt%; Modified cellulose (Lyocell) content 25 wt%- Needle punch density: 50 punches / cm2- Basis Weight: 178gsm- Target Thickness: 2.42mm to produce a bulk density of 75kg / m3The AQUACEL® Extra material of the invention comprised:- Carboxymethylcellulose (Hydrofiber) content: 100 wt%- Needle punch density: N / A- Basis Weight: 149gsm- Target Thickness: 2.03mm to produce a bulk density of 73kg / m3.

[0368] Fluid Absorbency & Retention

[0369] Testing shows that AQUACEL® Extra has a fluid absorbency of 0.21±0.01 g / cm2and a fluid retention of 78% (See Figure 4). TL5 has a fluid absorbency of 0.23±0.03 g / cm2and a fluid retention of 89%. Statistically the TL5 fabric is performing significantly better than AQUACEL® Extra (P=0.023).

[0370] Lateral Wicking Distance

[0371] Testing shows that AQUACEL® Extra wicks at 19±0.58mm in the machine direction and 12±0.58mm in the transverse direction (See Figure 5). TL5 wicks at 19±3mm in the machine directionand 20±2mm in the transverse direction. Statistically the TL5 fabric is performing significantly better than AQUACEL® Extra (P=0.023). Statistical analysis shows that the TL5 base material performs similarly to AQUACEL® Extra in the machine direction (P=0.468), but wicks significantly more in the transverse direction (P=0.000). A significant difference was also seen when comparing TL5 and AQUACEL® Extra in the furthest wicking direction TL5 estimated to wick 1mm further than AQUACEL® Extra over the one-minute timeframe (P=0.039)

[0372] Wet Tensile Strength

[0373] Testing shows that AQUACEL® Extra has a wet strength of 2.56±0.24 N / cm in the weakest direction (TD) (see Figure 6). TL5 performed at 4.51±1.02 N / cm, i.e. significantly better than AQUACEL® Extra. This indicates the TL5 fabric will maintain structural integrity when removed from a wound site.

[0374] Absorption Under Compression

[0375] TL5 performed at 0.16±0.01 g / cm2, significantly better than AQUACEL® Extra having a mean of 0.13 g / cm2 (see Figure 7, cf. " Ho") (P=0.000). Improved absorbency under compression in comparison to AQUACEL® Extra has been attributed to the higher entanglement of the fibres due to the higher needle punch density used in the production process. Whilst decreased needle punch density allows for better absorption under a free swell environment, this is not necessarily the case under compression. At lower entanglement more fluid can be absorbed between the fibre structure, however it is the fluid immobilised within the fibres, that contributes to better performance within this test. The overall increased weight per unit area of the fabric also adds to the differentiation seen in absorbency per unit area in comparison to AQUACEL® Extra.

[0376] Dry Tensile Strength

[0377] TL5 performed at 21.3±2.6 in the weakest (machine) direction, significantly better than AQUACEL® Extra at 17.4±1.7N / cm (see Figure 8, cf. " Ho") in the weakest (machine) direction (P=0.000). Increased dry strength has been achieved through increased basis weight and increased entanglement due to the higher needle punch density used, which has proven to be more effective than the stitchbonding used in AQUACEL® Extra, in producing this strength.

[0378] The inventors found that dry tensile strength data does not provide an indication as to how the dressing will perform, as it is the wet tensile strength that is critical to dressing removal, which is also more easily impacted by the fabric design and processing parameters. It should also be noted thatthe dry tensile strength is not a reflection of how the fabric behaves when wet, as shown in Figure 9, where the wet tensile strength is reduced as a consequence of increased carboxymethylcellulose (Hydrofiber) content, whereas the dry tensile strength is maintained or improved.

[0379] Dimensional Shrinkage

[0380] AQUACEL® Extra is currently performing at 11±1% in the machine direction and 20±l% in the transverse direction (See Figure 10). TL5 base fabrics design sees minimal improvement in shrinkage in the machine direction to 9%±1, but it has enabled the shrinkage in the transverse direction, also 9%±1, to be halved in comparison to AQUACEL® Extra. Removal of the stitching has provided immediate shrinkage to behave similarly in both directions which will benefit the end user in terms of the dressing wounds ensuring the required overlap onto peri-wound environment is in place. The improvement seen is significant in both machine (P=0.014) and transverse (P=0.000) directions.Example 4 - Negative Pressure Wound Dressing Evaluation

[0381] Negative pressure wound dressings were prepared that are suitable to manage high levels of exudate under negative pressure conditions, while avoiding maceration in the skin surrounding a wound. The wound dressing seeks to provide good wicking properties from the wound site and between the absorbent layers, which aids the spread of exudate across a greater area of the dressing but away from the wound. In this way exudate is spread across a large surface area to provide sufficient moisture vapour transmission but in a location distant from the wound and skin. Such a mechanism avoids maceration of the skin surrounding the wound, since the exudate is not contained in contact with the skin. This allows longer wear time for the patient and less disturbance of the wound on dressing change.

[0382] Wound dressings were prepared using the following construct: an adhesive border skin contact layer, a first absorbent layer formed by a non-woven fabric, a transmission layer, a second absorbent layer (e.g. a superabsorbent layer) and a backing layer including an airway port to provide the negative pressure aperture.

[0383] Two variants were compared where the first absorbent layer formed by a non-woven fabric was different. In the control, the first absorbent layer was formed by a non-woven fabric consisting of carboxymethylcellulose fibres and stitched using a lyocell yarn (produced under the trade name Tencel™ yarn). This layer had a density of 100 gsm. In the dressing according to the invention, the first absorbent layer was formed by a non-woven fabric consisting of 75 / 25 wt%carboxymethylcellulose / modified cellulose (Lyocell). The layer was not stitch bonded and had a density of 180gsm.

[0384] A formulation representative of a wound exudate, including a dye comprising 0.25g / L Eosin Y, was used to simulate the production of exudate from a wound bed. The formulation was injected into a fluid inlet, simulating a wound bed (see Figure 14). The fluid was injected at the fluid inlet for 7 days at a flow rate of 0.938 ml / hr.

[0385] It was found that in dressings in accordance with the invention, exudate travels across the dressing to the negative pressure port in a direct manner, when compared with the simulated exudate injected into the control dressing. This is illustrated in Figures 15 (Backing Side), 16 and 17 (Wound Side) (A / B are control; C / D are dressings of the invention). It was also found that the dressing of the invention was comparable to that of the control for establishing negative pressure over the wound site, and in 50% of replicates actually maintained lower negative pressure than the control dressing (approximately -92 to -98 mmHg relative to -72 mmHg of the control). Both of these properties are advantageous, given the lack of stitch bonding in the first absorbent layer, which allows for, among other things, simpler methods of manufacture.

Claims

CLAIMS1). A negative pressure wound dressing, the dressing comprising:a backing layer, an adhesive border skin contact layer, and an absorbent structure arranged between the backing layer and the adhesive skin contact layer;wherein the adhesive skin contact layer is configured to detachably adhere the dressing to a dermal surface;wherein the backing layer comprises a coupling member configured to connect the dressing to a negative pressure source;wherein the absorbent structure comprises a plurality of absorbent layers and a transmission layer, and at least two of the layers in the absorbent structure are laminated together; wherein a first absorbent layer comprises a non-woven fabric, wherein the non-woven fabric comprises gelling fibres and non-gelling fibres, wherein the gelling fibres are present in an amount of from about 60 to about 95 wt% of the first absorbent layer and the non-gelling fibres are present in an amount of from about 5 to about 40 wt% of the first absorbent layer; and wherein a second absorbent layer is located between the first absorbent layer and the transmission layer or the transmission layer is arranged between the first absorbent layer and the second absorbent layer.2). A negative pressure wound dressing according to claim 1, wherein the adhesive skin contact layer provides an adhesive border.3). A negative pressure wound dressing according to claims 1 or 2, wherein the adhesive skin contact layer comprises a window.4). The negative pressure wound dressing according to any one of claims 1 to 3, wherein the gelling fibres are selected from: carboxymethylcellulose fibres and derivatives thereof, modified cellulosic fibres, alkyl sulphonate modified cellulosic fibres, pectin fibres, alginate fibres, chitosan fibres, hyaluronic acid fibres, fibres derived from gums, non-cellulose synthetic fibres, superabsorbent fibres, and combinations thereof; preferably wherein the gelling fibres are carboxymethylcellulose fibres or derivatives thereof.5). The negative pressure wound dressing according to any one of claims 1 to 4, wherein the nongelling fibres are selected from: cellulosic fibres, modified cellulosic fibres, polyester fibres,polypropylene fibres, polyamide fibres, or combinations thereof; preferably wherein the nongelling fibres are modified cellulosic fibres.). The negative pressure wound dressing according to any one of claims 1 to 5, wherein the gelling fibres and non-gelling fibres are present in the non-woven fabric at a weight ratio of from about 85:15 to about 65:35; preferably wherein the gelling fibres and non-gelling fibres are present in the non-woven fabric at a weight ratio of about 80:20 to about 70:30.). The negative pressure wound dressing according to any one of claims 1 to 6, wherein the first absorbent layer has a basis weight of about 150 - 200 gsm; preferably wherein the first absorbent layer has a basis weight of about 160 - 185 gsm.). The negative pressure wound dressing according to any one of claims 1 to 7, wherein the first absorbent layer has a fluid absorbency of about 0.15g / cm2or more.). The negative pressure wound dressing according to any one of claims 1 to 8, wherein the first absorbent layer has a dimensional shrinkage of no greater than about 15 % in the machine direction and in the transverse direction.0). The negative pressure wound dressing according to any one of claims 1 to 9, wherein the first absorbent layer has a wet tensile strength of at least about 1.0 N / cm.1). The negative pressure wound dressing according to any one of claims 1 to 10, wherein the first absorbent layer has a dry tensile strength of at least about 9.0 N / cm.2). The negative pressure wound dressing according to any one of claims 1 to 11, wherein the first absorbent layer consists of the non-woven fabric; preferably wherein the non-woven fabric consists of the gelling fibres and the non-gelling fibres.3). The negative pressure wound dressing according to any one of claims 1 to 12, wherein each of the first absorbent layer, the transmission layer and the second absorbent layer are laminated together.). The negative pressure wound dressing according to any one of claims 1 to 13, wherein each of the first absorbent layer, the transmission layer and the second absorbent layer are laminated together by a scatter-coat adhesive.). The negative pressure wound dressing according to any one of claims 1 to 14 wherein the transmission layer is arranged between the first absorbent layer and the second absorbent layer.). The negative pressure wound dressing according to any one of claims 1 to 15, wherein the transmission layer is laminated on a first surface to the first absorbent layer and on a second surface to the second absorbent layer.). The negative pressure wound dressing according to any one of claims 1 to 16, wherein the transmission layer is a polyurethane foam, a polyester foam, a hydrophilic polyurethane, silicone, gelatine, polypropylene, nitrile or EVA foam.). The negative pressure wound dressing according to any one of claims 1 to 17, wherein the second absorbent layer is a non-woven material.). The negative pressure wound dressing according to any one of claims 1 to 18, wherein the second absorbent layer comprises sodium polyacrylate.). The negative pressure wound dressing according to any one of claims 1 to 19, wherein at least two of the first absorbent layer, the transmission layer and the second absorbent layer are laminated together by heat lamination.). The negative pressure wound dressing according to any one of claims 1 to 20, wherein the second absorbent layer is a superabsorbent layer.). The negative pressure wound dressing according to any one of claims 1 to 21, wherein the first absorbent layer is not stitch bonded.). A process for preparing a negative pressure wound dressing according to any one of claims 1 to 22, wherein the process comprises the steps:(a) Providing an adhesive skin contact layer and a backing layer;(b) Providing a first absorbent layer, a transmission layer and a second absorbent layer; (c) Adhering together at least two of the first absorbent layer, the transmission layer and the second absorbent layer to form an absorbent structure; and(d) Arranging the absorbent structure between the adhesive skin contact layer and the backing layer;wherein, in step c, each of the first absorbent layer, the transmission layer and the second absorbent layer are adhered together by lamination.). A kit comprising a backing layer and an absorbent structure for a negative pressure wound dressing according to any one of claims 1 to 22.). A negative pressure wound exudate management system comprising the negative pressure wound dressing according to any one of claims 1 to 22, a source of negative pressure, and a coupling member for providing negative pressure to the negative pressure wound dressing.

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