GB2414397A - Self-irrigating / reservoir wound dressing - Google Patents

Abstract

A wound dressing comprising: a liquid-impermeable backing sheet 1, a layer of adhesive 2 on the backing sheet 1, an hydrophilic absorbent pad 3 applied to the adhesive-coated side of the backing sheet 1 such that an adhesive-coated margin of the backing sheet 1 extends around the absorbent pad 3 and a reservoir 6 of wound irrigation liquid 9 (sterile saline solution) situated between the absorbent pad 3 and the backing sheet 1, wherein the reservoir 6 comprises a zone of weakness (eg. pull thread 8 or pressure point 12 of Fig 3) whereby the irrigation liquid 9 can be released from the reservoir 6 while the wound dressing is attached to a patient. Element 4 illustrates a perforated retaining sheet.

Description

24 1 4397 LSE.LE-IRRICATING WOD DRrSLSIN(i The present invention relates

to self:irrigating wounti dressings.

Wound irrigation is an important aspect of' wound treatment. Irrigation with sterile saline solutions is used to clean, humidii'y, and soothe wounds, and in particular to assist with the removal ol'adhererlt fragments ol' wound dressings or the like. 'I'he saline solution may also include therapeutic agents, such as a local anacsthetic or an antiseptic.

('lassical wound irrigation is relatively messy anti takes place under non-sterile conditions.

/t need exists for more economical, efficient and sterile methods of' wound irrigation.

So-called island dressings are widely USCti in wound treatment. Such dressings comprise: a liquiti-hnpermeable backing sheet, a layer ol' adhesive on the hacking', sheet, and an absorbent pad (or island) applied to the adhesive-coated side of the backing sheet such that an adhesivecoated margin ol' the hacking sheet extends around the absorbent pad i-'r attaching the dressing to the skin of a patient ar-,urld the wound to be treated.

W()()1/12116 describes island-type wound dressings having a perforated conduit for 2() liquids extending under the adhesive margin. Liquid can be introduced ink, the conduit to assist removal of' the dressing by dissolving or otherwise releasing,, the adhesive. 'I'here is no teaching or suggestion to use such a conduit for wound irrigation.

1JiS-A-2489675 describes island-type wound dressings having a reservoir of a medicament located between the absorbent pad and the backing sheet. 1\ frangible portion of the reservoir is broken off to release the medicament immediately bel'ore the dressing is applied to a patient.

IJS-A-35X()254 describes island-type dressings having a capsule of' medieament located between the absorbent island and the backing sheet. 'I'he capsule can be ruptured to release the medicament after the dressing has beer applied to a patient. 'I'here is no teaching or suggestion of using such a capsule for wound irrigation.

The present invention provides a wound dressing comprising: a liquidimpermeable backing sheet, a layer ot'adllesive on the backing sheet, an absorbent pad applied to the adhesive-coated side of the backing sheet such that an adhesive-coated margin of' the backing sheet extends around the absorbent pad, and a reservoir of wound irrigation liquid situated between the absorbent pad and the backing sheet, wherein the reservoir comprises a zone oi'weakoess whereby the irrigation liquid can be released from the reservoir while the wound dressing is attached to a patient.

The backing sheet is usually substantially liquid-imperrlleable. 'I'hat is to say, it is substantially continuous and substantially free prom macroscopic apertures or slits that coUItl allow the passage of liquid water or wound fluid. Ilowever, an aperture may be present for passage ol the optional reservoir pull-tab described in more detail below. The backing sheet is preferably formed Prone a semipermeable sheet material. That is to say, the backing sheet material is preferably permeable to water vapour, but not permeable to liquid water or wound exudate. I'ref'erably, the backing sheet material is also substantially microorganism-impermeable. Suitable continuous conformable backing sheets will preferably have a moisture vapor transmission rate (MVTR) ot the backing sheet alone of 300 to 5000 g/m2124hrs, preferably 500 to 20()0 g/m2124hrs at 37.5 TIC at 100% to 10% relative humidity dil't'erence. The backing, sheet thickness is pret'erably in the range of 10 to 2() 1000 rnicr<-'meters, more preferably 100 to 500 micrometers.

Suitable polymers for forming the backing sheet include polyurethanes and poly alkoxyalkyl acrylates and methacrylates such as those disclosed in GB-A-1280631.

Preferably, the backing sheet conprises a continuous layer of a high density blocked polyurethane foam that is predominantly closed-cell. A suitable backing sheet material is the polyurethane film available under the Registered 'I'rade Mark ES'I'ANF. 57141;.

Preferably, the backing sheet is substantially inelastic. Preferably, the sheet exhibits an elastic recovery at 5()% strain of less than 90%, preferably less than 75%, more preferably less than 50%. 3()

I'he backing sheet may have any shape, such as circular, oval or rectangular. Preferably, the backing sheet is shaped with at least one line of symmetry, and in certain embodiments the absorbent pad may be oi'i'set along a line <-1 symmetry of the backing sheet. Suitably, the backing sheet is substantially rectangular (including square). For example, the backing sheet may be substantially rectangular and has dimensions of' I'ron1 5 to 25 cm by from 5 to cm, more preferably Prom 10 to 2() crn by from] () to 20 cm.

The adhesive layer should be moisture vapor transmitting and/or patterned to allow passage of water vapor therethroug]l. 'I'he adhesive layer is preferably a continuous moisture vapor transmitting, pressure-sensitive adhesive layer of the type conventionally used for island-type wound dressings, for example, a pressure sensitive adhesive based on acrylatc ester copolymers, polyvinyl ethyl ether and polyurethane as described tor example in GB-A-128()631. 'he basis weight ot'the adhesive layer is preferably 2() to 250 g/m2, and more preferably 50 to 150 g/m2. Polyurethane-based pressure sensitive adhesives are pret'erred.

I'he adhesive layer extends outwardly from the absorbent pad to form an adhesive-ccrated margin on the backing sheet around the adhesive island as in a conventional island dressing. Preferably, the wound facing surl:ace of the absorbent island itself' is substantially free ot'the adhesive present on the backing sheet, and more preferably it is substantially Tree of any adhesive.

The absorbent pad or island may comprise any of the layers conventionally used for absorbing wound fluids, serum or blood in the wound healing art, including gauzes, nonwoven fabrics, superabsorhents, hydrogels and mixtures thereof' lret'erably, the absorbent pad comprises a layer of absorbent foam, such as an open celled hydrophilic polyurethane foam prepared in accordance with F,P-A-054 1391, the entire content of which is expressly incorporated herein by references In other embodiments, the absorbent pad may comprise a nonwoven fibrous web, for example a carded web of viscose staple fibers.

I'he basis weight of the absorbent pad may be in the range of 50-SOOg/m2, such as 100- 400g/m2. '1'hc absorbent pad may comprise more than one layer. For example, it may comprise an absorbent layer laminated to a non-adhercot, liquid-permeable wound contacting top sheet. 'I'he uncompressed thickness of the absorbent pad may be in the range of front O.5mm to l()mm, such as Imm to 4mm. In some embodiments, the uncompressed thickness of the pad may be less than 3mm. 'I'hc free (uncompressed) liquid absorbency of the pad measured for physiological saline may for example be in the range -,f'5to30g/gat25 .

Suitably, the absorbent island has at least one dimension greater than 4cm, preferably 5 to lOcm. 'lthe shape ol' the pad likewise may be any shape, such as circular, oval or rectallgular, and may be the same or dil't'erent from the shape of' the backing sheet. The area of the absorbent pad is typically in the range -,t' from 1 cm2 to 20()cm2, more preferably trom 4cm2 to l()()cm2. In certain embodiments, such as saclal dressings, the area of' the absorbent pad is preferably greater than 1 6cm2, more preferably greater than 20cm2. 1()

Suitably, the wound irrigation liquid comprises a sterile saline sohtion, and preferably it consists essentially of' such a solution. 'I'he saline solution may comprise a therapeutic agent, for example selected Irom the group consisting of an antimicrobial agent, a pain relieving agent, a growth factor and mixtures thereof'.

I'he antimicrobial agent may be selected from the group consisting of antiseptics and antibiotics and mixtures thereof: Suitable antibiotics include peptide antimicrobials (e.g. deSensins, Magainill, synthetic derivatives ol' them); antibiotics such as gentamycin, tetracycline, penicillins, terramycins, erythrornycin, bacitracin, neomycin, polymycin B. mopirocin, clindamycin and mixtures thereof: Suitable antiseptics include silver sulfadiazille, chlorhexidine, povidone iodine, triclosan, other silver salts and colloidal silver, sucrali:ate, antimicrobial quatemary ammonium salts and mixtures thereof: Suitably, the antimicrobial agent may be incorporated into thi; the wound irrigation liquid at concentrations of between about 0.1-3()% by weight based on the final weight of the sponge, more suitable Prom about ().5-15% by weight, and preferably from about 1 to about 5% by weight.

I'he pain relieving agent may be selected from the group consisting of an anaesthetic, an analgesic, an antiinflammatory or mixtures thereof'. Suitable anaesthetics include lidocaine or novocaine. Suitable analgesics include non-steroidal anti-inflammatory drugs (NSAll)s). Suitable antiinflammatory agents include steroids such as prostaglandins.

Suitably, the pain relieving agent may he incorporated into the the wound irrigation liquid at concentrations of between about 0.1-30 /O by weight based on the final weight of the sponge, more suitably front about 0.515% by weight, and preferably between about 1-5% by weight.

The growth factor may be selected from the group consisting of platelet derived growth Actor (Pl)(,l'), l'ibroblast growth factor (FCI), trnsf'orrllblg growth factor belt (TC;I;-), epidermal growth factor (l,(il.), vascular enclothclial growth factor (V1iGF) and insulin- like growth lactor (Ibid), and mixtures thereof: Suitably, the growth factor may be incorporated into the wound irrigation liquid at concentrations ot'betweer1 about Ippm to about 1% by weight based on the final weight of the sponge, more suitably from about 1 ()ppm to about 1 00()ppm by weight.

Suitably, the reservoir contains from about lml to about 40ml of the wound irrigation liquid, for example from about 4ml to about 25ml. In any case, there is preferably sul'ficient wound irrigation liquid k, substantially saturate the absorbent pad and thereby ensure easy, pain- f'ree removal of the dressing from the wound after use.

The reservoir is suitably made out of polymer sheet material, which may be shaped and filled by any of the methods conventional in the art. Suitable metl,,ods include injection molding or l'orm-fill-seal packaging, for example vertical form-f'ill-seal packaging with through-liquid impulse sealing. Preterably, the polymer used for the reservoir sheet is conformable but not substantially elastomeric. Suitable polymers include-, but are not limited to: polyolefins such as polyethylene, polypropylene, or ethylene methyl acrylate (EMA); polyesters; polyamides such as nylons; fluoropolymers such as polyvinylidene fluoride (PVI)F) or polytetrafluoroethylene (P'I'FE4,); and mixtures thereof'. The reservoir sheet material is preferably a polyc, lefin film. Preferably, the film has a thickness by weight (ASTM E252-84) of from 10 to 200 micrometers, more preferably from 25 to 100 micrometers.

The term "zone of weakness" refers to a region of the reservoir that releases the liquid from the reservoir when an external force is applied to the reservoir. The zone ol' weakness may, for cxamplc, comprise a score line in the sheet material making up the reservoir. In other embodiments, the zone of weakness may comprise a region of thinned sheet material making up the rcscrvoir. In yet other cmbodiinents, the voile of weakness may comprise a region of' relatively weak sealing between two layers of sheet material making up the reservoir. In yet other embotiimcnts, the zone of weakness may comprise a plug in an outlet of the reservoir that can be cxpcllcd or released by the application of'a force l'rom outsits the dresshlg.

I'he dressing may l'urther comprise a pull tab atLaclled to the %onc of weakness fair applying a l'orce to the zone while the dressing,, is attached to a patient. In other embodiments, the reservoir may be opened by applying a force through the backing S}1CCt to increase the pressure in the reservoir to rupture the zone of weakness. In these embodiments, the wound dressing may further comprise indicia on the backhlg sheet showing where to apply a force to open the reservoir.

In certain embodiments it may be desirable for the irrigation liquid to contact the wound bef'orc it is absorbed by the absorbent pad. Accordingly, the wound dressing according to the invention may further comprise a channel or conduit for liquid leading from the reservoir to a wound Lacing surface of the dressing. 'I'he channel or conduit is prei'erably in liquid communication with the:z-,ne of weakness in the reservoir and with the wound facing surface of the dressing',. In certain embodiments, the channel or conduit may extend around the edges of the absorbent pad so that the irrigation liquid bypasses the absorbent pad on its way to the wound surface. This may be achieved, for example, by leaving suitable adhesive-free regions extending down the sides of the absorbent pad. In other embodiments, the absorbent pad may be enclosed in an envelope having liquid-impermeabl hack and sides and a liquidpermeable front (wound facing) surface, so that the saline from the reservoir flows around the pad onto the wound surface bel'ore being, reabsorbed into the pad. In yet other embodiments, the channel or conduit may comprise a tube extending from the reservoir, and suitably the channel or conduit may then be formed integrally with the reservoirIn these embodiments, the zone of weakness may comprise a plug or pinch or score line in the channel that can be ruptured by applying pressure to the reservoir through the backing sheet. . For example, the channel or conduit could be in the form shown in IJS-A-2489675 (the entire content of which is incorporated herein by ret'ercnce).

In use, the irrigation liquid passes down the channel or conduit onto the surface of the wound, and is then reabsorbed back into the absorbent pad thereby irrigating and cleaning the wound.

I'he wound dressing according to the present invention optionally further comprises a liquid-permeable wound lacing top sheet over the absorbent pad. 'I'he top sheet may be any medically acceptable wound ['acing sheet, including woven and nonwoven textile materials. In certain embodiments, the wound tracing top sheet comprises a layer ot' absorbent team, such as an open celled hydrophilic polyurethane foam prepared in accordance with 1*,1'-1-0541391, the entire content of' which is expressly incorporated herein by reference.

In other embodiments, the wound facing top sheet comprises an apertured thermoplastic film. 'I'he top sheet film may be formed from a thermoplastic t'ilm-t'orming polymer.

Preferably, the polymer is conformable but not substantially elastomeric. Suitable polymers include, but are not limited to: polyolef'ins such as polyethylene, polypropylene, or ethylene methyl acrylate (EMA); polyesters; polyamides such as nylons; fluoropolymers such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (P'I'F12); and mixtures thereof'. The top sheet is preferably a polyolefin film. Preferably, the l'ilm has a thickness by weight (AS'I'M 1-,252-84) ol' from 10 to 200 micrometers, more preferably t'rom 25 to I 00 micrometers.

In certain embodiments, the top sheet of the wound dressing according to the invention is liquid permeable, but acts to block or restrict the flow ol'liquid from the back surface to the wound site. That is to say, the top sheet allows fluid to pass through the top sheet from the wound site, but blocks or restricts flow of the fluid back through the top sheet onto the wound (also known as wet-back). Such non-wetting or top sheets may t'or example be made from porous non-woven l:abrics comprising a layer of hydrophobic fibers, or having a hydrophobic finish applied to at least the outer surface thereof. In other embodiments, the top sheet is formed from a substantially liquid-impermeable sheet material provided with tapered capillaries, each capillary having a base substantially in the plane of' the wound facing surface of the top sheet and an apical opening remote from the wound facing surface ol' the top sheet and preferably in contact with an absorbent layer. 'I'he conical capillaries provide rapid one-way wicking of fluid from the front of' the top sheet, with minimal wet-hack. Top sheets of this type are described in GB-/- 152677X.

In yet other suitable embodiments the wound facing top sheet comprises an apertured fihn ot' water-hlsoluble hytlrogel material. For example, the apertured sheet may be a self: supporting sheet ol' such a hydrogel material as described in WO()3/011352, the entire content ol'whicl1 are incorporated herein by reference. 1()

l or the cmbotliments wherein the wound facing top sheet comprises an apertured film, the apertures typically make up from about 0.1% to about 50% of the area Blithe film, more typically from about 1% to about 30% of the area of' the apertured film, and prel'erably from about 10% to about 25% of the area of the apertured film. 'I'ypieally, the apertured IS film has from about I to about 30 apertures per square cm, for example from about 4 to about 15 apertures per square cm or from about 5 to about 10 apertures per square cm. In certain embodiments the apertures are uniformly distributed over the surface of the film, preferably in a regular pattern. The mean area of each aperture may t'or example be from about O.Ol to about 10 mm2, preferably from about O.l to about 4 mm2, and more preferably from about Imm2 to about 2mm2. In certain embodiments, the apertures have a ratio ol'maximum length to maximum width of' from about I to about 10, preferably from about I to about 3, and more preferably from about l to about 1.5. Suitable aperture shapes include round, oval or regular polygonal The wound facing top sheet may also consist of; or comprise, or be occlusively coated by, a composition that is soluble in a component of wound exudate, whereby the permeability of the wound facing sheet is dependent on the amount and/or the composition of wound exudate. for example, the composition may be soluble in water to provide increased absorption rates l'or highly exuding wounds, as described in GB--2379392. The composition may be soluble in the presence of enzymes that are markers for wound chronicity, such as protease enzymes, as described in W003/047643. The composition may be soluble in the presence of enzymes that are markers t'or wound infection, such as Iysozymc, as described in WO2()04/024196. The composition may be soluble in the presence of cnz.ymes that are markers for pain, or other wound conditions. The contents of all of'thc above applications arc hereby incorporated by reference.

he wound lacing top sheet may be bonded to the backing sheet around or behind the absorbent pad, and/or it may be bonded to the absorbent pad by any suitable means, including adhesive bonciing, melt bonding, needling, or entanglement.

In these embodiments, a channel or conduit suitably leads l'rom the reservoir to the wound facing surface ol'thc top sheet. 'I'he top sheet prevents the liquid t'rom being reabsorbed by 1() the absorbcut pad too quickly, bet'ore it has properly irrigated the wound.

The dressings according to the present invention can be used in similar fashion to conventional island dressings, but they have the added advantage that the reservoir can be used to irrigate the wound in situ, without removing the dressing. This provides for quick, easy and mcsslree wound irrigation under sterile conditions. In addition, once the absorbent pad is soaked with the irrigation liquid, it is easier to remove the dressing because the absorbent pad is less adherent to the wound surface.

I'rel'erably, the adhesive dressings according to the invention further comprise at least one relcasc-coated cover sheet covering the absorbent pad and the adhesive-coated margin.

More prel'erably, the dressings comprise two edge cover sheets covering opposed edges of the dressing and a central cover sheet extending between the edge cover sheets, preferably substantially as described in E13-A0117632, the entire content of which is incorporated herein by reference.

I'he wound dressing according to the present invention usually is sterile, and may be packaged in a microorganism-impermeable container.

I'he wound dressings according to the present invention may be used in a method of' treatment of a wound in a living animal or human comprising, the steps of'. applying a dressing according to the invention to the wound in need of treatment, followed by releasing the irrigation liquid Prom the reservoir to irrigate the wound. Suitably, the step of releasing is performed lifter the dressing has been applied to the wound for a suitable treatment period, for example at least I hour or at least 6 hours. Suitably, the step of releasing is followed by a step ot'removing the dressing e.g. once a substantial part of the irrigation liquid has been reabsorbed by the absorbent pad.

Specific embodiments of the present invention will now be described further, by way ol' example, with rclerence to the accompanying drawings, in which: I;ig. I shows a sectional schematic view ol' a wound dressing according to a first embodiment ol'tlle present invention; I'ig.2 shows shows a sectional schematic view of' a wound dressing according to a second cmboclimcnt of the present invention; and Fig.3 shows shows a sectional schematic view ol' the wound dressing of Fig.2 during release ol'the irrigation liquid l'rom the reservoir.

Refenring to l'ig. I, the backing sheet I is Donned from a microporous polyurethane sponge film ol' the kind conventionally used to provide a breathable but microorganism- imperrneable backing to island wound dressings. The backing sheet I is rectangular with rounded corners. 'I'he dimensions are approximately 150 mm by 150 mm, which makes the dressing suitable for protection of a human sacral region.

lower surface ol' the backing sheet I is coated with a layer 2 of a medical grade pressure- sensitive adhesive. An absorbent pad 3 ol hydrophilic nonwoven textile fabric is located centrally on tile wound lacing side of' the backing sheet 1. A perforated thermoplastic top sheet 4 covers the absorbent pad 3. The edges 5 of the top sheet are folded back along the edges of the absorbent pad 3 and adhere to the adhesive layers 2, thereby retaining the top sheet 4 and absorbent pad 2 in place centrally on the backing sheet 1. The adhesive-coated margin around the absorbent pad has an average width of about 20-50 mm.

The dressing further comprises a reservoir 6 filled with a sterile saline solution 9. The reservoir 6 is in the forth of an envelope of' thermoplastic sheet material formed and filled by injection molding, or by f'onn-fill-seal equipment (for example vertical t'orm-fill-seal with through-liquid impulse sealing). tear strip 7 is Donned in the wall of the reservoir 6, and a pull thread 8 extends along the tear strip and through the backing sheet 1 so that the end of'the pull thread 8 can be grasped and pulled to open the reservoir while the dressing is attached to a patient. The dressing may further comprise passages or adhesive-free channels (not shown) extending along the edges of the absorbent pad 3 and providing conduits t'or the passage ol' the sterile solution around the absorbent pad to the wound surface, from where it is then drawn back into the absorbent pad.

I'he island and the adhesive-coated margin are covered by a releasecoated cover sheet I ().

Referring to Trigs. 2 and 3, the general construction of this embodiment is similar to that ot' the embodiment of Iig.l. IIowever, the reservoir 12 hi this embodiment comprises an 1() integrally formed conduit 13 extending through the absorbent pad 14 and the top sheet 15.

I'he conduit comprises a collar of' pressure-sensitive, waterproof' adhesive 16 on an inner surface thereof; whereby the conduit is sealed by pinching this collar. In use, the saline can be released through the conduit by applying a gently t'orce to the backing sheet to compress and pressurize the reservoir 12, thereby forcing open the conduit 13 as shown in 1 5 L'ig.3.

I'he above embodiments have been described by way of example only. Many other embodiments falling within the scope of the accompanying claims will be apparent to the skilled reader.

Claims (11)

1. A wound dressing comprising: a liquid-impermeahle backing sheet, a layer of adhesive on the hacking sheet, an absorbent pad applied to the adhesive-coated side of the backing sheet SUC]1 that an adhesive-c<-,ated margin of tile backing sheet extends around the absorbent pad, and a reservoir ol' wound irrigation liquid situated between the absorbent patl and the backing sheet, wherein the reservoir comprises a zone of weakness whereby the irrigation liquid can he released l'rom the reservoir while the wound dressing is attached to a patient.

2. A wound cJrcssing according to claim 1, wherein the wound irrigation liquid comprises a sterile saline solution.

3. A wound dressing according to claim 1 or 2, wherein the wound irrigation liquid comprises a therapeutic agent selected from the group consisting of an antimicrobial agent, a pain relieving agent, a growth factor and mixtures thereof:

4. 1\ wound dressing according to any preceding claim, wherein the reservoir contains Prom about I ml to about 40ml of the wound irrigation liquid.

5. A wound dressing according to any preceding claim, wherein the reservoir is formed from sheet material, and the zone ol' weakness comprises a score line in the sheet material, or a thinned region of the sheet material, or a region of weak sealing between two layers of the sheet material.

6. A wound dressing according to any preceding claim, further comprising a pull tab attached to the reservoir for opening the reservoir at said zone of weakness.

7. A wound dressing according to any preceding claim, further comprising indicia on the backing sheet showing where to apply a force to open the reservoir.

X. A wound dressing according to any preceding claim, further comprising a channel or conduit for liquid leading from the reservoir to a wound facing surl:ace of the dressing.

9. A wound dressing according to claim 8, wherein the dressing further comprises a liquid-permeahle wound facing top sheet, and the channel or conduit leads from the reservoir to the wound lacing surface of the top sheet.

10. wound dressing according to any preceding claim, wherein the absorbent pad is enclosed in an envelope having a substantially liquid- impermeable back surface and a liquid-permcablc front (wound facing) surface.

1()

11. wound dressing according to any preceding claim, which is sterile and packaged in a microorganism-impermeable container.