US20110054423A1 - Wound cleansing apparatus in-situ - Google Patents

Wound cleansing apparatus in-situ Download PDF

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Publication number
US20110054423A1
US20110054423A1 US12/940,788 US94078810A US2011054423A1 US 20110054423 A1 US20110054423 A1 US 20110054423A1 US 94078810 A US94078810 A US 94078810A US 2011054423 A1 US2011054423 A1 US 2011054423A1
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United States
Prior art keywords
wound
fluid
therapy device
cleansing
backing layer
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Abandoned
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US12/940,788
Inventor
Patrick Lewis Blott
Bryan Greener
Edward Yerbury Hartwell
Julian Lee-Webb
Derek Nicolini
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Smith and Nephew PLC
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Smith and Nephew PLC
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Publication date
Priority to GB0325129.5 priority Critical
Priority to GBGB0325129.5A priority patent/GB0325129D0/en
Priority to PCT/GB2004/004549 priority patent/WO2005051461A1/en
Priority to US57587107A priority
Application filed by Smith and Nephew PLC filed Critical Smith and Nephew PLC
Priority to US12/940,788 priority patent/US20110054423A1/en
Publication of US20110054423A1 publication Critical patent/US20110054423A1/en
Application status is Abandoned legal-status Critical

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    • A61M2205/75General characteristics of the apparatus with filters
    • A61M2205/7518General characteristics of the apparatus with filters bacterial
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Abstract

An apparatus for cleansing wounds, in which wound exudate is removed from a wound bed and selectively cleansed and returned to the wound. The cleansing means removes materials deleterious to wound healing, and the cleansed fluid, still containing materials that are beneficial in promoting wound healing, is returned to the wound bed. The associated wound dressing and cleansing means are conformable to the wound, and may have irrigant fluid circulated from a reservoir by a device for moving fluid through a flow path which passes through the dressing and a means for fluid cleansing and back to the dressing.

Description

  • The present invention relates to apparatus and a medical wound dressing for cleansing wounds, and a method of treating wounds using such apparatus.
  • It relates in particular to such an apparatus, wound dressing and method that can be easily applied to a wide variety of, but in particular chronic, wounds, to cleanse them of materials that are deleterious to wound healing, whilst retaining materials that are beneficial in particular to wound healing.
  • Before the present invention, aspirating and/or irrigating apparatus were known, and tended to be used to remove wound exudate during wound therapy. In known forms of such wound therapy, the offtake from the wound, especially when in a highly exuding state, is voided to waste, e.g. to a collection bag.
  • Materials deleterious to wound healing are removed in this way. However, materials that are beneficial in promoting wound healing, such as growth factors, cell matrix components, and other physiologically active components of the exudate from a wound are lost to the site where they can be potentially of most benefit, i.e. the wound bed, when such therapy is applied.
  • Such known forms of wound dressing and aspiration and/or irrigation therapy systems thus often create a wound environment under the dressing that may result in the loss of optimum performance of the body's own tissue healing processes and in slow healing, and/or in weak new tissue growth that does not have a strong three-dimensional structure adhering well to and growing from the wound bed. This is a significant disadvantage, in particular in chronic wounds.
  • It thus would be desirable to provide a system of therapy which
    • a) can remove materials deleterious to wound healing from wound exudate, whilst
    • a) retaining materials that are beneficial in promoting wound healing in contact with the wound bed.
  • Dialysis is a known method of treating bodily fluids such as blood ex vivo, to cleanse them of materials that are deleterious to the body systemically. Removal of such materials by contact with the dialysate is the prime purpose of dialysis, whilst also retaining materials such as blood, cells and proteins. Other materials that may have an additional positive therapeutic action are potentially lost to the system through the dialysis membrane, which is also permeable to them. The balance of such materials in the bodily fluid in recirculation may thus be further depleted.
  • It would be desirable to provide a system of therapy that can remove materials deleterious to wound healing from wound exudate, without substantially diluting materials that are beneficial in promoting wound healing in contact with the wound bed, and which can continuously supply and recirculate such materials to the wound simultaneously.
  • Dialysis for treating bodily fluids is also a systemic therapy, since the treated fluid is returned to within the body. This is in contrast to a topical therapy in which the treated fluid is recycled outside the body, e.g. to a wound.
  • Dialysis also requires large amounts either of bodily fluids, such as blood, or dialysate, and consequently the relevant devices tend not to be portable. Even when in a highly exuding state, chronic wounds produce relatively little fluid to be treated compared with internal bodily systems and relatively little materials that are beneficial in some therapeutic aspect to be retained in the wound and/or its environment.
  • It is an object of the present invention
    • a) to obviate at least some of the abovementioned disadvantages of known aspiration and/or irrigation therapy systems, and
    • b) to provide a system of therapy which can
      • i) remove materials deleterious to wound healing from wound exudate, whilst
      • ii) retaining materials that are beneficial in promoting wound healing in contact with the wound bed.
  • It is a further object of the present invention
    • a) to obviate at least some of the abovementioned disadvantages of known dialysis systems, and
    • b) to provide a system of therapy which can remove materials deleterious to wound healing from wound exudate, whilst retaining materials that are beneficial in promoting wound healing in contact with the wound bed,
    • c) without affecting the body systemically.
  • It is a yet further object of the present invention
    • a) to obviate at least some of the abovementioned disadvantages of known dialysis systems, and
    • b) to provide a system of therapy which can remove materials deleterious to wound healing from wound exudate, whilst retaining materials that are beneficial in promoting wound healing in contact with the wound bed, and
    • c) is portable.
  • Vascular supply to, and circulation in, tissue underlying and surrounding the wound is often compromised. It is a further object of the present invention to provide a system of therapy that retains and supplies therapeutically active amounts of materials that are beneficial in reversing this effect whilst removing deleterious materials, thereby promoting wound healing.
  • Thus, according to a first aspect of the present invention there is provided an apparatus for cleansing wounds, comprising
  • a conformable wound dressing, having
    a backing layer which is capable of forming a relatively fluid-tight seal or closure over a wound and
    characterised in that it also comprises
    • a) a cleansing means for selectively removing materials that are deleterious to wound healing from wound exudate, which means is under the backing layer and sits in the underlying wound in use and
    • b) a moving device for moving fluid through the cleansing means, and
    • c) optionally bleed means for bleeding the cleansing means.
  • The term ‘bleed means for bleeding the cleansing means’ includes any bleed means that is in fluidic communication with the cleansing means.
  • Materials deleterious to wound healing are removed by the cleansing means, and the cleansed fluid remains in and/or is returned to the wound.
  • The fluid thus retains naturally occurring materials in the wound exudate that are potentially beneficial to wound healing in therapeutically active amounts
  • The apparatus for cleansing wounds of this first aspect of the present invention is based on this principle: by moving fluid through the cleansing means, the moving device continually brings materials that are deleterious to wound healing and the cleansing means into mutual dynamic contact, rather than relying on the passive movement of such materials, e.g. by diffusion under a chemical potential gradient in a fluid. Their removal from the wound exudate occurs more rapidly with such fluid movement.
  • There are various embodiments of the apparatus of the first aspect of the present invention for different types of application, including in particular those that are described in detail hereinafter. No matter how different they may be, it is believed that they may be classified into the following functional types, typified by which fluid passes through the cleansing means:
  • 1. A ‘Single-Phase System’
      • In this, the fluid that is moved through the means for fluid cleansing is wound exudate optionally mixed with an irrigant. This passes into, through and out of the cleansing means, e.g. a chamber under the backing layer, and back to the wound bed. Materials deleterious to wound healing pass into and are removed by the means for fluid cleansing before return of the cleansed fluid to the wound bed.
    2. A ‘Multiple-Phase System’
      • In this, the wound exudate remains in the wound, and does not pass into the cleansing means on a macro-scale. The means for fluid cleansing often comprises a chamber containing a second, cleansing fluid, most usually a fluid (dialysate) phase. The latter is separated from the wound exudate by means of a permeable integer, for example often a polymer film, sheet or membrane. The fluid that is moved through the means for fluid cleansing by the device for moving fluid is the cleansing fluid and/or the wound exudate optionally mixed with irrigant.
  • In both single- and multiple-phase systems, it may be appropriate to design and run the device to move fluid through the wound or the cleansing means to operate the system as a ‘circulating system’.
  • In this, the relevant fluid passes through the cleansing means one or more times in only one direction.
  • Alternatively, where appropriate it may be provided in the form of a ‘reversing system’. That is, the relevant fluid passes through the cleansing means at least once in opposing directions.
  • The apparatus of the first aspect of the present invention may however in different types of application be operated both as a circulating system and as a reversing system, in which the relevant fluid passes through the cleansing means at least once in the same and in opposing directions. (See FIG. 2 hereinafter).
  • The type of cleansing means may determine the appropriate design and mode of running the present apparatus.
  • The cleansing means may as desired be operated as a ‘single-pass system’, i.e. the relevant fluid passes through the cleansing means only once.
  • Alternatively, where appropriate it may be provided in the form of a ‘multiple-pass system’, in which the relevant fluid passes through the cleansing means and/or over the wound bed several times.
  • It will be seen that the combination of these parameters create a number of main embodiments of the present invention. In summary, these are:
  • 1. A ‘Single-Phase System’
      • a) as a ‘circulating system’, in which the wound exudate and optionally irrigant passes through the cleansing means one or more times in only one direction (Examples of such a system are shown in FIGS. 2, 4, 8, 9, 11 and 15 hereinafter.), or
      • b) as a ‘reversing system’, i.e. the wound exudate and optionally irrigant passes through the cleansing means at least once in opposing directions. (Examples of such a system are shown in FIGS. 1, 2, 3, 6, 7, 10 and 14 hereinafter.)
      • This type of cleansing may be operated as a
      • i) ‘single-pass system’, i.e. the relevant fluid passes through the cleansing means only once, or
      • ii) as ‘multiple-pass system’, in which the relevant fluid passes through the cleansing means and/or over the wound bed several times.
    2. A ‘Multiple-Phase System’
      • a) as a ‘circulating system’, in which
        • (i) the wound exudate and optionally irrigant and/or
        • (ii) a cleansing fluid
        • each passes through the cleansing means one or more times in only one direction (Examples of such a system are shown in FIGS. 12 and 13 hereinafter.), or
      • b) as a ‘reversing system’, i.e.
        • (i) the wound exudate and optionally irrigant and/or
        • (ii) a cleansing fluid
        • each passes through the cleansing means at least once in opposing directions.
      • This type of cleansing may be operated as a
      • i) ‘single-pass system’, i.e. the relevant fluid passes through the cleansing means only once, or
      • ii) as ‘multiple-pass system’, in which the relevant fluid passes through the cleansing means and/or over the wound bed several times.
      • In such a ‘multiple-phase system’, where both the cleansing fluid and/or the wound exudate optionally mixed with irrigant are moving, the flows may be cocurrent or countercurrent, preferably countercurrent
      • Examples of such circulating systems are shown in:
      • FIGS. 12 a and 13 in which the exudate is static and a cleansing fluid passes through the cleansing means one or more times in only one direction, and
      • FIG. 12 b, in which the exudate and optionally irrigant and a cleansing fluid each pass through the cleansing means one or more times in only one direction, here countercurrent to each other.
  • The general features of the dressing of the present invention will now be described, followed by specific features related to specific cleansing means within the dressing.
  • In all embodiments of the apparatus of this first aspect of the present invention for cleansing wounds, a particular advantage is the tendency of the wound dressing to conform to the shape of the bodily part to which it is applied.
  • The wound dressing comprises a backing layer with a wound-facing face which is capable of forming a relatively fluid-tight seal or closure over a wound.
  • The term ‘relatively fluid-tight seal or closure’ is used herein to indicate one which is fluid- and microbe-impermeable and permits a positive or negative pressure of up to 50% atm., more usually up to 15% atm. to be applied to the wound. The term ‘fluid’ is used herein to include gels, e.g. thick exudate, liquids, e.g. water, and gases, such as air, nitrogen, etc.
  • The shape of the backing layer that is applied may be any that is appropriate to aspirating, irrigating and/or cleansing the wound across the area of the wound.
  • Examples of such include a substantially flat film, sheet or membrane, or a bag, chamber, pouch or other structure of the backing layer, e.g. of polymer film, which can contain the necessary fluids.
  • The backing layer may be a film, sheet or membrane, often with a (generally uniform) thickness of up to 100 micron, preferably up to 50 micron, more preferably up to 25 micron, and of 10 micron minimum thickness.
  • Its largest cross-dimension may be up to 500 mm (for example for large torso wounds), up to 100 mm (for example for axillary and inguinal wounds), and up to 200 mm for limb wounds (for example for chronic wounds, such as venous leg ulcers and diabetic foot ulcers.
  • Desirably the dressing is resiliently deformable, since this may result in increased patient comfort, and lessen the risk of inflammation of a wound.
  • Suitable materials for it include synthetic polymeric materials that do not absorb aqueous fluids, such as
  • polyolefins, such as polyethylene e.g. high-density polyethylene, polypropylene, copolymers thereof, for example with vinyl acetate and polyvinyl alcohol, and mixtures thereof;
    polysiloxanes;
    polyesters, such as polycarbonates;
    polyamides, e.g. 6-6 and 6-10, and
    hydrophobic polyurethanes.
  • They may be hydrophilic, and thus also include hydrophilic polyurethanes.
  • They also include thermoplastic elastomers and elastomer blends, for example copolymers, such as ethyl vinyl acetate, optionally or as necessary blended with high-impact polystyrene.
  • They further include elastomeric polyurethane, particularly polyurethane formed by solution casting.
  • Preferred materials for the present wound dressing include thermoplastic elastomers and curable systems.
  • The backing layer is capable of forming a relatively fluid-tight seal or closure over the wound and/or around the inlet and outlet pipe(s).
  • However, in particular around the periphery of the wound dressing, outside the relatively fluid-tight seal, it is preferably of a material that has a high moisture vapour permeability, to prevent maceration of the skin around the wound. It may also be a switchable material that has a higher moisture vapour permeability when in contact with liquids, e.g. water, blood or wound exudate. This may, e.g. be a material that is used in Smith & Nephew's Allevyn™, IV3000™ and OpSite™ dressings.
  • The periphery of the wound-facing face of the backing layer may bear an adhesive film, for example, to attach it to the skin around the wound.
  • This may, e.g. be a pressure-sensitive adhesive, if that is sufficient to hold the wound dressing in place in a fluid-tight seal around the periphery of the wound-facing face of the wound dressing.
  • Alternatively or additionally, where appropriate a light switchable adhesive could be used to secure the dressing in place to prevent leakage. (A light switchable adhesive is one the adhesion of which is reduced by photocuring. Its use can be beneficial in reducing the trauma of removal of the dressing.)
  • Thus, the backing layer may have a flange or lip extending around the proximal face of the backing layer, of a transparent or translucent material (for which it will be understood that materials that are listed above are amongst those that are suitable).
  • This bears a film of a light switchable adhesive to secure the dressing in place to prevent leakage on its proximal face, and a layer of opaque material on its distal face.
  • To remove the dressing and not cause excessive trauma in removal of the dressing, the layer of opaque material on the distal face of the flange or lip extending around the wound is removed prior to application of radiation of an appropriate wavelength to the flange or lip.
  • If the periphery of the wound dressing, outside the relatively fluid-tight seal, that bears an adhesive film to attach it to the skin around the wound, is of a material that has a high moisture vapour permeability or is a switchable material, then the adhesive film, if continuous, should also have a high or switchable moisture vapour permeability, e.g. be an adhesive such as used in Smith & Nephew's Allevyn™, IV3000™ and OpSite™ dressings.
  • In a number of main embodiments of the present invention (summarised above), irrigant and/or wound exudate is moved in and out of the dressing.
  • This may be done under negative pressure on the dressing. Such a vacuum may be used to hold the wound dressing in place in a fluid-tight seal around the periphery of the wound-facing face of the wound dressing.
  • This removes the need for adhesives and associated trauma to the patient's skin, and the wound dressing may be merely provided with a silicone flange or lip to seal the dressing around the wound.
  • Alternatively, the flow of irrigant and/or wound exudate in and out of the dressing may be under positive pressure, which will tend to act at peripheral points to lift and remove the dressing off the skin around the wound.
  • In such use of the apparatus, it may thus be necessary to provide means for forming and maintaining such a seal or closure over the wound against such positive pressure on the wound, to act at peripheral points for this purpose.
  • Examples of such means include light switchable adhesives, as above, to secure the dressing in place to prevent leakage.
  • Since the adhesion of a light switchable adhesive is reduced by photocuring, thereby reducing the trauma of removal of the dressing, a film of a more aggressive adhesive may be used, e.g. on a flange, as above.
  • Examples of suitable fluid adhesives for use in more extreme conditions where trauma to the patient's skin is tolerable include ones that consist essentially of cyanoacrylate and like tissue adhesives, applied around the edges of the wound and/or the proximal face of the backing layer of the wound dressing, e.g. on a flange or lip.
  • Further suitable examples of such means include adhesive (e.g. with pressure-sensitive adhesive) and non-adhesive, and elastic and non-elastic straps, bands, loops, strips, ties, bandages, e.g. compression bandages, sheets, covers, sleeves, jackets, sheathes, wraps, stockings and hose.
  • The latter include, e.g. elastic tubular hose or elastic tubular stockings that are a compressive fit over a limb wound to apply suitable pressure to it when the therapy is applied in this way.
  • Suitable examples also include inflatable cuffs, sleeves, jackets, trousers, sheathes, wraps, stockings and hose that are a compressive fit over a limb wound to apply suitable pressure to it when the therapy is applied in this way. Such means may each be laid out over the wound dressing to extend beyond the periphery of the backing layer of the wound dressing.
  • As appropriate they may be adhered or otherwise secured to the skin around the wound and/or itself and as appropriate will apply compression (e.g. with elastic bandages, stockings) to a degree that is sufficient to hold the wound dressing in place in a fluid-tight seal around the periphery of the wound,
  • Such means may each be integral with the other components of the dressing, in particular the backing layer.
  • Alternatively, it may be permanently attached or releasably attached to the dressing, in particular the backing layer, with an adhesive film, for example, or these components may be a Velcro™, push snap or twist-lock fit with each other.
  • The means and the dressing may be separate structures, permanently unattached to each other.
  • In a more suitable layout for higher positive pressures on the wound, a stiff flange or lip extends around the periphery of the proximal face of the backing layer of the wound dressing as hereinbefore defined.
  • The flange or lip is concave on its proximal face to define a peripheral channel or conduit.
  • It has a suction outlet that passes through the flange or lip to communicate with the channel or conduit and may be connected to a device for applying a vacuum, such as a pump or a piped supply of vacuum.
  • The backing layer may be integral with or attached, for example by heat-sealing, to the flange or lip extending around its proximal face.
  • To form the relatively fluid-tight seal or closure over a wound that is needed and to prevent passage of irrigant and/or exudate under the periphery of the wound-facing face of the wound dressing, in use of the apparatus, the dressing is set on the skin around the wound.
  • The device then applies a vacuum to the interior of the flange or lip, thus forming and maintaining a seal or closure acting at peripheral points around the wound against the positive pressure on the wound.
  • With all the foregoing means of attachment, and means for forming and maintaining a seal or closure over the wound, against positive or negative pressure on the wound at peripheral points around the wound, the wound dressing sealing periphery is preferably of a generally round shape, such as an ellipse, and in particular circular.
  • As noted above, the cleansing means for selectively removing materials that are deleterious to wound healing from wound exudate, which means is under the backing layer and sits in the underlying wound in use, often comprises a chamber. A permeable integer, e.g. a sheet, film or membrane, forms part of the chamber wall.
  • In single-phase systems, the device to move fluid moves wound exudate in and out of the cleansing means through the permeable integer, either as a ‘circulating system’ or a reversing system.
  • In two-phase systems, the chamber contains a cleansing fluid, most usually a fluid (dialysate) phase. The latter is separated from the wound exudate by means of the permeable integer. The fluid that is moved within the means for fluid cleansing by at least one device for moving fluid is the cleansing fluid. and/or the wound exudate optionally mixed with irrigant.
  • The general features of the cleansing means of the present invention will now be described, followed by specific features related to specific cleansing means within the dressing.
  • The cleansing chamber is a resiliently flexible, e.g. elastomeric, and preferably soft, structure with good conformability to wound shape.
  • It is favourably urged by its own resilience against the backing layer to apply gentle pressure on the wound bed.
  • The cleansing chamber may be integral with the other components of the dressing, in particular the backing layer.
  • Alternatively, it may be permanently attached to them/it, with an adhesive film, for example, or by heat-sealing, e.g. to a flange or lip extending from the proximal face, so as not to disrupt the relatively fluid-tight seal or closure over the wound that is needed.
  • Less usually, the cleansing chamber is releasably attached to the backing layer, with an adhesive film, for example, or these components may be a push, snap or twist-lock fit with each other.
  • The cleansing chamber and the backing layer may be separate structures, permanently unattached to each other.
  • It may be in the form of, or comprise one or more conformable hollow bodies defined by a film, sheet or membrane, such as a bag, cartridge, pouch or other like structure.
  • The film, sheet or membrane, often has a (generally uniform) thickness of up to 1 mm, preferably up to 500 micron, more preferably from 20 micron to 500 micron minimum thickness, and is often resiliently flexible, e.g. elastomeric, and preferably soft.
  • Such a film, sheet or membrane is often integral with the other components of the dressing, in particular the backing layer, or permanently attached to them/it, with an adhesive film, for example, or by heat-sealing, e.g. to a flange.
  • However, when used herein the term ‘chamber’ includes any hollow body or bodies defined by a film, sheet or membrane, and is not limited to a bag, pouch or other like structure.
  • It may be formed of a film, sheet or membrane of a polymeric material is in a more convoluted form.
  • This may be in the form of elongate structures, such as pipes, tubes hollow fibres or filaments or tubules, e.g. in an array with spaces therebetween, running between an inlet and an outlet manifold.
  • The chamber, especially when it is a bag, cartridge, pouch or other like structure in which the cleansing fluid is contained, may suitably fill much or all of the wound space when in use during wound therapy. It may be desired to limit the remaining wound space volume under the backing layer with a filler where this is not the case, or to adjust the volume of the chamber to do so.
  • Where the chamber and the backing layer are separate structures, not directly attached to each other, such a filler may conveniently lie between the chamber and the backing layer to separate the structures, or within the chamber, so that the chamber may lie directly in contact with the wound bed.
  • The filler is favourably a resiliently flexible, e.g. elastomeric, and preferably soft, structure with good conformability to wound sha