U.S. patent application number 12/848817 was filed with the patent office on 2011-04-14 for wound cleansing apparatus in-situ.
Invention is credited to Patrick Blott, Bryan Greener, Edward Hartwell, Julian Lee-Webb, Derek Nicolini.
Application Number | 20110087179 12/848817 |
Document ID | / |
Family ID | 29725505 |
Filed Date | 2011-04-14 |
United States Patent
Application |
20110087179 |
Kind Code |
A2 |
Blott; Patrick ; et
al. |
April 14, 2011 |
WOUND CLEANSING APPARATUS IN-SITU
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.
Inventors: |
Blott; Patrick; (York,
UK) ; Greener; Bryan; (York, UK) ; Hartwell;
Edward; (Hull, UK) ; Lee-Webb; Julian; (York,
UK) ; Nicolini; Derek; (Brough, UK) |
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20100298793 A1 |
November 25, 2010 |
|
|
Family ID: |
29725505 |
Appl. No.: |
12/848817 |
Filed: |
August 2, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10/575871 |
Jan 29, 2007 |
|
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PCT/GB04/04549 |
Oct 28, 2004 |
|
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12848817 |
Aug 2, 2010 |
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Current U.S.
Class: |
604/319 |
Current CPC
Class: |
A61M 2205/075 20130101;
A61M 1/0072 20140204; A61M 27/00 20130101; A61M 1/0068 20140204;
A61M 3/022 20140204; A61F 13/0259 20130101; A61M 3/0229 20130101;
A61F 13/00068 20130101; A61F 13/0213 20130101; A61M 35/30 20190501;
A61M 2205/8206 20130101; A61M 1/0084 20130101; A61M 1/009 20140204;
A61F 13/0206 20130101; A61M 1/0062 20130101; A61F 2013/00357
20130101; A61M 2205/106 20130101; A61M 1/0037 20130101; A61F
13/0216 20130101; A61M 1/0088 20130101; Y10T 29/49826 20150115;
A61M 1/0058 20130101; A61M 2205/7518 20130101; A61M 3/0216
20140204 |
Class at
Publication: |
604/319 |
International
Class: |
A61M 1/00 20060101
A61M001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 28, 2003 |
GB |
0325129.5 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. (canceled)
9. (canceled)
10. (canceled)
11. A wound dressing apparatus, which comprises: a wound dressing
including a backing layer for positioning over a wound area; and a
negative pressure system comprising: a miniature pump for applying
negative pressure to the wound dressing to move wound exudate from
the wound area, the miniature pump being integral with the
dressing; and a pressure control device configured to control or
vary the pressure under the backing layer applied by the pump in
response to a pressure detected underneath the backing layer.
12. The wound dressing apparatus of claim 11, wherein the pump is
adapted to apply negative pressure of up to 114 mmHg.
13. The wound dressing apparatus of claim 11, wherein the pump is
adapted to apply negative pressure of up to 380 mmHg.
14. The wound dressing apparatus of claim 11, wherein the pump
includes a battery for powering the pump, the battery adapted to be
mounted to the backing layer.
15. The wound dressing apparatus of claim 11, wherein the wound
dressing comprises: a film positionable adjacent to the wound area,
an absorbent member positioned adjacent the film, and a top
member.
16. The wound dressing apparatus of claim 11, wherein the micropump
is mounted to the backing layer above the top member.
17. The wound dressing apparatus of claim 15, further comprising an
adhesive film, the adhesive film adapted to secure the wound
dressing in place and to provide a fluid-tight seal between the
wound dressing and the wound area.
18. The wound dressing apparatus of claim 15, further comprising a
chamber including at least one of medicaments, anti-infectives,
anti-inflammatory agents, anti-oxidants, protease inhibitors,
vitamins, ion exchangers, and pH adjusting agents.
19. The wound dressing apparatus of claim 15, wherein the absorbent
member comprises a material selected from the group consisting of
foams, hydrophilic polymeric materials, and hydrophobic
materials.
20. The wound dressing apparatus of claim 15, wherein the absorbent
member includes at least one of medicaments, anti-infectives,
anti-inflammatory agents, anti-oxidants, protease inhibitors,
vitamins, ion exchangers, and pH adjusting agents.
21. The wound dressing apparatus of claim 11, wherein the backing
layer comprises a transparent or translucent material.
22. The wound dressing apparatus of claim 11, wherein the wound
dressing includes a bleed valve adapted to respond to a degree of
pressure in the wound dressing.
23. The wound dressing apparatus of claim 11, wherein the wound
dressing includes a bleed valve adapted to respond to a degree of
exudate build-up in the wound dressing.
24. A wound dressing apparatus, comprising: a wound dressing
including an absorbent member positionable relative to a wound
area, the absorbent member being disposed underneath a backing
layer; and a negative pressure system mounted on the wound
dressing, the negative pressure system including: a miniature pump
for applying negative pressure to the wound area to facilitate
removal of wound exudate from the wound area, the portable pump
being integral with the wound dressing, a pressure control device
configured to control or vary the pressure under the backing layer
applied by the pump in response to a pressure detected underneath
the backing layer.
25. The wound dressing apparatus of claim 24, wherein the pump
includes a battery for powering the pump.
26. An apparatus for the treatment of a wound, comprising: a
backing layer configured to be positioned over at least a portion
of the wound; a porous layer configured to be positioned between
the wound and the backing layer to define a space beneath the
backing layer and an upper surface of the porous layer; a filter
configured to retain wound exudate in the space between the porous
layer and the backing layer; and, a vacuum source for applying
vacuum to the wound to draw wound exudate into the space between
the porous layer and the backing layer.
27. The apparatus of claim 26, wherein the vacuum source is a
pump
28. The apparatus of claim 27, wherein the pump is mounted on the
backing layer.
29. The apparatus of claim 26, wherein the space beneath the
backing layer additionally comprises a resiliently-flexible
filler.
30. The apparatus of claim 29, wherein the filler comprises
foam.
31. The apparatus of claim 30, wherein the foam is a reticulated
polyurethane foam.
32. The apparatus of claim 26, wherein the filter is
hydrophobic.
33. The apparatus of claim 26, wherein the filter comprises a flat
polymeric material.
34. The apparatus of claim 26, wherein the filter comprises a
micropore filter.
35. The apparatus of claim 26, further comprising a conduit for
applying negative pressure from the vacuum source to the backing
layer.
36. The apparatus of claim 26, wherein the backing layer is
flexible.
37. The apparatus of claim 26, wherein the backing layer is
attached to the porous layer.
38. A method of treating a wound comprising: positioning a wound
dressing over the wound, the wound dressing comprising: a backing
layer; a porous layer beneath the backing layer; a
resiliently-flexible filler located in a space between the backing
layer and the porous layer; and a filter configured to retain wound
exudate in the space between the backing layer and the porous
layer; sealing the wound dressing over the wound; and applying
negative pressure to the wound dressing to draw wound exudate into
the space between the backing layer and the porous layer.
39. The method of claim 38, wherein the resiliently-flexible filler
is a foam configured to sequester wound exudate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/575,871, published as US 2007/0167926 and
filed on Jan. 29, 2007, which is a U.S. National Phase of the PCT
International Application No. PCT/GB04/04549, filed on Oct. 28,
2004, which claims priority to application GB 0325129.5, filed on
Oct. 28, 2003.
FIELD OF THE INVENTION
[0002] The present invention relates to apparatus and a medical
wound dressing for cleansing wounds, and a method of treating
wounds using such apparatus.
[0003] 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.
BACKGROUND OF THE INVENTION
[0004] 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.
[0005] 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.
[0006] 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.
[0007] It thus would be desirable to provide a system of therapy
which [0008] a) can remove materials deleterious to wound healing
from wound exudate, whilst [0009] a) retaining materials that are
beneficial in promoting wound healing in contact with the wound
bed.
[0010] 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.
SUMMARY OF THE INVENTION
[0011] 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.
[0012] 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.
[0013] 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.
[0014] It is an object of the present invention [0015] a) to
obviate at least some of the abovementioned disadvantages of known
aspiration and/or irrigation therapy systems, and [0016] b) to
provide a system of therapy which can [0017] i) remove materials
deleterious to wound healing from wound exudate, whilst [0018] ii)
retaining materials that are beneficial in promoting wound healing
in contact with the wound bed.
[0019] It is a further object of the present invention [0020] a) to
obviate at least some of the abovementioned disadvantages of known
dialysis systems, and [0021] 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, [0022] c)
without affecting the body systemically.
[0023] It is a yet further object of the present invention [0024]
a) to obviate at least some of the abovementioned disadvantages of
known dialysis systems, and [0025] 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
[0026] c) is portable.
[0027] 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.
[0028] 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
[0029] 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
[0030] b) a moving device for moving fluid through the cleansing
means, and [0031] c) optionally bleed means for bleeding the
cleansing means.
[0032] The term `bleed means for bleeding the cleansing means`
includes any bleed means that is in fluidic communication with the
cleansing means.
[0033] Materials deleterious to wound healing are removed by the
cleansing means, and the cleansed fluid remains in and/or is
returned to the wound.
[0034] The fluid thus retains naturally occurring materials in the
wound exudate that are potentially beneficial to wound healing in
therapeutically active amounts
[0035] 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.
[0036] 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:
[0037] 1. A `single-phase system` [0038] 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.
[0039] 2. A `multiple-phase system` [0040] 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.
[0041] 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`.
[0042] In this, the relevant fluid passes through the cleansing
means one or more times in only one direction.
[0043] 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.
[0044] 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).
[0045] The type of cleansing means may determine the appropriate
design and mode of running the present apparatus.
[0046] 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.
[0047] 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.
[0048] It will be seen that the combination of these parameters
create a number of main embodiments of the present invention. In
summary, these are:
[0049] 1. A `single-phase system` [0050] 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 [0051] 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.) [0052]
This type of cleansing may be operated as a [0053] i) `single-pass
system`, i.e. the relevant fluid passes through the cleansing means
only once, or [0054] ii) as `multiple-pass system`, in which the
relevant fluid passes through the cleansing means and/or over the
wound bed several times.
[0055] 2. A `multiple-phase system` [0056] a) as a `circulating
system`, in which [0057] (i) the wound exudate and optionally
irrigant and/or [0058] (ii) a cleansing fluid [0059] 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 [0060] b) as a `reversing system`, i.e. [0061]
(i) the wound exudate and optionally irrigant and/or [0062] (ii) a
cleansing fluid [0063] each passes through the cleansing means at
least once in opposing directions. [0064] This type of cleansing
may be operated as a [0065] i) `single-pass system`, i.e. the
relevant fluid passes through the cleansing means only once, or
[0066] ii) as `multiple-pass system`, in which the relevant fluid
passes through the cleansing means and/or over the wound bed
several times. [0067] 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. [0068] Examples of such circulating
systems are shown in: [0069] FIGS. 12a 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 [0070] FIG. 12b, 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.
[0071] 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.
[0072] 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.
[0073] 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.
[0074] 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.
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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.
[0079] Desirably the dressing is resiliently deformable, since this
may result in increased patient comfort, and lessen the risk of
inflammation of a wound.
[0080] 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.
[0081] They may be hydrophilic, and thus also include hydrophilic
polyurethanes.
[0082] 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.
[0083] They further include elastomeric polyurethane, particularly
polyurethane formed by solution casting.
[0084] Preferred materials for the present wound dressing include
thermoplastic elastomers and curable systems.
[0085] 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).
[0086] 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.TM., IV3000.TM. and OpSite.TM. dressings.
[0087] 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.
[0088] 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.
[0089] 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.)
[0090] 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).
[0091] 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.
[0092] 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.
[0093] 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.TM., IV3000.TM. and OpSite.TM.
dressings.
[0094] 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.
[0095] 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.
[0096] 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.
[0097] 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.
[0098] 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.
[0099] Examples of such means include light switchable adhesives,
as above, to secure the dressing in place to prevent leakage.
[0100] 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.
[0101] 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.
[0102] 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.
[0103] 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.
[0104] 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.
[0105] 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,
[0106] Such means may each be integral with the other components of
the dressing, in particular the backing layer.
[0107] 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.TM., push snap or twist-lock fit with each other.
[0108] The means and the dressing may be separate structures,
permanently unattached to each other.
[0109] 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.
[0110] The flange or lip is concave on its proximal face to define
a peripheral channel or conduit.
[0111] 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.
[0112] The backing layer may be integral with or attached, for
example by heat-sealing, to the flange or lip extending around its
proximal face.
[0113] 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.
[0114] 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.
[0115] 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.
[0116] 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.
[0117] 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.
[0118] 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.
[0119] 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.
[0120] The cleansing chamber is a resiliently flexible, e.g.
elastomeric, and preferably soft, structure with good
conformability to wound shape.
[0121] It is favourably urged by its own resilience against the
backing layer to apply gentle pressure on the wound bed.
[0122] The cleansing chamber may be integral with the other
components of the dressing, in particular the backing layer.
[0123] 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.
[0124] 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.
[0125] The cleansing chamber and the backing layer may be separate
structures, permanently unattached to each other.
[0126] 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.
[0127] 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.
[0128] 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.
[0129] 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.
[0130] It may be formed of a film, sheet or membrane of a polymeric
material is in a more convoluted form.
[0131] 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.
[0132] 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.
[0133] 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.
[0134] The filler is favourably a resiliently flexible, e.g.
elastomeric, and preferably soft, structure with good
conformability to wound shape. The chamber may be urged by its own
resilience and that of the filler to apply gentle pressure on the
wound bed.
[0135] Examples of suitable forms of such wound fillers include
foams formed of a suitable material, e.g. a resilient
thermoplastic. Preferred materials for the present wound dressing
include reticulated filtration polyurethane foams with small
apertures or pores. (Examples of such a filler are shown in FIGS.
7, 10, 11 and 13 hereinafter.)
[0136] Alternatively or additionally, 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, pouch or other structure, filled
with a fluid or solid that urges it to the wound shape.
[0137] Examples of suitable fluids contained in the hollow body or
bodies defined by a film, sheet or membrane include gases, such as
air, nitrogen and argon, more usually air, at a small positive
pressure above atmospheric; and liquids, such as water, saline.
[0138] Examples also include gels, such as silicone gels, e.g.
CaviCare.TM. gel, or preferably cellulosic gels, for example
hydrophilic cross-linked cellulosic gels, such as Intrasite.TM.
cross-linked materials. Examples also include aerosol foams, where
the gaseous phase of the aerosol system is air or an inert gas,
such as nitrogen or argon, more usually air, at a small positive
pressure above atmospheric; and solid particulates, such as
plastics crumbs.
[0139] Such a filler may be inflatable and deflatable with the
fluid, such as a gas, e.g. air or nitrogen, or a liquid, such as
water or saline, to apply varying pressure to the chamber and wound
space if provided with one or more inlet and/or outlet pipes.
[0140] Of course, if the backing layer is a sufficiently
conformable and/or e.g. a downwardly dished sheet, the backing
layer may lie under the wound filler, rather than vice versa. FIG.
6 shows such a resiliently flexible, balloon filler, which is
inflatable and deflatable with a fluid, defined by the backing
layer and a rigid polymer dome that is impermeable and permanently
attached to the distal face of the backing layer
[0141] In this type of layout, in order for the wound filler to
urge the wound dressing towards the wound bed, it will usually have
to be firmly adhered or otherwise releasably attached to the skin
around the wound. This is especially the case in those embodiments
where the wound filler and the backing layer are separate
structures, permanently unattached to each other. FIG. 7 shows a
variant of the apparatus with such a resiliently flexible balloon
filler above the backing layer.
[0142] The specific nature of the chamber will depend largely on
the type of cleansing means that is employed.
[0143] The apparatus of the invention for aspirating, irrigating
and/or cleansing wounds is provided with means for fluid cleansing,
which may be [0144] a) a single-phase system, such as an
ultrafiltration unit, or a chemical adsorption unit; or [0145] b) a
two-phase system, such as a dialysis unit.
[0146] In the former, fluid from the wound passes through a single
flow path in which materials deleterious to wound healing are
removed and the cleansed fluid, still containing materials that are
beneficial in promoting wound healing is returned to the wound.
[0147] Examples of such systems are shown in FIGS. 1 and 2
hereinafter.
[0148] The means for fluid cleansing in such a system may include a
macro- or microfiltration unit, which appropriately comprises one
or more macroscopic and/or microscopic filters. These are to retain
particulates, e.g. cell debris and micro-organisms, allowing
proteins and nutrients to pass through.
[0149] The membrane may preferably be of a hydrophilic polymeric
material, such as a cellulose acetate--nitrate mixture,
polyvinylidene chloride, and, for example hydrophilic
polyurethane.
[0150] Examples of less preferred materials include hydrophobic
materials also including polyesters, such as polycarbonates, PTFE,
and polyamides, e.g. 6-6 and 6-10, and hydrophobic polyurethanes,
and quartz and glass fibre.
[0151] It has microapertures or micropores, the maximum
cross-dimension of which will largely depend on the species that
are to be selectively removed in this way and those to which it is
to be permeable.
[0152] The former may be removed with microapertures or micropores,
e.g. typically with a maximum cross-dimension in the range of 20 to
700 micron, e.g. 20 to 50 nm (for example for undesired proteins),
50 to 100 nm, 100 to 250 nm, 250 to 500 nm and 500 to 700 nm.
[0153] Alternatively, this part of a means for wound exudate
cleansing may be essentially a stack of such filters connected in
series with decreasing cross-dimension of the apertures or pores in
the direction of the fluid flow.
[0154] It may include an ultrafiltration unit, which appropriately
comprises one or more ultrafiltration filters, such as one in which
the cleansing integer is a filter for materials deleterious to
wound healing, for example a high throughput, low protein-binding
polymer film, sheet or membrane which is selectively impermeable to
materials deleterious to wound healing, which are removed and the
cleansed fluid, still containing materials that are beneficial in
promoting wound healing is passed by it.
[0155] The permeable integer in such a system may be a selective
`low pass` system film, sheet or membrane with relatively small
apertures or pores. Suitable materials for the filter include those
organic polymers listed above for macro- and micro-filters.
[0156] It will be appropriate to design and run the apparatus with
this type of cleansing means as a `circulating system`, in which
the relevant fluid passes through the cleansing means one or more
times in only one direction, since this is necessary for retaining
the filter residue out of the wound exudate.
[0157] (It would be inappropriate to run the system in the form of
a `reversing system`, since the fluid passing through the cleansing
means at least once in the reverse direction would return these
materials into the wound.)
[0158] The filter integer may be a flat sheet or membrane of a
polymeric material, or (less usually) in a more convoluted form,
e.g. in the form of elongate structure, such as pipes, tubules,
etc.
[0159] It may be intended that respectively the chamber or the
dressing is disposable. In such case, the device for moving fluid
through the means for wound exudate cleansing is then started and
run until no significant amounts of materials deleterious to wound
healing remain in the wound.
[0160] The dressing and/or the cleansing chamber under the backing
layer is then removed and discarded, to remove the materials
deleterious to wound healing from wound exudate.
[0161] A single-phase system cleansing means may comprise a
chemical adsorption unit, for example one in which a particulate,
such as a zeolite, or a layer, e.g. of a functionalised polymer has
sites on its surface that are capable of removing materials
deleterious to wound healing on passing the fluid from the wound
over them.
[0162] The materials may be removed, e.g. by destroying or binding
the materials that are deleterious to wound healing, by, for
example chelators and/or ion exchangers, and degraders, which may
be enzymes.
[0163] In this type, the chamber wall film, sheet or membrane is
not an integer selectively permeable to materials deleterious to
wound healing. The chamber, however, contains one or more materials
that can remove materials deleterious to wound healing from wound
exudate, by being antagonists to such species.
[0164] For example, where the wound exudate contains
proteases, such as serine proteases, e.g. elastase, and thrombin;
cysteine proteases, matrix metalloproteases, e.g. collagenase; and
carboxyl (acid) proteases;
endotoxins, such as lipopolysaccharides;
inhibitors of angiogenesis such as thrombospondin-1 (TSP-1),
plasminogen activator inhibitor, or angiostatin (plasminogen
fragment);
pro-inflammatory cytokines such as tumour necrosis factor alpha
(TNF.alpha.) and interleukin 1 beta (IL-1.beta.),
oxidants, such as free radicals, e.g., e.g. peroxide and
superoxide; and metal ions, e.g. iron II and iron III; all involved
in oxidative stress on the wound bed, or
basic or acidic species which adversely affect the pH in the wound
exudate, such as protons,
the cleansing chamber may contain, behind the permeable integer at
least one of the following antagonists as appropriate that is
captive in a part of the chamber where it can be in contact with
the irrigant and/or wound exudate:
[0165] protease inhibitors, such as serine protease inhibitors,
such as 4-(2-aminoethyl)-benzene sulphonyl fluoride (AEBSF,
PefaBloc) and N.alpha.-p-tosyl-L-lysine chloromethyl ketone (TLCK)
and .epsilon.-aminocaproyl-p-chlorobenzylamide; cysteine protease
inhibitors; matrix metalloprotease inhibitors; and carboxyl (acid)
protease inhibitors;
binders and/or degraders, such as anti-inflammatory materials to
bind or destroy lipopolysaccharides, e.g. peptidomimetics;
anti-oxidants, such as 3-hydroxytyramine (dopamine), ascorbic acid
(vitamin C), vitamin E and glutathione, and stable derivatives
thereof, and mixtures thereof;
to relieve oxidative stress on the wound bed:
metal ion chelators and/or ion exchangers, such as transition metal
ion chelators, such as iron III chelators (Fe III is involved in
oxidative stress on the wound bed.), such as desferrioxamine (DFO),
3-hydroxytyramine (dopamine);
iron III reductants; or
agents for the adjustment of pH in the wound exudate, such as base
or acid scavengers and/or ion exchangers, or other species, which
may be non-labile, insoluble and/or immobilised) species, such as
ScavengePore.RTM. phenethyl morpholine (Aldrich).
[0166] It will be appropriate to design and run the apparatus with
this type of cleansing means either as a `circulating system`, or
in the form of a `reversing system`, since the fluid passing
through the cleansing means at least once in the reverse direction
would not return these materials into the wound.)
[0167] An example of such systems is shown inter alia in FIGS. 1, 6
and 7 (reversing system) and 2, 8 and 9 (circulating system)
hereinafter.
[0168] A second, selectively permeable integer, again suitably a
flat sheet or membrane of a polymeric material may be required to
form part of a distal chamber wall in the flowpath in any
appropriate part of the apparatus to retain materials that are
deleterious to wound healing and antagonists or other active
materials in the chamber.
[0169] A particular advantage of this form of the system, is that
where a material that can remove materials deleterious to wound
healing from wound exudate is (cyto)toxic or bioincompatible, or
not inert to any components that are beneficial in promoting wound
healing, the system does not allow any significant amounts of it to
pass into the wound.
[0170] 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 a permeable
integer.
[0171] At least one fluid is moved through the means for fluid
cleansing by at least one device, in particular across the
permeable integer, for example the polymer film, sheet or
membrane.
[0172] This promotes the passage of relatively high concentrations
of solutes or disperse phase species, including deleterious
materials, from the wound exudate into the cleansing fluid and the
chamber and optionally the system in which the cleansing fluid
recirculates. Such systems are described further below.
[0173] The fluid that is moved through the means for fluid
cleansing by the device for moving fluid is [0174] a) the cleansing
fluid or [0175] b) the wound exudate optionally mixed with
irrigant, or [0176] c) both.
[0177] Examples of such systems are shown in FIGS. 12 and 13
hereinafter, in which
[0178] FIGS. 12a and 13 show such a system, a dialysis unit, in
which only the cleansing fluid separated from the wound exudate is
the moving fluid.
[0179] FIG. 12b shows such a system, a dialysis unit, in which the
cleansing fluid and the wound exudate optionally with irrigant are
the moving fluids.
[0180] The cleansing fluid is less usually static as in FIG. 4, as
this may not be a system with sufficient (dynamic) surface area to
remove materials deleterious to wound healing from wound exudate at
a practical rate.
[0181] Typical dialysate flow rates in a dialytic means for fluid
cleansing in the present apparatus for aspirating, irrigating
and/or cleansing wounds are those used in the conventional type of
two-phase system, such as a dialysis unit for systemic therapy.
[0182] The integer may be a film, sheet or membrane, often of the
same type, and of the same (generally uniform) thickness, as those
used in conventional two-phase system, such as a dialysis unit for
systemic therapy.
[0183] As noted above, the film, sheet or membrane may be
substantially flat, but, especially where the cleansing fluid
circulates, it may more suitably be in the form of pipes, tubes or
tubules in an array.
[0184] The surface area of any such film, sheet or membrane may be
suitably be no less than 50 mm.sup.2, such 100 to 1000000 mm.sup.2,
e.g. 500 to 25000 mm.sup.2.
[0185] If both fluids move it may be in co- or preferably
counter-current direction.
[0186] Again, materials deleterious to wound healing are removed
into the dialysate, and the cleansed fluid, still containing
materials that are beneficial in promoting wound healing, remains
or is returned by recirculation to the wound.
[0187] Examples of these deleterious materials as above include
oxidants, such as free radicals, e.g. peroxide and superoxide;
iron II and iron III; all involved in oxidative stress on the wound
bed;
proteases, such as serine proteases, e.g. elastase and thrombin;
cysteine proteases, matrix metalloproteases, e.g. collagenase; and
carboxyl (acid) proteases;
endotoxins, such as lipopolysaccharides;
autoinducer signalling molecules, such as homoserine lactone
derivatives, e.g. oxo-alkyl derivatives;
inhibitors of angiogenesis such as thrombospondin-1 (TSP-1),
plasminogen activator inhibitor, or angiostatin (plasminogen
fragment) pro-inflammatory cytokines such as tumour necrosis factor
alpha (TNF.alpha.) and interleukin 1 beta (IL-1.beta.); and
inflammatories, such as lipopolysaccharides, and e.g. histamine;
and
basic or acidic species which adversely affect the pH in the wound
exudate, such as protons.
[0188] Examples of suitable materials for the film, sheet or
membrane (typically in the form of conformable hollow bodies
defined by the film, sheet or membrane, such as the structures
described hereinbefore) include natural and synthetic polymeric
materials.
[0189] The membrane may be of one or more hydrophilic polymeric
materials, such as a cellulose derivative, e.g. regenerated
cellulose, a cellulose mono-, di- or tri-esters, such as cellulose
mono-, di- or tri-acetate, benzyl cellulose and Hemophan, and
mixtures thereof.
[0190] Examples of other materials include hydrophobic materials,
such as aromatic polysulphones, polyethersulphones,
polyetherether-sulphones, polyketones, polyetherketones and
polyetherether-ketones, and sulphonated derivatives thereof, and
mixtures thereof.
[0191] Examples of other materials include hydrophobic materials,
such as polyesters, such as polycarbonates and polyamides, e.g. 6-6
and 6-10; polyacrylates, including, e.g. poly(methyl methacrylate),
polyacrylonitrile and copolymers thereof, for example
acrylonitrile--sodium metallosulphonate copolymers; and
poly(vinylidene chloride).
[0192] Suitable materials for the present membranes include
thermoplastic polyolefins, such as polyethylene e.g. high-density
polyethylene, polypropylene, copolymers thereof, for example with
vinyl acetate and polyvinyl alcohol, and mixtures thereof.
[0193] The dialysis membrane should have a molecular weight cut off
(MWCO) chosen to allow selective perfusion of species deleterious
to wound healing that have been targeted for removal from the
wound. For example, perfusion of the serine protease elastase
(molecular weight 25900 Dalton) would require a membrane with
MWCO>25900 Dalton. The MWCO threshold can be varied to suit each
application between 1 and 3000000 Dalton.
[0194] Preferably, the MWCO should be as close as possible to this
weight to exclude interference by larger competitor species.
[0195] For example, such a membrane with MWCO>25900 Dalton does
not allow any significant amounts of the antagonist to elastase,
alpha-1-antitrypsin (AAT) (molecular weight 54000 Dalton), which
occurs naturally in wounds, to diffuse freely out of the wound
fluid into the dialysate. The inhibitor, which is beneficial in
promoting chronic wound healing, remains in contact with the wound
bed, and can act beneficially on it, whilst the elastase that is
deleterious to wound healing is removed.
[0196] Such use of the present apparatus is, e.g. favourable to the
wound healing process in chronic wounds, such as diabetic foot
ulcers, and especially decubitus pressure ulcers.
[0197] As noted hereinafter, antagonists, for example degrading
enzymes, or sequestrating agents for elastase on the dialysate side
of the membrane, may be used to enhance the removal of this
protease from wound exudate.
[0198] A less conventional type of two-phase system (see above) may
be used as the means for fluid cleansing. In this type, the
dialysis polymer film, sheet or membrane is not an integer
selectively permeable to materials deleterious to wound healing,
such as
proteases, such as serine proteases, e.g. elastase, and thrombin;
cysteine proteases; matrix metalloproteases, e.g. collagenase; and
carboxyl (acid) proteases;
endotoxins, such as lipopolysaccharides;
inhibitors of angiogenesis such as thrombospondin-1 (TSP-1),
plasminogen activator inhibitor, or angiostatin (plasminogen
fragment)
pro-inflammatory cytokines such as tumour necrosis factor alpha
(TNF.alpha.) and interleukin 1 beta (IL-1.beta.);
oxidants, such as free radicals, e.g., e.g. peroxide and
superoxide; and metal ions, e.g. iron II and iron III; all involved
in oxidative stress on the wound bed; and
basic or acidic species which adversely affect the pH in the wound
exudate, such as protons.
[0199] It will however also permit components of the exudate from a
wound and/or irrigant fluid that may be larger or smaller
molecules, but are beneficially involved in wound healing to pass
into and through it.
[0200] In the dialysate, or preferably in one or more solid
structural integers with at least one surface in contact with the
dialysate, in the means for fluid cleansing, there are one or more
materials that can remove materials deleterious to wound healing
from wound exudate, by being
[0201] antagonists to such species, for example enzymes or others,
such as protease inhibitors, such as serine protease inhibitors,
such as 4-(2-aminoethyl)-benzene sulphonyl fluoride (AEBSF,
PefaBloc) and N.alpha.-p-tosyl-L-lysine chloromethyl ketone (TLCK)
and .epsilon.-aminocaproyl-p-chlorobenzylamide; cysteine protease
inhibitors; matrix metalloprotease inhibitors; and carboxyl (acid)
protease inhibitors;
binders and/or degraders, such as anti-inflammatory materials to
bind or destroy lipopolysaccharides, e.g. peptidomimetics;
anti-oxidants, such as 3-hydroxytyramine (dopamine), ascorbic acid
(vitamin C), vitamin E and glutathione, and stable derivatives
thereof, and mixtures thereof;
to relieve oxidative stress on the wound bed;
metal ion chelators and/or ion exchangers, such as transition metal
ion chelators, such as iron III chelators (Fe III is involved in
oxidative stress on the wound bed.), such as desferrioxamine (DFO),
3-hydroxytyramine (dopamine);
iron III reductants; and
agents for the adjustment of pH in the wound exudate, such as base
or acid scavengers and/or ion exchangers, or other species, which
may be non-labile, insoluble and/or immobilised) species, such as
ScavengePore.RTM. phenethyl morpholine (Aldrich).
[0202] They further include peptides (including cytokines, e.g.
bacterial cytokines, such as .alpha.-amino-.gamma.-butyrolactone
and L-homocarnosine); and
sacrificial redox materials that are potentially or actually
beneficial in promoting wound healing, such as iron III reductants;
and/or regeneratable materials of this type, such as glutathione
redox systems; and
other physiologically active components.
[0203] In use of the two-phase system dialysis unit, of this less
conventional type, a broad spectrum of species will usually pass
into the dialysate from the exudate.
[0204] Some (mainly ionic) species will pass from the dialysate
into the irrigant and/or wound exudate through the dialysis polymer
film, sheet or membrane that is not very selectively permeable to
materials deleterious to wound healing.
[0205] The components of the exudate from a wound and/or irrigant
fluid will diffuse freely to and fro through it.
[0206] A steady state concentration equilibrium is eventually set
up between the dialysate and the irrigant and/or wound exudate,
which is `topped up` from the wound dressing.
[0207] Circulating wound fluid aids in the quicker attainment of
this equilibrium of materials beneficial in promoting wound
healing.
[0208] It also returns them to the site where they can be
potentially of most benefit, i.e. the wound bed.
[0209] The target materials deleterious to wound healing also pass
into the dialysate from the exudate through the dialysis polymer
film, sheet or membrane that is not very selectively permeable to
materials deleterious to wound healing.
[0210] Unlike the other components of the exudate from a wound
and/or irrigant fluid, the target materials deleterious to wound
healing come into contact with the dialysate, or preferably with
one or more solid structural integers with at least one surface in
the dialysate, and are removed by the appropriate antagonists,
binders and/or degraders, chelators and/or ion exchangers and redox
agents, etc. The cleansed fluid, still containing some materials
that are beneficial in promoting wound healing, is returned to the
wound.
[0211] Unlike the other components of the exudate from a wound
and/or irrigant fluid the target materials are constantly removed
from the dialysate, very little of these species will pass from the
dialysate into the irrigant and/or wound exudate, and a steady
state concentration equilibrium is not set up, even if the species
are constantly `topped up` from the wound dressing.
[0212] It is believed that circulating one or both fluids aids in
removal from recirculation of the materials deleterious to wound
healing from wound exudate, whilst retaining materials that are
beneficial in promoting wound healing in contact with the
wound.
[0213] A particular advantage of this form of the two-phase system,
is that where a material that can remove materials deleterious to
wound healing from wound exudate is (cyto)toxic or bioincompatible,
or not inert to any components that are beneficial in promoting
wound healing, the system does not allow any significant amounts of
antagonist to diffuse freely out of the dialysate into the wound
fluid. The active material can act beneficially on the fluid
however.
[0214] The film sheet or membrane is preferably a dialysis membrane
of molecular weight cut off (MWCO) (as conventionally defined)
chosen to allow perfusion of species targeted for sequestration or
destruction.
[0215] For example, sequestration of the serine protease elastase
(molecular weight 25900 Dalton) would require a membrane with
MWCO>25900 Dalton.
[0216] The MWCO threshold can be varied to suit each application
between 1 and 3 000 000 Dalton. Preferably, the MWCO should be as
close as possible to this weight to exclude sequestering
interference by larger competitor species.
[0217] It will be seen that in many of the embodiments of the
apparatus of this first aspect of the present invention for
cleansing wounds, the irrigant and/or wound exudate and/or the
cleansing fluid passes from the wound dressing and is returned via
a return path to it, through or under the backing layer with a
wound-facing face which is capable of forming a relatively
fluid-tight seal or closure over a wound.
[0218] Each return path will require
at least one inlet pipe for connection to a fluid return tube,
which passes through the wound-facing face of the backing layer,
and
at least one outlet pipe for connection to a fluid offtake tube,
which passes through the wound-facing face of the backing
layer,
the point at which the or each inlet pipe and the or each outlet
pipe passes through or under the wound-facing face forming a
relatively fluid-tight seal or closure over the wound.
[0219] Where any pipe is described in connection with the operation
of the apparatus as being connected or for connection to a (mating
end of a) tube, the pipe and the tube may form a single
integer.
[0220] Where the mode of running the present apparatus is in the
form of a `reversing system`, the at least one inlet pipe and the
at least one outlet pipe, and the at least one fluid supply tube
and the at least one outlet pipe, may respectively be the same
integer.
[0221] This is often in a `multiple-pass system` for irrigant
and/or wound exudate where this fluid passes from the wound
dressing and is returned to the wound, in both cases via the
cleansing means, e.g. under the action of the movement of a
reciprocating pump, such as a syringe or piston pump.
[0222] The or each inlet pipe or outlet pipe may have the form of
an aperture, such as a funnel, hole, opening, orifice, luer, slot
or port for connection as a female member respectively to a mating
end of a fluid return tube or a fluid offtake tube (optionally or
as necessary via means for forming a tube, pipe or hose, or nozzle,
as a male member.
[0223] Where the components are integral they will usually be made
of the same material (for which it will be understood that
materials that are listed above are amongst those that are
suitable).
[0224] Where, alternatively, they are a push, snap or twist-lock
fit, the may be of the same material or of different materials. In
either case, materials that are listed above are amongst those that
are suitable for all the components.
[0225] The backing layer may often have a rigid and/or resiliently
inflexible or stiff area to resist any substantial play between the
or each pipe and the or each mating tube, or deformation under
pressure in any direction.
[0226] It may often be stiffened, reinforced or otherwise
strengthened by a boss projecting distally (outwardly from the
wound).
[0227] This is usually around each relevant tube, pipe or hose, or
nozzle, hole, opening, orifice, luer, slot or port for connection
to a mating end of a fluid return tube or fluid offtake tube.
[0228] Alternatively or additionally, where appropriate the backing
layer may have a stiff flange or lip extending around the proximal
face of the backing layer to stiffen, reinforce or otherwise
strengthen the backing layer.
[0229] Both the single-phase system, such as an ultrafiltration
unit, and two-phase system, such as a dialysis unit, may be in
modular form that is relatively easily demountable from the
apparatus of the invention.
[0230] Each return flow path (whether in a single-phase system or a
two-phase system, such as an dialysis unit) requires a means for
moving fluid.
[0231] Suitable means will be apparent to the skilled person, but
the following types of small pump may be used as desired:
small reciprocating pumps, such as:
[0232] diaphragm pumps--where pulsations of one or two flexible
diaphragms displace liquid while check valves control the direction
of the fluid flow. [0233] syringe and piston pumps--where pistons
pump fluids optionally through check valves, in particular for
variable and/or reversible positive and/or negative pressure on the
wound bed and for closed single-phase reversing system, in which
the wound exudate and/or irrigant passes to and fro through the
cleansing means. small rotary pumps, such as: [0234] rotary vane
pumps--with rotating vaned disk attached to a drive shaft moving
fluid without pulsation as it spins. The outlet can be restricted
without damaging the pump. [0235] peristaltic pumps--with
peripheral rollers on rotor arms acting on a flexible fluid
circulation tube to urge fluid current flow in the tube in the
direction of the rotor, in particular for a dialysate phase in a
multiple-phase circulating system, in which it passes in only one
direction.
[0236] The type and/or capacity of the device will be largely
determined by the appropriate or desired fluid volume flow rate of
irrigant and/or wound exudate from the wound for optimum
performance of the wound healing process, and by factors such as
portability, power consumption and isolation from
contamination.
[0237] Such a device may also suitably be one that is capable of
pulsed, continuous, variable, reversible and/or automated and/or
programmable fluid movement. It may in particular be a pump of any
of these types.
[0238] The main function of the invention, i.e. an apparatus, that
is advantageously portable, for irrigating and/or cleansing wounds
will largely determine the main function of the pump, i.e. a moving
device for moving fluid, e.g. (chronic) wound exudate, through the
cleansing means, rather than for aspirating or pressurising wounds
that are being cleansed.
[0239] It may however be used to apply a positive or negative
pressure of up to 50% atm., more usually up to 15% atm., to the
wound, which may be pulsed, continuous, variable, reversible,
automated and/or programmable, as for fluid movement.
[0240] A fluid-tight seal or closure of the wound dressing around
the periphery of the backing layer then becomes more crucial, if
wound cleansing is to be applied in this way.
[0241] The device is favourably a small peristaltic pump or
diaphragm pump, e.g. preferably a miniature portable diaphragm or
peristaltic pump. These are preferred types of pump, in order in
particular to reduce or eliminate contact of internal surfaces and
moving parts of the pump with (chronic) wound exudate, and for ease
of cleaning.
[0242] Where the pump is a diaphragm pump, and preferably a small
portable diaphragm pump, the one or two flexible diaphragms that
displace liquid may each be, for example a polymer film, sheet or
membrane, that is connected to means for creating the pulsations.
This may be provided in any form that is convenient, inter alia as
an electromechanical oscillator, a piezoelectric transducer, a core
of a solenoid or a ferromagnetic integer and coil in which the
direction of current flow alternates, a rotary cam and follower,
and so on
[0243] In one embodiment of the apparatus of this first aspect of
the present invention for cleansing wounds with a two-phase system,
such as one with a dialysis unit, no fluid passes from the wound
dressing or is returned via a return path to it, through the
backing layer.
[0244] It therefore does not require any inlet pipe for connection
to a fluid return tube or any outlet pipe for connection to a fluid
offtake tube, which passes through the wound-facing face of the
backing layer.
[0245] In such an embodiment, the prime purpose of the moving
device is to move the cleansing fluid. In such an embodiment,
amongst suitable devices are:
[0246] Suitable examples of such a dressing include, e.g. those
making use of rotary impellers, such as: vane impellers, with
rotating vaned disk attached to a drive shaft, propellers on a
drive shaft, etc.
[0247] Such devices may be integral with the dressing. It will be
seen that the corresponding apparatus disadvantageously has a need
to ensure a fluid-tight seal or closure of the chamber around any
part of the moving device where it passes through the chamber wall
or wound dressing. They may (disadvantageously) not be
portable.
[0248] The possibility of using this type of wound dressing may be
largely determined by the ability to achieve such a relatively
fluid-tight seal or closure. It may be desirable that no part of
the moving device pass through the chamber wall or wound
dressing.
[0249] They may be separate structures, capable of interacting as
appropriate for the purpose of moving cleansing fluid along a
desired flow path across the selectively permeable integer,
effectively in a `multiple-pass system` within the interior of the
chamber.
[0250] The moving device may drive the cleansing fluid inside the
chamber remotely to set it in motion.
[0251] Such an embodiment of the apparatus advantageously enables a
tight seal or closure over the wound, and no part of the moving
device need pass through the chamber wall or wound dressing.
[0252] This avoids the need to ensure a fluid-tight seal or closure
of the chamber around it.
[0253] The chamber may thus, e.g. be provided in a form with at
least one magnetic follower enclosed within it and acted upon by a
magnetic stirrer to impel the cleansing fluid. The magnetic stirrer
to impel the cleansing fluid may be mounted on, e.g. releasably
attached to the other components of the dressing, in particular the
backing layer, e.g. with a Velcro.TM. attachment, an adhesive film
(e.g. of pressure-sensitive adhesive) or elastic or non-elastic
straps, bands, ties, bandages, e.g. compression bandages, sheets or
covers, or be a push, snap or twist-lock fit with it/tem.
[0254] It may be mounted, e.g. centrally, on the backing layer
above a circular or concentric toroidal hollow body that
effectively forms an annular chamber provided with at least one
magnetic follower within it. In use, the magnetic stirrer impels
the magnetic follower enclosed within respectively the circular or
the annular chamber to cause the wound cleansing fluid to
circulate.
[0255] The film, sheet or membrane is often selectively permeable,
contains the cleansing fluid, and should have the right resilience
against the pulsing pressure to allow significant compression or
decompression of the chamber to recirculate the wound cleansing
fluid through it.
[0256] All such remote devices may be integral with or permanently
attached to the dressing, in particular the backing layer, with an
adhesive film, for example, or by heat-sealing.
[0257] These components may be releasably attached, e.g. by a
Velcro.TM. attachment, with an adhesive film (e.g. with
pressure-sensitive adhesive) or with elastic and non-elastic
straps, bands, ties, bandages, e.g. compression bandages, sheets or
covers.
[0258] Another such a device may be provided in the form of at
least one ball or sphere, e.g. a solid metal ball or sphere.
[0259] This sets the cleansing fluid is in motion in contact with
the surface of the integer that is selectively permeable to
materials in the wound exudate under the action of the bodily
movement of the patient.
[0260] Alternatively, the top of a compressible chamber may be
provided with a trackway, around which the patient may run his or
her fingers to move the fluid around the chamber.
[0261] In practice, even from a wound in a highly exuding state,
such a rate of exudate flow is only of the order of up to 75
microlitres/cm.sup.2/hr (where cm.sup.2 refers to the wound area),
and the fluid can be highly mobile (owing to the proteases
present).
[0262] Exudate levels drop and the consistency of wound exudate
changes, e.g. to a higher viscosity liquid, as the wound heals,
e.g. to a level for the same wound that equates to 12.5-25
microlitres/cm.sup.2/hr.
[0263] Where materials deleterious to wound healing are removed by
a two-phase system (See below.), such as a dialysis unit, fluid is
also potentially lost to the system through the means for fluid
cleansing.
[0264] This may occur, e.g. through a dialysis polymer film, sheet
or membrane which is also permeable to water, in addition to
materials deleterious to wound healing.
[0265] The balance of fluid in recirculation may thus further
decrease. It may be desired to adjust the volume of the irrigant
and/or wound exudate and hence to minimise this undesired loss.
[0266] If the consistency of wound exudate changes, e.g. to a
higher viscosity liquid, as the wound heals, it may be desired to
adjust the volume of the irrigant and/or wound exudate and hence to
adjust the viscosity of the liquid, e.g. to a level that equates to
the initial level.
[0267] As noted above, the apparatus of this first aspect of the
present invention for cleansing wounds may be used with the wound
space at atmospheric pressure or at a positive or negative pressure
of up to 50% atm., more usually up to 15% atm. applied to the
wound.
[0268] A fluid may be added to or removed from the wound space
before and/or during wound therapy as may be desired to adjust the
volume of the irrigant and/or wound exudate and/or to adjust the
neutral, positive or negative pressure on the wound.
[0269] Thus, the volume of irrigant and/or wound exudate from the
wound may be increased by continuing addition of irrigant to the
wound space. A positive pressure may be applied to the wound by for
example flooding it with a desired amount of irrigant before the
dressing is applied to it and/or by continuing addition of irrigant
to the wound during the run. A negative pressure may be applied to
the wound by means of fluid removal from the wound, for example
with a small pump.
[0270] This may be achieved in all cases by passage of the relevant
fluid freely to and fro through a fluid regulator, such as a valve
or other control device, e.g. a valve that is turned to switch
between open and closed, that is mounted in a pipe or tube that
passes through or under the backing layer.
[0271] For example, if exudate build-up under the backing layer
becomes excessive during use, a bleed valve may be opened and
excess fluid vented off, e.g. to a waste reservoir, and any excess
pressure relieved.
[0272] Equally, any loss from any fluid from the wound may be
adjusted, or a positive pressure (i.e. above-atmospheric pressure)
may be applied to the wound bed by means of an irrigant which
passes through a similar input regulator, such as a valve or other
control device, e.g. a valve that is turned to switch between on
and off, through or under the backing layer to the wound bed.
[0273] A negative pressure may be conveniently applied to the wound
bed by means of fluid removal from the wound, for example with a
small pump, through a similar vacuum regulator, such as a valve or
other control device, e.g. a valve that is turned to closure once
the vacuum has been applied, before disconnection of the vacuum
source.
[0274] Alternatively or additionally, where appropriate the backing
layer may have a regulator such as an injection septum, through
which the desired amount of the relevant fluid, such as irrigant,
may be removed from or supplied to the wound, for example with a
small syringe or like pump to achieve the desired effect.
[0275] Equally, the balance in any cleansing fluid may be adjusted
by means for bleeding or supplying fluid to the relevant flowpath.
The means for bleeding or supplying fluid to the relevant flowpath
may be situated in any appropriate part of the apparatus that is in
contact with the cleansing fluid.
[0276] The means for bleeding or supplying fluid to the flowpath
may be a regulator, such as a valve or other control device, e.g. a
valve that is turned to switch between bleed and closure, for
bleeding fluids from the apparatus, e.g. to a waste reservoir, such
as a collection bag, or to switch between supply and closure, for
supplying fluids to the apparatus.
[0277] Alternatively or additionally, where appropriate the
flowpath may have a regulator such as an injection septum, through
which the desired amount of the relevant fluid cleanser may be
removed from or supplied to the flowpath, e.g. with a small syringe
or like pump to achieve the desired effect.
[0278] The inlet and/or outlet pipes, the fluid return tube and the
fluid offtake tube, etc. where present may be of conventional type,
e.g. of elliptical or circular cross-section, and may suitably have
a uniform cylindrical bore, channel, conduit or passage throughout
their length.
[0279] Depending on the desired fluid volume flow rate of irrigant
and/or wound exudate from the wound, and the desired amount in
recirculation, suitably the largest cross-dimension of the bore may
be up to 10 mm for large torso wounds, and up to 2 mm for limb
wounds.
[0280] The tube walls should suitably thick enough to withstand any
positive or negative pressure on them.
[0281] This is in particular the case if the volume of irrigant
and/or wound exudate from the wound in recirculation is increased
by continuing addition to it of wound exudate, and/or fluid passing
from a cleansing fluid through a selectively permeable integer, for
example the polymer film, sheet or membrane of a two-phase system,
such as an dialysis unit. However, as noted above with regard to
pumps, the prime purpose of such tubes is to convey irrigant and
exudate through the length of the apparatus flow path, rather than
to act as pressure vessels. The tube walls may suitably be at least
25 micron thick.
[0282] The whole length of the apparatus for aspirating, irrigating
and/or cleansing wounds should be microbe-impermeable once the
wound dressing is over the wound in use.
[0283] It is desirable that the wound dressing and the interior of
the apparatus for aspirating, irrigating and/or cleansing wounds of
the present invention is sterile.
[0284] The fluid may be sterilised in the system in which the fluid
moves, including the means for fluid cleansing, by ultraviolet,
gamma or electron beam irradiation. This way, in particular reduces
or eliminates contact of internal surfaces and the fluid with any
sterilising agent.
[0285] Examples of other methods of sterilisation of the fluid also
include e.g. the use of
ultrafiltration through microapertures or micropores, e.g. of 0.22
to 0.45 micron maximum cross-dimension, to be selectively
impermeable to microbes; and
fluid antiseptics, such as solutions of chemicals, such as
chlorhexidine and povidone iodine; metal ion sources, such as
silver salts, e.g. silver nitrate; and
hydrogen peroxide;
although the latter involve contact of internal surfaces and the
fluid with the sterilising agent.
[0286] It may be desirable that the interior of the wound dressing,
the rest of the system in which the fluid recirculates, and/or the
wound bed, even for a wound in a highly exuding state, are kept
sterile, or that at least naturally occurring microbial growth is
inhibited.
[0287] It is also desirable to provide a system in which
physiologically active components of the exudate that are
beneficial to wound healing are not removed before or after the
application of fluid cleansing, e.g. by the passive deposition of
materials that are beneficial in promoting wound healing, such as
proteins, e.g. growth factors.
[0288] This may occur at any point in the system that is in contact
with such physiologically active components of the exudate that are
beneficial to wound healing.
[0289] Often this will occur at any point in the system that is in
contact with the exudate, usually in a single-phase system, but it
may occur in the second fluid (dialysate) phase in a multiple-phase
system where materials in the wound exudate that are potentially
beneficial to wound healing diffuse freely into that phase in use
of the apparatus.
[0290] The deposition of materials that are beneficial in promoting
wound healing may be combated by using a repellent coating at any
point or on any integer in direct contact with the relevant
fluid.
[0291] Examples of coating materials for surfaces over which the
circulating fluid passes include
anticoagulants, such as heparin, and
high surface tension materials, such as PTFE, and polyamides,
which are useful for growth factors, enzymes and other proteins and
derivatives.
[0292] In all embodiments of the apparatus the type and material of
any tubes throughout the apparatus of the invention for irrigating
and/or cleansing wounds will be largely determined by their
function.
[0293] To be suitable for use, in particular on chronic timescales,
the material should be non-toxic and biocompatible, inert to any
active components, as appropriate of the irrigant and/or wound
exudate and of any dialysate. It should not allow any significant
amounts of extractables to diffuse freely out of it in use of the
apparatus.
[0294] It should be sterilisable by ultraviolet, gamma or electron
beam irradiation and/or with fluid antiseptics, such as solutions
of chemicals, fluid- and microbe-impermeable once in use, and
flexible.
[0295] Examples of suitable materials include synthetic polymeric
materials, such as polyolefins, such as polyethylene, e.g.
high-density polyethylene and polypropylene.
[0296] Suitable materials for the present purpose also include
copolymers thereof, for example with vinyl acetate and mixtures
thereof. Suitable materials for the present purpose further include
medical grade poly(vinyl chloride).
[0297] For the purposes of fluid cleansing in the apparatus of the
present invention, both the single-phase system, such as an
ultrafiltration unit, and two-phase system, such as a dialysis
unit, may have captive (non-labile, insoluble and/or immobilised)
species such as the following, bound to an insoluble and/or
immobilised) substrate over and/or through which the irrigant
and/or wound exudate from, the wound dressing passes in turn to the
fluid return tube(s):
antioxidants and free radical scavengers, such as 3-hydroxytyramine
(dopamine), ascorbic acid (vitamin C), vitamin E and glutathione,
and stable derivatives thereof, and mixtures thereof; to relieve
oxidative stress on the wound bed;
metal ion chelators and/or ion exchangers, such as transition metal
ion chelators, such as iron III chelators (Fe III is involved in
oxidative stress on the wound bed.), such as desferrioxamine (DFO),
3-hydroxytyramine (dopamine);
iron III reductants;
[0298] protease inhibitors, such as TIMPs and alpha 1-antitrypsin
(AAT); serine protease inhibitors, such as 4-(2-aminoethyl)-benzene
sulphonyl fluoride (AEBSF, PefaBloc) and N-.alpha.-p-tosyl-L-lysine
chloro-methyl ketone (TLCK) and
.epsilon.-aminocaproyl-p-chlorobenzylamide; cysteine protease
inhibitors; matrix metalloprotease inhibitors; and carboxyl (acid)
protease inhibitors;
sacrificial redox materials that are potentially or actually
beneficial in promoting wound healing, by the removal of materials
that trigger the expression into wound exudate of redox-sensitive
genes that are deleterious to wound healing;
autoinducer signalling molecule degraders, which may be enzymes;
and
anti-inflammatory materials to bind or destroy lipopolysaccharides,
e.g. peptidomimetics;
agents for the adjustment of pH in the wound exudate, such as base
or acid scavengers and/or ion exchangers, or other species, which
may be non-labile, insoluble and/or immobilised) species, such as
ScavengePore.RTM. phenethyl morpholine (Aldrich).
[0299] Other physiologically active components of the exudate that
are deleterious to wound healing may be removed in this way.
[0300] These may be removed with suitable chelators and/or ion
exchangers, degraders, which may be enzymes, or other species.
[0301] The following types of functionalised substrate has sites on
its surface that are capable of removing materials deleterious to
wound healing on passing the circulating fluid from the wound over
them:
heterogeneous resins, for example silica-supported reagents such
as:
metal scavengers,
3-(diethylenetriamino)propyl-functionalised silica gel
2-(4-(ethylenediamino)benzene)ethyl-functionalised silica gel
3-(mercapto)propyl-functionalised silica gel
3-(1-thioureido)propyl-functionalised silica gel
triamine tetraacetate-functionalised silica gel
or electrophilic scavengers,
4-carboxybutyl-functionalised silica gel
4-ethyl benzenesulfonyl chloride-functionalised silica gel
propionyl chloride-functionalised silica gel
3-(isocyano)propyl-functionalised silica gel
3-(thiocyano)propyl-functionalised silica gel
3-(2-succinic anhydride)propyl-functionalised silica gel
3-(maleimido)propyl-functionalised silica gel
or nucleophilic scavengers,
3-aminopropyl-functionalised silica gel
3-(ethylenediamino)-functionalised silica gel
2-(4-(ethylenediamino)propyl-functionalised silica gel
3-(diethylenetriamino)propyl-functionalised silica gel
4-ethyl-benzenesulfonamide-functionalised silica gel
2-(4-toluenesulfonyl hydrazino)ethyl-functionalised silica gel
3-(mercapto)propyl-functionalised silica gel
dimethylsiloxy-functionalised silica gel
or base or acid scavengers,
3-(dimethylamino)propyl-functionalised silica gel
3-(1,3,4,6,7,8-hexahydro-2H-pyrimido-[1,2-a]pyrimidino)propyl-functional-
ised silica gel
3-(1-imidazol-1-yl)propyl-functionalised silica gel
3-(1-morpholino)propyl-functionalised silica gel
3-(1-piperazino)propyl-functionalised silica gel
3-(1-piperidino)propyl-functionalised silica gel
3-(4,4'-trimethyldipiperidino)propyl-functionalised silica gel
2-(2-pyridyl)ethyl-functionalised silica gel
3-(trimethylammonium)propyl-functionalised silica gel
or the reagents,
3-(1-cyclohexylcarbodiimido)propyl-functionalised silica gel
TEMPO-functionalised silica gel
2-(diphenylphosphino)ethyl-functionalised silica gel
2-(3,4-cyclohexyldiol)propyl-functionalised silica gel
3-(glycidoxy)propyl-functionalised silica gel
2-(3,4-epoxycyclohexyl)propyl-functionalised silica gel
1-(allyl)methyl-functionalised silica gel
4-bromopropyl-functionalised silica gel
4-bromophenyl-functionalised silica gel
3-chloropropyl-functionalised silica gel
4-benzyl chloride-functionalised silica gel
2-(carbomethoxy)propyl-functionalised silica gel
3-(4-nitrobenzamido)propyl-functionalised silica gel
3-(ureido)propyl-functionalised silica gel
or any combinations of the above.
[0302] The use of such captive (non-labile, insoluble and/or
immobilised) species, such as the foregoing, bound to an insoluble
and immobilised) substrate over and/or through which the irrigant
and/or wound exudate from, the wound dressing passes has been
described hereinbefore as suitable for the means for fluid
cleansing.
[0303] However, they may additionally, where appropriate, be used
in any part of the apparatus that is in contact with the irrigant
and/or wound exudate, but often within the dressing, for removal of
materials deleterious to wound healing from wound.
[0304] In a second aspect of the present invention there is
provided a method of treating wounds to promote wound healing using
the apparatus for cleansing wounds of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0305] The present invention will now be described by way of
example only with reference to the accompanying drawings in
which:
[0306] FIGS. 1 to 15 are cross-sectional views of apparatus for
cleansing a wound according to the first aspect of the present
invention.
[0307] FIGS. 1 to 11 and 14 show apparatus with a single-phase
means for wound exudate cleansing, and of these:
[0308] FIGS. 1, 2, 3, 6 7 and 14 show a reversing system, in which
the wound exudate and optionally irrigant passes through the
cleansing means one or more times at least once in opposing
directions; and
[0309] FIGS. 2, 4, 5, 8, 9, 11 and 15 show a circulating system, in
which it/they pass in only one direction; and
[0310] FIGS. 12 and 13 show apparatus with a two-phase means for
wound exudate cleansing, and of these:
[0311] FIGS. 12 and 13 show such apparatus in which the cleansing
phase passes through the cleansing means.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0312] Referring to FIGS. 1 to 10 and 14, the apparatus (1) for
cleansing wounds comprises
a conformable wound dressing (2), having
a backing layer (3) which is capable of forming a relatively
fluid-tight seal or closure over a wound and bears an adhesive
film, to attach it to the skin sufficiently to hold the wound
dressing (2) in place;
a cleansing means (4) for selectively removing materials that are
deleterious to wound healing from wound exudate, which means is
under the backing layer (3) and sits in the underlying wound in
use; and
a moving device (7) for moving fluid through the cleansing
means.
[0313] Optional means for bleeding or supplying fluid to the
cleansing means (4) or to exudate under the backing layer, e.g. a
regulator, such as a valve are omitted in most of the Figures.
[0314] In FIG. 1, a reversing system is shown (wound exudate passes
through the cleansing means at least once in opposing
directions).
[0315] The microbe-impermeable film backing layer (3) bears a
centrally attached proximally projecting recessed boss (11).
[0316] A porous film (12) and a permeable membrane (13) mounted in
the recess (14) of the boss (11) define a cleansing chamber (15),
which contains a solid particulate (not shown) for sequestering
deleterious materials from, but initially separated from the wound
exudate. These integers form the cleansing means (4).
[0317] An annular chamber (16) about the boss (11) is defined by a
fluid-impermeable film (17) that extends between and is attached to
the boss (11) and the underside of the backing layer (3). It is
filled with a flexibly resilient foam (18)
[0318] An inlet and outlet pipe (19) passes centrally through the
boss (11) and communicates between the interior of the boss (11)
and a syringe barrel (20), which is part of a syringe moving device
(7).
[0319] In use, movement of the syringe plunger (22) sucks and
forces wound exudate to and fro through the cleansing means
(4).
[0320] The apparatus (1) in FIG. 2 may be operated as a circulating
system or as both a circulating system and as a reversing
system.
[0321] It is similar in construction to FIG. 1, but differs mainly
in that an inlet pipe return loop (19) passes in a bend through the
boss (11) and communicates between the interior of the chamber (16)
and the syringe barrel (20) via a non-return valve (21), the
resistance of which to flow is low relative to the resistance of
the cleansing means (4). Means for bleeding fluid from the chamber
(16), such as a valve, is omitted from FIG. 2.
[0322] In use, the plunger (22) of the syringe moving device (7) is
withdrawn to suck wound exudate into the cleansing means (4), which
sequesters deleterious materials from the wound exudate.
[0323] The plunger (22) of the syringe moving device (7) is then
returned to force cleansed wound exudate through the valve (21)
into the annular chamber (16), and thence through the porous film
(17) back into the wound.
[0324] A proportion of cleansed wound exudate is also pushed back
through the cleansing means (4) at each return stroke of the
syringe plunger. The proportion will depend largely on the position
of the return loop (19) on the syringe barrel. The amount pumped to
the annular chamber (16) will decrease the further from the
proximal end of the syringe the return loop links to the syringe
barrel, as the plunger cuts off the return loop (19) in the later
part of the return stroke.
[0325] Depending largely on the type of cleansing means that is
employed in this embodiment of the apparatus of the present
invention, the resistance of the valve (21) relative to the
resistance of the cleansing means (4) may also affect the
proportion through the chamber (16) and through the porous film
(17).
[0326] Excess pressure in the chamber (16), e.g. from wound exudate
from a wound in a highly exuding state, may be relieved by a bleed
valve, if fitted.
[0327] The apparatus (1) in FIG. 3 differs mainly from that in FIG.
2 in the position of the porous film (12) in the flow path.
[0328] The mode of use is the same: movement of the syringe plunger
(22) sucks and forces wound exudate to and from through the
cleansing means (4).
[0329] The apparatus (1) in FIG. 4 differs from that in FIG. 2 in
the moving device (7).
[0330] This is a press-button pump in place of a syringe. The pump
(7) is mounted on the distal face of the backing layer (3).
[0331] It comprises a resiliently compressible intake chamber (26),
connected by an outlet pipe (19) to the cleansing means (4) and by
a transfer tube (27) via a low resistance first non-return valve
(31) to a resiliently compressible output chamber (36), connected
via an inlet pipe (20) and a low resistance second non-return valve
(32) to the interior of the chamber (16).
[0332] In use, the intake chamber (26) is manually compressed and
released, its return to its original configuration causing wound
exudate to be drawn through the cleansing means (4).
[0333] The output chamber (36) is then manually compressed and
released, its return to its original configuration causing cleansed
wound exudate to be drawn through the first non-return valve (31)
from the intake chamber (26).
[0334] The intake chamber (26) is then manually compressed again
and released, its compression causing cleansed wound exudate to be
pumped into the output chamber (36) through the first non-return
valve (31) from the intake chamber (26), and its return to its
original configuration causing wound exudate to be drawn through
the cleansing means (4).
[0335] The output chamber (36) is then manually compressed again
and released, its compression causing cleansed wound exudate to be
pumped into the chamber (16) through the second non-return valve
(32) from the output chamber (36), and its return to its original
configuration causing cleansed wound exudate to be drawn through
the intake chamber (26).
[0336] The cycle is repeated as long as desired, and from the
second cycle onwards, when the output chamber (36) is manually
compressed, it causes cleansed wound exudate to be forced through
the annular chamber (16), and thence through the porous film (17)
back into the wound.
[0337] Referring to FIGS. 5 to 7 and 10, the apparatus (1) in each
comprises a cleansing means (4), which comprises a chamber (5),
here a conformable hollow bag, defined by the backing layer (3) and
a polymer film (6) that is permeable and permanently attached to
the proximal face of the backing layer (3).
[0338] It sits under the domed backing layer (3) in the underlying
wound in use, and contains a cleansing fluid absorbed in a
resiliently flexible foam (41).
[0339] FIGS. 5 to 7 and 10 show different methods of moving wound
exudate in and out of the cleansing means (4).
[0340] In FIG. 5, an electromechanical oscillator or piezoelectric
transducer (43) is mounted centrally in contact with the backing
layer (3) on a rigid frame (44) mounted at the periphery of the
backing layer (3), and is connected electrically to an appropriate
alternating electrical power source (45) (shown schematically). The
chamber (5) is provided with a bleed valve (8). If exudate build up
under the backing layer (3) becomes excessive during use, the bleed
valve (8) may be opened and excess fluid vented off, and any excess
pressure relieved.
[0341] In FIG. 6, the foam (41) has a resiliently flexible, balloon
core (47), which is inflatable and deflatable with a fluid, such as
a gas, e.g. air or nitrogen, or a liquid, such as water or saline,
to apply varying pressure to the chamber (5) via an inlet and
outlet pipe (48) mounted at the periphery of the backing layer
(3).
[0342] The pipe (48) is connected to a suitable moving device (58)
(not shown) for moving the inflating fluid in and out of the core
(47) and thus to move wound exudate in and out of the cleansing
means (4). Such a device is suitably one that is capable of
optionally pulsed, reversible fluid movement.
[0343] It may in particular be a small peristaltic pump or
diaphragm pump, e.g. preferably a battery-driven miniature portable
diaphragm or peristaltic pump, e.g. mounted centrally on the
backing layer (3) above the chamber (5) and is releasably attached
to the backing layer (3).
[0344] FIG. 7 shows a variant of the apparatus (1) of FIG. 6. The
resiliently flexible, balloon core (47) under the backing layer (3)
is replaced by a resiliently flexible, balloon chamber (49),
defined by the backing layer (3) and a rigid polymer dome (50) that
is impermeable and permanently attached to the distal face of the
backing layer (3).
[0345] The balloon chamber (49), defined by the backing layer (3)
and the rigid polymer dome (50) is also inflatable and deflatable
with a fluid, such as a gas, e.g. air or nitrogen, or a liquid,
such as water or saline, to apply varying pressure to the chamber
(5) via an inlet and outlet pipe (51) mounted at the periphery of
the backing dome (50).
[0346] A suitable moving device (58) (not shown) is used for moving
the inflating fluid in and out of the balloon chamber (49) and thus
to move wound exudate in and out of the cleansing means (4), as
noted in respect of FIG. 6, and may be mounted on the dome (50)
rather than the backing layer (3).
[0347] In FIG. 10, an electromagnetic solenoid core (53) within an
electrical coil (54) is mounted centrally in contact with the
backing layer (3) on a rigid flange (55). The electrical coil (54)
is connected electrically to an appropriate alternating electrical
power source (60) (shown schematically).
[0348] The chamber (5) is provided at its base with an attached
disc (56) of a ferromagnetic material sheathed from the wound
exudate and cleansing fluid.
[0349] As the direction of current flow alternates, the solenoid
core follows, and so compresses and releases the chamber (5), and
hence causes wound exudate to be forced to and fro through the
cleansing means (4).
[0350] FIGS. 8 and 9 show a variant of the apparatus (1) of FIGS. 1
and 4. The moving device (7) in both cases that respectively
replaces the syringe and the press-button pump is a small
peristaltic pump or diaphragm pump.
[0351] It is preferably a battery-driven miniature portable
diaphragm or peristaltic pump, e.g. mounted centrally on the
backing layer (3) above the chamber (5) and is releasably attached
to the backing layer (3).
[0352] FIG. 11 shows apparatus with a single-phase means for wound
exudate cleansing in which the wound exudate passes through the
cleansing means one or more times in only one direction. It is
similar in structure to the apparatus shown in FIGS. 5 to 7 and
10.
[0353] The apparatus (1) comprises a cleansing means (4), which
comprises a chamber (5), here a conformable hollow bag, defined by
the backing layer (3) and a polymer film (6) that is permeable and
permanently attached to the proximal face of the backing layer (3).
It contains a cleansing fluid absorbed in a resiliently flexible
foam (41).
[0354] The resiliently flexible foam (41) is contained in a
permeable membrane (43) and contains a material for sequestering
deleterious materials from the wound exudate.
[0355] These integers form the cleansing means (4).
[0356] An outlet pipe (69) passes centrally through the backing
layer (3) and communicates between the interior of the chamber (5)
and a pump, e.g. preferably a battery-driven miniature portable
diaphragm or peristaltic pump, e.g. mounted centrally on the
backing layer (3) above the chamber (5) and releasably attached to
the backing layer (3).
[0357] An inlet pipe (20) passes peripherally through the backing
layer (3) and communicates between the wound space and the
pump.
[0358] In use, wound exudate is moved by the pump (7) through the
cleansing means (4), and the foam (41) sequesters deleterious
materials from the wound exudate.
[0359] FIG. 12 shows apparatus with a two-phase means for wound
exudate cleansing in which the cleansing phase moves.
[0360] FIG. 12a shows apparatus in which the only the cleansing
phase moves.
[0361] FIG. 12b shows apparatus in which the cleansing phase and
the wound exudate phase move.
[0362] In both Figures, the apparatus (1) comprises a cleansing
means (4), which comprises a chamber (5), here in the form of
tubules in an array under the backing layer (3) between a first
boss (71) and a second boss (72) both mounted in the backing layer
(3). The tubules are made from a polymer membrane that is
selectively permeable to deleterious materials in the wound
exudate, and contain a dialysate fluid.
[0363] An inlet pipe (20) passes from the first boss (71) and
communicates between the interior of the chamber (5) and a pump
(7), e.g. preferably a battery-driven miniature portable diaphragm
or peristaltic pump, e.g. mounted centrally on the backing layer
(3) above the chamber (5) and releasably attached to the backing
layer (3). An outlet pipe (21) passes from the second boss (72) and
communicates between the interior of the chamber (5) and the pump
(7).
[0364] In use, dialysate fluid is moved by the pump (7) through the
cleansing means (4), and it removes deleterious materials from the
wound exudate.
[0365] In FIG. 12b, a third boss (78) with a wound exudate outlet
passing centrally through it and a fourth boss (79) with a wound
exudate inlet passing centrally through it are both mounted
peripherally and mutually diametrically opposed in the backing
layer (3).
[0366] A wound exudate outlet tube (80) is connected to the third
boss (78) and communicates between the interior of the wound and
the inlet of a second pump (82) (not shown), e.g. preferably a
battery-driven miniature portable diaphragm or peristaltic pump,
mounted centrally on the backing layer (3).
[0367] A wound exudate inlet tube (81) is connected to the fourth
boss (79) and communicates between the interior of the wound and
the outlet of the second pump.
[0368] In use, not only is dialysate fluid moved by the first pump
(7) through the cleansing means (4), where it removes deleterious
materials from the wound exudate, but the wound exudate phase is
moved under the backing layer (3) through the wound space by the
second pump in a counter-current direction to enhance the removal
from the wound exudate.
[0369] FIG. 13 shows apparatus with a two-phase means for wound
exudate cleansing in which the cleansing phase moves.
[0370] The apparatus (1) comprises a cleansing means (4), which
comprises a chamber (5), here in the form of bag under the backing
layer (3) and under a foam filler (81).
[0371] This bag is made from a polymer membrane and contains a
dialysate fluid, which contains a material as a solute or disperse
phase species that is for sequestering or degrading deleterious
materials from the wound exudate. The membrane is chosen to be
selectively permeable to allow perfusion of deleterious material
species targeted for sequestration or destruction from the wound
exudate into the dialysate, but not to allow any significant
amounts of antagonist in the dialysate fluid phase to diffuse
freely out of the dialysate into the wound fluid.
[0372] An outlet pipe (89) passes through the backing layer (3) and
communicates between the interior of the chamber (5) and a pump,
e.g. preferably a battery-driven miniature portable diaphragm or
peristaltic pump, e.g. mounted centrally on the backing layer (3)
above the chamber (5) and releasably attached to the backing layer
(3). An inlet pipe (90) passes peripherally through the backing
layer (3) and communicates between the chamber (5) and the
pump.
[0373] In use, dialysate is moved by the pump (7) through the
cleansing means (4). Deleterious material species targeted for
sequestration or destruction from the wound exudate into the
dialysate, where the antagonist in the dialysate fluid phase
removes deleterious materials from the wound exudate, without
diffusing out into the exudate.
[0374] In FIG. 14, a reversing system is shown (wound exudate
passes through the cleansing means at least once in opposing
directions) that is similar in structure to the apparatus shown in
FIGS. 1 and 3.
[0375] The microbe-impermeable polyurethane film backing layer (3),
formed by solution casting or extrusion, bears a centrally attached
proximally projecting boss (11) with a luer for connection to a
mating end of a fluid supply and offtake tube (19), which
communicates between the interior of the boss (11) and a syringe
barrel (20), which is part of a syringe moving device (7).
[0376] A lower porous film (12) and an intermediate porous membrane
(13), both made of permeable polyurethane membrane with small
apertures or pores, define a cleansing chamber (15), which contains
a solid particulate (not shown).
[0377] This is for sequestering deleterious materials from, but
initially separated from, the wound exudate. These integers, with a
coextensive impermeable upper sheet (24) with an upper aperture
adapted to register with the conduit in the boss (11), form an
upper chamber (25), and all together form the cleansing means (4).
This is mounted on the lower face of the boss (11) with the upper
aperture in register with the conduit in the boss (11).
[0378] In use, movement of the syringe plunger (22) sucks and
forces wound exudate to and fro through the cleansing means
(4).
[0379] The apparatus (1) in FIG. 15 is a circulating system (wound
exudate passes through the cleansing means one or more times in
only one direction). It is a variant of the apparatus (1) of FIGS.
8 and 9.
[0380] The microbe-impermeable polyurethane film backing layer (3),
formed by solution casting, bears a centrally mounted proximally
projecting boss (11) with a uniform cylindrical-bore conduit
through it and a luer for connection to a mating end of a fluid
supply tube (20), which communicates between the interior of the
boss (11) and the outlet of moving device (7).
[0381] The moving device (7) is a battery-driven miniature portable
diaphragm or peristaltic pump, mounted centrally on the backing
layer (3) and is releasably attached to the backing layer (3).
[0382] A second proximally projecting boss (82) with a luer for
connection to a mating end of a fluid offtake tube (83) is mounted
peripherally on the backing layer (3). The fluid offtake tube (83)
communicates between the wound space and the inlet of the pump
(7).
[0383] A lower porous film (12) and an intermediate porous membrane
(13), both made of permeable polyurethane membrane with small
apertures or pores, define a cleansing chamber (15), which contains
a solid particulate (not shown) for sequestering deleterious
materials from, but initially separated from, the wound exudate.
These integers, with a coextensive impermeable upper sheet (24)
with an upper aperture adapted to register with the conduit in the
boss (11), form an upper chamber (25), and all together form the
cleansing means (4). This is mounted on the lower face of the boss
(11) with the upper aperture in register with the conduit in the
boss (11).
[0384] In use, wound exudate is moved by the pump (7) through the
cleansing means (4), and the particulate (not shown) sequesters
deleterious materials from the wound exudate
[0385] The use of the apparatus of the present invention will now
be described by way of example only in the following Examples:
Example 1
Cleansing Fe(II) from Aqueous Solution with the Apparatus of FIG.
1: Single-Phase Hand-Syringe Pumped Dressing Containing Solid
Sequestrant (Cadexomer--Desferrioxamine)
[0386] A hand-syringe pumped dressing as shown in FIG. 14 was made
up. The cleansing chamber (15) contains a solid particulate (not
shown) desferrioxamine supported on Cadexomer (50 mg) to sequester
and remove deleterious Fe(II) ions from surrogate exudate.
[0387] The porous film (12) and a permeable membrane (13), both
made of Porvair permeable membrane, are chosen to allow perfusion
and flow under syringe pumping through the cleanser but to contain
the solid reagent.
[0388] In triplicate, the dressing as shown in FIG. 1 was applied
to a 9.60 ml capacity circular wound cavity (cast in Perspex)
containing an aqueous solution of ferrous chloride tetrahydrate
(Aldrich) (9.60 ml, 200 .mu.molar).
[0389] The solution was repeatedly completely withdrawn and
completely reinjected using the device syringe. At each withdrawal,
a 100 microlitre aliquot of solution was assayed using a ferrozine
assay as follows: each 100 ul aliquot was added immediately to a
1.5 ml capacity, 1 cm path-length UV cuvette containing 1 ml
Ferrozine stock solution (73.93 mg Ferrozine was made up to 250 ml
in distilled water (600 uM)). Absorbance (562 nm) readings were
taken after at least 5 min. incubation. The absorbance was measured
using UNICAM UV4-100 UV-Vis spectrophotometer V3.32 (serial no.
022405).
[0390] Six passes were made in total, at four minute intervals. The
same method was repeated in the absence of flow (i.e. without
syringe pumping through the cleanser) and sampled at equivalent
time points.
RESULTS AND CONCLUSIONS
[0391] The resulting iron concentration profiles were averaged and
the standard deviations were determined. The Fe(II) concentration
is effectively depleted to background level in 3 full cycles (12
minutes). In the control, insignificant concentration change has
occurred in the same time period.
[0392] The dressing as shown in FIG. 1 effectively sequesters
Fe(II) from aqueous solution such as water, saline or wound
exudate.
Example 2
Neutralising the pH of an Acidic Solution with the Apparatus of
FIG. 15: Single-Phase Recirculating Pumped Dressing Containing
Solid Acid Scavenger, ScavengePore.RTM. Phenethyl Morpholine
[0393] A recirculating pumped dressing as shown in FIG. 15 was made
up. The cleansing chamber (15) contains a solid particulate (not
shown) of ScavengePore.RTM. phenethyl morpholine (Aldrich) (50 mg),
which is a low-swelling macroporous highly crosslinked
polystyrene/divinylbenzene ion-exchanger resin matrix, with 200-400
micron particle size, to scavenge and remove protons, which are
acidic species which adversely affect the pH in the wound exudate,
from surrogate exudate.
[0394] The porous film (12) and a permeable membrane (13), both
made of Porvair permeable membrane, are chosen to allow perfusion
and flow under pumping through the cleanser but to contain the
ion-exchange reagent.
[0395] In triplicate, 4.80 ml DMEM was In triplicate, Device 2 was
applied to a 9.60 ml capacity circular wound cavity (cast in
Perspex) containing Dulbecco's Modified Eagles Medium (DMEM)
(Sigma) (4.80 ml, pH adjusted to pH 6.6 using hydrochloric acid
(0.975 N in water, 75 .mu.l). The remaining cavity volume was
filled with glass beads. The solution was circulated through the
cavity at a flow rate of 2.35 ml min.sup.-1.
[0396] 100 .mu.l samples were taken at 5 min. time points up to 40
min, and pH was recorded using a flat-bed pH meter. The same method
was repeated in the absence of flow (i.e. no pump circulation of
the solution) and sampled at equivalent time points.
RESULTS AND CONCLUSIONS
[0397] The resulting pH profiles were averaged and standard
deviations determined. The pH was effectively adjusted to pH 7.4 in
40 min. In the control, a slower change in pH was observed in the
same time period to pH 7.
Example 3
Cleansing Elastase from Aqueous Solution by Diffusion Across a
Dialysis Membrane with the Apparatus of FIG. 12: Two-Phase
Recirculating Pumped Dressing Containing No Reagent
[0398] A recirculating pumped dressing as shown in FIG. 12 was made
up. The cleansing chamber (5) is in the form of tubules made from a
polymer membrane that is selectively permeable to a deleterious
materials in wound exudate (elastase). These in an array under the
backing layer (3) within the wound space between a first boss (71)
and a second boss (72) both mounted in the backing layer (3). The
tubules contain a dialysate fluid and are in a circuit with a pump
(7).
[0399] In triplicate, the dressing as shown in FIG. 12 was applied
to a 9.60 ml capacity circular wound cavity (cast in Perspex)
containing elastase solution (porcine pancreatic elastase, Sigma)
(4.80 ml, 0.5 mgml.sup.-1 in TRIS buffer, pH 8.2, 0.2 M). The
remaining cavity volume was filled with glass beads. The inlet and
outlet ports were connected to the circulating pump.
[0400] The dialysate system was prefilled with TRIS (pH 8.0, 0.2
M). This was circulated through the dressing at a flow rate of 2.35
ml min.sup.-1. 10 .mu.l samples of the circulating solution were
taken at 5 min. time points up to 45 min, and the activity was
recorded using a standard N-succinyl-(ala).sub.3-p-nitroanilide
calorimetric assay. The same method was repeated in the absence of
flow (i.e. no pump circulation of the solution) and sampled at
equivalent time points.
RESULTS AND CONCLUSIONS
[0401] The activity of the samples was determined from their
absorbances at 405 nm using a UV/Vis spectrometer. Results were
averaged and standard deviations determined. Effective transfer of
elastase across the dialysis membrane is seen in 45 min. In the
control, no effective transfer was observed in the same time
period.
Example 4
Cleansing Fe(II) from Aqueous Solution with the Apparatus of FIG.
13: Two-Phase Recirculating Pumped Dressing Containing Liquid Phase
Sequestrant (Starch--Desferrioxamine (DFO) Conjugate)
[0402] An analogue of the apparatus (1) in FIG. 13 was made up,
i.e. with a circulating system (wound exudate passes through the
cleansing means one or more times in only one direction) with a
two-phase means for wound exudate cleansing in which the cleansing
phase moves.
[0403] The apparatus (1) comprises a cleansing means (4), which
comprises a chamber (5) which is made from a polymer membrane and
contains a dialysate fluid, which contains a material as a solute
or disperse phase species that is for sequestering or degrading
deleterious materials from the wound exudate.
[0404] The membrane is chosen to be selectively permeable to allow
perfusion of deleterious material species targeted for
sequestration or destruction from the wound exudate into the
dialysate, but not to allow any significant amounts of antagonist
in the dialysate fluid phase to diffuse freely out of the dialysate
into the wound fluid.
[0405] The analogue is a circuit containing a 0.5-1.0 ml capacity
Slide-A-Lyzer dialysis unit, with an upper chamber and a lower
chamber in which wound exudate and cleansing fluid respectively are
separated from each other by a polymer membrane chosen to have the
properties noted above (MWCO 10000).
[0406] The lower chamber, through which cleansing fluid passes, has
diagonally opposed inlet and outlet ports, which are opened with
needles, connected to a circuit of 5 ml capacity containing a
dialysate reservoir and a battery-driven miniature portable
diaphragm or peristaltic pump. The circuit contains an aqueous high
molecular weight starch--DFO conjugate (5 ml, 4 mg/ml).
[0407] An aliquot of ferrous chloride tetrahydrate (Aldrich)
solution (0.5 ml 3 mM) was placed in the upper cavity of the slide
and dialysed with 3.6 ml/min. flow in the circuit and (as a
control) in the absence of flow in the circuit.
[0408] 10 microlitre aliquots were removed for 30 minutes at 5
minutes intervals (including t=0). The 10 microlitre aliquot of
solution was assayed using the ferrozine iron(II) determination
assay as described in Example 1 above. These experiments were
performed in triplicate.
RESULTS AND CONCLUSIONS
[0409] The resulting iron concentration profiles were averaged and
standard deviations determined. The Fe(II) concentration was
effectively depleted to approximately 50% of the initial level in
30 minutes. Without circuit flow, Fe(II) concentration was depleted
to approximately 75% of the starting value in the same time period.
The apparatus effectively sequesters Fe(II) from aqueous
solution.
* * * * *