Apparatus and method for wound cleansing with actives

Abstract

An apparatus and method for cleansing and applying therapy or prophylaxis to wounds, in which irrigant fluid, which may contain a physiologically active material, and wound exudate from the dressing are moved by a device for moving fluid through a flow path which passes through the dressing. A means for fluid cleansing may also be provided to recirculate fluid back to the dressing. 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 apparatus may also provide means for distributing such materials in a precise and time-controlled manner over the wound bed. It may also contain a means for providing simultaneous aspiration and irrigation of the wound.

Claims

1. An apparatus for aspirating, irrigating and/or cleansing wounds, comprising: a conformable wound dressing having a backing layer configured to form a relatively fluid-tight seal or closure over a wound; a physiologically active agent source configured to connect by a fluid supply tube to the wound dressing, wherein the fluid supply tube is configured to deliver a physiologically active agent comprising oxygen from the physiologically active agent source to the wound; a negative pressure source configured to apply negative pressure to an interior of the wound dressing and to the wound; and wherein the physiologically active agent is configured to be supplied to the wound dressing from the physiologically active agent source via the fluid supply tube while fluid is simultaneously aspirated by the negative pressure source and desired negative pressure is applied to the wound.

2. The apparatus of claim 1, further comprising a wound contact layer.

3. The apparatus of claim 1, wherein the wound contact layer comprises a biodegradable material.

4. The apparatus of claim 3, wherein the biodegradable material comprises a cellulose derivative.

5. The apparatus of claim 1, wherein the physiologically active agent source comprises a reservoir.

6. The apparatus of claim 1, further comprising a controller.

7. The apparatus of claim 6, wherein the controller is configured to control delivery of negative pressure.

8. The apparatus of claim 6, wherein the controller is configured to control delivery of the physiologically active agent.

9. The apparatus of claim 7, wherein negative pressure is delivered continuously.

10. The apparatus of claim 7, wherein negative pressure is delivered intermittently.

11. The apparatus of claim 6, wherein the controller is configured to switch between a first setting where a physiologically active agent is delivered to the wound and a second setting where negative pressure is delivered to the wound.

12. The apparatus of claim 8, wherein the physiologically active agent is delivered in a plurality of supply cycles.

13. The apparatus of claim 6, wherein the controller is configured to control delivery of negative pressure and delivery of the physiologically active agent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will now be described by way of example only with reference to the accompanying drawings in which:

(2) FIGS. 1a and 1b are schematic views of apparatuses for aspirating, irrigating, and/or cleansing a wound. The apparatuses have a single device for moving fluid through the wound applied to the aspirate in the fluid offtake tube downstream of and away from the wound dressing, in combination with means for supply flow regulation, connected to a fluid supply tube, and means for aspirate flow regulation, connected to a fluid offtake tube.

(3) FIG. 1b also has a single-phase system means for fluid cleansing in the form of an ultrafiltration unit. The apparatus may have a single-phase system means for fluid cleansing in the form of a container, e.g. a canister, cartridge or cassette, with a chamber or compartment that contains a cell or tissue component, through which the wound exudate or a mixture with irrigant passes in recirculation.

(4) FIG. 2 is a schematic view of an apparatus for aspirating, irrigating and/or cleansing a wound according to an embodiment of the present invention. It has a two-phase system means for fluid cleansing in the form of a dialysis container, e.g. a canister, cartridge or cassette, with one compartment through which the circulating fluid from the wound and the fluid reservoir passes and is separated by an integer that is permeable to materials in the circulating fluid in the apparatus from a second compartment containing cells or tissue, through which passes a cleansing fluid.

(5) FIG. 3 is a schematic view of another apparatus for aspirating, irrigating and/or cleansing a wound according to an embodiment of the present invention that has a first device for moving fluid through the wound applied to the aspirate in the fluid offtake tube downstream of and away from the wound dressing, with means for aspirate flow regulation, connected to a fluid offtake tube; and a second device for moving fluid through the wound applied to the irrigant in the fluid supply tube upstream of and towards the wound dressing.

(6) FIGS. 4a to 8b are cross-sectional views of conformable wound dressings. In these, FIG. 4a is a cross-sectional plan view of the wound dressing, while FIG. 4b is a cross-sectional side view of the wound dressing. FIG. 5a is a cross-sectional plan view of the wound dressing, while FIG. 5b is a cross-sectional side view of the wound dressing. FIG. 6a is a cross-sectional plan view of the wound dressing, while FIG. 6b is a cross-sectional side view of the wound dressing. FIG. 7a is a cross-sectional plan view of the wound dressing, while FIG. 7b is a cross-sectional side view of the wound dressing. FIG. 8a is a cross-sectional plan view of the wound dressing, while FIG. 8b is a cross-sectional side view of the wound dressing.

(7) FIGS. 9a to 11c are various views of inlet and outlet manifold layouts for the wound dressings for respectively delivering fluid to, and collecting fluid from, the wound. FIGS. 9a-d are various views of inlet and outlet manifold layouts for the wound dressings for respectively delivering fluid to, and collecting fluid from, the wound. FIGS. 10a-b are various views of inlet and outlet manifold layouts for the wound dressings for respectively delivering fluid to, and collecting fluid from, the wound. FIGS. 10a-b are various views of inlet and outlet manifold layouts for the wound dressings for respectively delivering fluid to, and collecting fluid from, the wound. FIGS. 1a-c are various views of inlet and outlet manifold layouts for the wound dressings for respectively delivering fluid to, and collecting fluid from, the wound.

(8) FIG. 12 is a schematic view of an apparatus for aspirating, irrigating and/or cleansing a wound. It has a single-phase system means for fluid cleansing in the form of an ultrafiltration unit. In one embodiment, it has a single-phase system means for fluid cleansing in the form of a container, e.g. a canister, cartridge or cassette, with a chamber or compartment that contains a cell or tissue component, through which the wound exudate or a mixture with irrigant passes.

(9) FIG. 13 is a schematic view of an apparatus for aspirating, irrigating and/or cleansing a wound. It has a two-phase system means for fluid cleansing in the form of a dialysis unit, or a biphasic extraction unit. In one embodiment, it has a two-phase system means for fluid cleansing in the form of a dialysis container, e.g. a canister, cartridge or cassette, with one compartment through which the circulating fluid from the wound and the fluid reservoir passes and is separated by an integer that is permeable to materials in the circulating fluid in the apparatus from a second compartment containing cells or tissue, through which passes a cleansing fluid.

(10) FIGS. 14a to d are variants of a two-pump system with essentially identical, and identically numbered, components as in FIG. 2, except that there is a pump bypass loop (in all except FIG. 14c), a filter downstream of the aspirate collection vessel, and a bleed regulator, such as a rotary valve, connected to the fluid offtake tube or to the wound space, for the regulation of the positive or negative pressure applied to the wound.

(11) FIGS. 15a to c are variants of a two-pump system with essentially identical, and identically numbered, components as in FIG. 14, except that they have various means for varying the regulation of the positive or negative pressure applied to the wound.

(12) FIGS. 16a to 29 are cross-sectional views of conformable wound dressings. In these, FIGS. 16a-b are cross-sectional views of conformable wound dressings.

(13) FIG. 17 is a cross-sectional view of a conformable wound dressing.

(14) FIG. 18 is a cross-sectional view of a conformable wound dressing.

(15) FIGS. 19a-b are cross-sectional views of conformable wound dressings.

(16) FIG. 20 is a cross-sectional view of a conformable wound dressing.

(17) FIGS. 21a-b are cross-sectional views of conformable wound dressings.

(18) FIG. 22 is a cross-sectional view of a conformable wound dressing.

(19) FIG. 23 is a cross-sectional view of a conformable wound dressing.

(20) FIG. 24 is a cross-sectional view of a conformable wound dressing.

(21) FIG. 25 is a cross-sectional view of a conformable wound dressing.

(22) FIG. 26 is a cross-sectional view of a conformable wound dressing.

(23) FIG. 27 is a cross-sectional view of a conformable wound dressing.

(24) FIG. 28 is a cross-sectional view of a conformable wound dressing.

(25) FIG. 29 is a cross-sectional view of a conformable wound dressing.

(26) FIG. 30a is a plan view and FIG. 30b a cross-sectional view of a further conformable wound dressings.

(27) FIGS. 31a and 31b are schematic views of an apparatus for aspirating, irrigating and/or cleansing a wound according to one embodiment of the present invention. It has a single-phase system means for fluid cleansing in the form of an ultrafiltration unit.

(28) FIG. 32 shows a schematic representation exudialysis flow system according to one embodiment of the present invention.

(29) FIG. 33 shows WST activity of fibroblasts with the addition of Dermagraft (the source of actives from live cells) in comparison to a media only control (TCM).

(30) FIG. 34 shows WST activity of fibroblasts (i) with an exudialysis system TCM+catalase, (ii) in a media with the addition of Dermagraft (the source of actives from live cells) Dg and hydrogen peroxide H.sub.2O.sub.2, (iii) in a media with the addition of Dermagraft (the source of actives from live cells) Dg, hydrogen peroxide (H.sub.2O.sub.2) and with an exudialysis system (+catalase). It has a single-phase system means for fluid cleansing in the form of an ultrafiltration unit.

(31) FIG. 35 shows average WST activity of fibroblasts on (a) control (TCM+Dg) of media and cells, (b) media, cell and Hydrogen peroxide (TCM+Dg+H.sub.2O.sub.2); and (c) media, cells, Hydrogen peroxide and exudialysis (TCM+Dg+catalase+H.sub.2O.sub.2). It has a single-phase system means for fluid cleansing, in the form of a container, e.g. a canister, cartridge or cassette, with a chamber or compartment that contains a cell or tissue component, through which the wound exudate or a mixture with irrigant passes.

(32) FIGS. 36a and b are variants of a two-pump system with essentially identical, and identically numbered, components as in FIGS. 14a-d. However, they have alternative means for handling the aspirate flow to the aspirate collection vessel under negative or positive pressure to the wound in simultaneous aspiration and irrigation of the wound, including in FIG. 30b a third device for moving fluid into a waste bag.

(33) FIG. 37 is a single-pump system essentially with the omission from the apparatus of FIGS. 14a-d of the second device for moving irrigant fluid into the wound dressing.

(34) FIG. 38 shows a schematic representation of a simultaneous irrigate/aspirate (SIA) and sequential irrigate/aspirate (SEQ) flow system.

(35) FIG. 39 shows increased WST activity of fibroblasts and thus increased proliferation of cells in a SIA system with actives from cells being added.

(36) FIG. 40 shows a summary of WST activity of fibroblasts in SEQ systems for 24 h with or with “cells as actives” component (n=3).

DETAILED DESCRIPTION OF THE EMBODIMENTS

(37) In all of the pertinent Figures, the components (12A), the fluid reservoir, and (12B), a container that contains a cell or tissue component, may, in alternative embodiments, be replaced by a single fluid reservoir (12), and vice versa.

(38) Referring to FIG. 1a, the apparatus (1) for aspirating, irrigating and/or 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 (4) over a wound (5) and one inlet pipe (6) for connection to a fluid supply tube (7), which passes through the wound-facing face of the backing layer (3) at (8), and one outlet pipe (9) for connection to a fluid offtake tube (10), which passes through the backing layer (3) at (11), the points (8), (11) at which the inlet pipe and the outlet pipe passes through and/or under the backing layer (3) forming a relatively fluid-tight seal or closure over the wound; the inlet pipe being connected via means for supply flow regulation, here a valve (14), by the fluid supply tube (7) to means for supplying physiologically active agents from cells or tissue to the wound, here a fluid reservoir (12A) and a container that contains a cell or tissue component (12B) connected to the supply tube (7), and the outlet pipe (9) being connected via means for aspirate flow regulation, here a valve (16) and a fluid offtake tube (10) to waste, e.g. to a collection bag (not shown); a device for moving fluid through the wound (5), here a diaphragm pump (18), e.g. preferably a small portable diaphragm pump, acting on the fluid offtake tube (10) to apply a low negative pressure on the wound; and the valve (14) in the fluid supply tube (7), the valve (16) in the fluid aspiration tube (13), and the diaphragm pump (18), providing means for providing simultaneous aspiration and irrigation of the wound (5), such that fluid may be supplied to fill the flowpath from the fluid reservoir via the container that contains the cell or tissue component, in turn connected to a supply tube, fluid supply tube (via the means for supply flow regulation) and moved by the device through the flow path.

(39) The operation of the apparatus is as described hereinbefore. In use, the inlet pipe, means for supply flow regulation, here valve (14), the fluid supply tube (7) and the container for cells or tissue (12B) contain physiologically active components from the cells or tissue in therapeutically active amounts to promote wound healing, and adds such materials into the flowpath.

(40) The supply of such physiologically active materials is here effected to the wound via the fluid passing through the wound dressing from irrigant in the container that contains the cells or tissue.

(41) Referring to FIG. 1b, the apparatus (1) for aspirating, irrigating and/or 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 (4) over a wound (5) and one inlet pipe (6) for connection to a fluid supply tube (7), which passes through the wound-facing face of the backing layer (3) at (8), and one outlet pipe (9) for connection to a fluid offtake tube (10), which passes through backing layer (3) at (11), the points (8), (11) at which the inlet pipe and the outlet pipe passes through and/or under the backing layer (3) forming a relatively fluid-tight seal or closure over the wound, the inlet pipe being connected via means for supply flow regulation, here a valve (14), by the fluid supply tube (7) to a container for cells or tissue in series with a fluid reservoir (the container and reservoir being shown as a single integer (12)), containing physiologically active components in therapeutically active amounts to promote wound healing, e.g. agents from cells or tissue to the wound, and to a fluid recirculation tube (13) having a means for bleeding the tube, here a valve (16) to waste, e.g. to a collection bag (not shown), the outlet pipe (9) being connected via means for aspirate flow regulation, here a valve (16) and to a fluid offtake tube (10), connected in turn to means for fluid cleansing, in (17), here in the form of either a container, e.g. a canister, cartridge or cassette, with a chamber or compartment that contains a cell or tissue component, through which the wound exudate or a mixture with irrigant passes, or else alternatively an ultrafiltration unit, connected to the inlet pipe (6) via the fluid recirculation tube (13) and T-valve (14), and a device for moving fluid through the wound (5) and means for fluid cleansing (17), here a peristaltic or diaphragm pump (18), e.g. preferably a small portable peristaltic or diaphragm pump, acting on the fluid circulation or aspiration tube (13) with the peripheral rollers on its rotor (not shown) to apply a low negative pressure on the wound; and the valve (14) in the fluid supply tube (7), the valve (16) in the fluid aspiration tube (13), and the diaphragm pump (18), providing means for simultaneous aspiration and irrigation of the wound (5), such that fluid may be supplied to fill the flowpath from the fluid reservoir via the container that contains the cell or tissue component, in turn connected to a supply tube, fluid supply tube (via the means for supply flow regulations) and moved by the device through the flow path.

(42) In one embodiment, in use, the inlet pipe, means for flow switching between supply and recirculation T-valve (14), the fluid supply tube (7), the valve (16) in the fluid offtake tube (10), and the diaphragm pump (18), providing means for providing simultaneous aspiration and irrigation of the wound (5) and the container for cells or tissue (part of the integer (12)) contain physiologically active components from the cells or tissue in therapeutically active amounts to promote wound healing, such that fluid may be supplied to fill the flowpath from the fluid reservoir via the fluid supply tube (via the means for supply flow regulation) and moved by the device through the flow path and adds such materials into the flowpath.

(43) The operation of the apparatus is as described hereinbefore.

(44) The supply of such physiologically active materials may be effected at any appropriate point for this purpose along the apparatus flow path, but it is (as here) often convenient to effect such supply to the wound via the fluid in recirculation through the wound dressing from irrigant in the container that contains the cells or tissue.

(45) The ultrafiltration unit (17) is a single-phase system. In this the circulating fluid from the wound and the container for cells or tissue, and the fluid reservoir passes through a self-contained system in which materials deleterious to wound healing are removed and the cleansed fluid, still containing materials that are beneficial in promoting wound healing, with added elements beneficial to wound healing to the exudate and irrigant (or modified irrigant), modified through biochemical, enzymatic or physical means to contain elements beneficial to wound healing, is returned via the recirculation tube to the wound bed.

(46) (In a variant of this apparatus, there are two inlet pipes (6), which are connected respectively to a fluid supply tube (7) and fluid recirculation tube (13), respectively having a first valve for admitting fluid into the wound from the container from cells or tissue and the fluid reservoir (together the integer 12) and a second valve for admitting fluid into the wound from the recirculation tube. Usually in use of the apparatus, when the first valve is open, the second valve is shut, and vice versa.)

(47) In use of the apparatus (1), the valve (16) is opened to a collection bag (not shown), and the T-valve (14) is turned to admit fluid from the container for cells or tissue and fluid reservoir (together the integer (12)) to the wound dressing through the fluid supply tube (7) and inlet pipe (6).

(48) (In the variant of this apparatus having two inlet pipes (6), which are connected respectively to a fluid supply tube (7) and fluid recirculation tube (13), the first valve for admitting fluid into the wound from the container for cells or tissue and fluid reservoir (together the integer (12)) is opened and the second valve is shut, and vice versa.)

(49) The pump (18) is started to nip the fluid recirculation tube (13) with the peripheral rollers on its rotor (not shown) to apply a low positive pressure on the wound. It is allowed to run until the apparatus is primed throughout the whole length of the apparatus flow path and excess fluid is voided to waste via the bleed T-valve (16) into the collection bag (not shown).

(50) The T-valve (14) is then turned to switch from supply and recirculation, i.e. is set to close the wound to the container from cells or tissue and the fluid reservoir (together the integer (12)) but to admit fluid into the wound from the fluid recirculation tube (13), and the bleed T-valve (16) is simultaneously closed.

(51) (In the variant of this apparatus, there are two inlet pipes (6), which are connected respectively to a fluid supply tube (7) and fluid recirculation tube (13).

(52) In operation, the first valve is closed and a recirculating system set up by opening the second valve for admitting fluid into the wound from the recirculation tube (13).

(53) The circulating fluid from the wound and the container for cells or tissue and the fluid reservoir (together the integer (12)) passes through the ultrafiltration unit (17).

(54) Materials deleterious to wound healing are removed and the cleansed fluid, still containing materials that are beneficial in promoting wound healing with added elements beneficial to wound healing to the exudate and irrigant (or modified irrigant), and/or modified through biochemical, enzymatic or physical means to contain elements beneficial to wound healing, is returned via the recirculation tube (13) to the wound bed. The recirculation of fluid may be continued as long as desired.

(55) Switching between supply and recirculation is then reversed, by turning the T-valve (14) to admit fluid from the fluid reservoir and the container for cells or tissue to the wound dressing through the fluid supply tube (7) and inlet pipe (6).

(56) (In the variant of this apparatus having two inlet pipes (6), which are connected respectively to a fluid supply tube (7) and fluid recirculation tube (13), the first valve (19) for admitting fluid into the wound from the container for cells or tissue and fluid reservoir (together the integer (12)) is opened and the second valve (20) is shut, and vice versa.)

(57) The bleed valve (16) is simultaneously opened, so that fresh fluid flushes the recirculating system.

(58) The running of the pump (18) may be continued until the apparatus is flushed, when it and the fluid recirculation is stopped.

(59) If, e.g. the wound is in a highly exuding state, there is a positive change in the balance of fluid in recirculation. It may be necessary to bleed fluid from recirculation, by opening the bleed T-valve (16) to bleed fluid from the recirculation tube (13).

(60) Referring to FIG. 2, the apparatus (21) is a variant of that of FIG. 1b, with essentially identical, and identically numbered, components, except for the means for fluid cleansing which is in the form of a two-phase system, here a dialysis unit (23). Here a fluid reservoir and a container that contains a cell or tissue component (together the integer 12) connected to the supply tube (7)

(61) In this, there is one system through which the circulating fluid from the wound and the container for cells or tissue and the fluid reservoir passes and from which deleterious materials are removed by selectively permeable contact with a second system, through which passes a cleansing fluid.

(62) The dialysis unit (23) thus has an internal polymer film, sheet or membrane (24), selectively permeable to materials deleterious to wound healing, which divides it into (a) first chamber (25), through which passes a cleansing fluid across one surface of the polymer film, sheet or membrane, and (b) a second chamber (26), through which passes the circulating fluid from the wound and the fluid reservoir (12), and from which deleterious materials are removed

(63) The dialysis unit (23) thus has a dialysate inlet pipe (28) connecting to a dialysate supply tube (29) which passes to a peristaltic pump (38), e.g. preferably a small portable peristaltic pump, acting on the dialysate supply tube (29) with the peripheral rollers on its rotor (not shown) to supply cleansing fluid across the surface of the polymer film, sheet or membrane (28) in the first chamber (25) from a dialysate reservoir (not shown) via a valve (34).

(64) The dialysis unit (23) also has a dialysate outlet pipe (30) connecting to a dialysate outlet tube (31) which passes to waste via a second bleed T-valve (36) into, e.g. a collection bag (not shown).

(65) Operation of this apparatus is similar to that of FIGS. 1a and 1b, except for the dialysis unit (27), in that at some point after the irrigation system is primed and steady state recirculation established through the length of the apparatus flow path, the valve (34) and second bleed valve (36) are opened.

(66) The pump (38) is started to nip fluid dialysate tube (29) with the peripheral rollers on its rotor (not shown) to pump cleansing fluid to the first chamber from a dialysate reservoir (not shown) and out to waste via the bleed valve (36) into the collection bag (not shown).

(67) The dialysis unit (23) is a module (or scrubbing cartridge) with a substrate that changes colour to indicate the presence of detrimental factors in the cleansed fluid, and that the scrubbing cartridge is exhausted and should be renewed.

(68) Referring to FIG. 3, the apparatus (21) is a variant two-pump system with essentially identical, and identically numbered, components as in FIGS. 1a and 1b, except that there is no means for supply flow regulation in the fluid supply tube (7) from the means for supplying physiologically active agents from cells or tissue to the wound, and there is a first device for moving fluid through the wound (5), here a diaphragm pump (18a), e.g. preferably a small portable diaphragm pump, acting on the fluid aspiration tube (13) downstream of and away from the wound dressing to apply a low negative pressure on the wound; with means for aspirate flow and/or negative pressure regulation, here a valve (16), connected to the fluid aspiration or vacuum tube (13) and a vacuum vessel (aspirate collection jar) (19); and a second device for moving fluid through the wound (5), here a peristaltic pump (18b), e.g. preferably a small portable diaphragm pump, applied to the irrigant in the fluid supply tube (7) upstream of and towards the wound dressing, the first device (18a) and second device (18b), and the valve (16) in the vacuum tube (13), and the diaphragm pump (18b), providing means for providing simultaneous (or sequential) aspiration and irrigation of the wound (5), such that fluid may be supplied to fill the flowpath from the fluid reservoir via the fluid supply tube (via the means for supply flow regulation) and moved by the devices through the flow path.

(69) The operation of the apparatus is as described hereinbefore.

(70) Referring to FIGS. 4a to 7, each dressing is in the form of a conformable body defined by a microbe-impermeable film backing layer (42) with a uniform thickness of 25 micron, with a wound-facing face which is capable of forming a relatively fluid-tight seal or closure over a wound.

(71) The backing layer (42) extends in use on a wound over the skin around the wound. On the proximal face of the backing layer (42) on the overlap, it bears an adhesive film (not shown), to attach it to the skin sufficiently to hold the wound dressing in place in a fluid-tight seal around the periphery of the wound-facing face of the wound dressing.

(72) There is one inlet pipe (46) for connection to a fluid supply tube (not shown), which passes through and/or under the backing layer (42), and one outlet pipe (47) for connection to a fluid offtake tube (not shown), which passes through and/or under the backing layer (42),

(73) Referring to FIGS. 4a and 4b, one form of the dressing is provided with a wound filler (48) under a circular backing layer (42). This comprises a generally frustroconical, toroidal conformable hollow body, defined by a membrane (49) which is filled with a fluid, here air or nitrogen, that urges it to the wound shape. The filler (48) may be permanently attached to the backing layer with an adhesive film (not shown) or by heat-sealing.

(74) The inlet pipe (46) and outlet pipe (47) are mounted centrally in the backing layer (42) above the central tunnel (50) of the toroidal hollow body (48) and each passes through the backing layer (42), and each extends in pipes (51) and (52) respectively through the tunnel (50) of the toroidal hollow body (48) and then radially in diametrically opposite directions under the body (48). In other embodiments the inlet (46) and outlet (47) pipes may pass under the backing layer (42).

(75) This form of the dressing is a more suitable layout for deeper wounds.

(76) Referring to FIGS. 5a and 5b, a more suitable form for shallower wounds is shown. This comprises a circular backing layer (42) and a circular upwardly dished first membrane (61) with apertures (62) that is permanently attached to the backing layer (42) by heat-sealing to form a circular pouch (63).

(77) The pouch (63) communicates with the inlet pipe (46) through a hole (64), and thus effectively forms an inlet pipe manifold that delivers the aspirating or circulating fluid directly to the wound when the dressing is in use.

(78) An annular second membrane (65) with openings (66) is permanently attached to the backing layer (42) by heat-sealing to form an annular chamber (67) with the layer (42).

(79) The chamber (67) communicates with the outlet pipe (47) through an orifice (68), and thus effectively forms an outlet pipe manifold that collects the fluid directly from the wound when the dressing is in use.

(80) Referring to FIGS. 6a and 6b, a variant of the dressing of FIGS. 4a and 4b that is a more suitable form for deeper wounds is shown.

(81) This comprises a circular backing layer (42) and a filler (69), in the form of an inverted frustroconical, solid integer, here a resilient elastomeric foam, formed of a thermoplastic, or preferably a cross-linked plastics foam.

(82) It is permanently attached to the backing layer (42), with an adhesive film (not shown) or by heat-sealing.

(83) A circular upwardly dished sheet (70) lies under and conforms to, but is a separate structure, permanently unattached to, the backing layer (42) and the solid integer (69).

(84) A circular upwardly dished first membrane (71) with apertures (72) is permanently attached to the sheet (70) by heat-sealing to form a circular pouch (73) with the sheet (70).

(85) The pouch (73) communicates with the inlet pipe (46) through a hole (74), and thus effectively forms an inlet pipe manifold that delivers the aspirating circulating fluid directly to the wound when the dressing is in use.

(86) An annular second membrane (75) with openings (76) is permanently attached to the sheet (70) by heat-sealing to form an annular chamber (77) with the sheet (70).

(87) The chamber (77) communicates with the outlet pipe (47) through an orifice (78), and thus effectively forms an outlet pipe manifold that collects the fluid directly from the wound when the dressing is in use.

(88) Alternatively, where appropriate the dressing may be provided in a form in which the circular upwardly dished sheet (70) functions as the backing layer and the solid filler (69) sits on the sheet (70) as the backing layer, rather than under it. The filler (69) is held in place with an adhesive film or tape (not shown), instead of the backing layer (42).

(89) Referring to FIGS. 7a and 7b, a dressing that is a more suitable form for deeper wounds is shown.

(90) This comprises a circular backing layer (42) and a filler (79), in the form of an inverted generally hemispherical integer, here a resilient elastomeric foam or a hollow body filled with a fluid, here a gel that urges it to the wound shape, and permanently attached to the backing layer with an adhesive film (not shown) or by heat-sealing.

(91) The inlet pipe (46) and outlet pipe (47) are mounted peripherally in the backing layer (42).

(92) A circular upwardly dished sheet (80) lies under and conforms to, but is a separate structure, permanently unattached to, the backing layer (42) and the filler (79).

(93) A circular upwardly dished bilaminate membrane (81) has a closed channel (82) between its laminar components, with perforations (83) along its length on the outer surface (84) of the dish formed by the membrane (81) and an opening (85) at the outer end of its spiral helix, through which the channel (82) communicates with the inlet pipe (46), and thus effectively forms an inlet pipe manifold that delivers the aspirating or circulating fluid directly to the wound when the dressing is in use.

(94) The membrane (81) also has apertures (86) between and along the length of the turns of the channel (82).

(95) The inner surface (87) of the dish formed by the membrane (81) is permanently attached at its innermost points (88) with an adhesive film (not shown) or by heat-sealing to the sheet (80). This defines a mating closed spirohelical conduit (89).

(96) At the outermost end of its spiral helix, the conduit (89) communicates through an opening (90) with the outlet pipe (47) and is thus effectively an outlet manifold to collect the fluid directly from the wound via the apertures (86).

(97) Referring to FIGS. 8a and 8b, one form of the dressing is provided with a circular backing layer (42). A first (larger) inverted hemispherical membrane (92) is permanently attached centrally to the layer (42) by heat-sealing to form a hemispherical chamber (94) with the layer (42). A second (smaller) concentric hemispherical membrane (93) within the first is permanently attached to the layer (42) by heat-sealing to form a hemispherical pouch (95).

(98) The pouch (95) communicates with the inlet pipe (46) and is thus effectively an inlet manifold, from which pipes (97) radiate hemispherically and run to the wound bed to end in apertures (98).

(99) The pipes (97) deliver the aspirating or circulating fluid directly to the wound bed via the apertures (98).

(100) The chamber (94) communicates with the outlet pipe (47) and is thus effectively an outlet manifold from which tubules (99) radiate hemispherically and run to the wound bed to end in openings (100). The tubules (99) collect the fluid directly from the wound via the openings (100).

(101) Referring to FIGS. 9a to 9d, one form of the dressing is provided with a square backing layer (42), and first tube (101) extending from the inlet pipe (46), and second tube (102) extending from the outlet pipe (47), at the points at which they pass through the backing layer, to run over the wound bed.

(102) These pipes (101) and (102) have a blind bore with orifices (103) and (104) along the pipes (101) and (102). These pipes (101) and (102) respectively form an inlet pipe or outlet pipe manifold that delivers the aspirating or circulating fluid directly to the wound bed or collects the fluid directly from the wound respectively via the orifices.

(103) In FIGS. 9a and 9d, one layout of each of the pipes (101) and (102) as inlet pipe and outlet pipe manifolds is a spiral.

(104) In FIG. 9b, the layout is a variant of that of FIGS. 9a and 9b, with the layout of the inlet manifold (101) being a full or partial torus, and the outlet manifold (102) being a radial pipe.

(105) Referring to FIG. 9c, there is shown another suitable layout in which the inlet manifold (101) and the outlet manifold (102) run alongside each other over the wound bed in a boustrophedic pattern, i.e. in the manner of ploughed furrows.

(106) Referring to FIGS. 10a to 10d, there are shown other suitable layouts for deeper wounds, which are the same as shown in FIGS. 9a to 9d. The square backing layer (42) however has a wound filler (110) under, and may be permanently attached to, the backing layer (42), with an adhesive film (not shown) or by heat-sealing, which is an inverted hemispherical solid integer, here a resilient elastomeric foam, formed of a thermoplastic, preferably a cross-linked plastics foam.

(107) Under the latter is a circular upwardly dished sheet (111) which conforms to, but is a separate structure, permanently unattached to, the solid filler (110). Through the sheet (111) pass the inlet pipe (46) and the outlet pipe (47), to run over the wound bed. These pipes (101) and (102) again have a blind bore with orifices (103) and (104) along the pipes (101) and (102).

(108) Alternatively (as in FIGS. 6a and 6b), where appropriate the dressing may be provided in a form in which the circular upwardly dished sheet (111) functions as the backing layer and the solid filler (110) sits on the sheet (42) as the backing layer, rather than under it. The filler (110) is held in place with an adhesive film or tape, instead of the backing layer (42).

(109) In FIGS. 11a to 11c, inlet and outlet manifolds for the wound dressings for respectively delivering fluid to, and collecting fluid from, the wound, are formed by slots in and apertures through layers permanently attached to each other in a stack.

(110) Thus, in FIG. 11a there is shown an exploded isometric view of an inlet manifold and outlet manifold stack (120) of five square coterminous thermoplastic polymer layers, being first to fifth layers (121) to (125), each attached with an adhesive film (not shown) or by heat-sealing to the adjacent layer in the stack (120).

(111) The topmost (first) layer (121) (which is the most distal in the dressing in use) is a blank square capping layer.

(112) The next (second) layer (122), shown in FIG. 11b out of the manifold stack (120), is a square layer, with an inlet manifold slot (126) through it. The slot (126) runs to one edge (127) of the layer (122) for connection to a mating end of a fluid inlet tube ((not shown), and spreads into four adjacent branches (128) in a parallel array with spaces therebetween.

(113) The next (third) layer (123) is another square layer, with inlet manifold apertures (129) through the layer (123) in an array such that the apertures (129) are in register with the inlet manifold slot (126) through the second layer (122) (shown in FIG. 11b).

(114) The next (fourth) layer (124), shown in FIG. 11c out of the manifold stack (120), is another square layer, with inlet manifold apertures (130) through the layer (124) in an array such that the apertures (130) are in register with the apertures (129) through the third layer (123). It also has an outlet manifold slot (131) through it. The slot (131) runs to one edge (132) of the layer (124) on the opposite side of the manifold stack (120) from the edge (127) of the layer (122), for connection to a mating end of a fluid outlet tube (not shown). It spreads into three adjacent branches (133) in a parallel array in the spaces between the apertures (130) in the layer (124) and in register with the spaces between the apertures (129) in the layer (122).

(115) The final (fifth) layer (125) is another square layer, with inlet manifold apertures (134) through the layer (125) in an array such that the apertures (134) are in register with the inlet manifold apertures (130) through the fourth layer (124) (in turn in register with the apertures (129) through the third layer (123)). It also has outlet manifold apertures (135) in the layer (125) in an array such that the apertures (135) are in register with the outlet manifold slot (131) in the fourth layer (124).

(116) It will be seen that, when the layers (121) to (125) are attached together to form the stack (120), the topmost (first) layer (121), the inlet manifold slot (126) through the second layer (122), and the third layer (123) cooperate to form an inlet manifold in the second layer (122), which in use is connected to a mating end of a fluid inlet tube (not shown).

(117) The inlet manifold slot (126) through the second layer (122), and the inlet manifold apertures (129), (130) and (134) through the layers (123), (124) and (125), all being mutually in register, cooperate to form inlet manifold conduits though the third to fifth layers (123), (124) and (125) between the inlet manifold in the second layer (122) and the proximal face (136) of the stack (120).

(118) The third layer (121), the outlet manifold slot (131) through the fourth layer (124), and the fifth layer (125) cooperate to form an outlet manifold in the fourth layer (124), which is in use is connected to a mating end of a fluid outlet tube (not shown).

(119) The outlet manifold slot (131) through the fourth layer (124), and the outlet manifold apertures (135) through the fifth layer (125), being mutually in register, cooperate to form outlet manifold conduits though the fifth layer (125) between the outlet manifold in the fourth layer (124) and the proximal face (136) of the stack (120).

(120) Referring to FIG. 12, the apparatus (1) for aspirating, irrigating and/or cleansing wounds is a variant of the apparatus (1) of FIG. 1b. It has bypass (711) around the pump (17), as a protection of the pump against any blockage in the system. It is activated automatically by appropriate means, e.g. it is normally blocked by a bursting disc (not shown), or a pressure-activated motorised valve. An alternative to the by-pass (711) is a pressure sensor in the system that will detect excessive load or pressure, and shut down the pump.

(121) Referring to FIG. 13, the apparatus (1) for aspirating, irrigating and/or cleansing wounds is a variant of the apparatus (1) of FIG. 2.

(122) The latter is a two-phase system with a dialysis unit (23), but is one in which dialytic fluid passes only once across the surface of the dialytic membrane (24) in the first chamber (25) from a dialysate reservoir (not shown) to waste via a second bleed T-valve (36) into, e.g. a collection bag (not shown).

(123) This variant has a dialysate recirculation tube (811) running between a first T-valve (34) on the inlet side of the dialysate pump (38) and a second T-valve (36) to permit the pump (23) to recirculate the dialysate once the circuit is primed in multiple passes through the dialysis unit (23).

(124) The operation of the system will be apparent to the skilled person.

(125) Referring to FIG. 14a, the apparatus (21) is a variant two-pump system with essentially identical, and identically numbered, components as in FIG. 3.

(126) Thus, there is a means for supply flow regulation, here a valve (14) in the fluid supply tube (7) from the fluid reservoir (12A), and a first device for moving fluid through the wound (5), here a fixed-speed diaphragm pump (18A), e.g. preferably a small portable diaphragm pump, acting not on the fluid aspiration tube (13), but on an air aspiration tube (113) downstream of and away from an aspirate collection vessel (19) to apply a low negative pressure on the wound through the aspirate collection vessel (19); with a second device for moving fluid through the wound (5), here a fixed-speed peristaltic pump (18B), e.g. preferably a small portable peristaltic pump, applied to the irrigant in the fluid supply tube (7) upstream of and towards the wound dressing, the first device (18A) and second device (18B), and the valve (14) in the fluid supply tube (7), providing means for providing simultaneous aspiration and irrigation of the wound (5), such that fluid may be supplied to fill the flowpath from the fluid reservoir via the fluid supply tube (via the means for supply flow regulation) and moved by the devices through the flow path.

(127) There is no means for aspirate flow regulation, e.g. a valve connected to the fluid offtake tube (10).

(128) Since the first device (18A) and second device (18B) are fixed-speed, the valve (14) in the fluid supply tube (7) provides the sole means for varying the irrigant flow rate and the low negative pressure on the wound.

(129) The following extra features are present:

(130) The second device, the fixed-speed peristaltic pump (18B), is provided with means for avoiding over-pressure, in the form of a bypass loop with a non-return valve (115). The loop runs from the fluid supply tube (7) downstream of the pump (18B) to a point in the fluid supply tube (7) upstream of the pump (18B).

(131) A pressure monitor (116) connected to the fluid offtake tube (10) has a feedback connection to a bleed regulator, here a motorised rotary valve (117) on a bleed tube (118) running to and centrally penetrating the top of the aspirate collection vessel (19). This provides means for holding the low negative pressure on the wound at a steady level.

(132) A filter (119) downstream of the aspirate collection vessel (19) prevents passage of gas- (often air-) borne particulates, including liquids and micro-organisms, from the irrigant and/or exudate that passes into the aspirate collection vessel (19) into the first device (18A), whilst allowing the carrier gas to pass through the air aspiration tube (113) downstream of it to the first device (18A). The operation of the apparatus is as described hereinbefore

(133) Referring to FIG. 14b, this shows an alternative layout of the essentially identical, and identically numbered, components in FIG. 14a downstream of point A in FIG. 14a. The bleed tube (118) runs to the air aspiration tube (113) downstream of the filter (119), rather than into the aspirate collection vessel (19). This provides means for holding the low negative pressure on the wound at a steady level. The operation of the apparatus is as described hereinbefore

(134) Referring to FIG. 14c, this shows an alternative layout of the essentially identical, and identically numbered, components in FIG. 14a upstream of point B in FIG. 14a. The second device (18B) is a variable-speed pump, and the valve (14) in the fluid supply tube (7) is omitted. The second device (18B) is the sole means for varying the irrigant flow rate and the low negative pressure on the wound. The operation of the apparatus is as described hereinbefore

(135) Referring to FIG. 14d, this shows an alternative layout of the essentially identical, and identically numbered, components in FIG. 14a downstream of point B in FIG. 14a. The pressure monitor (116) is connected to a monitor offtake tube (120) and has a feedback connection to the bleed regulator, motorised rotary valve (117) on a bleed tube (118) running to the monitor offtake tube (120). This provides means for holding the low negative pressure on the wound at a steady level. The operation of the apparatus is as described hereinbefore

(136) Referring to FIG. 15a, this shows another alternative layout of the essentially identical, and identically numbered, components in FIG. 14a downstream of point B in FIG. 14a. The pressure monitor (116) is connected to a monitor offtake tube (120) and has a feedback connection to a means for aspirate flow regulation, here a motorised valve (16) in the air aspiration tube (113) downstream of the filter (119). This provides means for aspirate flow regulation and for holding the low negative pressure on the wound at a steady level. The operation of the apparatus is as described hereinbefore

(137) Referring to FIG. 15b, this shows another alternative layout of the essentially identical, and identically numbered, components in FIG. 14a downstream of point B in FIG. 14a. The pressure monitor (116) is connected to a monitor offtake tube (120) and has a feedback connection to a means for aspirate flow regulation, here a motorised valve (16), in the fluid offtake tube (10) upstream of the aspirate collection vessel (19). This provides means for aspirate flow regulation and for holding the low negative pressure on the wound at a steady level. The operation of the apparatus is as described hereinbefore

(138) Referring to FIG. 15c, this shows another alternative layout of the essentially identical, and identically numbered, components in FIG. 14a downstream of point B in FIG. 14a. The pressure monitor (116) is connected to a monitor offtake tube (120) and has a feedback connection to a variable-speed first device (18A), here a variable-speed pump, downstream of the filter (119), and the valve (16) in the fluid offtake tube (10) is omitted. This provides means for aspirate flow regulation and for holding the low negative pressure on the wound at a steady level. The operation of the apparatus is as described hereinbefore.

(139) Referring to FIGS. 16 to 18, these forms of the dressing are provided with a wound filler (348) under a circular backing layer (342). This comprises respectively a generally downwardly domed or toroidal, or oblately spheroidal conformable hollow body, defined by a membrane (349) which is filled with a fluid, here air or nitrogen, that urges it to the wound shape. The filler (348) is permanently attached to the backing layer via a boss (351), which is e.g. heat-sealed to the backing layer (342). An inflation inlet pipe (350), inlet pipe (346) and outlet pipe (347) are mounted centrally in the boss (351) in the backing layer (342) above the hollow body (348). The inflation inlet pipe (350) communicates with the interior of the hollow body (348), to permit inflation of the body (348). The inlet pipe (346) extends in a pipe (352) effectively through the hollow body (348). The outlet pipe (347) extends radially immediately under the backing layer (342).

(140) In FIG. 16, the pipe (352) communicates with an inlet manifold (353), formed by a membrane (361) with apertures (362) that is permanently attached to the filler (348) by heat-sealing. It is filled with foam (363) formed of a suitable material, e.g. a resilient thermoplastic. Preferred materials include reticulated filtration polyurethane foams with small apertures or pores.

(141) In FIG. 17, the outlet pipe (347) communicates with a layer of foam (364) formed of a suitable material, e.g. a resilient thermoplastic. Again, preferred materials include reticulated filtration polyurethane foams with small apertures or pores.

(142) In all of FIGS. 16, 17 and 18, in use, the pipe (346) ends in one or more openings that deliver the irrigant fluid directly from the wound bed over an extended area. Similarly, the outlet pipe (347) effectively collects the fluid radially from the wound periphery when the dressing is in use.

(143) Referring to FIG. 19, the dressing is also provided with a wound filler (348) under a circular backing layer (342). This also comprises a generally toroidal conformable hollow body, defined by a membrane (349) which is filled with a fluid, here air or nitrogen, that urges it to the wound shape. The filler (348) may be permanently attached to the backing layer (342) via a first boss (351) and a layer of foam (364) formed of a suitable material, e.g. a resilient thermoplastic. Again, preferred materials include reticulated filtration polyurethane foams with small apertures or pores. The first boss (351) and foam layer (364) are respectively heat-sealed to the backing layer (342) and the boss (351). An inflation inlet pipe (350), inlet pipe (346) and outlet pipe (347) are mounted centrally in the first boss (351) in the backing layer (342) above the toroidal hollow body (348).

(144) The inflation inlet pipe (350), inlet pipe (346) and outlet pipe (347) respectively each extend in a pipe (353), (354) and (355) through a central tunnel (356) in the hollow body (348) to a second boss (357) attached to the toroidal hollow body (348). The pipe (353) communicates with the interior of the hollow body (348), to permit inflation of the body (348). The pipe (354) extends radially through the second boss (357) to communicate with an inlet manifold (352), formed by a membrane (361) that is permanently attached to the filler (348) by heat-sealing in the form of a reticulated honeycomb with openings (362) that deliver the irrigant fluid directly to the wound bed over an extended area. The pipe (355) collects the fluid flowing radially from the wound center when the dressing is in use.

(145) This form of the dressing is a more suitable layout for deeper wounds

(146) In FIG. 20, the dressing is similar to that of FIG. 19, except that the toroidal conformable hollow body, defined by a membrane (349), is filled with a fluid, here solid particulates, such as plastics crumbs or beads, rather than a gas, such as air or an inert gas, such as nitrogen or argon, and the inflation inlet pipe (350) and pipe (353) are omitted from the central tunnel (356). Examples of contents for the body (348) also include gels, such as silicone gels or preferably cellulosic gels, for example hydrophilic cross-linked cellulosic gels, such as Intrasite™ cross-linked materials. Examples also include aerosol foams, and set aerosol foams, e.g. CaviCare™ foam.

(147) Referring to FIGS. 21 and 22, another form for deeper wounds is shown. This comprises a circular backing layer (342) and a chamber (363) in the form of a deeply indented disc much like a multiple Maltese cross or a stylised rose. This is defined by an upper impervious membrane (361) and a lower porous film (362) with apertures (352) that deliver the irrigant fluid directly from the wound bed over an extended area. A number of configurations of the chamber (363) are shown, all of which are able to conform well to the wound bed by the arms closing in and possibly overlapping in insertion into the wound. In a particular design of the chamber (363), shown lowermost, on of the arms extended and provided with an inlet port at the end of the extended arm. This provides the opportunity for coupling and decoupling the irrigant supply remote from the dressing and the wound in use. An inlet pipe (346) and outlet pipe (347) are mounted centrally in a boss (351) in the backing layer (342) above the chamber (363). The inlet pipe (346) is permanently attached to, and communicate with the interior of, the chamber (363), which thus effectively forms an inlet manifold. The space above the chamber (363) is filled with a loose gauze packing (364).

(148) In FIG. 21, the outlet pipe (347) collects the fluid from the interior of the dressing from just under the wound-facing face of the backing layer (342).

(149) A variant of the dressing of FIG. 21 is shown in FIG. 22. The outlet pipe (347) is mounted to open at the lowest point of the space above the chamber (363) into a piece of foam (354).

(150) In FIG. 23, the dressing is similar to that of FIG. 16, except that the inlet pipe (352) communicates with an inlet manifold (353), formed by a membrane (361) with apertures (362), over the upper surface of the generally downwardly domed wound hollow filler, rather than through it.

(151) In FIG. 24, the generally downwardly domed annular wound hollow filler is omitted.

(152) In FIG. 25, the dressing is similar to that of FIG. 17, with the addition of an inlet manifold (353), formed by a membrane (361) with apertures (362), over the lower surface of the generally downwardly domed annular wound hollow filler.

(153) Referring to FIG. 26, another form for deeper wounds is shown. An inlet pipe (346) and outlet pipe (347) are mounted centrally in a boss (351) in the backing layer (342) above a sealed-off foam filler (348). The inlet pipe (346) is permanently attached to and passes through the filler (348) to the wound bed. The outlet pipe (347) is attached to and communicates with the interior of, a chamber (363) defined by a porous foam attached to the upper periphery of the filler (348). The chamber (363) thus effectively forms an outlet manifold.

(154) In FIG. 27, the foam filler (348) is only partially sealed-off. The inlet pipe (346) is permanently attached to and passes through the filler (348) to the wound bed. The outlet pipe (347) is attached to and communicates with the interior of the foam of the filler (348). Fluid passes into an annular gap (349) near the upper periphery of the filler (348) into the foam, which thus effectively forms an outlet manifold.

(155) FIGS. 28 and 29 show dressings in which the inlet pipe (346) and outlet pipe (347) pass through the backing layer (342).

(156) In FIG. 28, they communicate with the interior of a porous bag filler (348) defined by a porous film (369) and filled with elastically resilient plastics bead or crumb.

(157) In FIG. 29, they communicate with the wound space just below a foam filler (348). The foam (348) may be CaviCare™ foam, injected and formed in situ around the pipes (346) and (347).

(158) Referring to FIG. 30, another form for deeper wounds is shown. This comprises a circular, or more usually square or rectangular backing layer (342) and a chamber (363) in the form of a deeply indented disc much like a multiple Maltese cross or a stylised rose. This is defined by an upper impervious membrane (361) and a lower porous film (362) with apertures (364) that deliver the irrigant fluid directly to the wound bed over an extended area, and thus effectively forms an inlet manifold. Three configurations of the chamber (363) are shown in FIG. 30b, all of which are able to conform well to the wound bed by the arms closing in and possibly overlapping in insertion into the wound.

(159) The space above the chamber (363) is filled with a wound filler (348) under the backing layer (342). This comprises an oblately spheroidal conformable hollow body, defined by a membrane (349) that is filled with a fluid, here air or nitrogen, that urges it to the wound shape.

(160) A moulded hat-shaped boss (351) is mounted centrally on the upper impervious membrane (361) of the chamber (363). It has three internal channels, conduits or passages through it (not shown), each with entry and exit apertures. The filler (348) is attached to the membrane (361) of the chamber (363) by adhesive, heat welding or a mechanical fixator, such as a cooperating pin and socket.

(161) An inflation inlet pipe (350), inlet pipe (346) and outlet pipe (347) pass under the edge of the proximal face of the backing layer (342) of the dressing, and extend radially immediately under the filler (348) and over the membrane (361) of the chamber (363) to each mate with an entry aperture in the boss (351).

(162) An exit to the internal channel, conduit or passage through it that receives the inflation inlet pipe (350) communicates with the interior of the hollow filler (348), to permit inflation.

(163) An exit to the internal channel, conduit or passage that receives the inlet pipe (346) communicates with the interior of the chamber (363) to deliver the irrigant fluid via the chamber (363) to the wound bed over an extended area.

(164) Similarly, an exit to the internal channel, conduit or passage that receives the outlet pipe (347) communicates with the space above the chamber (363) and under the wound filler (348), and collects flow of irrigant and/or wound exudate radially from the wound periphery.

(165) Referring to FIG. 31a, the apparatus (1) for aspirating, irrigating and/or cleansing wounds is a major variant of the apparatus shown in FIG. 1b.

(166) The device for moving fluid through the wound and means for fluid cleansing (17) in FIG. 1b is a peristaltic pump (18), e.g. preferably a small portable peristaltic pump, acting on the fluid circulation tube (13) downstream of the dressing (2) to apply a low negative pressure on the wound.

(167) In the apparatus (1) shown in FIG. 31a, the peristaltic pump (18) is replaced by: (a) a peristaltic pump (926) acting on the fluid supply tube (7) upstream of the dressing (2), and (b) a vacuum pump assembly (918) with pressure regulating means, acting downstream of the dressing (2), to apply an overall low negative pressure in the wound space.

(168) The vacuum pump assembly comprises a tank (911) with an inlet tube (912) connecting to the fluid circulation tube (13) and communicating with the upper part of the tank (911), a waste tube (913) connecting to a waste pump (914) with waste bag (915) and communicating with the lower part of the tank (911), a pump tube (916) connecting to a vacuum pump (918) and communicating with the upper part of the tank (911), and an outlet tube (917) connecting to the fluid circulation tube (13) to the means for cleansing (17) and communicating with the lower part of the tank (911).

(169) The vacuum pump (918) is controlled by a pressure feedback regulator (919) through an electrical line (920), the regulator receiving signals from a tank sensor (921) in the upper part of the tank (911), and a dressing sensor (922) in the wound space respectively via lines (923) and (924).

(170) The pressure feedback regulator (919) regulates the pressure at the wound and/or the tank (911).

(171) If the amount of fluid in circulation becomes excessive, e.g. because the wound continues to exude heavily, the waste pump (914) may be started to transfer fluid from the lower part of the tank (911) to the waste bag (915).

(172) Referring to FIG. 31b, the apparatus is as described in FIG. 31a, except that the vacuum pump assembly comprises a tank (911) with an inlet tube (912) connecting to the fluid circulation tube (13) and communicating with the upper part of the tank (911), a waste tube (913) connecting to a waste pump (914) with waste bag (915) and communicating with the lower part of the tank (911), a pump tube (917) connecting to a vacuum pump (918) and communicating with the upper part of the tank (911), and connecting via the fluid circulation tube (13) to the means for cleansing (17) and communicating with the lower part of the tank (911).

(173) Additionally, the waste pump (914) is controlled by a waste level feedback regulator (929) the regulator receiving signals from a tank sensor with electrical line (930) in the middle part of the tank (911).

(174) The vacuum pump (918) either acts as a valve so that the pump tube 917 connecting to the vacuum pump (918) is normally blocked to prevent passage of air through it from the upper part of the tank (911) when the vacuum pump (918) is at rest, or the pump tube (917) is provided with a manual or motorised, e.g. pressure-activated motorised, valve (930) (not shown), so that the pump tube (917) connecting to the vacuum pump (918) may be blocked to prevent such passage.

(175) The operation of the apparatus (1) is similar to that of the apparatus in FIG. 1b mutatis mutandis.

(176) In use of the apparatus (1), the valve (16) is opened to a collection bag (not shown), and the T-valve (14) is turned to admit fluid from the fluid reservoir (part of the integer (12)) to the wound dressing through the fluid supply tube (7) and inlet pipe (6).

(177) The pump (926) is started to nip the fluid recirculation tube (7) with the peripheral rollers on its rotor (not shown) to apply a low positive pressure on the wound.

(178) The vacuum pump (918) either acts as a valve since it is at rest, or the valve (930) (not shown) is closed, so that the pump tube 917 is blocked to prevent passage of air through it from the upper part of the tank (911).

(179) Irrigant pumped from the wound dressing (2) through the fluid offtake tube (10) is pumped through the lower part of the tank (911) up the outlet tube (917) via the means for cleansing (17) to the bleed T-valve (16) into, e.g. a collection bag (not shown).

(180) The peristaltic pump (926) acting on the fluid supply tube (7) upstream of the dressing (2) is allowed to run until the apparatus is primed throughout the whole length of the apparatus flow path and excess fluid is voided to waste via the bleed T-valve (16) into the collection bag.

(181) The T-valve (14) is then turned to switch from supply to recirculation, i.e. is set to close the wound to the fluid reservoir (part of the integer (12)) but to admit fluid into the wound from the fluid recirculation tube (13), and the bleed T-valve (16) is simultaneously closed.

(182) The vacuum pump (918) is then activated, and, if the vacuum pump (918) does not act as a valve when at rest, the valve (930) in the pump tube 917 is opened, to apply a low negative pressure to the wound.

(183) The circulating fluid from the wound and the fluid reservoir (part of the integer (12)) passes through the cleansing unit (17). Materials deleterious to wound healing are removed and the cleansed fluid, still containing materials that are beneficial in promoting wound healing, is returned via the recirculation tube (13) to the wound bed.

(184) The pressure feedback regulator (919) regulates the pressure at the wound and/or the tank (911).

(185) If the amount of fluid in circulation becomes excessive, e.g. because the wound continues to exude heavily, the waste pump (914) may be started by the waste level feedback regulator (929) on the regulator receiving signals from the tank sensor with electrical line (930), to transfer fluid from the lower part of the tank (911) to the waste bag (915).

(186) The recirculation of fluid may be continued as long as desired.

(187) The vacuum pump (918) is then deactivated, and, if the vacuum pump (918) does not act as a valve when at rest, the valve (930) in the pump tube (917) is closed, and the bleed T-valve (16) is opened to air to relieve the low negative pressure in the tank (911) via the means for cleansing (17) and the outlet tube (917).

(188) Switching between supply and recirculation is then reversed, by turning the T-valve (14) to admit fluid from the fluid reservoir to the wound dressing through the fluid supply tube (7) and inlet pipe (6).

(189) The bleed valve (16) is left open, so that fresh fluid flushes the recirculating system. The running of the pump (918) may be continued until the apparatus is flushed, when it and the fluid recirculation is stopped.

(190) Referring to FIG. 36a, this shows another alternative layout of the essentially identical, and identically numbered, components in FIG. 15c downstream of point B in FIG. 14a, and alternative means for handling the aspirate flow to the aspirate collection vessel under negative or positive pressure to the wound.

(191) The pressure monitor (116) is connected to a monitor offtake tube (120) and has a feedback connection to a variable-speed first device (18A), here a variable-speed pump, upstream of the aspirate collection vessel (19), and the filter (119) and the air aspiration tube (113) are omitted. This provides means for aspirate flow regulation and for holding the low negative pressure on the wound at a steady level. The operation of the apparatus is as described hereinbefore.

(192) Referring to FIG. 36b, this shows another alternative layout of the essentially identical, and identically numbered, components in FIG. 14b downstream of point A in FIG. 14a, and alternative means for handling the aspirate flow to the aspirate collection vessel under negative or positive pressure to the wound. The pressure monitor (116) is omitted, as is the feedback connection to a variable-speed first device (18A), here a variable-speed pump, downstream of the aspirate collection vessel (19) and the filter (119). A third device (18C), here a fixed-speed pump, provides means for moving fluid from the aspirate collection vessel (19) into a waste bag (19A). The operation of the apparatus is as described hereinbefore.

(193) Referring to FIG. 37, this shows an alternative layout of the essentially identical, and identically numbered, components in FIG. 14a upstream of point.

(194) It is a single-pump system essentially with the omission from the apparatus of FIG. 14a of the second device for moving irrigant fluid into the wound dressing. The operation of the apparatus is as described hereinbefore.

EXAMPLES

(195) The use of the apparatus of the present invention will now be described by way of example only in the following Examples:

Example 1

(196) The removal by dialysis of materials deleterious to wound healing (H.sub.2O.sub.2) by an enzyme (catalase) retained in a moving second phase was combined with the addition of an active agent (PDGF) to the moving first phase.

(197) An apparatus was constructed essentially as in FIG. 2, i.e. one in which the means for fluid cleansing is a two-phase system dialysis unit. In such an apparatus, an irrigant and/or wound exudate first phase from the wound recirculates through a first circuit and passes through the dialysis unit in contact across a selectively permeable dialysis membrane with a second fluid (dialysate) phase. The dialysis unit was operated with the two phases flowing counter-current to each other.

(198) Hydrogen peroxide is produced in conditions of oxidative stress following reduced blood flow and or the inflammatory response to bacterial contamination of wounds. It may be removed by the appropriate antagonists and/or degraders, which include enzymic or other inhibitors, such as peroxide degraders, e.g. catalase.

(199) The first circuit comprised a surrogate wound chamber (Minucells perfusion chamber) in which normal diploid human fibroblasts were cultured on 13 mm diameter (Thermanox polymer) cover slips retained in a two part support (Minnucells Minusheets). Tissues present in the healing wound that must survive and proliferate were represented by the cells within the chamber. Nutrient medium (DMEM with 5% FCS with 1% Buffer All) to simulate wound exudate was pumped from a reservoir into the lower aspect of the chamber where it bathed the fibroblasts and was removed from the upper aspect of the chamber and returned to the reservoir.

(200) The first circuit also comprised upstream of the wound chamber, a luer-fitting hollow fibre tangential membrane dialysis unit (Spectrum® MicroKros® X14S-100-04N, 8 cm.sup.2 surface area, 400 KD Mol. Wt. cut off,) through which a second cleansing circuit containing nutrient media with between 5,000 and 50,000 units (μmoles H.sub.2O.sub.2 degraded per min at pH7, 25° C.) per ml of catalase (in a circuit with a reservoir and total volume of between 5.0 ml and 20 ml) at a flow rate of between 0.5 ml min.sup.−1 and 5.0 ml min.sup.−1 could be passed in a counter current direction,

(201) The pumps for the two circuits were peristaltic pumps acting on silicone (or equivalent) elastic tubing. The internal diameter of the tubing was 1.0 mm. A total volume for the first circuit including the chamber and the reservoir at a number of values between 25 and 75 ml was used. The flow rates used were at a number of values between 0.5 ml min.sup.−1 and 5.0 ml min.sup.−1.

(202) An experiment was conducted that simulated conditions not uncommon for healing wounds whereby the nutrient medium containing a material deleterious to wound healing, namely hydrogen peroxide, was circulated over the cells.

(203) A solution of human recombinant Platelet Derived Growth Factor B was added to the reservoir of the first circuit so that the resulting concentration of PDGF-B lies at a number of values between 20 μg ml.sup.−1 to 320 μg ml.sup.−1, the fibroblasts survive and proliferate during.

(204) A control experiment was also conducted where the solution of human recombinant Platelet Derived Growth Factor B is not added to the reservoir of the first circuit.

(205) Results and Conclusions

(206) In controls where either a) the passage of the nutrient flow through the cleansing membrane dialysis unit or b) the solution of human recombinant Platelet Derived Growth Factor B is not added to the reservoir of the first circuit heat, and the concentration of H.sub.2O.sub.2 lies between 5 and 20 mM survival and growth of the fibroblasts is inhibited.

(207) However, when the nutrient medium flow in the first circuit is a) connected into the ends of the membrane dialysis unit through which a second cleansing circuit containing catalase (at the concentrations and flow rates noted above) is passing in a counter current direction, and b) the solution of human recombinant Platelet Derived Growth Factor B is added to the nutrient media bathing the cells, the fibroblasts survive and proliferate during a 24 hour period.

(208) The combination of the cleansing dialysis unit and the active growth factor enhances the cell response necessary for wound healing.

Example 2

(209) The removal by dialysis of materials deleterious to wound healing (H.sub.2O.sub.2) by an enzyme (catalase) retained in a static second phase was combined with the addition of an active agent (PDGF) to the moving first phase.

(210) An apparatus of the present invention was constructed essentially as in FIG. 2, i.e. one in which the means for fluid cleansing is a two-phase system dialysis unit.

(211) In such an apparatus, an irrigant and/or wound exudate first phase from the wound recirculates through a first circuit and passes in contact, across a selectively permeable dialysis membrane, with a static second fluid (dialysate) phase.

(212) Hydrogen peroxide is produced in conditions of oxidative stress following reduced blood flow and or the inflammatory response to bacterial contamination of wounds. It may be removed by the appropriate antagonists and/or degraders, which include enzymic or other inhibitors, such as peroxide degraders, e.g. catalase.

(213) The first circuit comprises a surrogate wound chamber (Minucells perfusion chamber) in which normal diploid human fibroblasts are cultured on 13 mm diameter (Thermanox polymer) cover slips retained in a two part support (Minnucells Minusheets). Tissues present in the healing wound that must survive and proliferate were represented by the cells within the chamber. Nutrient medium (DMEM with 5% FCS with 1% Buffer All) to simulate wound exudate was pumped from a reservoir into the lower aspect of the chamber where it bathed the fibroblasts and was removed from the upper aspect of the chamber and returned to the reservoir.

(214) The first circuit also includes, upstream of the wound chamber, a static second phase dialysis unit, comprising a length of dialysis tubing (Pierce Snake skin 68100 CG 49358B, 10 KD cut off) placed within the first circuit reservoir in which a static second phase second cleansing circuit containing nutrient media with between 5,000 and 50,000 units (μmoles H.sub.2O.sub.2 degraded per min at pH7, 25° C.) per ml of catalase (in a circuit with a reservoir and total volume of between 5.0 ml and 20 ml) at a flow rate of between 0.5 ml min.sup.−1 and 5.0 ml min.sup.−1.

(215) The pump was a peristaltic pump acting on silicone (or equivalent) elastic tubing. The internal diameter of the tubing was 1.0 mm. A total volume for the first circuit including the chamber and the reservoir at a number of values between 25 and 75 ml was used. The flow rates used were at a number of values between 0.5 ml min.sup.−1 and 5.0 ml min.sup.−1.

(216) An experiment was conducted that simulated conditions not uncommon for healing wounds whereby the nutrient medium containing a material deleterious to wound healing, namely hydrogen peroxide, was circulated over the cells.

(217) A solution of human recombinant Platelet Derived Growth Factor B was added to the reservoir of the first circuit so that the resulting concentration of PDGF-B lies at a number of values between 20 μg ml.sup.−1 to 320 μg ml.sup.−1, the fibroblasts survive and proliferate.

(218) A control experiment was also conducted where the solution of human recombinant Platelet Derived Growth Factor B is not added to the reservoir of the first circuit.

(219) Results and Conclusions

(220) The following results were obtained for a first phase circuit comprising a wound chamber as above containing nutrient media (75 ml) with H.sub.2O.sub.2 (10 μM) pumped at a flow rate of 1.0 ml min.sup.−1 in contact with a static second phase (15 ml) containing catalase (7,600 units ml.sup.−1), where the wound chamber and media were held at 37° C. for 45 hours.

(221) TABLE-US-00001 Mean level of cell activity* (n = 3) after Conditions 45 hours incubation. Nutrient media only 0.47 Media with H.sub.2O.sub.2 only 0.00 H.sub.2O.sub.2 + catalase 2.sup.nd phase dialysis unit 0.64 H.sub.2O.sub.2 + catalase 2.sup.nd phase dialysis unit + 0.56 40 ng/ml PDGF H.sub.2O.sub.2 + catalase 2.sup.nd phase dialysis unit + 0.86 80 ng/ml PDGF *Cell activity measured with a WST (Tetrazolium based mitochondrial dehdrogenase activity assay).

(222) In the controls where either a) the passage of the nutrient flow across the cleansing membrane dialysis unit or b) the solution of human recombinant Platelet Derived Growth Factor B is not added to the reservoir of the first circuit, and the concentration of H.sub.2O.sub.2 lies between 5 and 20 mM survival, growth of the fibroblasts is inhibited.

(223) However, when the nutrient medium flow in the first circuit is a) passed over the membrane dialysis unit in which a second cleansing circuit containing catalase (at the concentrations and flow rates noted above) is present, and b) the solution of human recombinant Platelet Derived Growth Factor B (80 ng/ml) is added to the nutrient media bathing the cells, the fibroblasts survive and proliferate to a greater extent than in the control circuits.

(224) The combination of the wound cleansing dialysis unit that removes and degrades H.sub.2O.sub.2 and the addition of the active PDGF growth factor at 80 ng/ml enhances the cell response necessary for wound healing.

Example 3

(225) Adherent bacteria and debris was removed with a two-pump apparatus.

(226) In this example, a culture medium sheet containing nutritional supplements with an adherent bacterial culture of Staphylococcus aureus on its top surface was laid in a cavity wound model to represent adherent bacteria and debris on a wound bed to be removed by the two-pump apparatus.

(227) The dressing was essentially identical with that in FIG. 21, i.e. it comprised a circular backing layer and a lobed chamber in the form of a deeply indented disc much like a multiple Maltese cross or a stylised rose, defined by an upper impervious membrane and a lower porous film with apertures that deliver the irrigant fluid directly from the wound bed over an extended area.

(228) The irrigant supplied to the wound dressing under a negative pressure on the wound bed contains a therapeutically active amount of an antibacterial agent, selected from chlorhexidine, povidone iodine, triclosan, metronidazole, cetrimide and chlorhexidine acetate.

(229) A two-pump system was set up essentially as in FIG. 3, with an irrigant dispensing bottle—1000 ml Schott Duran, connected to a peristaltic pump (Masterflex) for irrigant delivery, and associated power supply and supply tube, a diaphragm vacuum pump (Schwarz) for aspiration, and associated power supply and offtake tube, connected to a vacuum vessel (aspirant collection jar)—Nalgene 150 ml polystyrene, each pump being connected to a dressing consisting of the following elements: 1) wound-contacting element, comprising a lobed bag with low porosity ‘leaky’ membrane wound contact layer on the lower surface, impermeable film on the top, and a foam spacer between the two layers to allow free flow of irrigant solution; 2) a space filling element, comprising a reticulated, open-cell foam (black reticulated foam, Foam Techniques) 30 mm thick, 60 mm diameter; 3) an occlusive adhesive coated polyurethane backing layer top film (Smith & Nephew Medical) with acrylic pressure sensitive adhesive; 4) two tubes passing under the occlusive top film, and sealed to prevent leakage of gas or liquid: i) one tube centrally penetrating the top film of the wound-contacting element to deliver irrigant into the chamber formed by this film and the porous element; ii) the other tube of approximately equal length to remove aspirant with the opening positioned just above the top film of the wound contacting element.

(230) Preparation of Agar Culture Medium Sheet with Adherent Staphylococcus Aureus Culture.

(231) An aqueous solution of agar culture medium was prepared by weighing agar culture medium containing nutritional supplements into a glass jar and making it up to the required weight with deionized water. The jar was placed in an oven (Heraeus), at a set temperature. After 60 minutes the jar was removed from the oven and shaken, to encourage mixing.

(232) Petri dishes were partially filled with 10 g quantities of the culture medium and placed in a fridge (LEC, set temperature: 4° C.) to set for at least 1 hour.

(233) Final thickness of the culture medium sheet was ˜5 mm. Petri dishes containing the culture medium sheet were removed from the fridge at least 2 hours before use. The culture medium sheet in the Petri dishes was then inoculated with Staphylococcus aureus.

(234) Each was then placed in an incubator at a set temperature.

(235) After the culture had covered more than 50% of the agar surface the dishes were removed from the incubator.

(236) They were placed in a fridge, and removed from the fridge at least 2 hours before use.

(237) Preparation of Test Equipment and Materials

(238) Irrigant solution (deionized water containing a therapeutically effective amount of an antibacterial agent, selected from chlorhexidine, povidone iodine, triclosan, metronidazole, cetrimide and chlorhexidine acetate) and the Perspex wound model were pre-conditioned in an oven (Gallenkamp) at set temperature 37° C., for at least 4 hours before use.

(239) For each test, a freshly prepared culture medium sheet with adherent Staphylococcus aureus culture was removed from a Petri dish and weighed. The Perspex wound model was then removed from the oven and the culture medium sheet with adherent Staphylococcus aureus culture placed at the bottom of the cavity. Application of the dressing to the wound model was as follows: 1) the wound contacting element was carefully placed over the culture medium sheet with adherent Staphylococcus aureus culture; 2) the foam filler was placed on top of this with the irrigant and aspirant tubes running centrally to the top of the cavity (the foam filler was slit to the center to facilitate this); 3) the side entry port, pre-threaded onto the tubes, was adhesively bonded to the upper surface of the wound model block using an acrylic pressure sensitive adhesive; 4) the top adhesive coated film was applied over all of the elements and pressed down to give a seal on all sides, and especially around the tube entry/exit point

(240) Application of the dressing to the wound model was the same for all tests performed. All tubing used was the same for each experiment (e.g. material, diameter, length).

(241) Simultaneous Irrigation & Aspiration

(242) For the experiment most of the apparatus (not including the pumps, power supply, and connecting tubing to and from the pumps) was placed in an oven (Gallenkamp, set temperature: 37° C.), on the same shelf.

(243) Before starting the irrigation pump a vacuum was drawn on the system to check that the dressing and tube connections were substantially airtight.

(244) The pumping system was controlled to give a pressure at the vacuum vessel of approximately −75 mmHg before opening the system up to include the dressing). Once system integrity had been confirmed, the irrigation pump was started (nominal flow rate: 50 ml/hr), i.e. both pumps running together. Timing of the experiment was started when the advancing water front within the irrigant tube was observed to have reached the top of the dressing.

(245) After 60 minutes, the irrigation pump was stopped, shortly followed by the vacuum (aspiration) pump. Aspirant liquid collected in the vacuum jar was decanted into a glass jar. The vacuum jar was rinsed with ˜100 ml of deionized water and this added to the same glass jar. The aspirant solution was then assayed for the Staphylococcus aureus quantity present.

(246) Sequential Irrigation & Aspiration

(247) The experimental set up was as for the simultaneous irrigation/aspiration experiment. Before starting the experiment a vacuum was pulled on the system to check that the dressing and tube connections were substantially airtight. The pumping system was controlled to give a pressure at the vacuum vessel of approximately −75 mmHg before opening the system up to include the dressing. Once system integrity had been confirmed, the irrigation pump was started (nominal rate: 186 ml/hr) and run until the advancing water front in the irrigant tube was observed to have reached the top of the dressing.

(248) The pump was temporarily stopped at this point whilst the vacuum line was sealed (using a tube clamp) and the vacuum pump stopped.

(249) Timing of the experiment was from the point the irrigation pump was restarted. The pump was run until 50 ml of irrigant has entered the wound model (just over 16 minutes at the rate of 186 ml/hr). At this point the irrigant pump was stopped.

(250) It was observed that during the filling phase of sequential filling and flushing, air trapped in the model wound cavity caused the top film of the dressing to inflate substantially, to a point approaching failure.

(251) After a further ˜44 minutes (60 minutes from the start of the experiment) the vacuum pump was started and the tube clamp on the aspirant line removed. The wound model was aspirated for 5 minutes. Towards the end of this period a small leak was introduced into the top film of the dressing to maximize the amount of fluid drawn from the wound model (it is observed that as the pressure differential between the wound model cavity and the vacuum jar reduced to zero, the flow of aspirant also tended to slow. Introducing a small leak re-established the pressure differential and the flow of aspirant out of the cavity).

(252) Aspirant liquid collected in the vacuum jar was decanted into a glass jar. The vacuum jar was rinsed with ˜100 ml of deionized water and this added to the same glass jar. The aspirant solution was then assayed for the Staphylococcus aureus quantity present.

(253) Results and Conclusions

(254) Simultaneously irrigating and aspirating the wound model removes or kills more of the adherent Staphylococcus aureus on the culture medium sheet placed at the base of the wound model cavity than sequentially filling and emptying the cavity, even though the amount of liquid entering the wound and the duration of the experiment are the same in both cases. Simultaneously irrigating and aspirating also removes more fluid from the model wound.

Example 4

(255) The combination of simultaneous fluid flow (irrigation) with aspiration (under reduced pressure) and actives (PDGF-bb) on wound bed fibroblasts was compared with the exposure of wound bed fibroblasts to repeated fill-empty cycles of fluid flow and aspiration.

(256) An apparatus of the present invention was constructed essentially as in FIG. 38 which is an apparatus where an irrigant or fluid of some nature is delivered continually to the wound bed and the resultant wound exudate/fluid mixture is at the same time continually aspirated from the wound.

(257) Alternative systems are known where the wound is subjected to repeated iteration of a cycle of fluid delivery followed by a period of aspiration under reduced pressure.

(258) The apparatus comprised a surrogate wound chamber (Minucells perfusion chamber) in which normal diploid human fibroblasts were cultured on 13 mm diameter (Thermanox polymer) cover slips retained in a two part support (Minnucells Minusheets). Tissues present in the healing wound that must survive and proliferate were represented by the cells within the chamber. Nutrient medium (DMEM with 10% FCS with 1% Buffer All) to simulate an irrigant fluid/wound exudate mixture, was pumped from a reservoir into the lower aspect of the chamber where it bathed the fibroblasts and was removed from the upper aspect of the chamber and returned to a second reservoir. The wound chamber was maintained at less than atmospheric pressure by means of a Vacuum pump in line with the circuit.

(259) The pumps for the circuit were peristaltic pumps acting on silicone (or equivalent) elastic tubing. The circuit was exposed to a vacuum of no more than 10% atmospheric pressure, 950 mbar and atmospheric pressure varied up to a maximum value of 1044 mbar. The internal diameter of the tubing was 1.0 mm. A total volume for the circuit including the chamber and the reservoir of between 100 and 220 ml was used. The flow rates used were at a number of values between 0.1 ml min.sup.−1 and 2.0 ml.sup.−1 min.sup.−1.

(260) An experiment was conducted that simulated conditions that are not uncommon for healing wounds whereby a fluid was delivered to the wound bed and the application of a vacuum was used to remove the mixture of fluid and exudate to a waste reservoir. An air bleed fluid control valve was additionally positioned in the circuit so that on opening the air bleed occurred for a time and closed the fluid flow, the simulated irrigant fluid/wound exudate mixture was evacuated from the chamber and the chamber left empty and the fibroblasts were maintained under a negative pressure relative to the atmosphere. This represents an empty/fill system, 6 cycles of empty/fill were performed with each fill or empty phase lasting 1 hour.

(261) An experiment was conducted using the following 2 scenarios:

(262) Apparatus was constructed essentially as in FIG. 38 but where a) continuous flow simultaneous aspirate irrigate system with b) material beneficial to wound healing (PDGF-bb) was present in the nutrient flow bathing the cells.

(263) Apparatus was also constructed essentially as in FIG. 38 but a) it was operated as an empty/fill system with 6× cycles of 1 hour empty/1 hour fill over a total of 25 hours with b) the material beneficial to wound healing (PDGF-bb) was present, in the nutrient flow bathing the cells.

(264) Results and Conclusions

(265) The following results were obtained for a circuit comprising a wound chamber as above containing a total volume of nutrient media (104 ml) pumped at a flow rate of 0.2 ml min.sup.−1, and where vacuum was set at 950 mbar and where atmospheric pressure was varied up to a maximum value of 1044 mbar. The wound chamber and media were held at 37° C. for 25 hours. In one set of wound chambers continuous flow was maintained. In a second set of chambers 6 cycles of empty/fill were performed with each fill or empty phase lasting 1 hour.

(266) In controls a) operated as empty/fill with 6 cycles of 1 hour empty/1 hour fill, and b) where PDGF-bb is present, the survival and growth of fibroblasts is inhibited compared to the continuous flow systems.

(267) Where flow circuits consists of a) continuous flow (SIA) and b) PDGF-bb is present the survival and growth of fibroblasts is enhanced to a greater level than empty/fill plus PDGF-bb.

(268) TABLE-US-00002 Mean of cell activity* Conditions after 25 hours. Continuous flow (SIA) plus active (PDGF-bb) 0.34 Fill empty 6 cycles plus active (PDGF-bb) 0.22 *Cell activity measured with a WST (Tetrazolium based mitochondrial dehdrogenase activity assay).

(269) The combination of actives (PDGF-bb) and continuous fluid flow at 0.2 ml min.sup.−1 with waste fluid removal under a vacuum of no more than 10% atmospheric pressure, enhances the cell response necessary for wound healing more than the fill empty system (+PDGF-bb).

Example 5

(270) Using simultaneous irrigate/aspirate (SIA) and sequential irrigate/aspirate (SEQ), the effect of cells as a source of ‘actives’ on fibroblast proliferation was determined.

(271) Method

(272) Cells

(273) Human dermal fibroblasts (HS8/BS04) grown at 37° C./5% CO.sub.2, in T175 flasks containing 35 ml DMEM/10% FCS media were washed in PBS and lifted using 1× trypsin/EDTA (37° C. for 5 min). Trypsin inhibition was achieved by adding 10 ml DMEM/10% FCS media and the cells pelleted by centrifugation (Hereus Megafuge 1.0R; 1000 rpm for 5 min). The media was discarded and cells re-suspended in 10 ml DMEM/10% FCS. Cells were counted using haemocytometer (SOP/CB/007) and diluted in DMEM/10% FCS to obtain 100,000 cells per ml.

(274) Cells (100 μl of diluted stock) were transferred to 13 mm Thermanox tissue culture coated cover slips (Fisher, cat. no. 174950, lot no. 591430) in a 24 well plate and incubated at 37° C. in 5% CO.sub.2 to allow for cell adherence. After 1 h, 1 ml DMEM/10% FCS media was added per well and the cells incubated for approximately 5 hours in the above conditions. Cells were serum starved overnight by removing the DMEM/10% FCS and washing the coverslips with 2×1 ml PBS prior to the addition of 1 ml DMEM/0% FCS.

(275) Following overnight incubation, cells were assessed visually for cell adherence under the microscope and those with good adherence were inserted into cover slip holders for assembly in the Minucell chamber.

(276) Media

(277) Cells were grown in DMEM media (Sigma, cat. no. D6429) supplemented with 5% foetal calf serum; 1-glutamine, non-essential amino acids and penicillin/streptomycin. Media used in the experimental systems was buffered with 1% (v/v) Buffer-All media (Sigma, cat. no. B8405, lot. no. 51k2311) to ensure stable pH of the media.

(278) Minucell Flow Systems

(279) Media (50 ml) was transferred to each bottle prior to the autoclaved systems being assembled. The Minucell chambers were filled with 4 ml media prior to coverslips being inserted. The systems were set-up as shown in FIG. 38, set to run at 0.2 ml/min; hot plates, set to 45° C.; Discofix 3-way valves; vacuum pump, (Ilmvac VCZ 310), set to 950 mbar).

(280) SEQ Systems

(281) Media was pumped through the systems at 0.2 ml/min continuously when the chambers were full. The Minucell chambers were emptied by disconnecting the tubing from the pump and switching the 3-way valve to allow air through an attached 0.22 μm filter. When fully emptied, the 3-way valve was switched to close the system between the valve and the pump and so allowing the formation of a vacuum in the system. Elevation of the 3-way valve ensured media did not pass through the 0.22 μm filter by gravity flow. After 1 h, the 3-way valve was switched back to the starting position to allow the Minucell chamber to fill and the tube reconnected to the pump. The SEQ systems were treated as per the following table.

(282) Fill/Empty Regime for SEQ Systems:

(283) TABLE-US-00003 Time (h) 0 1 2 3 4 5 6 7 8 20 21 22 23 24 Empty/fill F E F E F E F E F E F E W A F = full chamber/flowing; E = empty chamber/under vacuum; W = remove coverslips for WST assay; A = read WST assay result.

(284) SIA Systems

(285) Continuous irrigate aspirate systems were run for 24 h with media irrigating the cells and being aspirated under vacuum set to 950 mbar. The atmospheric pressure varied daily, up to a maximum value of 1048 mbar, therefore the difference in pressure between the systems and the atmosphere was always under 10%.

(286) Cells as Actives Component

(287) The ‘cells as actives’ component of the flow cell system was provided by Dermagraft (a fibroblast seeded Vicryl mesh). Dermagraft stored at −70° C. was defrosted by placing in a 37° C. water-bath for 1 min and washed ×3 with 50 ml 0.9% v/v NaCl. The Dermagraft was cut into 24×1.1 cm.sup.2 squares using a sterile clicker-press and placed into DMEM/5% FCS. For the flow-cell experiments, a number of Dermagraft squares were placed in Media 1 bottle (FIG. 1) immediately prior to the start of the experiment. The presence of live cells in the Dermagraft squares was determined by WST assay when the experiment was terminated.

(288) WST Assay

(289) A WST assay to measure cell mitochondrial activity was performed on the coverslips. WST reagent (Roche, cat. no. 1 644 807, lot no. 11264000) was diluted to 10% v/v in DMEM/10% FCS. The coverslips (n=6) were removed from each Minucell chamber and washed in 1 ml PBS. PBS was removed and 200 μl WST/DMEM media added. The coverslips were then incubated at 37° C. for 45 min before transferring 150 μl to a 96 well plate. The absorbance at 450 nm with reference at 655 nm was determined using Ascent Multiskan Microtitre plate reader.

(290) The mitochondrial activity of cells grown in SIA and SEQ systems, with or without ‘cells as actives’ component was determined using the WST assay. The optimal number of Dermagraft squares required was first assessed in a SIA flow cell system. Addition of Dermagraft squares to the media had a beneficial effect, increasing the proliferation rate of seeded fibroblasts (FIG. 39). There was a slight benefit to increasing the number of Dermagraft squares from 3 to 6, although increasing the amount of Dermagraft to 11 squares did not further increase the rate of proliferation. Therefore, for the flow cell experiments, 6 Dermagraft squares were placed in the relevant media bottles. The experiments to show the optimal number of Dermagraft squares also showed that the addition of cells as a source of actives, to the SIA systems, resulted in an increased rate of proliferation (FIG. 39).

(291) Results and Conclusions

(292) Treatment of fibroblasts by the addition of ‘cells acting as a source of actives’ to the media, increased the rate of proliferation in SIA and the SEQ systems after 24 hours (FIGS. 39 & 40).

(293) This beneficial effect was observed in both SAI and the SEQ flow systems.

Example 6

(294) Method

(295) Cells

(296) Human dermal fibroblasts (HS8/BS04) grown at 37° C./5% CO.sub.2, in T175 flasks containing 35 ml DMEM/10% FCS media were washed in PBS and lifted using 1× trypsin/EDTA (37° C. for 5 min). Trypsin inhibition was achieved by adding 10 ml DMEM/10% FCS media and the cells were pelleted by centrifugation (Hereus Megafuge 1.0R; 1000 rpm for 5 min). The media was discarded and cells re-suspended in 10 ml DMEM/10% FCS. Cells were counted using a N haemocytometer (SOP/CB/007) and diluted in DMEM/10% FCS to obtain 100,000 cells per ml.

(297) Cells (100 μl of diluted stock) were transferred to each 13 mm Thermanox tissue culture coated cover slip (cat. 174950, lot 591430) in a 24 well plate and incubated for 1 hr at 37° C./5% CO.sub.2 to allow cell adherence. After 1 h, 1 ml DMEM/10% FCS media was added per well. After 6 h, the media was removed, cells washed with 2×1 ml PBS and 1 ml DMEM/0% FCS added per well and the cells incubated overnight in the above conditions.

(298) Following overnight incubation, cells were assessed visually for growth under the microscope and those with growth were inserted into cover slip holders (Vertriebs-Gmbh, cat no. 1300) for assembly in the Minucell chamber (Vertriebs-Gmbh, Cat no. 1301).

(299) Media

(300) Cells were grown in DMEM media (Sigma, no. D6429) supplemented with 10% foetal calf serum; 1-glutamine, non-essential amino acids and penicillin/streptomycin. Media used in the experimental systems was supplemented with 5% (v/v) foetal calf serum and buffered with 1% (v/v) Buffer-All media (Sigma, lot 51k2311) to ensure stable pH of the media.

(301) Minucell Flow Systems

(302) Systems (5) were made up as per FIG. 32.

(303) TABLE-US-00004 Bottle 1 Bottle 2 System 1 Media Media System 2 Media Media and 6 Dermagraft squares System 3 Media + catalase Media System 4 Media + H.sub.2O.sub.2 Media + Dermagraft System 5 Media + catalase + H.sub.2O.sub.2 Media + Dermagraft

(304) Equipment used in the flow system was Ismatec IPC high precision peristaltic pumps with Ismatec pump tubing 1.02 mm ID and high strength silicon tubing (HS-0152-009, Cole Palmer Instruments) and hot plates (asset number 6531 and 6532).

(305) Catalase

(306) Snakeskin pleated dialysis tube (10 kDa MWCO; Pierce, no. 68100, lot EB9446) containing 15 ml catalase (or 86200 units; Sigma, C3155, lot 014K7029). The dialysis tubing was placed in Media 1 bottle.

(307) H.sub.2O.sub.2

(308) Hydrogen peroxide (Sigma, lot 074K3641; stock 8.8M, 30% soln) (250 μl) added to 21.75 ml DMEM/5% FCS media. 5.1 ml of the media added to 39.9 ml DMEM/5% FCS media and 5 ml of this was added to bottle 1 of the relevant systems giving a final concentration of 1.1 mM.

(309) Hydrogen peroxide (H.sub.2O.sub.2) was used to mimic the chronic wound element, as it is a reactive oxygen species that causes oxidative stress to cells. The enzyme catalase is a natural antioxidant that degrades H.sub.2O.sub.2 into water and oxygen protecting cells against oxidative damage to proteins, lipids and nucleic acids. So, it was placed in dialysis tubing to mimic exudialysis. A source of cells as a source of actives was provided by using Vicryl mesh seeded with live fibroblast cells [Dermagraft]. The experiment ran for a total of 48 hours. A WST assay was used to measure fibroblast activity after 48 hours.

(310) Cells as a Source of Actives

(311) The ‘cells as a source of actives’ was fibroblasts seeded on a Vicryl mesh (Dermagraft, Smith and Nephew). Dermagraft was defrosted in a water bath at 37° C. for 1 minute and the cryoprotectant removed. The Dermagraft was washed with 3×50 ml 0.9% saline and cut into 1.1 cm squares using the clickerpress. 6 squares of Dermagraft were placed in bottle 2 of the systems described above. The final volume of media was made up to 50 ml in bottle 1 and bottle 2.

(312) WST Assay

(313) A WST assay to measure the cells mitochondrial activity was performed on 6 coverslips from each system. WST reagent (Roche, lot 102452000) was diluted to 10% v/v in DMEM/10% FCS/buffer all media. The coverslips were removed from the Minucell chamber and washed in 1 ml PBS. PBS was removed and 200 μl WST/DMEM media added. The coverslips were then incubated at 37° C. for 45 min before transferring 150 μl of reagent to a 96 well plate. The absorbance at 450 nm with reference at 655 nm was determined using Ascent Multiskan Microtitre plate reader.

(314) The mitochondrial activity of cells grown in exudialysis systems, with or without ‘cells as actives’ component was determined using the WST assay. The WST activity of individual experiments is shown in FIGS. 33 and 34, with the average WST activity represented by the bar and standard deviation by the error bars.

(315) From the data in FIG. 33 it is possible to see that the addition of Dermagraft (Dg) (the source of actives from live cells) resulted in an increased fibroblast activity, as measured by the WST assay.

(316) Fibroblast activity within the Dermagraft squares was shown by assaying a number of Dermagraft squares from the media at the end of the experimental incubation period. Dermagraft activity was in the range 0.17 to 0.95 and was therefore alive.

(317) From the data in FIG. 34 it is possible to see that with the addition of exudialysis (+catalase) resulted in an increased fibroblast activity over the control of media only (TCM).

(318) This graph (FIG. 34) also showed that the presence of H.sub.2O.sub.2 Hydrogen Peroxide even with Dermagraft (Dg) had no fibroblast activity. Thus in the absence of a removal system hydrogen peroxide, a source of toxic reactive oxygen species, kills the fibroblasts seeded on the coverslip and in the Dermagraft.

(319) In contrast, the data shows for, the actives from live cells (Dg) with Exudialysis (+catalase) even with Hydrogen Peroxide (H.sub.2O.sub.2) a significant increase in fibroblast activity, as measured by the WST assay over the media only control, the hydrogen peroxide control and media and exudialysis result.

(320) This increase was also greater than with media and actives from live cells (FIG. 33).

(321) Results and Conclusions

(322) It is possible to see an increase fibroblast growth activity when the cells are in the flow system in conjunction with the live cells providing a source of actives along with the exudialysis system which removes the ‘chrome wound element’ from the media.

Example 7

(323) The benefit of using cells as a cleanser in the Exudialysis systems can be demonstrated.

(324) Method

(325) Cells

(326) Human dermal fibroblasts (HS8/BS04) would be prepared for growth on Thermanox coverslips.

(327) Media

(328) Cells to be grown in DMEM media (Sigma, no. D6429) supplemented with 10% foetal calf serum; 1-glutamine, non-essential amino acids and penicillin/streptomycin (various lot numbers). Media to be used in the experimental systems is supplemented with 5% (v/v) foetal calf serum and buffered with 1% (v/v) Buffer-All media (Sigma) to ensure stable pH of the media. Alternatively, cells will be grown in Eagle MEM media supplemented with 2 mM glutamate, 1.5 g/L sodium bicarbonate, 0.1 mM NEAA and 1 mM sodium pyruvate. The Eagle MEM media is the recommended media type for hepatocyte cell line.

(329) Cells as Cleanser Aspect

(330) Hepatocyte cell line (for example HepG2/C3A cell line; ATCC, ATCC-CRL-10741) would be used as the cells to remove factors deleterious to wound healing (e.g. hydrogen peroxide) from the media. The cell line would be grown either on a synthetic matrix (e.g. nylon mesh) or possibly a non-synthetic matrix and placed within the exudialysis system either enclosed in a dialysis type membrane or free floating in the media bottle.

(331) Exudialysis System

(332) A number of systems would be made up to provide the relevant controls and test conditions. These would include:

(333) TABLE-US-00005 Bottle 1 Bottle 2 System 1 Media Media System 2 Media Media and hepatocytes System 3 Media + catalase Media System 4 Media + H.sub.2O.sub.2 Media + hepatocytes System 5 Media + H.sub.2O.sub.2 Media

(334) Equipment used in the flow system would include Ismatec IPC high precision peristaltic pumps with Ismatec pump tubing 1.02 mm ID and high strength silicon tubing (HS-0152-009, Cole Palmer Instruments) and hot plates.

(335) H.sub.2O.sub.2

(336) Hydrogen peroxide (Sigma, lot 074K3641; stock 8.8M, 30% soln) (250 μl) added to 21.75 ml DMEM/5% FCS media (or Eagle MEM media). 5.1 ml of the media added to 39.9 ml DMEM/5% FCS media and 5 ml of this was added to bottle 1 of the relevant systems giving a final concentration of 1.1 mM.

(337) Catalase

(338) Catalase is to be used as a positive control. Snakeskin pleated dialysis tube (10 kDa MWCO; Pierce, no. 68100, lot EB9446) containing 15 ml catalase (or 86200 units; Sigma, C3155, lot 014K7029). The dialysis tubing was placed in Media bottle.

(339) WST Assay

(340) A WST assay would be used to measure the cells mitochondrial activity was on 6 coverslips from each system. WST reagent (Roche) is diluted to 10% v/v in experimental/Buffer All media. The coverslips are removed from the Minucell chamber and washed in 1 ml PBS. PBS was removed and 200 μl WST/media added. The coverslips would then incubated at 37° C. for 45 min before transferring 150 μl of reagent to a 96 well plate. The absorbance at 450 nm with reference at 655 nm is determined using Ascent Multiskan Microtitre plate reader.

(341) It would be expected that hepatocyte cells would convert and detoxify hydrogen peroxide to oxygen and water through the action of catalase, which is reported to be a protein component of hepatocytes. Through the detoxification action of hepatocytes, the fibroblasts present in the wound bed will survive and proliferate to a greater extent than to those exposed to hydrogen peroxide alone. Previous experiments have shown the presence of hydrogen peroxide kills the seeded fibroblasts (FIG. 35).

(342) Results and Conclusions

(343) Hydrogen peroxide, at a sufficient concentration is toxic to fibroblast cells.

(344) A major role of hepatocytes is to detoxify biological fluids through enzymatic (e.g. catalase) mechanisms.

(345) By placing hepatocyte cells within a flow system it would be expected that the hepatocytes would detoxify the media and remove hydrogen peroxide to a sufficient level to enable the fibroblasts present to survive and proliferate.

(346) While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made without departing from the spirit of the disclosure. Additionally, the various features and processes described above may be used independently of one another, or may be combined in various ways. All possible combinations and subcombinations are intended to fall within the scope of this disclosure. Many of the embodiments described above include similar components, and as such, these similar components can be interchanged in different embodiments.

(347) Although the invention has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses and obvious modifications and equivalents thereof. Accordingly, the invention is not intended to be limited by the specific disclosures of preferred embodiments herein.