Combined negative pressure treatment and drainage

Abstract

A combined apparatus for delivering negative pressure to a tissue site for treatment and to a drainage site to drain fluids. Various configurations of pumps and valves are disclosed to allow the delivery of negative pressure wound treatment to a tissue site as well as drainage suction to a different location on the patient.

Description

PA200074W002COMBINED NEGATIVE PRESSURE TREATMENT AND DRAINAGECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 777,155, filed on March 25, 2025, which is incorporated herein by reference in its entirety.TECHNICAL FIELD

[0002] The following disclosure relates to negative pressure wound treatment systems with wound drainage, and in particular to a combined apparatus for negative pressure wound therapy and wound drainage.BACKGROUND

[0003] Negative pressure wound therapy is a well-known method of treating patients by reducing the pressure over a tissue site to below atmospheric pressure. Negative pressure systems generally supply negative pressure to the tissue site from a pump unit having a negative pressure source.

[0004] During treatment of tissue sites, principally following surgery, it is often necessary or desirable to drain subcutaneous spaces of the body close to, or associated with, the tissue site which is being treated with negative pressure therapy. For example, in addition to a tissue site being treated at the surface of the patient there may be subcutaneous areas which require draining during healing. For example, following surgery the tissue site may be a closed incision, and subcutaneous drainage may be utilised to drain fluids which are accumulating under the skin.

[0005] Such drains are conventionally implemented using a JP -drain which consists of a drain tube with an end positioned subcutaneously at the location to be drained, and a manual vacuum bulb at the other end of the tube, external to the body, which can be pumped to generate negative pressure to assist drainage.

[0006] Such drainage systems are often inconvenient as they require manual pumping to maintain the negative pressure and can be inconvenient for a patient due to the components attached to the body. Gravity or passive drains may also be used which can also be inefficient as they rely on natural flow of liquids.

[0007] There is therefore a need for an improved system for treating a patient with negative pressure wound therapy and wound drainage.BRIEF SUMMARY

[0008] Aspects of the disclosure are set out in the following numbered clauses.

[0009] 1. A combined negative pressure treatment and drainage system, comprising a source of negative pressure; a splitter having an inlet fluidly coupled to the source of negative pressure by asource fluid path, a first outlet fluidly coupled to a treatment fluid path for fluidly coupling to a tissue site and a second outlet fluidly coupled to a drainage fluid path for fluidly coupling to a drainage site; and a negative pressure regulator positioned in the drainage fluid path to regulate the negative pressure at an outlet of the drainage fluid path.

[0010] 2. A combined negative pressure treatment and drainage system according to clause 1, wherein the negative pressure regulator regulates the pressure at its outlet to a predetermined value.

[0011] 3. A combined negative pressure treatment and drainage system according to clause 1, wherein the negative pressure regulator regulates the pressure at its outlet to a level which is a predetermined amount less than the negative pressure at its inlet.

[0012] 4. A combined negative pressure treatment and drainage system according to any preceding clause, further comprising a treatment container forming part of the source fluid path, the container being for collecting liquids from the tissue site and drainage site.

[0013] 5. A combined negative pressure treatment and drainage system according to any of clauses 1 to 3, wherein the splitter is a container for collecting liquids from the tissue site, and wherein the input of the negative pressure regulator is fluidly coupled to the treatment container.

[0014] 6. A combined negative pressure treatment and drainage system according to clause 5, further comprising a drainage container forming part of the drainage fluid path between the negative pressure regulator and the drainage site.

[0015] 7. A combined negative pressure treatment and drainage system according to clause 6 wherein the source of negative pressure is located in a pump unit, and the drainage container and the treatment container are each separately releasably attachable to the pump unit.

[0016] 8. A combined negative pressure treatment and drainage system according to any of clauses 1 to 3, wherein the treatment fluid path comprises a container for collecting liquids from the tissue site, and the drainage fluid path comprises a container for collecting liquids from the drainage site.

[0017] 9. A combined negative pressure treatment and drainage system according to clause 8, wherein the splitter and negative pressure regulator are positioned in a pump unit.

[0018] 10. A combined negative pressure treatment and drainage system according to clause 9 wherein the drainage container and the treatment container are each separately releasably attachable to the pump unit.

[0019] 11. A combined negative pressure treatment and drainage system, comprising a source of negative pressure; a 3-port fluid valve, an input of the valve being fluidly coupled to the source of negative pressure, a first outlet of the valve being fluidly coupled to a treatment fluid path for fluidly coupling to a tissue site, and a second outlet of the valve being fluidly coupled to a drainage fluid path for fluidly coupling to a drainage site; a pressure sensor for monitoring the pressure at the input of the 3-port valve; and a controller configured to control the 3-port valve and the source of negative pressure based at least in part on the pressure sensor.

[0020] 12. A combined negative pressure treatment and drainage system according to clause 11, wherein the controller is configured to control the source of negative pressure and valve to alternately reduce the pressure of the treatment fluid path and the drainage fluid path to different predetermined levels.

[0021] 13. A combined negative pressure treatment and drainage system according to clause 12, wherein the predetermined level for the drainage fluid path is less than the predetermined level for the treatment fluid path.

[0022] 14. A combined negative pressure treatment and drainage system according to any of clauses 11 to 13, wherein the treatment fluid path comprises a treatment container for collecting liquid from the tissue site, and the drainage fluid path comprises a drainage container for collecting liquid from the drainage site.

[0023] 15. A combined negative pressure treatment and drainage system according to clause 14 wherein the source of negative pressure, valve, pressure sensor and controller are positioned in a pump unit, and the drainage container and the treatment container are each separately releasably attachable to the pump unit.

[0024] 16. A method of applying negative pressure to a tissue site for treatment and to a drainage site for drainage, the method comprising the steps of configuring a fluid valve to fluidly couple a source of negative pressure to the tissue site, operating the source of negative pressure to deliver a first predetermined level of negative pressure to the tissue site; configuring the fluid valve to couple the source of negative pressure to the drainage site; and operating the source of negative pressure to deliver a second predetermined level of negative pressure to the drainage site, wherein the first and second predetermined levels of negative pressure are different.

[0025] 17. A method according to clause 16, comprising cycling the steps of clause 16 according to a predetermined schedule.

[0026] 18. A method according to clause 16, comprising cycling the steps of clause 16 according to a schedule based on the speed of reduction of negative pressure at the tissue site and / or the drainage site.BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 shows a schematic block diagram of a negative pressure treatment system;

[0028] Figure 2 shows a schematic block diagram of a combined negative pressure and drain system;

[0029] Figure 3 shows a schematic diagram of a system for delivering combined negative pressure therapy and drainage using a single canister;

[0030] Figure 4 shows a schematic diagram of a system for delivering combined negative pressure therapy and drainage using separate canisters;

[0031] Figure 5 shows a schematic diagram of a system for delivering combined negative pressure therapy and drainage using separate canisters and an internal pressure regulator;

[0032] Figure 6 shows a schematic diagram of a system for delivering combined negative pressure therapy and drainage using a controlled fluid valve; and

[0033] Figure 7 is a block diagram of components of a pump unit.DESCRIPTION OF EXAMPLE EMBODIMENTS

[0034] The following description of examples provides information that enables a person skilled in the art to make and use the subject matter set forth in the appended claims, but it may omit certain details already well-known in the art. The following detailed description is, therefore, to be taken as illustrative and not limiting.

[0035] Figure 1 is a block diagram of an example therapy system 100 that can provide negativepressure therapy with instillation of topical treatment solutions to a tissue site in accordance with this specification.

[0036] The term “tissue site” in this context broadly refers to a wound, defect, or other treatment target located on or within tissue, including, but not limited to, bone tissue, adipose tissue, muscle tissue, neural tissue, dermal tissue, vascular tissue, connective tissue, cartilage, tendons, or ligaments. In a particular example a tissue site may be an area of the body which has been treated surgically. A wound may include chronic, acute, traumatic, subacute, and dehisced wounds, partial thickness bums, ulcers (such as diabetic, pressure, or venous insufficiency ulcers), flaps, and grafts, for example. The term “tissue site” may also refer to areas of any tissue that are not necessarily wounded or defective but are instead areas in which it may be desirable to add or promote the growth of additional tissue. For example, negative pressure may be applied to a tissue site to grow additional tissue that may be harvested and transplanted. The surface of the patient within the tissue site being treated will be referred to as the tissue site bed.

[0037] The therapy system 100 includes a negative-pressure source 102, a dressing 104, and a container 106. The dressing 104 comprises a tissue interface 108 and a cover 110 such that negative pressure can be coupled from the negative pressure source 102 and maintained at the tissue site under the cover 110. The tissue interface 108 is optional but typically comprises a manifold to distribute negative pressure and fluids across the tissue site bed and facilitate removal of fluids from the tissue site. The tissue interface 108 may be an open cell foam. The tissue interface 108 may be sized and shaped to fit the contours of the tissue site or may be compressed to fit the tissue site and held in place by the cover 110. The cover is typically an elastomeric self-adhesive film, for example a polyurethane film, and is typically formed of a breathable, but liquid impermeable, material.

[0038] The therapy system 100 may also include a controller 112 to control delivery of negative pressure by the negative pressure source 102. A first pressure sensor 114 may be included to detect pressure in the container 106, and a second pressure sensor 116 may be included to detect the pressure delivered by the negative pressure source 102. These pressure sensors 114, 116 may be utilised by the controller 112 to control the negative pressure source 102. Other sensors may also be provided to monitor operating parameters of the system.

[0039] The therapy system 100 may also include a source of instillation solution. For example, a solution source 118 may be fluidly coupled to the dressing 104 and a pump 120 may be utilised to transfer liquid from the source 118 to the dressing 110. An instillation regulator 122 may be provided to control instillation of liquid. The instillation may also be controlled by controller 112.

[0040] The components of therapy system 100 may be combined into integrated elements and may be co-packaged or provided separately.

[0041] The controller 112 comprises a microprocessor or computer programmed to operate one or more components of the therapy system 100, such as the negative pressure source 102. The controller 112 may be a microcontroller, which generally comprises an integrated circuit containing a processor core and a memory programmed to directly or indirectly control the one or more elements of the therapy system 100. A function of the controller 112 is to control the negative pressure source 102 to deliver the desired negative pressure to the tissue site for which signals from one or more of the pressure sensors 114, 116 may be utilised in addition to settings made by the user.

[0042] In operation, the tissue interface 108 is placed within, over, on, or otherwise proximate to a tissue site and may partially or completely fill the tissue site. The cover 110 is placed over the tissue interface 108 and sealed to an attachment surface near a tissue site. For example, the cover 110 may be sealed to undamaged tissue (e.g. epidermis) peripheral to the tissue site. Thus, the dressing 104 can provide a sealed therapeutic environment proximate to the tissue site, substantially isolated from the external environment, and the negative-pressure source 102 can reduce pressure in the sealed therapeutic environment.

[0043] In conventional negative pressure systems, the negative pressure at the tissue site may be monitored using a pressure sensor located to sense pressure at the pump unit such as the first sensor 114 discussed above. The first sensor 114 may be fluidly coupled to the tissue site either via the same lumen used to apply negative pressure to the tissue site, or via a separate lumen which is coupled to the tissue site, for example by using a multi-lumen conduit. The accuracy of such an arrangement can be limited due to the presence of liquid in the lumen between the sensor and the tissue site.Furthermore, the actual pressure at the point of coupling into the tissue site may be different to the pressure at the tissue site bed. In the example Figure 1, the second pressure sensor 116 may be fluidly coupled directly to the tissue site, or located at the tissue site, to allow measurement of pressure at the tissue site.

[0044] As will be appreciated only selected components have been shown and described in relation to Figure 1 to explain the principles of operation and construction of the treatment system, but other components may also be present in a complete system.

[0045] Figure 2 shows a schematic diagram of a combined negative pressure treatment and drain system 200, based upon the system of Figure 1, with the same reference numerals being used for comparable components. Conduit 202 from container 206 is fluidly coupled to splitter 204, rather than directly to the dressing 104 as with Figure 1. Splitter 204 couples the lumen of conduit 202 tothe lumens of treatment conduit 208 and drain conduit 210. That is, the outlet of container 206 is connected to both conduits 208, 210 such that negative pressure is delivered to treatment conduit 208 and drain conduit 210. Similarly, fluids withdrawn from dressing 104 and drainage site 212 flow through the relevant conduits and components to be collected in container 206. Treatment conduit 208 is fluidly connected to dressing 104 as described in relation to Figure 1. Drain conduit 210 is fluidly coupled to pressure regulator 214, the output of which is a further conduit for fluidly coupling to the drainage site 212.

[0046] The system of Figure 2 can accordingly deliver negative pressure to both a tissue site for treatment and to a drainage site for drainage and can collect fluids, particularly liquids, extracted from the dressing and the drainage site.

[0047] Pressure regulator 214 regulates the pressure delivered to the drainage site 212. Such a regulator is required because drainage typically uses lower negative pressures (i.e. less negative compared to atmospheric pressure) than negative pressure wound treatment. The negative pressure regulator 214 may regulate its outlet pressure to a predetermined level or may reduce the negative pressure at its inlet by a predetermined amount. In the first option the pressure at the drainage site is independent of the pressure at the outlet of the container 206 (providing the pressure at the inlet to regulator 214 is greater than the predetermined outlet pressure), whereas in the second option the pressure at the drainage site will vary as the pressure at the outlet of the container varies.

[0048] Valves such as duckbill valves may be suitable for use as a pressure reducing valve. In such valves the amount of pressure reduction can be defined by the geometry and materials of the valve and may be user-adjustable. Similarly spring-loaded pressure reducing valves may be utilised. Any suitable negative pressure regulator may be used to provide an outlet negative pressure regulated to a predetermined level.

[0049] Some valves, such as duck bill valves, may also function one-way valves to prevent flow of fluids in undesired directions. A one-way valve may also be provided in treatment conduit 208 and / or drain conduit 210 to prevent flow of fluids, particularly exudates, towards the tissue site 104 or drainage site 212.

[0050] As will be appreciated materials (including liquids such as exudate) extracted from the drainage site pass through the regulator 214 and so a suitable valve should be selected to ensure continued operation when materials other than gasses are passing through the valve.

[0051] In an example, the negative pressure delivered to the tissue site may be -125mmHg, and the pressure delivered to the drainage site may be -75mmHg. The pressure delivered to the tissue site may be controlled using known techniques, as discussed in relation to Figure 1.

[0052] In use, the drainage site 212 and dressing 104 are fluidly isolated from each other and therefore the different negative pressures delivered to those locations do not interact.

[0053] Figure 3 shows a schematic diagram of a negative pressure treatment system 300 for implementing the principles of the system of Figure 2. The system 300 comprises a therapy unit 302for providing negative pressure to a container 304. The therapy unit 302 comprises a pump 306 for delivering negative pressure to the container 304 via lumen 308. An optional pressure sensor 310 monitors the pressure delivered by the pump 306, either at lumen 308 or in the container 304. A further optional pressure sensor 312 may be provided to monitor pressure at the tissue site via a sensing lumen 314. The pump 306, and other aspects of the therapy unit 302 are controlled by a controller 316 based on user input and measurements from pressure sensors 310, 312 (if they are present).

[0054] A purge system 318 may also be provided to allow air to enter the lumen 314 to purge blockages or change the wound pressure towards atmospheric pressure.

[0055] Lumen 320, fluidly coupled to the container 304, is connected to splitter 322 which splits the negative pressure in conduit 320 to treatment conduit 324 and drain conduit 326. Treatment conduit 324 couples negative pressure to a dressing located at tissue site 328 in the conventional manner. Drain conduit 326 is coupled to regulator 330, which is a negative pressure regulator functioning as described in relation to element 214 of Figure 2. Conduit 332 fluidly coupled to the outlet of regulator 330 is for coupling negative pressure to the drainage site.

[0056] Splitter 322 may be provided using any appropriate element. For example, a Y-branch could be formed between 1 inlet and 2 outlet tubes, or a coupling device could be utilised. As mentioned in relation to Figure 2, one or more one-way valves may be provided in conjunction with splitter 322 to prevent flow of fluid towards the tissue site 324 and drainage site through conduits 324 and 326. Where sensing lumen 314 is provided as part of a multi-lumen conduit with conduit 320 the splitter 322 is configured to couple the sensing lumen 314 to a sensing lumen of treatment conduit 324 such that the pressure at the tissue site can be monitored.

[0057] In an alternative construction the splitter 322 may be provided as part of the container 304 such that two conduits are provided from the container or two connection points are provided to connect to conduits 324, 326 for use.

[0058] A liquid barrier may be provided within the container 304 to prevent liquid leaving the container 304 to avoid contamination of the pump unit.

[0059] Figure 4 shows a schematic diagram of a combined negative pressure treatment and drainage system 400. Many components are equivalent to those of Figure 3 and accordingly the same reference numerals have been utilised where appropriate. In the example of Figure 4, two containers 404, 406 are provided. A first container 404 receives negative pressure from lumen 308 and is fluidly connected to a dressing located at a tissue site 408 by treatment conduit 410. A second container 406 is fluidly connected to the first container 404 via negative pressure regulator 428. Second container 406 is fluidly connected to drain conduit 412 for coupling to a drainage site of a patient. The system of Figure 4 can therefore deliver negative pressure to both a tissue site 408 and a drainage site. The pressure delivered to the tissue site 408 is regulated by pump unit 402 as described hereinbefore, and the pressure delivered to the drain site is regulated by negative pressure regulator 428. As withnegative pressure regulator 330 the negative pressure regulator 428 may regulate pressure in container 406 to a predetermined value or may provide a reduction compared to the pressure in container 404. All discussion of negative pressure regulator 330 applies equally to negative pressure regulator 428.

[0060] The system of Figure 4 has separate containers 404, 406 for collecting fluids, particularly liquid exudates, from the tissue site and drain site. This may be convenient to allow monitoring of liquid extracted from each site. The containers 404, 406 may be configured such that they can be replaced individually should one of them become full before the other, or they may be provided as a unitary component.

[0061] Since liquid from the drain site is collected in container 406 regulator 428 may not be required to pass liquids. A liquid-barrier, for example a hydrophobic filter, may be provided on one or both sides of the regulator 428 to protect the regulator from liquids which could interfere with its operation. This protection may enable different regulators to be utilised which are not suitable for use in the system of Figure 3. Certain forms of liquid-barrier, such as hydrophobic filters, create a pressure drop. The regulator 428 and liquid-barrier could therefore by combined into a single entity to block liquids and provide the pressure regulation function.

[0062] A liquid barrier may be provided within the container 404 to prevent liquid leaving the container 404 to avoid contamination of the pump unit.

[0063] Figure 5 shows a variation of the system of Figure 4. In the system 500 of Figure 5 lumen 508 splits negative pressure between container 504 and negative pressure regulator 528. The outlet of regulator 528 is fluidly coupled to container 506. Container 506 is fluidly coupled to drain conduit 512 to deliver negative pressure to the drain site in the same manner as previous examples.Functionally the system of Figure 5 is the same that of Figure 4, but the negative pressure is coupled from lumen 508 to drain container 506 via regulator 528 within the pump unit, rather than via the container 504. This arrangement may be advantageous because the regulator 528 can be used for the life of pump unit 502, rather than being changed when canisters are changed. Furthermore, the arrangement may allow the containers 504, 506 to be more easily changed independently of each other.

[0064] A liquid barrier may be provided within the container 506 to prevent liquid leaving the container to avoid contamination of the regulator 528 and other components in the pump unit 504 and also within container 504 to prevent liquid from the tissue site 508 contaminating the pump unit 502.

[0065] Figure 6 shows a further variation of a system 600 for combined negative pressure wound treatment and drainage. In this example the output lumen 608 of pump 306 is coupled to the common port 602 a 3 -port valve 610. A first switched port 614 of the valve 610 is fluidly coupled to wound treatment container 604 and a second switched port 612 of valve 610 is fluidly coupled to drainage container 606. The valve 610 is controlled by controller 616 to connect the pump 306 to either container 604 or container 606. The pump and pressure sensor 310 can thus be utilised to deliver a predetermined negative pressure to each container independently. The arrangement of Figure 6 maythus provide increased control of the negative pressure delivered to each of the tissue site and drain site. In operation delivery of negative pressure may be switched between each container according to a specified protocol, for example at preset time intervals.

[0066] The valve 610 may switch to a container, the controller 616 measures the negative pressure using pressure sensor 310 in that container and, if necessary, runs pump 306 to reduce the pressure in the respective container to a predetermined value. The valve 610 is then switched to the other container and the process repeated.

[0067] While the pump 306 is delivering negative pressure one container the other container’s pressure will decrease towards atmospheric pressure at a rate dependent on the system configuration, rate of exudation, and leaks into the system. The controller 616 may be configured to learn the rate at which negative pressure decreases in each container and the period at which the valve is switched may be adjusted accordingly such that each pressure remains within a predetermined range. For example, the controller 616 may adjust the negative pressure in the treatment container to -125mmHg and aim for it not to fall below -lOOmmHg. Similarly, the pressure in drain container 606 may be adjusted to -75mmHg with an aim of it not falling below -50mmHg. These values are given for example only and any suitable values may be utilised.

[0068] A liquid barrier may be provided within one, or both, of the containers 604 and 606 to prevent liquid leaving the respective container to avoid contamination of the pump unit.

[0069] Figure 7 shows a simplified schematic diagram of the electronic elements of a pump unit 900. The components included in Figure 9 are selected to explain the general structure and configuration of the system by reference to the main elements such that the skilled person can implement the examples using known techniques. The pump unit 900 comprises a negative pressure pump 904 for supplying negative pressure to a tissue site via a suitable fluidic connection. The pump 904 is controlled by processor 906 based on settings made by the user via user interface 908, data held in memory 910, programming executed by the processor 906, sensors 912 (for example the ambient pressure sensor discussed hereinbefore), and measurements received via communications interface 914 from a pressure sensor device 902. Communications interface 914 is a wireless communication interface capable of establishing a wireless connection to remote wireless devices.

[0070] While shown in a few illustrative embodiments, a person having ordinary skill in the art will recognize that the systems, apparatuses, and methods described herein are susceptible to various changes and modifications that fall within the scope of the appended claims. Moreover, descriptions of various alternatives using terms such as “or” do not require mutual exclusivity unless clearly required by the context, and the indefinite articles “a” or “an” do not limit the subject to a single instance unless clearly required by the context. Components may also be combined or eliminated in various configurations for purposes of sale, manufacture, assembly, or use.

[0071] The appended claims set forth novel and inventive aspects of the subject matter described above, but the claims may also encompass additional subject matter not specifically recited in detail.For example, certain features, elements, or aspects may be omitted from the claims if not necessary to distinguish the novel and inventive features from what is already known to a person having ordinary skill in the art. Features, elements, and aspects described in the context of some embodiments may also be omitted, combined, or replaced by alternative features serving the same, equivalent, or similar purpose without departing from the scope of the invention defined by the appended claims.

Claims

Claims1. A combined negative pressure treatment and drainage system, comprisinga source of negative pressure;a splitter having an inlet fluidly coupled to the source of negative pressure by a source fluid path, a first outlet fluidly coupled to a treatment fluid path for fluidly coupling to a tissue site and a second outlet fluidly coupled to a drainage fluid path for fluidly coupling to a drainage site; anda negative pressure regulator positioned in the drainage fluid path to regulate the negative pressure at an outlet of the drainage fluid path.

2. A combined negative pressure treatment and drainage system according to claim 1, wherein the negative pressure regulator regulates the pressure at its outlet to a predetermined value.

3. A combined negative pressure treatment and drainage system according to claim 1, wherein the negative pressure regulator regulates the pressure at its outlet to a level which is a predetermined amount less than the negative pressure at its inlet.

4. A combined negative pressure treatment and drainage system according to claim 1, further comprising a treatment container forming part of the source fluid path, the container being for collecting liquids from the tissue site and drainage site.

5. A combined negative pressure treatment and drainage system according to claim 1, wherein the splitter is a container for collecting liquids from the tissue site, and wherein the input of the negative pressure regulator is fluidly coupled to the treatment container.

6. A combined negative pressure treatment and drainage system according to claim 5, further comprising a drainage container forming part of the drainage fluid path between the negative pressure regulator and the drainage site.

7. A combined negative pressure treatment and drainage system according to claim 6 wherein the source of negative pressure is located in a pump unit, and the drainage container and the treatment container are each separately releasably attachable to the pump unit.

8. A combined negative pressure treatment and drainage system according to claim 1, wherein the treatment fluid path comprises a container for collecting liquids from the tissue site, and the drainage fluid path comprises a container for collecting liquids from the drainage site.

9. A combined negative pressure treatment and drainage system according to claim 8, wherein the splitter and negative pressure regulator are positioned in a pump unit.

10. A combined negative pressure treatment and drainage system according to claim 9 wherein the drainage container and the treatment container are each separately releasably attachable to the pump unit.

11. A combined negative pressure treatment and drainage system, comprisinga source of negative pressure;a 3 -port fluid valve, an input of the valve being fluidly coupled to the source of negative pressure, a first outlet of the valve being fluidly coupled to a treatment fluid path for fluidly coupling to a tissue site, and a second outlet of the valve being fluidly coupled to a drainage fluid path for fluidly coupling to a drainage site;a pressure sensor for monitoring the pressure at the input of the 3-port valve; and a controller configured to control the 3-port valve and the source of negative pressure based at least in part on the pressure sensor.

12. A combined negative pressure treatment and drainage system according to claim 11, wherein the controller is configured to control the source of negative pressure and valve to alternately reduce the pressure of the treatment fluid path and the drainage fluid path to different predetermined levels.

13. A combined negative pressure treatment and drainage system according to claim 12, wherein the predetermined level for the drainage fluid path is less than the predetermined level for the treatment fluid path.

14. A combined negative pressure treatment and drainage system according to claim 11, wherein the treatment fluid path comprises a treatment container for collecting liquid from the tissue site, and the drainage fluid path comprises a drainage container for collecting liquid from the drainage site.

15. A combined negative pressure treatment and drainage system according to claim 14 wherein the source of negative pressure, valve, pressure sensor and controller are positioned in a pump unit, and the drainage container and the treatment container are each separately releasably attachable to the pump unit.

16. A method of applying negative pressure to a tissue site for treatment and to a drainage site for drainage, the method comprising the steps ofconfiguring a fluid valve to fluidly couple a source of negative pressure to the tissue site, operating the source of negative pressure to deliver a first predetermined level of negative pressure to the tissue site;configuring the fluid valve to couple the source of negative pressure to the drainage site; andoperating the source of negative pressure to deliver a second predetermined level of negative pressure to the drainage site, wherein the first and second predetermined levels of negative pressure are different.

17. A method according to claim 16, comprising cycling the steps of claim 16 according to a predetermined schedule.

18. A method according to claim 16, comprising cycling the steps of claim 16 according to a schedule based on the speed of reduction of negative pressure at the tissue site and / or the drainage site.

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