Pressure sensing for negative pressure treatment systems

Abstract

Negative pressure treatment devices for delivering negative pressure to a tissue site and including a single pressure sensor which can monitor the pressure at one or more locations within the treatment system. Certain examples include valves to connect the pressure sensor to different locations in the system such that pressure can be monitored at more than one location.

Description

PA200044W002PRESSURE SENSING FOR NEGATIVE PRESSURE TREATMENT SYSTEMSCROSS-REFERENCE TO REEATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 777,258, 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 pressure sensing, and particularly such systems with a single pressure sensor.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] In order to control the negative pressure source, pressure sensors are commonly provided to monitor the pressure in one or more parts of the system. The pressure at the tissue site may be monitored and also at the negative pressure source. Monitoring in each of these locations enables control of the negative pressure source to deliver the intended pressure at the tissue site being treated, and also the detection of blockages in the system. However, the use of two pressure sensors increases the cost of the system.

[0005] There is therefore a need for a negative pressure treatment system which enables appropriate pressure monitoring, but which has reduced cost.BRIEF SUMMARY

[0006] The invention is defined by the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 shows a schematic diagram of a negative pressure treatment system;

[0008] Figure 2 shows an example negative pressure treatment system having only a single pressure sensor and a switchable valve;

[0009] Figure 3 shows an example negative pressure treatment system having only a single pressure sensor and a pressure relief valve;

[0010] Figure 4 shows an example negative pressure treatment system having only a single pressure sensor and a switchable valve;

[0011] Figure 5 shows an example negative pressure treatment system and a differential pressure switch;

[0012] Figure 6 shows a flowchart of a method of operating negative pressure treatment systems with a single pressure sensor; and

[0013] Figure 7 is a block diagram of components of a pump unit and a pressure sensor device.DESCRIPTION OF EXAMPLE EMBODIMENTS

[0014] 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.

[0015] 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.

[0016] 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. 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 tissue site may also be areas of a patient without a wound where it is desired to apply negative pressure to treat internal damage. The surface of the patient within the tissue site being treated will be referred to as the tissue site bed.

[0017] The therapy system 100 includes a negative-pressure source 102, a dressing 104, and a canister 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.

[0018] In alternative examples the canister 106 may be omitted and liquids may be collected at the tissue site using an absorbent dressing.

[0019] 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 canister 106, and a second pressure sensor 116 may be included to detect the pressure at the tissue site 108. The second pressure sensor 116 is fluidly coupled to the tissue site by a separate lumen to the lumen which delivers negative pressure to the tissue site. This prevents the pressure reading being affect by liquids or blockages in the lumen. These pressure sensors 114, 116 may beutilised by the controller 112 to control the negative pressure source 102. Other sensors may also be provided to monitor operating parameters of the system.

[0020] A purge valve 124 is provided which selectively connects the sensing lumen to atmosphere. By opening the purge valve 124 air can enter the system leading to significant fluid flow through the lumens helping clear liquids and blockages.

[0021] 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. The instillation elements of the system may be omitted for a system which only provides treatment by delivery of negative pressure.

[0022] The components of therapy system 100 may be combined into integrated elements and may be co-packaged or provided separately.

[0023] 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.

[0024] 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.

[0025] Pressure sensor 114 measures the pressure in the canister 106 (or at the outlet of the negative pressure source) and pressure sensor 116 measures the pressure at the tissue site. Measuring both of these pressures enables the pressure at the tissue to be controlled for the desired treatment regime and also allows detection of blockages by monitoring for differences in the two measurements. The detection of blockages is useful to ensure correct operation of the system, but the provision of two pressure sensors adds cost to the system.

[0026] Figure 2 shows a schematic diagram of a negative pressure treatment system which enables measurement of pressure at the same locations as the sensors of Figure 1 but has only a single pressure sensor. All disclosure in relation to Figure 1 applies equally to the example of Figure 2, except where that disclosure is not applicable due to the differences between the examples.

[0027] Pump unit 200 comprises a pump 202 for delivering negative pressure to the tissue site via canister 204 and negative pressure lumen 206. Sensing lumen 208 is a separate fluid pathway from the tissue site to the pump unit 200 and is fluidly connected to purge valve 210. Purge valve 210 can selectively couple the sensing lumen 208 to atmosphere. When the system is at a negative pressure and the purge valve 210 is opened air is drawn into the system and assists with the clearage of blockages and movement of liquid through the lumens. Pressure sensor 212 is fluidly connected to the common port of a switchable valve 214 such that it can be fluidly connected to either the sensing lumen 208 or the outlet of the pump 202. As described in relation to Figure 1 the various components of Figure 2 are controlled by a controller, which is not shown for clarity.

[0028] When the pressure sensor 212 is connected to sensing lumen 208 by the valve 214 the pressure at the tissue site can be measured, and when the pressure sensor 212 is connected to negative pressure lumen 206 the pressure at the outlet of the pump 202 can be measured. The controller of the pump unit 200 switches the valve 214 between connections in a suitable manner to monitor the pressure at the two locations as required for control of the pump 202. In an example, the controller may be configured to alternate between the two locations regularly with each location being monitored for the same amount of time. Alternatively, the controller may be configured to monitor each location for a different period of time. Monitoring the pressure at the tissue site may be considered more important and accordingly that location may be monitored for longer periods of time than the pump outlet. Measurements of the tissue site pressure are used by the controller to control the pump to deliver the required pressure at the tissue site. If a comparison of the pressure at the tissue site and at the pump outlet shows a difference it may be determined that there is a blockage in one of the lumens. A predetermined threshold may be defined such that a blockage is only determined if the pressure difference is above that threshold. Similarly, a blockage may only be indicated if the difference is detected for more than a predetermined amount of time.

[0029] When a blockage is indicated the controller may open the purge valve 210 to allow air to enter the system from atmosphere to attempt to clear the blockage.

[0030] The combination of the single pressure sensor and switchable valve therefore provides comparable pressure monitoring to prior systems with two pressure sensors, but while only requiring one sensor and, hence, reducing cost.

[0031] Figure 3 shows a schematic diagram of a negative pressure treatment system which utilises only a single pressure sensor. All disclosure in relation to Figure 1 applies equally to the example of Figure 3, except where that disclosure is not applicable due to the differences between the examples.

[0032] Pump unit 300 comprises a pump 302 for delivering negative pressure to the tissue site via canister 304 and negative pressure lumen 306. Sensing lumen 308 is a separate fluid pathway from the tissue site to the pump unit 300 and is fluidly connected to purge valve 308. Purge valve 310 can selectively couple the sensing lumen 308 to atmosphere. When the system is at a negative pressure and the purge valve 310 is opened air is drawn into the system and assists with the clearage ofblockages and movement of liquid through the lumens. Pressure sensor 312 is fluidly connected to the sensing lumen 308 to sense the pressure at the tissue site. As described previously the various components of Figure 2 are controlled by a controller, which is not shown for clarity. The pressure sensed at the tissue site by pressure sensor 312 is used by the controller to control the pump 302 to deliver the required pressure at the tissue site.

[0033] Pressure relief valve 314 is fluidly connected between the pump outlet and atmosphere. The pressure relief valve 314 is configured to open when the negative pressure at the pump outlet exceeds a predetermined value (i.e. the absolute pressure at the pump outlet is more negative than a predetermined threshold). In an example that predetermined pressure may be -150mmHg (relative to the atmospheric pressure at the location of the pump unit).

[0034] The pump unit of Figure 3 can only monitor the pressure at the tissue site. If the negative pressure lumen 306 becomes blocked negative pressure generated by the pump 302 cannot reach the tissue site. However, because the pressure at the pump outlet is not monitored the system cannot determine there is a blockage and may continue to run the pump 302 in an effort to deliver the desired negative pressure at the tissue site. This can lead to the negative pressure at the pump outlet reaching a dangerous level which could harm the tissue site if the blockage suddenly clears and the pressure reaches the tissue site. The pressure relief valve 314 avoids this risk by admitting atmospheric air into the system if the negative pressure at the pump outlet reaches the predetermined threshold.

[0035] The system of Figure 3 may be configured to open the purge valve intermittently to clear any potential blockages. The purge valve 310 may be opened when it is detected that the pump 302 has been running for a long period of time as that may indicate the generated negative pressure is not reaching the tissue site due to a blockage.

[0036] The pressure relief valve 314 could be provided with a sensor to indicate when the pressure relief valve 314 opens. The controller may detect that indication and open the purge valve in response as the pressure relief valve 314 opening is an indication of a blockage.

[0037] Figure 4 shows a schematic diagram of a further negative pressure treatment system using only a single pressure sensor. All disclosure in relation to Figure 1 applies equally to the example of Figure 4, except where that disclosure is not applicable due to the differences between the examples.

[0038] Pump unit 400 comprises a pump 402 for delivering negative pressure to the tissue site via canister 404 and negative pressure lumen 406. Sensing lumen 408 is a separate fluid pathway from the tissue site to the pump unit 400.

[0039] A 4-port valve 410 is provided which switchable interconnects sensing lumen 408, negative pressure lumen 406, pressure sensor 412, and a purge lumen 414. Specifically, the valve 410 can fluidly connect the pressure sensor 412 to either the sensing lumen 408 or the negative pressure lumen 406 and can connect or disconnect the sensing lumen 408 to the purge lumen 414.

[0040] The valve 410 is controlled by a controller (not shown) of the pump unit 400 to configured fluidic connections to sense the pressure at the tissue site or pump outlet, and to purge the system.

[0041] The same principles described for control of the valve 210 in relation to Figure 2 apply equally to the system of Figure 4 and hence will not be repeated.

[0042] Figure 5 shows a schematic diagram of a further negative pressure treatment system using only a single pressure sensor.

[0043] Pump unit 500 comprises a pump 502 for delivering negative pressure to the tissue site via canister 504 and negative pressure lumen 506. Sensing lumen 508 is a separate fluid pathway from the tissue site to the pump unit 500. As with earlier examples a purge valve 510 selectively connects the sensing lumen 508 to atmosphere. Pressure sensor 512 senses the pressure in the sensing lumen 508 and hence at the tissue site. A differential pressure switch 514 is fluidly connected between the sensing lumen 508 and the negative pressure lumen 506. The switch 514 is configured to provide an indication to the controller when the pressure difference between the sensing lumen 508 and negative pressure lumen 506 exceeds a predetermined value.

[0044] As explained previously, a difference between the pressure at those two locations may indicate a blockage in one of the lumens. When switch 514 indicates such a difference the controller may open the purge valve 510 to attempt to clear the blockage.

[0045] After the purging process is executed if the blockage has been cleared the two pressures will be approximately equal (i.e. below the predetermined threshold) and the normal operation can continue. However, if the switch 514 indicates the pressures differ by more than the predetermined amount a blockage is determined to still be present. A further purge process may be executed, or an alert may be output to the user to attend to the blockage.

[0046] Figure 6 shows a flowchart of a method for operating the systems of Figures 2 or 4.

[0047] At step 600 the controller sets the valve 214, 410 such that the sensor 212, 412 senses the pressure at the tissue site. At step 602 the controller utilises the pressure values from the sensor 212, 412 to control the pump 202, 402 to deliver the desired pressure at the tissue site.

[0048] At step 604 the controller stores the pressure at the tissue site and controls the valve 214, 410 to connect the pressure sensor 212, 412 to sense the pressure at the pump outlet in the negative pressure lumen. The controller compares the pressure at the pump outlet to the stored tissue pressure at step 606 and at step 608 determines if the pressures differ by more than a predetermined amount. If the pressures do differ by more than the predetermined amount a purge process is executed at step 610.

[0049] The method then returns to step 600 to continuously execute the method of Figure 6 which allows the pressure at the tissue site to be monitored, while also monitoring for blocked lumens, using only a single pressure sensor.

[0050] 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 supplyingnegative 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, and sensors 912. Communications interface 914 is a wireless communication interface capable of establishing a wireless connection to a remote device for the exchange of data.

[0051] 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. For example, in some configurations the dressing 104, the canister 106, or both may be eliminated or separated from other components for manufacture or sale. In other example configurations, the controller 112 may also be manufactured, configured, assembled, or sold independently of other components.

[0052] 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 pump unit for a negative pressure treatment system, the pump unit comprising:a pump for generating negative pressure at an outlet lumen for fluidly coupling to a tissue site; a sensing lumen for fluidly coupling to the tissue site;only one pressure sensor;a switchable valve fluidly coupled to the outlet lumen, the only pressure sensor, and the sensing lumen, and configured to fluidly couple the only pressure sensor to the sensing lumen to sense the pressure in the sensing lumen or to the outlet lumen to sense the pressure in the outlet lumen; and a controller electrically connected to the pump, the only pressure sensor, and the switchable valve.

2. A pump unit according to claim 1, further comprising a purge valve for selectively fluidly coupling the sensing lumen to atmosphere and being electrically connected to the controller.

3. A pump unit according to claim 1, wherein the switchable valve is also fluidly connected to a purge lumen fluidly connected to atmosphere, wherein the switchable valve is configured to connect or disconnect the sensing lumen to and from the purge lumen.

4. A pump unit for a negative pressure treatment system, the pump unit comprising:a pump for generating negative pressure at an outlet lumen for fluidly coupling to a tissue site; a sensing lumen for fluidly coupling to the tissue site;only one pressure sensor, the only pressure sensor being fluidly connected to the sensing lumen to sense the pressure in the sensing lumen;a pressure relief valve fluidly connected to the outlet lumen and configured to connect the outlet lumen to atmosphere if the pressure in the outlet lumen becomes more negative than a predetermined threshold; anda controller electrically connected to the pump and only pressure sensor.

5. A pump unit according to claim 4, further comprising a purge valve for selectively fluidly coupling the sensing lumen to atmosphere and being electrically connected to the controller.

6. A pump unit for a negative pressure treatment system, the pump unit comprising:a pump for generating negative pressure at an outlet lumen for fluidly coupling to a tissue site; a sensing lumen for fluidly coupling to the tissue site;only one pressure sensor, the only pressure sensor being fluidly connected to the sensing lumen to sense the pressure in the sensing lumen;a pressure differential sensor fluidly coupled to the sensing lumen and the outlet lumen and configured to output an indication if the pressure difference between the sensing lumen and the outlet lumen exceeds a predetermined value; anda controller electrically connected to the pump, the only pressure sensor, and the pressure differential sensor.

7. A pump unit according to claim 6. further comprising a purge valve for selectively fluidly coupling the sensing lumen to atmosphere and being electrically connected to the controller.

8. A method of operating a pump unit for delivering negative pressure to a tissue site, the method comprising the steps of:controlling a switchable valve to fluidly connect a pressure sensor to a sensing lumen to sense the pressure at the tissue site;controlling a pump based on the sensed pressure at the tissue site to deliver a predetermined negative pressure at the tissue site;controlling the switchable valve to fluidly connect the pressure sensor to the outlet of the pump to measure the pressure at the outlet;comparing the pressure sensed at the tissue site to the pressure sensed at the pump outlet; and if the difference is greater than a predetermined threshold determining that at least one lumen is blocked.

9. A method according to claim 8, further comprising the step of executing a purge process if it is determined that at least one lumen is blocked.

10. A method according to claim 8 or claim 9, further comprising alternating between sensing the pressure at the tissue site and at the outlet of the pump.

11. A method of operating a pump unit for delivering negative pressure to a tissue site, the method comprising the steps ofsensing the pressure at the tissue site using a single pressure sensor of the pump unit via a sensing lumen;controlling a pump based on a pressure sensed at the tissue site to deliver a predetermined negative pressure at the tissue site; andif a pressure difference between the sensing lumen and the outlet of the pump exceeds a predetermined threshold determining that at least one lumen is blocked.

12. A method according to claim 11, further comprising the step of executing a purge process if it is determined that at least one lumen is blocked.

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