Patent Description:
Negative pressure wound therapy (NPWT) is a technique that promotes healing of e.g. surgical, acute and chronic wounds by the application of a negative (that is, sub-atmospheric) pressure to the wound, using a negative pressure pump. The NPWT technique also permits less outside disturbance of the wound as well as provides for transportation of excess fluids away from the wound site. Generally, the NPWT technique has until now mainly been applied to a patient while in a hospital environment. However, recent product development allows the technique to be used by a patient in a home environment.

In order to make it easier and more comfortable for a user to benefit from NPWT, mobile NPWT devices have recently been developed. For such an NPWT device to be truly mobile, it is practically necessary to power the NPWT device with one or several batteries. Naturally, operation of the NPWT device will eventually reduce the amount of energy stored in the battery (or batteries) to such a degree that it becomes necessary to replace the battery with a fully charged battery. Following a battery change, and also at other times, it may be desirable to put the NPWT device through a start-up test sequence to reduce the risk of injury or discomfort for the user.

It is an object of the present invention to provide an improved NPWT device according to claim <NUM> and a computer program stored in a computer readable data carrier according to claim <NUM>. Optional features of the claimed invention are disclosed in dependent claims <NUM>-<NUM> and <NUM>-<NUM>.

Turning now to the drawings and to <FIG> in particular, there is conceptually illustrated a negative pressure wound therapy (NPWT) system <NUM>, comprising a mobile NPWT device <NUM> in accordance with an example embodiment of the present invention. The NPWT system <NUM> further comprises a wound cover <NUM> with a chamber <NUM> arranged at a wound site. The wound cover <NUM>, including the chamber <NUM>, is adapted to create a sealed space <NUM> defined in part by a wound surface <NUM>, such as at the skin of a user, at or around a wound of the user. As is schematically shown in <FIG>, the chamber <NUM> has an inlet <NUM> and an outlet <NUM>. The outlet <NUM> of the chamber <NUM> is flow connected to the mobile NPWT device <NUM> using tubing <NUM>, and the inlet <NUM> of the chamber <NUM> is in flow connection with an ambient (the air around the user) through a filter (not visible in <FIG>) to provide for continuous leakage of air into the chamber <NUM>. The tubing <NUM> may be any suitable flexible tubing fabricated from elastomeric and/or polymeric materials.

As is schematically shown in <FIG>, the NPWT device <NUM> comprises a negative pressure pump <NUM> adapted for establishing a negative pressure when the negative pressure pump <NUM> is controlled to operate. The negative pressure pump <NUM> may be any type of pump that is biocompatible and maintains or draws adequate and therapeutic vacuum levels. Preferably, the negative pressure level to be achieved may be in a range between about -<NUM> mmHg and about -<NUM> mmHg. In a possible embodiment of the present disclosure, a negative pressure range between about -<NUM> mmHg and about -<NUM> mmHg may be used. In a possible embodiment of the present invention, the negative pressure pump <NUM> is a pump of the diaphragmatic or peristaltic type.

The negative pressure pump <NUM> is fluid flow connected to a canister <NUM>, the canister <NUM> also forming part of the NPWT device <NUM>. The canister <NUM> may be formed from e.g. molded plastic or the like, and may possibly be a detachable component of the NPWT device <NUM>. The canister <NUM> may preferably be at least partly transparent/translucent to permit viewing the interior of the canister <NUM> to assist the user in determining the remaining capacity of the canister <NUM>.

An inlet port <NUM> is formed at the canister <NUM>, for allowing connection to the tubing <NUM>. The inlet port <NUM> may also be formed elsewhere at the NPWT device <NUM>, however still fluidly connected to the canister <NUM>. The connection between the inlet port <NUM> and the tubing <NUM> is a sealed connection, thus ensuring that no leakage is formed at the inlet port <NUM> during normal operation of the NPWT device <NUM>. The tubing <NUM> is preferably releasably connected to the inlet port <NUM> through conventional means including a friction fit, bayonet coupling, snap fit, barbed connector, or the like. The inlet port <NUM> may be molded/formed from the same material and/or at the same time as forming the canister <NUM>. A similar sealed connection (e.g. using a flange insulation/ "O-ring") may be formed between the canister <NUM> and the negative pressure pump <NUM>.

The NPWT device <NUM> further comprises a battery <NUM> for powering the NPWT device <NUM>. The battery <NUM> may preferably be of the rechargeable type but may alternatively be disposable. A specifically adapted battery pack may be used in relation to some embodiments of the present disclosure.

The NPWT device <NUM> also comprises a control unit <NUM> for controlling operation of the mobile NPWT device <NUM>, at least one pressure sensor <NUM> arranged to sense a pressure in the canister <NUM>, and a speaker <NUM> for providing user feedback and/or alerts.

The control unit <NUM>, which is powered by the battery <NUM> and coupled to the pump <NUM>, the pressure sensor <NUM>, and the speaker <NUM>, may include a microprocessor, microcontroller, programmable digital signal processor or another programmable device. The control unit <NUM> may also, or instead, include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. Where the control unit <NUM> includes a programmable device such as the microprocessor, microcontroller or programmable digital signal processor mentioned above, the processor may further include computer executable code that controls operation of the programmable device.

During use of the NPWT device <NUM>, the wound cover <NUM> is arranged at a wound site of the user, forming the sealed space <NUM>. The tubing <NUM> is provided to fluidly connect the outlet <NUM> of the chamber <NUM> in the wound cover <NUM> to the inlet port <NUM> of the NPWT device <NUM>. To start the therapy, the mobile NPWT device <NUM> may then be activated, e.g. by the user, by pressing a start/pause button (not shown in <FIG>). In response to this request to start the therapeutic treatment, the control unit <NUM> may control the negative pressure pump <NUM> to operate. When in operation, the negative pressure pump <NUM> will start to evacuate air through the canister <NUM>, the inlet port <NUM>, the tubing <NUM> and the sealed space <NUM> formed by the chamber <NUM> in the wound cover <NUM>. Accordingly, negative pressure will be created within the sealed space <NUM>. In case a liquid has been formed at the wound site, this liquid from the wound site may at least partly be "drawn" from the wound site, through the tubing <NUM>, the inlet port <NUM> and into the canister <NUM> due to the continuous limited leakage provided by the inlet <NUM> of the chamber <NUM>. The amount of liquid (sometimes referred to as exudate) that is drawn from the wound and collected in the canister will depend on the type of wound that is being treated as well as the type of wound dressing used. For example, in case an absorbent dressing is used, the liquid may be absorbed and collected both in the canister and the wound dressing, whereas if a dressing with no or little absorption capacity is used most or all of the liquid from the wound site may be collected in the canister. A suitable filter member (not shown in <FIG>) may be arranged between the canister <NUM> and the negative pressure pump <NUM> to ensure that no liquid is allowed to pass to the negative pressure pump <NUM> from the canister <NUM>.

As was mentioned above, the mobile NPWT device <NUM> requires a charged battery pack <NUM> for operation, and when the battery pack <NUM> is depleted, it needs to be replaced. Following battery replacement, or if the NPWT device <NUM> is replaced by a new one, the NPWT device <NUM> is tested to reduce the risk of malfunction during subsequent therapy.

To that end, the control unit <NUM> in the NPWT device <NUM> according to embodiments of the present invention may be configured to carry out test procedures according to embodiments of the present invention. In particular, processing circuitry comprised in the control unit <NUM> may be programmed to carry out the steps according to various embodiments of the method of the present invention.

In the following, embodiments of the present invention will be described with reference to the flow charts in <FIG>, <FIG>, and <FIG>, in addition to the illustration in <FIG>.

<FIG> is a flow-chart illustrating a first example configuration of the mobile NPWT device according to embodiments of the present invention. Referring to <FIG>, the control unit <NUM> of the NPWT device <NUM> may be configured to receive <NUM> a start-up request, which may for example be provided in the form of pre-defined operation of a button, or a reset switch, or power up following replacement of the battery pack <NUM>.

In response to the request for start-up, the control unit <NUM> is configured to initiate <NUM> a start-up test sequence for the NPWT device <NUM>.

As a part of the start-up test sequence, the control unit <NUM> is configured to acquire <NUM>, from the pressure sensor <NUM> a first signal P<NUM> indicating the pressure in the canister <NUM>.

The control unit <NUM> is configured to evaluate <NUM> the first signal P<NUM> acquired from the pressure sensor <NUM>, and when the first signal P<NUM> indicates a pressure less negative than a predefined threshold pressure Pth, the control unit <NUM> is configured to control <NUM> the pump <NUM> to operate during a predefined time period T, and to acquire <NUM> a second signal P<NUM>, indicating a pressure in the canister <NUM>, after the predefined time period T.

The control unit <NUM> is configured to evaluate <NUM> the second signal P<NUM> acquired from the pressure sensor <NUM> after the predefined time period T, and when the second signal P<NUM> indicates that the pressure has not become more negative, or not sufficiently more negative to provide an indication that the pump <NUM> is operating as desired, the control unit <NUM> may be configured to determine <NUM> that the NPWT device <NUM> has failed the start-up test.

When, on the other hand, the second signal P<NUM> indicates that the pressure in the canister <NUM> has become more negative (or sufficiently more negative) than the pressure indicated by the first signal P<NUM>, the control unit <NUM> is configured to proceed <NUM> with the start-up test sequence, and to determine <NUM> if the NPWT device <NUM> has failed <NUM> the start-up test, or passed the start-up test. If the start-up test is determined by the control unit <NUM> to have been passed by the NPWT device <NUM>, the control unit <NUM> may be configured to allow <NUM> the NPWT device <NUM> to transition to therapy mode.

When the NPWT device <NUM> has been allowed to transition to therapy mode, the control unit <NUM> may be configured to directly transition the NPWT device <NUM> to therapy mode, or to do this in response to a user request, such as a predefined operation of a user interface, such as a button or a touch screen. The predefined time period T may advantageously be at least <NUM> in order to ensure that a reliable indication of whether or not the pump <NUM> and/or pressure sensor <NUM> is/are operational, regardless of the configuration of the NPWT system <NUM>. Even more advantageously, the predefined time period may be at least <NUM>, such as <NUM>.

After the control unit <NUM> has allowed the NPWT device <NUM> to transition to the therapy mode, or as a part of the start-up test sequence, the control unit <NUM> may be configured to take additional steps to test operation of the pump <NUM> and/or the pressure sensor <NUM> of the NPWT device <NUM>. Such a second example configuration of the mobile NPWT device according to embodiments of the present invention is schematically illustrated in <FIG>. Referring to <FIG>, the control unit <NUM> of the NPWT device <NUM> may thus additionally be configured to control <NUM> the pump <NUM> to operate, and to repeatedly acquire <NUM> signals P(t) from the pressure sensor <NUM> while the pump <NUM> is operating.

During or following acquisition of the signals P(t) from the pressure sensor <NUM>, the control unit <NUM> may be configured to evaluate the signals P(t) from the pressure sensor <NUM> to determine if at least one of two failure modes can be identified. When it is determined <NUM> that the signals P(t) acquired from the pressure sensor <NUM> are constantly at a minimum value Pmin that can be acquired from the pressure sensor <NUM>, or the signals P(t) acquired from the pressure sensor <NUM> are constantly at a maximum value Pmax that can be acquired from the pressure sensor <NUM>, or the signals P(t) acquired from the pressure sensor <NUM> alternate between the minimum value Pmin and the maximum value Pmax, the control unit <NUM> may be configured to identify a first failure mode indicating a broken connection between the control unit <NUM> and the pressure sensor <NUM>. When it is determined <NUM> that the signals P(t) acquired from the pressure sensor <NUM> indicate a pressure that increases over time, the control unit <NUM> may be configured to identify a second failure mode indicating malfunctioning amplification circuitry in the pressure sensor <NUM>.

When either of these failure modes is identified by the control unit <NUM>, the control unit is configured to determine <NUM> that signals P(t) from the pressure sensor <NUM> are unreliable, and that the pressure sensor <NUM> should therefore be classified as faulty. In such a case, the control unit <NUM> may be configured to take action by preventing the NPWT <NUM> from entering the therapy mode or interrupting therapy. The control unit <NUM> may also be configured to provide an indication to the user via a user interface.

When none of these failure modes is identified by the control unit <NUM>, the control unit is configured to determine <NUM> that the pressure sensor <NUM> works as intended, and may allow the NPWT <NUM> to enter or continue the therapy mode.

As a part of the start-up test sequence, the control unit <NUM> may be configured to take additional steps to test operation of the NPWT device <NUM>. Such a third example configuration of the mobile NPWT device <NUM> according to embodiments of the present invention is schematically illustrated in <FIG>. Referring to <FIG>, the control unit <NUM> of the NPWT device <NUM> may thus additionally be configured to control <NUM> the speaker <NUM> to emit sound. Since the speaker <NUM> is one of the most power hungry components of the NPWT device <NUM>, this may be an efficient way of evaluating the health of the battery pack <NUM>. According to instructions, a depleted battery pack <NUM> should be replaced by a fully charged or new battery pack <NUM>. If, however, instructions are not followed, a depleted battery pack <NUM> may be replaced by another at least partly depleted battery pack <NUM>.

Accordingly, the control unit <NUM> may be configured to measure <NUM> a battery voltage drop ΔV resulting from the operation of the speaker <NUM>.

The control unit <NUM> may be configured to evaluate <NUM> the measured battery voltage drop ΔV in relation to a predefined threshold voltage drop ΔVth, and to determine <NUM>, when the drop in battery voltage during operation of the speaker is less than the predefined threshold voltage drop ΔVth, that the NPWT device has fulfilled a criterion in the set of predefined criteria, so that the start-up test sequence can proceed.

When the control unit <NUM> instead determines that the measured battery voltage drop ΔV is greater than the predefined threshold voltage drop ΔVth, the control unit <NUM> may be configured to determine <NUM> that the NPWT device <NUM> has failed the start-up test.

Claim 1:
A mobile negative pressure wound therapy (NPWT) device, comprising:
an inlet to be in fluid flow connection with a wound site;
a canister in fluid flow connection with the inlet for collection of liquid from the wound site;
a pump in fluid flow connection with the canister for establishing a negative pressure in the canister;
a pressure sensor arranged to sense a pressure in the canister; and
control circuitry for controlling operation of the NPWT device, the control circuitry being configured to:
receive a request for start-up of the NPWT device;
initiate, in response to the request for start-up, a start-up test sequence for the NPWT device;
acquire, from the pressure sensor, a first signal indicating the pressure in the canister;
evaluate the first signal acquired from the pressure sensor;
when the acquired first signal indicates a pressure less negative than a predefined threshold pressure:
control the pump to operate during a predefined time period;
acquire a second signal from the pressure sensor after the predefined time period;
proceed with the start-up test sequence; and
allow, unless the NPWT device failed at least one test in the start-up test sequence by failing to fulfill at least one criterion in a set of predefined criteria, the NPWT device to transition to therapy mode; and
when the acquired first signal indicates a pressure more negative than the predefined threshold pressure:
proceed with the start-up test sequence without controlling the pump to operate during the predefined time period; and
allow, unless the NPWT device failed at least one test in the start-up test sequence by failing to fulfill at least one criterion in a set of predefined criteria, the NPWT device to transition to therapy mode.