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 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 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 now allows the technique to be used by a patient in a home environment.

When an NPWT device is used in such a home environment, it may be possible that the NPWT device is not operated and monitored by professional users, as compared to when the NPWT device is used in the mentioned hospital environment. Thus, it is desirable to further simplify the operational use of the NPWT device, for minimizing any errors in use and handling.

One example of such an NPWT device is disclosed in <CIT>, where the NPWT device can include one or more controllers responsible for various system functions associated with various levels of responsiveness, such as interfacing with a user (e.g., patient, physician, nurse, etc.), controlling a negative pressure pump, providing network connectivity, and the like. The NPWT device is in <CIT> furthermore configured to determine and monitor flow of fluid in the system, by using one or more pressure transducers or sensors that measure pressure in a fluid flow path and provide feedback to the one of the controllers. The NPWT device is also configured to provide indication, alarms, etc. reflecting operating conditions to a user, including for example visual, audible, tactile, and other types of indicators and/or alarms.

The solution presented in <CIT> generally improves the operation of the NPWT device for an "unskilled home user", by implementing means for ensuring that the NPWT device is easy to operate and effectively indicates to the user if there is a failure with the NPWT device.

Even though the solution <CIT> may reduce operational failure of an NPWT device for use in a home environment, there is always a desire to further improve the safety for the end user, i.e. the patient making use of the NPWT device, with the desire to minimize any risk involved with using an NPWT device.

Document <CIT> discloses a NPWT device in which, similarly to the above document, determination of the presence of blockage in one or more fluid flow paths connecting a negative pressure source to one or more dressings can be performed. In addition, pre-operational ('bootloader'/ startup) testing involves tests and procedures including plausibility of pressure sensor measurements.

In view of above-mentioned and other drawbacks of the prior art, it is an object of the present disclosure to provide improvements in relation to efficient and safe operation of a NPWT device operating to establish a negative pressure within the sealed space formed by a wound cover in relation to a wound site.

According to an aspect of the present disclosure, it is therefore provided a mobile negative pressure wound therapy (NPWT) device according to appended independent claim <NUM>.

The present disclosure is based upon the realization that further measures are needed to ensure that operation of the NPWT device is swiftly terminated in case the NPWT device starts to operate outside of what is a normal behavior, in accordance to the present disclosure defined as a predefined operational range. Enabling such a swift termination of operation of the NPWT device is in accordance to the present disclosure achieved by arranging the NPWT device to further comprise a control circuitry provided externally from the control unit and by providing a connection between the external control circuitry and a pressure sensor providing an indication of the negative pressure formed by the negative pressure pump also connected to the NPWT device's control unit. The external control circuitry is in line with the present disclosure arranged to not be dependent on a correct operation of the control unit (typically comprising some form of programmable circuit), meaning that the external control circuitry (typically comprising at least one logic gate or controllable switch provided with a first input control line for controlling the controllable switch) can terminate the operation of the NPWT device also in cases where e.g. software/firmware running at the control unit fails to operate in a fully normal manner. Accordingly, advantages following the present disclosure may for example include the possibility to provide an extra layer of security to the NPWT device to ensure that the user is not exposed to e.g. an unwanted action of the NPWT device in case of its failure.

Further advantages following the present disclosure includes the possibility to allow the external control circuitry to directly receive an input from e.g. a sensor, and allow the sensor to directly influence if the operation of the NPWT device is to be terminated, without the need to first be processed by the control unit. Accordingly, the setup as defined in accordance to the present disclosure allows for a mixture of advanced processing using the control unit and the extra layer of security achieved by the external control circuitry in case of a failure in the operation of e.g. the control unit.

An example of an undesirable operation NPWT device is in case the negative pressure pump fails to stop once a pressure threshold has been reached. In a typical prior art implementation of an NPWT device, a pressure sensor is connected to the control unit and generating data that is used by the control unit for determining a value for the negative pressure formed by the negative pressure pump. The control unit then uses this pressure value for controlling when and how to activate the negative pressure pump, typically for ensuring that the negative pressure stays within a predefined negative pressure range, where the predefined negative pressure range forms part of the predefined operational range for the NPWT device. One problem with such an implementation is that if the control unit fails in the processing of the data from the pressure sensor, or if the control unit "hangs", then it may be possible that the negative pressure pump stays activated even if the negative pressure goes outside of the predefined negative pressure range. This could potentially inflict pain to the patient, typically at the wound site, since the negative pressure at the wound site in such a situation potentially could be well below what is suitable for the wound.

To counteract such a situation, according to the invention the pressure sensor is also connected to the external control circuitry, and the controllable switch comprised with the external control circuitry is arranged to switch off the power to the negative pressure pump if the operation of the negative pressure pump is to be terminated due to the NPWT device having been determined to operate outside of a predetermined operational range, for instance if the pressure sensor provides an indication that the negative pressure is outside of the predefined negative pressure range.

To handle differences between different batches of pressure sensors it may be advantageous to adapt the pressure sensor and/or the NPWT device to comprise calibration circuitry. By means of such an implementation it could be possible to e.g. allow each individual pressure sensor to be calibrated at a production stage of the NPWT device. In some embodiments the pressure sensor is a differential pressure sensor, allowing for further reliability as to the measurement data provided by the pressure sensor.

In some embodiment of the present disclosure it may be advantageous to further equip the NPWT device with a watchdog circuitry, connected to and arranged as an external component in relation to the control unit. The watchdog circuitry is typically provided for allowing a path of recovery of the control unit in case of a malfunction of the control unit. The watchdog circuitry generally comprises a timer that is arranged to reset the control unit once the timer has counted down to zero (from a present value defining a preset time). However, as long as the control unit is functioning in a normal manner, the control unit will continuously (before the present time has passed) reset the timer of the watchdog circuitry, whereby the watchdog circuitry will not reset the control unit.

However, in accordance to the present disclosure the watchdog circuitry is not only arranged in connection with the control unit and provided for "resetting" the control unit. Rather, in accordance to the present disclosure the watchdog circuitry is also connected to the first controllable switch, whereby a "timeout" of the timer comprised with the watchdog circuitry will also switch the first controllable switch. Such an implementation will in an advantageous manner further enhance the security of the NPWT device, since the preset time of the watchdog circuitry may be set short enough (e.g. possibly between <NUM> second to <NUM> seconds) to ensure that the operation of the negative pressure pump is terminated in a direction connection with a possible malfunction of the control unit.

Accordingly, in addition to waiting for the negative pressure to go outside of the predefined negative pressure range, the switching of the first controllable switch achieved by the watchdog circuitry in conjunction with the first controllable switch of the external control circuitry will add a further limitation to an unwanted operation of the negative pressure pump in case of failure of the NPWT device, thus further reducing the risks involved with using the NPWT device in accordance to the present disclosure.

In one embodiment of the present disclosure the control circuitry further comprises a second controllable switch connected to the control unit and adapted to switch on the power to the negative pressure pump if the negative pressure pump is to be operated. The control unit may thus effectively control when to operate the negative pressure pump, where the second controllable switch of the external control circuitry will function as a "buffer" between the control unit and the negative pressure pump, reducing the risk e.g. any disturbances generated by the negative pressure pump to affect the operation of the control unit.

Advantageously, the control unit is further adapted to control the second controllable switch using pulse width modulation (PWM), whereby a speed of the negative pressure pump may be seamlessly controlled according in accordance to a desired behavior/scheme.

In some embodiments of the present disclosure the control unit is adapted to continuously measure an intermediate voltage level of the battery, and to select the PWM scheme based on recently measured voltage level of the battery. Generally, the voltage level of the battery will gradually drop during operation of the NPWT device, and simply switching on/off the second controllable switch using a constant PWM switching scheme will result in a reduction of the speed of the negative pressure pump as the voltage level drops. Accordingly, to maintain an operational speed of the negative pressure pump within a predetermined speed range (e.g. +/- <NUM>% of a speed value), it is desirable to select the PWM scheme based on a recently measured voltage level of the battery. By such a measure it is possible to keep the speed of the negative pressure pump essentially constant (such as within the mentioned exemplary +/- <NUM>%). Keeping the speed of the negative pressure pump essentially constant will also result in a sound level of the negative pressure pump at an essentially constant level, reducing a disturbance of the patient using the NPWT device. In some embodiments a "base speed" of the negative pressure pump is selected during manufacturing or by the patient, where the base speed is set to a level where the patient experiencing (or is expected to experience) the least amount of disturbance. The selection of the base speed may in some embodiments be achieved by providing input from the patient using a user interface comprised with the NPWT device.

Furthermore, it may generally be preferred that the canister is detachably connected to a housing comprising the negative pressure pump, whereby e.g. a full canister may be removed and replaced with an empty (new) canister. In such an embodiment it may be desirable to provide e.g. the canister and the housing with some form of engagement means for securing the canister to the housing such that the canister is not unintentionally removed from the housing. The engagement means may in one embodiment comprise a pair of flexible protrusions extending from the canister and adapted to engage with e.g. corresponding locking grooves provided at the housing.

In an embodiment of the present disclosure, the NPWT device is adapted for home care. Accordingly, in combination with the NPWT device being mobile, the NPWT device may be adapted to be carried by the user, e.g. in a pocket, belt, strap or similar. In addition, for simplifying the (end) user operation of the NPWT device, the NPWT device may additionally be provided with indication means for displaying a symbol providing an indication of an operational status for the NPWT device. In one embodiment the NPWT device may instead of display element be provided with dedicated light sources arranged at an operational front surface of NPWT device for providing the user with the mentioned operational status information.

Advantageously, the NPWT device is provided as a component of a wound treatment system, further comprising the wound cover. This will be further elaborated below in the detailed description of the present disclosure.

The skilled addressee realizes that different features of the present disclosure may be combined to create embodiments other than those described in the following, without departing from the scope of the invention as defined in the appended claims.

Turning now to the drawings and to <FIG> in particular, there is conceptually illustrated a wound treatment system <NUM>, comprising a NPWT device <NUM> in accordance with the present disclosure. The wound treatment system <NUM> further comprises a wound cover <NUM>, the wound cover <NUM> being adapted to create a sealed space <NUM> defined in part by a wound surface <NUM>, such as at the skin of a user/person, at or around a wound of the user/person. Additionally, the NPWT device <NUM> is fluidly connected to the wound cover <NUM> using e.g. a tubing <NUM>. The tubing <NUM> may be of any suitable flexible tubing fabricated from elastomeric and/or polymeric materials.

The NPWT device <NUM> in turn comprises a negative pressure pump <NUM> adapted for establishing a negative pressure when the negative pressure pump <NUM> is operable, i.e. in an active state. 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 is 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 is used. In a possible embodiment of the present disclosure, the negative pressure pump <NUM> is either a diaphragm pump or a peristaltic pump, or the like, in which the moving parts draw the mentioned fluid from the wound cover <NUM>.

The negative pressure pump <NUM> is fluidly 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 possibly being a detachable component of the NPWT device <NUM>. As mentioned above, the canister <NUM> is preferably at least partly transparent/translucent to permit viewing into the interior of the canister <NUM> to assist the user in determining the remaining capacity of the canister <NUM>.

For ease of understanding of the following discussion of the present disclosure, it should be understood that the expressions "negative pressure", "sub-atmospheric pressure", "reduced pressure", as used interchangeably herein, generally refer to a pressure less than a local ambient pressure, such as the ambient pressure in a local environment external to a sealed therapeutic environment provided by a wound cover or dressing. In many cases, the local ambient pressure may also be the atmospheric pressure at which a patient is located. Unless otherwise indicated, values of pressure stated herein are gauge pressures. Similarly, references to increases in negative pressure typically refer to a decrease in absolute pressure, while decreases in negative pressure typically refer to an increase in absolute pressure.

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>.

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 arranged to be disposable and thus to be changed once discharged. A specifically adapted battery pack may be used in relation to some embodiment of the present disclosure.

The NPWT device <NUM> also comprises a control unit <NUM>, electrically connected to the battery <NUM> and adapted to control an operation of the negative pressure pump <NUM>. The control unit <NUM> may include a microprocessor, microcontroller, programmable digital signal processor or another programmable device. The control unit <NUM> may also, or instead, each 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.

In line with the present disclosure, the NPWT device <NUM> further comprises a control circuitry <NUM> provided externally from the control unit <NUM> and arranged to generally control the operation of the negative pressure pump <NUM>, specifically for ensuring that the operation of the negative pressure pump <NUM> may be swiftly terminated in case the NPWT device <NUM> starts to operate outside of what is considered to be a normal behavior, as has been discussed above. The operation of the control circuitry <NUM> is further elaborated below in relation to <FIG>.

In addition, the NPWT device <NUM> comprises at least one pressure sensor <NUM> arranged in fluid connection with the negative pressure pump <NUM>.

During use of the NPWT device <NUM>, the wound cover <NUM> is arranged at a wound site of the user/patient, forming the sealed space <NUM>. The tubing <NUM> is provided to fluidly connect the wound cover <NUM> to the inlet port <NUM> of the NPWT device <NUM>. The NPWT device <NUM> is then activated, e.g. by the user/patient, by pressing the start/pause button <NUM> (see <FIG>). The negative pressure pump <NUM> is thereby activated. When activated, 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 wound cover <NUM>. Accordingly, the 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>. The amount of liquid (possibly defined 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>) is arranged between the canister <NUM> and the negative pressure pump <NUM> to ensure that no fluid is allowed to pass to the negative pressure pump <NUM> from the canister <NUM>.

Turning now to <FIG> illustrating different views of a possible implementation of the NPWT device according to the present disclosure, as shown in <FIG>. As presented, a majority of the components comprised with the NPWT device <NUM> are arranged within a housing <NUM>, where the housing <NUM> may be formed at least partly from plastic.

As presented above, the canister <NUM> is preferably allowed to be detachably connected to the housing <NUM>. By means of such an implementation it may be possible for the user operating the NPWT device <NUM> to remove and e.g. discard the canister <NUM> in case the canister <NUM> is full or otherwise need to be exchanged (e.g. due to a problem with the canister <NUM> or the inlet port <NUM>, etc.).

As shown in <FIG>, the housing <NUM> is provided with a start/pause button <NUM> for initiating/pausing operation of the NPWT device <NUM>. The start/pause button <NUM> is electrically connected to the control unit <NUM>. In addition, the housing <NUM> may optionally be provided with one or a plurality of display symbols <NUM>, <NUM>, <NUM> for providing feedback to the user of the NPWT device <NUM>. For example, the display symbols <NUM>, <NUM>, <NUM> may provide an indication to the user that there is a possible leakage at e.g. the wound cover <NUM>, that there is a need to charge/change the battery <NUM>, or that there is a blockage in the tubing <NUM>. The display symbols <NUM>, <NUM>, <NUM> may possible be formed by providing e.g. LEDs below an inner surface of the housing <NUM>, where suitable symbols may be formed, e.g. printed, at an outer surface of the housing <NUM> at suitable corresponding positions. It should be understood that the display symbols <NUM>, <NUM>, <NUM> alternatively may be shown on a display screen integrated with the housing <NUM>.

Turning now to <FIG>, presenting an exemplary detailed schematic of the control circuitry <NUM> comprised with the NPWT device <NUM>. As discussed above, the control circuitry <NUM> is provided externally and separately from the control unit <NUM>, however arranged in communication with the control unit <NUM>. The control circuitry <NUM> is further arranged in communication with the pressure sensor <NUM> and the negative pressure pump <NUM>
The control circuitry <NUM> comprises components allowing the operation of the negative pressure pump <NUM> to be terminated without any involvement of the control unit <NUM>. Thus, even in a situation where the control unit <NUM> fails to correctly identify e.g. a problem with sensor values received (such as a "too low" negative pressure), the control circuitry <NUM> can act independently of the control unit <NUM> and turn off the negative pressure pump <NUM>.

In the non-limiting and exemplary illustration as shown in <FIG>, the control circuitry <NUM> is shown to comprise a first controllable switch SW<NUM>. When the first controllable switch SW<NUM> is deactivated the negative pressure pump <NUM> will be turned off. The first controllable switch SW<NUM> is in turn controlled by each one of a pressure comparator <NUM> and a watchdog circuitry <NUM>, both comprised with the control circuitry <NUM>. Accordingly, the negative pressure pump <NUM> will be turned off by means of the first controllable switch SW<NUM> if either of the pressure comparator <NUM> or the watchdog <NUM> provides a control signal indicating that the operation of the negative pressure pump <NUM> is to be terminated. In <FIG> the "either functionality" is functionally illustrated by a logic OR circuitry <NUM>.

The pressure comparator <NUM> is in turn connected to the pressure sensor <NUM>, where data from the pressure sensor is compared to a predetermined negative pressure range. The predetermined negative pressure range may in turn be set e.g. a time of manufacturing, allowing the pressure sensor <NUM> to be correctly and possibly individually calibrated in a calibration process. It may in some embodiments be suitable to allow the pressure sensor <NUM> to be implemented as a differential pressure sensor, in some embodiments allowing for an in comparison higher reliability as compared to non-differential pressure sensor. As is shown in <FIG>, the pressure comparator <NUM> is provided with an interface for receiving the predetermined negative pressure range. Such an interface may for example be configured in line with suitable communication protocols, where the so called I2C protocol may be useful.

Accordingly, in case the pressure value as determined by the pressure sensor <NUM> fall outside of the predetermined negative pressure range, the pressure comparator <NUM> generates a control signal for controlling the first controllable switch SW<NUM>, whereby the first controllable switch SW<NUM> is turned off and the operation of the negative pressure pump <NUM> is terminated. It should be understood that the pressure value as determined by the pressure sensor <NUM> is also provided to the control unit <NUM>, for use in the general operation of the NPWT device <NUM>.

The watchdog circuitry <NUM> is arranged in communication with the control unit <NUM> and is generally comprised with the NPWT device <NUM> for allowing path of recovery of the control unit <NUM> in case of a malfunction of the control unit <NUM>. However, in line with the present disclosure the watchdog circuitry <NUM> will also function as a means for direct terminating the operation of the negative pressure pump <NUM>. This is achieved by allowing a "reset signal" (in case of a non-responsive control unit <NUM>) to be siphoned off and provided to the first controllable switch SW<NUM>, i.e. not just for provided to the control unit <NUM> for resetting the control unit <NUM>. Accordingly, if the watchdog circuitry <NUM> enters into a reset state, the reset signal will reset the control unit <NUM> and at the same time provide a control signal for operating the first controllable switch SW<NUM>.

The implementation of the watchdog circuitry <NUM> in relation to the first controllable switch SW<NUM> allows for a greatly reduced reaction time as compared to a situation where the termination of the negative pressure pump <NUM> is only dependent on the operation of the control unit <NUM>. That is, rather than having to wait for the control unit <NUM> to "reboot", the watchdog circuitry <NUM> will directly provide its control signal to the first controllable switch SW<NUM> to terminate the operation of the negative pressure pump <NUM>.

In addition to the above, the control circuitry <NUM> further comprises a second controllable switch SW<NUM>. The second controllable switch SW<NUM> is arranged in communication with the control unit <NUM> and may in some embodiments be seen as functioning as driver for the negative pressure pump <NUM>. In some implementations of the present disclosure, the control unit operates the negative pressure pump <NUM> based on pulse width modulation (PWM), meaning that the control unit <NUM> switches the negative pressure pump <NUM> on and off, using the second controllable switch SW<NUM>. The frequency of the switching is selected to be high enough to ensure that the moment of inertia of an electrical motor (not shown) comprised with the negative pressure pump <NUM> continues to operate the negative pressure pump <NUM>. However, by controlling the ratio between the time the second controllable switch SW<NUM> on and off, the overall suction provided by means of the negative pressure pump <NUM> may be controlled.

In some embodiments it may be desirable to select a PWM switching scheme that keeps the frequency fairly constant over time. In such an embodiment it is thus desirable to keep the frequency fairly constant while at the same time adjusting the on/off ratio (as compared to adjust both of the switching frequency and the on/off ratio). Such an implementation has shown desirable for the end user, since this keeps any sound stemming from the operation of the negative pressure pump <NUM>.

To achieve such a functionality, it may in some embodiments be desirable to monitor a voltage level of the battery <NUM> and select the PWM switching scheme according to a recently measured voltage level. By means of such an implementation, it may be possible to keep the speed of the negative pressure pump <NUM> even though the voltage level of the battery <NUM> will gradually decline over time.

During operation of the NPWT device <NUM>, with further reference to <FIG>, the control unit will select a suitable PWM scheme, for example based on recently measured voltage level of the battery <NUM>, and subsequently generate a control signal that in turn controls the second controllable switch SW<NUM>, thereby operating, S1, the negative pressure pump <NUM>.

The control unit <NUM> will continuously receive an indication from the pressure sensor <NUM> relating to the negative pressure formed by the negative pressure pump <NUM>, and control when and for how long time the negative pressure pump <NUM> is to operate. However, in line with the present disclosure it is desirable to ensure that the operation of the negative pressure pump <NUM> in case of any possible problem with the NPWT device <NUM>.

Accordingly, in line with the present disclosure a control signal is formed, S2, if the NPWT device <NUM> is determined to operate outside a first predefined operational range. Operation outside of first predefined operational range for example includes a situation where the negative pressure formed by the negative pressure pump <NUM> comes outside a predetermined negative pressure range. However, other situations include for example where the control unit <NUM> of the NPWT device <NUM> is determined to fail, such as by a reset signal generated by the watchdog circuitry <NUM> comprised with the control circuitry <NUM>. Also in this situation such a control signal is formed.

The control signal is in turned used for terminating, S3, the operation of the negative pressure pump <NUM> using the control circuitry <NUM>, where the control circuitry <NUM> is provided externally from the control unit <NUM>.

The control functionality of the present disclosure may be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwire system.

Claim 1:
A mobile negative pressure wound therapy (NPWT) device (<NUM>), comprising:
- a housing (<NUM>),
- a negative pressure pump (<NUM>) arranged within the housing (<NUM>),
- a canister (<NUM>) fluidly coupled to the negative pressure pump (<NUM>) and to a wound cover (<NUM>), the wound cover (<NUM>) provided for creating a sealed space (<NUM>) defined in part by a wound site,
- a battery (<NUM>) arranged within the housing (<NUM>),
- a control unit (<NUM>) arranged within the housing (<NUM>), the control unit (<NUM>) being electrically connected to the battery (<NUM>) and adapted to provide power to the negative pressure pump (<NUM>) for operating the negative pressure pump (<NUM>) to establish a negative pressure within the sealed space (<NUM>),
- a pressure sensor (<NUM>) adapted to provide an indication of a negative pressure formed by the negative pressure pump (<NUM>),
wherein:
- the NPWT device (<NUM>) further comprises a control circuitry (<NUM>) provided externally from the control unit (<NUM>),
- the pressure sensor (<NUM>) is connected to the control unit (<NUM>) and to the control circuitry (<NUM>), and
- the control circuitry (<NUM>) comprising a first controllable switch (SW<NUM>) arranged to switch off the power to the negative pressure pump (<NUM>) if the operation of the negative pressure pump (<NUM>) is to be terminated due to the NPWT device (<NUM>) having been determined to operate outside of a predefined operational range.