WO2025076590A1

WO2025076590A1 - Wound drainage pressure maintenance

Info

Publication number: WO2025076590A1
Application number: PCT/AU2024/051069
Authority: WO
Inventors: Raymond STUBBER; Scott Foster; Brody PAYNE
Original assignee: International Medical Research Pty Ltd
Current assignee: International Medical Research Pty Ltd
Priority date: 2023-10-10
Filing date: 2024-10-10
Publication date: 2025-04-17
Anticipated expiration: 2026-04-10

Abstract

Method and apparatus for creating negative pressure to remove wound fluid from a wound has a source of negative pressure, a pressure sensor to measure pressure in a fluid flow path fluidically connecting the wound and the source of negative pressure; a controller to control activation and deactivation of the source of negative pressure and to determine a pressure measurement based on the pressure measured by the pressure sensor. The pressure sensor periodically measures an instantaneous pressure. When the instantaneous pressure is equal to the preset negative pressure of a tolerance range, the source of negative pressure is switched off and the controller puts the apparatus into a sleep mode, the controller activates periodically from sleep mode to check the instantaneous pressure.

Description

WOUND DRAINAGE PRESSURE MAINTENANCE

TECHNICAL FIELD

[0001 ] Embodiments of the present invention relate to wound drainage apparatus and method of control thereof where reduced pressure (partial vacuum) is employed to assist wound drainage. The function of wound drainage is to promote rapid and efficient healing, such as for postoperative wounds.

BACKGROUND

[0002] Negative pressure wound therapy (NWPT), sometimes called reduced pressure wound therapy, utilises a source of negative pressure connected to a tube inserted into the wound to reduce the pressure within the wound and allow atmospheric pressure to force wound fluid along the tube to a container.

[0003] Such wound therapy is widely appreciated for the ability to promote the healing rate of a wound, such as wounds from surgery e.g. incision wounds, open wounds, thorax (chest) or abdomen wounds, by removing exudates to reduce risk of infection, promoting tissue granulation at the wound site, and encouraging blood flow.

[0004] A wide range of equipment has been proposed to assist in the draining of fluid from wounds, particularly wounds resulting from surgery or accidents, to help promote healing of the wound.

[0005] One type of known construction employs a bellows type container that can be reduced in volume against the pressure of an internal mechanical spring or by the force of deformation of the container material to provide a vacuum source. This is somewhat impractical to effectively control or maintain the desired vacuum level for efficient drainage. Further, as only a small degree of vacuum can be created, it dissipates rapidly as the container fills with fluid. [0006] Another known type of equipment for the extraction and collection of wound fluid employs a canister containing a partial vacuum that can be connected to the tube via a control valve providing some degree of vacuum control. The canister has to be replaced periodically as the vacuum reduces.

[0007] More recent developments have provided a disposable container connected to a re-useable battery powered electronically driven pump, allowing greater patient mobility. However, monitoring and controlling pressure to maintain a required vacuum can be challenging. Also, power management and ease of use can be problematic.

[0008] Embodiments of the present seek to provide a wound drainage apparatus and/or method of operation/control thereof that help(s) to alleviate one or more issues with known devices/practices, or at least provides a useful alternative.

[0009] It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country.

SUMMARY

[0010] With the aforementioned in mind, an aspect of the present invention provides a method of operating an apparatus configured for creating negative pressure to remove wound fluid from a wound, the apparatus having a housing containing a source of negative pressure, a pressure sensor configured to measure pressure in a fluid flow path configured to flu idical ly connect the wound and the source of negative pressure; a controller configured to control activation and deactivation of the source of negative pressure, the controller further configured to determine a pressure measurement based on the pressure measured by the pressure sensor, wherein the pressure sensor is controlled by the controller to periodically measure an instantaneous pressure, wherein, if the instantaneous pressure is equal to a target pressure, the source of negative pressure is not operated, and if the instantaneous pressure differs from the target pressure by a preset amount, the source of negative pressure is operated.

[0011 ] The instantaneous pressure may be checked periodically every few seconds, preferably between 2 and 5 seconds, more preferably around 3 seconds. The controller may include a timer for timing the periodic instantaneous pressure check. The source of negative pressure can be deactivated once the target pressure is reached, such as by the pressure sensor measuring the instantaneous pressure to be at least equal to the target pressure.

[0012] The source of negative pressure can be controlled to achieve at least the target pressure by comparing the instantaneous pressure measured by the pressure sensor to the target pressure.

[0013] For example, the source of negative pressure may include a pump. The pump may be run to achieve at least the target pressure. The pump may be run to achieve a desired or preset pressure above the target pressure, such as 5% measured pressure above the target pressure. That is, the target pressure can be a minimum pressure sought to be achieved by operation of the pump, plus a preset or predetermined excess pressure.

[0014] The apparatus can commence a timer once the pressure is at least at the target pressure or at the desired/preset pressure, or therebetween. With the source of negative pressure not operating (e.g. the pump is deactivated/not pumping), if the instantaneous pressure does not change significantly over a predetermined period, a blockage alert is given by the apparatus. The predetermined period may be 30 seconds or more, preferably around 60 seconds.

[0015] When the source of negative pressure is operating, such as when trying to return the instantaneous pressure back to the target or preset/predetermined pressure, the controller can monitor via a timer how long the source of negative pressure is operating. If the source of negative pressure operates continuously for at least a predetermined period, such as 30 seconds, 60 seconds or other predetermined period, the controller can cease the source of pressure operating and can give a leakage alert. The leakage alert can be a visual indication, such as a steady or intermittent light, and/or an audible alert, such as a ‘beep’ or series or pattern of ‘beeps’ or other audible sound(s), and/or vibration.

[0016] The instantaneous pressure read from the pressure sensor can be in analogue to digital converter counts (ADC counts) by an A-D converter functionally (e.g. electrically) connected to the pressure sensor and the controller.

[0017] When the instantaneous pressure is at least equal to the target pressure or to the preset/predetermined pressure, the source of negative pressure (e.g. the pump) can be switched off and the apparatus can enter a sleep mode, thereby conserving power.

[0018] It will be appreciated that the apparatus can include battery power, which may include one or more replaceable and/or rechargeable batteries. For example, the housing can include a space for one or more batteries. The housing can include an openable or removeable cover for access to insert and/or replace batteries.

[0019] The leakage alert may be cleared by the apparatus ‘on’ then ‘off’, or ‘off’ then ‘on’, or by activating a reset control, such as an external reset button.

[0020] Embodiments can include commencing a timer to maintain a count of the amount of time since the source of negative pressure (e.g. a pump) is OFF after the target pressure or preset/predetermined pressure is achieved. [0021] Embodiments can include the apparatus being controlled to activate (e.g. ‘wake up’ from a sleep mode) periodically (e.g. every 3 secs) to check the pressure (instantaneous pressure check).

[0022] If there is a pressure increase sensed by the pressure sensor, the controller can switch ON the source of negative pressure (e.g the pump) to return the instantaneous pressure back to the target or present/predetermined pressure. However, the apparatus can continue to accumulate a timer period/count if the difference between the instantaneous pressure and the target/present/predetermined pressure is less than a predetermined amount (aka ‘blockage time’), such as a predetermined number of ADC counts e.g. 500 ADC counts.

[0023] It will be appreciated that any amount/period of time measured by the controller can be related to counts of the ADC.

[0024] When the timer/count reaches a preset amount, if the difference between the instantaneous pressure and the target/preset/predetermined pressure does not breach the predetermined amount (e.g. 500 ADC counts or other predetermined value) the apparatus (e.g. by the controller) determines a blockage and can optionally provide a blockage alert.

[0025] The blockage alert can be visual, audible and/or tactile. One or more visual alerts can be by visual indication e.g. one or more steady or intermittent lights. One or more audible indications can be by a single, steady ‘beep’ or a number or pattern of ‘bleeps’. One or more tactile indications can be by a continuous or intermittent vibration.

[0026] At any wake-up interval (e.g. every 3 seconds), when the difference between the instantaneous pressure and the target or preset/predetermined pressure is more than the predetermined amount (e.g. 500 ADC counts), the controller determines that the blockage situation has been cleared. The blockage alert can then be cleared (which can be automatically cleared by determination by the controller) and the controller recommences operation of the source of negative pressure to achieve the required target pressure or the preset/predetermined pressure i.e. returning to ‘normal’ apparatus operation.

[0027] Embodiments can include a tolerance range, which can help cater for pressure measurement error of the target pressure or the preset/predetermined pressure.

[0028] The tolerance range may be up to +/-10%, preferably within +/-5%, more preferably within +/-2%, of the target pressure. For example, embodiments may include choosing the target pressure as -75mmHg, -lOOmmHg or -125 mmHg (such as by use of a target pressure selector or controller preset, e.g. using a change pressure button on the housing of the apparatus).

[0029] In use, embodiments can include starting the apparatus i.e. by operating an ON switch/button on the housing. The controller can include or have access to control software. The controller effects starting (run) of the source of negative pressure (e.g. the pump) to achieve the required preset or predetermined pressure e.g. by continuously comparing the instantaneous pressure read from the pressure sensor (such as in ADC counts).

[0030] Embodiments can include, when the instantaneous pressure is equal to the preset or predetermined pressure lowest pressure of the tolerance range (for example - 5%) (e.g. bottom of the tolerance range/band in Figure 3), the source of negative pressure can be switched off and the controller can instruct the apparatus to go into sleep mode (to conserve power).

[0031 ] For example, if the preset/predetermined pressure is -1 OOmmHG, the source of negative pressure is stopped at -lOOmmHg - 5mmHg = -105mmHg. The instantaneous pressure can be stored to memory. [0032] Periodically, (such as every 3 seconds), the controller can check the instantaneous pressure from the pressure sensor. The controller can come out of a sleep mode to check the instantaneous pressure, thereby saving power during sleep i.e. wake up, take pressure measurement, go to sleep.

[0033] Following waking up and measuring the instantaneous pressure, if the instantaneous pressure is within an expected/preset tolerance band (e.g. +/- 5% tolerance), the controller can take no further action other than to go back into sleep mode, (to be woken up after set period e.g. 3 seconds, to repeat the check.

[0034] However, after the waking up, if the controller determines that the instantaneous pressure is a greater pressure i.e. more positive (since it is a negative pressure) than the preset/predetermined pressure (+ 5% tolerance, as it is negative pressure), the source of negative pressure (e.g. the pump) is started immediately to re-establish the preset/predetermined pressure (-5% tolerance).

[0035] Once the preset/predetermined pressure is achieved, the source of negative pressure is switched off and the controller returns to sleep mode.

[0036] It will be appreciated that the above steps can repeat to maintain the preset/predetermined pressure and also conserve power.

[0037] For one or more embodiments, rate of leakage (LR) may be determined by leakage over time, such as Leakage rate (LR) = 5P (Pressure rise)/5T (Time).

[0038] The LR may be updated periodically, such as every 5 minutes or other preferred time period, to make the determination more accurate over time. This can be achieved by taking the difference between IP and preset/predetermined pressure (IP - Preset Pressure) and calculating that difference over the time the source of negative pressure (e.g. the pump) was OFF. [0039] Embodiments can include a negative pressure wound therapy device can include a device housing, a negative pressure source supported by the device housing, the negative pressure source configured to provide negative pressure to a wound (such as covered by a wound dressing), and a container configured to be in fluid communication with the negative pressure source and the wound, the container can store fluid (e.g. wound exudate/liquid) aspirated from the wound.

[0040] Embodiments can include an apparatus configured for creating negative pressure to remove wound fluid from a wound or wound dressing. The apparatus can have a housing containing a source of negative pressure, a pressure sensor configured to measure pressure in a fluid flow path fluidically connecting the wound and the source of negative pressure; a controller configured to control activation and deactivation of the source of negative pressure, a removable container for wound fluid from the wound, wherein the controller further configured to determine a pressure measurement based on the pressure measured by the pressure sensor, wherein the pressure sensor periodically measures an instantaneous pressure, wherein, if the instantaneous pressure is equal to a target pressure, the source of negative pressure is not operated, and if the instantaneous pressure differs from the target pressure by a preset amount, the source of negative pressure is operated.

[0041] The container can include a flexible tube (which may be removable from the container) connectable to a further tube providing a flow path for fluid from a wound or wound dressing. The flexible tube may be releasably retained by at least one retainer provided on the housing. The at least one retainer may include at least one friction or interference fit retainer for releasably retaining the flexible tube.

[0042] The container and the housing may be configured for relative rotation to releasably connect the container to and/or to release the container from the housing. Relative rotation of the container and the housing can connect the container to the housing and seal respective flow path connectors of the housing and the container to provide a continuous fluid flow path between the container and the housing.

[0043] The container can capture liquid from the wound and/or the wound dressing via the flow path, and the container can include a filter medium to filter liquid and particulate matter from air flowing to the housing.

[0044] The housing and the container may have respective curved facing surfaces when connected, at least one of the respective curved facing surfaces including engagement location means and/or relative rotation stop means to provide a positive final engagement position between the housing and the container.

[0045] The housing can include at least one of a visual pressure set indicator, an on-off control and a preset/reset control, or a combination of any two or more thereof.

[0046] The controller may be configured to periodically measure instantaneous pressure via the pressure sensor. The instantaneous pressure may be measured periodically every few seconds, preferably between 2 and 5 seconds, more preferably around 3 seconds. The source of negative pressure may be controlled by the controller to operate to achieve a preset negative pressure greater than the target pressure.

[0047] The controller can include a timer (such as a counter) and the controller is configured to commence the timing (or count) once the instantaneous pressure is at least at the target pressure or at the preset negative pressure, or therebetween.

[0048] The controller can include means to provide a blockage alert if the instantaneous pressure does not change significantly over a predetermined period while the source of negative pressure is not operating and/or including a leakage alert if the source of negative pressure operates continuously for at least a predetermined period, the controller ceases the source of pressure operating and effects the leakage alert.

[0049] When the instantaneous pressure is at least equal to the target pressure or to the preset negative pressure, the source of negative pressure is switched off by the controller and the apparatus is controlled by the controller to enter a sleep mode.

[0050] A timer or counter can be commenced by the controller to maintain a count of the amount of time since the source of negative pressure is OFF after the target pressure or the preset negative pressure is achieved.

[0051 ] The apparatus may be controlled by the controller to activate periodically to check the instantaneous pressure.

[0052] Embodiments can include the apparatus controlled by the controller to accumulate a timer period or count if the difference between the instantaneous pressure and the target pressure or the preset negative pressure is less than a predetermined amount of pressure difference. For example, when the timer or the count reaches a preset amount, if the difference between the instantaneous pressure and the target or preset negative pressure does not breach the predetermined amount of pressure difference, the apparatus determines there is a blockage in the flow path and provides a blockage alert.

[0053] Embodiments may include, at any apparatus wake-up interval of the apparatus, when the difference between the instantaneous pressure and the target or preset negative pressure is more than the predetermined amount of pressure difference, the controller determines that the blockage situation has been cleared. The blockage alert may be cleared, and the controller recommences operation of the source of negative pressure to achieve the required target pressure or the preset negative pressure. Embodiments may include the controller determining the pressure difference as an amount of run time of the source of negative pressure or a period of time or counts of the timer. The apparatus may include the controller configured to determine the instantaneous pressure is equal to the preset negative pressure being a lowest pressure (most negative pressure) of a tolerance range, the source of negative pressure is switched off and the controller instructs the apparatus to go into sleep mode.

[0054] Following waking up and measuring the instantaneous pressure, if the instantaneous pressure is determined via the controller and the pressure sensor to be within the tolerance band, the controller can put the apparatus back into sleep mode until the next periodic instantaneous pressure check.

[0055] After the waking up, if the controller determines that the instantaneous pressure is a greater pressure (more positive pressure) than the preset negative pressure that is the most negative pressure of the tolerance band, the source of negative pressure can be run/started to re-establish the preset negative pressure.

[0056] A leakage rate (LR) may be determined by pressure leakage over time. The apparatus may determine the LR is a change in pressure 5P (Pressure rise) I 5T (Time). The LR may be updated periodically by the controller, such as every 5 minutes or other preferred time period, to make the determination more accurate over time. The LR periodic update may include the controller taking the difference between the instantaneous pressure and the preset negative pressure and calculating that difference over the time that the source of negative pressure was OFF.

[0057] It will be appreciated that the apparatus may include control software (such as firmware) programmed into a programme controller of the controller to provide operational control, alerts and measurement instructions for apparatus functionality. BRIEF DESCRIPTION OF THE FIGURES

[0058] One or more embodiments or examples of the present invention will hereinafter be described with reference to the accompanying Figures, in which:

[0059] Figure 1 shows a perspective view of a wound drainage device with container attached for receiving wound fluid according to an embodiment of the present invention.

[0060] Figure 2 shows a perspective view of the container referred to in Figure 1 configured for attachment to a housing of the device of Figure 1 according to an embodiment of the present invention.

[0061 ] Figure 3 shows a partial internal schematic view of an apparatus according to an embodiment of the present invention.

[0062] Figure 4 shows a normal operation methodology for a negative pressure wound therapy apparatus, according to an embodiment of the present invention.

[0063] Figure 5 shows of leakage alert methodology for a negative pressure wound therapy apparatus, according to an embodiment of the present invention.

[0064] Figure 6 shows a blockage alert methodology for a negative pressure wound therapy apparatus, according to an embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT(S)

[0065] In the following detailed description, reference is made to accompanying drawings which form a part of the detailed description. The illustrative embodiments described in the detailed description, depicted in the drawings and defined in the claims, are not intended to be limiting. Other embodiments may be utilised and other changes may be made without departing from the spirit or scope of the subject matter presented.

[0066] It will be readily understood that the aspects of the present disclosure, as generally described herein and illustrated in the drawings can be arranged, substituted, combined, separated and designed in a wide variety of different configurations, all of which are contemplated in this disclosure.

[0067] An apparatus 10 for creating negative pressure to remove wound fluid from a wound includes a housing 12 containing a source of negative pressure 58 (such as a pump), a pressure sensor 56 configured to measure pressure in a fluid flow path configured to flu idical ly connect the wound and the source of negative pressure and a controller 54 configured to control activation and deactivation of the source of negative pressure 58.

[0068] Embodiments can include a container 14 (aka canister or reservoir) that can be removably attached to the housing 12. For example, the housing and the container can include respective interconnectors such that flow path continuity 38 can be established between the source of negative pressure 58 in the housing 12, a canister volume 30, and a passage 32 of the flow path. The respective interconnectors can include container interconnection means 40 provided on a connector 36 of the container and housing interconnection means 62 provided on a connector 60 of the housing. The passage can be within a flexible tube 33 connected to the container 14.

[0069] The housing 12 can include a channel 27, such as an exterior channel, to receive therein the flexible tube 33. The housing can include a retainer arrangement 28 for retaining the tube to the housing, such as a channel restriction/narrowing to retain the tube 33 by interference or pinch fit. It will be appreciated that the tube retainer arrangement 28 does not significantly, or at all, hinder the internal flow path through the tube at the retainer arrangement. [0070] The tube 33 can include a tube connector 34 at a distal end thereof, such as a Luer lock, for connection to a further tube to the wound site or a wound dressing.

[0071] The housing 12 can include a operation control 18, such as an On/Off button, a selector control 26 to select or reset a preset or predetermined pressure, such as -75mm Hg, -100mm Hg or -125mm Hg. Indicator lights 20, 22 and 24 can indicate the respective preset pressure e.g. light 20 for -75mm Hg, light 22 for -100mm Hg and light 24 for -125mm Hg. The selector control can be operated to cycle through the pressure settings until the desired preset pressure is selected, and then released.

[0072] A battery housing cover 16 provides access to internal storage for batteries 50 to power the apparatus. The batteries are electrically connected to the controller and provide power to the source of negative pressure 58.

[0073] Embodiments of the container can include housing engagement means 42 and stop means 44. The housing and container can be interconnected by relative rotation of the housing and container, such that the respective interconnectors engage. The stop means can provide a rotation stop.

Engagement establishes a leak free flow path between the source of negative pressure and the internal volume of the container.

[0074] Embodiments of the container 14 can include a filter medium 62 to prevent fluid (such wound fluid and any particles entrained therein) above a preferred size from entering the source of negative pressure. The filter medium can include a micro-porous synthetic filter material.

[0075] The controller can be configured to determine a pressure measurement based on the pressure measured by the pressure sensor 56. For example, the pressure senor 56 can periodically measure an instantaneous pressure the flow path. [0076] According to one or more embodiments, when the instantaneous pressure IP is equal to a target pressure TP, the source of negative pressure 58 is not operated. However, when the instantaneous pressure IP differs from the target pressure TP by a preset amount, the source of negative pressure 58 is operated.

[0077] According to one or more embodiments, in use, the required pressure (target pressure) can be set, such as the aforementioned choice of -75mm Hg, - 100mm Hg or -125 mm Hg using the change pressure selector control 26 (e.g. pressure selector button) on the housing.

[0078] When the apparatus is started, the controller controls starting the source of negative pressure, such as the pump, to achieve the required target pressure by continuously comparing the instantaneous pressure IP read from the pressure sensor (such as in ADC counts).

[0079] When the instantaneous pressure is equal to the target pressure, the source of negative pressure is switched off and the controller puts the apparatus into a sleep mode (which conserves power).

[0080] Periodically, such as at 3 second interval, the apparatus wakes from sleep mode and the controller checks the instantaneous pressure from the pressure sensor. If the instantaneous pressure (IP) is equal to the target pressure, the controller can take no further action and the apparatus goes back to sleep mode, to awake again after next period (e.g. 3 seconds) to re-check the IP.

[0081 ] After waking, if the controller determines that the instantaneous pressure is greater than the target pressure (since it is a negative pressure), the source of negative pressure (e.g. pump) is controlled to run to achieve the target pressure. Once the target pressure is achieved, the source of negative pressure is deactivated and the controller returns the apparatus to sleep mode. The above steps can be repeated to maintain the target pressure of the apparatus and also conserve power.

[0082] Leakage detection and recovery. Embodiments can include the controller maintaining a timer to monitor the amount of time that the source of negative pressure is ON when the source of negative pressure is operating to reach the target pressure. When this timer reaches a predetermined count/amount, such as 60 seconds, a leakage alert (alarm) is reached because the apparatus was not able to reach the target pressure within the count/amount (e.g. within a 60 threshold), therefore indicating a leak.

[0083] Embodiments can include the leakage alert/alarm able to be cleared, such as by switching ON and OFF the source of negative pressure.

[0084] Blockage detection and recovery. After the target pressure is achieved, and the source of negative pressure is switched OFF (as per the steps shown in the apparatus operation above), the controller can start a timer to maintain the amount of time since the source of negative pressure was deactivated once the targe pressure was reached, as sensed by the pressure sensor.

[0085] Embodiments can include the checking the IP periodically, such as every 3 seconds. Although a period of 3 seconds is used by way of example, other periods may be programmed into the controller, such as every 4 seconds or every 5 seconds.

[0086] If there is a pressure rise, the controller can activate the source of negative pressure to return the pressure to the target pressure. However, the controller can accumulate a blockage time if the difference between the instantaneous pressure (IP) and the target pressure TP is less than a predetermined time/count, such as 500 ADC counts. [0087] When this blockage timer reaches a preset time/count, such as 5 minutes or ADC count equivalent, if the difference between the IP and the TP does not breach the preset time/count e.g. the 500 ADC count), the controller determines there is a blockage and provides a blockage alert/alarm.

[0088] Any aforementioned alert/alarm may be visual (e.g. light(s)), audible (e.g. sound(s)) and/or tactile (e.g. vibration(s)).

[0089] At any wake up interval (such as each 3 second interval), when the difference between the IP and the target pressure is more than the preset time (e.g. 500 ADC counts), the blockage situation is interpreted as being cleared. At this point, the blockage alert/alarm is cleared and the control effects re-activation of the source of negative pressure (e.g. the pump) to achieve the target pressure (just as normal apparatus operation routine).

[0090] Figure 4 shows a chart of pressure versus time. The slope of pressure versus time graph represents time rate of change of pressure, such as representing leakage rate (LR) if the source of negative pressure is not operating during the pressure change (5P) over time. A very shallow, near horizontal or horizontal slope of such a graph can indicate a blockage due to zero or almost zero pressure change over time. A steeper slope indicating relatively rapid change of pressure over time can indicate leakage.

[0091 ] One or more further embodiments can include a tolerance band around the target pressure, such as shown by way of example in Figure 4. For example, a +/- % of the target pressure, such as +/- 5% of the target pressure.

[0092] The required target pressure is set (e.g. the aforementioned -75mm Hg, -100mm Hg or -125mm Hg) e.g. using the change pressure selector control 26 on the housing. When the apparatus is activated, the controller activates the source of negative pressure to achieve the required target pressure. The controller can operate, such as through operative computer firmware stored on a circuit board 52 for the controller, by continuously comparing the instantaneous pressure (IP) read from the pressure sensor 56 (e.g. in ADC counts.)

[0093] When the instantaneous pressure is beyond the target pressure and reaches the tolerance pressure PT e.g. - 5% (bottom of tolerance band), the source of negative pressure is switched off and the controller, via the control software, instructs the apparatus to go into sleep mode (which helps to conserve power). For example, if the target pressure is -100mm Hg and the tolerance band is +/- 5%, the source of negative pressure is deactivated at -100 - 5 = -105mm Hg.

[0094] Periodically, such as 3 secs or ADC count equivalent (though other periods/counts are envisaged to fall within the scope of embodiments of the present invention), the apparatus awakens, and the controller checks the instantaneous pressure from the pressure sensor.

[0095] If the instantaneous pressure is within the target pressure tolerance band (e.g. +-5% tolerance), the controller does not activate the source of negative pressure, and the apparatus goes back to sleep mode - to be woken up after the check period (e.g. the 3 second period) to repeat the IP check.

[0096] After waking up, if the controller determines that the instantaneous pressure is a higher pressure than the target pressure i.e. less negative pressure (e.g. + 5% tolerance, as its negative pressure - such as -95mm Hg compared to a target pressure 100mm Hg), the source of negative pressure is activated to achieve the lowest tolerance preset/predetermined pressure (such as -5% tolerance - e.g. 105mm Hg compared to the 100mm Hg target pressure). Once the preset pressure is achieved the source of negative pressure is deactivated and the controller returns the apparatus to sleep mode. Embodiments can include repeating the aforementioned steps to maintain the preset/predetermined tolerance pressure and also conserve power. [0097] Embodiments may include additional features, such as the controller operating for the apparatus to maintain a Leakage Rate (LR) (rate of leakage) which is calculated by leakage over time i.e. Leakage Rate (LR) = ^(Pressure rise) I b(Time).

[0098] The LR can be updated periodically, such as every 5 minutes or other preferred period, to make it more accurate over time. This can be done by taking the difference i.e. instantaneous pressure - preset pressure and calculating that difference over the time the source of negative pressure was deactivated/switched OFF.

[0099] Embodiments may include leakage detection and recovery. When the source of negative pressure (e.g. pump) is operating to reach a preset pressure, a timer can be running, such as controlled by the controller, to record the amount of time that the source of negative pressure is ON. When this timer reaches a predetermined value/count (such as 60 seconds, though other values may be adopted), a leakage alert/alarm can be given, meaning that the preset pressure was not achievable within the timer period (e.g. within 60 seconds) so there must be a leakage. The leakage alert/alarm may be cleared by switching ON and OFF the apparatus/source of negative pressure.

[00100] Embodiments may include blockage detection and recovery. After the preset pressure is achieved, and the source of negative pressure is switched OFF (such as per the steps shown in apparatus operation above), the instantaneous pressure (IP) can be saved (P1 ). At this point the controller starts maintaining the amount of time since the source of negative pressure was switched OFF. When this time reaches a predetermined amount/count (e.g. 5 minutes), the controller checks and can determine a blockage and provide a blockage alert/alarm.

[00101 ] Embodiments can include the blockage alert/alarm provided if a leakage rate LR (over a period of time, such as 5 mins) is equal to or less than a system leakage rate, such as a system leakage rate comprising a wound dressing leakage rate + an inherent apparatus leakage rate, to give the blockage alert/alarm.

[00102] Once the blockage alert/alarm has been indicated (such as via an illumination on and/or sound from the apparatus), the controller effects the IP pressure check via the pressure sensor periodically e.g. every 3 seconds, to check if a rate of change in pressure (instantaneous pressure - P1 and preferably calculated via ADC counts) is greater than the rate of change in pressure (RP1 , preferably in ADC counts) when the time taken for the pressure to reach the upper bound of error tolerance band (e.g. from lower bound) is equal to a predetermined value/count e.g. 5 minutes (constant value).

[00103] If the instantaneous pressure + RP1 is greater than P1 , the leakage rate LR can be determined. If the LR is greater than the overall system leakage rate, preferably being the ideal wound dressing leakage rate + the inherent apparatus leakage rate, the blockage alert/alarm is deemed cleared.

[00104] The controller can save the instantaneous Pressure (P1 ) for the next round of blockage detection protocol. Also, the source of negative pressure may be reactivated to achieve the preset pressure (just as normal device operation routine).

[00105] The controller can cause the source of negative pressure to run to achieve the preset pressure if the pressure rises above the error tolerance e.g. the 5%, from the preset pressure but keep reporting the blockage alert/alarm. This is to maintain the pressure within accepted error tolerance. Thus, the indication of blockage need not be based on pump function (ON/OFF) but the rate of change of leakage

[00106] As exemplified in one embodiment in Figure 5, if a negative pressure of a set point pressure +5% is not reached within a period of time, such as 60 seconds, form commencing running the source of negative pressure, a leakage is deemed detected. A leakage indication is given. The apparatus can be controlled by the controller to cease operating the source of negative pressure until the leakage is sealed. The apparatus can recommence creating negative pressure by operation of the power control.

[00107] As exemplified in one embodiment in Figure 6, with the source of negative pressure stopped, if a change in negative pressure over a set period of time, 5P (change in Pressure )/bt (Time), is detected by the controller via the pressure sensor to be less than or equal to an inherent system leakage rate for a set period of time, e.g. 5 mins, a blockage alert is given.

[00108] In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. , to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

CLAIMS:

1 . A method of operating an apparatus configured for creating negative pressure to remove wound fluid from a wound, the apparatus having a housing containing a source of negative pressure, a pressure sensor configured to measure pressure in a fluid flow path flu idical ly connecting the wound and the source of negative pressure; a controller configured to control activation and deactivation of the source of negative pressure, the controller further configured to determine a pressure measurement based on the pressure measured by the pressure sensor, wherein the pressure sensor periodically measures an instantaneous pressure, wherein, if the instantaneous pressure is equal to a target pressure, the source of negative pressure is not operated, and if the instantaneous pressure differs from the target pressure by a preset amount, the source of negative pressure is operated, and wherein, when the instantaneous pressure is equal to the preset negative pressure of a tolerance range, the source of negative pressure is switched off and the controller puts the apparatus into a sleep mode, and wherein the apparatus is controlled by the controller to activate periodically to check the instantaneous pressure.

2. The method of claim 1 , wherein the instantaneous pressure is measured periodically every few seconds, preferably between 2 and 5 seconds, more preferably around 3 seconds.

3. The method of claim 1 or claim 2, wherein the source of negative pressure is controlled to operate to achieve a preset negative pressure greater than the target pressure.

4. The method of claim 3, wherein the preset negative pressure is around 5% more negative in pressure than the target pressure.

5. The method of any one of the preceding claims, wherein the controller is configured to commence a timer once the instantaneous pressure is at least at the target pressure or at the preset negative pressure, or therebetween.

6. The method of any one of the preceding claims, wherein, if the instantaneous pressure does not change significantly over a predetermined period while the source of negative pressure is not operating, a blockage alert is given by the apparatus.

7. The method of claim 6, wherein the predetermined period is 30 seconds or more, preferably around 60 seconds.

8. The method of any one of the preceding claims, wherein, when the source of negative pressure is operating, the controller times for how long the source of negative pressure is operating.

9. The method of claim 8, wherein, if the source of negative pressure operates continuously for at least a predetermined period, the controller ceases the source of pressure operating and effects a leakage alert.

10. The method of claim 9, wherein, the at least a predetermined period is 30 seconds or more, preferably at least 60 seconds.

11 . The method of claim 1 , wherein, a timer is commenced to maintain a count of the amount of time since the source of negative pressure is OFF after the target pressure or the preset negative pressure is achieved.

12. The method of claim 11 , wherein, if there is sufficient pressure increase sensed by the pressure sensor differing from the target pressure or the preset negative pressure, the controller commences the source of negative pressure operating to return the instantaneous pressure back to the target or present negative pressure.

13. The method of any one of the preceding claims, wherein, the apparatus is controlled by the controller to accumulate a timer period or count if the difference between the instantaneous pressure and the target pressure or the preset negative pressure is less than a predetermined amount of pressure difference.

14. The method of claim 13, wherein, when the timer or the count reaches a preset amount, if the difference between the instantaneous pressure and the target or preset negative pressure does not breach the predetermined amount of pressure difference, the apparatus determines there is a blockage in the flow path and provides a blockage alert.

15. The method of claim 13 or claim 14, wherein, at any apparatus wake-up interval, when the difference between the instantaneous pressure and the target or preset negative pressure is more than the predetermined amount of pressure difference, the controller determines that the blockage situation has been cleared.

16. The method of claim 15, wherein the blockage alert is cleared, and the controller recommences operation of the source of negative pressure to achieve the required target pressure or the preset negative pressure.

17. The method of any one of claims 13 to 16, wherein the pressure difference is determined as an amount of run time of the source of negative pressure or a period of time or counts of the timer.

18. The method of claim 1 , wherein, following waking up and measuring the instantaneous pressure, if the instantaneous pressure is within the tolerance band, the controller puts the apparatus back into sleep mode until the next periodic instantaneous pressure check.

19. The method of claim 18, wherein, after the waking up, if the controller determines that the instantaneous pressure is a greater pressure than the preset negative pressure that is the most negative pressure of the tolerance band, the source of negative pressure is started to re-establish the preset negative pressure.

20. The method of any one of claims 1 to 19, wherein a leakage rate (LR) is determined by pressure leakage over time.

21 . The method of claim 20, wherein LR is determined as change in pressure 5P (Pressure rise) 15T (Time).

22. The method of claim 21 , wherein the LR is updated periodically, such as every 5 minutes or other preferred time period, to make the determination more accurate over time.

23. The method of claim 22, wherein the LR periodic update includes taking the difference between the instantaneous pressure and the preset negative pressure and calculating that difference over the time that the source of negative pressure was OFF.

24. An apparatus configured for creating negative pressure to remove wound fluid from a wound or wound dressing, the apparatus having a housing containing a source of negative pressure, a pressure sensor configured to measure pressure in a fluid flow path flu idical ly connecting the wound and the source of negative pressure; a controller configured to control activation and deactivation of the source of negative pressure, a removable container for wound fluid from the wound, wherein the controller further configured to determine a pressure measurement based on the pressure measured by the pressure sensor, wherein the pressure sensor periodically measures an instantaneous pressure, wherein, if the instantaneous pressure is equal to a target pressure, the source of negative pressure is not operated, and if the instantaneous pressure differs from the target pressure by a preset amount, the source of negative pressure is operated, and wherein, the apparatus is configured such that, when the instantaneous pressure is equal to the preset negative pressure of a tolerance range, the source of negative pressure is switched off and the controller instructs the apparatus into a sleep mode, and wherein the apparatus is configured such that the controller activates periodically to check the instantaneous pressure via the pressure sensor.

25. The apparatus of claim 24, wherein the container includes a flexible tube connectable to a further tube providing a flow path for fluid from a wound or wound dressing.

26. The apparatus of claim 25, wherein the flexible tube is releasably retained by at least one retainer provided on the housing.

27. The apparatus of claim 26, wherein the at least one retainer includes at least one friction or interference fit retainer for releasably retaining the flexible tube.

28. The apparatus of any one of claims 24 to 27, wherein the container and the housing are configured for relative rotation to releasably connect the container to and/or to release the container from the housing.

29. The apparatus of claim 28, wherein, relative rotation of the container and the housing to connect the container to the housing seals respective flow path connectors of the housing and the container to provide a continuous fluid flow path between the container and the housing.

30. The apparatus of any one of claims 24 to 29, wherein the container captures liquid from the wound via the flow path, and the container includes a filter medium to filter liquid and particulate matter from air flowing to the housing.

31 . The apparatus of any one of claim 24 to 30, wherein the housing and the container have respective curved facing surfaces when connected, at least one of the respective curved facing surfaces including engagement location means and/or relative rotation stop means to provide a positive final engagement position between the housing and the container.

32. The apparatus of any one of claims 24 to 31 , the housing including at least one of a visual pressure set indicator, an on-off control and a preset/reset control, or a combination of any two or more thereof.

33. The apparatus of any one of claims 24 to 32, wherein the controller is configured to periodically measure instantaneous pressure via the pressure sensor.

34. The apparatus of claim 33, wherein the instantaneous pressure is measured periodically every few seconds, preferably between 2 and 5 seconds, more preferably around 3 seconds.

35. The apparatus of claim 34, wherein the source of negative pressure is controlled to operate to achieve a preset negative pressure greater than the target pressure.

36. The apparatus of claim 35, wherein the controller includes a timer and the controller is configured to commence the timing once the instantaneous pressure is at least at the target pressure or at the preset negative pressure, or therebetween.

37. The apparatus of claim 36, the controller including a blockage alert if the instantaneous pressure does not change significantly over a predetermined period while the source of negative pressure is not operating and/or including a leakage alert if the source of negative pressure operates continuously for at least a predetermined period, the controller ceases the source of pressure operating and effects the leakage alert.

38. The apparatus of claim 24, wherein, a timer is commenced to maintain a count of the amount of time since the source of negative pressure is OFF after the target pressure or the preset negative pressure is achieved.

39. The apparatus of claim 24, wherein, if there is sufficient pressure increase sensed by the pressure sensor differing from the target pressure or the preset negative pressure, the controller commences the source of negative pressure operating to return the instantaneous pressure back to the target or present negative pressure.

40. The apparatus of any one of claims 24 to 39, wherein, the apparatus is controlled by the controller to accumulate a timer period or count if the difference between the instantaneous pressure and the target pressure or the preset negative pressure is less than a predetermined amount of pressure difference.

41 . The apparatus of claim 40, wherein, when the timer or the count reaches a preset amount, if the difference between the instantaneous pressure and the target or preset negative pressure does not breach the predetermined amount of pressure difference, the apparatus determines there is a blockage in the flow path and provides a blockage alert.

42. The apparatus of claim 41 , wherein, at any apparatus wake-up interval, when the difference between the instantaneous pressure and the target or preset negative pressure is more than the predetermined amount of pressure difference, the controller determines that the blockage situation has been cleared.

43. The apparatus of claim 42, wherein the blockage alert is cleared, and the controller recommences operation of the source of negative pressure to achieve the required target pressure or the preset negative pressure.

44. The apparatus of any one of claims 40 to 43, wherein the pressure difference is determined as an amount of run time of the source of negative pressure or a period of time or counts of the timer.

45. The apparatus of claim 44, wherein, when the instantaneous pressure is equal to the preset negative pressure being a lowest pressure (most negative pressure) of a tolerance range, the source of negative pressure is switched off and the controller instructs the apparatus to go into sleep mode.

46. The apparatus of claim 45, wherein, following waking up and measuring the instantaneous pressure, if the instantaneous pressure is within the tolerance band, the controller can put the apparatus back into sleep mode until the next periodic instantaneous pressure check.

47. The apparatus of claim 46, wherein, after the waking up, if the controller determines that the instantaneous pressure is a greater pressure (more positive pressure) than the preset negative pressure that is the most negative pressure of the tolerance band, the source of negative pressure is started to re-establish the preset negative pressure.

48. The apparatus of any one of claims 45 to 48, wherein, a leakage rate (LR) is determined by pressure leakage over time.

49. The apparatus of claim 48, wherein LR is determined as change in pressure 5P (Pressure rise) 15T (Time).

50. The apparatus of claim 49, wherein the LR is updated periodically, such as every 5 minutes or other preferred time period, to make the determination more accurate over time.

51 . The apparatus of claim 50, wherein the LR periodic update includes taking the difference between the instantaneous pressure and the preset negative pressure and calculating that difference over the time that the source of negative pressure was OFF.