Patent Description:
Embodiments of the present disclosure relate to methods (not claimed) and apparatuses for dressing and treating a wound with negative or reduced pressure therapy or topical negative pressure (TNP) therapy. In particular, but without limitation, embodiments disclosed herein relate to negative pressure therapy devices, methods (not claimed) for controlling the operation of TNP systems, and methods (not claimed) of using TNP systems. Relevant prior art can be found in: <CIT>, <CIT>, <CIT>, and <CIT>.

An apparatus for applying negative pressure to a wound is disclosed. The apparatus includes a source of negative pressure, a valve, and a controller. The source of negative pressure is in fluidic communication via a flow path with a wound dressing placed over a wound. The source of negative pressure provides negative pressure under the wound dressing. The valve controls supply of positive pressure via the flow path to the wound dressing. The controller is configured to: operate the source of negative pressure to supply negative pressure via the flow path to the wound dressing, determine a pressure difference between a pressure under the wound dressing and a pressure setting, generate a control signal according at least to the pressure difference, and using the control signal, operate the valve to supply positive pressure via the flow path to the wound dressing so that the pressure under the wound dressing reaches the pressure setting. The controller is further configured to operate the valve to supply positive pressure when the controller applies intermittent negative pressure wound therapy to the wound, and to output the control signal to the valve to operate the valve to vary an amount of positive pressure provided to the fluid flow path.

The apparatus of the preceding paragraph can include one or more of the following features: The control signal can be a pulse-width modulation (PWM) signal, and the controller can vary a duty cycle of the PWM signal to operate the valve to supply positive pressure via the flow path to the wound dressing. The controller can generate the control signal using a proportional-integral-derivative (PID) calculation, and an error of the PID calculation can be the pressure difference. The controller can: at a first time, determine that an accumulated error of the PID calculation is negative, and set an integral term of the PID calculation to be <NUM> and the accumulated error to be <NUM> in response to a determination that the accumulated error is negative. The controller can: at a first time, determine that the error is negative, and set an accumulated error of the PID calculation to be greater than a sum of the accumulated error and the error in response to a determination that the error is negative. The valve can be positioned before an exhaust for the source of negative pressure. The valve can be a solenoid valve.

A method (not claimed) of operating or manufacturing the apparatus of the preceding two paragraphs is also disclosed.

In some embodiments, a method (not claimed) for applying negative pressure therapy to a wound is disclosed. The method can include: providing negative pressure via a flow path to a wound dressing placed over a wound; determining a pressure difference between a pressure under the wound dressing and a pressure setting; generating a control signal according at least to the pressure difference; and using the control signal, operating a valve to supply positive pressure via the flow path to the wound dressing so that the pressure under the wound dressing reaches the pressure setting.

The method of the preceding paragraph can include one or more of the following features: The operating the valve to supply positive pressure can be performed when intermittent negative pressure wound therapy is being applied to the wound. The control signal can be a pulse-width modulation (PWM) signal, and the operating the valve to supply positive pressure can be performed by varying a duty cycle of the PWM signal. The generating the control signal can include generating the control signal using a proportional-integral-derivative (PID) calculation, and an error of the PID calculation can be the pressure difference. The valve can be a solenoid valve.

The present disclosure relates to methods and apparatuses for dressing and treating a wound with reduced pressure therapy or topical negative pressure (TNP) therapy. In particular, but without limitation, embodiments of this disclosure relate to negative pressure therapy apparatuses, methods for controlling the operation of TNP systems, and methods of using TNP systems.

Many different types of wound dressings are known for aiding in the healing process of a human or animal. These different types of wound dressings include many different types of materials and layers, for example, gauze, pads, foam pads or multi-layer wound dressings. TNP therapy, sometimes referred to as vacuum assisted closure, negative pressure wound therapy, or reduced pressure wound therapy, can be a beneficial mechanism for improving the healing rate of a wound. Such therapy is applicable to a broad range of wounds such as incisional wounds, open wounds and abdominal wounds or the like.

TNP therapy can assist in the closure and healing of wounds by reducing tissue oedema, encouraging blood flow, stimulating the formation of granulation tissue, removing excess exudates, and reducing bacterial load and thus, infection to the wound. Furthermore, TNP therapy can permit less outside disturbance of the wound and promote more rapid healing.

As is used herein, reduced or negative pressure levels, such as -X mmHg, represent pressure levels that are below atmospheric pressure, which typically corresponds to <NUM> mmHg (or <NUM> atm, <NUM> inHg, <NUM> kPa, <NUM> psi, etc.). Accordingly, a negative pressure value of -X mmHg reflects pressure that is X mmHg below atmospheric pressure, such as a pressure of (<NUM>-X) mmHg. In addition, negative pressure that is "less" or "smaller" than -X mmHg corresponds to pressure that is closer to atmospheric pressure (for example, -<NUM> mmHg is less than -<NUM> mmHg). Negative pressure that is "more" or "greater" than -X mmHg corresponds to pressure that is further from atmospheric pressure (for example, -<NUM> mmHg is more than -<NUM> mmHg).

<FIG> illustrates an embodiment of a negative or reduced pressure wound treatment (or TNP) system <NUM> comprising a wound filler <NUM> placed inside a wound cavity <NUM>, the wound cavity sealed by a wound cover <NUM>. The wound filler <NUM> in combination with the wound cover <NUM> can be referred to as wound dressing. A single or multi lumen tube or conduit <NUM> is connected the wound cover <NUM> with a pump assembly <NUM> configured to supply reduced pressure. The wound cover <NUM> can be in fluidic communication with the wound cavity <NUM>. In any of the system embodiments disclosed herein, as in the embodiment illustrated in <FIG>, the pump assembly can be a canisterless pump assembly (meaning that exudate is collected in the wound dressing or is transferred via tube <NUM> for collection to another location). However, any of the pump assembly embodiments disclosed herein can be configured to include or support a canister. Additionally, in any of the system embodiments disclosed herein, any of the pump assembly embodiments can be mounted to or supported by the dressing, or adjacent to the dressing.

The wound filler <NUM> can be any suitable type, such as hydrophilic or hydrophobic foam, gauze, inflatable bag, and so on. The wound filler <NUM> can be conformable to the wound cavity <NUM> such that it substantially fills the cavity. The wound cover <NUM> can provide a substantially fluid impermeable seal over the wound cavity <NUM>. The wound cover <NUM> can have a top side and a bottom side, and the bottom side adhesively (or in any other suitable manner) seals with wound cavity <NUM>. The conduit <NUM> or lumen or any other conduit or lumen disclosed herein can be formed from polyurethane, PVC, nylon, polyethylene, silicone, or any other suitable material.

Some embodiments of the wound cover <NUM> can have a port (not shown) configured to receive an end of the conduit <NUM>. For example, the port can be Renays Soft Port available from Smith & Nephew. In other embodiments, the conduit <NUM> can otherwise pass through or under the wound cover <NUM> to supply reduced pressure to the wound cavity <NUM> so as to maintain a desired level of reduced pressure in the wound cavity. The conduit <NUM> can be any suitable article configured to provide at least a substantially sealed fluid flow pathway between the pump assembly <NUM> and the wound cover <NUM>, so as to supply the reduced pressure provided by the pump assembly <NUM> to wound cavity <NUM>.

The wound cover <NUM> and the wound filler <NUM> can be provided as a single article or an integrated single unit. In some embodiments, no wound filler is provided and the wound cover by itself may be considered the wound dressing. The wound dressing may then be connected, via the conduit <NUM>, to a source of negative pressure, such as the pump assembly <NUM>. The pump assembly <NUM> can be miniaturized and portable, although larger conventional pumps such can also be used.

The wound cover <NUM> can be located over a wound site to be treated. The wound cover <NUM> can form a substantially sealed cavity or enclosure over the wound site. In some embodiments, the wound cover <NUM> can be configured to have a film having a high water vapor permeability to enable the evaporation of surplus fluid, and can have a superabsorbing material contained therein to safely absorb wound exudate. It will be appreciated that throughout this specification reference is made to a wound. In this sense it is to be understood that the term wound is to be broadly construed and encompasses open and closed wounds in which skin is torn, cut or punctured or where trauma causes a contusion, or any other surficial or other conditions or imperfections on the skin of a patient or otherwise that benefit from reduced pressure treatment. A wound is thus broadly defined as any damaged region of tissue where fluid may or may not be produced. Examples of such wounds include, but are not limited to, acute wounds, chronic wounds, surgical incisions and other incisions, subacute and dehisced wounds, traumatic wounds, flaps and skin grafts, lacerations, abrasions, contusions, burns, diabetic ulcers, pressure ulcers, stoma, surgical wounds, trauma and venous ulcers or the like. The components of the TNP system described herein can be particularly suited for incisional wounds that exude a small amount of wound exudate.

Some embodiments of the system are designed to operate without the use of an exudate canister. Some embodiments can be configured to support an exudate canister. In some embodiments, configuring the pump assembly <NUM> and tubing <NUM> so that the tubing <NUM> can be quickly and easily removed from the pump assembly <NUM> can facilitate or improve the process of dressing or pump changes, if necessary. Any of the pump embodiments disclosed herein can be configured to have any suitable connection between the tubing and the pump.

The pump assembly <NUM> can be configured to deliver negative pressure of approximately -<NUM> mmHg, or between about -<NUM> mmHg and <NUM> mmHg in some implementations. Note that these pressures are relative to normal ambient atmospheric pressure thus, -<NUM> mmHg would be about <NUM> mmHg in practical terms. The pressure range can be between about -<NUM> mmHg and -<NUM> mmHg. Alternatively a pressure range of up to -<NUM> mmHg, up to -<NUM> mmHg or over -<NUM> mmHg can be used. Also a pressure range of below -<NUM> mmHg can be used. Alternatively a pressure range of over approximately -<NUM> mmHg, or even <NUM> mmHg, can be supplied by the pump assembly <NUM>.

In operation, the wound filler <NUM> is inserted into the wound cavity <NUM> and wound cover <NUM> is placed so as to seal the wound cavity <NUM>. The pump assembly <NUM> provides a source of a negative pressure to the wound cover <NUM>, which is transmitted to the wound cavity <NUM> via the wound filler <NUM>. Fluid (e.g., wound exudate) is drawn through the conduit <NUM>, and can be stored in a canister. In some embodiments, fluid is absorbed by the wound filler <NUM> or one or more absorbent layers (not shown).

Wound dressings that may be utilized with the pump assembly and other embodiments of the present application include Renasys-F, Renasys-G, Renasys AB, and Pico Dressings available from Smith & Nephew. Further description of such wound dressings and other components of a negative pressure wound therapy system that may be used with the pump assembly and other embodiments of the present application are found in <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>. In other embodiments, other suitable wound dressings can be utilized.

<FIG> illustrates a front view of a pump assembly <NUM> and canister <NUM> according to some embodiments. As is illustrated, the pump assembly <NUM> and the canister are connected, thereby forming a negative pressure wound therapy device. The pump assembly <NUM> can be similar to or the same as the pump assembly <NUM> in some embodiments.

The pump assembly <NUM> includes one or more indicators, such as visual indicator <NUM> configured to indicate alarms and visual indicator <NUM> configured to indicate status of the TNP system. The indicators <NUM> and <NUM> can be configured to alert a user, such as patient or medical care provider, to a variety of operating or failure conditions of the system, including alerting the user to normal or proper operating conditions, pump failure, power supplied to the pump or power failure, detection of a leak within the wound cover or flow pathway, suction blockage, or any other similar or suitable conditions or combinations thereof. The pump assembly <NUM> can comprise additional indicators. The pump assembly can use a single indicator or multiple indicators. Any suitable indicator can be used such as visual, audio, tactile indicator, and so on. The indicator <NUM> can be configured to signal alarm conditions, such as canister full, power low, conduit <NUM> disconnected, seal broken in the wound seal <NUM>, and so on. The indicator <NUM> can be configured to display red flashing light to draw user's attention. The indicator <NUM> can be configured to signal status of the TNP system, such as therapy delivery is ok, leak detected, and so on. The indicator <NUM> can be configured to display one or more different colors of light, such as green, yellow, etc. For example, green light can be emitted when the TNP system is operating properly and yellow light can be emitted to indicate a warning.

The pump assembly <NUM> includes a display or screen <NUM> mounted in a recess <NUM> formed in a case of the pump assembly. The display <NUM> can be a touch screen display. The display <NUM> can support playback of audiovisual (AV) content, such as instructional videos. As explained below, the display <NUM> can be configured to render a number of screens or graphical user interfaces (GUIs) for configuring, controlling, and monitoring the operation of the TNP system. The pump assembly <NUM> comprises a gripping portion <NUM> formed in the case of the pump assembly. The gripping portion <NUM> can be configured to assist the user to hold the pump assembly <NUM>, such as during removal of the canister <NUM>. The canister <NUM> can be replaced with another canister, such as when the canister <NUM> has been filled with fluid.

The pump assembly <NUM> includes one or more keys or buttons configured to allow the user to operate and monitor the operation of the TNP system. As is illustrated, there buttons 212a, 212b, and 212c (collectively referred to as buttons <NUM>) are included. Button 212a can be configured as a power button to turn on/off the pump assembly <NUM>. Button 212b can be configured as a play/pause button for the delivery of negative pressure therapy. For example, pressing the button 212b can cause therapy to start, and pressing the button 212b afterward can cause therapy to pause or end. Button 212c can be configured to lock the display <NUM> or the buttons <NUM>. For instance, button 212c can be pressed so that the user does not unintentionally alter the delivery of the therapy. Button 212c can be depressed to unlock the controls. In other embodiments, additional buttons can be used or one or more of the illustrated buttons 212a, 212b, or 212c can be omitted. Multiple key presses or sequences of key presses can be used to operate the pump assembly <NUM>.

The pump assembly <NUM> includes one or more latch recesses <NUM> formed in the cover. In the illustrated embodiment, two latch recesses <NUM> can be formed on the sides of the pump assembly <NUM>. The latch recesses <NUM> can be configured to allow attachment and detachment of the canister <NUM> using one or more canister latches <NUM>. The pump assembly <NUM> comprises an air outlet <NUM> for allowing air removed from the wound cavity <NUM> to escape. Air entering the pump assembly can be passed through one or more suitable filters, such as antibacterial filters. This can maintain reusability of the pump assembly. The pump assembly <NUM> includes one or more strap mounts <NUM> for connecting a carry strap to the pump assembly <NUM> or for attaching a cradle. In the illustrated embodiment, two strap mounts <NUM> can be formed on the sides of the pump assembly <NUM>. In some embodiments, various of these features are omitted or various additional features are added to the pump assembly <NUM>.

The canister <NUM> is configured to hold fluid (e.g., exudate) removed from the wound cavity <NUM>. The canister <NUM> includes one or more latches <NUM> for attaching the canister to the pump assembly <NUM>. In the illustrated embodiment, the canister <NUM> comprises two latches <NUM> on the sides of the canister. The exterior of the canister <NUM> can formed from frosted plastic so that the canister is substantially opaque and the contents of the canister and substantially hidden from plain view. The canister <NUM> comprises a gripping portion <NUM> formed in a case of the canister. The gripping portion <NUM> can be configured to allow the user to hold the pump assembly <NUM>, such as during removal of the canister from the apparatus <NUM>. The canister <NUM> includes a substantially transparent window <NUM>, which can also include graduations of volume. For example, the illustrated <NUM> canister <NUM> includes graduations of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. Other embodiments of the canister can hold different volume of fluid and can include different graduation scale. For example, the canister can be an <NUM> canister. The canister <NUM> comprises a tubing channel <NUM> for connecting to the conduit <NUM>. In some embodiments, various of these features, such as the gripping portion <NUM>, are omitted or various additional features are added to the canister <NUM>. Any of the disclosed canisters may include or may omit a solidifier.

<FIG> illustrates a rear view of the pump assembly <NUM> and canister <NUM> according to some embodiments. The pump assembly <NUM> comprises a speaker port <NUM> for producing sound. The pump assembly <NUM> includes a filter access door <NUM> with a screw for removing the access door <NUM>, accessing, and replacing one or more filters, such as antibacterial or odor filters. The pump assembly <NUM> comprises a gripping portion <NUM> formed in the case of the pump assembly. The gripping portion <NUM> can be configured to allow the user to hold the pump assembly <NUM>, such as during removal of the canister <NUM>. The pump assembly <NUM> includes one or more covers <NUM> configured to as screw covers or feet or protectors for placing the pump assembly <NUM> on a surface. The covers <NUM> can be formed out of rubber, silicone, or any other suitable material. The pump assembly <NUM> comprises a power jack <NUM> for charging and recharging an internal battery of the pump assembly. The power jack <NUM> can be a direct current (DC) jack. In some embodiments, the pump assembly can comprise a disposable power source, such as batteries, so that no power jack is needed.

The canister <NUM> includes one or more feet <NUM> for placing the canister on a surface. The feet <NUM> can be formed out of rubber, silicone, or any other suitable material and can be angled at a suitable angle so that the canister <NUM> remains stable when placed on the surface. The canister <NUM> comprises a tube mount relief <NUM> configured to allow one or more tubes to exit to the front of the device. The canister <NUM> includes a stand or kickstand <NUM> for supporting the canister when it is placed on a surface. As explained below, the kickstand <NUM> can pivot between an opened and closed position. In closed position, the kickstand <NUM> can be latched to the canister <NUM>. In some embodiments, the kickstand <NUM> can be made out of opaque material, such as plastic. In other embodiments, the kickstand <NUM> can be made out of transparent material. The kickstand <NUM> includes a gripping portion <NUM> formed in the kickstand. The gripping portion <NUM> can be configured to allow the user to place the kickstand <NUM> in the closed position. The kickstand <NUM> comprises a hole <NUM> to allow the user to place the kickstand in the open position. The hole <NUM> can be sized to allow the user to extend the kickstand using a finger.

<FIG> illustrates a view of the pump assembly <NUM> separated from the canister <NUM> according to some embodiments. The pump assembly <NUM> includes a vacuum attachment, connector, or inlet <NUM> through which a vacuum pump communicates negative pressure to the canister <NUM>. The pump assembly aspirates fluid, such as gas, from the wound via the inlet <NUM>. The pump assembly <NUM> comprises a USB access door <NUM> configured to allow access to one or more USB ports. In some embodiments, the USB access door is omitted and USB ports are accessed through the door <NUM>. The pump assembly <NUM> can include additional access doors configured to allow access to additional serial, parallel, or hybrid data transfer interfaces, such as SD, Compact Disc (CD), DVD, FireWire, Thunderbolt, PCI Express, and the like. In other embodiments, one or more of these additional ports are accessed through the door <NUM>.

<FIG> illustrates an electrical component schematic 300A of a pump assembly, such as the pump assembly <NUM>, according to some embodiments. Electrical components can operate to accept user input, provide output to the user, operate the pump assembly and the TNP system, provide network connectivity, and so on. Electrical components can be mounted on one or more printed circuit boards (PCBs). As is illustrated, the pump assembly can include multiple processors.

The pump assembly can comprise a user interface processor or controller <NUM> configured to operate one or more components for accepting user input and providing output to the user, such as the display <NUM>, buttons <NUM>, etc. Input to the pump assembly and output from the pump assembly can controlled by an input/output (I/O) module <NUM>. For example, the I/O module can receive data from one or more ports, such as serial, parallel, hybrid ports, and the like. The processor <NUM> also receives data from and provides data to one or more expansion modules <NUM>, such as one or more USB ports, SD ports, Compact Disc (CD) drives, DVD drives, FireWire ports, Thunderbolt ports, PCI Express ports, and the like. The processor <NUM>, along with other controllers or processors, stores data in one or more memory modules <NUM>, which can be internal or external to the processor <NUM>. Any suitable type of memory can be used, including volatile or non-volatile memory, such as RAM, ROM, magnetic memory, solid-state memory, magnetoresistive random-access memory (MRAM), and the like.

In some embodiments, the processor <NUM> can be a general purpose controller, such as a low-power processor. In other embodiments, the processor <NUM> can be an application specific processor. The processor <NUM> can be configured as a "central" processor in the electronic architecture of the pump assembly, and the processor <NUM> can coordinate the activity of other processors, such as a reduced pressure control processor <NUM>, communications processor <NUM>, and one or more additional processors <NUM> (e.g., processor for controlling the display <NUM>, processor for controlling the buttons <NUM>, etc.). The processor <NUM> can run a suitable operating system, such as a Linux, Windows CE, VxWorks, etc..

The reduced pressure control processor <NUM> can be configured to control the operation of a reduced pressure source, such as a pump <NUM>, and a valve <NUM>. The pump <NUM> can be a suitable pump, such as a diaphragm pump, peristaltic pump, rotary pump, rotary vane pump, scroll pump, screw pump, liquid ring pump, diaphragm pump operated by a piezoelectric transducer, voice coil pump, and the like. The valve <NUM> can be a suitable valve, such as a solenoid valve, diaphragm valve, and the like, and be positioned, for instance, downstream (or before) an exhaust for the pump assembly or in a fluid flow path between the pump assembly and a wound dressing. The valve <NUM> can be a single valve or composed of multiple different valves.

The reduced pressure control processor <NUM> can measure pressure in a fluid flow path, using data received from one or more pressure sensors, calculate the rate of fluid flow, and control the pump <NUM> and the valve <NUM>. The reduced pressure control processor <NUM> can control a pump motor of the pump <NUM> so that a desired level of negative pressure is achieved in the wound cavity <NUM>. The desired level of negative pressure can be pressure set or selected by the user. In various embodiments, the reduced pressure control processor <NUM> controls the pump (e.g., pump motor) using pulse-width modulation (PWM). A control signal for driving the pump <NUM> can be a <NUM>-<NUM>% duty cycle PWM signal. Moreover, the reduced pressure control processor <NUM> can control opening and closing of the valve <NUM> so that a desired level of negative pressure is achieved in the wound cavity <NUM>. The desired level of negative pressure can be pressure set or selected by the user or set automatically according to a mode of operation or setting for the pump assembly. In various embodiments, the reduced pressure control processor <NUM> controls the opening and closing of the valve <NUM> using PWM. A control signal for controlling or driving the valve <NUM> can be a <NUM>-<NUM>% duty cycle PWM signal.

The reduced pressure control processor <NUM> can perform flow rate calculations and detect various conditions in a flow path. The reduced pressure control processor <NUM> can communicate information to the processor <NUM>. The reduced pressure control processor <NUM> can include internal memory or can utilize memory <NUM>. The reduced pressure control processor <NUM> can be a low-power processor.

A communications processor <NUM> can be configured to provide wired or wireless connectivity. The communications processor <NUM> can utilize one or more antennas <NUM> for sending and receiving data. The communications processor <NUM> can provide one or more of the following types of connections: Global Positioning System (GPS) technology, cellular connectivity (e.g., <NUM>, <NUM>, LTE, <NUM>), WiFi connectivity, Internet connectivity, and the like. Connectivity can be used for various activities, such as pump assembly location tracking, asset tracking, compliance monitoring, remote selection, uploading of logs, alarms, and other operational data, and adjustment of therapy settings, upgrading of software or firmware, and the like. The communications processor <NUM> can provide dual GPS/cellular functionality. Cellular functionality can, for example, be <NUM> functionality. The pump assembly can include a SIM card, and SIM-based positional information can be obtained.

The communications processor <NUM> can communicate information to the processor <NUM>. The communications processor <NUM> can include internal memory or can utilize memory <NUM>. The communications processor <NUM> can be a low-power processor.

In some embodiments, using the connectivity provided by the communications processor <NUM>, the device can upload any of the data stored, maintained, or tracked by the pump assembly. The device can also download various operational data, such as therapy selection and parameters, firmware and software patches and upgrades, and the like.

<FIG> illustrates a block diagram of certain components 300B of a pump assembly, such as the pump assembly <NUM>, according to some embodiments. The components 300B include an inlet <NUM> (which can be like the inlet <NUM>), the pump <NUM>, the valve <NUM>, an exhaust <NUM>, a pressure sensor <NUM>, and the reduced pressure control processor <NUM>.

The pump <NUM> can provide negative pressure in a fluid flow path connecting the pump <NUM> (via the inlet <NUM>) to a wound dressing placed over the wound, such that the negative pressure is provided to the inlet <NUM> and then to a wound dressing (for example, through a canister). The valve <NUM> can open (for example, partially or fully) to admit air, gas, or other fluid, which thereby provides positive pressure in the fluid flow path. In some implementations, the pump <NUM> under control of the reduced pressure control processor <NUM> can additionally or alternatively provide positive pressure in the fluid flow path, such as by operating the pump <NUM> in reverse. Additionally or alternatively, another pump different from the pump <NUM> and controllable by the reduced pressure control processor <NUM> can be included to provide positive pressure in the fluid flow path.

In some embodiments, the reduced pressure control processor <NUM> can measure the pressure in the fluid flow path near or at the inlet <NUM> (or at any other location in the fluid flow path, such as at the wound), using data received from one or more pressure sensors, such as the pressure sensor <NUM>, calculate the rate of fluid flow, and control the pump <NUM> and the valve <NUM>. The reduced pressure control processor <NUM> can, for instance, control one or more pump actuators, such as a pump motor of the pump <NUM>, or one or more valve actuators, such as a solenoid of the valve <NUM>, so that a desired level of negative (or positive) pressure is achieved at the wound. The desired level of negative pressure (or pressure setpoint) can be a pressure set or selected by the user or set automatically according to a mode of operation or setting for the pump assembly.

The components 300B can further include one or more additional sensors (not shown), such as a tachometer, positioned to detect or determine a level of activity of the pump <NUM> (for example, the pump motor) and provide indications responsive to the level of activity of the pump <NUM> to the reduced pressure control processor <NUM>. For example, a tachometer can be separate from the pump <NUM> (for example, external to the pump) and positioned near or coupled to the pump <NUM>, and the tachometer can detect a rotation (such as a partial rotation, complete rotation, or multiple partial or complete rotations) of a pump motor of the pump <NUM>.

In some implementations, at least two pressure sensors can be positioned in or fluidically connected to the fluid flow path to permit differential measurement of the pressure. For example, a first pressure sensor can be positioned downstream of the wound dressing (such as at or near an inlet of the pump assembly) and a second pressure sensor can be positioned to detect pressure at or near the wound dressing or at or near a canister. This configuration can be accomplished by incorporating, in addition to one or more lumens forming a first fluid flow path connecting the pump assembly to the wound, a second fluid flow path that includes one or more lumens connecting the pump assembly to the wound dressing and through which the second pressure sensor can monitor pressure at or near the wound dressing or at or near the canister. The first and second fluid flow paths can be fluidically isolated from each other. When the at least two pressure sensors are used, the rate of change of pressure (for example, in peak-to-peak pressure or maximum pressure) in the first and second fluid flow paths can be determined and the difference in pressure detected between the first and second pressure sensors can be determined. These values can be used separately or together to detect various operational conditions, such as leaks, blockages, canister full, presence of blood in the first fluid flow path or the second fluid flow path, etc. Moreover, multiple redundant pressure sensors can be provided to protect against failure of one or more of the pressure sensors in some implementations.

In some embodiments, the pump assembly <NUM> can be operated using a touchscreen interface displayed on the screen <NUM>. Various graphical user interface (GUI) screens present information on systems settings and operations, among other things. The touchscreen interface can be actuated or operated by a finger (or a stylus or another suitable device). Tapping a touchscreen cam result in making a selection. To scroll, a user can touch screen and hold and drag to view the selections. Additional or alternative ways to operate the touchscreen interface can be implemented, such as multiple finger swipes for scrolling, multiple finger pinch for zooming, and the like.

<FIG> and <FIG> illustrate graphical user interface screens according to some embodiments. The GUI screens can be displayed on the screen <NUM>, which can be configured as a touchscreen interface. Information displayed on the screens can be generated based on input received from the user. The GUI screens can be utilized for initializing the device, selecting and adjusting therapy settings, monitoring device operation, uploading data to the network (e.g., cloud), and the like. The illustrated GUI screens can be generated directly by an operating system running on the processor <NUM> or by a graphical user interface layer or component running on the operating system. For instance, the screens can be developed using Qt framework available from Digia.

<FIG> illustrates a therapy settings screen 400A according to some embodiments. The therapy settings screen 400A can be displayed after the pump assembly has been initialized (e.g., screen 400A can function as a home screen). The therapy settings screen 400A includes a status bar <NUM> that comprises icons indicating operational parameters of the device. Animated icon <NUM> is a therapy delivery indicator. When therapy is not being delivered, icon <NUM> can be static and displayed in a color, such as gray. When therapy is being delivered, icon <NUM> can turn a different color, such as orange, and becomes animated, such as, rotates, pulsates, become filled with color, etc. Other status bar icons include a volume indicator and a battery indicator, and may include additional icons, such as wireless connectivity. The therapy settings screen 400A includes date/time and information. The therapy settings screen 400A includes a menu <NUM> that comprises menu items <NUM> for accessing device settings, <NUM> for accessing logs, <NUM> for accessing help, and <NUM> for returning to the therapy settings screen (or home screen) from other screens. The pump assembly can be configured so that after a period of inactivity, such as not receiving input from the user, therapy settings screen 400A (or home screen) is displayed. Additional or alternative controls, indicators, messages, icons, and the like can be used.

The therapy settings screen 400A includes negative pressure up and down controls <NUM> and <NUM>. Up and down controls <NUM> and <NUM> can be configured to adjust the negative pressure setpoint by a suitable step size, such as ±<NUM> mmHg. As is indicated by label <NUM>, the current therapy selection is -<NUM> mmHg (or <NUM> mmHg below atmospheric pressure). The therapy settings screen 400A includes continuous/intermittent therapy selection <NUM>. Continuous therapy selection screen can be accessed via control <NUM> and intermittent therapy selection screen can be accessed via control <NUM>. As is illustrated, the current therapy setting is to continuously deliver negative pressure at -<NUM> mmHg. As is indicated by message <NUM>, therapy delivery can be initiated by pressing a button, such as button 212b on the pump assembly <NUM>. The therapy settings screen 400A includes Y-connector selection <NUM> for treating multiple wounds, such as two, three, etc. wounds, with one pump assembly <NUM>. Control <NUM> selects treatment of a single wound, and control <NUM> selects treatment of more than one wound by the pump assembly. As is indicated by the label "Y-CONNECT OFF," the current selection is to treat a single wound. Additional or alternative controls, indicators, messages, icons, and the like can be used.

<FIG> illustrates therapy settings screen 400B for delivering intermittent therapy according to some embodiments. Screen 400B can be accessed via control <NUM>. Therapy settings screen 400B includes intermittent therapy settings <NUM> and <NUM>. As is illustrated by settings of controls <NUM>, <NUM>, <NUM>, and <NUM>, respectively, current therapy selection is applying -<NUM> mmHg of reduced pressure for <NUM> minutes followed by <NUM> minutes of applying atmospheric pressure (or turning off the vacuum pump). Such treatment cycles can be repeated until stopped by the user or by the pump assembly <NUM>. Negative pressure levels and time durations can be adjusted by selecting one or more of controls <NUM>, <NUM>, <NUM>, and <NUM> and operating the up or down controls <NUM> or <NUM> until desired values are selected. In some implementations, more than two negative pressure values and corresponding durations can be selected for treatment of a wound. For example, a user can select three or more negative pressure values and corresponding durations. Additional or alternative controls, indicators, messages, icons, and the like can be used.

In some embodiments, the pump assembly controls the vacuum pump to deliver negative pressure therapy to a wound according to a selected or programmed protocol. Pump control can be performed by the reduced pressure control processor <NUM> alone or in combination with the processor <NUM>.

For example, the user can select continuous operation at a desired pressure (or negative pressure setpoint). The pump assembly can activate the vacuum pump to reduce or draw down the pressure at the wound (e.g., under the dressing) to reach the setpoint. As explained below, the drawdown can be performed by increasing the negative pressure at the wound limited by a maximum change in negative pressure per unit time called compression, until the setpoint (or another selected pressure value as explained below) has been achieved. Wound drawdown can be defined as the period of time immediately after therapy has been initiated during which the wound has not yet achieved the setpoint. As explained below, at the end of this period when the setpoint is achieved, the flow rate in the fluid flow path should be below a leak (or high flow) threshold and above a low vacuum threshold, otherwise an appropriate alarm will be activated.

As another example, the user can select intermittent operation between two desired pressures (or high and low pressure setpoints). The pump assembly can activate the vacuum pump to reduce or draw down the pressure at the wound to reach the high setpoint. Subsequently, the pump assembly can allow pressure at the wound to increase to reach the low setpoint. As explained below, decreasing and increasing negative pressure can be performed in accordance with the compression setting.

As yet another example, compression can be used anytime there is a change in the pressure setpoint (which can include stopping delivery of negative prsssure). In some embodiments, different compression settings can be used for setpoint changes that result in decreasing or increasing pressure at the wound. In various embodiments, compression setting can be adjusted while a pressure setpoint is being achieved.

<FIG> illustrates a process <NUM> for providing negative pressure wound therapy according to some embodiments. The process <NUM> can be executed by the reduced pressure control processor <NUM> alone or in combination with the processor <NUM> and utilize one or more other components described herein or other systems not shown. The process <NUM> can be periodically executed, such as for example every <NUM> milliseconds (or <NUM> times per second) or at any other suitable frequency. Alternatively or additionally, the process <NUM> can be continuously executed.

The process <NUM> can begin in block <NUM>, which it can transition to when therapy is initiated or when the setpoint is changed while therapy is being delivered. In block <NUM>, the process <NUM> compares wound pressure, which can be determined as explained below, to the setpoint. For example, the process <NUM> can subtract the wound pressure from the setpoint or vice versa. If the wound pressure is below the setpoint, the process <NUM> can transition to block <NUM>. Conversely, if the wound pressure exceeds or is equal to the setpoint, the process <NUM> can transition to block <NUM>.

In block <NUM> (pressure ramp up), the process <NUM> can increment a pump ramp setpoint by an amount that depends on the compression setting as explained below. The vacuum pump will then attempt to draw down (or make more negative) the wound pressure to reach the current value of the pump ramp setpoint. For example, a suitable pump drive signal, such as voltage or current signal, can be generated and supplied to the pump motor so as to increase the speed of the pump motor to achieve wound draw down. For purposes of efficiency, the pump motor can be driven using PWM or any other suitable method. The process <NUM> can continue incrementing the pump ramp setpoint until it reaches the setpoint selected by the user. The process <NUM> can transition to block <NUM> when the wound pressure has nearly reached or reached the setpoint, which can correspond to reaching steady state pressure under the wound dressing. For example, the process <NUM> can transition to block <NUM> when the wound pressure is within a ramp up threshold pressure of the setpoint, such as within <NUM> mmHg of the setpoint or within any other suitable value. In some embodiments, the pump ramp setpiont can be adaptively set to a higher negative pressure than the setpoint. For example, as is explained below, the device can detect presence of one or more leaks which result in a higher level of flow. Because this can cause loss of pressure at the wound, the device can compensate such loss of pressure by increasing the pump ramp setpoint above the setpoint. For instance, the device can set the pump ramp setpoint to be <NUM>%, <NUM>%, <NUM>%, etc. more negative than the setpoint. In certain embodiments, the pump ramp setpoint can be adaptively set to a lower negative pressure (or more positive pressure) than the setpoint.

In block <NUM> (pressure ramp down), the process <NUM> can set the pump ramp setpoint to the setpoint selected by the user (or to another set value as explained above). The process <NUM> can deactivate the pump so that the wound pressure is allowed to decay, such as due to one or more leaks in the fluid flow path, to reach or almost reach the setpoint. This can be performed in accordance with the compression setting, such as for example, deactivating the pump for a first period of time and then activating the pump for a second period of time so that pressure at the wound increases according to the compression setting.

Additionally or alternatively, the process <NUM> can open and close one or more valves (for example, the valve <NUM>) positioned in the fluid flow path, such as described with respect to <FIG> and <NUM>, to thereby admit ambient air, gas,or another fluid into the fluid flow path in order to reach or almost reach the setpoint. This can be performed in accordance with the compression setting, such as for example opening the one or more valves for a first period of time and then closing some or all of the one or more valves for a second period of time so that pressure at the wound increases according to the compression setting. Further, the process <NUM> can operate a positive pressure pump to increase the pressure at the wound. Also, the process <NUM> can utilize a reservoir configured to store air or gas to increase the pressure at the wound. This is described in more detail in <CIT>. Such approaches can advantageously, in certain embodiments, enable negative pressure to be quickly reduced or relieved if appropriate, such as for patient safety in the case of bleeding, excessive pain, and the like.

At this point, the process <NUM> can transition to block <NUM>. For example, the process <NUM> can transition to block <NUM> when the wound pressure is within a ramp down threshold pressure of the setpoint, such as within <NUM> mmHg of the setpoint or within any other suitable value. In some cases, the ramp down threshold pressure can be the same as the ramp up threshold pressure. In some embodiments, the pump ramp setpiont can be adaptively set to a lower negative pressure than the setpoint. For example, as is explained below, the device can detect presence of one or more leaks which result in a higher level of flow. Because this can cause loss of pressure at the wound, the device can compensate such loss of pressure by decreasing the pump ramp setpoint below the setpoint. For instance, the device can set the pump ramp setpoint to be <NUM>%, <NUM>%, <NUM>%, etc. less negative than the setpoint. In certain embodiments, the pump ramp setpoint can be adaptively set to a higher negative pressure (or more positive pressure) than the setpoint.

In block <NUM> (steady state), the pump ramp setpoint can be set to the setpoint selected by the user (or another suitable value). The process <NUM> can control the vacuum pump to maintain the desired negative pressure at the wound. One or more conditions, such as high vacuum, low vacuum, leak, and the like can be detected in block <NUM> as is explained below. If the user changes the setpoint to be more negative or more positive or if delivery of therapy is paused, the process <NUM> can transition to block <NUM>.

In some embodiments, the pump assembly controls the vacuum pump to draw down the wound (e.g., as is explained above in connection with block <NUM>) by utilizing compression. Using compression can be beneficial for avoiding rapid changes in wound pressure, which can minimize patient pain or discomfort, reduce noise produced as a result of operating the pump, maintain efficient delivery of negative pressure, maintain efficient use of power (e.g., battery power), and the like. Compression can be executed by the process <NUM>, which in turn can be implemented by the reduced pressure control processor <NUM> alone or in combination with the processor <NUM>. Compression can correspond to the maximum desired increase or decrease in negative pressure at the wound per unit of time. Compression can be determined based on the negative pressure setpoint in the continuous mode or low and high negative pressure setpoints in the intermittent mode and selected compression setting (e.g., low, medium, or high).

Compression can be utilized when the wound is expected to experience a significant increase in negative pressure. This can occur when: (<NUM>) therapy is initiated on a deflated wound, and negative pressure will increase from zero or substantially zero to reach the pressure setpoint at the wound; (<NUM>) therapy is active in intermittent mode and during transitions from a low negative pressure setpoint to a high negative pressure setpoint, negative pressure will increase to reach the high pressure setpoint at the wound; (<NUM>) therapy is active in intermittent mode and during transitions from a high negative pressure setpoint to a low negative pressure setpoint, negative pressure will decrease to reach the low pressure setpoint at the wound; (<NUM>) therapy is active and the setpoint has been changed to a more negative pressure value, which will cause negative pressure to be increased to reach the higher pressure setpoint at the wound; (<NUM>) therapy is active and the setpoint has been changed to a more positive pressure value, which will cause negative pressure to be decreased to reach the lower pressure setpoint at the wound; (<NUM>) therapy is active and is stopped or paused for a period of time, which will cause the pressure to be gradually restored to atmospheric pressure; or (<NUM>) positive pressure is applied to the wound. Additional situations in which compression may be utilized include, for example, when a leak is introduced after seal has been achieved, which can cause negative pressure at the wound to rapidly drop and the vacuum pump to increase or ramp up delivery of negative pressure in an attempt to maintain pressure. Once the leak has been corrected, the pump would attempt to rapidly restore setpoint pressure at the wound according to the compression setting.

Compression can be achieved by maintaining a secondary negative pressure setpoint target that represents the negative pressure setpoint allowed by compression as a function of time. The secondary setpoint can correspond to the pump ramp setpoint. Secondary setpoint can be incremented or decremented based on the selected compression setting. Secondary setpoint can be incremented or decremented by a suitable amount every time process <NUM> is executed, such as <NUM> times a second or any other suitable frequency. For example, if low compression setting has been selected, the secondary setpoint can be incremented by -<NUM> mmHg (or decremented by <NUM> mmHg), which can result in negative pressure ramp up (or ramp down) of no more than approximately -<NUM> mmHg (or <NUM> mmHg) per second (assuming that pump rate is incremented <NUM> times a second, such as a result of executing the process <NUM>). If medium compression setting has been selected, the secondary setpoint can be incremented by -<NUM> mmHg (or decremented by <NUM> mmHg), which can result in negative pressure ramp up (or ramp down) of no more than approximately -<NUM> mmHg (or <NUM> mmHg) per second. If high compression setting has been selected, the secondary setpoint can be incremented by -<NUM> mmHg (or decremented by <NUM> mmHg), which can result is negative pressure ramp up (or ramp down) of no more than approximately -<NUM> mmHg (or <NUM> mmHg) per second. These values are illustrative and any other suitable values can be used.

In some embodiments, the pump assembly monitors various parameters, such as pressure and rate of flow in the fluid flow path, in order to control the pump in connection with delivery of negative pressure wound therapy. Parameters monitoring and pump control can be performed by the reduced pressure control processor <NUM> alone or in combination with the processor <NUM>. Monitoring the flow rate can be used, among other things, to ensure that therapy is properly delivered to the wound, to detect leakages, blockages, high pressure, and low vacuum, canister full, and the like.

The pump assembly can be configured to indirectly measure the flow rate in the fluid flow path. For example, the pump assembly can measure the speed (e.g., as frequency) of the vacuum pump motor by using a tachometer. Alternatively or additionally, the pump assembly can measure a level of activity or duty cycle of the pump using any suitable approach, such as by monitoring voltage or current supplied to the pump, sensing pump speed (e.g., by using a Hall sensor), measuring back EMF generated by the pump motor, and the like. Tachometer readings can be averaged in order to mitigate the effects of one or more errant readings. A number of most recent tachometer readings, such as over last <NUM> seconds or any other suitable time period, can be averaged to obtain short tachometer average. A number of less recent tachometer readings, such as over the last <NUM> seconds or any other suitable time period, can be averaged to obtain long tachometer average. Short and long tachometer averages can be utilized for pump control. Additionally or alternatively, the pump assembly can directly measure the flow rate, such as by using a flow meter.

Flow rate can be estimated as the air or gas volume moving over the wound per unit of time normalized to standard temperature and standard pressure (e.g., <NUM> atm). Flow rate can be periodically computed, such as every <NUM> milliseconds or any other suitable time value, according to the following formula:
<MAT>.

Tachometer is short tachometer average (e.g., in Hz) and Slope and Intercept are constants that are based on the pressure setpoint. The values for Slope and Intercept can be determined for possible pressure setpoints (e.g., -<NUM> mmHg, -<NUM> mmHg, -<NUM> mmHg, -<NUM> mmHg, -<NUM> mmHg, -<NUM> mmHg, -<NUM> mmHg, -<NUM> mmHg, -<NUM> mmHg, -<NUM> mmHg, -<NUM> mmHg, -<NUM> mmHg, -<NUM> mmHg) for a given vacuum pump type. The flow as a function of the pump speed may not be a best fit as a single line because the vacuum pump can be designed to be more efficient at lower flow rates. Because of this, slope and intercept values can be pre-computed for various setpoints and various pumps. Flow rate can be measured in standard liters per minute (SLPM) or any other suitable measurement unit. As explained below, the determined flow rate can be compared to various flow rate thresholds, such as blockage threshold, leakage threshold, and maximum flow rate threshold, to determine a presence of a particular condition, such as a blockage, leakage, over vacuum, etc..

In addition, the pump assembly can determine and monitor pressure in the flow path using one or more sensors. In some embodiments, the pump assembly includes a pressure sensor in or near the inlet <NUM> (or canister connection) of the pump assembly <NUM> or in any other suitable locations in the fluid flow path, such as described herein. This pressure sensor can measure the pressure in the canister (or in or near the dressing in a canisterless system). The arrangement of one or more pressure sensors in disclosed in <CIT>. The pump assembly can continuously measure pressure in the canister, such as every millisecond or any other suitable duration. A suitable number of latest pressure sensor readings can be averaged to mitigate the effects of one or more errant readings.

Wound pressure can be estimated using the measured canister pressure and the pump speed. Because of presence of one or more leaks in the flow path, wound pressure may not be the same as canister pressure. For example, wound pressure may be lower or more positive than canister pressure. In some embodiments, wound pressure is estimated using the following formula:
<MAT>.

Canister Pressure is averaged measured canister pressure. As explained above, Tachometer is short tachometer average and Slope and Intercept are constants that are based on the pressure setpoint. The values for Slope and Intercept are not necessarily same value as used above for determining the flow rate. Additionally or alternatively, wound pressure can be measured directly by a pressure sensor placed in the wound or near the wound or under the dressing.

Based on the determined flow rate, canister pressure, and wound pressure values, the pump assembly can monitor and detect various operating conditions. One or more of these conditions can be detected by the process <NUM> while the process in in block <NUM>. Blockage in the fluid flow path can be determined by comparing the flow rate, as reflected by long tachometer average, to a particular blockage threshold over or during a period of time, such as <NUM> minutes or any other suitable duration. The blockage threshold can be selected or determined based on the particular pressure setpoint. That is, to detect blockage, the pump assembly can utilize a plurality of blockage thresholds corresponding to particular pressure setpoints. As explained above, the flow rate can be indirectly determined by detecting and monitoring the pump speed. Long tachometer average can be compared to the blockage threshold. Alternatively or additionally, short tachometer average or any other suitable measure of flow rate can be compared to the blockage threshold.

In some embodiments, blockage detection may be suspended while the process <NUM> is in block <NUM>. That is, blockage detection can be configured to be suppressed or disabled when the therapy unit is in the ramp down state in block <NUM>. Blockage detection can be enabled or re-enabled when the process transitions to another state, such as the steady state in block <NUM>. In some embodiments, blockage detection can be disabled when the process <NUM> is in a state other than the ramp down state in block <NUM>, such as when the process <NUM> is in the ramp up state in block <NUM>, and re-enabled when the process <NUM> is in a state other than the steady state in block <NUM>. In some embodiments, the process <NUM> can continuously monitor for a blockage condition, but when such conditions is detected, the process <NUM> can be configured to suppress the blockage alarm when in, for example, a pressure ramp down state.

When the pump is off, such as when intermittent therapy is applied with one of the pressure setpoints being set to zero, and negative pressure at the wound is expected to decrease (or become more positive) due to leaks, blockage can be detected by determining whether the pressure level at the wound is decreasing or decaying as expected. For example, the drop in pressure at the wound can be computed over a period of time, such as <NUM> seconds or any other suitable duration. A blockage may be present if the wound pressure at the end of the period of time has not decreased to satisfy (e.g., exceed) a pressure decay threshold.

In additional or alternative embodiments, multiple pressure sensors can be placed in the fluid flow path to facilitate detection of one or more of the above-described conditions. For example, in addition to or instead of the pressure sensor being placed in the pump inlet, a pressure sensor can be placed in the wound or under the dressing to directly determine the wound pressure. Measuring pressure at different locations in the fluid flow path, such as in the canister and at the wound, can facilitate detection of blockages, leaks, canister full condition, and the like. Multiple lumens can be utilized for connecting fluid flow path elements, such as pressure sensors, canister, pump assembly, dressing, and the like. Canister full condition can be detected by placing a sensor, such as capacitive sensor, in the canister. In some embodiments, in order to prevent occurrence of over vacuum, the maximum pressure supplied by the pump can be limited mechanically or electrically. For example, a pump drive signal, such as voltage or current supplied to the pump, can be limited not exceed a maximum flow rate threshold, such as <NUM> liters/min or any other suitable value. Additional details of flow rate detection and pump control are provided in <CIT>.

In some embodiments, one or more flow sensors or flow meters can be used to directly measure the fluid flow. In some embodiments, the pump assembly can utilize one or more of the above-described techniques in parallel to control the pump and to detect various conditions. The pump assembly can be configured to suitably arbitrate between using parameters determined by different techniques. For example, the pump assembly can arbitrate between flow rates determined indirectly, such as based on the pump speed as measured by a tachometer, and directly, such as by using a flow meter. In certain embodiments, the pump assembly can indirectly determine the flow rate and resort to direct determination of the flow rate when needed, such as when indirectly determined flow rate is perceived to be inaccurate or unreliable.

<FIG> illustrates a process <NUM> of controlling wound therapy according to some embodiments. The process <NUM> can be executed by the reduced pressure control processor <NUM> alone or in combination with the processor <NUM> and utilize one or more other components described herein or other systems not shown. The process <NUM> can be periodically executed or at any other suitable frequency or continuously. Advantageously, in certain embodiments, the process <NUM> can enable dynamic control of the supply of positive pressure by a valve or a pressure source to a wound dressing. Such control can desirably allow for enhanced intermittent or dynamic therapies and control of therapy in a manner that reduces an amount of pain felt by a patient during negative pressure wound therapy.

At block <NUM>, the process <NUM> can measure pressure in a fluid flow path. For example, the pressure may have been measured using the pressure sensor <NUM> at or near the inlet <NUM> or at any other suitable portion of the fluid flow path.

At block <NUM>, the process <NUM> can generate a control signal from the measured pressure. For example, the control signal can be a PWM signal, and a duty cycle of the control signal can be varied according to the measured pressure. In some embodiments, the duty cycle of the control signal can be varied according to a proportional-integral-derivative (PID) calculation that depends on a difference between the measured pressure and a pressure setpoint, such as is described with respect to the process <NUM> of <FIG>.

At block <NUM>, the process <NUM> outputs the control signal to control positive pressure. The control signal is output to the valve <NUM> to operate the valve <NUM> to vary an amount of positive pressure provided to the fluid flow path.

<FIG> illustrates a process <NUM> for determining a duty cycle for a PWM control signal for a positive pressure source, such as the valve <NUM>, according to some embodiments. The process <NUM> can be executed by the reduced pressure control processor <NUM> alone or in combination with the processor <NUM> and utilize one or more other components described herein or other systems not shown. The process <NUM> can be executed in intermittent pressure mode when positive pressure is provided to the wound (for example, in block <NUM> of <FIG>). The process <NUM> can be periodically executed or at any other suitable frequency or can be performed when positive pressure is introduced under control of a pump assembly. Advantageously, in certain embodiments, the process <NUM> can enable the reduced pressure control processor <NUM> to determine a suitable duty cycle for controlling a source of positive pressure, such as a valve like the valve <NUM> or a pump like the pump <NUM> operating in reverse or a dedicated positive pressure pump to provide positive pressure, so that an amount of positive pressure provided is ramped, provided according to a compression setting, or controlled to a setpoint.

The process <NUM> can be based on a PID calculation and serve as a control loop feedback mechanism. The control loop feedback mechanism can provide up to three-term control according to an error value calculated based on a difference between a measured pressure and a setpoint pressure. The up to three-term control can be determined by a proportional control term (PTERM), integral control term (ITERM), or derivative control term (DTERM). In some embodiments, the output of the PID calculation (PIDOUT) can depend on a sum of PTERM, ITERM, and DTERM. The ITERM, in addition, can be related to an integral sum (ISUM) that can also depend on an accumulation of past errors. As illustrated by the process <NUM>, in some embodiments, DTERM can be set to <NUM> during the process <NUM>.

PIDOUT can be set to permissibly range from <NUM> to <NUM> so that <NUM> corresponds to a <NUM>% duty cycle PWM control signal (for example, causing positive pressure to be supplied at a minimum level such as providing no positive pressure), <NUM> corresponds to a <NUM>% duty cycle PWM control signal (for example, causing positive pressure to be supplied at a level <NUM>% of a maximum level), <NUM> corresponds to a <NUM>% duty cycle PWM control signal (for example, causing positive pressure to be supplied at a level <NUM>% of a maximum level), <NUM> corresponds to a <NUM>% duty cycle PWM control signal (for example, causing positive pressure to be supplied at a level <NUM>% of a maximum level), and <NUM> corresponds to a <NUM>% duty cycle PWM control signal (for example, causing positive pressure to be supplied at a maximum level). In one implementation, for instance, <NUM> may correspond to a <NUM>% duty cycle PWM control signal and cause a valve like the valve <NUM> to remain fully open <NUM>% of the time and fully closed <NUM>% of the time, <NUM> may correspond to a <NUM>% duty cycle PWM control signal and cause a valve like the valve <NUM> to remain fully open <NUM>% of the time and fully closed <NUM>% of the time, and <NUM> may correspond to a <NUM>% duty cycle PWM control signal and cause a valve like the valve <NUM> to remain fully open <NUM>% of the time and fully closed <NUM>% of the time.

At block <NUM>, the process <NUM> can determine whether a measured pressure (PMEASURED) in the flow path is below a low vacuum threshold (TLOW). The measured pressure can be a pressure measured by a pressure sensor positioned at or near an inlet of a pump assembly, such as the pump assembly <NUM>, or in any other suitable place or places in the fluid flow path. If the measured pressure exceeds the low vacuum threshold, at block <NUM>, the process <NUM> can set ISUM to be <NUM> and PIDOUT to be <NUM>, and the process <NUM> can end by returning the value of PIDOUT.

If the measured pressure does not exceed the low vacuum threshold, the process <NUM> can transition to block <NUM>, where the process <NUM> can set ERROR to be a difference between the measured pressure and a pressure setpoint and set PTERM to be a proportional gain (Kp) times ERROR. The pressure setpoint can be set, for example, by a user of a pump assembly by setting a desired pressure or a mode of operation that corresponds to the pressure setpoint. In some embodiments, the proportional gain can be set at pump assembly manufacture or during a test operation of a pump assembly using one or more control loop tuning approaches. The proportional gain can, for instance, be set to a value ranging from <NUM> to <NUM>, ranging from <NUM> to <NUM>, ranging from <NUM> to <NUM>, or to <NUM>.

The process can transition to block <NUM>, where the process <NUM> can determine whether PTERM equals or exceeds <NUM>. If PTERM equals or exceeds <NUM>, at block <NUM>, the process <NUM> can set ISUM to be <NUM> and PIDOUT to be <NUM>, and the process <NUM> can end by returning the value of PIDOUT. If PTERM does not equal or exceed <NUM>, the process <NUM> can transition to block <NUM>, where the process <NUM> can determine whether ERROR is below <NUM>. If ERROR is not below <NUM>, the process <NUM> can set ISUM to be a sum of ISUM and <NUM> times ERROR at block <NUM>. If ERROR is below <NUM>, the process <NUM> can set ISUM to be a sum of ISUM and ERROR at block <NUM>. The process <NUM> can transition from block <NUM> or <NUM> to block <NUM>, where the process <NUM> can determine whether ISUM is less than <NUM>. If ISUM is less than <NUM>, at block <NUM>, the process <NUM> can set ISUM to be <NUM> and PIDOUT to be PTERM at block <NUM>, and the process <NUM> can end by returning the value of PIDOUT.

If ISUM is not less than <NUM>, the process <NUM> can transition to block <NUM>, where the process <NUM> can set ITERM to be an integral gain (KI) times ISUM and set PIDOUT to be a sum of PTERM and ITERM. In some embodiments, the proportional gain can be set to a value ranging from <NUM> to <NUM>, ranging from <NUM> to <NUM>, or to <NUM>. The process <NUM> can transition to block <NUM>, where the process <NUM> can determine whether PIDOUT exceeds <NUM>. If PIDOUT does not exceed <NUM>, process <NUM> can end by returning the value of PIDOUT. If PIDOUT exceeds <NUM>, the process can transition to block <NUM>, where the process <NUM> can scale ISUM (e.g., by an amount depending on or proportional to the amount that PIDOUT exceeds <NUM>) and set PIDOUT to be <NUM>, and the process <NUM> can end by returning the value of PIDOUT.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of protection. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made. Those skilled in the art will appreciate that in some embodiments, the actual steps taken in the processes illustrated or disclosed may differ from those shown in the figures. For example, the actual steps or order of steps taken in the disclosed processes may differ from those shown in the figure. For instance, the various components illustrated in the figures may be implemented as software or firmware on a processor, controller, ASIC, FPGA, or dedicated hardware. Hardware components, such as processors, ASICs, FPGAs, and the like, can include logic circuitry.

User interface screens illustrated and described herein can include additional or alternative components. These components can include menus, lists, buttons, text boxes, labels, radio buttons, scroll bars, sliders, checkboxes, combo boxes, status bars, dialog boxes, windows, and the like. User interface screens can include additional or alternative information. Components can be arranged, grouped, displayed in any suitable order.

Claim 1:
An apparatus for applying negative pressure therapy to a wound, the apparatus comprising:
a source of negative pressure (<NUM>) configured to be in fluidic communication via a flow path with a wound dressing placed over a wound, the source of negative pressure configured to provide negative pressure under the wound dressing;
a valve (<NUM>) configured to control supply of positive pressure via the flow path to the wound dressing; and
a controller (<NUM>) configured to:
operate the source of negative pressure to supply negative pressure via the flow path to the wound dressing,
determine a pressure difference between a pressure under the wound dressing and a pressure setting,
generate a control signal according at least to the pressure difference, and
using the control signal, operate the valve to supply positive pressure via the flow path to the wound dressing so that the pressure under the wound dressing reaches the pressure setting; and
characterised in that
the controller is configured to operate the valve to supply positive pressure when the controller applies intermittent negative pressure wound therapy to the wound, and to output the control signal to the valve to operate the valve to vary an amount of positive pressure provided to the fluid flow path.