Patent Description:
Wound therapy systems including instillation therapy (IT) systems and negative pressure wound therapy (NPWT) systems rely on conduit or flow tubing to transport and receive fluids from a wound site. During instillation, the IT device delivers instillation fluid to the wound site for treatment and to prevent drying of any affected areas. After instillation is complete, the NPWT device applies a negative pressure to the wound site to resume the therapy regimen. The negative pressure forces the instillation fluid into the conduit, which can result in a large pressure drop across the conduit between a pump and the wound site. This large pressure drop may be overcome by increasing the operating speed of the pump, resulting in a large pressure differential between the pump and the wound site. In some instances, the higher negative pressures applied by the pump can be communicated to the wound site, such as when a bolus of instillation fluid suddenly clears from the conduit. In such instances, the NPWT system may be configured to open a valve to vent the wound site to ambient pressure, which may induce dynamic instability in the system. <CIT> concerns a wound therapy device.

It would be desireable to provide an improved system and method to clear fluids from a conduit following instillation to a wound site during negative pressure wound therapy.

One implementation of the present disclosure is a wound therapy system. The wound therapy system includes a wound dressing apparatus, a pneumatic pump, a valve, and a controller. The pneumatic pump is fluidly coupled to the wound dressing apparatus and is configured to apply a negative pressure to the wound dressing apparatus. The valve is coupled to the wound dressing apparatus at a location that is upstream of the wound. The controller is communicatively coupled to the pneumatic pump and the valve. The controller is configured to determine a volume of instillation fluid that has been delivered to the wound. The controller is also configured to operate the pneumatic pump and the valve to apply the negative pressure to the wound dressing apparatus to purge a first portion of the instillation fluid from the wound dressing apparatus. The controller is further configured to operate the pneumatic pump and the valve during a purge operation to deliver a volume of air through the wound dressing apparatus that is approximately equal to or greater than the volume of instillation fluid to purge a second portion of the instillation fluid from the wound dressing apparatus.

In any of the above embodiments, the wound therapy system may include a removable fluid canister that is fluidly coupled to the wound dressing apparatus and the pneumatic pump. The removable fluid canister may be configured to receive the instillation fluid from the wound dressing apparatus during the purge operation. In some instances, the wound therapy system also includes a sensor that is fluidly coupled to the removable fluid canister and that is configured to determine a negative pressure of the removable fluid canister. The controller may be communicatively coupled to the sensor and configured to initiate the purge operation based on a determination that the negative pressure of the removable fluid canister is above a predefined purge trigger pressure. Additionally, the controller may be configured to operate the pneumatic pump during the purge operation to maintain the negative pressure of the removable fluidly canister to a value that is approximately equal to a predefined target therapy pressure at the wound. Alternatively, the controller may be configured to operate the pneumatic pump during the purge operation to maintain the negative pressure of the removable fluid canister to a value that is greater than a predefined target therapy pressure at the wound by a predefined threshold.

In any of the above embodiments, the controller may be configured to hold the valve open for a period of time within a range between approximately <NUM> and <NUM> seconds during the purge operation.

In some embodiments, the wound dressing apparatus includes a wound dressing and a fluid conduit. The fluid conduit may include at least one sensing lumen and a vacuum lumen. In some aspects, the volume of air is approximately equal to a total volume of the at least one sensing lumen and the vacuum lumen.

In any of the above embodiments, the controller may be configured to repeatedly open and close the valve during the purge operation at a predefined operating frequency. In some embodiments, the valve is a digitally variable, pulse-width-modulation driven valve. The controller may be configured to continuously vary an operating frequency of the valve during the purge operation to provide a gradual increase in flow rate at a beginning of the purge operation and an end of the purge operation.

In any of the above embodiments, the controller may be configured to continuously repeat the purge operation for a predefined number of cycles or for a predefined time period.

In some embodiments, the wound therapy system also includes an instillation fluid canister configured to contain the instillation fluid and an instillation pump configured to deliver the instillation fluid from the instillation fluid canister to the wound dressing apparatus.

In some embodiments, the valve is fluidly coupled to the wound dressing apparatus at a location that is upstream of the wound and the pneumatic pump.

Another implementation of the present disclosure is an apparatus. The apparatus includes a purge control circuit that further includes a memory and a processor. The memory stores machine-readable instructions configured to cause the processor to perform operations. The operations include determining a volume of instillation fluid that has been delivered to a wound through a wound dressing apparatus, operating a pneumatic pump and a valve to apply a negative pressure to the wound dressing apparatus to purge a first portion of the instillation fluid from the wound dressing apparatus, and operating the pneumatic pump and the valve during a purge operation to deliver a volume of air through the wound dressing apparatus that is approximately equal to or greater than the volume of instillation fluid to purge a second portion of the instillation fluid from the wound dressing apparatus.

In some embodiments, the machine readable instructions cause the processor to initiate the purge operation in response to a determination that a negative pressure of a removable fluid canister is above a predefined purge trigger pressure.

Another implementation (not claimed) of the present disclosure is a method of purging a wound dressing apparatus. The method includes providing a volume of instillation fluid to the wound dressing apparatus. The method also includes dwelling, for a first period of time with the instillation fluid contained within the wound dressing apparatus. The method further includes applying, by a pneumatic pump that is fluidly coupled to the wound dressing apparatus and a removable fluid canister, a negative pressure to the wound dressing apparatus to purge a first portion of the instillation fluid from the wound dressing apparatus into the removable fluid canister. The method additionally includes passing, by the pneumatic pump and a valve, a volume of air through the wound dressing apparatus that is approximately equal to or greater than the volume of instillation fluid to purge a second portion of instillation fluid from the wound dressing apparatus into the removable fluid canister.

In some embodiments, the method further includes determining a negative pressure of the removable fluid canister that is fluidly coupled to the wound dressing apparatus and the pneumatic pump, and passing the volume of air through the wound dressing apparatus based on a determination that the negative pressure of the removable fluid canister is above a predefined purge trigger pressure.

In other embodiments, the method of passing the volume of air through the wound dressing apparatus includes determining an open time during which the valve is held in an open position. The method of determining the open time may include identifying a target open time associated with the volume of instillation fluid, and adjusting the open time to equal or substantially equal the target open time.

In some embodiments, the volume of instillation fluid is provided to the wound dressing apparatus by an instillation pump that is fluidly coupled to the wound dressing apparatus.

Those skilled in the art will appreciate that the summary is illustrative only and is not intended to be in any way limiting. Other aspects, inventive features, and advantages of the devices and/or processes described herein, as defined solely by the claims, will become apparent in the detailed description set forth herein and taken in conjunction with the accompanying drawings.

Referring generally to the Figures, a wound therapy system and method is provided for actively removing (e.g., purging) liquids (e.g., instillation fluid, wound exudate, etc.) from a wound during negative pressure wound therapy. Specifically, the wound therapy system is configured to remove liquids from the wound through a wound dressing apparatus that is fluidly coupled to the wound. The wound therapy system includes a pneumatic pump and a valve that are both fluidly coupled to the wound dressing apparatus. According to various exemplary embodiments, the valve is located upstream of both the wound and the pneumatic pump. The wound therapy system additionally includes a controller communicatively coupled to the pneumatic pump and the valve. The controller is configured to coordinate operation of the pneumatic pump and the valve to purge the wound dressing apparatus after delivery of an instillation fluid to the wound.

In various exemplary embodiments, the controller is configured to determine a volume of instillation fluid that has been delivered to the wound. The controller may be configured to operate the pneumatic pump and the valve during a purge operation to deliver a volume of air through the wound dressing apparatus that is greater than or equal to the determined volume of instillation fluid. Among other benefits, purging the wound dressing apparatus based on the volume of instillation fluid introduced (into the wound dressing apparatus) reduces the risk of leaving behind any liquids while also minimizing the amount of time required to complete the purge cycle. In some embodiments, the purge cycle may be performed just after the instillation fluid is introduced to the wound site in order to reduce the risk of drying the wound.

In some embodiments, the wound therapy system includes a sensor configured to determine a negative pressure downstream of the wound. Specifically, the sensor may be configured to determine a negative pressure of a removable fluid canister that is disposed between the wound dressing apparatus and the pneumatic pump (e.g., a removable fluid canister configured to receive instillation fluid from the wound dressing apparatus). The controller may be communicatively coupled to the sensor and may be configured to control the pneumatic pump based on information received from the sensor. For example, the controller may be configured to initiate the purge operation based on a determination that the negative pressure of the removable fluid canister is above a predefined threshold (e.g., a purge trigger pressure that indicates a discrepancy between the pressure at the removable fluid canister and the wound, etc.). During the purge operation, information from the sensor may be used by the control the pneumatic pump to maintain the negative pressure of the removable fluid canister above the predefined threshold (e.g., at a purge operating pressure).

In some embodiments, the valve is cycled between an open state and a closed state multiple times by the controller during the purge. Among other benefits, cycling or fluttering the valve reduces system instability and may also allow for pressure monitoring at the wound site during the purge operation to more accurately determine when the instillation liquid has been removable from the wound dressing apparatus. These and other features and advantages of the wound therapy system are described in detail below.

Referring to <FIG>, a wound therapy system <NUM> is shown, according to an exemplary embodiment. The wound therapy system <NUM> is configured to facilitate treatment (e.g., healing) of a wound <NUM>. The wound therapy system <NUM> is shown to include a therapy device <NUM> fluidly connected to a wound dressing <NUM> via instillation tubing <NUM>, sensing tubing <NUM>, and vacuum tubing <NUM>. As used herein, tubing may refer to conduit and/or fluid lines configured to transport fluids to different parts of the wound therapy system <NUM>. The wound dressing <NUM> may be adhered or sealed to a patient's skin <NUM> surrounding a wound <NUM>. In various exemplary embodiments, the therapy device <NUM> is configured to provide negative pressure wound therapy (NPWT) by reducing the pressure at the wound <NUM>. The therapy device <NUM> can draw a vacuum at the wound <NUM> (relative to atmospheric pressure) by removing wound exudate, air, and other fluids from the wound <NUM>. Wound exudate may include fluid that filters from a patient's circulatory system into lesions or areas of inflammation. For example, wound exudate may include water and dissolved solutes such as blood, plasma proteins, white blood cells, platelets, and red blood cells. Other fluids removed from the wound <NUM> may include instillation fluid <NUM> used to mediate and/or wet the wound <NUM>. Instillation fluid <NUM> can include, for example, a cleansing fluid, a prescribed fluid, a medicated fluid, an antibiotic fluid, or any other type of fluid which can be delivered to the wound <NUM> during wound treatment. As shown in <FIG>, instillation fluid <NUM> may be held in an instillation fluid canister <NUM> and controllably dispensed to the wound <NUM> via instillation tubing <NUM>.

The wound therapy system <NUM> includes a wound dressing apparatus <NUM>. The wound dressing apparatus <NUM> is configured to fluidly couple the therapy device <NUM> to the wound <NUM>. In the exemplary embodiment of <FIG>, the wound dressing apparatus <NUM> includes the wound dressing <NUM>, the sensing tubing <NUM>, and the vacuum tubing <NUM>. Specifically, the wound dressing apparatus <NUM> includes a portion of the sensing tubing <NUM> that extends between a purge valve <NUM> and the wound dressing <NUM>, and a portion of the vacuum tubing <NUM> that extends between a removable fluid canister <NUM> and the wound dressing <NUM>. The sensing tubing <NUM> is configured to fluidly couple the one or more sensors to the wound dressing <NUM> (e.g., wound <NUM>) so that conditions at the wound <NUM> may be accurately monitored. The vacuum tubing <NUM> is configured to fluidly couple the wound dressing <NUM> to an NPWT system that is configured to apply a negative pressure to the wound dressing <NUM> (and wound <NUM>). In various exemplary embodiments, the sensing tubing <NUM> and the vacuum tubing <NUM> are individual lumens (e.g., flow conduits) integrally formed into a single unitary structure (e.g., hose, tube, etc.) that extends between the therapy device <NUM> and the wound dressing <NUM>. In other embodiments, the number and arrangement of the sensing tubing and/or the vacuum tubing may be different.

As shown in <FIG>, fluids <NUM> removed from the wound <NUM> pass through the vacuum tubing <NUM> and are collected in the removable fluid canister <NUM>. The removable fluid canister <NUM> may be a component of the therapy device <NUM> configured to collect wound exudate and other fluids <NUM> (e.g., instillation fluid <NUM>) removed from the wound <NUM>. In some embodiments, the removable fluid canister <NUM> is detachable from the therapy device <NUM> to allow the canister <NUM> to be emptied and replaced as needed. A lower portion of the canister <NUM> may be filled with wound exudate and other fluids <NUM> removed from the wound <NUM>, whereas an upper portion of the canister <NUM> may be filled with air. The therapy device <NUM> can be configured to draw a vacuum within the canister <NUM> by pumping air out of the canister <NUM>. The reduced pressure within the canister <NUM> can be translated to the wound dressing <NUM> and the wound <NUM> via the vacuum tubing <NUM> such that the wound dressing <NUM> and the wound <NUM> are maintained at approximately the same pressure as canister <NUM> (or a different pressure depending on the pressure drop through the vacuum tubing <NUM>).

Therapy device <NUM> is shown to include a pneumatic pump <NUM>, an instillation pump <NUM>, a safety relief valve <NUM>, a purge valve <NUM>, a filter <NUM>, and a controller <NUM>. As shown in <FIG>, the pneumatic pump <NUM> is fluidly coupled to the removable fluid canister <NUM> (e.g., via conduit <NUM>) and is configured to draw a vacuum within canister <NUM> by pumping air out of canister <NUM>. Pneumatic pump <NUM> is controlled by a controller <NUM>, as will be described in greater detail below with reference to <FIG>.

Similarly, instillation pump <NUM> can be fluidly coupled to instillation fluid canister <NUM> via instillation tubing <NUM> and fluidly coupled to wound dressing <NUM> via instillation tubing <NUM>. The instillation pump <NUM> is configured to deliver instillation fluid <NUM> to the wound dressing <NUM> and the wound <NUM> by pumping instillation fluid <NUM> through the instillation tubing <NUM>, as shown in <FIG>. The instillation pump <NUM> may also be controlled by controller <NUM> and/or by a separate, dedicated controller of the therapy device <NUM>.

Filter <NUM> is positioned between the removable fluid canister <NUM> and the pneumatic pump <NUM> (e.g., along conduit <NUM>) such that the air pumped out of the canister <NUM> passes through the filter <NUM>. The filter <NUM> is configured to prevent liquid or solid particles from entering the conduit <NUM> and reaching the pneumatic pump <NUM>. In various exemplary embodiments, the filter <NUM> includes a bacterial filter that is hydrophobic and/or lipophilic such that aqueous and/or oily liquids will bead on the surface of the filter <NUM>.

As shown in <FIG>, the safety relief valve <NUM> can be fluidly connected with the pneumatic pump <NUM> and the filter <NUM> via conduit <NUM>. In some embodiments, the safety relief valve <NUM> is configured to control airflow between the conduit <NUM> and an environment surrounding the therapy device <NUM>. For example, the safety relief valve <NUM> may be opened to allow airflow into the conduit <NUM> via vent <NUM> and conduit <NUM>, and closed to prevent airflow into the conduit <NUM> via vent <NUM> and conduit <NUM>. Among other benefits, the safety relief valve <NUM> may be used to reduce the risk of damage to the NPWT system due to over-pressurization. The safety relief valve <NUM> may also be used to rapidly return the NPWT system to ambient pressure when removing or replacing the dressing <NUM>. The safety relief valve <NUM> is operably coupled to the controller <NUM> and may be opened and closed by controller <NUM>.

The purge valve <NUM> is fluidly coupled to the sensing tubing <NUM>. The purge valve <NUM> is configured to control airflow between the sensing tubing <NUM> and the environment surrounding the therapy device <NUM>. For example, the purge valve <NUM> may be opened to allow airflow into the sensing tubing <NUM> via vent <NUM>. During operation (e.g., when the pneumatic pump <NUM> is activated), air entering the sensing tubing <NUM> through the purge valve <NUM> is directed through the sensing tubing <NUM> and toward the wound dressing <NUM>. At the wound dressing <NUM>, the air is redirected through the vacuum tubing <NUM> as a result of the negative pressure applied to the removable fluid canister <NUM> by the pneumatic pump <NUM>. As the air moves along the sensing tubing <NUM> and vacuum tubing <NUM>, it forces liquids contained within the wound dressing apparatus <NUM>, including wound exudate, instillation fluid <NUM>, and/or other fluids <NUM> out of the wound dressing apparatus <NUM>, and into the removable fluid canister <NUM>, thereby purging the wound dressing apparatus <NUM> of any entrained liquids.

The safety relief valve <NUM> and the purge valve <NUM> may be electronically controlled solenoid valves. The safety relief valve <NUM> may be the same or similar to the purge valve <NUM>. In various exemplary embodiments, the purge valve <NUM> is configured to regulate the flow rate of air through the vent <NUM> to prevent a sudden crash (e.g., reduction) in negative pressure at the wound <NUM> (e.g., an abrupt increase in static pressure at the wound <NUM>) when the purge valve <NUM> is activated (e.g., opened). For example, the purge valve <NUM> may be cycled between an open and closed state at a predefined operating frequency by the controller <NUM> to gradually reduce the negative pressure at the start of a purge cycle. In some embodiments, the purge valve <NUM> is a digitally variable, pulse-width-modulation (PWM) driven valve which functions as a digitally variable orifice that can be tuned to provide a digital and profiled rate of pressure decay at the wound <NUM>. In other embodiments, the purge valve <NUM> may include a plurality of valves arranged in parallel to selectively vary the air flow rate into the sensing tubing <NUM>.

The therapy device <NUM> additionally includes a plurality of sensors configured to monitor operating conditions in different parts of the wound therapy system <NUM>. In the exemplary embodiment of <FIG>, the therapy device <NUM> includes a plurality of pressure sensors. A first pressure sensor <NUM> of the plurality of pressure sensors is coupled to the removable fluid canister <NUM> and is configured to measure a pressure (e.g., static pressure) of the removable fluid canister <NUM>. A second pressure sensor <NUM> of the plurality of pressure sensors is coupled to the sensing tubing <NUM> at a location between the purge valve <NUM> and the wound dressing <NUM>. The second pressure sensor <NUM> is configured to measure a pressure (e.g., static pressure) at the wound <NUM> (e.g., a wound site to which the wound dressing <NUM> is coupled). The plurality of pressure sensors may be communicatively coupled to the controller <NUM> such that pressure measurements collected by the plurality of pressure sensors may be communicated to the controller <NUM>. The controller <NUM> uses the pressure measurements to ensure that the wound <NUM> is maintained at a target negative pressure and/or to determine whether a purge operation is required to remove liquids from the wound dressing apparatus <NUM>, as will be further described below with reference to <FIG>.

Referring now to <FIG>, a block diagram illustrating the controller <NUM> in greater details is shown, according to an exemplary embodiment. In other embodiments, the controller <NUM> may include additional, fewer, and/or different components. The controller <NUM> is shown to include a processing circuit <NUM> including a processor <NUM> and memory <NUM>. The processor <NUM> may be a general purpose or specific purpose processor, an application specific integrated circuit (ASIC), one or more field programmable gate arrays (FPGAs), a group of processing components, or other suitable processing components. The processor <NUM> is configured to execute computer code or instructions stored in memory <NUM> or received from other computer readable media (e.g., CDROM, network storage, a remote server, etc.).

Memory <NUM> may include one or more devices (e.g., memory units, memory devices, storage devices, etc.) for storing data and/or computer code for completing and/or facilitating the various processes described in the present disclosure. Memory <NUM> may include random access memory (RAM), read-only memory (ROM), hard drive storage, temporary storage, non-volatile memory, flash memory, optical memory, or any other suitable memory for storing software objects and/or computer instructions. Memory <NUM> may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in the present disclosure. Memory <NUM> may be communicably connected to the processor <NUM> via processing circuit <NUM> and may include computer code for executing (e.g., by the processor <NUM>) one or more processes described herein. When the processor <NUM> executes instructions stored in memory <NUM>, the processor <NUM> generally configures the controller <NUM> (and more particularly processing circuit <NUM>) to complete such activities.

The controller <NUM> is shown to include a purge control circuit <NUM>. The purge control circuit <NUM> may be configured to determine a volume of instillation fluid <NUM> that has been delivered to the wound <NUM> (see also <FIG>) and to control the purge operation to remove at least the determined volume of instillation fluid <NUM> from the wound dressing apparatus <NUM>. In various exemplary embodiments, the purge control circuit <NUM> is configured to determine a maximum volume of instillation fluid <NUM> that may be present within the wound dressing apparatus <NUM>. For example, the purge control circuit <NUM> may be configured to determine a total volume of the wound dressing apparatus <NUM> by accessing a look-up table stored in memory <NUM>. The look-up table may include a list of target therapy pressures at the wound <NUM> and a corresponding list of valve operating times (e.g., periods) for the purge valve <NUM>. The operating times may be open times for the purge valve <NUM> (e.g., durations of time during which the purge valve <NUM> is operated in an open state) that are required to completely purge a volume of air through the wound dressing apparatus <NUM> that is greater than or equal to the total volume of the wound dressing apparatus <NUM>. The purge control circuit <NUM> may be configured to determine a valve operating time from the look-up table based on a target therapy pressure at the wound <NUM> (e.g., a target therapy pressure input by a user via a user interface on the therapy device <NUM> or stored in memory <NUM>).

In some embodiments, the purge control circuit <NUM> is configured to determine a valve operating time based on a predefined purge operating pressure that is applied to the removable fluid canister <NUM>. The predefined purge operating pressure may be greater than the target therapy pressure to ensure that the liquids (e.g., instillation fluid <NUM>, wound exudate, and other fluids <NUM>) can be carried up through the vacuum tubing <NUM> (see also <FIG>). The purge control circuit <NUM> may be configured to compare the target therapy pressure with the predefined purge operating pressure at the start of the purge operation and to adjust the negative pressure if needed. For example, the purge operating pressure may be <NUM> mmHg. In scenarios where the target therapy pressure is less than the purge operating pressure (e.g., <NUM> mmHg), the purge control circuit <NUM> may readjust the speed of the pneumatic pump <NUM> to increase the negative pressure within the removable fluid canister <NUM> during the purge operation (e.g., to a value that is approximately equal to the purge operating pressure). Conversely, in scenarios where the target therapy pressure is greater than or equal to the purge operating pressure, the purge control circuit <NUM> will operate the pneumatic pump <NUM> to maintain the negative pressure within the removable fluid canister <NUM> at a value that is approximately equal to the target therapy pressure.

The list of valve operating times stored in memory <NUM> may be determined by the purge control circuit <NUM> based on a total volume of the wound dressing apparatus <NUM>. Specifically, the valve operating times may be those required to flush a volume of air equal to the total volume of the wound dressing apparatus <NUM> through the sensing tubing <NUM> (e.g., the portion of the sensing tubing <NUM> between the purge valve <NUM> and the wound dressing <NUM>) and the vacuum tubing <NUM> (e.g., the portion of the vacuum tubing <NUM> between the wound dressing <NUM> and the removable fluid canister <NUM>). The valve operating times will vary depending on the negative pressure within the removable fluid canister <NUM> during the purge operation. The purge control circuit <NUM> may be configured to determine the total volume of the wound dressing apparatus <NUM> based on user inputs (e.g., via a user interface on the therapy device <NUM>). For example, the purge control circuit <NUM> may be configured to determine the total volume based on the diameter and length of at least one of the sensing tubing <NUM> and the vacuum tubing <NUM>. The times required to flush the volume of air through the wound dressing apparatus <NUM> (e.g., the purge times) may also be determined based on a type of filter <NUM> and a flow area through the filter <NUM>, and/or a calculation of the likely range of wound exudate, fluid viscosity, and the flow restriction through the wound dressing <NUM> (which together may be more than a theoretical purge time for a gas only volume). Alternatively, or in combination, the purge control circuit <NUM> may be configured to determine the purge times based directly on an instilled fluid volume provided to the purge control circuit <NUM> by an instillation control circuit (not shown) or based on a user specified value of the instilled fluid volume stored in memory <NUM>.

In various exemplary embodiments, the purge control circuit <NUM> may be configured to calculate the required purge time directly based on user inputs, tubing data, and/or operating data stored in memory <NUM>. In an exemplary embodiment, the air flow rate through the sensing tubing <NUM> (see also <FIG>) is approximately <NUM> cc/min (<NUM> cc/second). The vacuum tubing <NUM> is approximately <NUM> in length and has a diameter of approximately <NUM>. For the purposes of this example, the volume of the sensing tubing <NUM> can be assumed to be negligible relative to the volume of the vacuum tubing <NUM>. Based on these parameters, the required purge time of air through the wound dressing apparatus <NUM> (e.g., the required valve open time) is approximately <NUM>. In some embodiments, the purge control circuit <NUM> may be configured to double the required purge time (e.g., <NUM>) or increase the overall purge time by another scaling factor to ensure that all liquids are removed from the wound dressing apparatus <NUM> during the purge operation.

As shown in <FIG>, the purge control circuit <NUM> is configured to operate the pneumatic pump <NUM> and at least one of the safety relief valve <NUM> and the purge valve <NUM> by generating and providing control signals to the pneumatic pump <NUM> and/or the valves <NUM> and <NUM>. The control signals provided to the pneumatic pump <NUM> can cause the pneumatic pump <NUM> to activate, deactivate, or achieve a variable capacity or speed (e.g., operated at half speed, operate at full speed, etc.). Similarly, the control signals provided to the valves <NUM> and <NUM> can cause the valves <NUM> and <NUM> to open, close, or to cycle between an open and closed state at a predefined operating frequency.

In some embodiments, the purge control circuit <NUM> is configured to change the operating frequency (e.g., cycling frequency) of the valves <NUM> and <NUM> during operation. For example, the operating frequency of the purge valve <NUM> may be controlled/varied during a purge cycle to gradually increase a flow rate of air into the sensing tubing <NUM> (see also <FIG>) at a beginning of the purge operation and/or to gradually reduce the flow rate of air into the sensing tubing <NUM> at an end of the purge operation. Among other benefits, gradually transitioning the purge valve <NUM> between a closed state and an open state prevents a rapid increase or decrease in negative pressure at the wound <NUM>. For example, the purge control circuit <NUM> may transmit a first control signal to the purge valve <NUM> to operate the purge valve <NUM> at a first operating frequency to gradually introduce air into the wound dressing apparatus <NUM>. After a first period of time, the purge control circuit <NUM> may transmit a second control signal to the purge valve <NUM> to maintain the purge valve <NUM> in a fully open state (e.g., position) to allow air to pass through the purge valve <NUM> unimpeded. Near the end of the purge operation, the purge control circuit <NUM> may transmit a third control signal to the purge valve <NUM> to again operate the purge valve <NUM> at the first operating frequency to gradually reduce the flow rate of air into the sensing tubing <NUM>.

In other exemplary embodiments, the purge control circuit <NUM> may be configured to continuously vary the operating frequency of the purge valve <NUM> during the purge operation, for example, by using a PWM driven purge valve <NUM>. Among other benefits, cycling or fluttering the purge valve <NUM> at the beginning of the purge operation and at the end of the purge operation can reduce dynamic instability in the control system (e.g., instability relating to rapid changes in negative pressure in at least one of the wound <NUM> and the removable fluid canister <NUM>).

As shown in <FIG>, the controller <NUM> (e.g., the purge control circuit <NUM>) is communicatively coupled to the plurality of sensors and is configured to take action based on information (e.g., sensor data) received from each of the plurality of sensors. In various exemplary embodiments, the purge control circuit <NUM> is configured to initiate the purge operation based on information from at least one of the first pressure sensor <NUM> (e.g., the pressure sensor that is coupled to the removable fluid canister <NUM>) and the second pressure sensor <NUM> (e.g., the pressure sensor that is coupled to the sensing tubing <NUM>). For example, the purge control circuit <NUM> may be configured to initiate the purge operation based on a determination that the negative pressure of the removable fluid canister <NUM> is above a predefined purge trigger pressure (e.g., a negative pressure that is much greater than a target therapy pressure at the wound <NUM>), which can occur when a volume of liquid accumulates within the vacuum tubing <NUM>. Alternatively, or in combination, the purge control circuit <NUM> may be configured to initiate the purge operation based on a determination that a difference between the negative pressure in the removable fluid canister <NUM> and the negative pressure at the wound <NUM> exceeds a predefined threshold.

The purge control circuit <NUM> may also be configured to automatically control the pneumatic pump <NUM> during the purge operation based on sensor data; for example, to maintain the negative pressure of the removable fluid canister <NUM> to a value that is greater than a predefined target therapy pressure (e.g., a purge operating pressure stored in memory <NUM>). Among other benefits, using automatic pump control based on sensor data ensures that a target therapy pressure is maintained at the wound <NUM> (e.g., that performance targets can be achieved regardless of the additional hydraulic head caused by liquid in the vacuum tubing <NUM>).

In various exemplary embodiments, the purge control circuit <NUM> may be configured to repeat the purge operation for a predefined number of cycles and/or for a predefined time period to ensure that all liquids such as wound exudate, instillation fluid <NUM>, and other fluids <NUM> are fully removed from the wound dressing apparatus <NUM> (see also <FIG>). The predefined number of cycles and/or predefined time period may be input by a user (e.g., via user interface on the therapy device <NUM>) or otherwise stored in memory <NUM> (e.g., during manufacturing of the therapy device <NUM>).

Referring to <FIG>, a flow diagram of a method <NUM> of purging a wound dressing apparatus is shown, according to an exemplary embodiment. The method <NUM> may be implemented by a wound therapy system to remove liquids (e.g., wound exudate, instillation fluid <NUM>, and other fluids) from a wound dressing apparatus. The method <NUM> may be applied by the wound therapy system directly after instillation and/or routinely (e.g., periodically) during a treatment regimen by an NPWT system. The wound therapy system may be the same or similar to the wound therapy system <NUM> of <FIG>. For simplicity, similar numbering will be used to identify similar components. At <NUM>, a volume of instillation fluid <NUM> is provided to the wound dressing apparatus <NUM> by an instillation pump <NUM>. Block <NUM> is illustrated schematically in <FIG>. As shown in <FIG>, block <NUM> includes passing the volume of instillation fluid <NUM> from the instillation fluid canister <NUM>, through the instillation tubing <NUM>, and into the wound <NUM> (via the wound dressing <NUM>). Block <NUM> may continue until the wound <NUM> is completely filled with instillation fluid <NUM>. Alternatively, the volume of instillation fluid <NUM> provided to the wound <NUM> may be determined based on user inputs to the therapy device <NUM> or may be a predetermined value (e.g., stored in memory <NUM>).

At <NUM>, the wound therapy system <NUM> dwells (e.g., pauses, rests, etc.) with the instillation pump <NUM> and pneumatic pump <NUM> in a deactivated state (e.g., shut down, turned off) for a first period of time. Block <NUM> is shown schematically in <FIG>. During the dwell operation, instilled fluid <NUM> is allowed to remain within the wound <NUM>. At <NUM>, a pneumatic pump <NUM> applies a negative pressure to the wound dressing apparatus <NUM> to purge a first portion <NUM> of the instillation fluid <NUM> from the wound dressing apparatus <NUM> and into a removable fluid canister <NUM>. Block <NUM> is shown schematically in <FIG>. During block <NUM>, other fluids such as wound exudate may also be removed from the wound <NUM> and delivered into the removable fluid canister <NUM>. Block <NUM> may include operating the pneumatic pump <NUM>, in response to a control signal from a controller <NUM>, to apply the negative pressure for a predefined period of time (e.g., <NUM> minutes or another period of time that is required to achieve steady-state conditions within the wound dressing apparatus <NUM>). Block <NUM> may additionally include operating the pneumatic pump <NUM> based on sensor data from the second pressure sensor <NUM>. Specifically, block <NUM> may include operating the pneumatic pump <NUM> to automatically increase the negative pressure applied by the pneumatic pump <NUM> to the removable fluid canister <NUM> to offset any additional head height associated with remaining liquids in the vacuum tubing <NUM> (e.g., such that the wound <NUM> is maintained at the target therapeutic pressure).

At <NUM>, a controller <NUM> compares the negative pressure of the removable fluid canister <NUM> (e.g., via first pressure sensor <NUM>) with a purge trigger pressure to determine whether any liquids remain in the wound dressing apparatus <NUM>. The purge trigger pressure may be equal to a target therapy pressure at the wound <NUM> plus a predefined offset (e.g., <NUM> mmHg, or another suitable offset pressure indicative of liquid within the wound dressing apparatus <NUM>). In a scenario where the negative pressure of the removable fluid canister <NUM> is below the purge trigger pressure, the method <NUM> proceeds to block <NUM>. At <NUM>, the controller <NUM> compares an amount of time since the start of the NPWT regimen (e.g., since the start of block <NUM>) to a predefined fluid check period. The predefined fluid check period is a period of time during which the therapy device <NUM> continually checks to see if the negative pressure in the removable fluid canister <NUM> has exceeded the purge trigger pressure. It should be understood that the negative pressure in the removable fluid canister <NUM> may change over time due to the introduction of wound exudate into the vacuum tubing <NUM> and/or other parts of the wound dressing apparatus <NUM> (e.g., from the wound <NUM>). In a scenario where the negative pressure in the removable fluid canister <NUM> remains below the purge trigger pressure throughout the fluid check period, the method <NUM> proceeds to block <NUM>, and the controller <NUM> proceeds to implement a continuous NPWT regimen.

In the event the negative pressure of the removable fluid canister <NUM> exceeds the purge trigger pressure within the fluid check period, the method <NUM> proceeds to block <NUM>. At <NUM>, the controller <NUM> activates the purge valve <NUM> (while operating the pneumatic pump <NUM>) to pass a volume of air through the wound dressing apparatus <NUM> that is greater than or equal to the volume of instillation fluid <NUM> provided in block <NUM>. Block <NUM> includes purging a second portion <NUM> of the instillation fluid <NUM> from the wound dressing apparatus <NUM> into the removable fluid canister <NUM>. Block <NUM> is shown schematically in <FIG>. Block <NUM> may additionally include determining, by the controller <NUM> (e.g., the purge control circuit <NUM> of <FIG>), a valve open time (e.g., duration) during which the purge valve <NUM> is held in an open position. In some embodiments, determining the open time includes accessing a look-up table from memory <NUM> that includes a list of open times. The list of open times may be a function of different operating parameters such as the negative pressure in the removable fluid canister <NUM>, the volume of the wound dressing apparatus <NUM>, the volume of instillation fluid <NUM> delivered to the wound <NUM>, and/or other factors. Block <NUM> may include adjusting the open time to equal or substantially equal the target open time. Block <NUM> may further include sending a control signal to the pneumatic pump <NUM> to increase the negative pressure in the removable fluid canister <NUM> to the purge operating pressure (e.g., a value greater than the target therapy pressure to ensure the pressure is adequate to remove liquids from the vacuum tubing <NUM>).

At <NUM>, the controller <NUM> operates the purge valve <NUM> and the pneumatic pump <NUM> to maintain the negative pressure at the wound <NUM> at the target therapy pressure. Block <NUM> may include closing the purge valve <NUM> to prevent any additional purging of the wound dressing apparatus <NUM>. Block <NUM> may additionally include adjusting the operating speed of the pneumatic pump <NUM> to reduce the negative pressure in the removable fluid canister <NUM> (e.g., to reduce the negative pressure to the target therapy pressure or to another value that is lower than the purge operating pressure).

At <NUM>, the controller <NUM> determines whether the negative pressure in the removable fluid canister <NUM> is greater than the purge trigger pressure. In a scenario where the negative pressure in the removable fluid canister <NUM> exceeds the purge trigger pressure, the method <NUM> returns to block <NUM> and repeats the purge operation. Block <NUM> may additionally include recording a number of purge cycles. At <NUM>, the controller <NUM> compares the number of purge cycles with a predefined threshold number of cycles. In a scenario where the number of purge cycles exceeds the predefined number of cycles, or in a scenario where the negative pressure within the removable fluid canister <NUM> is less than the purge trigger pressure (after a purge), the method <NUM> proceeds to block <NUM> in which the standard NPWT regime is resumed. Block <NUM> is shown schematically in <FIG>. In other embodiments, the method <NUM> of <FIG> may include additional, fewer, and/or different operations.

The method <NUM> described in the exemplary embodiment of <FIG> should not be considered limiting. Many alternatives are possible without departing from the inventive concepts disclosed herein. For example, the purge operation may also be performed periodically during the normal NPWT regimen (e.g., after a bulk of the instillation fluid <NUM> has been removed and the negative pressure within the removable fluid canister <NUM> is below the purge trigger pressure). Among other benefits, repeating the purge cycle periodically during treatment may also help to prevent the buildup of wound exudate that might otherwise clog the vacuum tubing <NUM> and/or interfere with accurate pressure measurements of the wound <NUM>. In some embodiments, the purge operation may include increasing the open times for the purge valve <NUM> to a longer duration and/or reapplying the purge operation more frequently throughout the NPWT regimen. For example, the wound therapy system <NUM> may be configured to increase open times for the purge valve <NUM> to <NUM>-<NUM> second intervals every <NUM> minutes directly after an instillation/dwell operation for a total time of <NUM>-<NUM> minutes or another suitable time to aid with fluid removal. As described above, during the purge operation, the controller <NUM> may operate the pneumatic pump <NUM> to apply a higher negative pressure to the removable fluid canister <NUM> (e.g., greater than a target therapy pressure at the wound <NUM>) to ensure that enough pressure is provided to the return fluid canister <NUM> to overcome any head in the vacuum tubing <NUM> due to trapped liquids.

Claim 1:
A wound therapy system (<NUM>), comprising:
a wound dressing apparatus (<NUM>) fluidly coupled to a wound (<NUM>);
a pneumatic pump (<NUM>) fluidly coupled to the wound dressing apparatus (<NUM>) and configured to apply a negative pressure to the wound dressing apparatus (<NUM>);
a valve (<NUM>) fluidly coupled to the wound dressing apparatus (<NUM>) at a location that is upstream of the wound (<NUM>); and
a controller (<NUM>) communicatively coupled to the pneumatic pump (<NUM>) and the valve (<NUM>),
the system characterized in that the controller is configured to:
determine a volume of instillation fluid that has been delivered to the wound (<NUM>);
operate the pneumatic pump (<NUM>) and the valve (<NUM>) to apply the negative pressure to the wound dressing apparatus (<NUM>) to purge a first portion of the instillation fluid from the wound dressing apparatus (<NUM>); and
operate the pneumatic pump (<NUM>) and the valve (<NUM>) during a purge operation to deliver a volume of air through the wound dressing apparatus (<NUM>) that is approximately equal to or greater than the volume of instillation fluid to purge a second portion of the instillation fluid from the wound dressing apparatus (<NUM>).