Patent Description:
During operation of a NPWT system, exudates and other fluids from a wound may be collected in a canister detachably mated with the NPWT system. If the canister reaches capacity during therapy, a caregiver may replace the full canister with a new canister. NPWT systems may be used with canisters of different sizes, such as <NUM>, <NUM>, and <NUM>,<NUM>. In various situations, it may be desirable to know the volume of the canister that is in fluid communication with the NPWT system. Accordingly, in some NPWT systems, a canister may be provided with one or more markings or other identifiable features representative of the volume of the canister. The canister size is then entered into the NPWT system manually or by electronically scanning marking on the canister.

<CIT> concerns systems and methods for controlling operation of negative pressure wound therapy apparatus. <CIT> concerns a disposable cartridge for vacuum actuated fluid delivery. <CIT> concerns a system for determining a fill status of a canister of fluid in a reduced pressure treatment system.

It may be advantageous to provide a NPWT system configured to estimate a volume of an attached canister without requiring any user input and/or a scanning element.

The present invention provides a wound therapy system according to claim <NUM>. Further optional features are provided in the dependent claims. According to a first implementation (not claimed) of the present disclosure, a wound therapy system includes a fluid canister, a housing, a pump and a controller. The housing includes a canister receiving attachment to which the canister is releasably secured. The pump is fluidly coupled to the canister and is configured to draw a negative pressure within an interior of the canister. The controller is configured to operate the pump to apply a vacuum to the interior of the canister, obtain one or more measurements representative of a flow of air that is exhausted from the canister interior following the initiation of the operation of the pump and estimate the volume of the canister based on the obtained flow rate measurements.

In some embodiments, the controller is configured to prevent operation of the wound therapy system in response to estimating that the volume of the fluid canister exceeds a predetermined volume corresponding to an upper limit of a quantity of fluid that may be safely evacuated from a patient.

In some embodiments, the controller comprises a memory storing model airflow curves representative of the flow of air that is exhausted from a canister interior during the operation of the wound therapy system with canisters defined by varying volumes.

In some embodiments, the controller is configured to initiate a timer upon initiating operation of the pump. The one or more measurements representative of the flow of air obtained by the controller comprise a flow rate measurement obtained at a predetermined time following the initiation of the operation of the timer. The controller is configured to stop the timer and the operation of the pump in response to the controller obtaining a measurement that the flow of air is below a predetermined flow rate.

In some embodiments, the controller is configured to estimate the volume of the canister by identifying a model airflow curve that is defined by a flow rate at the predetermined time that is substantially similar to the flow rate measurement obtained by the controller. The controller is configured to estimate the volume of the canister by identifying a model airflow curve that is defined by a flow rate that is substantially the same as the predetermined flow rate at a time corresponding to the time interval defined between the initiation of the pump and the stopping of the pump.

In some embodiments, the wound therapy system further includes a wound dressing configured to be sealed about a wound site and a conduit having a first end attached to the wound dressing and a second end attached to a canister inlet. A flow restrictor is positioned between the conduit second end and the canister inlet.

According to one implementation (not claimed) of the present disclosure, a wound therapy system includes a fluid canister, a housing, and a pump. The housing includes a canister receiving attachment to which the canister is releasably secured. The pump is fluidly coupled to the canister and configured to draw a negative pressure within an interior of the canister. The controller is configured to operate the pump to apply a vacuum to the interior of the canister, obtain one or more measurements representative of a pressure within the canister interior following the initiation of the operation of the pump, and estimate the volume of the canister based on the obtained pressure measurements.

In some embodiments, the controller is configured to prevent operation of the wound therapy system in response to estimating that the volume of the fluid canister exceeds a predetermined volume corresponding to an upper limit of a quantity of fluid that may be safely evacuated from a patient. The controller comprises a memory storing model pressure curves representative of the change in pressure within a canister interior during the operation of the wound therapy system with canisters defined by varying volumes. In some embodiments, the controller is configured to initiate a timer upon initiating operation of the pump.

In some embodiments, the one or more measurements representative of pressure within the canister interior are obtained by the controller comprise a pressure measurement obtained at a predetermined time following the initiation of the operation of the timer. The controller may be configured to stop the timer and the operation of the pump in response to the controller obtaining a pressure measurement that corresponds to a predetermined pressure.

In some embodiments, the controller is configured to estimate the volume of the canister by identifying a model pressure curve that is defined by a pressure at the predetermined time that is substantially similar to the pressure measurement obtained by the controller. The controller may be configured to estimate the volume of the canister by identifying a model pressure curve that is defined by a pressure that is substantially the same as the predetermined pressure at a time corresponding to the time interval defined between the initiation of the pump and the stopping of the pump.

In some embodiments, the wound therapy system further includes a wound dressing configured to be sealed about a wound site and a conduit having a first end attached to the wound dressing and a second end attached to a canister inlet. A flow restrictor may be positioned between the conduit second end and the canister inlet.

According to one implementation (not claimed) of the present disclosure, a method of estimating a volume of a canister attached to a negative pressure wound therapy device includes attaching a first canister to a wound therapy device, attaching a conduit between an inlet of the canister and a first wound dressing, operating a pump of the therapy device to attain a desired predetermined negative pressure within a treatment space defined underneath the wound dressing, obtaining one or more measurements of the airflow from an outlet of the canister following the initiation of the pump, obtaining model airflow data curves representative of the change in the rate of airflow from a canister interior during the operation of a wound therapy system with canisters defined by varying volumes, and estimating a volume of the canister using the measured airflow and the obtained model airflow data curves.

In some embodiments, an alert is generated in response to determining that the estimated volume of the canister exceeds a predetermined volume corresponding to an upper limit of a quantity of fluid that may be safely evacuated from a patient.

In some embodiments, a timer is initiated upon initiating operation of the pump. In some embodiments, the airflow measurement is obtained at a predetermined time following the initiation of the operation of the timer. The timer may be stopped in response to the controller obtaining an airflow measurement that is below a predetermined flow rate. The volume of the canister is estimated by identifying a model airflow curve that is defined by a flow rate at the predetermined time that is substantially similar to the flow rate measurement obtained by the controller.

In some embodiments, the volume of the canister is estimated by identifying a model airflow curve that is defined by a flow rate that is substantially the same as the predetermined flow rate at a time corresponding to the time interval defined between the initiation of the pump and the stopping of the pump.

In some embodiments, a volume of the canister is detected using one or more markers or indicators provided on the canister. The detected volume is compared against the estimated volume and an alert is generated if the detected volume and the estimated volume are not substantially the same.

In some embodiments, the first canister is removed from the wound therapy device after the canister volume has been estimated. A second canister is attached to the wound therapy device. A conduit is attached between an inlet of the second canister and a second wound dressing. The pump of the therapy device is operated to attain a desired predetermined negative pressure within a treatment space defined underneath the second wound dressing. One or more measurements of the airflow from an outlet of the second canister following the initiation of the pump are obtained. A volume of the second canister is estimated using the measured airflow and the obtained model airflow data curves. Estimating the volume of the first canister includes making a binary distinction as to whether the canister volume is greater or less than a predetermined volume.

According to one implementation (not claimed) of the present disclosure, a method of estimating a volume of a canister attached to a negative pressure wound therapy device includes attaching a first canister to a wound therapy device, attaching a conduit between an inlet of the canister and a first wound dressing, operating a pump of the therapy device to attain a desired predetermined negative pressure within a treatment space defined underneath the wound dressing, obtaining one or more measurements of pressure within an interior of the canister following the initiation of the pump, obtaining model pressure data curves representative of the change in pressure within the canister interior during the operation of a wound therapy system with canisters defined by varying volumes, and estimating a volume of the canister using the measured pressure and the obtained model pressure data curves.

In some embodiments, a timer is initiated upon initiating operation of the pump. In some embodiments, the pressure measurement is obtained at a predetermined time following the initiation of the operation of the timer. The timer is stopped in response to the controller obtaining a pressure measurement that is below a predetermined pressure. In some embodiments, the volume of the canister is estimated by identifying a model pressure curve that is defined by a pressure at the predetermined time that is substantially similar to the pressure measurement obtained by the controller. The volume of the canister may be estimated by identifying a model pressure curve that is defined by a pressure that is substantially the same as the predetermined pressure at a time corresponding to the time interval defined between the initiation of the pump and the stopping of the pump.

In some embodiments, the first canister is removed from the wound therapy device after the canister volume has been estimated. A second canister is attached to the wound therapy device. A conduit is attached between an inlet of the second canister and a second wound dressing. The pump of the therapy device is operated to attain a desired predetermined negative pressure within a treatment space defined underneath the second wound dressing. One or more measurements of the pressure within an interior of the second canister following the initiation of the pump are obtained. A volume of the second canister is estimated using the measured pressure and the obtained model pressure data curves. In some embodiments, estimating a volume of the first canister includes making a binary distinction as to whether the canister volume is greater or less than a predetermined volume.

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 NPWT system and method of its use is shown according to various exemplary embodiments. The NPWT system generally includes a therapy device and a wound dressing. A removed fluid canister is fluidly coupled to each of the therapy device and wound dressing, and is configured to retain fluids (e.g. wound exudate, fluid previously instilled to the wound site during instillation therapy, etc.) removed from the wound site during use of the therapy device. The wound therapy device is configured to accept and be used with fluid canisters of differing volumes.

As will be described in more detail below, the NPWT system is configured to estimate the volume of the fluid canister upon initiation of treatment using the NPWT system by observing one or more parameters such as pressure, flow rate, pump ripple decay, etc. as air is evacuated from a negative pressure circuit defined by the wound treatment space volume defined between the wound dressing and a wound site about which the wound dressing is applied, the fluid canister, and fluid tubing extending between the wound site and the fluid canister. These observed changes are compared against previously obtained model data to estimate the volume of the fluid canister.

Because the volume estimated by the NPWT system using the methods described herein is obtained based on measurements that are based on the physical structure of the canister, the NPWT system may provide a more reliable option via which a volume of a canister may be estimated and/or via which a previously obtained volume may be confirmed, and may avoid or entirely prevent errors that could otherwise occur as a result of a canister marker or other identifier representative of a volume of a canister improperly identifying the volume of the canister. Additionally, the ability of the NPWT system to provide a canister volume estimate without requiring that the canister be provided with markings or other volume identifying elements allows the NPWT system to be used to provide volume estimates irrespective of whether the attached canister includes such markings. Furthermore, because the NPWT system is configured to use measurements obtained during an initial draw down of the negative pressure circuit to estimate volume, the NPWT system requires no additional user input to provide such volume estimates than would otherwise be required to operate the NPWT system.

As noted above, the NPWT system may be used to provide volume estimates independent of any markings provided on a container and intendent of any user input and/or the incorporation of a reader or other scanning element into the NPWT system. However, according to some embodiments, the NPWT system may optionally receive a user input canister volume and/or may include a reader or other scanning element that may be used to read a volume represented by the markings of other volume identifiers provided on a canister that is attached to the therapy device. In such embodiments, the methods and systems described herein may provide the NPWT system with a built in, integrated error-detection system that may alert a user to situations in which there is a discrepancy between the volume estimates.

As will be understood, the canister volume estimated by the NPWT system may be used for any number of purposes, including, e.g. preventing leaks and/or damage to the therapy device; minimizing risks associated with the use of the wound therapy system; monitoring the progress of wound treatment; etc. For example, in some situations the NPWT system may be configured to limit or prevent use of the NPWT system under potentially unsafe conditions during use of the NPWT system in a non-medical setting (e.g., in a home-use setting) or in other situations in which a patient may not be under constant medical supervision. In such situations the NPWT system may be configured to alert a user (optionally) and block operation of the NPWT system (as claimed) in the event that the volume of a canister attached to the therapy device is estimated by the NPWT system to exceed than an upper limit of a quantity of fluid that may be safely evacuated from a wound site. As such, the NPWT system prevents a situation in which the use of a large canister with the therapy device would otherwise allow the NPWT system to continue operating to withdraw fluid from the wound site even after this threshold quantity had been exceeded.

Referring to <FIG> and <FIG>, a negative pressure wound therapy (NPWT) system <NUM> is shown according to an exemplary embodiment. NPWT system <NUM> is shown to include a therapy device <NUM> fluidly connected to a wound dressing <NUM> via a conduit <NUM>. Wound dressing <NUM> may be adhered or sealed to a patient's skin <NUM> surrounding a wound <NUM> to define a treatment space <NUM>. Several examples of wound dressings <NUM> which can be used in combination with NPWT system <NUM> are described in detail in <CIT>, <CIT>, <CIT>, and <CIT>.

Therapy device <NUM> can be configured to provide negative pressure wound therapy by reducing the pressure within the treatment space <NUM>. Therapy device <NUM> can draw a vacuum within the treatment space <NUM> (relative to atmospheric pressure) by removing fluids such as 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 wound <NUM> may include instillation fluid previously delivered to wound <NUM>. Instillation fluid 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 wound <NUM> during wound treatment. In some embodiments, therapy device <NUM> is configured to deliver instillation fluid to wound <NUM>, as described in <CIT>.

Fluids removed from wound <NUM> pass through conduit <NUM> and are collected in a removed fluid canister <NUM>. Conduit <NUM> may have a first end coupled to an inlet of the canister <NUM> and a second end fluidly coupled to the wound treatment space <NUM> via the wound dressing <NUM>. As will be described in more detail below, according to some embodiments, a restriction element <NUM> may be provided between the opening <NUM> of the canister <NUM> and the first end of the conduit <NUM> and/or elsewhere along the conduit <NUM>. According to some embodiments, the restriction element <NUM> may define a fixed size opening that is smaller than an opening defined by the inlet of the canister <NUM> and/or the inlet of the first end of the conduit <NUM>. In other embodiments, the size of the opening defined by the restriction element <NUM> may be varied manually and/or automatically as desired.

The canister <NUM> is configured to collect wound exudate and other fluids removed from wound <NUM>. The canister <NUM> is detachable from therapy device <NUM> to allow canister <NUM> to be emptied and replaced as needed. The canister <NUM> may be defined by any desired volume, with canisters <NUM> of differing volumes interchangeably being configured to be attached to and used with the therapy device <NUM>.

In various embodiments, the canister <NUM> may optionally include one or more markings or other identifiable features via which a user and/or the therapy device <NUM> may determine the volume of the canister <NUM>. For example, in some embodiments, the therapy device <NUM> may optionally include a scanner or other reader configured to read a marking or readable structure provided on or associated with the canister <NUM>. According to other embodiments, the canister <NUM> may optionally be formed without any markings or other identifiable features indicative of a size or volume of the canister <NUM>.

Referring to <FIG>, a block diagram illustrating the therapy device <NUM> in greater detail is shown according to an exemplary embodiment. As illustrated by <FIG>, therapy device <NUM> includes a pneumatic pump <NUM>, and may also optionally include a relief valve <NUM>, a filter <NUM>, and a controller <NUM>. Pump <NUM> can be fluidly coupled to canister <NUM> (e.g., via conduit <NUM>) and can be configured to draw a vacuum within canister <NUM> by pumping air out of canister <NUM>. In some embodiments, pump <NUM> is configured to operate in both a forward direction and a reverse direction. For example, pump <NUM> can operate in the forward direction to pump air out of canister <NUM> and decrease the pressure within canister <NUM>. Pump <NUM> can operate in the reverse direction to pump air into canister <NUM> and increase the pressure within canister <NUM> and/or to instill fluid to the wound <NUM>. Pump <NUM> can be controlled by controller <NUM>, described in greater detail below.

Filter <NUM> can be positioned between canister <NUM> and pump <NUM> (e.g., along conduit <NUM>) such that the air pumped out of canister <NUM> passes through filter <NUM>. Filter <NUM> can be configured to prevent liquid or solid particles from entering conduit <NUM> and reaching pump <NUM>. Filter <NUM> may include, for example, a bacterial filter that is hydrophobic and/or lipophilic such that aqueous and/or oily liquids will bead on the surface of filter <NUM>. Pump <NUM> can be configured to provide sufficient airflow through filter <NUM> such that the pressure drop across filter <NUM> is not substantial (e.g., such that the pressure drop will not substantially interfere with the application of negative pressure to the wound treatment space <NUM>).

Valve <NUM> can be fluidly connected with pump <NUM> and filter <NUM> via conduit <NUM>. In some embodiments, valve <NUM> is configured to control airflow between conduit <NUM> and the environment around therapy device <NUM>. For example, valve <NUM> can be opened to allow airflow into conduit <NUM>, and closed to prevent airflow into conduit <NUM>. Valve <NUM> can be opened and closed by controller <NUM>. The negative pressure circuit may include any component of the NPWT system <NUM> that can be maintained at a negative pressure when performing negative pressure wound therapy (e.g., conduit <NUM>, canister <NUM>, conduit <NUM>, and/or wound treatment space <NUM>).

In some embodiments, therapy device <NUM> includes one or more sensors. For example, therapy device <NUM> is shown to include one or more pressure sensors <NUM> configured to measure the pressure within canister <NUM> and/or the pressure within the wound treatment space <NUM>. Pressure measurements recorded by pressure sensor <NUM> can be communicated to controller <NUM>. According to various embodiments, the controller <NUM> may use the pressure measurements from pressure sensor(s) <NUM> to maintain the wound <NUM> at a desired negative pressure. For example, controller <NUM> can activate pump <NUM> in response to a pressure measurement from pressure sensor <NUM> exceeding a negative pressure setpoint in order to reduce the pressure at wound <NUM>. In various embodiments, the therapy device <NUM> may additionally, or alternatively, include one or more flow rate sensors <NUM> configured to measure a rate of airflow into and/or out from the fluid canister <NUM> and/or conduit <NUM>.

Referring to <FIG>, controller <NUM> is shown to include a processor <NUM> and memory <NUM>. 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. 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.). According to various embodiments, the processor <NUM> is configured to operate the controller to automatically estimate the volume of a canister <NUM> that is attached to the therapy device <NUM>.

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 processor <NUM> and may include computer code for executing (e.g., by processor <NUM>) one or more processes described herein. When processor <NUM> executes instructions stored in memory <NUM>, processor <NUM> generally configures controller <NUM> to complete such activities.

According to various embodiments, the memory <NUM> is configured to store canister volume estimation logic <NUM>, which, when executed, is configured use stored model data <NUM> and pressure data obtained using pressure sensor <NUM>, flow rata data obtained using flow rate sensor <NUM> and/or pump ripple data to estimate a volume of the canister <NUM> that is attached to the therapy device <NUM>. In some embodiments in which an optionally provided flow restriction element <NUM> is defined by an actuatable element, the canister volume estimation logic <NUM> may optionally additionally be configured to vary the opening defined by the restriction element <NUM>, such as, e.g., by narrowing the opening of the restriction element <NUM> during the drawdown of the negative pressure circuit.

Controller <NUM> is shown to include a pump controller <NUM>. Pump controller <NUM> can be configured to operate pump <NUM> by generating and providing control signals to pump <NUM>. The control signals provided to pump <NUM> can cause pump <NUM> to activate, deactivate, or achieve a variable capacity or speed (e.g., operate at half speed, operate at full speed, etc.).

In some embodiments, pump controller <NUM> may receive input from an optionally provided canister sensor configured to detect whether canister <NUM> is present. Pump controller <NUM> can be configured to activate pump <NUM> only when canister <NUM> is present. For example, pump controller <NUM> can check whether canister <NUM> is present and can activate pump <NUM> in response to a determination that canister <NUM> is present. However, if canister <NUM> is not present, pump controller <NUM> may prevent pump <NUM> from activating.

Controller <NUM> is shown to include a pressure monitor <NUM>. Pressure monitor <NUM> can be configured to monitor the pressure within canister <NUM> and/or the pressure within the wound treatment space <NUM> using feedback from pressure sensor <NUM>. For example, pressure sensor <NUM> may provide pressure measurements to pressure monitor <NUM>. Pressure monitor <NUM> can use the pressure measurements to determine the pressure within canister <NUM> and/or the pressure within wound dressing <NUM> or wound treatment space <NUM> in real-time. As will be understood, according to various embodiments, the pressure measurement values relied upon in estimating the volume of the fluid canister <NUM> by the canister volume estimation circuit <NUM> may be pressure measurements provided by the pressure monitor <NUM>.

The controller <NUM> may also include a flow rate monitor <NUM>. Flow rate monitor <NUM> can be configured to monitor the flow rate of air into and/or out from the canister <NUM> a using feedback from flow rate sensor <NUM>. For example, flow rate sensor <NUM> may provide flow rate measurements to flow rate monitor <NUM>. Flow rate monitor <NUM> can use the pressure measurements to determine the rate of flow into and/or out from the canister <NUM> in real-time. As will be understood, according to various embodiments, the flow rate measurement values relied upon in estimating the volume of the fluid canister <NUM> by the canister volume estimation circuit <NUM> may be flow rate measurements provided by the flow rate monitor <NUM>.

In some embodiments, therapy device <NUM> includes a data communications interface <NUM> (e.g., a USB port, a wireless transceiver, etc.) configured to receive and transmit data. Communications interface <NUM> may include wired or wireless communications interfaces (e.g., jacks, antennas, transmitters, receivers, transceivers, wire terminals, etc.) for conducting data communications external systems or devices. In various embodiments, the communications may be direct (e.g., local wired or wireless communications) or via a communications network (e.g., a WAN, the Internet, a cellular network, etc.). For example, communications interface <NUM> can include a USB port or an Ethernet card and port for sending and receiving data via an Ethernet-based communications link or network. In another example, communications interface <NUM> can include a Wi-Fi transceiver for communicating via a wireless communications network or cellular or mobile phone communications transceivers.

In some embodiments, therapy device <NUM> includes a user interface <NUM>. User interface <NUM> may include one or more buttons, dials, sliders, keys, or other input devices configured to receive input from a user. User interface <NUM> may also include one or more display devices (e.g., LEDs, LCD displays, etc.), speakers, tactile feedback devices, or other output devices configured to provide information to a user. In some embodiments, the pressure measurements recorded by pressure sensor <NUM> and/or flow rate measurements records by the flow rate sensor <NUM> are presented to a user via user interface <NUM>. User interface <NUM> can also display alerts generated by controller <NUM>.

Following the application of a wound dressing <NUM> to the skin <NUM> surrounding a wound <NUM>, NPWT treatment is initiated using the NPWT system <NUM> by closing valve <NUM> (if included) and operating pump <NUM> to draw a vacuum within the negative pressure circuit defined by the canister <NUM>, tubing <NUM> and wound treatment space <NUM> defined between the wound <NUM> and the wound dressing <NUM>. The operation of the pump <NUM> is continued until a desired negative pressure has been attained within the treatment space <NUM> as, e.g., determined by monitoring pressure using pressure sensor(s) <NUM>), at which point operation of the pump <NUM> may be ceased. As will be described in more detail below, according to various embodiments, the NPWT system <NUM> is configured to estimate a volume of the canister <NUM> attached to (either directly, or via tubing) the therapy device <NUM> using pressure, flow rate, and/or pump ripple measurement obtained during the initial draw-down of the negative pressure circuit. Following the attainment of the desired negative pressure at the wound space <NUM>, NPWT treatment using the NPWT system <NUM> may continue according to any number of desired treatment protocols.

Referring to <FIG>, a model graph representative of changes in pressure and flow rate during operation of NPWT systems <NUM> having varying sized canisters <NUM> operated under similar operating conditions is shown according to one embodiment. Given the large volume defined by the interior of the fluid canister <NUM> and the substantial lack of resistance to the flow of air out of the canister <NUM> (apart from the minimal resistance encountered as air flows through optionally provided filter <NUM>), the pump <NUM> operates under substantially free flow conditions during an initial phase of the draw down process during which air is being evacuated from the interior of the canister <NUM>. However, once all (or substantially all of) the initial volume of air within the canister <NUM> has been evacuated, and as air begins to be evacuated from the conduit <NUM> and wound treatment space <NUM>, the increased flow resistance encountered as air flows through the narrow tubing <NUM> results in a measurable decrease of the rate of change of flow of air that is evacuated from the negative pressure circuit.

As noted above, according to some embodiments, a restriction element <NUM> configured to further narrow and restrict the flow of air being evacuated from the negative pressure circuit may optionally be incorporated between the canister <NUM> and the conduit <NUM>. By further increasing the resistance to the flow of air from the conduit <NUM> and wound treatment space <NUM>, the rate of airflow may be further reduced, resulting in an even more marked and pronounced changed in the measured flow which, which may facilitate the identification of the inflection point in the flow rate curve representative of the time at which all of (or substantially all of) the air in the canister <NUM> has been evacuated. As illustrated by <FIG>, given the larger volume defined by (and thus greater amount of air contained within) large canisters, the time interval between the initiation of the pump <NUM> and the occurrence of the inflection point in the flow rate curve will be greater for large canisters <NUM> than for smaller canisters <NUM>.

As also illustrated by the graph of <FIG>, during the initial, substantial free flow of air immediately following the initiation of pump <NUM>, pressure within the fluid canister <NUM> remains unchanged. or substantially unchanged. Negative pressure within the canister <NUM> slowly begins to increase as air continues to be evacuated from the canister <NUM> interior following the initiation of pump <NUM>. However, as illustrated by <FIG>, given the relatively large volume of the canister <NUM> interior (as compared to the remaining volume of the negative pressure circuit), negative pressure within the canister <NUM> does not measurably begin increasing until air has been entirely (or substantially entirely) evacuated from the canister <NUM>, at which point a marked and notable increase of the negative pressure within the canister <NUM> occurs. As illustrated by <FIG>, given the longer time required to evacuate all (or substantially all) of the air within larger canisters, the inflection point in the pressure curve (representative of the marked increase in pressure occurring upon all, or substantially all, of the air within the canister being evacuated) for a larger container will occur at the later time than the time associated with the inflection point in the pressure curve of smaller canisters <NUM>.

The NPWT system <NUM> is configured to utilize the notable and distinguishable inflection points associated with the changing pressure within a canister and the change in the rate of air being evacuated from the negative pressure circuit occurring in response to the evacuation of all (or substantially all) of the air from within a canister, and the variation in the time following initiation of the pump <NUM> at which these inflection points occur for canisters of differing volumes, to estimate the volume of a canister <NUM> that is attached to the therapy device <NUM>. According to various embodiments, measurements of pump ripple-reflective of the changes in the pump operation that occur between the evacuation of air from the canister <NUM> and the evacuation of air from the remainder of the negative pressure circuit-may also by obtained and used by the NPWT system <NUM> to estimate canister volume <NUM>. In particular, as illustrated by the representative pressure and flow rate data of <FIG> and <FIG>, according to various embodiments, the NPWT system <NUM> may be configured to obtain pressure, flow rate and/or pump ripple decay measurements representative of the operation of the NPWT system <NUM> with canisters of varying volumes and under a variety of different operating conditions (e.g. differing target pressures, differing initial pressure within the negative pressure circuit, relative humidity, differing volumes defined by the conduit <NUM> and wound treatment space, differing pumps, etc.). For example, the pressure and flow rate data of <FIG> and <FIG> is representative of the operation of one embodiment of a NPWT system <NUM> with <NUM>, <NUM> and <NUM> containers under temperature conditions of approximately <NUM> and a relative humidity of approximately <NUM>%. Graphs representative of the pressure and flow rate data of <FIG> and <FIG> are provided in <FIG> and <FIG>. respectively.

As illustrated by the graphs of <FIG> and <FIG>, the pressure and flow rate data obtained by the NPWT system <NUM> may exhibit noise owing to any number of different factors, including, e.g. pump ripple. Accordingly, in various embodiments, any number of, or combination of various function approximators, statistical methods, machine learning systems, model generators, etc. may optionally be used to smooth, curve fit, or otherwise process the data to generate model decay curves, such as, e.g., the model decay curves representatively illustrated by the embodiment of the model graph of <FIG>.

As illustrated by the model graph of <FIG>, although canisters <NUM> of differing volumes exhibit different changes in pressure, flow rate and pump ripple (not shown) over time, during certain intervals during the draw down process, such as, e.g., immediately following the initiation of the pump and/or once the target negative pressure has been substantially attained, the differences between the curves of varying sized canisters may be more difficult to accurately distinguish. Accordingly, in various embodiments, in addition to obtaining pressure, flow rate and/or pump ripple decay curves for NPWT systems operated with different sized canisters <NUM> and/or under varying condition, the NPWT system <NUM> may be configured to identify relevant ranges and/values of flow rate, pressure, ripple decay and/or time that correspond to the inflection points in the flow rate pressure and ripple decay curves against which time, pressure, flow and/or pressure measurements obtained during operation of the NPWT system <NUM> may be applied to facilitate and increase the accuracy of the estimate of the volume of the canister <NUM> attached to the therapy device <NUM>.

For example in embodiments in which the NPWT system <NUM> is configured to estimate a volume based on one or more parameter measurements obtained following the expiration of a timers (such as, e.g., the method of <FIG> and/or the method of <FIG>) the time interval selected for the timer may be selected to correspond to a time range having a lower limit equal to the time at which-according to the model data-an inflection in pressure, flow rate and/or pump ripple is expected to occur for a volume corresponding to the smallest anticipated canister <NUM> volume that would be expected to be used with the NPWT system <NUM> and an upper limit equal to the time at which-also according to the model date-an inflection in pressure, flow rate and/or pump ripple is expected to occur for a volume corresponding to the largest anticipated canister <NUM> volume that would be expected to be used with the NPWT system <NUM>.

Given the marked increase in negative pressure that occurs upon evacuation of the air from the canister <NUM> during a drawdown of the negative pressure circuit, according to embodiments in which the attainment of a predetermined pressure measurement is used by the NPWT system <NUM> to estimate canister <NUM> volume (such as, e.g. in the method of <FIG>), the pressure value selected as the predetermined pressure value may be selected to be between approximately ±<NUM>% of the pressure at the inflection point on the pressure decay curve.

Similarly, given the marked decrease in the change in the rate of airflow from the negative pressure that occurs upon evacuation of the air from the canister <NUM> during a drawdown of the negative pressure circuit, according to embodiments in which the attainment of a predetermined flow rate is used by the NPWT system <NUM> to estimate canister <NUM> volume (such as, e.g. in the method of <FIG>), the flow rate value selected as the predetermined flow rate value may be selected to be between approximately ±<NUM>% of the flow rate at the inflection point on the pressure decay curve. For example, in some embodiments, the predetermined flow rate may be between approximately <NUM>/min and approximately <NUM>/min, and more specifically, between approximately <NUM>/min and approximately <NUM>/min.

Referring to <FIG>, flowcharts of various methods for operating the NPWT system <NUM> are shown according to various embodiments. Shown in <FIG> is a representative embodiment of a method of providing NPWT treatment using the NPWT system <NUM> according to one embodiment. At step <NUM>, model data representative of changes in pressure, flow rate and/or pump ripple over time during an initial draw down of a negative pressure circuit under a variety of clinically relevant conditions and states (e.g. fluid canister volume, wound treatment space volumes, conduit volumes, dressing/foam characteristics, initial pressure within the negative pressure circuit, target negative pressure, etc.) is obtained from any desired source.

In some embodiments, the model data obtained at step <NUM> may comprise accessing model data <NUM> previously obtained and stored in the control <NUM> memory <NUM>. According to other embodiments, such model data may be generated using any number of, or combination of various function approximators, statistical method, machine learning systems, etc. The model data obtained at step <NUM> may include any number of different pressure decay curves, flow rate curves, pump ripple curves, functions, lookup tables, etc., and may be obtained as pre-existing information that is input and stored by the controller, and/or may be obtained and processed by the controller <NUM> during an optional, initial training procedure conducted by the controller <NUM> prior to the use of the NPWT system <NUM> to treat wound site <NUM>. For example, according to some embodiments, step <NUM> of obtaining model data may be performed as part of the assembly of the NPWT system <NUM> at the desired treatment site of step <NUM>. Non-limiting examples of various exemplary training procedures by which such relationships may be generated by the controller <NUM> are outlined in related, co-pending <CIT> and titled WOUND THERAPY SYSTEM WITH WOUND VOLUME ESTIMATION.

At step <NUM>, wound dressing <NUM> is applied to the patient's skin <NUM> surrounding a wound <NUM>, and the wound dressing <NUM> is fluidly connected to a fluid canister <NUM> that is attached to a therapy device <NUM>. Once the NPWT system <NUM> has been assembled, at step <NUM>, the pump <NUM> is operated to draw a vacuum in the negative pressure circuit.

According to various embodiments, at step <NUM>, the NPWT system <NUM> may optionally be configured to confirm that an initial free flow of air following the initiation of the pump <NUM> is attributable to the evacuation of air from the fluid canister <NUM>-as opposed to a problem in the NPWT system <NUM>. For example, according to some embodiments, the NPWT system <NUM> may be configured to differentiate the initial free flow of evacuated air from a gross leak resulting from the canister <NUM> being improperly attached to, or entirely omitted from, the therapy device <NUM> via the incorporation of one or more sensors or other elements configured to detect the attachment of the canister <NUM> to the therapy device <NUM>.

Although the initial evacuation of air from the negative pressure circuit is characterized by an initial free flow of air, under proper operating conditions, the flow of evacuated air from the negative pressure circuit gradually decreases as air from the canister <NUM> is emptied. In contrast, in the event of a leak in the tubing <NUM> and/or an improper seal of the wound dressing <NUM>, the flow of evacuated air from the negative pressure circuit may continue to flow for an extended period of time under free flow, or almost free conditions following the initial operation of the pump <NUM>. Accordingly, in some embodiments, at step <NUM>, the NPWT system <NUM> may additionally, or alternatively be optionally configured alert a user and/or terminate operation of the NPWT system <NUM> at step <NUM> in the event that such a leak in the negative pressure circuit is detected.

As will be discussed in more detail with reference to <FIG>, <FIG> and <FIG>, at step <NUM>, as air is evacuated from the negative pressure circuit during operation of the pump <NUM>, at least one of a flow rate of the air from the negative pressure circuit, a pressure within the interior of the canister <NUM> and/or a pump ripple is monitored. At step <NUM>, the measurements obtained from monitoring the one or more parameters during step <NUM> and the model data obtained at step <NUM> are used by the controller <NUM> to estimate the volume of the fluid canister <NUM>. This estimated volume may optionally be recorded at step <NUM> for future use by the wound therapy system <NUM>. At step <NUM>, treatment using the NPWT system <NUM> may be continued according to any number of various protocols.

Referring to <FIG>, a method of estimating a volume of a canister <NUM> using the NPWT system <NUM> is shown according to one embodiment. As shown in <FIG>, at step <NUM>, a timer is initiated to mark the start of the operation of the pump <NUM> at step <NUM>. Following the initiation of the timer, one or more of the: air flowing out from the negative pressure circuit, the pressure within the canister <NUM> and/or pump ripple is monitored at step <NUM>. As represented by step <NUM>, the one or more parameters are monitored until the monitored parameter has attained a predetermined value, at which point, at step <NUM>, the timer is stopped. At step <NUM>, the predetermined parameter value and the time that was required to attain the determined parameter value as measured at step <NUM> are compared to the model data previously obtained by the NPWT system <NUM> (such as, e.g. model data <NUM> stored in the memory <NUM>) representative of flow rate, pressure and/or pump ripple decay during operation of NPWT systems having varying sized canister volumes under operating conditions similar to those during step <NUM>-<NUM>. At step <NUM>, the volume of the canister <NUM> is estimated based on the identification of a model data set exhibiting a flow rate, pressure and/or pump ripple value reading corresponding to the predetermined value used in step <NUM> at a time corresponding substantially to the time interval measured at step <NUM>.

Referring to <FIG>, a method of estimating the volume of a canister <NUM> is shown according to another embodiment. As shown in <FIG>, at step <NUM>, a timer is set for a predetermined time. Upon setting the timer at step <NUM>, operation of the pump <NUM> is initiated at step <NUM>. According to various embodiments, the predetermined time interval set at step <NUM> may be selected to correspond to a time that is approximately equal to an estimated time that would be required to evacuate air from within the interior of the smallest size canister with which the NPWT system <NUM> would be expected to be used. Operation of the pump <NUM> is continued until the time interval set at step <NUM> has been determined to have expired at step <NUM>.

Upon expiration of the time interval at step <NUM>, at step <NUM>, a measurement of at least one or more of the flow rate of air being evacuated from the negative pressure circuit, the pressure in the canister <NUM> and/or pump ripple is obtained. (e.g., using flow rate sensor(s) <NUM> and/or pressure sensor(s) <NUM>). At step <NUM>, the time interval set at step <NUM> and the parameter measurement obtained at step <NUM> are compared to the model data previously obtained by the NPWT system <NUM> (such as, e.g. model data <NUM> stored in the memory <NUM>) representative of flow rate, pressure and/or pump ripple decay during operation of NPWT systems having varying sized canister volumes under operating conditions similar to those during step <NUM>-<NUM>. At step <NUM>, the volume of the canister <NUM> is estimated based on the identification of a model data set exhibiting a flow rate, pressure and/or pump ripple value reading corresponding to the parameter measurement obtained at step <NUM> at a time corresponding to the time interval set at step <NUM>.

As an alternative to waiting until a predetermined parameter value has been attained during the drawdown of the negative pressure circuit (such as, e.g., described with reference to the method of <FIG>) and/or as an alternative to waiting until a predetermined time interval has expired (such as, e.g. described with reference to the method of <FIG>) to compare parameter measurement(s) obtained during draw down of the negative pressure circuit to previously obtained model data <NUM>, as shown in <FIG>, according to some methods, measured flow rate, pressure and/or pump ripple measurements may be compared in real-time to previously obtained model data <NUM>. In such embodiments, a real-time comparison of the measured parameters to the model data may continue until sufficient data has been acquired to determine a statistically meaningful canister <NUM> volume estimate based on the identification of a model data decay curve that exhibits similar decay to that of the real-time parameter readings obtained at step <NUM>. As will be understood, according to some such embodiments, any number of different types of statistical modeling and analysis may be used as real-time measurements are obtained at step <NUM> and compared against the model data at step <NUM> to address any noise in the acquired data and/or to address discrepancies or variations between the acquired parameter measurements and the model data <NUM>.

As noted above, according to various embodiments, the volume of the canister <NUM> attached to the therapy device <NUM> may have previously been obtained using any other number of markings provided on the canister <NUM> and/or other systems for measuring volume. In some such embodiments, it may be desirable to verify this previously obtained canister <NUM> volume using any of the methods described herein. For example, as shown in <FIG>, in some such embodiments, after obtaining a canister <NUM> volume estimate at step <NUM> using any of the methods described herein, at step <NUM> the previously obtained volume measurement may be verified against the canister <NUM> volume estimated at step <NUM>. At step <NUM>, an alert may be generated in the event of a discrepancy between the canister <NUM> volume estimated at step <NUM> and the canister volume previously obtained using markings provided on the canister <NUM> and/or other systems for measuring volume. Otherwise, at step <NUM>, the verified fluid canister <NUM> volume may optionally be recorded at step <NUM>, and operation of the NPWT system <NUM> may continue at <NUM> as desired.

As also discussed above, in certain situations (such as, e.g., during home-based use of the NPWT system <NUM>), it may be advantageous to prevent use of the therapy device <NUM> with a fluid canister <NUM> having a volume that exceeds a predetermined threshold volume, such as, e.g. <NUM>. Accordingly, as illustrated by the method of <FIG>, in some embodiments, after obtaining an estimate of the volume of a canister <NUM> at step <NUM> (using any of the methods described herein), at step <NUM> the estimated canister <NUM> volume may be compared against the predetermined maximum canister volume at step <NUM>. Upon confirming that the canister <NUM> volume does not exceed the maximum allowed predetermined volume, at step <NUM> the estimated canister <NUM> volume may be recorded, and at step <NUM> operation of the NPWT system <NUM> may be continued as desired (such as, e.g., to provide NPWT to a patient in a home, or other medically unsupervised setting).

In the event that the volume of the canister <NUM> is determined to exceed the predetermined maximum volume at step <NUM>, at step <NUM> an alert may be generated. The alert generated <NUM> at step may be communicated to one or both of the patient, a medical provider, and/or any other number of individuals that may be involved in the treatment provided by the NPWT system <NUM>. In some embodiments, as an additional safety precaution, the NPWT system <NUM> may optionally be disabled (either permanently, for a predetermined time, or until re-enabled by an authorized user) to prevent the use of the NPWT system <NUM>. In some such embodiments, at step <NUM> an alert indicating the disablement of the NPWT system <NUM> may optionally be provided to a medical provider and/or any number of other individuals that may be involved in the treatment provided by the NPWT system <NUM>.

As will be understood, although the method of <FIG> has been described as being used to prevent the use of the NPWT system <NUM> with a canister <NUM> having an estimated volume that exceeds a predetermined maximum allowed volume, according to other embodiments, the method of <FIG> may be modified to instead be used to prevent the use of the NPWT system <NUM> in the event that the volume of the canister <NUM> is estimated to be less than a minimum, predetermined threshold volume.

In some situations, the volume of the canister <NUM> may be used solely for purposes of determining whether a canister <NUM> exceeds (or alternatively, is less than) an allowed (or required) threshold volume. Accordingly, as illustrated in <FIG>, in some embodiments, a method of operating the NPWT system <NUM> may omit the step of estimating the volume of the canister <NUM>, and instead may instead be configured to provide a binary assessment as to whether or not the volume of a canister <NUM> exceeds for is less than) a threshold volume.

As shown in <FIG>, at step <NUM> a timer may be set for a predetermined interval. Upon initiating the timer, operation of the pump <NUM> is initiated at step <NUM>. At step <NUM>, the pump <NUM> continues to operate until the expiration of the time interval set at step <NUM>, at which point, at step <NUM>, a measurement of at least one of the flow rate of air being evacuated from the negative pressure circuit, the pressure within the canister <NUM> and/or pump ripple is obtained.

At step <NUM>, the parameter measurement(s) obtained at step <NUM> is compared against a threshold parameter value to provide a binary distinction as to whether the canister <NUM> volume exceeds a predetermined maximum volume. The predetermined parameter value against which the parameter measurement obtained at step <NUM> is compared corresponds to the expected parameter value that would be measured during operation of the NPWT system <NUM> having a fluid canister defining the predetermined maximum volume at the same time following the initial operation of the NPWT system pump as the time interval at which the parameter measurement was obtained at step <NUM>. Depending on the parameter being compared, the determination of the measure parameter value being greater than or less than the threshold parameter value will be sufficient for the NPWT system <NUM> to determine whether to permit continued operation of the wound therapy system at step <NUM> and <NUM>, or whether to generate an alarm at step <NUM> and optionally disable the system at step <NUM> and alert a provide or other individual at step <NUM>.

The construction and arrangement of the systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements can be reversed or otherwise varied and the nature or number of discrete elements or positions can be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps can be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure.

The present disclosure contemplates methods, systems and program products on any machine-readable media for accomplishing various operations. The embodiments of the present disclosure can be implemented using existing computer processors, or by a special purpose computer processor for an appropriate system, incorporated for this or another purpose, or by a hardwired system. Embodiments within the scope of the present disclosure include program products comprising machine-readable media for carrying or having machine-executable instructions or data structures stored thereon. Such machine-readable media can be any available media that can be accessed by a general purpose or special purpose computer or other machine with a processor. By way of example, such machine-readable media can comprise RAM, ROM, EPROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to carry or store desired program code in the form of machine-executable instructions or data structures and which can be accessed by a general purpose or special purpose computer or other machine with a processor. Combinations of the above are also included within the scope of machine-readable media. Machine-executable instructions include, for example, instructions and data which cause a general purpose computer, special purpose computer, or special purpose processing machines to perform a certain function or group of functions.

Claim 1:
A wound therapy system (<NUM>) comprising:
a fluid canister (<NUM>) having a canister volume;
a housing including a canister receiving attachment to which the canister is releasably secured;
a pump (<NUM>) fluidly coupled to the canister and configured to draw a negative pressure within an interior of the canister; and
characterized by a controller (<NUM>) configured to:
operate the pump (<NUM>) to apply a vacuum to the interior of the canister;
obtain one or more measurements representative of at least one of a flow of air exhausted from the canister interior and a pressure within the canister interior following the initiation of the operation of the pump (<NUM>);
estimate the canister volume based on the measurement; and
prevent operation of the wound therapy system (<NUM>) in response to estimating that the canister volume exceeds a predetermined volume corresponding to an upper limit of a quantity of fluid that may be safely evacuated from a patient.