US20210077671A1 - Wound therapy system with wound volume estimation - Google Patents

Abstract

A wound therapy system includes a negative pressure circuit configured to apply negative pressure to a wound, a pump fluidly coupled to the negative pressure circuit and operable to control the negative pressure within the negative pressure circuit, a pressure sensor configured to measure the negative pressure within the negative pressure circuit or at the wound and a controller communicably coupled to the pump and the pressure sensor. The controller is configured to execute a pressure testing procedure including applying a pressure stimulus to the negative pressure circuit, observe a dynamic pressure response of the negative pressure circuit to the pressure stimulus using pressure measurements recorded by the pressure sensor, and estimate a wound volume of the wound based on the dynamic pressure response.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims the benefit of priority to U.S. Provisional Application No. 62/650,132, filed on Mar. 29, 2018, and U.S. Provisional Application No. 62/799,241, filed on Jan. 31, 2019, the complete disclosures of which are each incorporated herein by reference in their entireties.
BACKGROUND
• The present disclosure relates generally to a wound therapy system, and more particularly to a wound therapy system configured to estimate the volume of a wound.
• Negative pressure wound therapy (NPWT) is a type of wound therapy that involves applying a negative pressure to a wound site to promote wound healing. Some wound treatment systems apply negative pressure to a wound using a pneumatic pump to generate the negative pressure and flow required. Recent advancements in wound healing with NPWT involve applying topical fluids to wounds to work in combination with NPWT. However, it can be difficult to determine the appropriate volume of instillation fluid to deliver to the wound. Additionally, it can be difficult to accurately monitor and track healing progression over time.
SUMMARY
• One implementation of the present disclosure is a wound therapy system including a negative pressure circuit configured to apply negative pressure to a wound, a pump fluidly coupled to the negative pressure circuit and operable to control the negative pressure within the negative pressure circuit, a pressure sensor configured to measure the negative pressure within the negative pressure circuit or at the wound and a controller communicably coupled to the pump and the pressure sensor. The controller is configured to execute a pressure testing procedure including applying a pressure stimulus to the negative pressure circuit, observe a dynamic pressure response of the negative pressure circuit to the pressure stimulus using pressure measurements recorded by the pressure sensor, and estimate a wound volume of the wound based on the dynamic pressure response.
• In some embodiments, the negative pressure circuit includes a wound dressing sealable to skin surrounding the wound. In some embodiments, the negative pressure circuit includes at least one of an instillation fluid canister containing instillation fluid for delivery to the wound or a removed fluid canister containing fluid removed from the wound. In some embodiments, the negative pressure circuit includes tubing fluidly connecting the pump with the wound.
• In some embodiments, the negative pressure circuit includes a wound dressing sealable to skin surrounding the wound, at least one of an instillation fluid canister containing instillation fluid for delivery to the wound or a removed fluid canister containing fluid removed from the wound, and tubing fluidly connecting the instillation fluid canister or the removed fluid canister with the wound dressing.
• In some embodiments, the controller is configured to operate the pump to establish the negative pressure within the negative pressure circuit. In some embodiments, the testing procedure includes operating the pump to establish the negative pressure within the negative pressure circuit and applying the pressure stimulus after the negative pressure has been established within the negative pressure circuit.
• In some embodiments, the system includes a valve coupled to the negative pressure circuit and operable to controllably vent the negative pressure circuit. In some embodiments, applying the pressure stimulus includes opening the valve to allow airflow into the negative pressure circuit for a predetermined amount of time and closing the valve after the predetermined amount of time has elapsed. In some embodiments, applying the pressure stimulus further includes waiting for another predetermined amount of time after closing the valve and repeating the opening, closing, and waiting steps until the negative pressure reaches a threshold pressure value. In some embodiments, applying the pressure stimulus further includes operating the pump while the valve is closed to mitigate air leakage into the negative pressure circuit.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a depth of purge parameter defined as a difference between a measured value of the negative pressure before the valve is opened and a measured value of the negative pressure while the valve is open.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a rebound parameter defined as a difference between a measured value of the negative pressure after the valve is closed and a measured value of the negative pressure while the valve is open.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a delta parameter defined as a difference between a measured value of the negative pressure before the valve is opened and a measured value of the negative pressure after the valve is closed.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a leak rate parameter defined as a rate at which the negative pressure changes while the valve is closed.
• In some embodiments, the wound therapy system includes an orifice located along the negative pressure circuit and configured to allow air to leak into the negative pressure circuit at a known rate.
• In some embodiments, applying the pressure stimulus includes operating the pump to achieve a predetermined negative pressure within the negative pressure circuit and deactivating the pump upon reaching the predetermined negative pressure within the negative pressure circuit.
• In some embodiments, estimating the wound volume based on the dynamic pressure response includes determining values for one or more parameters that characterize the dynamic pressure response and applying the values of the one or more parameters as inputs to a model that defines a relationship between the one or more parameters and the wound volume.
• In some embodiments, the model that defines the relationship between the one or more parameters and the wound volume is a polynomial approximation model. In some embodiments, the model that defines the relationship between the one or more parameters and the wound volume is a neural network.
• In some embodiments, the controller is configured to generate the model that defines the relationship between the one or more parameters and the wound volume by executing a training procedure comprising applying the pressure stimulus to training circuit having a known volume, observing a dynamic pressure response of the training circuit to the pressure stimulus using pressure measurements recorded by the pressure sensor and associating the known volume with the dynamic pressure response of the training circuit.
• In some embodiments, generating the model further includes repeating the training procedure for a plurality of known volumes, observing the dynamic pressure response of the training circuit for each of the plurality of known volumes, and generating a correlation between the plurality of known volumes and the dynamic pressure response of the training circuit.
• In some embodiments, the controller is configured to execute the pressure testing procedure, observe the dynamic pressure response, and estimate the wound volume at a plurality of times during wound treatment. The controller can be configured to determine healing progression based on changes in the wound volume during wound treatment.
• In some embodiments, the controller is configured to determine a volume of instillation fluid to deliver to the wound based on the estimated wound volume. The controller can be configured to operate the pump to deliver the volume of instillation fluid to the wound.
• In some embodiments, the controller is configured to determine the volume of instillation fluid to deliver to the wound by multiplying the estimated wound volume by a fluid instillation factor. In some embodiments, the fluid instillation factor is less than one such that less than the total wound volume is filled with the instillation fluid. In some embodiments, the fluid instillation factor is between approximately 0.2 and approximately 0.8.
• Another implementation of the present disclosure is a method for estimating a wound volume of a wound. The method includes applying negative pressure to a wound using a negative pressure circuit, operating a pump fluidly coupled to the negative pressure circuit to control the negative pressure within the negative pressure circuit, measuring the negative pressure within the negative pressure circuit or at the wound, executing a pressure testing procedure including applying a pressure stimulus to the negative pressure circuit, observing a dynamic pressure response of the negative pressure circuit to the pressure stimulus using measurements of the negative pressure, and estimating the wound volume based on the dynamic pressure response.
• In some embodiments, the negative pressure circuit includes a wound dressing sealable to skin surrounding the wound. In some embodiments, the negative pressure circuit includes at least one of an instillation fluid canister containing instillation fluid for delivery to the wound or a removed fluid canister containing fluid removed from the wound. In some embodiments, the negative pressure circuit includes tubing fluidly connecting the pump with the wound.
• In some embodiments, the negative pressure circuit includes a wound dressing sealable to skin surrounding the wound, at least one of an instillation fluid canister containing instillation fluid for delivery to the wound or a removed fluid canister containing fluid removed from the wound, and tubing fluidly connecting the instillation fluid canister or the removed fluid canister with the wound dressing.
• In some embodiments, the method includes operating the pump to establish the negative pressure within the negative pressure circuit. In some embodiments, the testing procedure includes operating the pump to establish the negative pressure within the negative pressure circuit and applying the pressure stimulus after the negative pressure has been established within the negative pressure circuit.
• In some embodiments, the method includes operating a valve coupled to the negative pressure circuit to controllably vent the negative pressure circuit. In some embodiments, applying the pressure stimulus includes opening the valve to allow airflow into the negative pressure circuit for a predetermined amount of time and closing the valve after the predetermined amount of time has elapsed.
• In some embodiments, applying the pressure stimulus further includes waiting for another predetermined amount of time after closing the valve and repeating the opening, closing, and waiting steps until the negative pressure reaches a threshold pressure value. In some embodiments, applying the pressure stimulus further includes operating the pump while the valve is closed to mitigate air leakage into the negative pressure circuit.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a depth of purge parameter defined as a difference between a measured value of the negative pressure before the valve is opened and a measured value of the negative pressure while the valve is open.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a rebound parameter defined as a difference between a measured value of the negative pressure after the valve is closed and a measured value of the negative pressure while the valve is open.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a delta parameter defined as a difference between a measured value of the negative pressure before the valve is opened and a measured value of the negative pressure after the valve is closed.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a leak rate parameter defined as a rate at which the negative pressure changes while the valve is closed.
• In some embodiments, the method includes allowing air to leak into the negative pressure circuit at a known rate via an orifice located along the negative pressure circuit.
• In some embodiments, applying the pressure stimulus includes operating the pump to achieve a predetermined negative pressure within the negative pressure circuit and deactivating the pump upon reaching the predetermined negative pressure within the negative pressure circuit.
• In some embodiments, estimating the wound volume based on the dynamic pressure response includes determining values for one or more parameters that characterize the dynamic pressure response and applying the values of the one or more parameters as inputs to a model that defines a relationship between the one or more parameters and the wound volume.
• In some embodiments, the model that defines the relationship between the one or more parameters and the wound volume is a polynomial approximation model. In some embodiments, the model that defines the relationship between the one or more parameters and the wound volume is a neural network.
• In some embodiments, the method includes generating the model that defines the relationship between the one or more parameters and the wound volume by executing a training procedure comprising applying the pressure stimulus to training circuit having a known volume, observing a dynamic pressure response of the training circuit to the pressure stimulus using pressure measurements recorded by the pressure sensor, and associating the known volume with the dynamic pressure response of the training circuit.
• In some embodiments, generating the model further includes repeating the training procedure for a plurality of known volumes, observing the dynamic pressure response of the training circuit for each of the plurality of known volumes, and generating a correlation between the plurality of known volumes and the dynamic pressure response of the training circuit.
• In some embodiments, the method includes executing the pressure testing procedure, observing the dynamic pressure response, and estimating the wound volume at a plurality of times during wound treatment. The method may include determining healing progression based on changes in the wound volume during wound treatment.
• In some embodiments, the method includes determining a volume of instillation fluid to deliver to the wound based on the estimated wound volume and operating the pump to deliver the volume of instillation fluid to the wound.
• In some embodiments, determining the volume of instillation fluid to deliver to the wound includes multiplying the estimated wound volume by a fluid instillation factor. In some embodiments, the fluid instillation factor is less than one such that less than the total wound volume is filled with the instillation fluid. In some embodiments, the fluid instillation factor is between approximately 0.2 and approximately 0.8.
• Another implementation of the present disclosure is wound therapy system. The wound therapy system includes a negative pressure circuit configured to apply negative pressure to a wound, a canister containing instillation fluid for delivery to the wound, a pump operable to deliver the instillation fluid to the wound, a pressure sensor configured to measure the negative pressure within the negative pressure circuit or at the wound, and a controller communicably coupled to the pump and the pressure sensor. The controller is configured to execute a pressure testing procedure to estimate a wound volume of the wound, determine a volume of instillation fluid to deliver to the wound based on the estimated wound volume, and operate the pump to deliver the volume of instillation fluid to the wound.
• In some embodiments, the controller is configured to determine the volume of instillation fluid to deliver to the wound by multiplying the estimated wound volume by a fluid instillation factor. In some embodiments, the fluid instillation factor is less than one such that less than the total wound volume is filled with the instillation fluid. In some embodiments, the fluid instillation factor is between approximately 0.2 and approximately 0.8.
• In some embodiments, the negative pressure circuit includes a wound dressing sealable to skin surrounding the wound. In some embodiments, the negative pressure circuit includes tubing fluidly connecting the canister with the wound dressing.
• In some embodiments, the controller is configured to operate the pump to establish the negative pressure within the negative pressure circuit. In some embodiments, the pressure testing procedure includes operating the pump to establish the negative pressure within the negative pressure circuit and applying a pressure stimulus to the negative pressure circuit after the negative pressure has been established within the negative pressure circuit.
• In some embodiments, the wound therapy system includes an orifice located along the negative pressure circuit and configured to allow air to leak into the negative pressure circuit at a known rate.
• In some embodiments, the pressure testing procedure includes operating the pump to achieve a predetermined negative pressure within the negative pressure circuit and, upon reaching the predetermined negative pressure within the negative pressure circuit, deactivating the pump and observing a dynamic pressure response of the negative pressure circuit.
• In some embodiments, the system includes a valve coupled to the negative pressure circuit and operable to controllably vent the negative pressure circuit. In some embodiments, the pressure testing procedure includes opening the valve to allow airflow into the negative pressure circuit for a predetermined amount of time and closing the valve after the predetermined amount of time has elapsed.
• In some embodiments, the pressure testing procedure includes waiting for another predetermined amount of time after closing the valve and repeating the opening, closing, and waiting steps until the negative pressure reaches a threshold pressure value.
• In some embodiments, the pressure testing procedure includes applying a pressure stimulus to the negative pressure circuit, observing a dynamic pressure response of the negative pressure circuit to the pressure stimulus using pressure measurements recorded by the pressure sensor, and estimating the wound volume of the wound based on the dynamic pressure response. In some embodiments, the pressure testing procedure includes operating the pump while the valve is closed to mitigate air leakage into the negative pressure circuit.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a depth of purge parameter defined as a difference between a measured value of the negative pressure before the valve is opened and a measured value of the negative pressure while the valve is open.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a rebound parameter defined as a difference between a measured value of the negative pressure after the valve is closed and a measured value of the negative pressure while the valve is open.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a delta parameter defined as a difference between a measured value of the negative pressure before the valve is opened and a measured value of the negative pressure after the valve is closed.
• In some embodiments, the dynamic pressure response of the negative pressure circuit is characterized by a leak rate parameter defined as a rate at which the negative pressure changes while the valve is closed.
• In some embodiments, estimating the wound volume based on the dynamic pressure response includes determining values for one or more parameters that characterize the dynamic pressure response and applying the values of the one or more parameters as inputs to a model that defines a relationship between the one or more parameters and the wound volume.
• In some embodiments, the model that defines the relationship between the one or more parameters and the wound volume is a polynomial approximation model. In some embodiments, the model that defines the relationship between the one or more parameters and the wound volume is a neural network.
• In some embodiments, the controller is configured to generate the model that defines the relationship between the one or more parameters and the wound volume by executing a training procedure comprising applying the pressure stimulus to training circuit having a known volume, observing a dynamic pressure response of the training circuit to the pressure stimulus using pressure measurements recorded by the pressure sensor, and associating the known volume with the dynamic pressure response of the training circuit.
• In some embodiments, generating the model further includes repeating the training procedure for a plurality of known volumes, observing the dynamic pressure response of the training circuit for each of the plurality of known volumes, and generating a correlation between the plurality of known volumes and the dynamic pressure response of the training circuit.
• In some embodiments, the controller is configured to execute the pressure testing procedure to estimate the wound volume at a plurality of times during wound treatment and determine healing progression based on changes in the wound volume during wound treatment.
• 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.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a block diagram of a wound therapy system including a therapy device coupled to a wound dressing via tubing, according to an exemplary embodiment.
• FIG. 2 is a block diagram illustrating the therapy device ofFIG. 1 in greater detail when the therapy device operates to draw a vacuum within a negative pressure circuit, according to an exemplary embodiment.
• FIG. 3A is a block diagram illustrating the therapy device ofFIG. 1 in greater detail when the therapy device operates to vent the negative pressure circuit, according to an exemplary embodiment.
• FIG. 3B is a block diagram illustrating the therapy device ofFIG. 1 in greater detail when the therapy device uses an orifice to vent the negative pressure circuit, according to an exemplary embodiment.
• FIG. 4 is a block diagram illustrating the therapy device ofFIG. 1 in greater detail when the therapy device operates to deliver instillation fluid to the wound dressing and/or a wound, according to an exemplary embodiment.
• FIG. 5 is a block diagram illustrating a controller of the therapy device ofFIG. 1 in greater detail, according to an exemplary embodiment.
• FIG. 6A is a graph illustrating a passive pressure testing procedure which can be performed by the therapy device ofFIG. 1, according to an exemplary embodiment.
• FIG. 6B is a graph illustrating an active pressure testing procedure which can be performed by the therapy device ofFIG. 1, according to an exemplary embodiment.
• FIG. 6C is a graph illustrating an uncontrolled pressure testing procedure with a variable leak rate which can be performed by the therapy device ofFIG. 1, according to an exemplary embodiment.
• FIG. 6D is a graph illustrating an uncontrolled pressure testing procedure with a constant leak rate which can be performed by the therapy device ofFIG. 1, according to an exemplary embodiment.
• FIG. 7A is a graph illustrating several pressure decay curves which can be generated and/or used by the therapy device ofFIG. 1 to relate measured pressure to wound volume, according to an exemplary embodiment.
• FIG. 7B is a graph illustrating an unassisted pressure decay curve generated using the passive pressure testing procedure ofFIG. 6A and an assisted pressure decay curve generated using the active pressure testing procedure ofFIG. 6B, according to an exemplary embodiment.
• FIG. 8 is a flowchart of a process for generating a pressure response model that relates dynamic pressure response parameters to wound volume, according to an exemplary embodiment.
• FIG. 9 is a flowchart of a process for estimating wound volume by applying a pressure stimulus to a negative pressure circuit and observing the dynamic pressure response, according to an exemplary embodiment.
• FIG. 10 is a flowchart of a process for monitoring healing progression over time based on a set of wound volume estimates, according to an exemplary embodiment.
• FIG. 11 is a graph illustrating wound volume and instillation fluid volume over time, according to an exemplary embodiment.
• FIG. 12 is a flowchart of a process for determining an amount of instillation fluid to deliver to a wound based on an estimated wound volume, according to an exemplary embodiment.
• FIG. 13 is a graph illustrating a wound therapy process including leak rate determination, wound volume determination, and fluid instillation stages, according to an exemplary embodiment.
DETAILED DESCRIPTIONOverview
• Referring generally to the FIGURES, a wound therapy system with fluid instillation and removal and components thereof are shown, according to various exemplary embodiments. The wound therapy system may include a therapy device and a wound dressing. The therapy device may include an instillation fluid canister, a removed fluid canister, a valve, a pneumatic pump, an instillation pump, and a controller. The wound dressing can be applied to a patient's skin surrounding a wound. The therapy device can be configured to deliver instillation fluid to the wound and provide negative pressure wound therapy (NPWT) by maintaining the wound at negative pressure. Components of the wound therapy device, the wound dressing, and/or the wound form a negative pressure circuit.
• The controller can be configured to operate the pneumatic pump, the instillation pump, the valve, and/or other controllable components of the therapy device. In some embodiments, the controller performs a pressure testing procedure by applying a pressure stimulus to the negative pressure circuit. For example, the controller may instruct the valve to close and operate the pneumatic pump to establish negative pressure within the negative pressure circuit. Once the negative pressure has been established, the controller may deactivate the pneumatic pump. The controller may cause the valve to open for a predetermined amount of time and then close after the predetermined amount of time has elapsed. In some embodiments, the controller operates the pneumatic pump while the valve is closed to mitigate air leakage into the negative pressure circuit. The controller may observe a dynamic pressure response of the negative pressure circuit to the pressure stimulus using pressure measurements recorded by a pressure sensor. The dynamic pressure response may be characterized by a variety of parameters including, for example, a depth of purge parameter, a rebound parameter, a delta parameter, and a leak rate parameter (described in greater detail below).
• The controller can estimate the volume of the wound based on the observed dynamic pressure response. For example, the controller can apply the observed parameters as inputs to a pressure model that defines a relationship between the observed parameters and the volume of the negative pressure circuit and/or the volume of the wound. The model may include a polynomial approximation model, a neural network model, or any other model that relates the observed parameters to the volume of the negative pressure circuit and/or the volume of the wound. In some embodiments, the pressure model is a pre-existing model stored in the controller by the manufacturer of the therapy device. In other embodiments, the controller can generate the pressure model on-site by performing a training procedure.
• The training procedure may be the same as the pressure testing procedure with the exception that the therapy device is connected to a training circuit having a known volume. For example, the wound dressing can be applied to a test device having a known volume rather than to a patient's skin surrounding a wound. The controller can apply the pressure stimulus to various training circuits having various known volumes and may observe the dynamic pressure response of each training circuit. Each of the known volumes may result in a different dynamic pressure response to the pressure stimulus. The controller can then associate the known volume of each training circuit with the corresponding dynamic pressure response. In some embodiments, the controller uses the dynamic pressure responses of the training circuits to generate the pressure model that defines a relationship between the observed parameters of the dynamic pressure response (e.g., depth of purge, rebound, delta, leak rate, etc.) and the volume of the training circuit. The pressure model can then be stored in the therapy device and used to estimate the volume of a wound, as previously described.
• In some embodiments, the controller is configured to execute the pressure testing procedure, observe the dynamic pressure response, and estimate the wound volume at a plurality of times during wound treatment. The controller can then determine healing progression based on changes in the wound volume during wound treatment. In some embodiments, the controller is configured to determine a volume of instillation fluid to deliver to the wound based on the estimated wound volume. The volume of instillation fluid to deliver may be a predetermined percentage of the volume of the wound (e.g., 20%, 50%, 80%, etc.). The controller can then operate the instillation pump to deliver the determined volume of instillation fluid to the wound. These and other features of the wound therapy system are described in detail below.
Wound Therapy System
• Referring now toFIGS. 1-4, a negative pressure wound therapy (NPWT)system100 is shown, according to an exemplary embodiment.NPWT system100 is shown to include atherapy device102 fluidly connected to a wound dressing112 viatubing108 and110. Wound dressing112 may be adhered or sealed to a patient'sskin116 surrounding awound114. Several examples ofwound dressings112 which can be used in combination withNPWT system100 are described in detail in U.S. Pat. No. 7,651,484 granted Jan. 26, 2010, U.S. Pat. No. 8,394,081 granted Mar. 12, 2013, and U.S. patent application Ser. No. 14/087,418 filed Nov. 22, 2013. The entire disclosure of each of these patents and patent applications is incorporated by reference herein.
• Therapy device102 can be configured to provide negative pressure wound therapy by reducing the pressure atwound114.Therapy device102 can draw a vacuum at wound114 (relative to atmospheric pressure) by removing wound exudate, air, and other fluids fromwound114. 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 fromwound114 may includeinstillation fluid105 previously delivered to wound114. Instillation fluid105 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 wound114 during wound treatment. Instillation fluid105 may be held in aninstillation fluid canister104 and controllably dispensed to wound114 viainstillation fluid tubing108. In some embodiments,instillation fluid canister104 is detachable fromtherapy device102 to allowcanister106 to be refilled and replaced as needed.
• Thefluids107 removed fromwound114 pass through removedfluid tubing110 and are collected in removedfluid canister106.Removed fluid canister106 may be a component oftherapy device102 configured to collect wound exudate andother fluids107 removed fromwound114. In some embodiments, removedfluid canister106 is detachable fromtherapy device102 to allowcanister106 to be emptied and replaced as needed. A lower portion ofcanister106 may be filled with wound exudate andother fluids107 removed fromwound114, whereas an upper portion ofcanister106 may be filled with air.Therapy device102 can be configured to draw a vacuum withincanister106 by pumping air out ofcanister106. The reduced pressure withincanister106 can be translated to wound dressing112 and wound114 viatubing110 such that wound dressing112 and wound114 are maintained at the same pressure ascanister106.
• Referring particularly toFIGS. 2-4, block diagrams illustratingtherapy device102 in greater detail are shown, according to an exemplary embodiment.Therapy device102 is shown to include apneumatic pump120, aninstillation pump122, avalve132, afilter128, and acontroller118.Pneumatic pump120 can be fluidly coupled to removed fluid canister106 (e.g., via conduit136) and can be configured to draw a vacuum withincanister106 by pumping air out ofcanister106. In some embodiments,pneumatic pump120 is configured to operate in both a forward direction and a reverse direction. For example,pneumatic pump120 can operate in the forward direction to pump air out ofcanister106 and decrease the pressure withincanister106.Pneumatic pump120 can operate in the reverse direction to pump air intocanister106 and increase the pressure withincanister106.Pneumatic pump120 can be controlled bycontroller118, described in greater detail below.
• Similarly,instillation pump122 can be fluidly coupled toinstillation fluid canister104 viatubing109 and fluidly coupled to wound dressing112 viatubing108.Instillation pump122 can be operated to deliverinstillation fluid105 to wound dressing112 and wound114 by pumpinginstillation fluid105 throughtubing109 andtubing108, as shown inFIG. 4.Instillation pump122 can be controlled bycontroller118, described in greater detail below.
• Filter128 can be positioned between removedfluid canister106 and pneumatic pump120 (e.g., along conduit136) such that the air pumped out ofcanister106 passes throughfilter128.Filter128 can be configured to prevent liquid or solid particles from enteringconduit136 and reachingpneumatic pump120.Filter128 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 offilter128.Pneumatic pump120 can be configured to provide sufficient airflow throughfilter128 that the pressure drop acrossfilter128 is not substantial (e.g., such that the pressure drop will not substantially interfere with the application of negative pressure to wound114 from therapy device102).
• In some embodiments,therapy device102 operates avalve132 to controllably vent the negative pressure circuit, as shown inFIG. 3A.Valve132 can be fluidly connected withpneumatic pump120 and filter128 viaconduit136. In some embodiments,valve132 is configured to control airflow betweenconduit136 and the environment aroundtherapy device102. For example,valve132 can be opened to allow airflow intoconduit136 viavent134 andconduit138, and closed to prevent airflow intoconduit136 viavent134 andconduit138.Valve132 can be opened and closed bycontroller118, described in greater detail below. Whenvalve132 is closed,pneumatic pump120 can draw a vacuum within a negative pressure circuit by causing airflow throughfilter128 in a first direction, as shown inFIG. 2. The negative pressure circuit may include any component ofsystem100 that can be maintained at a negative pressure when performing negative pressure wound therapy (e.g.,conduit136, removedfluid canister106,tubing110, wound dressing112, and/or wound114). For example, the negative pressure circuit may includeconduit136, removedfluid canister106,tubing110, wound dressing112, and/or wound114. Whenvalve132 is open, airflow from the environment aroundtherapy device102 may enterconduit136 viavent134 andconduit138 and fill the vacuum within the negative pressure circuit. The airflow fromconduit136 intocanister106 and other volumes within the negative pressure circuit may pass throughfilter128 in a second direction, opposite the first direction, as shown inFIG. 3A.
• In some embodiments,therapy device102 vents the negative pressure circuit via anorifice158, as shown inFIG. 3B.Orifice158 may be a small opening inconduit136 or any other component of the negative pressure circuit (e.g., removedfluid canister106,tubing110,tubing111, wound dressing112, etc.) and may allow air to leak into the negative pressure circuit at a known rate. In some embodiments,therapy device102 vents the negative pressure circuit viaorifice158 rather than operatingvalve132.Valve132 can be omitted fromtherapy device102 for any embodiment in which orifice158 is included. The rate at which air leaks into the negative pressure circuit viaorifice158 may be substantially constant or may vary as a function of the negative pressure, depending on the geometry oforifice158. For embodiments in which the leak rate viaorifice158 is variable,controller118 can use a stored relationship between negative pressure and leak rate to calculate the leak rate viaorifice158 based measurements of the negative pressure. Regardless of whether the leak rate viaorifice158 is substantially constant or variable, the leakage of air into the negative pressure circuit viaorifice158 can be used to generate a pressure decay curve for use in estimating the volume ofwound114, as described with reference toFIGS. 5-9.
• In some embodiments,therapy device102 includes a variety of sensors. For example,therapy device102 is shown to include apressure sensor130 configured to measure the pressure withincanister106 and/or the pressure at wound dressing112 or wound114. In some embodiments,therapy device102 includes apressure sensor113 configured to measure the pressure withintubing111.Tubing111 may be connected to wound dressing112 and may be dedicated to measuring the pressure at wound dressing112 or wound114 without having a secondary function such as channelinginstallation fluid105 or wound exudate. In various embodiments,tubing108,110, and111 may be physically separate tubes or separate lumens within a single tube that connectstherapy device102 to wound dressing112. Accordingly,tubing110 may be described as a negative pressure lumen that functions apply negative pressure wound dressing112 or wound114, whereastubing111 may be described as a sensing lumen configured to sense the pressure at wound dressing112 or wound114.Pressure sensors130 and113 can be located withintherapy device102, positioned at any location alongtubing108,110, and111, or located at wound dressing112 in various embodiments. Pressure measurements recorded bypressure sensors130 and/or113 can be communicated tocontroller118.Controller118 use the pressure measurements as inputs to various pressure testing operations and control operations performed by controller118 (described in greater detail with reference toFIGS. 5-12).
• Controller118 can be configured to operatepneumatic pump120,instillation pump122,valve132, and/or other controllable components oftherapy device102. In some embodiments,controller118 performs a pressure testing procedure by applying a pressure stimulus to the negative pressure circuit. For example,controller118 may instructvalve132 to close and operatepneumatic pump120 to establish negative pressure within the negative pressure circuit. Once the negative pressure has been established,controller118 may deactivatepneumatic pump120.Controller118 may causevalve132 to open for a predetermined amount of time and then close after the predetermined amount of time has elapsed.Controller118 may observe a dynamic pressure response of the negative pressure circuit to the pressure stimulus using pressure measurements recorded bypressure sensors130 and/or113. The dynamic pressure response may be characterized by a variety of parameters including, for example, a depth of purge parameter, a rebound parameter, a delta parameter, and a leak rate parameter (described in greater detail with reference toFIG. 5).
• Controller118 can estimate the volume ofwound114 based on the observed dynamic pressure response. For example,controller118 can apply the observed parameters as inputs to a pressure model that defines a relationship between the observed parameters and the volume of the negative pressure circuit and/or the volume ofwound114. The model may include a polynomial approximation model, a neural network model, or any other model that relates the observed parameters to the volume of the negative pressure circuit and/or the volume ofwound114. In some embodiments, the pressure model is a pre-existing model stored incontroller118 by the manufacturer oftherapy device102. In other embodiments,controller118 can generate the pressure model on-site by performing a training procedure.
• The training procedure may be the same as the pressure testing procedure with the exception thattherapy device102 is connected to a training circuit having a known volume. For example, wound dressing112 can be applied to a test device having a known volume rather than to a patient'sskin116 surroundingwound114.Controller118 can apply the pressure stimulus to various training circuits having various known volumes and may observe the dynamic pressure response of each training circuit. Each of the known volumes may result in a different dynamic pressure response to the pressure stimulus.Controller118 can then associate the known volume of each training circuit with the corresponding dynamic pressure response. In some embodiments,controller118 uses the dynamic pressure responses of the training circuits to generate the pressure model that defines a relationship between the observed parameters of the dynamic pressure response (e.g., depth of purge, rebound, delta, leak rate, etc.) and the volume of the training circuit. The pressure model can then be stored incontroller118 and used to estimate the volume of awound114, as previously described.
• In some embodiments,controller118 is configured to execute the pressure testing procedure, observe the dynamic pressure response, and estimate the wound volume at a plurality of times during wound treatment.Controller118 can then determine healing progression based on changes in the wound volume during wound treatment. In some embodiments,controller118 is configured to determine a volume ofinstillation fluid105 to deliver to wound114 based on the estimated wound volume. The volume ofinstillation fluid105 to deliver may be a predetermined percentage of the volume of wound114 (e.g., 20%, 50%, 80%, etc.).Controller118 can then operateinstillation pump122 to deliver the determined volume ofinstillation fluid105 to wound114. These and other features ofcontroller118 are described in greater detail with reference toFIGS. 5-12.
• In some embodiments,therapy device102 includes auser interface126.User interface126 may include one or more buttons, dials, sliders, keys, or other input devices configured to receive input from a user.User interface126 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 bypressure sensors130 and/or113 are presented to a user viauser interface126.User interface126 can also display alerts generated bycontroller118. For example,controller118 can generate a “no canister” alert ifcanister106 is not detected.
• In some embodiments,therapy device102 includes a data communications interface124 (e.g., a USB port, a wireless transceiver, etc.) configured to receive and transmit data. Communications interface124 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 interface124 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 interface124 can include a Wi-Fi transceiver for communicating via a wireless communications network or cellular or mobile phone communications transceivers.
Controller
• Referring now toFIG. 5, a blockdiagram illustrating controller118 in greater detail is shown, according to an exemplary embodiment.Controller118 is shown to include aprocessing circuit140 including aprocessor142 andmemory144.Processor142 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.Processor142 is configured to execute computer code or instructions stored inmemory144 or received from other computer readable media (e.g., CDROM, network storage, a remote server, etc.).
• Memory144 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.Memory144 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.Memory144 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.Memory144 may be communicably connected toprocessor142 viaprocessing circuit140 and may include computer code for executing (e.g., by processor142) one or more processes described herein. Whenprocessor142 executes instructions stored inmemory144,processor142 generally configures controller118 (and more particularly processing circuit140) to complete such activities.
• Controller118 is shown to include apump controller146 and avalve controller150.Pump controller146 can be configured to operatepumps120 and122 by generating and providing control signals to pumps120-122. The control signals provided to pumps120-122 can cause pumps120-122 to activate, deactivate, or achieve a variable capacity or speed (e.g., operate at half speed, operate at full speed, etc.). Similarly,valve controller150 can be configured to operatevalve132 by generating and providing control signals tovalve132. The control signals provided tovalve132 can causevalve132 to open, close, or achieve a specified intermediate position (e.g., one-third open, half open, etc.). In some embodiments,pump controller146 andvalve controller150 are used by other components of controller118 (e.g.,testing procedure controller148, woundvolume estimator156, etc.) to operate pumps120-122 andvalve132 when carrying out the processes described herein.
• In some embodiments,pump controller146 uses input from a canister sensor configured to detect whether removedfluid canister106 is present.Pump controller146 can be configured to activatepneumatic pump120 only when removedfluid canister106 is present. For example,pump controller146 can check whethercanister106 is present and can activatepneumatic pump120 in response to a determination that canister106 is present. However, ifcanister106 is not present,pump controller146 may preventpneumatic pump120 from activating. Similarly,pump controller146 can be configured to activateinstillation pump122 only when instillationfluid canister104 is present. For example,pump controller146 can check whethercanister104 is present and can activateinstillation pump122 in response to a determination that canister104 is present. However, ifcanister104 is not present,pump controller146 may preventinstillation pump122 from activating.
• Controller118 is shown to include apressure monitor152. Pressure monitor152 can be configured to monitor the pressure within removedfluid canister106 and/or the pressure within wound dressing112 or wound114 using feedback frompressure sensors130 and/or113. For example,pressure sensors130 and/or113 may provide pressure measurements to pressure monitor152. Pressure monitor152 can use the pressure measurements to determine the pressure withincanister106 and/or the pressure within wound dressing112 or wound114 in real-time. Pressure monitor152 can provide the pressure value tomodel generator154,pump controller146,testing procedure controller148, and/orvalve controller150 for use as an input to control processes performed by such components.
• Referring now toFIGS. 5 and 6A-6C,controller118 is shown to include atesting procedure controller148.Testing procedure controller148 can be configured to execute a pressure testing procedure to invoke and observe a dynamic pressure response. Iftherapy device102 is connected to a wound dressing112 applied to a patient'sskin116 over awound114,testing procedure controller148 can observe the dynamic pressure response of a negative pressure circuit that includesconduit136, removedfluid canister106,tubing110, wound dressing112, and/or wound114 (which may have an unknown volume). Iftherapy device102 is connected to a wound dressing112 applied to a training device having a known volume,testing procedure controller148 can observe the dynamic pressure response of a training circuit that includesconduit136, removedfluid canister106,tubing110, wound dressing112, and/or the training device.
• Referring particularly toFIG. 6A, agraph200 illustrating a passive pressure testing procedure performed bytesting procedure controller148 is shown, according to an exemplary embodiment.Testing procedure controller148 can be configured to operatepneumatic pump120 to establish negative pressure within the negative pressure circuit and/or the training circuit. The negative pressure may be defined as the difference between the atmospheric pressure surroundingtherapy device102 and the pressure within the negative pressure circuit and/or the training circuit (i.e., the amount by which atmospheric pressure exceeds the pressure within the negative pressure circuit and/or the training circuit). For example, at time t₀, the negative pressure is shown having a value of P₀(e.g., zero mmHg), which indicates that the pressure within the negative pressure circuit and/or the training circuit is equal to atmospheric pressure aroundtherapy device102.
• At time t₀,testing procedure controller148 begins operatingpneumatic pump120 to reduce the pressure within the negative pressure circuit and/or the training circuit. The negative pressure continues to decrease until it reaches a negative pressure value of P₈mmHg below atmospheric pressure (e.g., 125 mmHg) at time t₁. Between time t₁and time t₂,testing procedure controller148 maintains the negative pressure at the value of P₈by operatingpneumatic pump120 as needed to remove air from the negative pressure circuit and/or the training circuit.Testing procedure controller148 may then apply a pressure stimulus to the negative pressure circuit and/or the training circuit after the negative pressure has been established within the negative pressure circuit and/or the training circuit.
• At time t₂,testing procedure controller148 deactivatespneumatic pump120. Beginning at time t₂, the magnitude of the negative pressure within the negative pressure circuit and/or the training circuit may decrease due to leakage of air into the negative pressure circuit and/or the training circuit whilevalve132 is closed. The rate at which the negative pressure decreases whilevalve132 is closed is defined by the slope ofline202 between time t₂and time t₃.Testing procedure controller148 may determine the slope ofline202 between time t₂and time t₃and may store the slope as the value of the leak rate parameter. The leak rate parameter may be one of the parameters that characterizes the dynamic pressure response of the negative pressure circuit and/or the training circuit.
• At time t₃,testing procedure controller148 applies a pressure stimulus to the negative pressure circuit and/or the training circuit. Applying the pressure stimulus may include operatingvalve132 to controllably vent the negative pressure circuit and/or the training circuit. For example,testing procedure controller148 may causevalve132 to open at time t₃to allow airflow into the negative pressure circuit and/or the training circuit.Testing procedure controller148 may keepvalve132 open for a predetermined amount of time (i.e., from time t₃to time t₄) and may closevalve132 after closing the valve after the predetermined amount of time has elapsed (i.e., at time t₄).
• At time t₄,testing procedure controller148 may observe the dynamic pressure response of the negative pressure circuit and/or the training circuit to the pressure stimulus. The dynamic pressure response may be characterized by several additional parameters including a depth of purge parameter, a rebound parameter, and a delta parameter. The depth of purge parameter may be defined as the difference between a measured value of the negative pressure P₇beforevalve132 is opened and a measured value of the negative pressure P₃whilevalve132 is open (i.e., depth of purge=P₇−P₃). The rebound parameter may be defined as the difference between a measured value of the negative pressure P₆aftervalve132 is closed and a measured value of the negative pressure P₃whilevalve132 is open (i.e., rebound=P₆−P₃). The delta parameter may be defined as the difference between a measured value of the negative pressure P₇beforevalve132 is opened and a measured value of the negative pressure P₆aftervalve132 is closed (i.e., delta=P₇−P₆).
• In some embodiments,testing procedure controller148 applies the pressure stimulus one or more additional times until the negative pressure reaches a threshold value P₁whenvalve132 is closed. Between each application of the pressure stimulus,testing procedure controller148 may wait for another predetermined amount of time (i.e., from time t₄to time t₅and from time t₆to time t₇). For example,testing procedure controller148 may wait for a predetermined amount of time from time t₄to time t₅and may apply the pressure stimulus again at time t₅.Testing procedure controller148 may causevalve132 to open at time t₅to allow airflow into the negative pressure circuit and/or the training circuit.Testing procedure controller148 may keepvalve132 open for a predetermined amount of time (i.e., from time t₅to time t₆) and may closevalve132 after closing the valve after the predetermined amount of time has elapsed (i.e., at time t₆). At time t₆,testing procedure controller148 may record values of the depth of purge parameter (i.e., depth of purge=P₅−P₁), the rebound parameter (i.e., rebound=P₄−P₁), and the delta parameter (i.e., delta=P₅−P₄) in response to the second application of the pressure stimulus. This process can be repeated until the value of the negative pressure within the negative pressure circuit and/or the training circuit reaches the threshold pressure value P₁at time t₉.
• Referring particularly toFIG. 6B, agraph210 illustrating an active testing procedure performed bytesting procedure controller148 is shown, according to an exemplary embodiment.Testing procedure controller148 can be configured to operatepneumatic pump120 to establish negative pressure within the negative pressure circuit and/or the training circuit. The negative pressure may be defined as the difference between the atmospheric pressure surroundingtherapy device102 and the pressure within the negative pressure circuit and/or the training circuit (i.e., the amount by which atmospheric pressure exceeds the pressure within the negative pressure circuit and/or the training circuit). For example, at time t₀, the negative pressure is shown having a value of P₀(e.g., zero mmHg), which indicates that the pressure within the negative pressure circuit and/or the training circuit is equal to atmospheric pressure aroundtherapy device102.
• The active testing procedure illustrated inFIG. 6B may be substantially similar to the passive testing procedure illustrated inFIG. 6A. However, in the active testing procedure,controller148 can be configured to operatepneumatic pump120 using brief controlled activations ofpneumatic pump120 whilevalve132 is closed (e.g., between times t₄and t₅, between times t₆and t₇, and between times t₈and t₉) to compensate for a high leak rate of air into the negative pressure circuit and/or the training circuit. Ingraph210,line212 represents the pressure within the negative pressure circuit and/or the training circuit as a function of time. The actual leak rate of air into the negative pressure circuit and/or the training circuit whilevalve132 is closed is indicated by the slope ofline segments216, whereas the slope ofline214 represents the average or assisted leak rate between times t₄and t₅. The brief controlled activations ofpneumatic pump120 remove some of the air from the negative pressure circuit and/or the training circuit between times t₄and t₅(causing the negative pressure to increase with each controlled activation) such that the average or assisted leak rate is equal to
• $\frac{P_6-P_5}{t_5-t_4}.$
• Similar negative pressure adjustments can be made between times t₆and t₇and between times t₈and t₉. In this way, the influx of air into the negative pressure circuit and/or training can be mitigated to compensate for a high actual leak rate whilevalve132 is closed.
• Referring particularly toFIGS. 6C-6D,graphs220 and230 illustrating an uncontrolled testing procedure performed bytesting procedure controller148 is shown, according to an exemplary embodiment. Unlike the passive testing procedure and active testing procedure described with reference toFIGS. 6A and 6B, the uncontrolled testing procedure does not make use ofvalve132 and can be performed for embodiments in whichtherapy device102 includesorifice158 in place ofvalve132.Graph220 illustrates the uncontrolled testing procedure whenorifice158 leaks air into the negative pressure circuit and/or training circuit at a variable leak rate, whereasgraph220 illustrates the uncontrolled testing procedure whenorifice158 leaks air into the negative pressure circuit and/or training circuit at a substantially constant leak rate.
• In both uncontrolled testing procedures, at time t₀,testing procedure controller148 begins operatingpneumatic pump120 to reduce the pressure within the negative pressure circuit and/or the training circuit. The negative pressure continues to decrease until it reaches a negative pressure value of P₂mmHg below atmospheric pressure (e.g., 125 mmHg) at time t₁.
• At time t₁,testing procedure controller148 deactivatespneumatic pump120. Beginning at time t₁, the magnitude of the negative pressure within the negative pressure circuit and/or the training circuit may decrease due to leakage of air into the negative pressure circuit and/or the training circuit viaorifice158. The rate at which the negative pressure decreases is defined by the slope ofline222 between time t₁and time t₂. Ingraph220, leakage of air into the negative pressure circuit and/or training circuit viaorifice158 occurs more quickly near time t₁and more slowly near time t₂, as shown by the slope ofline222 becoming closer to zero as time elapses between t₁and t₂. Ingraph230, leakage of air into the negative pressure circuit and/or training circuit viaorifice158 occurs at a substantially constant rate, as shown by the substantiallylinear line232. In either scenario,testing procedure controller148 may determine the slope ofline222 at one or more times between time t₁and time t₂and may store the slope as the value of the leak rate parameter. Alternatively, the leak rate parameter can be defined as the amount of time required for the negative pressure to drop from P₂to P₁and can be calculated by subtracting t₁from t₂(i.e., t₂−t₁). The leak rate parameter may be one of the parameters that characterizes the dynamic pressure response of the negative pressure circuit and/or the training circuit.
• Testing procedure controller148 can be configured to execute the passive testing procedure, the active testing procedure, and/or the uncontrolled testing procedure in various embodiments. The passive testing procedure may be suitable under most conditions and may be the primary or default testing procedure used bytesting procedure controller148. However, the active testing procedure may be suitable in the presence of a high leak rate and may be used bytesting procedure controller148 in response to a determination that the actual leak rate exceeds a predetermined leak rate threshold. The uncontrolled testing procedure may be suitable for embodiments in whichvalve132 is replaced withorifice158.
• Leak rate can be determined in a variety of ways. In some embodiments, leak rate is determined by operatingpneumatic pump120 to achieve a predetermined negative pressure within the negative pressure circuit and measuring the pressure decay over time. In some embodiments, leak rate is determined based on the effort ofpneumatic pump120 or power consumed bypneumatic pump120. For example,pump controller146 can be configured to perform brief controlled activations ofpneumatic pump120 to maintain the negative pressure at a setpoint or prevent the negative pressure from dropping at a rate that exceeds a predetermined leak rate threshold, as previously described. The number or frequency of these brief controlled activations ofpneumatic pump120 depends on the leak rate and can be used to determine the leak rate. Similarly, the power consumed bypneumatic pump120 to perform these brief controlled activations depends on the leak rate and can be used to determine the leak rate. For example,controller118 can be configured to record the number of brief controlled activations ofpneumatic pump120 within a given time period, measure a frequency or interval of the brief controlled activations, measure a duty cycle of pneumatic pump120 (e.g., a percentage of timepneumatic pump120 is active), or measure an amount of power consumed bypneumatic pump120 to perform the brief controlled activations. Any of these metrics may characterize pump effort and can be stored as a pump effort parameter.Controller118 can use a stored equation or predetermined relationship to calculate leak rate as a function of the pump effort.
• Referring again toFIG. 5,controller118 is shown to include amodel generator154.Model generator154 can be configured to generate a model that defines a relationship between the parameters of the dynamic pressure response and the volume ofwound114. To generate the model,model generator154 can causetesting procedure controller148 to run the pressure testing procedure outlined above for several different training circuits having several different known volumes (e.g., 50 cc, 100 cc, 200 cc, 300 cc, etc.). When the pressure testing procedure is performed on a training circuit having a known volume, the pressure testing procedure may be referred to as a training procedure. Each performance of the training procedure may include applying the pressure stimulus to a training circuit having a known volume, observing the dynamic pressure response of the training circuit to the pressure stimulus, and associating the known volume with the dynamic pressure response of the training circuit.
• In some embodiments,model generator154 records the values of the parameters of the dynamic pressure response (i.e., leak rate, depth of purge, rebound, delta, etc.) for each known volume and associates those values with the known volume. The values of the parameters and the known volume form a set of training data which can be used to construct a model. The values of the parameters form a set of model input training data, whereas the known volumes form a set of model output training data.Model generator154 can use any of a variety of model generation techniques to construct a model (i.e., a mathematical model) that relates the values of the parameters to the corresponding volume in the set of training data.
• In some embodiments,model generator154 creates a polynomial approximation model to relate the values of the parameters to the corresponding volume. To generate a polynomial approximation model,model generator154 can perform a curve fitting process such as polynomial regression using any of a variety of regression techniques. Examples of regression techniques which can be used bymodel generator154 include least squares, ordinary least squares, linear least squares, partial least squares, total least squares, generalized least squares, weighted least squares non-linear least squares, non-negative least squares, iteratively reweighted least squares, ridge regression, least absolute deviations, Bayesian linear regression, Bayesian multivariate linear regression, etc.
• In other embodiments,model generator154 creates a neural network model to relate the values of the parameters to the corresponding volume. To generate a neural network model,model generator154 can perform a machine learning process. Examples of machine learning techniques which can be used bymodel generator154 include decision tree learning, association rule learning, artificial neural networks, deep learning, inductive logic programming, support vector machines, clustering, Bayesian networks, reinforcement learning, representation learning, similarity and metric learning, sparse dictionary learning, genetic algorithms, rule-based machine learning, etc.
• Referring now toFIG. 7A, agraph250 illustrating several pressure decay curves252,254,256, and258 are shown, according to an exemplary embodiment. Each of pressure decay curves252-258 corresponds to a known volume and represents the pressure within the negative pressure circuit and/or the training circuit as a function of time for the corresponding volume. For example,pressure decay curve252 corresponds to a volume of 300 cc,pressure decay curve254 corresponds to a volume of 200 cc,pressure decay curve256 corresponds to a volume of 100 cc,pressure decay curve258 corresponds to a volume of 50 cc. Each of pressure decay curves252-258 may be created bymodel generator154 using any of the modeling techniques described above. For example, pressure decay curves252-258 can be created by running the pressure testing procedure for each known volume and plotting the pressure decay over time for each known volume.
• In some embodiments,controller118 uses pressure decay curves252-258 to translate a measured pressure value into a corresponding volume when estimating the volume ofwound114. For example,controller118 can measure the pressure of the negative pressure circuit and identify a time at which the pressure was measured.Controller118 can interpolate between pressure decay curves252-258 to determine an interpolated pressure value that corresponds to the measured pressure and time pair. For example, at time t₁,controller118 may observe a pressure value of P₁. The combination of time t₁and pressure P₁defines apoint260 ingraph250.Point260 lies approximately halfway betweenpressure decay curve252 andpressure decay curve254.Controller118 can interpolate between pressure decay curves252 and254 to estimate that the volume of the negative pressure circuit is approximately halfway between the known volumes corresponding to pressure decay curves252 and254 (i.e., approximately 250 cc). In other embodiments,controller118 estimates the volume ofwound114 by applying observed parameters of a dynamic pressure response as inputs to a pressure model.
• Referring now toFIG. 7B, agraph260 illustrating an unassistedpressure decay curve264 and an assistedpressure decay curve262 is shown, according to an exemplary embodiment. Ingraph260, both unassistedpressure decay curve264 and assistedpressure decay curve262 correspond to the same volume of the negative pressure circuit and/or training circuit. Unassistedpressure decay curve264 illustrates the pressure decay during the passive testing procedure shown inFIG. 6A (i.e., whenpneumatic pump120 is not operated to compensate for a high leak rate). Conversely, assistedpressure decay curve262 illustrates the pressure decay during the active testing procedure (i.e., whenpneumatic pump120 is operated to compensate for a high leak rate). As discussed with reference toFIG. 6B, operatingpneumatic pump120 during the active testing procedure mitigates the pressure decay and therefore results in a more gradual assistedpressure decay curve262 relative to unassistedpressure decay curve264.
• Referring again toFIG. 5,controller118 is shown to include awound volume estimator156.Wound volume estimator156 can be configured to estimate the volume ofwound114 based on pressure measurements collected bypressure sensors130 and/or113. In some embodiments, woundvolume estimator156 estimates the volume ofwound114 by performing a pressure testing procedure. The pressure testing procedure may include applying a pressure stimulus to the negative pressure circuit and observing the dynamic pressure response of the negative pressure circuit to the pressure stimulus. As described above, the negative pressure circuit may include any component ofsystem100 that can be maintained at a negative pressure when performing negative pressure wound therapy (e.g.,conduit136, removedfluid canister106,tubing110, wound dressing112, and/or wound114).
• To perform the pressure testing procedure, woundvolume estimator156 may instructvalve132 to close and operatepneumatic pump120 to establish negative pressure within the negative pressure circuit. Once the negative pressure has been established, woundvolume estimator156 may deactivatepneumatic pump120.Wound volume estimator156 may causevalve132 to open for a predetermined amount of time and then close after the predetermined amount of time has elapsed.Wound volume estimator156 may observe a dynamic pressure response of the negative pressure circuit to the pressure stimulus using pressure measurements recorded bypressure sensors130 and/or113. The dynamic pressure response may be characterized by a variety of parameters including, for example, a depth of purge parameter, a rebound parameter, a delta parameter, and a leak rate parameter, as previously described.
• Wound volume estimator156 can estimate the volume ofwound114 based on the observed dynamic pressure response. For example, woundvolume estimator156 can apply the observed parameters as inputs to a pressure model that defines a relationship between the observed parameters and the volume of the negative pressure circuit and/or the volume ofwound114. In some embodiments, the pressure model is the model created by model generator154 (e.g., by performing the training procedure based on training data collected using the training circuits). The model may include a polynomial approximation model, a neural network model, or any other model that relates the observed parameters to the volume of the negative pressure circuit and/or the volume ofwound114. In other embodiments, the pressure model is a pre-existing model stored inmemory144 by the manufacturer oftherapy device102.
• In some embodiments, woundvolume estimator156 is configured to execute the pressure testing procedure, observe the dynamic pressure response, and estimate the wound volume at a plurality of times during wound treatment.Wound volume estimator156 can then determine healing progression based on changes in the wound volume during wound treatment. In some embodiments, woundvolume estimator156 is configured to determine a volume ofinstillation fluid105 to deliver to wound114 based on the estimated wound volume. The volume ofinstillation fluid105 to deliver may be a predetermined percentage of the volume of wound114 (e.g., 20%, 50%, 80%, etc.).Wound volume estimator156 can then operateinstillation pump122 to deliver the determined volume ofinstillation fluid105 to wound114.
Flow Diagrams
• Referring now toFIG. 8, a flowchart of aprocess300 for generating a pressure model is shown, according to an exemplary embodiment.Process300 can be performed by one or more components oftherapy device102 to create a model that characterizes the dynamic pressure response of a training circuit and/or negative pressure circuit. For example,process300 can be performed bycontroller118,pneumatic pump120,valve132, and/orpressure sensors130 and/or113. In some embodiments,process300 is executed bytesting procedure controller148 andmodel generator154.
• Process300 is shown to include applying a pressure stimulus to a training circuit having a known volume (step302). The training circuit may include one or more components of therapy device102 (e.g.,conduit136, removedfluid canister106, etc.) and/or other components of system100 (e.g.,tubing110, wound dressing112). Under wound treatment conditions, wound dressing112 would normally be applied to a patient'sskin116 surrounding awound114. However, the training circuit may replace wound114 with a training device having a known volume. Step302 may include instructingvalve132 to close and operatingpneumatic pump120 to establish negative pressure within the training circuit. Once the negative pressure has been established,pneumatic pump120 may be deactivated. Step302 may include causingvalve132 to open for a predetermined amount of time and then closingvalve132 after the predetermined amount of time has elapsed.
• Process300 is shown to include observing the dynamic pressure response of the training circuit to the pressure stimulus (step304) and associating the known volume of the training circuit with the dynamic pressure response (step306). Step304 may include monitoring the pressure of the training circuit over time using pressure measurements recorded bypressure sensors130 and/or113. The dynamic pressure response may be characterized by a variety of parameters including, for example, a depth of purge parameter, a rebound parameter, a delta parameter, and a leak rate parameter, as previously described. Step306 may include storing the values of the parameters of the dynamic pressure response as input training data and storing the known volume of the training circuit as output training data that corresponds to the input training data.
• Process300 is shown to include determining whether all volumes have been tested (step308). If not all volumes have been tested (i.e., the result ofstep308 is “no”), the training device to whichtherapy device102 is connected can be replaced with a different training device having a different known volume. Steps302-306 can then be repeated to apply the pressure stimulus to apply the pressure stimulus and observe the dynamic pressure response of the training circuit for each known volume. Each set of dynamic pressure response parameters can be stored as input training data and each set and the corresponding known volume can be stored as output training data.
• Once all volume have been tested (i.e., the result ofstep308 is “yes”),process300 may proceed to generating a pressure model (step310). Step310 may include using any of a variety of model generation techniques to construct a model (i.e., a mathematical model) that relates the values of the dynamic pressure response parameters to the corresponding volume in the set of training data.
• In some embodiments, the model generated instep310 is a polynomial approximation model. Step310 may include performing a curve fitting process such as polynomial regression using any of a variety of regression techniques. Examples of regression techniques which can be used instep310 include least squares, ordinary least squares, linear least squares, partial least squares, total least squares, generalized least squares, weighted least squares non-linear least squares, non-negative least squares, iteratively reweighted least squares, ridge regression, least absolute deviations, Bayesian linear regression, Bayesian multivariate linear regression, etc.
• In some embodiments, the model generated instep310 is a neural network model. Step310 may include using any of a variety of machine learning techniques to generate a neural network model that relates the values of the dynamic pressure response parameters to the corresponding volume in the set of training data. Examples of machine learning techniques which can be used instep310 include decision tree learning, association rule learning, artificial neural networks, deep learning, inductive logic programming, support vector machines, clustering, Bayesian networks, reinforcement learning, representation learning, similarity and metric learning, sparse dictionary learning, genetic algorithms, rule-based machine learning, etc. The pressure model can then be stored for use in estimating the volume ofwound114.
• Referring now toFIG. 9, a flowchart of aprocess400 for estimating the volume of a wound is shown, according to an exemplary embodiment.Process400 can be performed by one or more components oftherapy device102 estimate the volume ofwound114. For example,process400 can be performed bycontroller118,pneumatic pump120,valve132, and/orpressure sensors130 and/or113. In some embodiments,process400 is executed bytesting procedure controller148 and woundvolume estimator156.
• Process400 is shown to include applying a pressure stimulus to a negative pressure circuit having an unknown volume (step402). The negative pressure circuit may include one or more components of therapy device102 (e.g.,conduit136, removedfluid canister106, etc.) and/or other components of system100 (e.g.,tubing110, wound dressing112, wound114). Under wound treatment conditions, wound dressing112 may be applied to a patient'sskin116 surroundingwound114. Accordingly, the volume ofwound114 forms part of the negative pressure circuit. Step402 may include instructingvalve132 to close and operatingpneumatic pump120 to establish negative pressure within the negative pressure circuit. Once the negative pressure has been established,pneumatic pump120 may be deactivated. Step402 may include causingvalve132 to open for a predetermined amount of time and then closingvalve132 after the predetermined amount of time has elapsed. In some embodiments,step402 includes executing the passive testing procedure and/or the active testing procedure, as described with reference toFIGS. 6A-6B.
• Process400 is shown to include observing the dynamic pressure response of the negative pressure circuit to the pressure stimulus (step404) and determining values for parameters that characterize the dynamic pressure response (step406). Step404 may include monitoring the pressure of the negative pressure circuit over time using pressure measurements recorded bypressure sensors130 and/or113. The dynamic pressure response may be characterized by a variety of parameters including, for example, a depth of purge parameter, a rebound parameter, a delta parameter, and a leak rate parameter, as previously described. Step406 may include storing the values of the parameters of the dynamic pressure response.
• Process400 is shown to include applying the values of the parameters as inputs to a pressure response model that defines a wound volume as a function of the parameters (step408). In some embodiments, the pressure response model is the model created by performing process300 (e.g., by performing a regression process or machine learning process using training data collected using the training circuits). The model may include a polynomial approximation model, a neural network model, or any other model that relates the observed parameters to the volume of the negative pressure circuit and/or the volume ofwound114.
• Process400 is shown to include estimating the volume of the wound based on an output of the model (step410). In some embodiments, the output of the pressure response model is the estimated volume ofwound114. Accordingly, the output of the pressure response model can be used as the estimated wound volume. In other embodiments, the output of the pressure response model is the estimated volume of the negative pressure circuit. If the output of the pressure response model is the estimated volume of the negative pressure circuit, step410 may include subtracting known volumes of other components of the negative pressure circuit to isolate the estimated volume ofwound114. For example, step410 may include subtracting the known volumes ofconduit136, removedfluid canister106,tubing110, and/or wound dressing112 such that the only volume remaining is the volume ofwound114.
• In some embodiments, the volume of removedfluid canister106 that forms part of the negative pressure circuit is limited to the volume of the air withincanister106. The volume of the air withincanister106 may vary based on the level of removedfluid107 withincanister106. In some embodiments, removedfluid canister106 includes a sensor (e.g., a level sensor, a weight sensor, etc.) that operates to record the level of removedfluid107 withincanister106. The observed level of removed fluid107 can then be used to estimate the air volume withincanister106. In other embodiments, the volume of air withincanister106 can be estimated by performing a dead-space detection process. An example of a dead-space detection process which can be used to estimate the volume of air withincanister106 is described in detail in U.S. Provisional Patent Application No. 62/577,579 filed Oct. 26, 2017, the entire disclosure of which is incorporated by reference herein.
• Referring now toFIG. 10, a flowchart of aprocess500 for monitoring healing progression over time is shown, according to an exemplary embodiment.Process500 can be performed by one or more components oftherapy device102 to assess healing progression based on the volume ofwound114. For example,process500 can be performed bycontroller118,pneumatic pump120,valve132, and/orpressure sensors130 and/or113.
• Process500 is shown to include executing a pressure testing procedure to estimate wound volume at a plurality of times during wound treatment (step502). Step502 may include performingprocess400 multiple times during wound treatment (e.g., once per day). Eachtime process400 is performed, the volume ofwound114 may be estimated. Each estimate of the wound volume can be stored along with the time at which the estimate was obtained. The pairs of time and estimated wound volume can be stored as data points within the memory oftherapy device102 and/or presented to a user as an output of therapy device102 (e.g., viacommunications interface124 or user interface126). In some embodiments, the estimated wound volume can be plotted as a function of time, as shown inFIG. 11.
• Process500 is shown to include determining healing progression based on changes in the wound volume during wound treatment (step504). Step504 may include comparing a current estimate of the wound volume to one or more previous estimates of the wound volume to identify a change in the wound volume. In some embodiments,step504 includes determining a rate at which wound114 is healing based on the changes in the wound volume over time. In some embodiments,step504 includes extrapolating or predicting a time at which wound114 will be fully healed based on a series of wound volume estimates. For example, step504 may include predicting a time at which the estimated wound volume will reach zero (or another threshold value) based on the series of wound volume estimates obtained instep502.
• Referring now toFIGS. 11-12, agraph600 andflowchart700 illustrating an application of the wound volume estimates are shown, according to an exemplary embodiment.Controller118 can use the estimated wound volume to calculate a volume ofinstillation fluid105 to deliver to wound114 (step702). In some embodiments,controller118 calculates the volume ofinstillation fluid105 to deliver to wound114 by multiplying the estimated wound volume by a fluid instillation factor. The fluid instillation factor may be less than one (i.e., between zero and one) such that the calculated volume ofinstillation fluid105 is less than the volume ofwound114. In some embodiments, the fluid instillation factor is between approximately 0.2 and approximately 0.8. However, it is contemplated that the fluid instillation factor can have any value in various alternative embodiments.
• Ingraph600,line602 represents the estimated volume ofwound114 as a function of time, whereasline604 represents the calculated volume ofinstillation fluid105 to deliver to wound114 over time. At time t₁, the estimated volume ofwound114 is V₄. The estimated wound volume V₄at time t₁can be multiplied by the fluid instillation factor F (e.g., F=0.8) to calculate the volume of instillation fluid105 V₃to deliver to wound114 at time t₁(i.e., V₄*F=V₃). Aswound114 heals, the estimated volume ofwound114 decreases and reaches a value of V₂at time t₂. The estimated wound volume V₂at time t₂can be multiplied by the fluid instillation factor F to calculate the volume of instillation fluid105 V₁to deliver to wound114 at time t₂(i.e., V₂*F=V₁).
• Controller118 can then operate a pump to deliver the calculated volume ofinstillation fluid105 to wound114 (step704). Step704 can includeoperating instillation pump122 to drawinstillation fluid105 frominstillation fluid canister104 and deliverinstillation fluid105 to wound114 viatubing109 and108. In some embodiments, the calculated volume ofinstillation fluid105 is also used to control the operation ofpneumatic pump120. For example,controller118 can operatepneumatic pump120 to remove the volume ofinstillation fluid105 fromwound114 viatubing110. The amount of time thatpneumatic pump120 operates may be a function of the volume ofinstillation fluid105 that was delivered to wound114.
Wound Therapy Graph
• Referring now toFIG. 13, agraph800 illustrating several stages of a wound therapy process is shown, according to an exemplary embodiment. The wound therapy process illustrated inFIG. 13 can be performed by one or more components oftherapy device102 as previously described.Line802 represents the negative pressure within the negative pressure circuit at each stage of the wound therapy process.
• At time t₀,therapy device102 begins operatingpneumatic pump120 to reduce the negative pressure within the negative pressure circuit during an initial draw downstage804 that occurs between time t₀and t₁. At time t₁, the negative pressure within the negative pressure circuit reaches approximately 125 mmHg below atmospheric pressure andpneumatic pump120 is deactivated.
• Between times t₁and t₂, negative pressure within the negative pressure circuit is monitored using measurements frompressure sensors130 and/or113 during aseal check stage806. A substantial change in the pressure between times t₁and t₂may indicate that the seal between wound dressing112 and the patient's skin is not airtight whereas a substantially constant pressure between times t₁and t₂may indicate that wound dressing112 is properly sealed to the patient's skin.
• At time t₂,pneumatic pump120 is activated until the negative pressure within the negative pressure circuit is reduced to approximately 200 mmHg below atmospheric pressure. Upon reaching a negative pressure of 200 mmHg,pneumatic pump120 is deactivated and a woundvolume determination stage808 is initiated.Pneumatic pump120 may be intermittently activated duringstage808 to maintain the negative pressure at approximately 200 mmHg and compensate for any leakage of air into the negative pressure circuit.
• At time t₃,pneumatic pump120 is deactivated and aleak determination stage810 begins. Between times t₃and t₄, the negative pressure within the negative pressure circuit is monitored to determine a rate at which air leaks into the negative pressure circuit. At time t₄,pneumatic pump120 is reactivated to reduce the negative pressure back to approximately 200 mmHgPneumatic pump120 may be intermittently activated between time t₄and t₅to maintain the negative pressure at approximately 200 mmHg and compensate for any leakage of air into the negative pressure circuit.
• At time t₅,pneumatic pump120 is deactivated and a woundvolume determination stage812 begins. During woundvolume determination stage812,therapy device102 may perform one or more of the pressure testing procedures described with reference toFIGS. 6A-6D. The time ranges shown ingraphs200,210,220, and230 may occur entirely between times t₅and t₆ingraph800.
• At time t₆,pneumatic pump120 is activated and the negative pressure is reduced to approximately 125 mmHg below atmospheric pressure during a draw down forinstillation stage814. Upon reaching approximately 125 mmHg of negative pressure at time t₇,pneumatic pump120 is deactivated.Pneumatic pump120 may be intermittently activated between times t₇and t₈to maintain the negative pressure at approximately 125 mmHg and compensate for any leakage of air into the negative pressure circuit. Between times t₇and t₈,instillation fluid105 may be delivered to wound114.
Configuration of Exemplary Embodiments
• 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.
• Although the figures show a specific order of method steps, the order of the steps may differ from what is depicted. Also two or more steps can be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.

Claims (79)

1. A wound therapy system comprising:

a negative pressure circuit configured to apply negative pressure to a wound;

a pump fluidly coupled to the negative pressure circuit and operable to control the negative pressure within the negative pressure circuit;

a pressure sensor configured to measure the negative pressure within the negative pressure circuit or at the wound; and

a controller communicably coupled to the pump and the pressure sensor, the controller configured to:

execute a pressure testing procedure comprising applying a pressure stimulus to the negative pressure circuit;

observe a dynamic pressure response of the negative pressure circuit to the pressure stimulus using pressure measurements recorded by the pressure sensor; and

estimate a wound volume of the wound based on the dynamic pressure response.

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7. The wound therapy system ofclaim 1, wherein the testing procedure comprises:

operating the pump to establish the negative pressure within the negative pressure circuit; and

applying the pressure stimulus after the negative pressure has been established within the negative pressure circuit.

8. The wound therapy system ofclaim 1, further comprising a valve coupled to the negative pressure circuit and operable to controllably vent the negative pressure circuit.

9. The wound therapy system ofclaim 8, wherein applying the pressure stimulus comprises:

opening the valve to allow airflow into the negative pressure circuit for a predetermined amount of time; and

closing the valve after the predetermined amount of time has elapsed.

10. The wound therapy system ofclaim 9, wherein applying the pressure stimulus further comprises:

waiting for another predetermined amount of time after closing the valve; and

repeating the opening, closing, and waiting steps until the negative pressure reaches a threshold pressure value.

11. The wound therapy system ofclaim 9, wherein applying the pressure stimulus further comprises operating the pump while the valve is closed to mitigate air leakage into the negative pressure circuit.

12. The wound therapy system ofclaim 9, wherein the dynamic pressure response of the negative pressure circuit is characterized by a depth of purge parameter defined as a difference between:

a measured value of the negative pressure before the valve is opened; and

a measured value of the negative pressure while the valve is open.

13. The wound therapy system ofclaim 9, wherein the dynamic pressure response of the negative pressure circuit is characterized by a rebound parameter defined as a difference between:

a measured value of the negative pressure after the valve is closed; and

a measured value of the negative pressure while the valve is open.

14. The wound therapy system ofclaim 9, wherein the dynamic pressure response of the negative pressure circuit is characterized by a delta parameter defined as a difference between:

a measured value of the negative pressure before the valve is opened; and

a measured value of the negative pressure after the valve is closed.

15. The wound therapy system ofclaim 9, wherein the dynamic pressure response of the negative pressure circuit is characterized by a leak rate parameter defined as a rate at which the negative pressure changes while the valve is closed.

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18. The wound therapy system ofclaim 1, wherein estimating the wound volume based on the dynamic pressure response comprises:

determining values for one or more parameters that characterize the dynamic pressure response; and

applying the values of the one or more parameters as inputs to a model that defines a relationship between the one or more parameters and the wound volume.

19. The wound therapy system ofclaim 18, wherein the model that defines the relationship between the one or more parameters and the wound volume is a polynomial approximation model.

20. The wound therapy system ofclaim 18, wherein the model that defines the relationship between the one or more parameters and the wound volume is a neural network.

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23. The wound therapy system ofclaim 1, wherein the controller is configured to:

execute the pressure testing procedure, observe the dynamic pressure response, and estimate the wound volume at a plurality of times during wound treatment; and

determine healing progression based on changes in the wound volume during wound treatment.

24. The wound therapy system ofclaim 1, wherein the controller is configured to:

determine a volume of instillation fluid to deliver to the wound based on the estimated wound volume; and

operate the pump to deliver the volume of instillation fluid to the wound.

25. The wound therapy system ofclaim 24, wherein the controller is configured to determine the volume of instillation fluid to deliver to the wound by multiplying the estimated wound volume by a fluid instillation factor.

26. The wound therapy system ofclaim 25, wherein the fluid instillation factor is less than one such that less than the total wound volume is filled with the instillation fluid.

27. The wound therapy system ofclaim 25, wherein the fluid instillation factor is between approximately 0.2 and approximately 0.8.

28. A method for estimating a wound volume of a wound, the method comprising:

applying negative pressure to a wound using a negative pressure circuit;

operating a pump fluidly coupled to the negative pressure circuit to control the negative pressure within the negative pressure circuit;

measuring the negative pressure within the negative pressure circuit or at the wound;

executing a pressure testing procedure comprising applying a pressure stimulus to the negative pressure circuit;

observing a dynamic pressure response of the negative pressure circuit to the pressure stimulus using measurements of the negative pressure; and

estimating the wound volume based on the dynamic pressure response.

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35. The method ofclaim 28, further comprising operating a valve coupled to the negative pressure circuit to controllably vent the negative pressure circuit.

36. The method ofclaim 35, wherein applying the pressure stimulus comprises:

opening the valve to allow airflow into the negative pressure circuit for a predetermined amount of time; and

closing the valve after the predetermined amount of time has elapsed.

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55. A wound therapy system comprising:

a negative pressure circuit configured to apply negative pressure to a wound;

a canister containing instillation fluid for delivery to the wound;

a pump operable to deliver the instillation fluid to the wound;

a pressure sensor configured to measure the negative pressure within the negative pressure circuit or at the wound; and

a controller communicably coupled to the pump and the pressure sensor, the controller configured to:

execute a pressure testing procedure to estimate a wound volume of the wound;

determine a volume of instillation fluid to deliver to the wound based on the estimated wound volume; and

operate the pump to deliver the volume of instillation fluid to the wound.

56. The wound therapy system ofclaim 55, wherein the controller is configured to determine the volume of instillation fluid to deliver to the wound by multiplying the estimated wound volume by a fluid instillation factor.

57. The wound therapy system ofclaim 56, wherein the fluid instillation factor is less than one such that less than the total wound volume is filled with the instillation fluid.

58. The wound therapy system ofclaim 56, wherein the fluid instillation factor is between approximately 0.2 and approximately 0.8.

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79. The wound therapy system ofclaim 55, wherein the controller is configured to:

execute the pressure testing procedure to estimate the wound volume at a plurality of times during wound treatment; and

determine healing progression based on changes in the wound volume during wound treatment.

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