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

TNP therapy assists in the closure and healing of wounds by reducing tissue oedema; encouraging blood flow; stimulating the formation of granulation tissue; removing excess exudates and may reduce bacterial load and thus, infection to the wound. Furthermore, TNP therapy permits less outside disturbance of the wound and promotes more rapid healing. For example, <CIT>, <CIT>, <CIT> and <CIT> disclose a negative pressure wound therapy apparatus and a method for its operation.

The present invention is defined by the appended claims and relates to apparatuses for dressing and treating a wound with reduced pressure therapy or topical negative pressure (TNP) therapy. In particular, this invention relates to negative pressure therapy apparatuses for controlling the operation of TNP systems.

The negative pressure wound therapy apparatus includes a negative pressure source configured to provide negative pressure via a fluid flow path to a dressing placed over a wound to create a seal over the wound, a pressure sensor configured to measure pressure in the fluid flow path, and a controller. The controller is configured to, in response to a request to initiate or restart application of negative pressure, operate the negative pressure source in a first mode and determine a change in pressure in the fluid flow path over a period of time based on a plurality of measurements by the pressure sensor over the period of time. The controller is configured to, in response to a determination that pressure in the fluid flow path is decreasing, operate the negative pressure source in a second mode in which the negative pressure source provides a greater amount of negative pressure than in the first mode. The controller is also configured to, in response to a determination that pressure in the fluid flow path is not decreasing, provide an indication of a first leak in the seal.

The request to initiate or restart application of negative pressure is associated with a negative pressure set point to be established in the fluid flow path. Operation of the negative pressure source in the first mode is insufficient to reduce pressure in the fluid flow path to establish the negative pressure set point. Operation of the negative pressure source in the second mode is sufficient to reduce pressure in fluid flow path to establish the negative pressure set point.

The apparatus of any of the preceding paragraphs can include one or more of the following features. Operation of the negative pressure in the second mode can include the controller being further configured to activate the negative pressure source to reduce pressure in the fluid flow path to the negative pressure set point; if pressure in the fluid flow path has not reached the negative pressure set point over a first period of time, deactivate the negative pressure source for a second period of time; and in response to a determination that the second period of time has elapsed, activate the negative pressure source to reduce pressure in the fluid flow path to establish the negative pressure set point.

The apparatus of any of the preceding paragraphs can include one or more of the following features. The controller can be further configured to monitor a number of deactivations of the negative pressure source for the second period of time. The controller can be further configured to provide an indication of a second leak in the seal in response to a determination that the number of the negative pressure source exceeds a retry threshold. The first leak can be a leak of smaller intensity than the second leak. Indication of at least one of the first or second leaks in the seal can include deactivation of the source of negative pressure. Operation of the negative pressure source in the first mode can include establishment of a flow rate of about <NUM>/min in the fluid flow path. Indication of the first leak in the seal can correspond to an indication of a leak with flow of about <NUM>/min or less.

The apparatus of any of the preceding paragraphs can include one or more of the following features. The controller can be configured to determine the change in pressure in the fluid flow path based on a determination of a difference in a first pressure in the fluid flow path measured by the pressure sensor and a second pressure in the fluid flow path subsequently measured by the pressure sensor. The first mode can be a low flow mode. The controller can be configured to operate the negative pressure source in the first mode based on a first drive signal provided to an actuator of the negative pressure source. The controller can be configured to operate the negative pressure source in the second mode based on a second drive signal provided to the actuator of the negative pressure source, the second drive signal being different from the first drive signal.

Insofar as the term disclosure or embodiment is used in the following, or features are presented as being optional, this should be interpreted in such a way that the only protection sought is that of the invention claimed. Reference(s) to "embodiment(s)" throughout the description which are not under the scope of the appended claims merely represent possible exemplary executions and are not part of the present invention.

Disclosed herein are apparatuses and methods of treating a wound with reduced pressure. As is used herein, reduced or negative pressure levels, such as -X mmHg, represent pressure levels relative to normal ambient atmospheric pressure, which can correspond to <NUM> mmHg (or <NUM> atm, <NUM> inHg, <NUM> kPa, <NUM> psi, etc.). In some embodiments, local ambient atmospheric pressure is used as a reference point, and such local atmospheric pressure may not necessarily be, for example, <NUM> mmHg. Accordingly, a negative pressure value of -X mmHg reflects absolute pressure that is X mmHg below, for example, <NUM> mmHg or, in other words, pressure of (<NUM>-X) mmHg. In addition, negative pressure that is "less" or "smaller" than X mmHg corresponds to pressure that is closer to atmospheric pressure (such as, -<NUM> mmHg is less than -<NUM> mmHg). Negative pressure that is "more" or "greater" than -X mmHg corresponds to pressure that is further from atmospheric pressure (such as, -<NUM> mmHg is more than -<NUM> mmHg).

The negative pressure range for some embodiments of the present disclosure can be approximately -<NUM> mmHg, or between about -<NUM> mmHg and -<NUM> mmHg or more. Note that these pressures are relative to normal ambient atmospheric pressure, which can be <NUM> mmHg. Thus, -<NUM> mmHg would be about <NUM> mmHg in practical terms. In some embodiments, the pressure range can be between about -<NUM> mmHg and -<NUM> mmHg. Alternatively a pressure range of up to -<NUM> mmHg, up to -<NUM> mmHg or over -<NUM> mmHg can be used. Also in other embodiments a pressure range of below -<NUM> mmHg can be used. Alternatively, a pressure range of over approximately -<NUM> mmHg, or even -<NUM> mmHg, can be supplied by the negative pressure apparatus.

Embodiments of the present disclosure are generally applicable to use in topical negative pressure ("TNP") therapy systems. Briefly, negative pressure wound therapy assists in the closure and healing of many forms of "hard to heal" wounds by reducing tissue oedema, encouraging blood flow and granular tissue formation, and/or removing excess exudate and can reduce bacterial load (and thus infection risk). In addition, the therapy allows for less disturbance of a wound leading to more rapid healing. TNP therapy systems can also assist in the healing of surgically closed wounds by removing fluid and by helping to stabilize the tissue in the apposed position of closure. A further beneficial use of TNP therapy can be found in grafts and flaps where removal of excess fluid is important and close proximity of the graft to tissue is required in order to ensure tissue viability.

<FIG> illustrates an embodiment of a reduced pressure wound treatment apparatus <NUM> comprising a wound dressing <NUM> in combination with a negative pressure source <NUM>, which is illustrated as a pump assembly. In any of the apparatus embodiments disclosed herein, as in the embodiment illustrated in <FIG>, the negative pressure source can be a canisterless negative pressure source (meaning that the negative pressure source does not have an exudate or liquid collection canister). However, any of the embodiments disclosed herein can be configured to include or support a canister. Additionally, in any of the apparatus embodiments disclosed herein, any of the negative pressure source embodiments can be mounted to, embedded within, or supported by the dressing, or adjacent to the dressing. The dressing <NUM> may be placed over a wound (not illustrated), and a conduit <NUM> may then be connected to the dressing <NUM>. Dressing <NUM> or any other dressing disclosed herein can have be made of any suitable materials, sizes, components, etc. The conduit <NUM> or any other conduit disclosed herein can be formed from polyurethane, PVC, nylon, polyethylene, silicone, or any other suitable material.

Some embodiments of the dressing <NUM> can have a port <NUM> configured to receive an end of the conduit <NUM> (e.g., the first end 106a of the conduit <NUM>), though such port <NUM> is not required. In some embodiments, the conduit can otherwise pass through and/or under the dressing <NUM> to supply a source of reduced pressure to a space between the dressing <NUM> and the wound so as to maintain a desired level of reduced pressure in such space. Some embodiments of the apparatus <NUM> can be configured such that the first end 106a of the conduit <NUM> is pre-attached to the port <NUM>. The conduit <NUM> can be any suitable article configured to provide at least a substantially sealed fluid flow pathway between the negative pressure source <NUM> and the dressing <NUM>, so as to supply the reduced pressure provided by the negative pressure source <NUM> to the dressing <NUM>. In some embodiments, the port <NUM> can be made of soft, flexible materials such that, for example, the user would experience little or no discomfort if the user lies or otherwise puts pressure on the dressing <NUM> and/or the port <NUM>.

The dressing <NUM> can be provided as a single article with all wound dressing elements (including the port <NUM>) pre-attached and integrated into a single unit. The wound dressing <NUM> may then be connected, via the conduit <NUM>, to a source of negative pressure such as the negative pressure source <NUM>. In some embodiments, though not required, the negative pressure source <NUM> can be miniaturized and portable, such as the PICO (TM) pump, although larger conventional pumps, such as the EZ CARE (TM) pump, can also be used with the dressing <NUM>. The pump can be a diaphragm pump (or any other type of negative pressure pump) actuated by an electric motor, a voice-coil actuator, a piezoelectric actuator, etc..

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

In some embodiments, it may be preferable for the wound site to be filled partially or completely with a wound packing material. This wound packing material is optional, but may be desirable in certain wounds, for example deeper wounds. The wound packing material can be used in addition to the wound dressing <NUM>. The wound packing material generally can comprise a porous and conformable material, for example foam (including reticulated foams), and gauze. Preferably, the wound packing material is sized or shaped to fit within the wound site so as to fill any empty spaces. The wound dressing <NUM> can then be placed over the wound site and wound packing material overlying the wound site. When a wound packing material is used, once the wound dressing <NUM> is sealed over the wound site, TNP is transmitted from a pump through the wound dressing <NUM>, through the wound packing material, and to the wound site. This negative pressure draws wound exudate and other fluids or secretions away from the wound site.

In some embodiments, the tubing <NUM> can have a connector <NUM> positioned at a second end 106b of the tubing <NUM>. The connector <NUM> can be configured to couple with a short length of conduit <NUM> projecting from the negative pressure source <NUM>, with a mating connector 114a in communication with the short length of conduit <NUM>, with a connector supported by the pump housing, or otherwise. The length of the tubing <NUM> in some embodiments can be approximately <NUM> (. <NUM> in), or from approximately. <NUM> in to approximately <NUM> inches. The short length of conduit or tubing <NUM> can decrease the discomfort to a patient while laying or otherwise resting on the pump and connector <NUM>. Configuring the negative pressure source <NUM> and tubing <NUM> so that the tubing <NUM> can be quickly and easily removed from the negative pressure source <NUM> can facilitate or improve the process of dressing or pump changes, if necessary. Any of the pump embodiments disclosed herein can be configured to have any of the connection configurations disclosed herein between the tubing and the pump.

In some embodiments, as in the illustrated embodiment, the negative pressure source <NUM> can be of a sufficiently small and portable size to be supported on a user's body or in a user's clothing or on the dressing <NUM>. For example, the negative pressure source <NUM> can be sized to be attached using adhesive medical tape or otherwise to a person's skin in a comfortable location, adjacent to or on the dressing <NUM> or otherwise. Further, the negative pressure source <NUM> can be sized to fit within a person's pants or shirt pocket, or can be tethered to a person's body using a lanyard, pouch, or other suitable device or article.

Some embodiments of the apparatus <NUM> are designed to operate without the use of an exudate canister. The dressing <NUM> can be configured to have a film having a high water vapour permeability to enable the evaporation of surplus fluid, and can have a superabsorbing material contained therein to safely absorb wound exudate. Some embodiments of the apparatus are designed for single-use therapy and can be disposed of in an environmentally friendly manner after an approximately maximum usage of from seven to eleven days. The pump can be programmed to automatically terminate therapy after a desired number of days, e.g., after seven days, further operation of the pump will not be possible. Some embodiments are designed for longer or repeated usage, and can be configured to support an exudate canister.

In some embodiments, the system <NUM> provides indication, alarms, etc. to the user reflecting operating conditions. The system <NUM> can include visual, audible, tactile, and other types of indicators and/or alarms configured to signal to the user various operating conditions. Such conditions include system on/off, standby, pause, normal operation, dressing problem, leak, error, and the like. The indicators and/or alarms can include one or more speakers, displays, light sources, etc., and/or combinations thereof. For example, indication can be provided by activating or deactivating the source of negative pressure, reducing negative pressure level generated by the source of negative, lowering the amount of power used by the source of negative pressure, etc. or any combination thereof.

As is illustrated in <FIG>, indicators <NUM> can be one or more light emitting diodes (LEDs). The indicators <NUM> can be positioned on a housing <NUM> of the negative pressure source <NUM> and can be configured to alert a user to a variety of operating and/or failure conditions of the negative pressure source, including alerting the user to normal or proper operating conditions, pump failure, power supplied to the pump or power failure, the condition or voltage level of the batteries, detection of a leak within the dressing (e.g., in the seal) or flow pathway, suction blockage, or any other similar or suitable conditions or combinations thereof. In some embodiments, the indicators <NUM> can include a battery indicator, an OK indicator, and a dressing indicator. The negative pressure source <NUM> can also have a control button <NUM> (which can also be a switch or other similar component).

The fluidic connection between the dressing <NUM> and the negative pressure source <NUM> can be referred to as the fluid flow path.

In some embodiments, such as when the negative pressure source <NUM> is mounted to or embedded within the dressing <NUM>, portions of or the entirety of one or more of the conduit <NUM>, the port <NUM>, the connector <NUM>, or the conduit <NUM> can be omitted.

In some embodiments, the negative pressure source <NUM> is controlled by at least one controller, which can be coupled to at least one memory.

In some embodiments, the negative pressure source <NUM> can be configured to control the operation of system. For example, the negative pressure source <NUM> can be configured to provide a suitable balance between uninterrupted delivery of therapy and/or avoidance of inconveniencing the user by, for example, frequently or needlessly pausing or suspending therapy and a desire to conserve power, limit noise and vibration generated by the negative pressure source, etc. <FIG> illustrates a top level state diagram <NUM> of operation of the negative pressure source according to some embodiments. In some embodiments, a controller of the negative pressure source can be configured to implement the flow of the state diagram <NUM>. As is illustrated in <FIG>, the operation of the negative pressure source can, in some embodiments, be grouped into four general state categories: inactive/initialization (states <NUM> and <NUM>), active <NUM>, operational <NUM>, and end of life (state <NUM>). As is illustrated in <FIG> and <FIG>, state categories <NUM> and <NUM> each comprises multiple states and transitions between states.

In some embodiments, so long as a power source (e.g., one or more batteries) is not connected to the negative pressure source or removed (as is illustrated by the transition <NUM>), or the negative pressure source has not been activated (e.g., by pulling an activation strip, triggering a switch, or the like), the negative pressure source remains in state <NUM>. While remaining in this state, the negative pressure source can remain inactive. When the power source is connected and/or the negative pressure source has been activated for a first time, the negative pressure source transitions to state <NUM>, where power on self-test(s) (POST) can be performed. Power on self-test(s) can include performing various checks to ensure proper functionality of the system, such as testing a memory (e.g., performing a check, such as a cyclic redundancy check, of the program code to determine its integrity, testing the random access memory, etc.), reading a pressure sensor to determine whether the pressure values are within suitable limits, reading the remaining capacity or life of the power source (e.g., battery voltage, current, etc.) to determine whether it is within suitable limits, testing the negative pressure source, and the like. As is illustrated, indicators (e.g., one or more LEDs, one or more LCDs, etc.) can be configured to indicate to the user (e.g., by blinking or flashing once) that the negative pressure source is undergoing POST test(s).

In some embodiments, if one or more of POST test(s) fail, the negative pressure source can transition to non-recoverable error state <NUM>. While in this state, the negative pressure source can deactivate therapy, and the indicators <NUM> can be configured and indicate to the user that an error was encountered. In some embodiments, all indicators can be configured to remain active. Based on the severity of error, in some embodiments, the negative pressure source can be configured to recover from the error and continue operation (or transition to the non-recoverable error state <NUM>). As is illustrated, the negative pressure source can transition to state <NUM> upon encountering a fatal error during operation. Fatal errors can include program memory errors, program code errors (e.g., encountering an invalid variable value), controller operation errors (e.g., watchdog timer expires without being reset by the controller), component failure (e.g., inoperative negative pressure source, inoperative pressure sensor, etc.), and any combination thereof.

When POST test(s) pass, in some embodiments, the negative pressure source can transition to a manually paused state <NUM>. As is illustrated, this transition can be indicated to the user by deactivating one of indicators <NUM> (e.g., the battery indicator). When the negative pressure source transitions into and remains in the manually paused state <NUM>, the user can be provided an indication, such as by deactivating one or more indicators (e.g., the OK indicator and the dressing indicator). In some embodiments, therapy can be suspended while the negative pressure source remains in the manually paused state <NUM>. For example, the source of negative pressure (e.g., pump) can be deactivated (or turned off). In some embodiments, indication can be provided by deactivating the source of negative pressure.

In some embodiments, the negative pressure source can be configured to make a transition <NUM> from the manually paused state <NUM> to the operational state category <NUM> (where the negative pressure source is configured to deliver therapy) in response to receiving a signal from the switch. For example, the user can press a button to start, suspend, and/or restart therapy. In some embodiments, the negative pressure source can be configured to monitor the duration of time the negative pressure source remains in the manually paused state <NUM>. This can be accomplished, for example, by maintaining a timer (in firmware, software, hardware or any combination thereof), which can be reset and started when the negative pressure source transitions into the manually paused state <NUM>. The negative pressure source can be configured to automatically make the transition <NUM> from the manually paused state <NUM> to the operational state category <NUM> when the time duration exceeds a threshold. In some embodiments, such threshold can be a preset value, such as between <NUM> minute or less and <NUM> hour or more. In some embodiments, the threshold can be set or changed by the user. In some embodiments, the threshold can be varied based on various operating conditions or on any combination thereof. For example, as the negative pressure source nears the end of life (as is explained below), the threshold can be decreased. In some embodiments, the user can pause therapy by activating the switch (e.g., pressing the button), thereby causing the negative pressure source to make a transition <NUM> from the operational state category <NUM> to the manually paused state <NUM>. In some embodiments, the negative pressure source can be configured so that the user can only pause therapy, whereas disconnecting the power source (e.g., removing batteries) stops therapy.

In some embodiments, the negative pressure source can be configured to include a paused state <NUM>. When the negative pressure source transitions into and remains in the paused state <NUM>, the user can be provided an indication. For example, the negative pressure source can be configured to deactivate the OK indicator and cause the dressing indicator to flash or blink. In some embodiments, therapy can be suspended while the negative pressure source remains in the manually paused state <NUM>. For example, the source of negative pressure (e.g., pump) can be deactivated (or turned off), which provides the indication to the user that the negative pressure source is in the paused state <NUM>. As is explained below, in some embodiments, the negative pressure source can be configured to transition from the operational state category <NUM> into the paused state <NUM> when a number of retry cycles exceeds a retry limit (transition <NUM>) or when duty cycle is determined to exceed a duty cycle limit (transition <NUM>). In some embodiments, transitions <NUM> and <NUM> can reflect the presence of a leak in the system.

In some embodiments, the negative pressure source can be configured to make a transition <NUM> from the paused state <NUM> to the operational state category <NUM> (where the negative pressure source is configured to activate the pump to deliver therapy) in response to receiving a signal from the switch (e.g., the user pressing a button to restart therapy). In some embodiments, the negative pressure source can be configured to monitor the duration of time the negative pressure source remains in the paused state <NUM>. For example, this can be accomplished by maintaining a timer (in firmware, software, hardware or any combination thereof), which can be reset and started when the negative pressure source transitions into the paused state <NUM>. The negative pressure source can be configured to automatically make the transition <NUM> from the paused state <NUM> to the operational state category <NUM> when the time duration exceeds a threshold. The threshold can be the same or different than the threshold of the manually paused state <NUM> described herein. In some embodiments, the threshold can be a preset value, such as between <NUM> minute or less and <NUM> hour or more. In some embodiments, the threshold can be set or changed by the user. In some embodiments, the threshold can be varied based on various operating conditions or on any combination thereof. For example, as the negative pressure source nears the end of life (as is explained below), the threshold can be decreased.

In some embodiments, the negative pressure source includes both the manually paused state <NUM> and the paused state <NUM> in order to differentiate between various causes for pausing therapy. Such ability to differentiate can allow the negative pressure source to provide the user with an indication of a particular cause for pausing therapy (e.g., manually paused state <NUM> and paused state <NUM> can provide different indications). For example, therapy can be paused due to the user manually pressing the button, in which case the negative pressure source can make the transition <NUM> from the operational state category <NUM> to the manually paused state <NUM>. As another example, therapy can be paused due to detecting a leak, in which case the negative pressure source can make the transition <NUM> and/or <NUM> from the operational state category <NUM> to the paused state <NUM>. In some embodiments, the negative pressure source can be configured to include one state indicating a suspension or pause in the delivery of therapy or more than two such states.

In some embodiments, the negative pressure source can be configured to monitor the remaining capacity or life of the power source (e.g., by periodically reading or sampling the battery voltage, current, etc.). The negative pressure source can be configured to indicate to the user the remaining capacity. For example, if the power source is determined to have a normal remaining capacity (e.g., as a result of comparison to a threshold, such as <NUM>. 5V, etc.), the battery indicator can be deactivated. If the power source is determined to have low remaining capacity, the negative pressure source can be configured to provide an indication to the user by, for example, causing the battery indicator to blink or flash, as is illustrated by the transition <NUM>. In some embodiments, the battery indicator can be configured to be blinking or flashing intermittently or continuously regardless of the state the negative pressure source is in or only in particular states.

In some embodiments, when the remaining capacity of the power source is determined to be at or near a critical level (e.g., as a result of comparison to a threshold, such as <NUM>. 2V, etc.), the negative pressure source can be configured to transition into a battery critical state <NUM>. In some embodiments, the negative pressure source can be configured to remain in this state until the capacity of the power source is increased, such as by replacing or recharging the power source. The negative pressure source can be configured to deactivate therapy while remaining in the battery critical state <NUM>. In addition, as is illustrated, the negative pressure source can be configured to indicate to the user that the power source is at or near the critical level by, for example, deactivating all indicators.

In some embodiments, the negative pressure source can be configured to provide therapy for a predetermined period of time, such as approximately <NUM> day, <NUM>-<NUM> days, etc. following a first activation. In some embodiments, such period of time can be a preset value, changed by the user, and/or varied based on various operating conditions or on any combination thereof. The negative pressure source can be disposed upon the expiration of such period of time. In some embodiments, the first activation can be reflected by a transition into the active state category <NUM>, by pulling the activation strip (e.g., transition into state <NUM>), etc. Once the negative pressure source has been activated, the negative pressure source can be configured to monitor the duration it has remained active. In some embodiments, the negative pressure source can be configured to monitor the cumulative duration of remaining in the active state category <NUM>. This can be accomplished, for example, by maintaining a timer (in firmware, software, hardware or any combination thereof), that reflects such duration.

When the duration reaches or exceeds a threshold (e.g., <NUM> days, <NUM> days, etc.), the negative pressure source can be configured to transition to an end of life (EOL) state <NUM>. The negative pressure source can be configured to deactivate therapy while remaining in state <NUM> and to indicate to the user that end of negative pressure source' usable life has been reached. For example, the negative pressure source can be configured to deactivate all indicators and/or deactivate the button. In some embodiments, when the negative pressure source is disposable, transitioning to the end of life state <NUM> means that the negative pressure source can be disposed of. The negative pressure source can be configured to disable reactivation of the negative pressure source once the end of life has been reached. For example, the negative pressure source can be configured to not allow reactivation even if the power source is disconnected and reconnected later, which can be accomplished by storing an indication, value, flag, etc. in the read only memory.

<FIG> illustrates the operational flow in state category <NUM> of the negative pressure source <NUM> according to some embodiments. The negative pressure source can be configured to deliver therapy, monitor leaks in the system, provide indication(s) to the user, and the like. As is explained below, in some embodiments, the negative pressure source can be configured to deliver therapy by initially attempting to establish a first set point or desired negative pressure level (e.g., negative pressure between -<NUM> mmHg or less and -<NUM> mmHg or more, such as -<NUM> mmHg) in the fluid flow path (e.g., under the dressing <NUM>). In some embodiments, the first desired negative pressure level can be a preset value, set or changed by the user, and/or varied based on various operating conditions or on any combination thereof. Once the first desired negative pressure level is established in the fluid flow path, the negative pressure source can be configured to deactivate the source of negative pressure (e.g., pump). When negative pressure in the fluid flow path (e.g., under the dressing <NUM>) decreases (e.g., gravitates toward standard atmospheric pressure) due to leaks in the system, the negative pressure source can be configured to restore negative pressure in the fluid flow path by activating the pump to establish a second set point or desired negative pressure level in the fluid flow path (e.g., negative pressure between -<NUM> mmHg or less and -<NUM> mmHg or more, such as -<NUM> mmHg). In some embodiments, the second desired negative pressure level can be a preset value, set or changed by the user, and/or varied based on various operating conditions or on any combination thereof. In some embodiments, the first and second desired negative pressure levels can be the same. In some embodiments, the first and second desired negative pressure levels can be different, that is, the second negative pressure level can be less than the first negative pressure level or vice versa.

In some embodiments, the negative pressure source can transition from the manually paused state <NUM> and/or paused state <NUM> to state <NUM>. As is explained herein, this transition can be caused by the user pressing the button to start/restart therapy and/or upon expiration of duration of time, such as <NUM> hour. The negative pressure source can be configured to immediately transition to an initial pump down (IPD) state <NUM>, where the negative pressure source can be activated to establish the first desired negative pressure level in the fluid flow path. In some embodiments, the negative pressure source can be activated if the pressure level in the fluid flow path is above (less than) the first desired negative pressure level. Activating the source of negative pressure to establish the first desired negative pressure level in the fluid flow path (e.g., under the dressing <NUM>) can be referred to herein as the "initial pump down. " The negative pressure source can be configured to indicate to the user that it is performing the initial pump down by, for example, causing the OK indicator to blink or flash and deactivating the dressing indicator. In some embodiments, the indication can be provided by, for example, activating the source of negative pressure. The negative pressure source can be configured to measure the level of pressure in the fluid flow path by reading or sampling the sensor. The pressure sensor can be positioned in any suitable location in the fluid flow path, such as at or near the pump inlet, under or near the dressing, etc. In some embodiments, more than one pressure sensor is positioned in the fluid flow path such as, for example, in different locations.

In some embodiments, the negative pressure source can be configured to monitor the duration of time the negative pressure source remains in the IPD state <NUM>. This can be accomplished, for example, by maintaining a timer (in firmware, software, hardware or any combination thereof), which can be reset and started when the negative pressure source transitions into the IPD state <NUM>. In some embodiments, in order to conserve power, limit the noise and/or vibration generated by the pump, etc., the negative pressure source can be configured to suspend the initial pump down operation for a period of time and, later, retry the initial pump down. This functionality can, for example, conserve battery power and allow transient and/or non-transient leaks to become resolved without user intervention or allow the user to fix the leak (e.g., straighten the dressing, fix the seal, check the connection or connections, etc.).

In some embodiments, when the duration of time for remaining in the IPD state <NUM> equals or exceeds a threshold (e.g., <NUM> seconds), the negative pressure source can be configured to make the transition <NUM> to state <NUM>. In some embodiments, the threshold can be a preset value, such as between <NUM> seconds or lower and <NUM> minutes or higher. In some embodiments, the threshold can be set or changed by the user. In some embodiments, the threshold can be varied based on various operating conditions or on any combination thereof. In some embodiments, the negative pressure source can be configured to deactivate the pump when making the transition <NUM>. The negative pressure source can be configured to monitor a number attempts (e.g., by maintaining a counter which can be reset in state <NUM> and updated in wait state <NUM>) made to establish the first desired negative pressure in the fluid flow path. In some embodiments, the negative pressure source can be configured to provide a limited or maximum number of IPD retry attempts in order, for example, to conserve power. Preferably, the negative pressure source can be configured to provide a limited number of consecutive IPD retry attempts, although the negative pressure source can be configured to provide a limited number of non-consecutive IPD retry attempts or a mix of consecutive and non-consecutive IPD retry attempts. The threshold for IPD retry attempts can be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and so on. In some embodiments, the threshold can be a preset value. In some embodiments, the threshold can be set or changed by the user. In some embodiments, the threshold can be varied based on various operating conditions or on any combination thereof.

In some embodiments, the negative pressure source can be configured to determine in state <NUM> whether the number of IPD retry attempts made is equal to or exceeds the threshold (e.g., <NUM> retry attempt). In case the number of IPD retry attempts made is equal or exceeds the threshold, the negative pressure source can be configured to make the transition 1228a to the paused state <NUM>, where therapy is paused or suspended as is described herein. Otherwise, the negative pressure source can be configured to make the transition <NUM> to the wait state <NUM>. In some embodiments, the negative pressure source can be configured to deactivate the source of negative pressure in state <NUM>, which can provide an indication to the user that the negative pressure source transitioned to state <NUM>.

In some embodiments, the negative pressure source can be configured to deactivate the pump in the wait state <NUM>, thereby pausing therapy for a period of time (e.g., between <NUM> second or less and <NUM> minute or more, such as <NUM> seconds). This can be accomplished, for example, by maintaining a timer (in firmware, software, hardware or any combination thereof), which can be reset and started when the negative pressure source transitions into the wait state <NUM>. This period of time in the wait state <NUM> can be preset or variable (e.g., automatically or by the user). In some embodiments, the period of time can be varied based on various operating conditions or on any combination thereof. The period of time the negative pressure source remains in the wait state <NUM> can be decreased or increased (e.g., multiplied by a factor between <NUM> or less and <NUM> or more, such as <NUM>), on each transition into the wait state <NUM>. The period of time can be decreased or increased on each successive transition into the wait state <NUM>. The period of time can be decreased or increased until it equals or passes a threshold (e.g., between <NUM> second or less and <NUM> minutes or more, such as <NUM> minutes). In addition, the period of time can be reset to an initial value upon transition to a monitor pressure state <NUM>, transition to the manually paused state <NUM>, transition to the paused state <NUM>, etc..

In some embodiments, the negative pressure source can be configured to indicate to the user that the negative pressure source is in the wait state <NUM>. For example, the negative pressure source can be configured to cause the OK indicator to flash or blink and deactivate the dressing indicator. In some embodiments, deactivating the pump can provide indication that the negative pressure source is in the wait state <NUM>. Upon expiration of the period of time in the wait state, the negative pressure source can be configured to make the transition <NUM> from the wait state <NUM> to the IPD state <NUM>, where the negative pressure source can attempt to establish the first desired negative pressure level in the fluid flow path. In some embodiments, the negative pressure source can be configured to ensure that the negative pressure level under the dressing remains above a certain safety level. For example, the negative pressure source can be configured to maintain the negative pressure level in the fluid flow path above a safety level between -<NUM> mmHg or less and -<NUM> mmHg or more, such as -<NUM> mmHg.

In some embodiments, the retry transitions (e.g., transitions <NUM>, <NUM>, and <NUM>) between the IPD state <NUM>, state <NUM>, and the wait state <NUM> can detect a leak with high flow, such as a leak that prevents the initial pump down. For example, the retry transitions can detect a leak with a flow of <NUM> scc/m (e.g., <NUM>/min or any lower or higher suitable flow) or more. A leak having smaller flow may be detected by the transitions (e.g., <NUM> and <NUM>) between states <NUM> and <NUM> as explained below, but such detection may take a long period of time, such as <NUM> minutes or more. In certain cases, there is a need to detect a low flow leak quickly. For example, a healthcare professional that may place the dressing on the patient and activate delivery of negative pressure therapy, may need to be quickly alerted that there is a leak so that the healthcare professional can remedy the leak.

In some embodiments, a lower flow leak can be quickly detected by a leak check state <NUM>, which is entered from the IPD state <NUM> (via a transition <NUM>) prior to initial pump down or directly from the manually paused state <NUM> and/or the paused state <NUM>. In the leak check state <NUM>, the controller can operate the negative pressure source to provide a lower flow rate in the fluid flow path than, for example, in the IPD state <NUM>. While the flow rate provided by the negative pressure source may not be sufficient to perform the initial pump down of the wound, the flow rate is nonetheless sufficient to detect if a low flow leak is present in the fluid flow path. For example, the negative pressure source can be configured to provide a flow rate of about <NUM> scc/m (e.g., <NUM>/min or any other lower or higher suitable flow) in the leak check state <NUM>. While the negative pressure source operates in such low flow mode, the controller can analyze the change in pressure in the fluid flow path (e.g., under the dressing) to identify signs of successful depressurization, such as whether the pressure in the fluid flow path is decreasing, which is indicative of leak rate (e.g., in dressing seal) being below the negative pressure flow rate and therefore within acceptable levels. On the other hand, if the pressure in the fluid flow path remains static at or below atmospheric pressure, this can be indicative of the leak rate being above the flow rate of the negative pressure source (e.g., <NUM> scc/m or any other suitable lower or higher flow), which may not be acceptable.

The controller can analyze the change in pressure in the fluid flow path based on multiple pressure readings received from the pressure sensor. For example, a first pressure reading P<NUM> can be taken at time t<NUM> and a second pressure reading P<NUM> can be taken at a subsequent time t<NUM>. Times t<NUM> and t<NUM> can be a second or less or more apart. Based on the difference between pressure levels P<NUM> and P<NUM>, the controller can determine if the pressure in the fluid flow path is decreasing (e.g., becoming more negative). In some embodiments, more than two pressure readings can be used and multiple pressure readings can be further processed, such as averaged, smoothed, low-pass filtered, etc., to minimize the risk of making an erroneous determination. In some embodiments, change in pressure is analyzed over a period of time, such as <NUM> seconds or more or less.

In certain implementations, in response to detecting that a leak is present in the fluid flow path, the controller can provide one or more indications to the user. For example, the controller can cause a transition <NUM> to the pause state <NUM>, where therapy is paused or suspended as is described herein. If the controller does not detect presence of a leak, transition <NUM> to the IPD state <NUM> can be made and the negative pressure source continues to operate as described herein. In some embodiments, detection of a leak in the leak check state <NUM> can be performed in a minute or less. In some implementations, detection of a leak can be performed in <NUM> seconds or less, <NUM> seconds or less, etc..

In certain embodiments, the leak check state <NUM> can be replaced by measuring the rate of pressure change in the fluid flow path when the negative pressure source is deactivated, such as for example in the wait state <NUM>. However, while the rate of decay of the negative pressure (toward atmospheric pressure) may indicate a presence of a leak, the volume of the wound may need to be known in order to make an accurate determination. In some cases, the volume of the wound is not known a priori. Utilizing the leak check state <NUM> as described herein may provide a solution that is independent of the wound volume. Because fluid flow rates are analyzed as described herein, even though a large volume would depressurize more slowly than a small one, the large wound volume would still depressurize due to one or more leaks, which can be detected as described herein.

In some embodiments, a negative pressure source can be calibrated to operate in the leak check state <NUM>. For example, a drive signal supplied to the actuator of the pump can be selected (e.g., during calibration in manufacturing, etc.) to cause the pump to provide low flow to detect presence of a leak. The drive signal can be selected so that it will not cause the pump to stall. A different drive signal can be used in the IPD state.

In some embodiments, when the first desired negative pressure level in the fluid flow path has been established, the negative pressure source can be configured to make the transition <NUM> to a monitor state <NUM>. The negative pressure source can be configured to reset the number of IPD retry attempts when making the transition <NUM>. The negative pressure source can be configured to indicate the transition to the monitor state <NUM> to the user by, for example, causing the OK indicator to blink or flash and deactivating the dressing indicator. While remaining in the monitor state <NUM>, the negative pressure source can be configured to deactivate the pump (which can provide an indication to the user that the negative pressure source is in the monitor state <NUM>) and periodically or continuously monitor the level of pressure in the fluid flow path. The negative pressure source can be configured to measure the level of pressure in the fluid flow path by reading or sampling the sensor.

In some embodiments, the negative pressure source can be configured to determine whether, for example, due to leaks in the system, the level of negative pressure in the fluid flow path decreases to reach and/or pass (e.g., become less than) a threshold. The threshold can be selected from the range between -<NUM> mmHg or less and -<NUM> mmHg or more, such as -<NUM> mmHg. In some embodiments, the threshold can be a preset value, set or changed by the user, and/or varied based on various operating conditions or on any combination thereof. If the threshold is determined to be reached or passed, the negative pressure source can be configured to restore the level of negative pressure in the fluid flow path. In some embodiments, the negative pressure source can be configured to reestablish the first desired negative pressure level or establish another, different negative pressure level. This can be accomplished by making the transition <NUM> to a maintenance pump down (MPD) state <NUM>.

In some embodiments, the negative pressure source can be configured to activate the pump to establish the desired level of negative pressure in the fluid flow path (e.g., the first desired level) while the negative pressure source remains in the MPD state <NUM>. The negative pressure source can be configured to provide an indication to the user, for example, by causing the OK indicator to blink or flash and deactivating the dressing indicator. In some embodiments, the negative pressure source activating the source of negative pressure can provide an indication to the user that the negative pressure source transitioned to state <NUM>. In some embodiments, the negative pressure source can be configured to generate less noise and vibration when the pump is activated in the MPD state <NUM> than when the pump is activated in the IPD state <NUM>. For example, the difference in the noise level can be between <NUM> dB or less and <NUM> dB or more, such as approximately <NUM> dB, approximately <NUM> dB, etc. As another example, the difference in the noise level can be between <NUM> dB or less to <NUM> dB or more, such as approximately <NUM> dB, approximately <NUM> dB, approximately <NUM> dB, etc..

In some embodiments, the negative pressure source can be configured to monitor the duration of time it remains in the MPD state <NUM>. This can be accomplished, for example, by maintaining a timer (in firmware, software, hardware or any combination thereof), which can be reset and started when the negative pressure source makes the transition <NUM> into the MPD state <NUM>. In some embodiments, in order to conserve power, limit the noise and/or vibration generated by the pump, etc., the negative pressure source can be configured to suspend the maintenance pump down operation for a period of time and, later, retry the initial pump down and/or maintenance pump down. This functionality can, for example, conserve battery power and allow transient and/or non-transient leaks to become resolved without user intervention or allow the user to fix the leak (e.g., straighten the dressing, fix the seal, check the connection or connections, etc.).

In some embodiments, when the duration of time in the MPD state <NUM> equals or exceeds a threshold (e.g., a value between <NUM> seconds or lower and <NUM> minutes or higher, such as <NUM> seconds) and the pressure level in the fluid flow path has not reached the desired negative pressure level, the negative pressure source can be configured to make the transition <NUM> to state <NUM>. The threshold can be a preset value, set or changed by the user, and/or varied based on various operating conditions or on any combination thereof. In some embodiments, the negative pressure source can be configured to deactivate the pump when making the transition <NUM>, which can provide an indication to the user that the negative pressure source is making the transition. The negative pressure source can be configured to monitor a number of MPD attempts (e.g., by maintaining a counter which can be reset in the state <NUM> and/or when making the transition 1228b and updated when making the transition <NUM>) made to establish the desired negative pressure in the fluid flow path. In some embodiments, the negative pressure source can be configured to provide a limited or maximum number of MPD retry attempts (e.g., to conserve power). Preferably, the negative pressure source can be configured to provide a limited number of consecutive MPD retry attempts, although the negative pressure source can be configured to provide a limited number of non-consecutive MPD retry attempts or a mix of consecutive and non-consecutive retry attempts. The threshold for MPD retry attempts can be <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and so on. In some embodiments, the threshold can be a preset value, set or changed by the user, and/or varied based on various operating conditions or on any combination thereof. The negative pressure source can be configured to set the number of IPD and MPD retry attempts to the same or different value. The negative pressure source can be configured to determine in state <NUM> whether the number of MPD retry attempts made is equal to or exceeds the threshold (e.g., <NUM> retry attempts). In case the number of MPD retry attempts made is equal or exceeds the threshold, the negative pressure source can be configured to make the transition 1228b to the paused state <NUM>, where therapy is paused or suspended as is described herein. Otherwise, the negative pressure source can be configured to make the transition <NUM> to the wait state <NUM>, where therapy is paused or suspended as is described herein. Alternatively, the negative pressure source can be configured to make the transition to the IPD state <NUM> or MPD state <NUM>.

In some embodiments, the negative pressure source can be configured to make the transition <NUM> to the monitor state <NUM> if the level of pressure under the dressing reaches or exceeds (e.g., become greater than) the desired negative pressure level. The negative pressure source can also be configured to reset the number of MPD retry attempts when making the transition <NUM>.

In some embodiments, the negative pressure source can be configured to monitor the duty cycle of the source of negative pressure (e.g., pump). The negative pressure source can be configured to monitor the duty cycle periodically and/or continuously. Duty cycle measurements can reflect various operating conditions of the system, such as presence and/or severity of leaks, rate of flow of fluid (e.g., air, liquid and/or solid exudate, etc.) aspirated from wound, and so on. For example, duty cycle measurements can indicate presence of a high leak, and the negative pressure source can be configured to indicate this condition and/or temporarily suspend or pause operation of the pump in order to conserve power. This functionality can, for example, conserve battery power and allow transient and/or non-transient leaks to become resolved without user intervention or allow the user to fix the leak (e.g., straighten the dressing, fix the seal, check the connection or connections, etc.).

In some embodiments, the negative pressure source can be configured to periodically monitor the duty cycle, such as once between every <NUM> seconds or less and <NUM> minutes or more. In some embodiments, the negative pressure source can be configured to monitor the duty cycle once per minute. This can be accomplished by maintaining a timer (in firmware, software, hardware or any combination thereof), which can be set to expire every minute (e.g., as is indicated by an interrupt or via polling) and can be restarted (e.g., by clearing an interrupt). In some embodiments, the time interval for measuring the duty cycle can be a preset value, set or changed by the user, and/or varied based on various operating conditions or on any combination thereof. In some embodiments, the negative pressure source can be configured to monitor the duty cycle when the negative pressure source is in the operational state category <NUM> (i.e., any of states <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and/or any transitions between any of the states), as the negative pressure source is configured to activate the pump in this state category. In some embodiments, the negative pressure source can be configured to monitor the duty cycle when the negative pressure source is in a particular state and/or state transition or subset of states and/or state transitions of the operational state category <NUM>. In some embodiments, the negative pressure source can be configured to monitor the duty cycle when the pump assembly is in a particular state and/or state transition, subset of states and/or state transitions, or all states and/or state transitions of the active state category <NUM> or any combination of any states and/or state transitions disclosed herein. As is illustrated in <FIG>, the negative pressure source can make the transition <NUM> from any of states <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and/or transitions between any of the states to state <NUM>, where the negative pressure source determines the duty cycle of the pump during the elapsed minute. The duty cycle can be determined according to the equation:
<MAT>
where DC is the duty cycle, t is the duration that the source of negative pressure is active, and T is the total time under consideration. In case of monitoring the duty cycle once per minute (i.e., T = <NUM> seconds), the duty cycle can be expressed (e.g., in percent) as:
<MAT>.

In order to determine the duty cycle, the negative pressure source can be configured to monitor the duration of time that the pump has been active (e.g., the pump run time) and/or inactive.

In some embodiments, the negative pressure source can be configured to compare the determined duty cycle to a duty cycle threshold, which can be selected from the range between <NUM>% or less and <NUM>% or more. The comparison can, for example, indicate presence of a leak in the system. In other words, if the pump is remains active over a period of time so that the duty cycle threshold is reached or exceeded, the pump may be working hard to overcome the leak. In such cases, the negative pressure source can be configured to suspend or pause the delivery of therapy. The negative pressure source can be configured to provide an indication to the user that the pump is working hard (e.g., duty cycle exceeds the duty cycle threshold) by, for example, deactivating the source of negative pressure. In some embodiments, the duty cycle threshold can be a preset value, set or changed by the user, and/or varied based on various operating conditions or on any combination thereof. As is illustrated in <FIG>, the negative pressure source can be configured to compare the determined duty cycle to the duty cycle threshold (e.g., <NUM>% or another suitable fixed or dynamic threshold). The negative pressure source can be configured to monitor the number of duty cycles that exceed the threshold by, for example, maintaining and updating an overload counter, which can be reset when the negative pressure source transitions from state <NUM> to the IPD state <NUM>.

In some embodiments, the negative pressure source can be configured to update the overload counter in state <NUM>. If the determined duty cycle does not exceed the duty cycle threshold, the negative pressure source can decrement the overload counter. In some embodiments, the minimum value of overload counter can be set to zero, that is the overload counter cannot become negative. Conversely, if the determined duty cycle is equal to or exceeds the duty cycle threshold, the negative pressure source can increment the overload counter.

In some embodiments, the negative pressure source can be configured to monitor a total or aggregate number of duty cycles that equal to or exceed the duty cycle threshold. This approach can help to smooth or average the duty cycle variation in order to, for example, prevent one or several erratic cycles that may be caused by a transient leak from interrupting therapy. In some embodiments, the negative pressure source can be configured to monitor consecutive or non-consecutive duty cycles exceeding the duty cycle threshold. In some embodiments, the threshold can be a preset value, set or changed by the user, and/or varied based on various operating conditions or on any combination thereof. If the number of duty cycles that exceed the duty cycle threshold is determined to exceed an overload threshold (e.g., a number between <NUM> and <NUM> or more, such as <NUM>), the negative pressure source can be configured to make the transition <NUM> to the paused state <NUM>, where therapy is suspended or paused as is described herein. In some embodiments, the negative pressure source can be configured to deactivate the source of negative pressure, which can provide an indication to the user that the pump is working hard (e.g., duty cycle exceeds the overload threshold). If the number of duty cycles that exceed the duty cycle threshold is not determined to exceed the overload threshold, the negative pressure source can be configured to make the transition <NUM> and remain in the operational state category <NUM>. In some embodiments, the negative pressure source can be configured to return to the same state and/or transition between states from which the negative pressure source made the transition <NUM>. In some embodiments, the negative pressure source can be configured to transition to a different state and/or transition between states.

In some embodiments the negative pressure source is further configured to suspend or pause therapy if the user presses the button <NUM> while the negative pressure source is in the operational state category <NUM>. In some embodiments, the negative pressure source can be configured to transition to the manually paused state <NUM>.

<FIG> illustrates another state diagram of operation of the negative pressure source <NUM> according to some embodiments. In some embodiments, the controller can be configured to implement the flow of the state diagram <NUM>. In some embodiments, the flow <NUM> can be largely similar to the flow illustrated in <FIG>. State <NUM> corresponds to state <NUM>, state <NUM> corresponds to state <NUM>, state category <NUM> corresponds to state category <NUM>, state <NUM> corresponds to state <NUM>, state <NUM> corresponds to state <NUM>, state <NUM> corresponds to state <NUM>, transition <NUM> corresponds to transition <NUM>, transition <NUM> corresponds to transition <NUM>, transition <NUM> corresponds to the transition <NUM>, transition <NUM> corresponds to transition <NUM>, state <NUM> corresponds to state <NUM>, and state <NUM> corresponds to the state <NUM>. In addition, state category <NUM> corresponds to state category <NUM>, state <NUM> corresponds to state <NUM>, transition <NUM> corresponds to transition <NUM>, state <NUM> corresponds to transition <NUM>, transition <NUM> corresponds to transition <NUM>, transition 1428a corresponds to transition 1228a, state <NUM> corresponds to state <NUM>, and transition <NUM> corresponds to transition <NUM>. Further, transition <NUM> corresponds to transition <NUM>, state <NUM> corresponds to state <NUM>, transition <NUM> corresponds to transition <NUM>, state <NUM> corresponds to state <NUM>, transition <NUM> corresponds to transition <NUM>, state <NUM> corresponds to state <NUM>, transition <NUM> corresponds to transition <NUM>, transition 1428b corresponds to transition 1228b, transition <NUM> corresponds to transition <NUM>, transition <NUM> corresponds to transition <NUM>, and transition <NUM> corresponds to transition <NUM>.

In some embodiments, the negative pressure source can be configured to monitor the duty cycle after a desired negative pressure level is established in the fluid flow path in the MPD state <NUM>. In some embodiments, the negative pressure source can also take into account the duration of time that the pump has been active while the negative pressure source remains in the IPD state <NUM>. As is illustrated, the device can be configured to make the transition <NUM> from the MPD state <NUM>. Transition <NUM> can be similar to the transition <NUM>, but instead of transitioning directly to the IPD state <NUM>, the negative pressure source can be configured to monitor the duty cycle in state <NUM>. In some embodiments, the negative pressure source can be configured to monitor the duty cycle during a cumulative period of time that the negative pressure source has remained in the monitor state <NUM> and MPD state <NUM>. In some embodiments, the negative pressure source can be configured to monitor the duty cycle over the cumulative period of time during the immediately preceding or previous monitor and MPD cycles. For example, immediately before transitioning to state <NUM> the negative pressure source could have remained in the MPD state <NUM> for time duration X (during which the pump was active). In addition, assuming that immediately before transitioning to the MPD state <NUM>, the negative pressure source remained in the monitor state <NUM> for a time duration Y (during which the pump was not active), the duty cycle (DC) can be expressed (e.g., in percent) as:
<MAT>.

In order to determine the duty cycle, the negative pressure source can be configured to monitor the duration of time that the pump has been active and/or inactive.

In some embodiments, the negative pressure source can be configured to compare the determined duty cycle to a duty cycle threshold, as is described herein. In some embodiments, the threshold can be a preset value, set or changed by the user, and/or varied based on various operating conditions or on any combination thereof. If the duty cycle is determined to be below the threshold, the negative pressure source can be configured to make the transition <NUM> to the monitor state <NUM>. Conversely, if the duty cycle is determined to be equal to or exceed the threshold, the negative pressure source can be configured to make the transition <NUM> to state <NUM>. In some embodiments, the negative pressure source can provide an indication that the duty cycle exceeds the threshold by, for example, deactivating the pump.

In some embodiments, the negative pressure source can be configured to monitor a total or aggregate time over which the duty cycle is equal to or exceeds the threshold. This approach can help to smooth or average the duty cycle variation in order to, for example, prevent one or several erratic cycles that may be caused by a transient leak from interrupting therapy. Monitoring can be accomplished by maintaining a timer (in firmware, software, hardware or any combination thereof), which can be restarted (e.g., on the transition <NUM>) and updated (e.g., in state <NUM>). In some embodiments, the negative pressure source can be configured to determine whether the duty cycle equals to or exceeds the threshold over a certain aggregate period of time, which can be compared to an aggregate duration threshold. The threshold can be selected from a range between <NUM> minutes or less and <NUM> hours or more, such as <NUM> minutes. In some embodiments, the threshold can be a preset value, set or changed by the user, and/or varied based on various operating conditions or on any combination thereof. If the aggregate period of time equals to or exceeds the threshold, the negative pressure source can be configured to make the transition <NUM> to the paused state <NUM>, where the negative pressure source can be configured to suspend or pause the delivery of therapy. In some embodiments, the negative pressure source can indicate this transition to the user by, for example, deactivating the pump. Conversely, if the aggregate period of time is determined to be less than the threshold, the negative pressure source can be configured to make the transition <NUM> to the monitor state <NUM>. The pump assembly can be configured to indicate the transition <NUM> to the user by, for example, causing the OK indicator to blink or flash and deactivating the dressing indicator.

Additional embodiments of controlling the negative pressure source as described in <CIT>. Additional embodiments of calibrating the drive signal of a pump are described in <CIT> The embodiments described herein are compatible with and can be part of the embodiments described in these publications, and some or all of the features described herein can be used or otherwise combined with any of the features described in these publications.

Features, materials, characteristics, or groups described in conjunction with a particular aspect, embodiment, or example are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features or steps are mutually exclusive.

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

Claim 1:
A negative pressure wound therapy apparatus (<NUM>) comprising:
a negative pressure source (<NUM>) configured to provide negative pressure via a fluid flow path to a dressing (<NUM>) placed over a wound to create a seal over the wound;
a pressure sensor configured to measure pressure in the fluid flow path; and
a controller configured to, in response to a request to initiate or restart application of negative pressure:
operate the negative pressure source in a first mode;
determine a change in pressure in the fluid flow path over a period of time based on a plurality of measurements by the pressure sensor over the period of time;
in response to a determination that pressure in the fluid flow path is decreasing, operate the negative pressure source in a second mode in which the negative pressure source provides a greater amount of negative pressure than in the first mode; and
in response to a determination that pressure in the fluid flow path is not decreasing, provide an indication of a first leak in the seal and
wherein:
the request to initiate or restart application of negative pressure is associated with a negative pressure set point to be established in the fluid flow path;
operation of the negative pressure source in the first mode is insufficient to reduce pressure in the fluid flow path to establish the negative pressure set point; and
operation of the negative pressure source in the second mode is sufficient to reduce pressure in fluid flow path to establish the negative pressure set point.