Method and system for detecting sensor drift of an intravascular blood pump

Abstract

Methods and apparatuses for detecting sensor drift associated with a pressure sensor of a heart pump are provided. The method includes receiving a pressure signal from a pressure sensor disposed on a heart pump; determining a feature within a time window of the pressure signal; updating a minimum feature value or a maximum feature value based at least in part on the feature within the time window; determining whether a range of the feature is greater than a threshold, wherein the range is determined as a difference between the minimum feature value and the maximum feature value; and performing an action upon determining that the range of the feature is greater than the threshold.

Description

Technical Field

[0001] This disclosure relates to a technique for detecting sensor drift in intravascular blood pumps. Background Technology

[0002] Fluid pumps, such as blood pumps, are used for a wide range of applications and purposes in the medical field. An intravascular blood pump is a pump that can be advanced through a patient's vascular system (i.e., veins and / or arteries) to a location within the patient's heart or other parts of the patient's circulatory system. For example, an intravascular blood pump can be inserted via a catheter and positioned across one or more heart valves. The intravascular blood pump is typically positioned at the end of the catheter. Once in place, the pump can be used to assist the heart and pump blood through the circulatory system, and thus temporarily reduce the load on the patient's heart, for example, to allow the heart to recover after a heart attack. An exemplary intravascular blood pump may be branded under the name Impella. ® The heart pump was purchased from ABIOMED, ​​Inc., Danvers, MA.

[0003] Intravascular blood pumps are typically connected to a corresponding external heart pump controller, which controls the heart pump (such as motor speed) and collects and displays operational data about the blood pump, such as cardiac signal levels, battery temperature, blood flow rate, and tubing integrity. An exemplary heart pump controller may be branded as Automated Impella Controller. ® Purchased from Abiomed. In some cases, the controller may issue an alarm when operating data values ​​fall outside a predetermined value or range, such as in the event of a leak, suction, and / or pump failure. The controller may include a video display screen displaying a graphical user interface configured to display operating data and / or alarms. Summary of the Invention

[0004] Intravascular blood pumps may include one or more pressure sensors configured to sense pressure values ​​within a patient's heart during placement and / or operation of the blood pump. The sensitivity of pressure sensors to temperature changes and / or other factors can cause the pressure signal sensed by such pressure sensors to undergo sensor drift (e.g., DC offset) over time. For example, the sensor mounting process used to mount the pressure sensor onto the blood pump may result in different thicknesses of the silicone film on different pumps, which may lead to different sensor drift characteristics for sensors used on different pumps. Sensor drift can affect the accuracy of operational data and / or alarms presented on the graphical user interface of a controller associated with the blood pump. This document describes systems and methods for detecting sensor drift associated with pressure signals sensed by pressure sensors of an intravascular blood pump, based at least in part on the analysis of pressure signals. Although the techniques described herein are for detecting sensor drift in the differential pressure signal of a pressure sensor of a blood pump inserted across the right ventricular valve, it should be understood that at least some of these techniques can also be used to detect sensor drift in the signals of different types of sensors associated with an intravascular blood pump (e.g., pressure sensors of blood pumps inserted across the left ventricular valve).

[0005] In one aspect, a method is provided for detecting sensor drift associated with a pressure sensor of a heart pump. The method includes: receiving a pressure signal from a pressure sensor disposed on a heart pump; determining features of the pressure signal within a time window; updating a minimum or maximum feature value based at least in part on the features within the time window; determining whether a range of the features is greater than a threshold, wherein the range is determined as the difference between the minimum and maximum feature values; and performing an action when the range of the features is determined to be greater than the threshold.

[0006] In another aspect, the pressure sensor includes a differential pressure sensor. In another aspect, a heart pump is inserted across the pulmonary valve of the patient's heart, and the pressure signal is a differential pressure signal across the pulmonary valve. In another aspect, determining the characteristics within a time window of the pressure signal includes using a random phase approximation technique to determine the characteristics. In another aspect, determining the characteristics within a time window of the pressure signal includes calculating the sum of the pressure signal values ​​within the time window of the pressure signal. In another aspect, the method further includes initializing a minimum eigenvalue and a maximum eigenvalue to the same value, and updating the minimum eigenvalue and / or the maximum eigenvalue based at least in part on the characteristics includes: updating the minimum eigenvalue to the sum when the sum is less than the minimum eigenvalue, or updating the maximum eigenvalue to the sum when the sum is greater than the maximum eigenvalue.

[0007] In another aspect, performing an action when the determined characteristic's range exceeds a threshold includes outputting an alarm indicating that a reference value for the pressure signal should be recalibrated. In another aspect, outputting an alarm indicating that a reference value for the pressure signal should be recalibrated includes providing an alarm on a display. In another aspect, performing an action includes recalibrating the reference value for the pressure signal. In another aspect, the method further includes determining the threshold based at least in part on the motor speed associated with the heart pump's motor. In another aspect, the pressure signal is associated with a reference value, and the method further includes determining that a predetermined amount of time has elapsed since the last calibration of the reference value, and performing an action when the determined characteristic's range exceeds the threshold and after the predetermined amount of time has elapsed.

[0008] In another aspect, determining the characteristics within a time window of the pressure signal includes determining the average value of the pressure signal within the time window. In another aspect, the method further includes initializing a minimum characteristic value and a maximum characteristic value to the same value, and updating the minimum and / or maximum characteristic values ​​at least in part based on the characteristics includes: updating the minimum characteristic value to the average value when the average value is less than the minimum characteristic value, or updating the maximum characteristic value to the average value when the average value is greater than the maximum characteristic value. In another aspect, performing an action when the determined range of the characteristics exceeds a threshold includes outputting an alarm indicating that a reference value of the pressure signal should be recalibrated. In another aspect, outputting an alarm indicating that a reference value of the pressure signal should be recalibrated includes providing an alarm on a display. In another aspect, performing an action includes recalibrating the reference value of the pressure signal. In another aspect, the length of the time window is one minute.

[0009] In one aspect, a heart pump system is provided. The heart pump system includes a heart pump and a controller. The heart pump includes a pressure sensor configured to sense pressure within a portion of a patient's heart. The controller is configured to: receive a pressure signal from the pressure sensor; determine characteristics of the pressure signal within a time window; update a minimum or maximum characteristic value based at least in part on the characteristics within the time window; determine whether a range of the characteristics is greater than a threshold, wherein the range is determined to be the difference between the minimum and maximum characteristic values; and perform an action when the range of the characteristics is determined to be greater than the threshold.

[0010] In another aspect, the pressure sensor includes a differential pressure sensor. In another aspect, the heart pump is configured for insertion across the pulmonary valve of the patient's heart, and the pressure signal is a differential pressure signal across the pulmonary valve. In another aspect, determining the characteristics within a time window of the pressure signal includes using a random phase approximation technique to determine the characteristics. In another aspect, determining the characteristics within a time window of the pressure signal includes calculating the sum of the pressure signal values ​​within the time window of the pressure signal. In another aspect, the controller is further configured to initialize a minimum characteristic value and a maximum characteristic value to the same value, and updating the minimum characteristic value and / or the maximum characteristic value based at least in part on the characteristics includes: updating the minimum characteristic value to the sum when the sum is less than the minimum characteristic value, or updating the maximum characteristic value to the sum when the sum is greater than the maximum characteristic value.

[0011] In another aspect, performing an action when the determined characteristic's range exceeds a threshold includes outputting an alarm indicating that a reference value for the pressure signal should be recalibrated. In another aspect, outputting an alarm indicating that a reference value for the pressure signal should be recalibrated includes providing an alarm on a display. In another aspect, performing an action includes recalibrating the reference value for the pressure signal. In another aspect, the controller is further configured to determine the threshold at least in part based on the motor speed associated with the heart pump's motor. In another aspect, the pressure signal is associated with a reference value, and the controller is further configured to determine that a predetermined amount of time has elapsed since the last calibration of the reference value, and to perform an action when the determined characteristic's range exceeds a threshold and after the predetermined amount of time has elapsed.

[0012] In another aspect, determining the characteristics within a time window of the pressure signal includes determining the average value of the pressure signal within the time window. In another aspect, the controller is further configured to initialize the minimum and maximum characteristic values ​​to the same value, and to update the minimum and / or maximum characteristic values ​​at least partially based on the characteristics, including: updating the minimum characteristic value to the average value when the average value is less than the minimum characteristic value, or updating the maximum characteristic value to the average value when the average value is greater than the maximum characteristic value. In another aspect, performing an action when the determined range of the characteristic exceeds a threshold includes outputting an alarm indicating that a reference value for the pressure signal should be recalibrated. In another aspect, outputting an alarm indicating that a reference value for the pressure signal should be recalibrated includes providing an alarm on a display. In another aspect, performing an action includes recalibrating the reference value for the pressure signal. In another aspect, the length of the time window is one minute.

[0013] In one aspect, a controller for a heart pump system is provided. The controller includes at least one hardware processor. The at least one hardware processor is configured to: receive a pressure signal from a pressure sensor disposed on a heart pump of the heart pump system; determine characteristics of the pressure signal within a time window; update a minimum or maximum characteristic value based at least in part on the characteristics within the time window; determine whether a range of the characteristics is greater than a threshold, wherein the range is determined to be the difference between the minimum and maximum characteristic values; and perform an action when the range of the characteristics is determined to be greater than the threshold.

[0014] In another aspect, the pressure sensor includes a differential pressure sensor. In another aspect, the heart pump is configured for insertion across the pulmonary valve of the patient's heart, and the pressure signal is a differential pressure signal across the pulmonary valve. In another aspect, determining the characteristics within a time window of the pressure signal includes using a random phase approximation technique to determine the characteristics. In another aspect, determining the characteristics within a time window of the pressure signal includes calculating the sum of the pressure signal values ​​within the time window of the pressure signal. In another aspect, the at least one hardware processor is further configured to initialize a minimum characteristic value and a maximum characteristic value to the same value, and to update the minimum characteristic value and / or the maximum characteristic value at least in part based on the characteristics, including: updating the minimum characteristic value to the sum when the sum is less than the minimum characteristic value, or updating the maximum characteristic value to the sum when the sum is greater than the maximum characteristic value.

[0015] In another aspect, performing an action when the determined characteristic's range exceeds a threshold includes outputting an alarm indicating that a reference value for the pressure signal should be recalibrated. In another aspect, outputting an alarm indicating that a reference value for the pressure signal should be recalibrated includes providing an alarm on a display. In another aspect, performing an action includes recalibrating the reference value for the pressure signal. In another aspect, the at least one hardware processor is further configured to determine the threshold based at least in part on the motor speed associated with the heart pump's motor. In another aspect, the pressure signal is associated with a reference value, and the at least one hardware processor is further configured to determine that a predetermined amount of time has elapsed since the last calibration of the reference value, and to perform an action when the determined characteristic's range exceeds the threshold and after the predetermined amount of time has elapsed.

[0016] In another aspect, determining the characteristics within a time window of the pressure signal includes determining the average value of the pressure signal within the time window. In another aspect, at least one hardware processor is further configured to initialize a minimum characteristic value and a maximum characteristic value to the same value, and to update the minimum and / or maximum characteristic values ​​at least in part based on the characteristics, including: updating the minimum characteristic value to the average value when the average value is less than the minimum characteristic value, or updating the maximum characteristic value to the average value when the average value is greater than the maximum characteristic value. In another aspect, performing an action when the determined range of the characteristics exceeds a threshold includes outputting an alarm indicating that a reference value for the pressure signal should be recalibrated. In another aspect, outputting an alarm indicating that a reference value for the pressure signal should be recalibrated includes providing an alarm on a display. In another aspect, performing an action includes recalibrating the reference value for the pressure signal. In another aspect, the length of the time window is one minute. Attached Figure Description

[0017] Figure 1A An exemplary cardiac support device is shown that can be used with some implementation schemes.

[0018] Figure 1B It shows including Figure 1A An exemplary cardiac support system.

[0019] Figure 2A A graph showing the motor speed signal of a heart support device according to some embodiments is shown.

[0020] Figure 2B A graph showing the differential pressure signal sensed by a pressure sensor of a cardiac support device according to some embodiments is shown.

[0021] Figure 2C A graph of the motor current signal associated with a cardiac support device is shown according to some embodiments.

[0022] Figure 3 This is a flowchart of a process for detecting sensor drift associated with a sensor in a cardiac support device, according to some implementation schemes.

[0023] Figure 4 This is a flowchart illustrating the process of detecting sensor drift using sample requests and techniques, based on some implementation schemes.

[0024] Figure 5 This is a flowchart of a process for detecting sensor drift using averaged placement signal technology, based on some implementation schemes.

[0025] Figure 6A This illustrates the use according to some implementation schemes. Figure 5A graph showing instances of sensor drift detected using the average placement signal technique.

[0026] Figure 6B This is an example of what happens when... Figure 6A The graph shown is a graph of the average motor current associated with the cardiac support device during the time period associated with it. Detailed Implementation

[0027] Physicians and other healthcare providers may rely on indications of operational status and / or patient physiological parameters displayed by the controller of a cardiac support device (e.g., an intravascular blood pump) to ensure the device is correctly placed in the patient's heart and / or to determine whether device settings (e.g., pump rate) should be adjusted when the device is providing support to the patient. The cardiac support device may include one or more sensors (e.g., pressure sensors) configured to sense pressure in one or more chambers of the patient's heart, and the sensed pressure signals can be used to determine one or more of the indications of operational status and / or patient physiological parameters displayed by the controller. For example, the controller may be configured to display indications of the patient's central venous pressure (CVP) and pulmonary artery pressure (PAP) based at least in part on differential pressure signals sensed by pressure sensors of the cardiac support device inserted into the right side of the patient's heart. The differential pressure signal may reflect the pressure difference across the pulmonary valve of the patient's heart. As the pressure sensors continuously sense differential pressure sensor measurements during operation of the cardiac support device, the displayed CVP and PAP values ​​and / or waveforms may be updated by the controller in real-time (or near real-time).

[0028] Over time, the differential pressure signal sensed by the differential pressure sensor may drift from a reference (e.g., baseline) value, which can lead to inaccurate estimates of various physiological parameters such as CVP and PAP. Some conventional techniques for detecting sensor drift in pressure sensors used in cardiac support devices may require the user to notice erroneous values ​​being displayed on the controller (e.g., large negative values ​​for CVP and / or PAP). The inventors have recognized and understand that manual detection of sensor drift is challenging, especially when the user is not focused on detecting it, because sensor drift tends to manifest in the sensed pressure signal (and the physiological measurements based on the sensed pressure signal) over a relatively long time span. To this end, some embodiments of this disclosure relate to novel data-driven techniques for detecting sensor drift based on the analysis of the sensed pressure signal.

[0029] Figure 1AAn exemplary embodiment of a blood pump assembly 100 according to the present disclosure is shown. The blood pump assembly 100 may include a pump 101, a pump housing 103, a proximal end 105, a distal end 107, a cannula 108, an impeller (not shown), a non-invasive extension 102, a catheter 112, an inlet region 110, an outlet region 106, and a blood discharge port 117. In some embodiments, the catheter 112 may be connected to the inlet region 110 of the cannula 108. The inlet region 110 may be located near the proximal end 105 of the cannula, and the outlet region 106 may be positioned toward the distal end 107 of the cannula 108. The inlet region 110 may include the pump housing 103 having an outer peripheral wall 111 extending about an axis of rotation of the impeller blades, the outer peripheral wall being radially outwardly positioned relative to the axis of rotation of the impeller outside the inner surface. An impeller may be rotatably coupled to pump 101 at an inlet region 110 adjacent to blood discharge port 117, which is formed in the wall 111 of pump housing 103. According to some embodiments, pump housing 103 may be made of metal. Extension 102, also referred to as a "pigtail tube," may be connected to the distal end 107 of cannula 108 and may help stabilize the blood pump assembly 100 and / or position it correctly in the heart. The pigtail tube may be configured from a straight configuration to a partially curved configuration. The pigtail tube may be at least partially made of a flexible material and may have dual rigidity. It should be understood that some embodiments of the pump assembly may not include a pigtail tube.

[0030] The cannula 108 may have a shape that matches (or is similar to) the anatomy of the patient's right ventricle. Figure 1A In the exemplary embodiment shown, the cannula has a proximal end 105 arranged near the patient's inferior vena cava and a distal end 107 arranged near the pulmonary artery. The cannula 108 may include a first segment S1 extending from the inflow region to point B between the inlet region 110 and the outlet region 106. The cannula 108 may also include a second segment S2 extending from point C between the inlet region 110 and the outlet region 106 to the outlet region 106. In some embodiments, points B and C may be located at the same location along the cannula 108. The first segment S1 of the cannula may be formed in an "S" shape in a first plane. In some embodiments, segment S1 may have a curvature between 30 degrees and 180 degrees. The second segment S2 of the cannula may be formed in an "S" shape in a second plane. In some implementations, segment S2 may have a curvature between 30 and 180 degrees (e.g., 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, or 170°). The second plane may be different from the first plane. In some implementations, the second plane may be parallel to or identical to the first plane.

[0031] Although shown as an "S" shape, it should be understood that other embodiments of the blood pump assembly may be formed in other shapes (e.g., a "U" shape), or may not have a shape at all when outside the body. In such embodiments, the cannula may be formed of a flexible material, allowing it to bend during insertion and achieve the desired shape once inside the patient's heart.

[0032] In some embodiments, the blood pump assembly 100 can be percutaneously inserted through the internal jugular vein, through the right atrium, and into the right ventricle. When properly positioned, the blood pump assembly 100 can deliver blood from an inlet region 110 located inside the patient's right atrium through a cannula 108 to a blood outlet 117 of a pump housing 103 located in the pulmonary artery. Alternatively, in some embodiments, the blood pump assembly 100 can be percutaneously inserted through the femoral artery and into the left ventricle to deliver blood from the left ventricle into the aorta.

[0033] Figure 1B The blood pump assembly 100 is shown to form part of a cardiac support system 120. The cardiac support system 120 may also include a controller 130 (e.g., the AutomatedImpella Controller from Abeomed, Danvers, Massachusetts). ® The system includes a monitor 140, a cleaning subsystem 150, a connector cable 160, a plug 170, and a repositioning unit 180. As shown, the controller 130 may include the monitor 140. The controller 130 may be configured to monitor and control the operation of the blood pump assembly 100. During operation, the cleaning subsystem 150 may be configured to deliver cleaning fluid to the blood pump assembly 100 via a catheter 112 to prevent blood from entering the motor (not shown) of the heart pump. In some embodiments, the cleaning fluid is a dextran solution (e.g., a 5% aqueous solution of dextran containing 25 IU / mL or 50 IU / mL heparin, although this solution does not need to contain heparin in all embodiments). The connector cable 160 provides an electrical connection between the blood pump assembly 100 and the controller 130. The plug 170 may connect the catheter 112, the cleaning subsystem 150, and the connector cable 160. In some implementations, the thimble 170 includes a storage device (e.g., a memory) configured to store, for example, operating parameters to facilitate the transfer of the patient to another controller when needed. The repositioning unit 180 can be used to reposition the blood pump assembly 100 within the patient's heart (e.g., by maintaining the position of the pump assembly relative to the patient).

[0034] like Figure 1BAs shown, in some embodiments, the cardiac support system 120 may include a cleaning subsystem 150 having a container 151, a supply line 152, a cleaning cartridge 153, a cleaning tray 154, a cleaning tubing 155, a check valve 156, a pressure reservoir 157, an infusion filter 158, and a side arm 159. The container 151 may be, for example, a bag or a bottle. It should be understood that in other embodiments, the cardiac support system 120 may not include a cleaning subsystem. In some embodiments, cleaning fluid may be stored in the container 151. The supply line 152 may provide a fluid connection between the container 151 and the cleaning cartridge 153. The cleaning cartridge 153 may control how the cleaning fluid in the container 151 is delivered to the blood pump assembly 100. For example, the cleaning cartridge 153 may include one or more valves for controlling the pressure and / or flow rate of the cleaning fluid. The cleaning tray 154 may include one or more pressure sensors and / or flow sensors for measuring the pressure and / or flow rate of the cleaning fluid. As shown, the controller 130 may include the cleaning cartridge 153 and the cleaning tray 154. A cleaning line 155 provides a fluid connection between the cleaning tray 154 and the check valve 156. A pressure reservoir 157 provides additional filling volume during cleaning fluid changes. In some embodiments, the pressure reservoir 157 may include a flexible rubber diaphragm that uses an expansion chamber to provide additional filling volume. An infusion filter 158 helps prevent bacterial contamination and air ingress into the catheter 112. A side arm 159 provides a fluid connection between the infusion filter 158 and the plug 170. Although shown with separate cleaning lines and connector cables, it should be understood that in some embodiments, the cardiac support system 120 may include a single connector where both fluid and electrical connections are available to the controller 130.

[0035] During operation, controller 130 may be configured to receive measurements from one or more pressure sensors (not shown) included as part of blood pump assembly 100 and cleaning tray 154. Controller 130 may also be configured to control the operation of motors (not shown) of blood pump assembly 100 and cleaning cartridge 153. In some embodiments, controller 130 may be configured to control and measure the pressure and / or flow rate of the cleaning fluid via cleaning cartridge 153 and cleaning tray 154. During operation, after exiting cleaning subsystem 150 via side arm 159, cleaning fluid may be directed through cleaning lumen (not shown) within conduit 112 and plug 170. Sensor cables (not shown), connector cables 160, and plug 170 within conduit 112 provide electrical connections between components of blood pump assembly 100 (e.g., one or more pressure sensors) and controller 130. Motor cables (not shown), connector cables 160, and plug 170 within conduit 112 provide electrical connections between the motor of blood pump assembly 100 and controller 130. During operation, controller 130 can be configured to receive measurements from one or more pressure sensors of blood pump assembly 100 via sensor cables (e.g., optical fibers) and control the electrical power delivered to the motor of blood pump assembly 100 via motor cables. By controlling the power delivered to the motor of blood pump assembly 100, controller 130 can be operated to control the speed of the motor.

[0036] Various modifications can be made to the cardiac support system 120 and one or more of its components. For example, one or more additional sensors can be added to the blood pump assembly 100. In another example, a signal generator can be added to the blood pump assembly 100 to generate a signal indicating the rotational speed of the motor of the blood pump assembly 100. Furthermore, one or more components of the cardiac support system 120 can be separate. For example, the display 140 can be integrated into another device that communicates with the controller 130 (e.g., wirelessly or via one or more electrical cables).

[0037] As described herein, a cardiac pump (e.g., blood pump assembly 100) may include a pressure sensor (e.g., a differential pressure sensor) configured to detect the pressure difference between the inlet and outlet of the cardiac pump when the pump is positioned across a valve in a patient's heart. For example, when a right ventricular cardiac support device is correctly positioned, the pump inlet may be located within the right atrium of the patient's heart, and the cardiac pump outlet may be located within the pulmonary artery of the patient's heart, where the pump crosses the pulmonary valve. The pressure signal sensed by the differential pressure sensor may be used, at least in part, to determine the correct positioning of the cardiac pump within the patient's heart and / or to determine various pressure measurements (e.g., CVP, PAP) that may be displayed to a user during pump operation.

[0038] Such as combination Figure 1A and Figure 1BAs described, a cardiac support system (e.g., cardiac support system 120) may include a controller (e.g., controller 130) configured to control the operation of a motor of a cardiac pump to cause the impeller of the cardiac pump to rotate at a specific speed (referred to herein as P level, where P0 is the slowest speed and P9 is the fastest speed), thereby affecting the rate at which blood is pumped from the inlet to the outlet of the cardiac pump. Figure 2A A graph showing the relationship between P level and time for exemplary operation of a heart pump system is presented. Figure 2A As shown, the pump operates at the P level of P9 for a time period t1, and then at the P level of P7 for a time period t2. Figure 2B It shows in Figure 2A The graph shows the differential pressure (dP) signal sensed by the differential pressure sensor of the heart pump during time periods t1 and t2. Figure 2C The graph shows the motor current signal during the same time periods t1 and t2. (Example) Figure 2B As can be observed, the differential pressure signal (dP) drifts during each of the time periods t1 and t2, while... Figure 2C As can be observed, the motor current remains relatively constant during each of the time periods t1 and t2. Figure 2C The arrow in the middle indicates the execution and Figure 2B The diagram shows the calibration time points for the reference value (e.g., DC reference value) associated with the differential pressure signal. As shown, the reference value can be recalibrated each time the P level is changed. It can also be recalibrated at other times when the user determines that such recalibration is necessary due to sensor drift. As discussed herein, sensor drift is not automatically detected in conventional systems, and therefore, when to recalibrate the reference value for the differential pressure signal is determined by the user upon noticing a problem with one or more of the displayed signals. (See also...) Figure 6A and Figure 6B The automated sensor drift detection technique discussed herein can detect sensor drift much faster than relying on conventional user identification techniques.

[0039] Figure 3 A process 300 for detecting sensor drift in a pressure sensor signal, according to some embodiments, is illustrated. Process 300 may begin in action 310, in which a sensor signal is received from a heart pump. As described herein, the heart pump may have one or more pressure sensors (e.g., differential pressure sensors) disposed thereon. During placement and / or operation of the heart pump, one or more pressure sensors may be configured to output a pressure signal, which is sent to a controller associated with the heart pump (e.g., [controller name missing]). Figure 1B The controller 130 shown is illustrated. In some embodiments, the controller can be configured to process the received signal to detect sensor drift (e.g., by performing...). Figure 3 The process 300 is shown. After receiving the sensor signal, process 300 can proceed to action 312, in which a feature (e.g., DC feature) can be determined within a time window of the received sensor signal. Figure 2B As illustrated in the examples, sensor drift tends to occur over relatively long timescales (e.g., hours, days, etc.). The inventors have recognized that drift characteristics determined within shorter time windows (e.g., seconds, minutes, etc.) can be used to approximate sensor drift trends over longer timescales. For example, in some embodiments, a random phase approximation feature can be determined in action 312, which can be used to approximate a global function of sensor drift using a semi-local density function computation. In some embodiments, the feature can be computed as a statistical value (e.g., sum, average, etc.) within a time window, which characterizes the sensor value within the window. Figure 4 The process shown is 400 and Figure 5 The process 500 shown provides further details of some examples of methods for determining features according to some embodiments of this disclosure.

[0040] Process 300 then proceeds to action 314, in which the minimum or maximum value of the feature can be updated, at least in part, based on the feature determined in action 312. Some embodiments track the range of feature values ​​over time to detect drift in the sensor signal. For example, a minimum and maximum feature value can be stored, and each time a new feature value is determined in action 312, the minimum and maximum feature values ​​can be updated if the newly determined feature value is less than the stored minimum or greater than the stored maximum. In some embodiments, starting from a reference time (e.g., at the beginning of recording sensor values, after calibrating a reference value for the sensor signal when there is a change in motor speed (e.g., P level)), the minimum and maximum feature values ​​can be set to the same value (e.g., the reference value). In subsequent iterations of the feature determined in action 312, the minimum or maximum feature value can be updated in action 314 according to various conditions as described herein.

[0041] Process 300 then proceeds to action 316, in which it can be determined whether the range of the difference between the determined minimum and maximum eigenvalues ​​is greater than a threshold. In some embodiments, the threshold may be the same for all motor speeds (e.g., P level). In other embodiments, different thresholds may be used for different motor speeds. In some embodiments, the threshold may change over time (e.g., the threshold may increase over time to allow for more sensor drift over time). In some embodiments, the threshold may be reset at a reference time (e.g., at the beginning of recording sensor values, after calibrating a reference value for the sensor signal when there is a change in motor speed (e.g., P level)).

[0042] If the range is determined not to be greater than a threshold in action 316, process 300 can return to action 312, in which a feature is determined for a new observation time window. Actions 312, 314, and 316 can then be repeated until the range of the feature determined in action 316 is greater than the threshold, or until a reset / recalibration event occurs (e.g., a change in motor speed). If the range is determined to be greater than the threshold in action 316, sensor drift can be detected, and process 300 can proceed to action 318, in which an action is performed to resolve the sensor drift. In some embodiments, performing the action includes outputting an indication that the sensor drift is out of range and should be corrected (e.g., by manual recalibration or resetting the reference value). For example, an alarm can be displayed on a user interface associated with a controller of a cardiac support system to notify the user that a recalibration of the reference value of the sensor signal should be performed. As another example, the controller can be configured to initiate a recalibration of the reference value of the sensor signal to correct the sensor drift. In yet another example, both recalibration (e.g., automatic recalibration) and an alarm that recalibration has been performed can be performed in action 318.

[0043] Figure 4 A process 400 of a first technique for detecting sensor drift in a sensor signal (e.g., a differential pressure signal) according to some embodiments of the present disclosure is illustrated. Process 400 may begin in action 410, in which the sensor signal (e.g., the differential pressure signal) is received from the heart pump (e.g., via a controller). Process 400 may then proceed to action 412, in which the sum S(t) is calculated according to the following formula:

[0044] ,

[0045] Where n is the number of samples in the observation time window, and dP is the sensor signal (in this case, the differential pressure sensor signal). In some implementations, n can be equal to 255, such that 256 samples present in the observation time window are considered in the summation at time t. At a sampling rate of 25 Hz, this 256-sample observation time window corresponds to a summation over approximately 10 seconds. Calculating the summation S(t) can be considered analogous to applying a low-pass filter to the sensor signal to smooth the high-frequency components of the signal. By smoothing the high-frequency components, the features can be used to approximate the low-frequency behavior of the signal.

[0046] Process 400 can then proceed to action 414, in which the maximum value of the sum (S) can be updated based on the sum S(t) calculated in action 412. max ) and the minimum value of the sum (S) min As described in action 314 of process 300, the minimum eigenvalue (in this case, S) can be stored. min ) and the largest eigenvalue (in this case, S) max Furthermore, when a new characteristic value is determined, if the newly determined characteristic value is less than the stored minimum value or greater than the stored maximum value, the minimum and maximum characteristic values ​​can be updated. Additionally, starting from a reference time (e.g., at the beginning of recording sensor values, after calibrating the reference value of the sensor signal when there is a change in motor speed (e.g., P level), the minimum characteristic value (e.g., S) can be updated. min ) and the largest eigenvalue (e.g., S) max Initialize them to the same value. For example, the stored value can be set to S. ref = S max = S min = S(t cal In subsequent iterations where S(t) is determined in action 412, the minimum or maximum eigenvalue can be updated in action 414 as follows:

[0047] • If S(t) > S max Then S max Set it to S(t). Otherwise, S max constant

[0048] • If S(t) < S min Then S min Set it to S(t). Otherwise, S min constant

[0049] In this way, update S in action 414. min or S max This allows the upper and lower bounds of S(t) to be tracked over time as a new value of S(t) is determined in action 412.

[0050] Process 400 can then proceed to action 416, in which the range S can be determined. max – S min Is it greater than the threshold T? drift For example, combining Figure 3 The process described in 300 shows a threshold (e.g., T). drift The threshold can be the same for all motor speeds, or different thresholds can be used for different motor speeds. In some implementations, the threshold can change over time (e.g., the threshold can increase over time to allow for more sensor drift over time). In some implementations, the threshold can be reset at a reference time (e.g., at the beginning of recording sensor values, after calibrating a reference value for the sensor signal when there is a change in motor speed (e.g., P level). If the range S is determined in action 416... max – S min Not greater than the threshold T drift If the range is determined to be greater than a threshold in action 412, then process 400 can return to action 412, in which the value of S(t) can be calculated for the new observation time window. Actions 412, 414, and 416 can then be repeated until a reset / recalibration event occurs (e.g., a change in motor speed). If the range is determined to be greater than the threshold in action 416, sensor drift can be detected, and process 400 can proceed to action 418, in which actions can be performed to resolve the sensor drift, non-limiting examples of which are described herein. In example process 400, an indication of the detected sensor drift can be output as the action performed.

[0051] Figure 5 A process 500 of a second technique for detecting sensor drift in a sensor signal (e.g., a differential pressure signal) according to some embodiments of the present disclosure is illustrated. In some embodiments, the cardiac support system may be configured to store data associated with one or more sensor signals (e.g., real-time sensor data). In some embodiments, the cardiac support system may be additionally or alternatively configured to calculate and store derived data based on sensed (e.g., real-time) sensor data. For example, the system may be configured to calculate the minimum, maximum, and / or average values ​​of the differential pressure sensor signal within a specific time window (e.g., 1 minute), and the calculated values ​​of the statistical measurements may be logged in a log stored by the system. In this case, the average value of the differential pressure signal may be considered as the value MeanPlacement(t) in a series of averaged placement signals. In some embodiments, the averaged placement signal may be used as a feature for detecting drift in the differential pressure signal.

[0052] Process 500 can begin in action 510, where the average placement signal MeanPlacement(t) is received (e.g., by accessing a log with stored average placement signals via a controller). Process 500 can then proceed to action 514, where the maximum value (MP) of the average placement signal can be updated based on the received average placement signal MeanPlacement(t). max The minimum value of the sum (MP) min As described in action 314 of process 300, the minimum eigenvalue (in this case, MP) can be stored. min ) and the largest eigenvalue (MP in this case) max Furthermore, when a new characteristic value (e.g., MeanPlacement(t)) is determined, if the newly determined characteristic value is less than the stored minimum value or greater than the stored maximum value, the minimum and maximum characteristic values ​​can be updated. Additionally, starting from a reference time (e.g., at the beginning of recording sensor values, or after calibrating the reference value of the sensor signal when there is a change in motor speed (e.g., P level), the minimum characteristic value (e.g., MP) can be updated. min ) and the largest eigenvalue (e.g., MP) max Initialize them to the same value. For example, the stored value can be set to MP. ref = MP max = MP min = MeanPlacement(t cal In subsequent iterations, the minimum or maximum eigenvalue can be updated in action 512 as follows:

[0053] • If MeanPlacement(t) > MP max Then MP max Set to MeanPlacement(t). Otherwise, MP max constant

[0054] • If MeanPlacement(t) < MP min Then MP min Set to MeanPlacement(t). Otherwise, MP min constant

[0055] In this way, update MP in action 512. min or MP max This allows the upper and lower bounds of MeanPlacement(t) to be tracked over time as a new value of MeanPlacement(t) is received in action 510.

[0056] Process 500 can then proceed to action 514, in which the range MP can be determined. max – MP min Is it greater than the threshold T? MP For example, combining Figure 3 The process described in 300 shows a threshold (e.g., T). MP The threshold can be the same for all motor speeds, or different thresholds can be used for different motor speeds. In some implementations, the threshold can be changed over time (e.g., the threshold can be increased over time to allow more sensor drift over time). In some implementations, the threshold can be reset at a reference time (e.g., at the beginning of recording sensor values, after calibrating a reference value for the sensor signal when there is a change in motor speed (e.g., P level). If the range MP is determined in action 514... max – MP min Not greater than the threshold T MP Then process 500 can return to action 510, in which the value of MeanPlacement(t) can be received for a new observation time window. Actions 510, 512, and 514 can then be repeated until a range greater than a threshold is determined in action 514, or until a reset / recalibration event occurs (e.g., a change in motor speed). If a range greater than the threshold is determined in action 514, sensor drift can be detected, and process 500 can proceed to action 516, in which actions can be performed to resolve the sensor drift, non-limiting examples of which are described herein. In example process 500, an indication of the detected sensor drift can be output as the action performed.

[0057] Figure 6A An example of the average placement signal of a differential pressure (dP) sensor over a 2-day period is shown in the figure. Figure 6B Examples are shown in the context of... Figure 6A The graph shown is a curve of the average motor current over the same time period. (Example:) Figure 6A As shown, the average placement signal drifts significantly over a 2-day period, while Figure 6B The average motor current shown remains relatively constant at a constant motor speed.

[0058] Figure 6A The graph in the figure shows the curves based on Figure 5 The process shown in 500 determines the average placement signal (MeanPlacement(t)) as a function of time, and the maximum eigenvalue (MP). max ) and minimum eigenvalue (MP) min ). Figure 6AThe threshold (T) is also shown. MP 610. In Figure 6A In the example shown, the threshold is constant for the two motor speeds illustrated in the figure. In some implementations, as described herein, the threshold may change as the motor speed changes and / or over time. Figure 6A The defined range (MPa) of characteristics for each period within multiple observation time windows is also shown. max - MP min 612, where the height of the vertical bar in the figure represents the size of the range. As described in action 514 of reference process 500, sensor drift is detected when the size of the range exceeds a threshold.

[0059] Figure 6A This paper illustrates a conventional method of manual calibration relative to a reference value at which the user notices a difference and initiates a pressure signal, using the techniques described herein to detect sensor drift earlier. For example, as Figure 6A As shown, sensor drift is detected at time 618, prior to time 620 when user-initiated manual calibration is performed. As another example, sensor drift is detected at time 628, prior to time 630 when user-initiated manual calibration is performed. By detecting sensor drift earlier than is typically achieved using conventional methods, some embodiments of this disclosure can take action to address sensor drift in a more timely manner (e.g., by performing automated calibration routines and / or notifying the user of sensor drift). This can result in the cardiac support device providing more accurate information to the user, thereby improving patient care.

[0060] Therefore, having described several aspects and embodiments of the technology set forth in this disclosure, it should be understood that various changes, modifications, and improvements will readily occur to those skilled in the art. Such changes, modifications, and improvements are intended to fall within the spirit and scope of the technology described herein. For example, those skilled in the art will readily conceive of various other means and / or structures for performing functions and / or obtaining results and / or one or more advantages described herein, and such changes and / or modifications are considered to fall within the scope of the embodiments described herein. Those skilled in the art will recognize, or be able to determine, various equivalents of the specific embodiments described herein using only conventional experimentation. Therefore, it should be understood that the foregoing embodiments are presented by way of example only, and embodiments of the invention may be practiced in ways other than those specifically described within the scope of the appended claims and their equivalents. Furthermore, any combination of such features, systems, articles, materials, kits, and / or methods is included within the scope of this disclosure if two or more features, systems, articles, materials, kits, and / or methods described herein do not contradict each other.

[0061] The embodiments described above can be implemented in any of a variety of ways. One or more aspects and embodiments of this disclosure relating to the execution of processes or methods can be executed or controlled using program instructions executable by a device (e.g., a computer, processor, or other device). In this regard, various inventive concepts can be embodied in a computer-readable storage medium (or multiple computer-readable storage media) (e.g., computer memory, one or more floppy disks, optical disks, magnetic tapes, flash memory, circuit configurations in field-programmable gate arrays or other semiconductor devices, or other tangible computer storage media) encoded with one or more programs, which, when executed on one or more computers or other processors, perform methods implementing one or more embodiments of the various embodiments described above. One or more computer-readable media may be transportable such that one or more programs stored thereon can be loaded onto one or more different computers or other processors to implement various aspects of the aspects described above. In some embodiments, the computer-readable medium may be a non-transitory medium.

[0062] The embodiments described above in this technology can be implemented in any of a variety of ways. For example, the embodiments can be implemented using hardware, software, or a combination thereof. When implemented in software, the software code can execute on any suitable processor or set of processors, whether provided in a single computer or distributed across multiple computers. It should be understood that any component or set of components that performs the functions described above can generally be considered as a controller that controls the functions described above. The controller can be implemented in a variety of ways, such as with dedicated hardware or general-purpose hardware (e.g., one or more processors), which is programmed using microcode or software to perform the functions listed above, and when the controller corresponds to multiple components of a system, it can be implemented in a variety of combinations.

[0063] Furthermore, it should be understood that a computer can be embodied in any of a variety of forms, such as rack-mounted computers, desktop computers, laptop computers, or tablet computers, as non-limiting examples. Additionally, a computer can be embedded in a device that is not typically considered a computer but has suitable processing capabilities, including personal digital assistants (PDAs), smartphones, or any other suitable portable or stationary electronic device.

[0064] In addition, a computer may have one or more input and output devices. These devices are particularly useful for presenting a user interface. Examples of output devices that can be used to provide a user interface include a printer or display screen for visual presentation of output, and a speaker or other sound-generating device for audible presentation of output. Examples of input devices that can be used for a user interface include keyboards and pointing devices such as mice, touchpads, and digital tablets. Furthermore, a computer may receive input information through voice recognition or in other audible formats.

[0065] Such computers can be interconnected through one or more suitable networks, including local area networks (LANs) or wide area networks (WANs), such as enterprise networks, intelligent networks (INs), or the Internet. These networks can be based on any suitable technology and can operate according to any suitable protocol, and may include wireless networks, wired networks, or fiber optic networks.

[0066] Additionally, as described, some aspects can be embodied as one or more methods. Actions performed as part of a method can be ordered in any suitable manner. Therefore, implementations in which actions are performed in an order different from the illustrative order can be constructed, which may include performing several actions simultaneously, even if these actions are shown as sequential actions in the illustrative implementation.

[0067] All definitions defined and used herein should be understood to take precedence over dictionary definitions, definitions in referenced documents, and / or the general meaning of the defined terms.

[0068] Unless explicitly stated to the contrary, the indefinite articles “a” and “an” as used herein in the specification and claims shall be understood to mean “at least one”.

[0069] As used herein in the specification and claims, the phrase “and / or” should be understood to mean “any one or both” of the elements so combined, that is, elements that exist in combination in some cases and separately in others. Multiple elements listed with “and / or” should be interpreted in the same way, that is, “one or more” of the elements so combined. In addition to the elements specifically identified by the “and / or” clause, other elements may optionally exist, whether related to or unrelated to those specifically identified. Thus, as a non-limiting example, when used in conjunction with open-ended language such as “comprising,” reference to “A and / or B” may in one embodiment refer only to A (optionally including elements other than B); in another embodiment, only to B (optionally including elements other than A); in yet another embodiment, both A and B (optionally including other elements); and so on.

[0070] As used herein in the specification and claims, with respect to a list of one or more elements, the phrase “at least one” should be understood to mean at least one element selected from any one or more elements in the list of elements, but does not necessarily include at least one of each element specifically listed in the list of elements, and does not exclude any combination of elements in the list of elements. This definition also allows for the optional presence of other elements besides those specifically identified in the list of elements referred to by the phrase “at least one,” whether or not these elements are related to those specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or equivalently, “at least one of A or B”, or equivalently, “at least one of A and / or B”) in one embodiment may refer to at least one A, optionally including more than one A but without B (and optionally including elements other than B); in another embodiment, it may refer to at least one B, optionally including more than one B but without A (and optionally including elements other than A); in yet another embodiment, it may refer to at least one A, optionally including more than one A, and at least one B, optionally including more than one B (and optionally including other elements); and so on.

[0071] Furthermore, the wording and terminology used herein are for descriptive purposes and should not be considered restrictive. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof in this document is intended to cover the items listed thereafter and their equivalents, as well as any additional items.

[0072] In the claims and the description above, all transitional phrases (such as "comprising," "including," "carrying," "having," "containing," "involving," "holding," "constituting," etc.) should be understood as open-ended, that is, meaning including but not limited to. Only the transitional phrases "constituting of" and "constituting substantially of" are respectively closed or semi-closed transitional phrases.

[0073] The use of ordinal terms such as “first,” “second,” and “third” in the claims to modify a claim element does not imply any priority, precedence, or order of one claim element relative to another, or the chronological order of the actions of the method. Rather, it serves only as a label to distinguish one claim element with a specific name from another element with the same name (but using ordinal terms), thereby differentiating the claim elements.

Claims

1. A method for detecting sensor drift associated with a pressure sensor of a heart pump, the method comprising: Receive pressure signals from pressure sensors arranged on the heart pump; Determine the characteristics of the pressure signal within a time window; The minimum or maximum feature value is updated at least in part based on the features within the time window; Determine whether the range of the feature is greater than a threshold, wherein the range is determined as the difference between the minimum feature value and the maximum feature value; as well as An action is performed when the range of the feature is determined to be greater than the threshold.

2. The method according to claim 1, wherein the pressure sensor includes a differential pressure sensor.

3. The method of claim 2, wherein the heart pump is inserted across the pulmonary valve of the patient's heart, and the pressure signal is a differential pressure signal across the pulmonary valve.

4. The method according to any one of claims 1 to 3, wherein determining the characteristics within a time window of the pressure signal comprises: The features are determined using a random phase approximation technique.

5. The method according to any one of claims 1 to 3, wherein determining the characteristics within a time window of the pressure signal comprises: Calculate the sum of the pressure signal values ​​within the time window of the pressure signal.

6. The method according to claim 5, further comprising: The minimum eigenvalue and the maximum eigenvalue are initialized to the same value. Updating the minimum eigenvalue and / or the maximum eigenvalue based at least in part on the features includes: When the sum is less than the minimum eigenvalue, the minimum eigenvalue is updated to the sum, or When the sum is greater than the maximum eigenvalue, the maximum eigenvalue is updated to the sum.

7. The method according to any one of claims 1 to 3, wherein performing the action when determining that the range of the feature is greater than the threshold comprises: An alarm should be issued to recalibrate the reference value of the pressure signal.

8. The method of claim 7, wherein outputting an alarm for the reference value of the pressure signal that should be recalibrated comprises: The alarm is displayed on the monitor.

9. The method according to any one of claims 1 to 3, wherein performing the action comprises: Recalibrate the reference value of the pressure signal.

10. The method according to claim 1, further comprising: The threshold is determined at least in part based on the motor speed associated with the motor of the heart pump.

11. The method of claim 1, wherein the pressure signal is associated with a reference value, and wherein the method further comprises: Determine the predetermined amount of time that has elapsed since the last calibration of the reference value; as well as The action is performed when the range of the feature is determined to be greater than the threshold and after the predetermined amount of time has elapsed.

12. The method according to any one of claims 1 to 3, wherein determining the characteristics within a time window of the pressure signal comprises: Determine the average value of the pressure signal within the time window of the pressure signal.

13. The method of claim 12, further comprising: The minimum eigenvalue and the maximum eigenvalue are initialized to the same value. Updating the minimum eigenvalue and / or the maximum eigenvalue based at least in part on the features includes: When the average value is less than the minimum eigenvalue, the minimum eigenvalue is updated to the average value, or When the average value is greater than the maximum eigenvalue, the maximum eigenvalue is updated to the average value.

14. The method of claim 13, wherein performing the action when determining that the range of the feature is greater than the threshold comprises: An alarm should be issued to recalibrate the reference value of the pressure signal.

15. The method of claim 14, wherein outputting an alarm for the reference value of the pressure signal that should be recalibrated comprises: The alarm is displayed on the monitor.

16. The method of claim 13, wherein performing the action comprises: Recalibrate the reference value of the pressure signal.

17. The method of claim 12, wherein the length of the time window is one minute.

18. A heart pump system, comprising: A heart pump, the heart pump including a pressure sensor configured to sense pressure within a portion of a patient's heart; and The controller is configured to: Receive pressure signals from the pressure sensor; Determine the characteristics of the pressure signal within a time window; The minimum or maximum feature value is updated at least in part based on the features within the time window; Determine whether the range of the feature is greater than a threshold, wherein the range is determined as the difference between the minimum feature value and the maximum feature value; as well as An action is performed when the range of the feature is determined to be greater than the threshold.

19. The heart pump system of claim 18, wherein the pressure sensor comprises a differential pressure sensor.

20. The heart pump system of claim 19, wherein the heart pump is configured to be inserted across the pulmonary valve of the patient's heart, and the pressure signal is a differential pressure signal across the pulmonary valve.

21. The cardiac pump system according to any one of claims 18 to 20, wherein determining the characteristics within a time window of the pressure signal comprises: The features are determined using a random phase approximation technique.

22. The cardiac pump system according to any one of claims 18 to 20, wherein determining the characteristics within a time window of the pressure signal comprises: Calculate the sum of the pressure signal values ​​within the time window of the pressure signal.

23. The heart pump system of claim 22, wherein the controller is further configured to: The minimum eigenvalue and the maximum eigenvalue are initialized to the same value. Updating the minimum eigenvalue and / or the maximum eigenvalue based at least in part on the features includes: When the sum is less than the minimum eigenvalue, the minimum eigenvalue is updated to the sum, or When the sum is greater than the maximum eigenvalue, the maximum eigenvalue is updated to the sum.

24. The heart pump system according to any one of claims 18 to 20, wherein performing the action when determining that the range of the characteristic is greater than the threshold comprises: An alarm should be issued to recalibrate the reference value of the pressure signal.

25. The heart pump system of claim 24, wherein the alarm outputting the reference value of the pressure signal that should be recalibrated comprises: The alarm is displayed on the monitor.

26. The cardiac pump system according to any one of claims 18 to 20, wherein the action comprises: Recalibrate the reference value of the pressure signal.

27. The heart pump system of claim 18, wherein the controller is further configured to: The threshold is determined at least in part based on the motor speed associated with the motor of the heart pump.

28. The heart pump system of claim 18, wherein the pressure signal is associated with a reference value, and wherein the controller is further configured to: Determine the predetermined amount of time that has elapsed since the last calibration of the reference value; and The action is performed when the range of the feature is determined to be greater than the threshold and after the predetermined amount of time has elapsed.

29. The cardiac pump system according to any one of claims 18 to 20, wherein determining the characteristics within a time window of the pressure signal comprises: Determine the average value of the pressure signal within the time window of the pressure signal.

30. The heart pump system of claim 29, wherein the controller is further configured to: The minimum eigenvalue and the maximum eigenvalue are initialized to the same value. Updating the minimum eigenvalue and / or the maximum eigenvalue based at least in part on the features includes: When the average value is less than the minimum eigenvalue, the minimum eigenvalue is updated to the average value, or When the average value is greater than the maximum eigenvalue, the maximum eigenvalue is updated to the average value.

31. The heart pump system of claim 30, wherein performing the action when determining that the range of the feature is greater than the threshold comprises: An alarm should be issued to recalibrate the reference value of the pressure signal.

32. The heart pump system of claim 31, wherein the alarm outputting the reference value of the pressure signal that should be recalibrated comprises: The alarm is displayed on the monitor.

33. The heart pump system of claim 31, wherein the action includes: Recalibrate the reference value of the pressure signal.

34. The heart pump system of claim 29, wherein the length of the time window is one minute.

35. A controller for a heart pump system, the controller comprising: At least one hardware processor, said at least one hardware processor being configured to: Receive pressure signals from pressure sensors located on the heart pump of the heart pump system; Determine the characteristics of the pressure signal within a time window; The minimum or maximum feature value is updated at least in part based on the features within the time window; Determine whether the range of the feature is greater than a threshold, wherein the range is determined as the difference between the minimum feature value and the maximum feature value; as well as An action is performed when the range of the feature is determined to be greater than the threshold.

36. The controller of claim 35, wherein the pressure sensor comprises a differential pressure sensor.

37. The controller of claim 36, wherein the heart pump is configured to insert across the pulmonary valve of the patient's heart, and the pressure signal is a differential pressure signal across the pulmonary valve.

38. The controller according to any one of claims 35 to 37, wherein determining the characteristics within the time window of the pressure signal comprises: The features are determined using a random phase approximation technique.

39. The controller according to any one of claims 35 to 37, wherein determining the characteristics within the time window of the pressure signal comprises: Calculate the sum of the pressure signal values ​​within the time window of the pressure signal.

40. The controller of claim 39, wherein the at least one hardware processor is further configured to: The minimum eigenvalue and the maximum eigenvalue are initialized to the same value. Updating the minimum eigenvalue and / or the maximum eigenvalue based at least in part on the features includes: When the sum is less than the minimum eigenvalue, the minimum eigenvalue is updated to the sum, or When the sum is greater than the maximum eigenvalue, the maximum eigenvalue is updated to the sum.

41. The controller according to any one of claims 35 to 37, wherein performing the action when determining that the range of the feature is greater than the threshold comprises: An alarm should be issued to recalibrate the reference value of the pressure signal.

42. The controller of claim 41, wherein the alarm outputting the reference value of the pressure signal that should be recalibrated comprises: The alarm is displayed on the monitor.

43. The controller according to any one of claims 35 to 37, wherein performing the action comprises: Recalibrate the reference value of the pressure signal.

44. The controller of claim 35, wherein the at least one hardware processor is further configured to: The threshold is determined at least in part based on the motor speed associated with the motor of the heart pump.

45. The controller of claim 35, wherein the pressure signal is associated with a reference value, and wherein the at least one hardware processor is further configured to: Determine the predetermined amount of time that has elapsed since the last calibration of the reference value; and The action is performed when the range of the feature is determined to be greater than the threshold and after the predetermined amount of time has elapsed.

46. ​​The controller according to any one of claims 35 to 37, wherein determining the characteristics within the time window of the pressure signal comprises: Determine the average value of the pressure signal within the time window of the pressure signal.

47. The controller of claim 46, wherein the at least one hardware processor is further configured to: The minimum eigenvalue and the maximum eigenvalue are initialized to the same value. Updating the minimum eigenvalue and / or the maximum eigenvalue based at least in part on the features includes: When the average value is less than the minimum eigenvalue, the minimum eigenvalue is updated to the average value, or When the average value is greater than the maximum eigenvalue, the maximum eigenvalue is updated to the average value.

48. The controller of claim 47, wherein performing the action when determining that the range of the feature is greater than the threshold comprises: An alarm should be issued to recalibrate the reference value of the pressure signal.

49. The controller of claim 48, wherein outputting an alarm that requires recalibrating the reference value of the pressure signal comprises: The alarm is displayed on the monitor.

50. The controller of claim 47, wherein performing the action includes: Recalibrate the reference value of the pressure signal.

51. The controller of claim 46, wherein the length of the time window is one minute.

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