Method and system for determining the position of the cardiac pump

Abstract

A method and apparatus for determining the position of the cardiac pump within a patient's heart is described. An intravascular blood pump designed for right ventricular support may extend through and into the pulmonary artery to pump blood into the pulmonary artery. To properly position a right ventricular support device, the device may be made to pass through the inferior vena cava, right atrium, tricuspid valve, right ventricle, and finally, the pulmonary valve. Proper positioning of the intravascular blood pump across the pulmonary valve is important to ensure that the pump operates as intended. The method described herein includes receiving a pressure signal from at least one pressure sensor arranged on the cardiac pump, generating a histogram of values ​​observed within a time window associated with the pressure signal, and determining the position of the cardiac pump at least in part based on the form of the histogram.

Description

Technical Field

[0001] The present disclosure relates to a technique for determining the positioning of a heart pump.

Background Art

[0002] Fluid pumps such as blood pumps are used in 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 blood vessels, i.e., veins and / or arteries, to a location within the patient's heart or to any location within the patient's circulatory system. For example, an intravascular blood pump can be inserted via a catheter and positioned to straddle one or more heart valves. An intravascular blood pump is typically disposed at the end of a catheter. Once in place, the pump is used to assist the heart and pump blood through the circulatory system, and thus can temporarily reduce the load on the patient's heart, such as to enable the heart to recover after a heart attack. An exemplary intravascular blood pump is available from ABIOMED, Inc. (Danvers, MA) under the trade name Impella® Heart Pump.

[0003] An intravascular blood pump is typically connected to an individual external heart pump controller that controls the heart pump, such as motor speed, and collects and displays operating data about the blood pump, such as heart signal level, battery temperature, blood flow rate, and tubing integrity. An exemplary heart pump controller is available from ABIOMED, Inc. under the trade name Automated Impella Controller®. In some cases, the controller can issue an alarm when an operating data value is outside a predetermined value or range, e.g., when a leak, suction, and / or pump failure is detected. The controller can include a video display screen, and a graphical user interface configured to display the operating data and / or alarm is presented thereon.

Summary of the Invention

Means for Solving the Problems

[0004] An intravascular blood pump designed for right ventricular support may extend through and into the pulmonary artery to pump blood into the pulmonary artery. To properly position a right ventricular support device, the device may be made to pass through the inferior vena cava, right atrium, tricuspid valve, right ventricle, and finally, the pulmonary valve. Proper positioning of the intravascular blood pump across the pulmonary valve is crucial to ensure that the pump operates as intended. Described herein are systems and methods for determining the position of an intravascular blood pump, at least in part, based on the analysis of pressure signals received from pressure sensors located on the pump. While the techniques described herein are used to determine the position of a blood pump configured to provide right ventricular support, it should be understood that at least some of the techniques may also be used to determine the position of a blood pump inserted across the aortic valve on the left side of the heart.

[0005] In one aspect, a method for determining the location of the cardiac pump within a patient's heart is provided. The method includes receiving a pressure signal from at least one pressure sensor arranged on the cardiac pump, generating a histogram of values ​​observed within a time window associated with the pressure signal, and determining the location of the cardiac pump at least in part based on the form of the histogram.

[0006] In another aspect, at least one pressure sensor is a differential pressure sensor. In another aspect, the length of the time window is at least 4 seconds and less than 10 seconds. In another aspect, the length of the time window is at least 5 seconds and less than 7 seconds.

[0007] In another aspect, the method further includes filtering the pressure signal and generating a filtered pressure signal, and generating a histogram of the values ​​includes generating a histogram of the values ​​observed within a time window of the filtered pressure signal. In another aspect, filtering the pressure signal includes filtering the pressure signal using a finite impulse response (FIR) filter.

[0008] In another aspect, determining the location of the heart pump based at least partially on the morphology of the histogram includes determining the location of the heart pump based at least partially on the distribution of the histogram. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram includes determining whether the distribution is bimodal. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram further includes determining whether the heart pump is not properly located when the histogram has a bimodal distribution. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram further includes determining whether the distribution is normal. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram further includes determining whether the heart pump is properly located when the histogram has a normal distribution.

[0009] In another aspect, determining the position of the heart pump based at least partially on the morphology of the histogram includes determining the standard deviation of the values ​​in a time window, defining subwindows in the time window based at least partially on the standard deviation, and determining the position of the heart pump based at least partially on the values ​​in the subwindows. In another aspect, determining the position of the heart pump based at least partially on the values ​​in the subwindows includes calculating a first sum of all the values ​​in the subwindows, calculating a second sum of all the values ​​in the time window, dividing the first sum by the second sum to determine a morphological index value, determining that the heart pump is not properly positioned when the morphological index value is below a threshold, and determining that the heart pump is properly positioned when the morphological index value is above a threshold.

[0010] In another aspect, the method further includes outputting an indication of the cardiac pump location via a user interface. In another aspect, the method further includes determining the pulsatileness of a pressure signal and generating a histogram of the values, which is performed in response to the pulsatileness of the pressure signal being above a first threshold pulsatile value and below a second threshold pulsatile value. In another aspect, the cardiac pump is configured to provide right ventricular assistance for the patient, and determining the location of the cardiac pump, at least in part based on the form of the histogram, includes determining whether the outlet of the cardiac pump is located within the patient's pulmonary artery.

[0011] In one aspect, a cardiac pump system is provided. The cardiac pump system includes a cardiac pump including at least one pressure sensor configured to sense pressure within a portion of a patient's heart, and a controller. The controller is configured to receive a pressure signal output from at least one pressure sensor, generate a histogram of values ​​observed within a time window associated with the pressure signal, and determine the position of the cardiac pump based at least in part on the form of the histogram.

[0012] In another aspect, at least one pressure sensor is a differential pressure sensor. In another aspect, the length of the time window is at least 4 seconds and less than 10 seconds. In another aspect, the length of the time window is at least 5 seconds and less than 7 seconds.

[0013] In another aspect, the controller is further configured to filter the pressure signal and generate a filtered pressure signal, and generating a histogram of the values ​​includes generating a histogram of the values ​​observed within a time window of the filtered pressure signal. In another aspect, filtering the pressure signal includes filtering the pressure signal using a finite impulse response (FIR) filter.

[0014] In another aspect, determining the location of the heart pump based at least partially on the morphology of the histogram includes determining the location of the heart pump based at least partially on the distribution of the histogram. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram includes determining whether the distribution is bimodal. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram further includes determining whether the heart pump is not properly located when the histogram has a bimodal distribution. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram further includes determining whether the distribution is normal. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram further includes determining whether the heart pump is properly located when the histogram has a normal distribution.

[0015] In another aspect, determining the position of the heart pump based at least partially on the morphology of the histogram includes determining the standard deviation of the values ​​in a time window, defining subwindows in the time window based at least partially on the standard deviation, and determining the position of the heart pump based at least partially on the values ​​in the subwindows. In another aspect, determining the position of the heart pump based at least partially on the values ​​in the subwindows includes calculating a first sum of all the values ​​in the subwindows, calculating a second sum of all the values ​​in the time window, dividing the first sum by the second sum to determine a morphological index value, determining that the heart pump is not properly positioned when the morphological index value is below a threshold, and determining that the heart pump is properly positioned when the morphological index value is above a threshold.

[0016] In another aspect, the controller is further configured to output an indication of the cardiac pump location via a user interface. In another aspect, the controller is further configured to determine the pulsatileness of the pressure signal, and generating a histogram of the values ​​is performed in response to the pulsatileness of the pressure signal being above a first threshold pulsatile value and below a second threshold pulsatile value. In another aspect, the cardiac pump is configured to provide right ventricular support for the patient, and determining the cardiac pump location, at least in part, based on the form of the histogram, includes determining whether the outlet of the cardiac pump is located within the patient's pulmonary artery.

[0017] In one aspect, a controller for a cardiac 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 output from at least one pressure sensor arranged on the cardiac pump of the cardiac pump system, generate a histogram of values ​​observed within a time window associated with the pressure signal, and determine the position of the cardiac pump at least in part based on the form of the histogram.

[0018] In another aspect, at least one pressure sensor is a differential pressure sensor. In another aspect, the length of the time window is at least 4 seconds and less than 10 seconds. In another aspect, the length of the time window is at least 5 seconds and less than 7 seconds.

[0019] In another aspect, at least one hardware processor is further configured to filter the pressure signal and produce a filtered pressure signal, and generating a histogram of the values ​​includes generating a histogram of the values ​​observed within a time window of the filtered pressure signal. In another aspect, filtering the pressure signal includes filtering the pressure signal using a finite impulse response (FIR) filter.

[0020] In another aspect, determining the location of the heart pump based at least partially on the morphology of the histogram includes determining the location of the heart pump based at least partially on the distribution of the histogram. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram includes determining whether the distribution is bimodal. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram further includes determining whether the heart pump is not properly located when the histogram has a bimodal distribution. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram further includes determining whether the distribution is normal. In another aspect, determining the location of the heart pump based at least partially on the distribution of the histogram further includes determining whether the heart pump is properly located when the histogram has a normal distribution.

[0021] In another aspect, determining the position of the heart pump based at least partially on the morphology of the histogram includes determining the standard deviation of the values ​​in a time window, defining subwindows in the time window based at least partially on the standard deviation, and determining the position of the heart pump based at least partially on the values ​​in the subwindows. In another aspect, determining the position of the heart pump based at least partially on the values ​​in the subwindows includes calculating a first sum of all the values ​​in the subwindows, calculating a second sum of all the values ​​in the time window, dividing the first sum by the second sum to determine a morphological index value, determining that the heart pump is not properly positioned when the morphological index value is below a threshold, and determining that the heart pump is properly positioned when the morphological index value is above a threshold.

[0022] In another aspect, at least one hardware processor is further configured to output an indication of the cardiac pump location via a user interface. In another aspect, at least one hardware processor is further configured to determine the pulsatileness of a pressure signal, and generating a histogram of values ​​is performed in response to the pulsatileness of the pressure signal being above a first threshold pulsatile value and below a second threshold pulsatile value. In another aspect, the cardiac pump is configured to provide right ventricular support for the patient, and determining the cardiac pump location, at least in part, based on the form of the histogram, includes determining whether the outlet of the cardiac pump is located within the patient's pulmonary artery.

[0023] In one aspect, a method is provided for determining the location of a right ventricular assist device within a patient's heart. The method includes receiving a pressure signal from at least one pressure sensor arranged adjacent to the outlet of the right ventricular assist device; generating a histogram of values ​​observed within a time window associated with the pressure signal; determining that the distribution of the histogram is bimodal; and, in response to determining that the distribution of the histogram is bimodal, outputting an indication that the outlet of the right ventricular assist device is not located in the patient's pulmonary artery.

[0024] In another aspect, at least one pressure sensor comprises a differential pressure sensor. In another aspect, the length of the time window is at least 4 seconds and less than 10 seconds. In another aspect, the length of the time window is at least 5 seconds and less than 7 seconds.

[0025] In another aspect, the method further comprises filtering a pressure signal and generating a filtered pressure signal, and generating a histogram of values comprises generating a histogram of values observed within a time window of the filtered pressure signal. In another aspect, filtering the pressure signal comprises filtering the pressure signal using a finite impulse response (FIR) filter.

[0026] In another aspect, determining that the distribution of the histogram is bimodal comprises determining a standard deviation of the values within the time window, defining a sub-window within the time window based at least in part on the standard deviation, and determining that the distribution of the histogram is bimodal based at least in part on the values within the sub-window. In another aspect, determining that the distribution of the histogram is bimodal based at least in part on the values within the sub-window comprises calculating a first sum of all the values within the sub-window, calculating a second sum of all the values within the time window, dividing the first sum by the second sum to determine a morphological index value, and determining that the distribution of the histogram is bimodal when the morphological index value is less than a threshold value.

[0027] In another aspect, the method further comprises determining the pulsatility of the pressure signal, and generating a histogram of values is performed in response to the pulsatility of the pressure signal exceeding a first threshold pulsatility value and falling below a second threshold pulsatility value.

Brief Description of the Drawings

[0028] [Figure 1A] FIG. 1A shows an exemplary heart assist device that may be used in conjunction with some embodiments.

[0029] [Figure 1B] FIG. 1B shows an exemplary cardiac assist system including the cardiac assist device of FIG. 1A.

[0030] [Figure 2] FIG. 2 is a flowchart of a process for determining the position of a cardiac assist device according to some embodiments.

[0031] [Figure 3] FIG. 3 is a flowchart of a process for determining a morphological index associated with a pressure signal waveform according to some embodiments.

[0032] [Figure 4] FIG. 4 schematically illustrates a process for analyzing the morphology of a histogram associated with a pressure signal according to some embodiments.

DETAILED DESCRIPTION OF THE INVENTION

[0033] Detailed Description Determining that a cardiac assist device (e.g., an intravascular blood pump) is properly positioned within a patient's heart during its operation can be crucial to ensuring the pump provides adequate cardiac assistance to the patient. As described herein, a cardiac assist device may include one or more pressure sensors configured to sense pressure within a patient's heart when the device is operating. For example, one or more pressure sensors may include optical pressure sensors and / or differential pressure sensors configured to sense a pressure difference across one or more valves through which the cardiac assist device is inserted. Positioning of a cardiac assist device inserted across the aortic valve to provide left ventricular assistance for a patient may be determined at least in part by evaluating the pulsatility of the pressure signals sensed by one or more pressure sensors on the device. The inventors recognize and understand that, in some cases, pulsatility measurements used to determine the positioning of a left ventricular assist device may not be used to provide a reliable positioning determination when the cardiac assist device is used to provide right ventricular assistance. For example, since the pumping of blood through the right side of the heart generally produces a pressure signal with less pulsation compared to the pulsation of the pressure signal measured when blood is pumped through the left side of the heart, determining the position of the right ventricular assist system solely on or based on the pulsation of the pressure signal may not lead to accurate positioning results. For this purpose, some embodiments of the present disclosure relate to novel techniques for determining the position of a cardiac assist system (e.g., a right ventricular assist system) based at least in part on a morphological index associated with a pressure signal.

[0034] Figure 1A shows an illustrative embodiment of a blood pump assembly 100 according to the present disclosure. 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-traumatic extension 102, a catheter 112, an inlet region 110, an outlet region 106, and a blood drainage opening 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 located toward the distal end 107 of the cannula 108. The inlet region 110 may include a pump housing 103 having a peripheral wall 111 extending about the rotation axis of the impeller blades, the peripheral wall 111 positioned radially outward from the inner surface with respect to the rotation axis of the impeller. The impeller may be rotatably coupled to the pump 101 in the inlet region 110 adjacent to a blood discharge opening 117 formed within the peripheral wall 111 of the pump housing 103. The pump housing 103 may be made of metal, according to several implementations. A non-traumatic extension 102, also called a "pigtail," may be connected to the distal end 107 of the cannula 108 and may help stabilize the blood pump assembly 100 and / or position it correctly within the heart. The non-traumatic extension 102 may be configured in a straight configuration or a partially curved configuration. The non-traumatic extension 102 may be made of a flexible material, at least partially, and may have dual rigidity. It should be understood that some embodiments of the pump assembly do not need to include the non-traumatic extension 102.

[0035] The cannula 108 may have a shape that matches (or resembles) the biostructure of the patient's right ventricle. In the exemplary embodiment shown in Figure 1A, the cannula has a proximal end 105 positioned near the patient's inferior vena cava and a distal end 107 positioned near the pulmonary artery. The cannula 108 may include a first compartment Sl 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 compartment S2 extending from point C between the inlet region 110 and the outlet region 106 to the outlet region 106. In some implementations, points B and C may be located in the same place along the cannula 108. The first compartment Sl of the cannula may form an "S" shape in a first plane. In some implementations, the compartment Sl may have a curvature of 30 to 180 degrees. The second compartment S2 of the cannula may form an "S" shape in the second plane. In some implementations, compartment S2 can have a curvature of 30 to 180 degrees (e.g., 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, or 170°). The second plane may differ from the first plane. In some implementations, the second plane may be parallel to or the same as the first plane.

[0036] While shown with an "S" shape, it should be understood that other implementations of the blood pump assembly may be formed with other shapes (e.g., a "U" shape) or without any shape at all when outside the body. In such implementations, the cannula may be formed from a flexible material so that it can bend during insertion and achieve the desired shape when it comes inside the patient's heart.

[0037] In some implementations, the blood pump assembly 100 can be percutaneously inserted into the right ventricle through the internal jugular vein, through the right atrium. 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 discharge opening 117 of the pump housing 103 positioned in the pulmonary artery. Alternatively, in some implementations, the blood pump assembly 100 can be percutaneously inserted into the left ventricle through the femoral artery, delivering blood from the left ventricle into the aorta.

[0038] Figure 1B shows that the blood pump assembly 100 may form part of a cardiac assist system 120. The cardiac assist system 120 may also include a controller 130 (e.g., an Automated Impella Controller®, referred to herein as "AIC," manufactured by ABIOMED, ​​Inc., Danvers, Mass.), a display 140, a purge subsystem 150, a connector cable 160, a plug 170, and a repositioning unit 180. As shown, the controller 130 may include a display 140. The controller 130 may be configured to monitor and control the operation of the blood pump assembly 100. During operation, the purge subsystem 150 may be configured to deliver purge fluid to the blood pump assembly 100 through a catheter 112 to prevent blood from entering the motor of the cardiac pump (not shown). In some implementations, the purge fluid is a glucose solution (e.g., 5% glucose in water with 25 or 50 IU / mL heparin, although the solution does not necessarily have to contain heparin in all embodiments). A connector cable 160 may provide an electrical connection between the blood pump assembly 100 and the controller 130. A plug 170 may connect the catheter 112, the purge subsystem 150, and the connector cable 160. In some implementations, the plug 170 may include a storage device (e.g., memory) configured to store, for example, operating parameters, to facilitate patient transfer to another controller if necessary. A repositioning unit 180 may 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).

[0039] As shown in Figure 1B, in some embodiments, the cardiac support system 120 may include a purge subsystem 150 having a container 151, a supply line 152, a purge cassette 153, a purge disc 154, purge 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. As understood, in other embodiments, the cardiac support system 120 may not include the purge subsystem. In some embodiments, the purge fluid may be stored in the container 151. The supply line 152 may provide a fluid connection between the container 151 and the purge cassette 153. The purge cassette 153 may control how the purge fluid in the container 151 is delivered to the blood pump assembly 100. For example, the purge cassette 153 may include one or more valves to control the pressure and / or flow rate of the purge fluid. The purge disc 154 may include one or more pressure and / or flow sensors to measure the pressure and / or flow rate of the purge fluid. As shown, the controller 130 may include the purge cassette 153 and the purge disc 154. Purge tubing 155 may provide a fluid connection between the purge disc 154 and the check valve 156. A pressure reservoir 157 may provide additional filling volume during purge fluid exchange. In some implementations, the pressure reservoir 157 may include a flexible rubber diaphragm with an expansion chamber to provide additional filling volume. An infusion filter 158 may help prevent bacterial contamination and air from entering the catheter 112. A side arm 159 may provide a fluid connection between the infusion filter 158 and the plug 170. Although shown to have separate purge tubing and connector cables, it should be understood that in some embodiments, the cardiac support system 120 may include a single connector having both fluid and electrical lines connectable to the controller 130.

[0040] During operation, the controller 130 may be configured to receive measurements from one or more pressure sensors (not shown) included as part of the blood pump assembly 100 and purge disk 154. The controller 130 may also be configured to control the operation of the motors (not shown) of the blood pump assembly 100 and purge cassette 153. In some embodiments, the controller 130 may be configured to control and measure the pressure and / or flow rate of the purge fluid via the purge cassette 153 and purge disk 154. During operation, after exiting the purge subsystem 150 through the side arm 159, the purge fluid may be guided through a purge lumen (not shown) in the catheter 112 and plug 170. The catheter 112, connector cable 160, and sensor cable (not shown) in the plug 170 may provide electrical connections between components of the blood pump assembly 100 (e.g., one or more pressure sensors) and the controller 130. A catheter 112, a connector cable 160, and a motor cable (not shown) within a plug 170 may provide an electrical connection between the motor of the blood pump assembly 100 and the controller 130. During operation, the controller 130 may be configured to receive measurements from one or more pressure sensors of the blood pump assembly 100 through a sensor cable (e.g., optical fiber) and to control the power delivered to the motor of the blood pump assembly 100 through the motor cable. By controlling the power delivered to the motor of the blood pump assembly 100, the controller 130 may be operable to control the speed of the motor.

[0041] Various modifications can be made to the cardiac assist system 120 and one or more of its components. For example, one or more additional sensors may be added to the blood pump assembly 100. In another embodiment, a signal generator may 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. In yet another embodiment, one or more components of the cardiac assist system 120 may be isolated. For example, the display 140 may be incorporated into another device that communicates with the controller 130 (e.g., wirelessly or through one or more electrical cables).

[0042] As described herein, a cardiac pump (e.g., a blood pump assembly 100) may include a pressure sensor (e.g., an optical pressure sensor) configured to detect the pressure near the outlet of the cardiac pump from which blood is pumped. For example, when a right cardiac assist device is properly positioned, the outlet of the cardiac pump may be positioned within the pulmonary artery of the patient's heart, and the pressure sensor may measure the pressure within the pulmonary artery. The pressure signal sensed by the 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 the blood flow rate through the cardiac pump when it is operating. For example, the pressure signal may be used in combination with a motor current signal received from a motor current sensor (not shown) and a set of stored values ​​for determining the blood flow rate through the cardiac pump. With respect to a right cardiac assist device, the differential pressure between the right atrium and the pulmonary artery may also be determined indirectly based on a pressure signal measuring the pressure within the pulmonary artery and a set of stored values. Alternatively, the differential pressure between the right atrium and the pulmonary artery can be determined using multiple pressure sensors, one located in the inflow region of the cardiac pump and another in the outflow region.

[0043] As described herein, pressure signals sensed by pressure sensors of a cardiac pump located within the right side of the heart may be weaker than the corresponding pressure signals when the cardiac pump is located within the left side of the heart. Therefore, some conventional techniques for determining the positioning of left-sided cardiac assist devices, such as determining positioning based on whether the pulsatileness of the pressure signal is above or below a threshold pulsatile value, may not function well for determining the positioning of right-sided cardiac assist devices.

[0044] Figure 2 illustrates a process 200 for determining the position of the cardiac pump within a patient's heart, based at least in part on the form of a pressure signal, according to some embodiments of the present disclosure. In action 210, the pressure signal may be received from a pressure sensor of the cardiac pump. For example, the pressure signal may be received by a controller (e.g., controller 130) coupled to the pressure sensor of the cardiac pump. In some embodiments, the pressure signal may be a differential pressure signal representing the pressure difference between the right atrium (e.g., central venous pressure) and the pulmonary artery when the cardiac pump is properly positioned within the right side of the heart. Alternatively, when the cardiac pump is not properly positioned within the right side of the heart, the differential pressure signal may represent the pressure difference between the right atrium and the right ventricle. Some embodiments of the present disclosure relate to techniques for analyzing the differential pressure signal and distinguishing a “good” position of the cardiac pump (e.g., when the outlet of the cardiac pump is in the pulmonary artery) from a “bad” position (e.g., when the outlet of the cardiac pump is in the right ventricle).

[0045] After receiving a pressure signal, process 200 may proceed to act 212, in which a histogram distribution of values ​​observed within a time window of the received pressure signal is calculated. For example, the received pressure signal may be continuously received by a controller, and the values ​​of the pressure signal within a specific time window (e.g., 5 seconds) may be used to generate a histogram of values ​​within the time window. An example of such a histogram 400 is shown in Figure 4. In some embodiments, pulsation information associated with the received pressure signal may be used in act 212 to determine when and / or whether a histogram distribution of values ​​should be calculated. For example, as shown in Figure 2, the pulsation of the pressure signal within a time window may be determined, and when it is determined in act 211 that the pulsation is less than a first threshold pulsation value, it may be determined in act 212 not to calculate the histogram distribution, and process 200 may terminate. In some embodiments, the pulsatility of the pressure signal may be compared to a second threshold pulsatility value, and if the pulsatility associated with the pressure signal exceeds the second threshold pulsatility value in action 213, this may indicate that the patient is moving, and it may be decided not to calculate the histogram distribution in action 212 (for example, because the patient may be moving), and process 200 may terminate. In some embodiments, if the pulsatility associated with the pressure signal is between a first threshold pulsatility value and a second threshold pulsatility value, it may be decided to calculate the histogram distribution in action 212, and process 200 may continue as described herein.

[0046] Process 200 may then proceed to act 214, in which the position of the cardiac pump may be determined, at least in part, based on the morphology of the histogram distribution. For example, in some embodiments, the position of the cardiac pump may be determined, at least in part, based on whether the histogram has a bimodal distribution or some other distribution. When the histogram has a bimodal distribution, it may be determined that the pump is not properly positioned (e.g., the pump outlet is located in the right ventricle rather than the pulmonary artery). Embodiments in which the pump position is determined using morphological information associated with a histogram distribution of values, which is derived from a pressure signal, are described in more detail in relation to Figures 3 and 4.

[0047] Process 200 may then proceed to act 216, in which the pump position indication is displayed on the user interface (e.g., on a display associated with the controller 130). The pump position indication may be displayed in any preferred manner. For example, an alarm or other alert may be displayed on the user interface when a “bad” position of the heart pump is determined, which may indicate to the user that the position of the heart pump should be adjusted. In another embodiment, the display may have color indicators (e.g., green and red indicating “good” and “bad” positions of the device, respectively).

[0048] Figure 3 is a flowchart of a process 300 for determining a morphological index associated with a pressure signal from a heart pump, according to some embodiments of the present disclosure. The morphological index may be used to determine the position of the heart pump within the patient's heart. Process 300 may begin with act 310, in which the pressure signal (e.g., a differential pressure signal received from a pressure sensor of the heart pump) is filtered. In some embodiments, a high-pass filter may be used to remove DC values ​​and low-frequency components of the pressure signal that may represent patient breath and / or sensor drift. In some embodiments, a band-pass filter may be used to filter the pressure signal by reducing high-frequency fluctuations in the signal while preserving the overall morphology of the signal. In some embodiments, the filter may be a linear phase filter (e.g., a finite impulse response (FIR) filter). Process 300 may then proceed to act 312, in which a time window of values ​​of the filtered pressure signal may be extracted for further analysis. In some embodiments, a time window of a fixed length may be used. In some embodiments, the length of the time window may be selected based at least in part on one or more criteria, including, but not limited to, a specificity criterion and / or an alarm update criterion. For example, if the length of the time window is selected to be too short, sufficient signals may not be captured within the window to distinguish between good and bad placements (i.e., the values ​​within the windowed signal may not have sufficient specificity). Alternatively, if the length of the time window is selected to be too long, the amount of time between alarm updates (e.g., when a bad placement is detected) may be too long. In some embodiments, the length of the time window is selected to be between 4 and 10 seconds. In some embodiments, the length of the time window is selected to be between 5 and 7 seconds. In some embodiments, the length of the time window is selected to be 6 seconds.

[0049] Process 300 may then proceed to act 314, in which the standard deviation of the histogram values ​​within the time window is calculated. Process 300 may then proceed to act 316, in which a sub-window within the time window is defined based at least in part on the calculated standard deviation of the histogram values ​​within the time window. For example, the sub-window may be centered within the time window and may have a width that is a multiple of the standard deviation. In some embodiments, the width of the time window may be half the standard deviation (e.g., + / -0.25SD), one standard deviation (e.g., + / -0.5SD), two standard deviations (i.e., + / -1SD), or some other multiple of the standard deviation calculated in act 314. Process 300 may then proceed to act 318, in which a morphological index (MI) value associated with the pressure signal may be determined based at least in part on the histogram values ​​within the sub-window. For example, in some embodiments, the MI value associated with the pressure signal may be determined as the sum of all histogram values ​​in a sub-window, divided by the sum of all histogram values ​​in the entire time window. The MI value associated with the pressure signal may then be used to determine the pump position, as described in relation to process 200. For example, the MI value may be compared to a threshold, and when the MI value is less than the threshold, it may be determined that the histogram distribution is bimodal. In such cases, it may be determined that the pump is not properly positioned (e.g., the pump output is located in the right ventricle rather than the pulmonary artery). In contrast, when the MI value is above the threshold, it may be determined that the pump is properly positioned (e.g., the cardiac pump output may be located in the pulmonary artery).

[0050] Figure 4 schematically illustrates how different pressure signals received from a cardiac pump pressure sensor can be mapped to different histogram distributions according to several embodiments. Figure 4 shows two different exemplary pressure signals. The first pressure signal 410 represents a “bad” placement of the cardiac pump, in which the outlet of the cardiac pump is located in the right ventricle of the patient’s heart. As shown, when the output of the cardiac pump is not properly placed in the pulmonary artery, the differential pressure signal spends most of its time either on the upper or lower side, with a steep slope between the peak and trough of the signal. The steeper peak and trough of the first pressure signal 410 are represented as two corresponding peaks in the histogram 400 generated from a windowed version of the first pressure signal 410 (e.g., six second windows). In other words, a bimodal histogram is generated when a “bad” placement signal is present.

[0051] The second pressure signal 420 represents a “good” placement of the heart pump, in which the outlet of the heart pump is located within the pulmonary artery and provides right ventricular support. As shown, when the output of the heart pump is properly placed within the pulmonary artery, the differential pressure signal spends approximately the same amount of time rising or falling, with a gentler slope between the peaks and troughs within the signal. The broader peaks and troughs within the second pressure signal 420 result in a histogram 402 that is closer to a normal distribution, with single peaks having values ​​close to zero.

[0052] As described in relation to process 300 in Figure 3, a technique for distinguishing a bimodal distribution (e.g., histogram 400) from a normal distribution (e.g., histogram 402), according to several embodiments, may involve defining a sub-window 430 that encompasses the central portion of the histogram and observing the presence or absence of peaks within that sub-window (e.g., the presence or absence of peaks near zero). In some embodiments, the width of the sub-window 430 may be determined based on the standard deviation of the values ​​in the histogram of the windowed pressure signal. In the exemplary histogram shown in Figure 4, the width of the sub-window 430 is defined as 1 standard deviation (+ / -0.5SD).

[0053] Specific techniques for generating morphological indices based on histogram values ​​within a sub-window and determining whether a histogram has a bimodal distribution are described herein, but it should be understood that other techniques for determining whether a histogram distribution has a bimodal distribution may also be used as alternatives. For example, a peak detection technique may be used to determine whether a histogram distribution has one peak or two peaks. In such embodiments, (one or more) alternative sub-windows may be selected, and the process is configured to look for the presence (or intensity) of peaks within those (one or more) windows. In another such embodiment, the slope of the histogram values ​​may be used to determine one or more local maximums representing one or more peaks in the histogram. As understood, other suitable techniques for evaluating histograms may also be used in other embodiments to determine whether a bimodal or normal histogram is generated.

[0054] While some aspects and embodiments of the technology described herein have been described above, it should be understood that various modifications, alterations, and improvements will be readily conceivable to those skilled in the art. Such modifications, alterations, and improvements are intended to be within the spirit and scope of the technology described herein. For example, those skilled in the art will readily conceivable various other means and / or structures for carrying out the functions described herein and / or obtaining one or more of the results and / or benefits, and each of such modifications and / or alterations will be considered within the scope of the embodiments described herein. Those skilled in the art will be able to recognize many equivalents to the specific embodiments described herein, or confirm them by using only routine experimentation. Therefore, it should be understood that the embodiments described herein are presented only as examples, and embodiments of the present invention may be practiced separately from those specifically described, within the scope of the appended claims and their equivalents. In addition, any combination of two or more features, systems, articles, materials, kits, and / or methods described herein is included within the scope of this disclosure, provided that such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent.

[0055] The embodiments described above can be implemented in any of a number of ways. One or more aspects and embodiments of the Disclosure involving the implementation of a process or method may utilize program instructions executable by a device (e.g., a computer, processor, or other device) to implement or control the implementation of the process or method. In this regard, various concepts of the Invention may be embodied as a computer-readable storage medium (or more computer-readable storage mediums) encoded with one or more programs (e.g., computer memory, one or more floppy disks, compact disks, optical disks, magnetic tape, flash memory, field-programmable gate arrays, or circuit configurations in other semiconductor devices, or other tangible computer storage mediums), which, when executed on one or more computers or other processors, implements a method of implementing one or more of the various embodiments described above. The (one or more) computer-readable mediums may be transportable, and the (one or more) programs stored thereon may 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-transient medium.

[0056] The embodiments of this technology described above can be implemented in any of a number of ways. For example, the embodiments may be implemented using hardware, software, or a combination thereof. When implemented in software, the software code can run on any suitable processor or set of processors, whether provided on a single computer or distributed across multiple computers. It should be understood that any component or set of components that perform the functions described above can generally be considered a controller that controls the functions described above. The controller can be implemented in a number of ways, such as using dedicated hardware or using general-purpose hardware (e.g., one or more processors) programmed with microcode or software to perform the functions listed above, and when the controller corresponds to multiple components of a system, it may be implemented in a combination of these ways.

[0057] Furthermore, it should be understood that, in non-limiting embodiments, computers can be embodied in any of several forms, such as rack-mount computers, desktop computers, laptop computers, or tablet computers. In addition, computers can be embedded in devices that are not generally considered computers but possess suitable processing capabilities, including personal digital assistants (PDAs), smartphones, or any other suitable portable or fixed electronic devices.

[0058] Furthermore, a computer may have one or more input and output devices. These devices can, among other things, be used to present a user interface. Embodiments 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. Embodiments of input devices that can be used for a user interface include a keyboard and pointing devices such as a mouse, touchpad, and digitized tablet. In another embodiment, a computer may receive input information through speech recognition or in other audible formats.

[0059] Such computers may be interconnected by one or more networks in any preferred form, including local area networks or wide area networks such as enterprise networks, and intelligent networks (INs) or the Internet. Such networks may be based on any preferred technology, operate according to any preferred protocol, and may include wireless networks, wired networks, or fiber optic networks.

[0060] Furthermore, as will be explained, several aspects may be embodied in one or more ways. The actions performed as part of the method may be ordered in any preferred way. Thus, embodiments may be constructed in which the actions are performed in a different order than those illustrated, and may include performing several actions simultaneously, even if they are shown as sequential actions in the illustrative embodiments.

[0061] It should be understood that all definitions defined and used herein take precedence over dictionary definitions, definitions in literature incorporated by reference, and / or the ordinary meaning of the defined term.

[0062] The indefinite articles "a" and "an" as used in the specification and claims herein should be understood to mean "at least one" unless explicitly indicated otherwise.

[0063] The phrase "and / or" as used in the specification and claims herein should be understood to mean "either or both" of the elements thus combined, that is, elements that exist conjugately in some cases and disjunctly in others. Multiple elements listed using "and / or" should be interpreted in the same manner, that is, "one or more" of the elements thus combined. Other elements other than those specifically identified by the "and / or" clause may exist, whether related to or unrelated to those specifically identified elements. Therefore, in non-restrictive embodiments, a reference to "A and / or B," when used in conjunction with non-restrictive terms such as "comprising," may refer in one embodiment to A only (optionally including elements other than B), in another embodiment to B only (optionally including elements other than A), in yet another embodiment to both A and B (optionally including other elements), and so on.

[0064] As used in the specification and claims herein, the phrase “at least one” referring to a list of one or more elements means at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of every element specifically enumerated in the list of elements, and not excluding any combination of elements in the list of elements. This definition also allows for the optional presence of elements other than those specifically identified in the list of elements to which the phrase “at least one” refers, whether related to or unrelated to those specifically identified elements. Therefore, in non-limiting embodiments, “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”) may refer to, in one embodiment, at least one A (and optionally including elements other than B) which may not include any B; in another embodiment, at least one B (and optionally including elements other than A) which may not include any A; and in yet another embodiment, at least one A which may include one or more, and at least one B (and optionally including other elements), and so on.

[0065] Furthermore, the terminology and grammar used herein are for illustrative purposes only and should not be considered limiting. The use of “including,” “comprising,” “having,” “containing,” “involving,” and their variations herein means that they encompass the items listed below and their equivalents, as well as any additional items.

[0066] In the claims and the above specification, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and their equivalents shall be understood to be open-ended, meaning they include but are not limited to them. Only the transitional phrases “consisting of” and “consisting essentially of” shall be considered restrictive or semi-restrictive transitional phrases, respectively.

[0067] The use of ordinal terms such as "first," "second," and "third" in the claims to modify claim elements does not, in itself, imply any priority, precedence, or order of one claim element over another, or any chronological order in which the actions of the method are performed, but is simply used as a distinguishing mark to differentiate one claim element having a certain name from another having the same name (except by the use of other element ordinal terms).

Claims

1. A method for determining the location of the cardiac pump within a patient's heart, wherein the method is: Receiving a pressure signal from at least one pressure sensor arranged on the heart pump, To generate a histogram of the values ​​observed within the time window associated with the pressure signal, Determining the position of the heart pump based at least partially on the shape of the histogram: Methods that include...

2. The method according to claim 1, wherein the at least one pressure sensor comprises a differential pressure sensor.

3. The method according to claim 1, wherein the length of the time window is at least 4 seconds and less than 10 seconds.

4. The method according to claim 3, wherein the length of the time window is at least 5 seconds and less than 7 seconds.

5. The method further includes filtering the pressure signal and generating a filtered pressure signal, The method according to claim 1, wherein generating a histogram of values ​​comprises generating a histogram of values ​​observed within a time window of the filtered pressure signal.

6. The method according to claim 5, wherein filtering the pressure signal includes filtering the pressure signal using a finite impulse response (FIR) filter.

7. The method according to claim 1, wherein determining the position of the heart pump based at least partially on the shape of the histogram comprises determining the position of the heart pump based at least partially on the distribution of the histogram.

8. The method according to claim 7, wherein determining the position of the heart pump based at least in part on the distribution of the histogram includes determining whether the distribution is bimodal.

9. Determining the position of the heart pump based at least partially on the distribution of the histogram further, The method according to claim 8, comprising determining that the cardiac pump is not properly positioned when the histogram has the bimodal distribution.

10. The method according to claim 1, wherein determining the position of the heart pump based at least in part on the distribution of the histogram further comprises determining whether the distribution is a normal distribution.

11. Determining the position of the heart pump based at least partially on the distribution of the histogram further, The method according to claim 10, comprising determining that the heart pump is properly positioned when the histogram has the normal distribution.

12. Determining the position of the heart pump based at least partially on the shape of the histogram is: Determining the standard deviation of the values ​​within the aforementioned time window, Define a sub-window within the time window based at least partially on the standard deviation, The position of the heart pump is determined at least partially based on the value in the sub-window. The method according to claim 1, including the method described in claim 1.

13. Determining the position of the heart pump based at least partially on the value in the sub-window is, Calculate the first sum of all values ​​in the aforementioned sub-window, Calculate the second sum of all values ​​within the aforementioned time window, Dividing the first sum by the second sum to determine the morphological index value, When the morphological index value is below a threshold, it is determined that the cardiac pump is not properly positioned, When the morphological index value exceeds the threshold, it is determined that the cardiac pump is properly positioned. The method according to claim 12, including the method described in claim 12.

14. The method according to claim 1, further comprising outputting an indication of the position of the heart pump via a user interface.

15. The method further includes determining the pulsatility of the pressure signal, The method according to claim 1, wherein generating a histogram of values ​​is performed in response to the pulsatility of the pressure signal exceeding a first threshold pulsatility value and falling below a second threshold pulsatility value.

16. The cardiac pump is configured to provide right heart support for the patient, The method according to claim 1, wherein determining the position of the cardiac pump based at least in part on the shape of the histogram includes determining whether the outlet of the cardiac pump is located within the patient's pulmonary artery.

17. A cardiac pump system, wherein the cardiac pump system is A cardiac pump including at least one pressure sensor configured to sense pressure within a portion of the patient's heart, A controller, wherein the controller is Receiving a pressure signal output from at least one of the pressure sensors, To generate a histogram of the values ​​observed within the time window associated with the pressure signal, The position of the heart pump is determined at least partially based on the shape of the histogram. A controller and A heart pump system equipped with this system.

18. The cardiac pump system according to claim 17, wherein the at least one pressure sensor comprises a differential pressure sensor.

19. The cardiac pump system according to claim 17, wherein the length of the time window is at least 4 seconds and less than 10 seconds.

20. The cardiac pump system according to claim 19, wherein the length of the time window is at least 5 seconds and less than 7 seconds.

21. The controller further, The system is configured to filter the pressure signal and generate the filtered pressure signal, The cardiac pump system according to claim 17, wherein generating a histogram of values ​​comprises generating a histogram of values ​​observed within a time window of the filtered pressure signal.

22. The cardiac pump system according to claim 21, wherein filtering the pressure signal includes filtering the pressure signal using a finite impulse response (FIR) filter.

23. The heart pump system according to claim 17, wherein determining the position of the heart pump based at least partially on the shape of the histogram comprises determining the position of the heart pump based at least partially on the distribution of the histogram.

24. The heart pump system according to claim 23, wherein determining the position of the heart pump based at least in part on the distribution of the histogram includes determining whether the distribution is bimodal.

25. Determining the position of the heart pump based at least partially on the distribution of the histogram further, The cardiac pump system according to claim 24, comprising determining that the cardiac pump is not properly positioned when the histogram has the bimodal distribution.

26. The heart pump system according to claim 24, wherein determining the position of the heart pump based at least in part on the distribution of the histogram further comprises determining whether the distribution is a normal distribution.

27. Determining the position of the heart pump based at least partially on the distribution of the histogram further, The cardiac pump system according to claim 26, comprising determining that the cardiac pump is properly positioned when the histogram has the normal distribution.

28. Determining the position of the heart pump based at least partially on the shape of the histogram is: Determining the standard deviation of the values ​​within the aforementioned time window, Define a sub-window within the time window based at least partially on the standard deviation, The position of the heart pump is determined at least partially based on the value in the sub-window. The cardiac pump system according to claim 17, including the following:

29. Determining the position of the heart pump based at least partially on the value in the sub-window is, Calculate the first sum of all values ​​in the aforementioned sub-window, Calculate the second sum of all values ​​within the aforementioned time window, Dividing the first sum by the second sum to determine the morphological index value, When the morphological index value is below a threshold, it is determined that the cardiac pump is not properly positioned, When the morphological index value exceeds the threshold, it is determined that the cardiac pump is properly positioned. The cardiac pump system according to claim 28, including the following:

30. The controller further, The cardiac pump system according to claim 17, configured to output an indication of the position of the cardiac pump via a user interface.

31. The controller further, It is configured to determine the pulsation of the pressure signal, The cardiac pump system according to claim 17, wherein generating a histogram of values ​​is performed in response to the pulsatility of the pressure signal exceeding a first threshold pulsatility value and falling below a second threshold pulsatility value.

32. The cardiac pump is configured to provide right heart support for the patient, The cardiac pump system according to claim 17, wherein determining the position of the cardiac pump based at least in part on the shape of the histogram includes determining whether the outlet of the cardiac pump is located within the patient's pulmonary artery.

33. A controller for a cardiac pump system, wherein the controller is Equipped with at least one hardware processor, The at least one hardware processor is The system receives a pressure signal output from at least one pressure sensor arranged on the heart pump of the heart pump system, To generate a histogram of the values ​​observed within the time window associated with the pressure signal, The position of the heart pump is determined at least partially based on the shape of the histogram. A controller configured to perform the following actions.

34. The controller according to claim 33, wherein the at least one pressure sensor comprises a differential pressure sensor.

35. The controller according to claim 33, wherein the length of the time window is at least 4 seconds and less than 10 seconds.

36. The controller according to claim 35, wherein the length of the time window is at least 5 seconds and less than 7 seconds.

37. The aforementioned at least one hardware processor further, The system is configured to filter the pressure signal and generate the filtered pressure signal, The controller according to claim 33, wherein generating a histogram of values ​​includes generating a histogram of values ​​observed within a time window of the filtered pressure signal.

38. The controller according to claim 37, wherein filtering the pressure signal includes filtering the pressure signal using a finite impulse response (FIR) filter.

39. The controller according to claim 33, wherein determining the position of the heart pump based at least partially on the shape of the histogram comprises determining the position of the heart pump based at least partially on the distribution of the histogram.

40. The controller according to claim 39, wherein determining the position of the heart pump based at least in part on the distribution of the histogram includes determining whether the distribution is bimodal.

41. Determining the position of the heart pump based at least partially on the distribution of the histogram further, The controller according to claim 40, comprising determining that the cardiac pump is not properly positioned when the histogram has the bimodal distribution.

42. The controller according to claim 38, wherein determining the position of the heart pump based at least in part on the distribution of the histogram further includes determining whether the distribution is a normal distribution.

43. Determining the position of the heart pump based at least partially on the distribution of the histogram further, The controller according to claim 42, comprising determining that the heart pump is properly positioned when the histogram has the normal distribution.

44. Determining the position of the heart pump based at least partially on the shape of the histogram is: Determining the standard deviation of the values ​​within the aforementioned time window, Define a sub-window within the time window based at least partially on the standard deviation, The position of the heart pump is determined at least partially based on the value in the sub-window. The controller according to claim 33, including the controller described in claim 33.

45. Determining the position of the heart pump based at least partially on the value in the sub-window is, Calculate the first sum of all values ​​in the aforementioned sub-window, Calculate the second sum of all values ​​within the aforementioned time window, Dividing the first sum by the second sum to determine the morphological index value, When the morphological index value is below a threshold, it is determined that the cardiac pump is not properly positioned, When the morphological index value exceeds the threshold, it is determined that the cardiac pump is properly positioned. The controller according to claim 44, including the controller described in claim 44.

46. The aforementioned at least one hardware processor further, The controller according to claim 33, configured to output an indication of the position of the heart pump via a user interface.

47. The aforementioned at least one hardware processor further, It is configured to determine the pulsation of the pressure signal, The controller according to claim 33, wherein generating a histogram of values ​​is performed in response to the pulsatility of the pressure signal exceeding a first threshold pulsatility value and falling below a second threshold pulsatility value.

48. The cardiac pump is configured to provide right heart support for the patient. The controller according to claim 33, wherein determining the position of the cardiac pump based at least in part on the form of the histogram includes determining whether the outlet of the cardiac pump is located within the patient's pulmonary artery.

49. A method for determining the position of a right heart assist device within a patient's heart, wherein the method is: Receiving a pressure signal from at least one pressure sensor arranged adjacent to the outlet of the right heart assist device, To generate a histogram of the values ​​observed within the time window associated with the pressure signal, To determine that the distribution of the aforementioned histogram is bimodal, In response to determining that the distribution of the histogram is bimodal, an indication is output that the outlet of the right heart assist device is not located within the patient's pulmonary artery. Methods that include...

50. The method according to claim 49, wherein the at least one pressure sensor comprises a differential pressure sensor.

51. The method according to claim 49, wherein the length of the time window is at least 4 seconds and less than 10 seconds.

52. The method according to claim 51, wherein the length of the time window is at least 5 seconds and less than 7 seconds.

53. The method further includes filtering the pressure signal and generating a filtered pressure signal, The method according to claim 49, wherein generating a histogram of values ​​comprises generating a histogram of values ​​observed within a time window of the filtered pressure signal.

54. The method according to claim 53, wherein filtering the pressure signal includes filtering the pressure signal using a finite impulse response (FIR) filter.

55. Determining that the distribution of the histogram is bimodal means Determining the standard deviation of the values ​​within the aforementioned time window, Define a sub-window within the time window based at least partially on the standard deviation, Based at least partially on the values ​​in the sub-window, it is determined that the distribution of the histogram is bimodal. The method according to claim 49, including the method described in claim 49.

56. Determining that the distribution of the histogram is bimodal based at least partially on the values ​​in the sub-window is: Calculate the first sum of all values ​​in the aforementioned sub-window, Calculate the second sum of all values ​​within the aforementioned time window, Dividing the first sum by the second sum to determine the morphological index value, When the morphological index value is less than the threshold, it is determined that the distribution of the histogram is bimodal. The method according to claim 55, including the method described in claim 55.

57. The method further includes determining the pulsatility of the pressure signal, The method according to claim 49, wherein generating a histogram of values ​​is performed in response to the pulsatility of the pressure signal exceeding a first threshold pulsatility value and falling below a second threshold pulsatility value.

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