System and method for detecting aspiration events in a blood pump - Patents.com

Abstract

A system and method for detecting aspiration events in a blood pump by monitoring a pump motor current. A pump aspiration event is detected based on a comparison of a pulsatility index calculated based on a filtered pump motor current signal to a first predetermined threshold value or based on a comparison of a calculated index associated with a normalized bandpass filtered pump motor current signal to a second predetermined threshold value. Aspiration events are also detected based on a comparison of both the calculated pulsatility index and the calculated index associated with the normalized bandpass filtered pump motor current signal to respective first and second predetermined threshold values.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Provisional Application No. 63 / 270,940, filed October 22, 2021, which is incorporated by reference in its entirety.

[0002] The present technology relates to systems and methods for detecting aspiration events in blood pumps, such as heart pumps, using pump motor current. [Background technology]

[0003] Fluid pumps, such as blood pumps, are used in the medical field for a wide variety of applications and purposes. 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 in the patient's heart or elsewhere in the patient's circulatory system. For example, an intravascular blood pump may be inserted through a catheter and positioned to span a heart valve. The intravascular blood pump is typically disposed at the end of the catheter. Once in place, the pump may be used to assist the heart, pumping blood through the circulatory system and thus temporarily reducing the workload of the patient's heart, such as to allow 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.

[0004] Such pumps can be positioned in a chamber of the heart, such as the left ventricle, to assist the heart. In this case, the blood pump can be inserted via a femoral artery by means of a hollow catheter and introduced up to and into the left ventricle of the patient's heart. From this position, the blood pump inlet draws in blood and the blood pump outlet ejects blood into the aorta. In this way, the function of the heart can be replaced or at least assisted by the action of the pump.

[0005] Each intravascular blood pump is typically connected to a respective external heart pump controller that controls the heart pump, such as motor speed, and collects and displays operational data regarding the blood pump, such as cardiac signal levels, battery temperature, blood flow rate, and plumbing integrity. An exemplary heart pump controller is available from Abiomed, Inc. under the trade name Automated Impella Controller®. The controller issues an alarm when an operational data value exceeds a predetermined value or range, e.g., if a leak or loss of suction is detected. The controller includes a video display screen as a human user interface on which the operational data and / or alarms are displayed.

[0006] When blood pumps use suction to draw blood into the pump, a suction event may occur if the pump suction inlet is too close or adjacent to cardiac tissue. A suction event may occur when the pump inlet interacts with cardiac tissue, causing a partial or complete blockage of pump flow. A persistent suction event may damage the patient's heart, impair pump function, and cause inadequate perfusion. In addition, a suction event may also result in hemolysis. Thus, there is a need to detect suction so that a suction event can be resolved. Summary of the Invention

[0007] SUMMARY OF THE DISCLOSURE Systems and methods for detecting aspiration events in a blood pump are described herein.

[0008] In one aspect, a blood pump is provided that includes an inlet, an outlet, a rotor, a motor for driving rotation of the rotor to transport blood from the inlet to the outlet, and at least one processor configured to monitor a motor current signal of the motor, filter the motor current signal, calculate a pulsatility index of the motor current signal based on the filtered motor current signal, compare the calculated pulsatility index to a predetermined threshold, and detect an occurrence of a suction event based on the comparison.

[0009] In another aspect, a blood pump is provided that includes an inlet, an outlet, a rotor, a motor for driving rotation of the rotor to transport blood from the inlet to the outlet, and at least one processor configured to monitor a motor current signal of the motor, low-pass filter the motor current signal, band-pass filter the low-pass filtered motor current signal, normalize the band-pass filtered motor current signal, calculate an index value based on the normalized band-pass filtered motor current signal, compare the calculated index value to a predetermined threshold, and detect the occurrence of a suction event based on the comparison.

[0010] In another aspect, a blood pump is provided that includes an inlet, an outlet, a rotor, a motor that drives rotation of the rotor to transport blood from the inlet to the outlet, and at least one processor configured to monitor a motor current signal of the motor, low pass filter the motor current signal, calculate a pulsatility index of the motor current signal based on the low pass filtered motor current signal, band pass filter the low pass filtered motor current signal, normalize the band pass filtered motor current signal, calculate an index value based on the normalized band pass filtered signal, compare the calculated pulsatility index to a first predetermined threshold, compare the calculated index value to a second predetermined threshold, compare the calculated pulsatility index to the first predetermined threshold, and detect an occurrence of a suction event based on comparing the calculated index value to the second predetermined threshold. [Brief description of the drawings]

[0011] [Figure 1A] 1 shows a prior art pump inserted into the heart. [Figure 1B] 1B shows a portion of the prior art pump of FIG. 1A. [Figure 2A] 1 shows a pump system according to the present technology. [Figure 2B] FIG. 2B is a cross-sectional view of a portion of the pump system of FIG. 2A in accordance with the present technique. [Diagram 3]4 is a graph of a motor current signal of a pump according to the present technique. [Figure 4] 1 is a graph showing pulsatility in a motor current signal of a pump according to the present technology. [Diagram 5] 13 is a graph showing aspiration detection versus pulsatility index threshold in accordance with the present technology. [Figure 6] 1 is a flow chart of a method for detecting aspiration events according to the present technology. [Figure 7] 4 is a graph showing a noisy motor current signal and a filtered motor current signal in accordance with the present technique; [Figure 8] 4 shows the filter response of an elliptic filter according to the present technique. [Figure 9] 4 shows the filter response of a Butterworth filter according to the present technique. [Figure 10] 4 illustrates filtering and normalization of a pump motor current signal according to the present technique. [Figure 11] 13 is a flow chart of another method for detecting aspiration events according to the present technology. [Figure 12] 13 is a flow chart of another method for detecting aspiration events according to the present technology. [Figure 13] The results of testing the suction detection method using this technology are shown below. [Figure 14] The results of testing the suction detection method using this technology are shown below. [Figure 15] The results of testing the suction detection method using this technology are shown below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Aspects of the present disclosure will be described in detail with reference to the drawings in which like reference numbers identify similar or identical elements. It should be understood that the disclosed aspects are merely examples of the present disclosure, which may be embodied in various forms. Well-known functions or structures are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, the specific structure and function details disclosed herein should not be interpreted as limitations, but merely as a basis for the claims and as a representative basis for teaching those skilled in the art to variously employ the present disclosure in substantially any appropriately detailed structure.

[0013] Traditionally, in blood pumps, such as catheter-based heart pumps that are inserted into a patient's ventricle, suction events that may be caused by interactions between the pump inlet and the cardiac tissue are detected using both pressure sensors and motor current.

[0014] For example, a prior art catheter-based heart pump is shown in Figures 1A and 1B. The blood pump of Figures 1A and 1B is based on a catheter 10 (catheter-based blood pump) by which a blood pump is temporarily introduced into the left ventricle 16 of the heart through the aorta 12 and the aortic valve 15. As shown in more detail in Figure 1B, the blood pump comprises, in addition to the catheter 10, a rotary pump device 50 fixed to the end of the catheter tube 20. The rotary pump device 50 comprises a motor part 51 and a pump part 52 arranged axially apart therefrom. A flow cannula 53 is connected at one end to the pump part 52 and has an inflow cage 54 extending from the pump part 52 and arranged at the other end. An atraumatic tip 55 is attached to the inflow cage 54. The pump part 52 comprises a pump housing having an outlet opening 56. Furthermore, the pump device 50 comprises a drive shaft 57 protruding from the motor part 51 into the pump housing of the pump part 52. The drive shaft 57 drives an impeller 58 as a propulsion element, so that during operation of the blood pump, blood can be drawn in through the inflow cage 54 (forming the inlet) and expelled through the outlet opening 56 (forming the outlet) on the other side of the aortic valve 15.

[0015] 1A and 1B, three wires pass through the catheter tube 20 of the catheter 10 to the pump device 50: two signal wires 28A and 28B and a power wire 29 for supplying current to the motor section 51. The two signal wires 28A and 28B and the power wire 29 are attached to the control device 100 at their proximal ends.

[0016] 1B, signal lines 28A, 28B couple the blood pressure sensors to corresponding sensor heads 30 and 60, respectively, which are located outside the housing of the pump portion 52. The sensor head 60 of the first pressure sensor is associated with signal line 28B. Signal line 28A is associated with and connected to the sensor head 30 of the second blood pressure sensor. The pressure sensor signals, which carry respective information regarding the pressure at the sensor location and may be of any suitable physical origin, e.g., optical, hydraulic or electrical, are transmitted via the respective signal lines 28A, 28B to corresponding inputs of the controller 100.

[0017] As mentioned above, blood pressure sensed by sensors 30, 60 and motor current provided to motor section 51 via power line 29 may conventionally be used by controller 100 to determine whether a suction event is occurring. However, some pumps may not include a pressure sensor and may place the pump motor outside of the patient to reduce the maximum outer diameter of the pump as it is inserted into and removed from the patient.

[0018] For example, a pump system 100 coupled to a control unit 200 according to the present technology is shown in Figures 2A and 2B. The pump 100 includes a distal atraumatic tip 102, a coated pump housing 104 surrounding a rotor 108, an outflow tube 106, a distal bearing 110, a proximal bearing 112, an inlet 116, an outlet 118, a catheter 120, a handle 130, a cable 140, and a motor 150. In one aspect, the pump housing 104 is a frame structure formed by a mesh having an opening that may be at least partially covered by a resilient material. A proximal portion of the pump housing 104 extends into and is attached to the hollow interior of the outflow tube 106, and a distal portion of the pump housing 104 extends distally beyond the distal end of the outflow tube 106. An exposed opening in the mesh pump housing 104 that extends distally beyond the outflow tube 106 forms the inlet 116 of the pump 100. The proximal end of the outflow tube 106 includes a plurality of openings which form an outlet 118 of the pump 100. The rotor 108 is rotatably mounted between bearings 110, 112 and is coupled to a distal end of a flexible drive shaft 114. The drive shaft 114 extends through the catheter 120, through the hollow interior of the outflow tube 106 and into a handle 130 which is coupled to a motor 130 which is integral to the handle 130. The proximal end of the handle 130 is coupled to a control unit 200 via a cable 140.

[0019] The control unit 200 includes one or more memories 202, one or more processors 204, a user interface 206, and one or more current sensors 208. The processor(s) 204 may comprise one or more microcontrollers, one or more microprocessors, one or more application specific integrated circuits (ASICs), one or more digital signal processors, program memory, or other similar components. The processor 204 is communicatively coupled to and configured to control the operation of the other components of the control unit 200 (e.g., 202, 206, 208) and the pump 100. In one aspect, the controller 200 is an Automated Impeller Controller® manufactured by Abiomed, Inc. (Danvers, MA). In some aspects, the memory 202 is included within the processor 204.

[0020] In operation, the processor 204 controls the power delivered to the motor 150 by a power line (not shown) in the cable 140 (e.g., by controlling a power supply (not shown)). By controlling the power delivered to the motor 150, the processor 204 can control the speed of the motor 150. In one aspect, the processor 204 may monitor the motor current using one or more current sensors 208 that measure and sample the motor current. The current sensors 208 may be included in the control unit 200 or along any portion of the power line in the cable 140. In another aspect, the current sensors 208 may be included in the motor 130 and the processor 204 may monitor and measure the motor current via a data line (not shown) in the cable 140 that is coupled to the processor 204 and the motor 150.

[0021] The memory 202 may store computer-readable instructions and other information for various functions of the components of the control unit 200. In one aspect, the memory 202 includes volatile and / or non-volatile memory, such as an Electrically Erasable Programmable Read Only Memory (EEPROM).

[0022] The user interface 206 may include means for receiving user input, such as buttons, switches, knobs, etc. Additionally, the user interface 206 may include a display for displaying information and one or more indicators, such as light indicators, audio indicators, etc., for conveying information and / or providing alerts regarding the operation of the pump 100.

[0023] The pump 100 can be inserted into a patient's body, for example into the left ventricle of the heart, using an introducer system. In one aspect, the housing 104, rotor 108, and outflow tube 106 are radially compressible to allow the pump 100 to achieve a relatively small outer diameter, for example 9 Fr (3 mm), during insertion. Once the pump 100 is inserted into the patient's body, for example into the left ventricle, the handle 130 and motor 150 are positioned outside the patient's body, similar to that described above with reference to the pump of FIGS. 1A and 1B. The motor 150 is controlled by the processor 204 to drive the rotation of the drive shaft 114 and rotor 108 to transport blood from the inlet 116 to the outlet 118. It should be appreciated that the rotor 108 may be rotated in the opposite direction by the motor 150 to transport blood in the opposite direction (in which case the opening in 118 forms the inlet and the opening in 116 forms the outlet). In one aspect, pump 100 is intended to be used during high-risk procedures for durations of up to six hours, although it should be understood that the technology of the present disclosure is not limited to any particular type of treatment and / or duration of use.

[0024] Because pump 100 lacks a pressure sensor included in conventional pumps such as those shown in Figures 1A and 1B, conventional suction detection methods or algorithms that rely on pressure signals cannot be used with pump 100. However, when pump 100 is inserted into a patient, suction events may still occur and need to be detected so as to be resolved in a timely manner so that the risk of damage to the patient and / or pump 100 may be reduced. Thus, there is a need to enable suction detection in pumps that do not include a pressure sensor, such as pump 100.

[0025] To address this need and enable aspiration detection in such blood pumps that do not include a pressure sensor, the present disclosure describes systems and methods for detecting aspiration events in blood pumps using only the pump's motor current signal. In one aspect, systems and methods are disclosed for detecting aspiration events using a pulsatility index of the motor current signal. In another aspect, systems and methods are disclosed for detecting aspiration events using an index of a normalized bandpass filtered signal of the motor current signal. In yet another aspect, systems and methods are disclosed for detecting aspiration events using both the pulsatility index and the index of a normalized bandpass filtered signal.

[0026] The suction detection methods described herein (i.e., methods 600, 1100, 1200 described below) may be implemented in the control unit 200 of the pump system 100. For example, computer readable instructions for one or all of the methods described below may be stored in one or more memories 202 and executed by one or more processors 204 of the control unit 200 during use of the pump to detect aspiration events. Additionally, parameters and settings of one or more processors used in the methods described herein, such as predetermined thresholds, predetermined window lengths, bin sizes, and / or any other parameters and settings of the methods described below, may be stored in the memory 202. The parameters and settings, as well as the particular suction detection method performed by the processor 204, may be adjusted or selected by a user via user input to the user interface 206 of the control unit 200.

[0027] Normalization During normal use of the pump 100 and in the absence of the occurrence of a suction event, the motor current of the motor 150 may vary over time, such as by trending downward over time. For example, a downward trending motor current according to the methods described herein is shown in FIG. 3. In the graph of FIG. 3, the y-axis represents motor current (in mA) and the x-axis represents time. Thus, the downward trending motor current makes it difficult to achieve an absolute threshold that can be reliably implemented in a processor configured to detect a suction event. Furthermore, there are variations in the characteristics and performance of different pump models and the operating speeds of those different pumps. Thus, as described in more detail below, in some aspects, the index of the processor output provided by the methods described herein may be normalized and not dependent on the absolute value of the motor current. Using a normalized index produces more reliable suction detection by incorporating an absolute or global threshold used to detect a suction event that can be used with different pumps across different pump speeds and to account for varying (e.g., decreasing) motor currents.

[0028] Aspiration detection using pulsatility index In one aspect of the present technology, a pulsatility index is used to detect suction events in a pump system, such as pump system 100. For example, in the field of medical ultrasound analysis of blood flow, a pulsatility index is defined as the difference between the peak systolic blood flow velocity and the end diastolic blood flow velocity divided by the time-averaged flow velocity. Such a pulsatility index is hypothesized to reflect the vascular resistance in the artery distal to the location of acoustic isolation. As described herein, the principles of systolic and diastolic flow velocity pulsatility may be extended to the motor current signal of a blood pump to calculate a pulsatility index (PI) of the motor current, which is used to detect suction events.

[0029] For example, in one aspect of the present technology, to calculate the PI of the motor current signal, the maximum motor current (max MC) and the minimum motor current (min MC) within a predefined time duration window (predefined window) are each detected by the processor 204. Also, the average motor current (average MC) is calculated by the processor 204 by averaging the motor current samples within the predefined window.

[0030]

number

[0031] Using the maximum MC, minimum MC, and average MC calculated here, the processor 204 calculates a normalized PI of the motor current signal, as defined below.

[0032]

number

[0033] When an aspiration event occurs, it decreases the PI of the motor current and increases the minimum motor current. For example, this effect is shown in the graph of FIG. 4 according to the present technology. In FIG. 4, the y-axis represents the motor current measured in mA, and the x-axis represents time. As shown, during use of the pump, the motor current exhibits a pulsatile behavior. However, the pulsatility of the motor current during an aspiration event changes. In this regard, as shown in FIG. 4, during an aspiration event 402, the PI of the motor current (calculated in Equation 2) decreases and the minimum motor current increases relative to the PI and minimum motor current outside (before and after) the aspiration event 402.

[0034] The pulsatile decrease in motor current exhibited during aspiration events is used in accordance with the present technique to detect such aspiration events during use of the pump. Since the calculated PI is normalized, a global threshold can be defined to account for the motor current decreasing over time across all pump speeds. The global threshold can then be compared to the calculated PI of the motor current when the pump is in use to detect whether or not aspiration events are occurring. For example, in one embodiment, the threshold can be about (e.g., + / - 10%) 0.15. Referring to FIG. 5, a graph of laboratory test results in accordance with the present technique is shown in which different pump speeds (represented as p levels P9-P5 in FIG. 5) and blood pressure conditions (i.e., 90 / 70, 120 / 70, 160 / 20 mmHg as shown in the legend of FIG. 5) were simulated both during and without aspiration events. In the graph of FIG. 5, the y-axis represents the PI of the motor current and the x-axis represents the minimum motor current (measured in mA) of the pump motor. As shown in FIG. 5, when there is no suction event, the calculated PI is greater than 0.15, and when there is a section event, the calculated PI is less than 0.15. Therefore, 0.15 was found to be an appropriate PI for predicting the occurrence of suction events under different pump speed and blood pressure conditions. The threshold of 0.15 was found to balance sensitivity and stability or specificity when used in detecting suction events. It should be understood that other thresholds for comparison with the calculated PI are contemplated to be within the scope of the present disclosure.

[0035] Referring to FIG. 7, a graph of a motor current signal and a filtered motor current signal according to the present technique is shown. The results in the graph of FIG. 7 were obtained during an animal study in a noisy environment. The y-axis represents the motor current measured in mA, and the x-axis represents time. The dotted line in the graph of FIG. 7 is the motor current signal. As shown, in a noisy environment, the motor current signal contains spikes and noise that may reduce the accuracy of the above-mentioned method using the PI of the motor current. The signal may be filtered to produce a less noisy and smoother signal, as shown by the solid line in FIG. 7, which may increase the accuracy of the aspiration detection method. For example, the motor current signal may be low pass filtered using a 15 Hz low pass filter, which is selected to remove noise spikes in the motor current signal while also preserving the relevant pulsatility and heart rate information in the signal.

[0036] 6, a method 600 for detecting aspiration events using the PI of the motor current during use of a pump in a patient, such as pump 100, is shown in accordance with the present technique. It should be appreciated that method 600 may be implemented or performed by one or more processors of a pump system, such as processor 204, using the pump motor current as the only input.

[0037] Initially, in step 602, the processor 204 monitors the motor current of the pump motor after deployment of the pump in the patient and activation of the pump. In step 604, the motor current signal is filtered using a low pass filter to remove noise and spikes from the motor current signal. For example, in one embodiment, a 15 Hz low pass filter may be used to filter the motor current signal, although it should be understood that other low pass filters (e.g., low pass filters based on frequencies other than 15 Hz) may be appropriate in other embodiments. In one exemplary embodiment, the low pass filter may be a second order Butterworth filter as shown in FIG. 9. It should further be understood that the filtering may be implemented digitally by the processor 204. Alternatively, the processor 204 may control an analog filter circuit, for example, included in the control unit 200 or external to the control unit 200, to low pass filter the motor current signal.

[0038] In step 606, the processor 204 detects the maximum and minimum MC within a predetermined time window (e.g., 2 seconds) of the filtered motor current signal. In step 608, the processor 204 calculates the average MC of the motor current samples within the predetermined window of the filtered motor current signal according to Equation 1 above. In step 610, the processor 204 calculates the PI of the motor current for the predetermined window using the detected maximum and minimum MC of step 606 and the calculated average MC of step 608 according to Equation 2 above. In step 612, the processor 204 compares the calculated PI of step 610 to a first threshold. As discussed above, the first threshold may be about 0.15 and may be used reliably across different pump speeds, different pump types, and to account for downwardly trending motor currents. If in step 612 the processor 204 determines that the calculated PI is not below (i.e., above) the first threshold, the processor 204 determines in step 614 that suction is not detected. Alternatively, if, in step 612, the processor 204 determines that the calculated PI is less than the first threshold, then, in step 618, the processor 204 determines that aspiration is detected.

[0039] In one aspect, the suction detection method 600 may include a counter (implemented and maintained by the processor 204 and stored in the memory 202) that holds a count of non-aspiration / aspiration detection from steps 614, 618. For example, in one aspect, the counter is a stepped counter such that the processor 204 decrements the counter by one if no aspiration is detected and increments the counter by one if aspiration is detected. It should be understood that if the counter is at zero, the processor 204 will not decrement the counter below zero, i.e., zero is the floor of the counter. If the processor 204 determines that the counter has reached a predetermined suction count, an alarm condition is triggered by the processor 204. The predetermined suction count is selected to balance sensitivity and stability of aspiration detection. In this regard, the predetermined suction count may prevent false positives by requiring several clustered confirmations of the comparisons in step 612 to trigger an alarm condition to indicate that a suction event is occurring. In one aspect, the predetermined suction count is set to four, although in accordance with the present disclosure, the predetermined suction count may be more or less than four. In one embodiment, the predetermined suction count may be adjustable by the user, for example, via user input to the user interface 206.

[0040] For example, returning to method 600 of FIG. 6, when suction is not detected based on the comparison in step 612, processor 204 decrements or decreases the counter by one in step 616. Alternatively, when suction is detected based on the comparison in step 612, processor 204 increments or increases the counter by one in step 620. As discussed above, if the counter is 0, processor 204 does not decrement the counter below 0, i.e., 0 is the floor of the counter. In step 622, processor 204 determines whether the counter has reached a predetermined suction count. If in step 622, processor 204 determines that the counter has not reached a predetermined suction count, processor 204 returns to monitoring the MC signal in step 602 and method 600 is executed again. Alternatively, if in step 622 the processor 204 determines that the counter has reached a predetermined aspiration count, the processor 204 in step 620 triggers an alarm condition, alerting a user of the pump 100 that a aspiration event has been detected, and the processor 204 resets the counter to zero. The alarm condition may include triggering one or more indicators to alert the user of the detected alarm condition. For example, the indicator may include a light indicator (e.g., a light emitting diode (LED), an audible alarm, and / or a notification or message output for display on a display device, e.g., in the user interface 206 of the control unit 200). A light indicator and / or a speaker for outputting an audible alarm may be included in the user interface 206 control unit 200. The indicator may further include a vibration or haptic actuator (e.g., in the handle of the pump 100 to alert the user via haptic feedback). The indicator may include one of a light indicator, an audible alarm, a haptic actuator, and a notification, or a combination or subcombination of such indicators. After triggering the alarm condition and resetting the counter to zero at step 624 , the processor 204 returns to monitoring the MC signal at step 602 of the method 600 .

[0041] Although a stepped counter is described above for use in method 600, it should be understood that in other aspects of the present technology, other types of counters may be used to trigger an alarm condition. For example, in one aspect, processor 204 may control or maintain a counter (e.g., stored in memory 202) that keeps a count of the number of previous windows (e.g., 2 second windows as described above) of the filtered motor current signal that were determined by processor 204 to include an index of suction (detected in step 618 based on the comparison in step 612). If processor 204 determines that a predetermined number of windows (e.g., 4 of 7 previous windows, 5 of 8 previous windows, or another ratio) out of a predetermined total number of previous windows include an index of suction, processor 204 determines that a suction event has occurred and triggers an alarm condition.

[0042] In one aspect of the method 600, steps 614 and 618 may be eliminated, and in this aspect, the processor 204 may determine that a suction event has occurred only if a predetermined suction count in step 622 is reached.

[0043] In another aspect of method 600, steps 616, 620, and 622 (the steps relating to counters) may be removed from method 600, in which the processor 204 triggers an alarm condition if aspiration is detected in step 618 (based on the comparison in step 612) and returns to monitoring the motor current in step 602. If the processor 204 does not detect a suction condition in step 614, the method returns to monitoring the motor current in step 602.

[0044] Aspiration detection using normalized minimum bandpass signal Another embodiment of aspiration detection including additional signal filtering will now be described. For example, in this second embodiment, in addition to low-pass filtering the motor current (MC) signal (e.g., using a 15 Hz low-pass filter as described above), the motor current signal is further filtered by the processor 204 using a band-pass filter that passes frequencies within a second predetermined range, such as 0.5-5 Hz. The second predetermined range, e.g., 0.5-5 Hz, is selected based on a typical heart rate frequency range of 30-300 beats per minute (BPM). It should be appreciated that the second predetermined range may be 0.5-3 Hz, 0.5-5 Hz, 0.5-8 Hz, 0.5-10 Hz, or any other suitable range that includes sufficient information regarding the pulsatility of the patient's heart rate. The 0.5 Hz-5 Hz range may balance sensitivity and stability when used in this embodiment of aspiration detection described in more detail below.

[0045] The bandpass filtering is similar to extracting pulsatile information from the motor current signal, assuming a typical heart rate range of 30-300 BPM. The bandpass and lowpass filters may be digital filters applied by the processor 204 (e.g., filter software that may be stored in the memory 202 and executed by the processor 204). Alternatively, the processor 204 may control analog filter circuitry (including appropriate lowpass and bandpass filters), for example, included in the control unit 200 or external to the control unit 200, to lowpass and bandpass filter the motor current signal.

[0046] In one embodiment, the bandpass filter may be a 6th order elliptical filter that passes frequencies within a second predetermined range, for example 0.5-5 Hz. FIG. 8 shows a graph of the filter response of such an elliptical filter, where the y-axis represents gain (in dB) and the x-axis represents frequency (in Hz) for an elliptical filter that passes all frequencies in the range 0.5-5 Hz. Furthermore, in one embodiment, the lowpass filter may be a 2nd order Butterworth filter that passes frequencies in a first predetermined range, for example 0 Hz-15 Hz. FIG. 9 shows a graph of the filter response of such a Butterworth filter, where the y-axis represents gain (in dB) and the x-axis represents frequency (in Hz) for a Butterworth filter that passes all frequencies in the range 0-15 Hz.

[0047] As described above, the normalization of the signal used in the aspiration detection method allows for the use of an absolute threshold to detect aspiration events even when the motor current may vary over time (e.g., tend to decline). Thus, this aspect of the method described herein continues by normalizing the bandpass filtered signal. For example, in one aspect, the processor 204 normalizes the bandpass signal according to the following formula:

[0048]

number

[0049] The processor 204 then calculates a normalized minimum bandpass signal index (referred to herein as the MBS index) by detecting the minimum of the normalized bandpass filtered signal within a predefined window of the signal and evaluating the MBS index against a threshold. In one embodiment, the absolute value of the detected minimum within the predefined window (i.e., abs(MBS)) is compared to a threshold. Using the absolute value of the MBS makes it easier to determine a suction event. With reference to FIG. 15, in a bar graph of the normalized minimum bandpass signal (MBS), values ​​above a threshold are an indication of a suction event. Since the current represented by the MBS can be negative, values ​​that are "more negative" (i.e., less than but greater than the threshold in the absolute value sense) are an indication of "no suction". Using the absolute value of these negative values, the absolute value of the MBS value below the threshold is an indication of a suction event and abs(MBS) values ​​above the threshold are an indication of no suction. The predefined window for the MBS calculation can be 2 seconds, which is a window that can balance the reliability and stability of aspiration detection as explained above. However, other windows (e.g., 1 second, 3 seconds, 4 seconds, 5 seconds, etc.) are contemplated herein. Since the normalized bandpass filtered signal is normalized, the second predetermined threshold can be defined to account for the motor current varying (e.g., decreasing) across different pump speeds, pump types, and over time. The second predetermined threshold can then be compared to the abs(MBS) value of the normalized bandpass filtered motor current signal when the pump is in use to detect whether an aspiration event has occurred. For example, in one aspect, the second threshold may be about (e.g., + / - 10%) 0.07, with an abs(MBS) value below the second threshold indicating the occurrence of an aspiration event and an abs(MBS) value above the second threshold indicating the absence of an aspiration event. A second threshold of 0.07 has been found to balance sensitivity and stability when used to detect an aspiration event. It should be understood that other thresholds for comparison with abs(MBS) are contemplated herein. For example, the second threshold may be in the range of 0.05 to 0.12.It should be understood that a value at the lower end of this range, when used as a second threshold for comparison with abs(MBS), may result in increased sensitivity but decreased stability. Additionally, a value at the upper end of this range, when used as a second threshold for comparison with abs(MBS), may result in decreased sensitivity but increased stability.

[0050] The process of filtering and normalizing the motor current signal described above according to the present technique is illustrated in FIG. 10. For example, FIG. 10 includes graphs 1002, 1004, 1006, where the y-axis of each graph is motor current (in mA) and the x-axis of each graph is time (marked in 2 second increments). Graph 1002 shows the motor current of the pump, graph 1004 shows the motor current signal of graph 1002 after it has been low-pass filtered using the Butterworth filter described above and band-pass filtered using the elliptical filter described above, and graph 1006 shows the band-pass filtered signal after it has been normalized according to Equation 3 described above. The original motor current signal of graph 1002 was obtained during an animal study in which the motor speed was controlled in a stepwise manner (as shown in the stepwise motor current changes). At the end of each speed change, a suction event was simulated by inferior vena cava (IVC) occlusion (using an occlusion tool, as described below) and / or by placing the pump inlet near the aortic valve. The simulated suction events can be seen in the narrowing of the signal spacing in graphs 1004 and 1006, where the motor current pulsatility decreases during each suction event. By normalizing the bandpass filtered signal as shown in graph 1006, the filtered signal in graph 1006 acquires a more uniform shape, even taking into account the varying motor speed during the experiment. Thus, the different pulsatility of the bandpass filtered signal shown in graph 1004 is normalized for comparison against the second threshold value mentioned above. In this regard, the minimum of the normalized bandpass signal shown in graph 1006 is detected every 2 second window, and the absolute value of the minimum (i.e., the calculated MBS index) is compared to the second threshold value to determine whether a suction event has / has occurred within the evaluated window.

[0051] 11, there is shown a method 1100 for detecting aspiration events using the bandpass filtering, normalization, and MBS index values ​​described above during use of a pump, such as pump 100, in accordance with the present technology within a patient. It should be appreciated that method 1100 may be implemented or performed by one or more processors of a pump system, such as processor 204 of pump 100, using the pump motor current as the only input.

[0052] Initially, in step 1102, the processor 204 monitors the motor current of the pump motor after deployment of the pump into the patient and activation of the pump. In step 1104, the motor current signal is filtered using a low pass filter. For example, in one embodiment, a 15 Hz low pass filter, such as a second order Butterworth filter as described above, may be used to filter the motor current signal. In step 1106, the low pass filtered signal is band pass filtered by the processor 204 using a band pass filter that passes frequencies of the signal within a predetermined range, such as 0.5-5 Hz, as described above. For example, in another embodiment, a 6th order elliptical filter that passes frequencies in the range of 0.5 Hz-5 Hz may be used to filter the low pass filtered signal, as described above.

[0053] It should be understood that the filtering in method 1100 may be implemented digitally by processor 204. Alternatively, processor 204 may control analog filter circuitry (including appropriate low-pass and band-pass filters), for example, included in control unit 200 or external to control unit 200, to low-pass and band-pass filter the motor current signals.

[0054] In step 1108, the processor 204 calculates a normalized band-pass filtered signal of the band-pass signal by dividing each sample of the band-pass filtered signal of step 1106 by each corresponding sample of the low-pass filtered signal of step 1104 according to Equation 3 above. In step 1109, the processor 204 calculates the MBS index of the normalized band-pass filtered signal by finding the minimum value within a predetermined time window (e.g., 2 seconds) of the normalized band-pass filtered signal, and determines abs(MBS) from the calculated value. In step 1110, the processor 204 compares the abs(MBS) of step 1109 to a second threshold. As mentioned above, the second threshold may be 0.07 and may be used reliably across different pump speeds, pump types, and to account for fluctuating (e.g., downwardly trending) motor currents. If the processor 204 determines in step 1110 that abs(MBS) is not below (i.e., is greater than or equal to) the second threshold, the processor 204 determines in step 1112 that aspiration is not detected. Alternatively, if the processor 204 determines in step 1110 that abs(MBS) is less than the second threshold, the processor 204 determines in step 1120 that aspiration event is detected.

[0055] As mentioned above, to balance reliability and stability of aspiration detection, a counter may be implemented by the processor 204. The counter may be a graduated counter or any other suitable counter, as described above.

[0056] For example, returning to method 1100 of FIG. 11, when suction is not detected based on the comparison in step 1110, processor 204 decrements or decreases the counter by one in step 1114. Alternatively, when suction is detected based on the comparison in step 1110, processor 204 increments or increases the counter by one in step 1122. As discussed above, if the counter is 0, processor 204 does not decrement the counter below 0, i.e., 0 is the floor of the counter. In step 1124, processor 204 determines whether the counter has reached a predetermined suction count. If, in step 1124, processor 204 determines that the counter has not reached a predetermined suction count, processor 204 returns to monitoring the MC signal in step 1102 and method 1100 is executed again. Alternatively, if in step 1124 the processor 204 determines that the counter has reached the predetermined aspiration count, then in step 1126 the processor 204 triggers an alarm condition, alerting a user of the pump 100 that an aspiration event has been detected, and the processor 204 resets the counter to zero. The alarm condition may include triggering one or more indicators to alert a user of the detected alarm condition, as described above in connection with step 624 of method 600. After triggering the alarm condition and resetting the counter to zero in step 1126, the processor 204 returns to monitoring the MC signal in step 1102 of method 1100.

[0057] In another aspect of the method 1100, steps 1112 and 1120 may be eliminated, and in this aspect, the processor 204 may determine that a suction event has occurred only if a predetermined suction count in step 1124 is reached.

[0058] In another aspect of method 1100, steps 1114, 1122, and 1124 (the steps relating to counters) may be removed from method 1100, in which the processor 204 triggers an alarm condition if an aspiration event is detected in step 1120 (based on the comparison in step 1110) and returns to monitoring the motor current in step 1102. If the processor 204 does not detect a suction condition in step 1112, the method returns to monitoring the motor current in step 1102.

[0059] Aspiration detection using both PI and MBS indices In one aspect, the algorithms using the PI and MBS indices of motor current described above in connection with Figures 6 and 11 are combined according to another aspect of the method described herein. The combination of the PI and MBS indices in a single method may produce even more sensitive and stable results for aspiration detection.

[0060] 12, there is shown a method 1200 for detecting aspiration events using the PI and MBS indices of the motor current during use of a pump in a patient, such as pump 100, in accordance with the present technology. It should be appreciated that method 1200 may be implemented or performed by one or more processors of a pump, such as processor 204 of pump 100, using the pump's motor current as the only input.

[0061] 12, a method 1200 for detecting aspiration events using both the motor current PI and MBS index values ​​described above during use of a pump, such as pump 100, within a patient is shown in accordance with the present technique. It should be appreciated that method 1200 may be implemented or performed by one or more processors of a pump system, such as processor 204 of pump 100, using the pump motor current as the only input.

[0062] Initially, in step 1202, the processor 204 monitors the motor current of the pump motor after deployment of the pump into the patient and activation of the pump. In step 1204, the motor current signal is filtered using a low pass filter. For example, in one aspect, a 15 Hz low pass filter, such as a second order Butterworth filter as described above, may be used to filter the motor current signal. In step 1206, the low pass filtered signal is band pass filtered by the processor 204 using a band pass filter that passes frequencies of the signal within a predetermined range, such as 0.5-5 Hz, as described above. For example, in one aspect, a 6th order elliptical filter that passes frequencies in the range of 0.5 Hz-5 Hz may be used to filter the low pass filtered signal, as described above.

[0063] It should be understood that the filtering in method 1200 may be implemented digitally by processor 204. Alternatively, processor 204 may control analog filter circuitry (including appropriate low-pass and band-pass filters), for example, included in control unit 200 or external to control unit 200, to low-pass and band-pass filter the motor current signals.

[0064] In step 1208, the processor 204 calculates a normalized bandpass filtered signal of the bandpass signal by dividing each sample of the bandpass filtered signal of step 1206 by each corresponding sample of the lowpass filtered signal of step 1204 according to Equation 3 above. In step 1210, the processor 204 determines abs(MBS) by detecting a minimum within a predetermined time window (e.g., 2 seconds) of the normalized bandpass filtered motor current signal and calculating an MBS index of the normalized bandpass filtered signal by determining the absolute value of the detected minimum within the predetermined time window. In step 1212, the processor 204 calculates the PI of the motor current of the lowpass filtered signal of step 1204 according to Equation 2 above and in the manner described in connection with steps 606-610 above.

[0065] At step 1214, the processor 204 compares the calculated PI of the motor current at step 1212 to a first predetermined threshold (e.g., about 0.15 as described above), and the processor 204 compares the abs(MBS) determined at step 1210 to a second predetermined threshold (e.g., about 0.07 as described above). If at step 1214, both the PI and the abs(MBS) are less than the respective first and second thresholds, then a suction event is detected at 1220. If at step 1214, the processor 204 determines at least one of the calculated PI of the motor current exceeds the first predetermined threshold and / or the absolute value of the calculated MBS index exceeds the second threshold, then the processor 204 determines at step 1216 that suction is not detected.

[0066] It should be understood that while method 1200 requires both PI to be less than the first threshold and abs(MBS) to be less than the second threshold in step 1214 in order to detect an aspiration event in step 1220, other approaches may be appropriate depending on the specificity or sensitivity desired. In particular, the depicted method may promote specificity by requiring that both threshold conditions be met before detecting an aspiration event in step 1220. In other aspects, such as when increased sensitivity is preferred, aspiration may be detected when PI is less than the first threshold or abs(MBS) is less than the second threshold (i.e., aspiration is detected as long as one threshold condition is met).

[0067] As mentioned above, to balance reliability and stability of aspiration detection, a counter may be implemented by the processor 204. The counter may be a graduated counter or any other suitable counter, as described above.

[0068] For example, returning to method 1200 of FIG. 12, when suction is not detected based on the comparison in step 1214, processor 204 decrements or decreases the counter by one in step 1218. Alternatively, when suction is detected based on the comparison in step 2114, processor 204 increments or increases the counter by one in step 1222. As noted above, if the counter is 0, processor 204 does not decrement the counter below 0, i.e., 0 is the floor of the counter. In step 1224, processor 204 determines whether the counter has reached a predetermined suction count. If, in step 1224, processor 204 determines that the counter has not reached a predetermined suction count, processor 204 returns to monitoring the MC signal in step 1202 and method 1200 is executed again. Alternatively, if in step 1224 the processor 204 determines that the counter has reached a predetermined aspiration count, then in step 1226 the processor 204 triggers an alarm condition, alerting a user of the pump 100 that a aspiration event has been detected, and the processor 204 resets the counter to zero. The alarm condition may include triggering one or more indicators to alert a user of the detected alarm condition, as described above in connection with step 624 of method 600. After triggering the alarm condition and resetting the counter to zero in step 1226, the processor 204 returns to monitoring the MC signal in step 1202 of method 1200.

[0069] In one aspect of the method 1200, steps 1216 and 1220 may be eliminated, and in this aspect, the processor 204 may determine that a suction event has occurred only if a predetermined suction count in step 1224 is reached.

[0070] In another aspect of method 1200, steps 1218, 1222, and 1224 (steps relating to counters) may be removed from method 1200, in which the processor 204 triggers an alarm condition if an aspiration event is detected in step 1220 (based on the comparison in step 1214) and returns to monitoring the motor current in step 1202. If the processor 204 does not detect a suction condition in step 1216, the method returns to monitoring the motor current in step 1202.

[0071] Selection of PI and MBS thresholds There is often a trade-off between sensitivity and specificity in the methods described herein. In this regard, increasing the sensitivity of a method may decrease its specificity. With respect to the method 1200 described above, this trade-off depends on the selection of the first and second thresholds used to compare with the calculated PI and MBS indices, respectively. If the first threshold is about 0.15 and the second threshold is about 0.07, depending on the test conditions, the method 1200 has a specificity (+ / - 5%) of about 100% and a sensitivity (+ / - 5%) of about 70-90%.

[0072] Testing and Verification The aspiration detection method 1200 was tested and validated by inducing different aspiration and cardiac or pulse pressure conditions and testing the performance of the aspiration detection. For example, aspiration detection was tested in baseline and altered cardiac conditions (using pharmaceutical intervention), as well as under simulated induced aspiration events using mechanical intervention. For example, this is summarized in Table 1 below.

[0073] [Table 1]

[0074] As shown in the table above, three types of aspiration, IVC occlusion (using a circulatory occlusion tool (e.g., an inflatable balloon) to block flow to the ventricle, simulating IVC occlusion in a patient), pump placement at the apex, and pump inlet placement at the valve were induced during testing. Additionally, various cardiac or pulse pressure conditions were induced by the introduction of beta-blockers (to induce low pressure), phenylephrine (to induce high pressure), and microbead injection (to induce cardiogenic shock (CGS)).

[0075] Examples of tests performed when the pump speed was increased and under different aspiration conditions induced during animal studies are shown in Figure 13 according to the present technique. As shown, the motor current signal and the PI of the normalized bandpass signal were obtained according to Equations 2 and 3 above and were successfully used to detect aspiration events (IVC occlusion and valve inlet) within a 2 second window of the signal.

[0076] Table 2 below shows the different pressure conditions used during the tests performed.

[0077] [Table 2]

[0078] result Table 3 below contains a summary of the results of various tests of the aspiration detection method performed using different pumps, during animal studies or in simulated environments, with and without different types of induced aspiration, and under different induced pressure conditions.

[0079] [Table 3]

[0080] It should be understood that in the above table, "TP" is a true positive result where aspiration is correctly detected, "TN" is a true negative result where no aspiration is correctly detected, "FP" is a false positive where aspiration is incorrectly detected, and "FN" is a false negative where no aspiration is incorrectly detected.

[0081] As shown in Table 3, only two false positive results were observed during the animal and simulated benchtop tests performed. Table 4 below shows the calculations of the sensitivity and specificity achieved during the testing of the aspiration detection of the present technology. As shown, a very high specificity of 98% and a good sensitivity of 79% were achieved by the aspiration detection method using the PI and MBS index of the present technology in the test summarized above.

[0082] [Table 4]

[0083] It should be understood that the duration of the aspiration event may affect the sensitivity and aspiration detection. For example, referring to FIG. 14, the results of a further animal study conducted are shown, in which the duration of each induced aspiration event (IVC occlusion) was increased (as long as it was tolerated by the animal) and the pump speed was increased. During this animal study, aspiration detection using the PI and MBS indexes was able to detect aspiration in hypertensive conditions at various pump speeds. The specificity of aspiration detection was about 100% (+ / - 5%), and the sensitivity of aspiration detection was about 89% (+ / - 5%).

[0084] 15, results of applying the suction detection method 1200 of the present technology to human study data are shown. As shown, the suction detection method 1200 retrospectively detected and confirmed suction events in the human study data inferred from pulsatility index information.

[0085] 13-15, as mentioned above, the current of the normalized minimum bandpass signal may be negative. Therefore, as mentioned above, to take into account the negative current of the normalized minimum bandpass signal in aspiration detection, the MBS index may be calculated by detecting the minimum value of the normalized minimum bandpass signal within a predetermined window of the signal, and then the absolute value of the detected minimum value (abs(MBS)) is compared with a second predetermined threshold to determine to detect an aspiration event (if abs(MBS) is less than the threshold).

[0086] It should be appreciated that in any of the above described methods, the parameters of the method, e.g., the predetermined time window and thresholds used for detection of aspiration events, may be adjustable by a user via user input to the control unit 200 (e.g., user input to the user interface 206). Additionally, the particular aspiration detection method used (e.g., methods 600, 1100, 1200) may also be selectable by a user via user input to the control unit 200.

[0087] It should be appreciated that in any of the above methods, in response to an aspiration event being detected (or an alarm condition being triggered), the processor 204 may output a notification message to the user (e.g., displayed via the interface 206) or otherwise communicate to the user (e.g., via an indicator light, audible message, etc.) to slow down the pump speed so that the aspiration event may be resolved. In one aspect, the alarm condition in the above methods includes a message or other communication to the user to slow down the pump speed. In one aspect, in response to an aspiration event being detected (or an alarm condition being triggered), the processor 204 may automatically control the motor current to slow down the pump speed to a predetermined speed threshold to resolve the aspiration event.

[0088] In one aspect, a blood pump is provided that includes an inlet, an outlet, a rotor, a motor for driving rotation of the rotor to transport blood from the inlet to the outlet, and at least one processor configured to monitor a motor current signal of the motor, filter the motor current signal, calculate a pulsatility index of the motor current signal based on the filtered motor current signal, compare the calculated pulsatility index to a predetermined threshold, and detect an occurrence of a suction event based on the comparison.

[0089] In any of the above aspects, the motor current signal may be filtered using a low pass filter.

[0090] In any of the above embodiments, the low-pass filter may be a second-order Butterworth filter.

[0091] In any of the above aspects, the low-pass filter may pass frequencies from 0 Hz to 15 Hz.

[0092] In any of the above aspects, the at least one processor may be configured to calculate a pulsatility index of the motor current signal by detecting a maximum motor current (max MC) and a minimum motor current (min MC) within a predetermined window of the filtered motor current signal, calculating a mean motor current (mean MC) within the predetermined window of the filtered motor current signal, and calculating a pulsatility index of the motor current signal according to Equation 4 below.

[0093]

number

[0094] In any of the above aspects, the predetermined window may be about 2 seconds.

[0095] In any of the above aspects, the predetermined threshold may be about 0.15.

[0096] In any of the above aspects, the occurrence of a suction event may be detected when the calculated pulsatility index is below a predetermined threshold.

[0097] In any of the above aspects, the at least one processor can be configured to maintain a suction counter that includes a suction count representative of the number of detected suction events.

[0098] In any of the above aspects, the at least one processor may be configured to trigger an alarm condition when the counter reaches a predetermined suction count to alert a user that a suction event is occurring.

[0099] In any of the above aspects, the predetermined suction count may be four.

[0100] In any of the above aspects, the at least one processor may be configured to increment a counter by one when an occurrence of a suction event is detected and to decrement the counter by one when an occurrence of a suction event is not detected.

[0101] In any of the above aspects, the at least one processor may be configured to detect the occurrence of a suction event without information regarding the sensed blood pressure.

[0102] In any of the above aspects, the blood pump may be a cardiac pump insertable into a ventricle of the patient's heart.

[0103] In another aspect, a blood pump is provided that includes an inlet, an outlet, a rotor, a motor for driving rotation of the rotor to transport blood from the inlet to the outlet, and at least one processor configured to monitor a motor current signal of the motor, low-pass filter the motor current signal, band-pass filter the low-pass filtered motor current signal, normalize the band-pass filtered motor current signal, calculate an index value based on the normalized band-pass filtered motor current signal, compare the calculated index value to a predetermined threshold, and detect the occurrence of a suction event based on the comparison.

[0104] In any of the above aspects, the motor current signal may be low pass filtered using a second order Butterworth filter.

[0105] In any of the above aspects, the motor current signal may be low pass filtered using a low pass filter that passes frequencies between 0 Hz and 15 Hz.

[0106] In any of the above aspects, the low-pass filtered motor current signal may be band-pass filtered using a sixth order elliptic filter.

[0107] In any of the above aspects, the low-pass filtered motor current signal may be band-pass filtered using a band-pass filter that passes frequencies between 0.5 Hz and 5 Hz.

[0108] In any of the above aspects, the at least one processor may be configured to calculate the exponent value by detecting a minimum value within a predetermined window of the normalized bandpass filtered motor current signal and calculating an absolute value of the detected minimum value within the predetermined window.

[0109] In any of the above aspects, the predetermined window may be about 2 seconds.

[0110] In any of the above aspects, the at least one processor may calculate a normalized bandpass filtered motor current signal by dividing each sample in the bandpass filtered motor current signal by a corresponding each sample in the lowpass filtered motor current signal.

[0111] In any of the above aspects, the predetermined threshold may be about 0.07.

[0112] In any of the above aspects, the occurrence of a suction event may be detected when the calculated index value falls below a predetermined threshold.

[0113] In any of the above aspects, the at least one processor can be configured to maintain a suction counter that includes a suction count representative of the number of detected suction events.

[0114] In any of the above aspects, the at least one processor may be configured to trigger an alarm condition when the counter reaches a predetermined suction count to alert a user that a suction event is occurring.

[0115] In any of the above embodiments, the predetermined suction count may be four.

[0116] In any of the above aspects, the at least one processor may be configured to increment a counter by one when an occurrence of a suction event is detected and to decrement the counter by one when an occurrence of a suction event is not detected.

[0117] In any of the above aspects, the at least one processor may be configured to detect the occurrence of a suction event without information regarding the sensed blood pressure.

[0118] In any of the above aspects, the blood pump may be a cardiac pump insertable into a ventricle of the patient's heart.

[0119] In another aspect, a blood pump is provided that includes an inlet, an outlet, a rotor, a motor that drives rotation of the rotor to transport blood from the inlet to the outlet, and at least one processor configured to monitor a motor current signal of the motor, low pass filter the motor current signal, calculate a pulsatility index of the motor current signal based on the low pass filtered motor current signal, band pass filter the low pass filtered motor current signal, normalize the band pass filtered motor current signal, calculate an index value based on the normalized band pass filtered signal, compare the calculated pulsatility index to a first predetermined threshold, compare the calculated index value to a second predetermined threshold, compare the calculated pulsatility index to the first predetermined threshold, and detect an occurrence of a suction event based on comparing the calculated index value to the second predetermined threshold.

[0120] From the above and with reference to the various figures, those skilled in the art will understand that certain modifications can be made to the present disclosure without departing from the scope of the present disclosure. Although several aspects of the present disclosure are shown in the drawings, the present disclosure is not intended to be limited to these embodiments, as it is intended that the present disclosure should be accorded as broad scope as the art will permit, and that the specification should be read in the same manner. Thus, the above description should not be construed as limiting, but merely as exemplification of certain aspects. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

1. 1. A blood pump comprising: an entrance and an exit; A rotor, a motor that drives the rotor to rotate and transport blood from the inlet to the outlet; and at least one processor, wherein the at least one processor: monitoring a motor current signal of the motor; filtering the motor current signal; calculating a pulsatility index of the motor current signal based on the filtered motor current signal; comparing the calculated pulsatility index to a predetermined threshold; The blood pump is configured to detect the occurrence of a suction event based on the comparison.

2. The blood pump of claim 1 , wherein the motor current signal is filtered using a low pass filter.

3. 3. The blood pump of claim 2, wherein the low-pass filter is a second-order Butterworth filter or passes frequencies between 0 Hz and 15 Hz.

4. 1. A blood pump, comprising: detecting a maximum motor current (max MC) and a minimum motor current (min MC) within a predetermined window of the filtered motor current signal; Calculating an average motor current (average MC) within the predetermined window of the filtered motor current signal; According to the formula below, [Equation 1] 4. A blood pump according to claim 1, configured to calculate the pulsatility index of the motor current signal by calculating the pulsatility index of the motor current signal.

5. 5. The blood pump of claim 4, wherein the predetermined window is about 2 seconds.

6. 2. The blood pump of claim 1, wherein the predetermined threshold is approximately 0.

15.

7. The blood pump of claim 6 , wherein the occurrence of the suction event is detected when the calculated pulsatility index is less than the predetermined threshold.

8. 10. The blood pump of claim 1, wherein the at least one processor is configured to maintain a suction counter including a suction count representative of a number of detected suction events, or to trigger an alarm condition when the suction counter reaches a predetermined suction count to alert a user that a suction event is occurring.

9. 9. The blood pump of claim 8, wherein the predetermined aspiration count is four.

10. 9. The blood pump of claim 8, wherein the at least one processor is configured to increment the suction counter by one when an occurrence of a suction event is detected and to decrement the suction counter by one when the occurrence of a suction event is not detected.

11. The blood pump of claim 1 , wherein the at least one processor is configured to detect the occurrence of the aspiration event without information regarding sensed blood pressure.

12. 10. The blood pump of claim 1, wherein the blood pump is a cardiac pump insertable into a ventricle of a patient's heart.

13. 1. A blood pump comprising: an entrance and an exit; A rotor, a motor that drives the rotor to rotate and transport blood from the inlet to the outlet; and at least one processor, wherein the at least one processor: monitoring a motor current signal of the motor; low pass filtering the motor current signal; band-pass filtering the low-pass filtered motor current signal; normalizing the bandpass filtered motor current signal; calculating an index value based on the normalized bandpass filtered motor current signal; comparing the calculated index value to a predetermined threshold; The blood pump is configured to detect the occurrence of a suction event based on the comparison.

14. 14. The blood pump of claim 13, wherein the motor current signal is low-pass filtered using a second order Butterworth filter or a low-pass filter that passes frequencies between 0 Hz and 15 Hz.

15. 15. The blood pump of claim 14, wherein the low-pass filtered motor current signal is band-pass filtered using a sixth-order elliptic filter.

16. 14. The blood pump of claim 13, wherein the low-pass filtered motor current signal is band-pass filtered using a band-pass filter that passes frequencies between 0.5 Hz and 5 Hz.

17. 14. The blood pump of claim 13, wherein the at least one processor is configured to detect a minimum value within a predetermined window of the normalized bandpass filtered motor current signal and calculate the index value by determining an absolute value of the detected minimum value within the predetermined window.

18. 18. The blood pump of claim 17, wherein the predetermined window is about 2 seconds.

19. 14. The blood pump of claim 13, wherein the at least one processor calculates the normalized bandpass filtered motor current signal by dividing each sample in the bandpass filtered motor current signal by each corresponding sample in the lowpass filtered motor current signal.

20. 14. The blood pump of claim 13, wherein the predetermined threshold is about 0.

07.

21. 14. The blood pump of claim 13, wherein the occurrence of the suction event is detected when the calculated index value is less than the predetermined threshold.

22. 14. The blood pump of claim 13, wherein the at least one processor is configured to maintain a suction counter including a suction count representative of a number of detected suction events, or to trigger an alarm condition when the suction counter reaches a predetermined suction count to alert a user that a suction event is occurring.

23. 23. The blood pump of claim 22, wherein the predetermined suction count is four.

24. 23. The blood pump of claim 22, wherein the at least one processor is configured to increment the suction counter by one when an occurrence of a suction event is detected and to decrement the suction counter by one when the occurrence of a suction event is not detected.

25. 14. The blood pump of claim 13, wherein the at least one processor is configured to detect the occurrence of the aspiration event without information regarding sensed blood pressure.

26. 14. The blood pump of claim 13, wherein the blood pump is a cardiac pump insertable into a ventricle of a patient's heart.

27. 1. A blood pump comprising: an entrance and an exit; A rotor, a motor that drives the rotor to rotate and transport blood from the inlet to the outlet; and at least one processor, wherein the at least one processor: monitoring a motor current signal of the motor; low pass filtering the motor current signal; calculating a pulsatility index of the motor current signal based on the low-pass filtered motor current signal; band-pass filtering the low-pass filtered motor current signal; normalizing the bandpass filtered motor current signal; calculating an index value based on the normalized bandpass filtered signal; comparing the calculated pulsatility index to a first predetermined threshold and comparing the calculated index value to a second predetermined threshold; and detecting the occurrence of a suction event based on the comparison of the calculated pulsatility index value with the first predetermined threshold and the comparison of the calculated index value with the second predetermined threshold.

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