US-20260124440-A1 - SUCTION DETECTION METHODS AND DEVICES

US20260124440A1US 20260124440 A1US20260124440 A1US 20260124440A1US-20260124440-A1

Abstract

A method of detecting a suction condition during operation of a rotary blood pump with an inlet connected to a ventricle of the heart of a patient, an outlet connected to an artery of the patient, a rotor, and a control circuit configured maintain the rotor at a set rotational speed. The method includes measuring the rotational speed of the rotor at a plurality of times during each of a plurality of speed measurement intervals. A speed range is determined between a minimum measured speed and a maximum measured speed during each of the plurality of speed measurement intervals. At least one additional parameter relating to the operation of the blood pump is derived. A suction detection signal is generated if both at least one determined speed range is above a speed range limit and the at least one additional parameter is indicative of a suction condition.

Inventors

Michael C. Brown
Neil Voskoboynikov

Assignees

BOSTON SCIENTIFIC SCIMED, INC.

Dates

Publication Date: 20260507
Application Date: 20251027

Claims (20)

1 . A method of detecting a suction condition during operation of a blood pump at a set rotational speed, the method comprising: monitoring, by a control circuit configured to maintain a speed of a rotor of the blood pump within a range around the set rotational speed, a flow rate of blood through the blood pump for a period of time during one or more cardiac cycles of a patient; determining, by the control circuit, a duty parameter representing a proportion of the period of time during which the flow rate is above a crossover flow rate; generating, by the control circuit, a suction detect signal based at least in part on the duty parameter; and altering operation of the blood pump in response to the suction detect signal.
2 . The method of claim 1 , wherein generating the suction detect signal includes: comparing, by the control circuit, the duty parameter with a duty limit corresponding to a set proportion of the period of time; and generating, by the control circuit, the suction detect signal based at least in part on the comparison.
3 . The method of claim 2 , wherein generating the suction detect signal comprises generating the suction detect signal in response to determining that the duty parameter represents a proportion above the set proportion.
4 . The method of claim 2 , wherein the period of time is during a single cardiac cycle, and wherein generating the suction detect signal comprises generating the suction detect signal in response to determining that the duty parameter represents a proportion above the set proportion.
5 . The method of claim 1 , further comprising: deriving, by the control circuit, at least one additional parameter relating to operation of the blood pump; generating, by the control circuit, at least one additional signal in response to determining that the at least one additional parameter is indicative of the suction condition; and altering, by the control circuit, operation of the blood pump in response to generating the at least one additional signal and based on the duty parameter.
6 . The method of claim 5 , wherein deriving the at least one additional parameter includes: measuring, by the control circuit, the speed of the rotor of the blood pump at a plurality of times during one or more speed measurement intervals at least partially encompassing the one or more cardiac cycles; and determining, by the control circuit, a measured speed range between a minimum measured speed and a maximum measured speed during each speed measurement interval.
7 . The method of claim 5 , wherein generating the at least one additional signal comprises generating a speed range signal in response to determining that the measured speed range exceeds a range limit.
8 . The method of claim 1 , further comprising: determining, by the control circuit, an average flow rate; and determining, by the control circuit, the crossover flow rate as a function of the average flow rate.
9 . The method of claim 8 , wherein the crossover flow rate is equal to the average flow rate.
10 . The method of claim 9 , further comprising: altering, by the control circuit, operation of the blood pump responsive to the suction detect signal.
11 . The method of claim 1 , wherein determining, by the control circuit, the duty parameter comprises: determining, by the control circuit, a plurality of flow rate estimates during the period of time: determining, by the control circuit, a number of the plurality of flow rate estimates that are above the crossover flow rate; and determining, by the control circuit, the duty parameter based on the number of the plurality of flow rate estimates that are above the crossover flow rate.
12 . A device comprising: a memory; and one or more processors implemented in circuitry, coupled to the memory, and configured to: maintain a speed of a rotor of a blood pump within a range around a set rotational speed, wherein the blood pump is set at the set rotational speed; monitor a flow rate of blood through a blood pump for a period of time during one or more cardiac cycles of a patient; determine a duty parameter representing a proportion of the period of time during which the flow rate is above a crossover flow rate; generate a suction detect signal based at least in part on the duty parameter; and alter operation of the blood pump in responsive to the suction detect signal.
13 . The device of claim 12 , wherein to generate the suction detect signal, the one or more processors are further configured to: compare the duty parameter with a duty limit corresponding to a set proportion of the period of time; and generate the suction detect signal based at least in part on the comparison.
14 . The device of claim 13 , wherein the one or more processors are further configured to generate the suction detect signal in response to determining that the duty parameter represents a proportion above the set proportion.
15 . The device of claim 13 , wherein the period of time is during a single cardiac cycle, and wherein the one or more processors are further configured to generate the suction detect signal in response to determining that the duty parameter represents a proportion above the set proportion.
16 . The device of claim 12 , wherein the one or more processors are further configured to: derive at least one additional parameter relating to operation of the blood pump; generate at least one additional signal in response to determining that the at least one additional parameter is indicative of the suction condition; and alter operation of the blood pump in response to generating the at least one additional signal and based on the duty parameter.
17 . The device of claim 16 , wherein to derive the at least one additional parameter, the one or more processors are further configured to: measure the speed of the blood pump at a plurality of times during one or more speed measurement intervals at least partially encompassing the one or more cardiac cycles; and determine a measured speed range between a minimum measured speed and a maximum measured speed during each speed measurement interval.
18 . The device of claim 16 , wherein: to generate the at least one additional signal, the one or more processors are further configured to generate a speed range signal in response to determining that the measured speed range exceeds a range limit.
19 . The device of claim 12 , wherein the one or more processors are further configured to: determine an average flow rate; and determine the crossover flow rate as a function of the average flow rate.
20 . The device of claim 12 , wherein the one or more processors are further configured to alter operation of the blood pump responsive to the suction detect signal.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a Continuation application of U.S. patent application Ser. No. 16/860,594, which is a Divisional of U.S. patent application Ser. No. 15/665,718, filed Aug. 1, 2017, now U.S. Pat. No. 10,675,396 and is related to and claims priority to U.S. Provisional Patent Application Ser. No. 62/369,295, filed Aug. 1, 2016, entitled SUCTION DETECTION METHODS AND DEVICES, the entirety of which is incorporated herein by reference. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT N/a TECHNICAL FIELD The present invention relates to a method and system for detecting suction conditions in a patient having an implantable blood pump. BACKGROUND Implantable blood pumps may be used to provide assistance to patients with late stage heart disease. Blood pumps operate by receiving blood from a patient's vascular system and impelling the blood back into the patient's vascular system. By adding momentum and pressure to the patient's blood flow, blood pumps may augment or replace the pumping action of the heart. For example, a blood pump may be configured as a ventricular assist device or “VAD.” Where a VAD is used to assist the pumping action of the left ventricle, the device draws blood from the left ventricle of the heart and discharges the blood into the aorta. To provide clinically useful assistance to the heart, blood pumps impel blood at a substantial blood flow rate. For an adult human patient, a ventricular assist device may be arranged to pump blood at about 1-10 liters per minute at a differential pressure across the pump of about 10-110 mm Hg, depending on the needs of the patient. The needs of the patient may vary with age, height, and other factors. If a VAD is operated at an average flow rate in excess of the average inflow rate of blood to the ventricle, the VAD will create a suction condition within the ventricle, wherein the ventricle is collapsed and essentially devoid of blood. This condition is undesirable. For example, in such a condition the wall of the ventricle may collapse in such a way that the wall occludes the pump inlet, causing the flow rate through the pump to decline rapidly, leading to inadequate blood perfusion. Moreover, if a suction condition is maintained for a prolonged period, it can cause damage to the heart. Accordingly, as disclosed, for example, in U.S. Patent Application Publication Nos. 2015/0367048 (“the '048 Publication”) and 2014/0100413 (“the '413 Publication”), the disclosures of which are incorporated by reference herein, VAD control systems have been arranged to detect suction conditions. For example, the '048 Publication discloses methods in which the control system associated with the pump acquires data representing flow rate through the pump and examines this data to detect a suction condition. In one embodiment, the control system examines the minimum flow rate occurring during one or more cardiac cycles, the amplitude of the flow rate waveform and the average flow rate to yield a calculated value. The control system may examine a plurality of these calculated values representing several cardiac cycles and determine properties such as the mean, median, mode and standard deviation of such values to determine whether or not a suction condition exists. As disclosed in the '413 Publication, the control system may compare a minimum flow rate occurring during a current cardiac cycle against a threshold which is set based on minima of previous cardiac cycles, and determine that a suction condition exists if the minimum flowrate for the current cardiac cycle is below the threshold. In either case, the control system may respond to detection of a suction condition by altering operation of the pump as, for example, by reducing the set rotational speed of the rotor, in an effort to clear the suction condition, by issuing an alarm signal, or both. Despite these and other improvements in the art, still further improvements would be desirable. For example, systems based on thresholds established during previous cardiac cycles can be susceptible to false alarms when the set rotational speed of the rotor is deliberately changed. In some cases, the suction detection function is disabled during speed changes, during pump startup or both. Moreover, if a suction condition exists immediately after startup of the VAD or when the detection system is re-enabled after being disabled, the thresholds may be set based on conditions prevailing during the suction condition, and the system may ignore the suction condition. SUMMARY The present invention advantageously provides a method of detecting a suction condition during operation of a rotary blood pump with an inlet connected to a ventricle of the heart of a patient, an outlet connected to an artery of the patient, a rotor, and a control circuit configured maintain the rotor at a set rotational speed. The method includes measuring the rotational speed of the rotor at a plurality of t