SUCTION DETECTION METHODS AND DEVICES
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.
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.