Pressure/flow characteristic modification of a centrifugal pump in a ventricular assist device

1. A ventricular assist device comprising:

a centrifugal pump comprising a motor; and

at least one processor configured to:

determine an estimated flow rate through the centrifugal pump based on a current of the motor;

cause the motor to operate at a first speed when the estimated flow rate is greater than a predetermined flow rate during a user's systolic period; and

cause the motor to operate at a second speed when the estimated flow rate is less than the predetermined flow rate, wherein the predetermined flowrate corresponds to a particular flowrate through the centrifugal pump during a transition between systole and diastole phases of a person's cardiac cycle.

2. The ventricular assist device of claim 1 , wherein:

the second speed is greater than the first speed.

3. The ventricular assist device of claim 1 , wherein:

at least one of the first speed or the second speed is set by a clinician.

4. The ventricular assist device of claim 1 , wherein:

when the motor is operating at the second speed, the motor is operating at a constant current.

5. The ventricular assist device of claim 1 , wherein causing the motor of the centrifugal pump to operate at the second speed comprises:

controlling the motor to maintain at least one parameter at a substantially constant value, wherein the at least one parameter is selected from a group consisting of: motor current, motor voltage, motor power, and back electromotive force.

6. The ventricular assist device of claim 1 , wherein the at least one processor is further configured to:

identify a suction event in the centrifugal pump; and

reduce a speed of the motor to alleviate the suction event.

7. The ventricular assist device of claim 1 , wherein:

the ventricular assist device further comprises a flow measurement sensor; and

determining the estimated flow is further based on a signal from the flow measurement sensor.

8. A method for controlling a ventricular assist device comprising:

determining an estimated flow rate through a centrifugal pump based on a current of a motor of the centrifugal pump;

causing the motor to operate at a first speed when the estimated flow rate is greater than a predetermined flow rate during a user's systolic period; and

causing the motor to operate at a second speed when the estimated flow rate is less than the predetermined flow rate, wherein the predetermined flowrate corresponds to a particular flowrate through the centrifugal pump during a transition between systole and diastole phases of a person's cardiac cycle.

9. The method for controlling a ventricular assist device of claim 8 , wherein:

the second speed is greater than the first speed.

10. The method for controlling a ventricular assist device of claim 8 , wherein:

at least one of the first speed or the second speed is set by a clinician.

11. The method for controlling a ventricular assist device of claim 8 , wherein:

when the motor is operating at the second speed, the motor is operating at a constant current.

12. The method for controlling a ventricular assist device of claim 8 , wherein causing the motor of the centrifugal pump to operate at the second speed comprises:

controlling the motor to maintain at least one parameter at a substantially constant value, wherein the at least one parameter is selected from a group consisting of: motor current, motor voltage, motor power, and back electromotive force.

13. The method for controlling a ventricular assist device of claim 8 , wherein the method further comprises:

identifying a suction event in the centrifugal pump; and

reducing a speed of the motor to alleviate the suction event.

14. The method for controlling a ventricular assist device of claim 8 , wherein:

determining the estimated flow is further based on a signal from a flow measurement sensor.

15. A non-transitory machine readable medium having instructions stored thereon for controlling a ventricular assist device, wherein the instructions are executable by at least one processor to perform steps comprising:

determining an estimated flow rate through a centrifugal pump based on a current of a motor of the centrifugal pump;

causing the motor to operate at a first speed when the estimated flow rate is greater than a predetermined flow rate during a user's systolic period; and

causing the motor to operate at a second speed when the estimated flow rate is less than the predetermined flow rate, wherein the predetermined flowrate corresponds to a particular flowrate through the centrifugal pump during a transition between systole and diastole phases of a person's cardiac cycle.

16. The non-transitory machine readable medium of claim 15 , wherein:

at least one of the first speed or the second speed is set by a clinician.

17. The non-transitory machine readable medium of claim 15 , wherein:

when the motor is operating at the second speed, the motor is operating at a constant current.

18. The non-transitory machine readable medium of claim 15 , wherein causing the motor of the centrifugal pump to operate at the second speed comprises:

controlling the motor to maintain at least one parameter at a substantially constant value, wherein the at least one parameter is selected from a group consisting of: motor current, motor voltage, motor power, and back electromotive force.

19. The non-transitory machine readable medium of claim 15 , wherein the instructions are further executable by the at least one processor to perform steps comprising:

identifying a suction event in the centrifugal pump; and

reducing a speed of the motor to alleviate the suction event.

20. The non-transitory machine readable medium of claim 15 , wherein:

determining the estimated flow is further based on a signal from a flow measurement sensor.