Cardiac pump with speed adapted for ventricle unloading
A blood pump system is implantable in a patient for ventricular support. A pumping chamber has an inlet for receiving blood from a ventricle of the patient. An impeller is received in the pumping chamber. A motor is coupled to the impeller for driving rotation of the impeller. A motor controller is provided for tracking systolic and diastolic phases of a cardiac cycle of the patient and supplying a variable voltage signal to the motor in a variable speed mode to produce a variable impeller speed linked to the cardiac cycle. The impeller speed comprises a ramping up to an elevated speed during the diastolic phase in order to reduce a load on the ventricle at the beginning of the systolic phase.
1. A blood pump, comprising:
a chamber;
an impeller disposed within the chamber;
a motor that is configured to drive the impeller; and
at least one processor that:
determines an average speed of the motor;
determines an offset from the average speed for one or both of an elevated speed and a reduced speed based on a measurement from a physiological sensor;
determines an instantaneous speed of the motor, wherein the instantaneous speed comprises the elevated speed or the reduced speed; and
generates voltage outputs using field oriented control to adjust the speed of the motor by a magnitude of the offset associated with the instantaneous speed.
2. The blood pump of claim 1 , wherein:
determining the instantaneous speed of the motor comprises:
measuring a phase current in at least two phases; and
estimating a speed of the impeller based on the measured phase currents.
3. The blood pump of claim 2 , wherein:
determining the instantaneous speed of the motor further comprises calculating an additional phase current; and
estimating the speed of the impeller is further based on the additional phase current.
4. The blood pump of claim 3 , wherein:
the instantaneous speed is based at least in part on a signal from a pacemaker.
5. The blood pump of claim 1 , wherein:
the motor is operable in a constant current mode.
6. The blood pump of claim 1 , wherein:
the motor is operable in a variable speed mode.
7. The blood pump of claim 1 , wherein:
the speed of the motor is adjusted synchronously with a cardiac cycle.
8. A method of operating a blood pump, comprising:
determining an average speed of a motor of the blood pump;
determining an offset from the average speed for one or both of an elevated speed and a reduced speed based on a measurement from a physiological sensor;
determining an instantaneous speed of the motor, wherein the instantaneous speed comprises the elevated speed or the reduced speed; and
generating voltage outputs using field oriented control to adjust the speed of the motor by a magnitude of the offset associated with the instantaneous speed.
9. The method of operating a blood pump of claim 8 , further comprising:
receiving a status signal that indicates that a ventricle of a heart is in a highly weakened state or whether a predetermined recovery has been obtained in a strength of the ventricle; and
determining whether a various speed control needs to be used to unload the ventricle based on the status signal.
10. The method of operating a blood pump of claim 8 , further comprising:
determining a heart rate of a patient, wherein a timing of the generation of the voltage outputs is based at least in part on the heart rate.
11. The method of operating a blood pump of claim 8 , further comprising:
operating the motor in a variable speed mode or a constant speed mode.
12. The method of operating a blood pump of claim 11 , wherein:
selection of the variable speed mode or the constant speed mode is determined based on a physiological capability of a patient.
13. The method of operating a blood pump of claim 12 , wherein:
the variable speed mode is selected when a left ventricle of the patient is weak; and
the constant speed mode is selected when the left ventricle has recovered.
14. The method of operating a blood pump of claim 11 , wherein:
in the variable speed mode, the speed of the motor changes inversely with a flow rate through the blood pump.
15. A non-transitory computer-readable medium having instructions stored thereon that, when executed by at least one processor cause the at least one processor to:
determine an average speed of a motor of a blood pump;
determine an offset from the average speed for one or both of an elevated speed and a reduced speed based on a measurement from a physiological sensor;
determine an instantaneous speed of the motor, wherein the instantaneous speed comprises the elevated speed or the reduced speed; and
generate voltage outputs using field oriented control to adjust the speed of the motor by a magnitude of the offset associated with the instantaneous speed.
16. The non-transitory computer-readable medium of claim 15 , wherein:
the average speed is provided by a physiological monitor.
17. The non-transitory computer-readable medium of claim 15 , wherein:
the average speed is provided by a medical caregiver.
18. The non-transitory computer-readable medium of claim 15 , wherein the instructions further cause the at least one processor to:
determine a heart rate of a patient, wherein a timing of the generation of the voltage outputs is based at least in part on the heart rate.
19. The non-transitory computer-readable medium of claim 15 , wherein the instructions further cause the at least one processor to:
operate the motor in a variable speed mode or a constant speed mode.
20. The non-transitory computer-readable medium of claim 19 , wherein:
selection of the variable speed mode or the constant speed mode is determined based on a physiological capability of a patient.