Chronic performance control system for rotodynamic blood pumps

• US 20040152944A1
• Filed: 04/01/2004
• Published: 08/05/2004
• Est. Priority Date: 03/27/2000
• Status: Active Grant

• Current Assignee: Alexander Massiello, Alexander Medvedev, Leonard A.R. Golding
• Original Assignee: Alexander Massiello, Alexander Medvedev, Leonard A.R. Golding
• Inventors: Golding, Leonard A R, Medvedev, Alexander, Massiello, Alexander
• Granted Patent: US 7,645,225 B2
• Time in Patent Office: Days
• US Class Current: 600/17
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• CPC Class Codes: A61M 2205/3365 Rotational speed
• CPC Class Codes: A61M 60/148 in line with a blood vessel using resection or like techniques, e.g. permanent endovascular heart assist devices
• CPC Class Codes: A61M 60/178 drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
• CPC Class Codes: A61M 60/221 the blood flow through the rotating member having both radial and axial components, e.g. mixed flow pumps
• CPC Class Codes: A61M 60/232 Centrifugal pumps
• CPC Class Codes: A61M 60/237 the blood flow through the rotating member having mainly axial components, e.g. axial flow pumps
• CPC Class Codes: A61M 60/411 generated by an electromotor
• CPC Class Codes: A61M 60/546 of blood flow, e.g. by adapting rotor speed

Abstract

In a left ventricular assist device (LVAD) a rotodynamic blood pump (10) is powered by a brushless DC motor (12). A power supply (14) supplies power to the motor (12). Three feedback channels, one for each of voltage, current, and motor speed lead to a microcontroller or microprocessor (18). The three feedback waveforms are analyzed, and from these waveforms, motor input power, patient heart rate, current pump flow rate, and systemic pressure are determined. The microprocessor (18) then calculates a desired flow rate proportional to the patient heart rate. The microprocessor communicates a new power output to a commutation circuit (16), which regulates power to the mortor (12). The pump (10) also includes safety checks that are prioritized over desired pump flow. These include prevention of ventricular suction, low pulsatility, minimum and maximum pump speed, minimum peed-relative pump flow, minimum absolute pump flow, minimum and maximum motor input power.

Claims

1. A cardiac assist apparatus comprising:

a blood pump;

a drive unit for driving the blood pump;

a power supply for supplying power to the drive unit;

a frequency sensor that senses a rotational speed of the blood pump;

a current sensor that senses an average direct current waveform of the drive unit;

a power supply voltage sensor that senses a power supply voltage; and

a blood pump controller that receives data from the frequency sensor, current sensor, and the power supply voltage sensor and controls operation of the blood pump in response thereto.

2. The cardiac assist apparatus as set forth in claim 1, wherein the controller estimates a drive unit input power, a flow rate, a patient heart rate, pressure and a desired flow rate.

3. The cardiac assist apparatus as set forth in claim 1, fisher comprising a drive unit winding commutation circuit for relaying the desired flow rate to the drive unit motor.

4. The cardiac assist apparatus as set forth in claim 1, wherein the drive unit includes a brushless DC motor.

5. The cardiac assist apparatus as set forth in claim 1, wherein the power supply includes at least one rechargeable battery.

6. The cardiac assist apparatus as set forth in claim 1, wherein the frequency sensor includes one of a back EMF, Hall and optical sensor.

7. The cardiac assist apparatus as set forth in claim 1, wherein the controller based on the input information, calculates:

a drive unit input power,

a heart rate;

a pump flow rate; and

,

a pressure differential.

8. The cardiac assist apparatus as set forth in claim 7, wherein the controller calculates a new pump flow rate based on the calculated heart rate.

9. The cardiac assist apparatus as set forth in claim 8, wherein the new flow rate is within a pre-determined margin.

10. The cardiac assist apparatus as set forth in claim 9, wherein the margin includes flow rates corresponding to preset maximum and minimum heartbeats per minute.

11. A method of controlling blood flow with a blood pump comprising:

sensing a current waveform of a drive motor of the blood pump;

sensing an input voltage waveform to the drive motor;

sensing a rotational frequency waveform of the drive motor; and

controlling operation of the blood pump in response to the sensing steps.

12. The method as set forth in claim 11, firher including:

calculating a motor input power;

calculating a heart rate;

calculating a pump flow rate;

calculating a pump pressure differential; and

,

calculating a required pump flow based on current physiological conditions.

13. The method as set forth in claim 12, further including:

analyzing a pump performance to verify that the pump is operating within predetermined conditions.

14. The method as set forth in claim 12, wherein the step of calculating the motor input power uses the equation:

15. The method as set forth in claim 14, wherein the step of calculating the heart rate includes analyzing one of the current waveform, input power, rotational frequency, pressure differential and pump flow waveform for a fundamental frequency.

16. The method as set forth in claim 12, wherein the step of calculating the pump pressure differential includes using one of the equation:

P_norm=ψ

(Q_norm)

and a look up table, where P_norm=P/σ

*ω

², Q_norm=Q/ω

, and ω

is the pump rotational speed, σ

is the blood density.

17. The method as set forth in claim 12, wherein the step of calculating the required pump flow includes one of the equations:

Q_target=C₁*HR+C₂; and

, Q_target=f(M);

where Q_target is the desired flow rate, C₁ and C₂ are constants determined by patient heart condition and size, M=HR/P where P is the pressure and HR is the heart rate.

18. The method as set forth in claim 12, wherein the step of calculating the required pump flow includes tracking the heart rate and basing the flow rate on the heart rate.

19. The method as set forth in claim 13, wherein the predetermined conditions include:

a minimum flow rate;

a maximum flow rate;

a minimum pulsatility;

a minimum pump rotational speed; and

,

a maximum pump rotational speed.

20. The method as set forth in claim 12, further including reverting to a pre-selected default pump rotational speed in the event of a controller failure.

21. The method as set forth in claim 12, further including reverting to a pre-selected default motor input power in the event of a controller failure.

22. The method as set forth in claim 12, further including reverting to a pre-selected default PWM duty cycle in the event of a controller failure.

23. The method as set forth in claim 19 wherein the safety conditions include:

absolute minimum flow rate, and

relative minimum flow rate.

24. The method as set forth in claim 23 comprising the further step of calculating the relative minimum flow rate as

Q_{rel min}=A*(ω

−

ω

₀)ⁿ.

25. The method as set in claim 23, further including reverting to a pre-selected default power level decrease in response to detecting ventricular suction.

26. The method as set forth in claim 12, wherein the step of calculating the pump flow includes using one of the equation:

Q=φ

(S/ω

²)

and a look up table, where S=V*I, S is average electrical power, V is motor driven bus voltage, I is motor average current within a certain time interval, and (o is the pump rotational speed.