Magnetically suspended fluid pump and control system

• US 6,293,901 B1
• Filed: 05/07/1999
• Issued: 09/25/2001
• Est. Priority Date: 11/26/1997
• Status: Expired due to Fees

• Current Assignee: Vascor, Inc.
• Original Assignee: Vascor, Inc.
• Inventors: Prem, Edward K.
• Primary Examiner(s): Schaetzle, Kennedy
• Application Number:
  US09/307,116
• Time in Patent Office: 872 Days
• Field of Search: 623/3.13, 623/3.14, 623/3.28, 623/3.1, 600/16, 600/17, 600/438, 600/439, 600/459, 600/507, 600/508, 600/587
• US Class Current: 600/17
• CPC Class Codes: A61M 2205/33 Controlling, regulating or measuring
• CPC Class Codes: A61M 2205/3303 Using a biosensor
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• 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 60/232 Centrifugal pumps
• CPC Class Codes: A61M 60/242 with the outlet substantially perpendicular to the axis of rotation
• CPC Class Codes: A61M 60/422 the force acting on the blood contacting member being electromagnetic, e.g. using canned motor pumps
• CPC Class Codes: A61M 60/523 using blood flow data, e.g. from blood flow transducers
• CPC Class Codes: A61M 60/546 of blood flow, e.g. by adapting rotor speed
• CPC Class Codes: A61M 60/814 Volutes
• CPC Class Codes: A61M 60/822 specially adapted for being actively controlled
• CPC Class Codes: A61M 60/824 Hydrodynamic or fluid film bearings
• CPC Class Codes: A61M 60/833 Occluders for preventing backflow
• CPC Class Codes: A61M 60/894 Passive valves, i.e. valves actuated by the blood
• CPC Class Codes: F04D 13/0646 the hollow pump or motor shaft being the conduit for the working fluid
• CPC Class Codes: F04D 29/048 magnetic; electromagnetic
• CPC Class Codes: F16C 2316/18 Pumps for pumping blood
• CPC Class Codes: F16C 2360/44 Centrifugal pumps
• CPC Class Codes: F16C 32/0444 Details of devices to control the actuation of the electromagnets
• CPC Class Codes: F16C 32/047 : Details of housings; Mounting of active magnetic bearings

Abstract

A blood pump for assisting a heart is provided by a stator and a rotor. The rotor is magnetically supported creating a suspension gap between the stator and the rotor. The rotor can be supported axially by a Lorentz force bearing and can be magnetically rotated. The stator can have a volute pump chamber and the rotor can have an impeller portion for pumping blood. The rotor can have a center bore as a primary blood flowpath. The suspension gap can be a first retrograde blood flowpath. An axial gap between the impeller and the volute housing can be a second retrograde blood flowpath. The blood pump can also have an axial position controller. The axial position controller can cause the axial bearing to adjust the position of the rotor. The axial position of the rotor. The axial position of the magnetic suspension components can be adjusted to compensate for changes in the magnetic fields of the magnetic suspension components. The blood pump can also have a flow rate controller. The flow rate controller can have a member for measuring a dimension of a heart ventricle to control the flow rate to avoid overly distending or contracting the ventricle. A method for operating the flow rate controller to create a pulsatile flow rate is also provided. A flow sensor can be used to avoid excessively low or reverse blood flow through the pump when a pulsatile flow rate is provided.

Claims

1. A blood pump apparatus implantable in a patient comprising:

a. a stator member;

b. a rotor member disposed adjacent said stator member for rotation relative thereto;

c. a magnetic suspension having a stator magnet portion carried by said stator member and a rotor magnet portion carried by said rotor member, said stator and rotor magnet portions cooperating to magnetically support said rotor member radially such that an annular magnetic suspension gap is created between said rotor member and said stator member;

d. at least one of said stator magnet portion and said rotor magnet portion movable in an axial direction with respect to the member which carries said magnet portion;

e. an axial position actuator engaged with said movable one of said stator magnet portion and said rotor magnet portion, said axial position actuator controllable to move said movable one of said stator magnet portion and said rotor magnet portion relative to the member which carries said magnet portion to adjust axial alignment between said stator and rotor magnet portions; and

f. a magnetic drive having a stator motor portion carried by said stator member and a rotor motor portion carried by said rotor member, said stator motor portion and said rotor motor portion cooperating to magnetically rotate said rotor member relative to said stator member to pump blood.

2. The blood pump apparatus of claim 1 further comprising:

a. a sleeve member slidably disposed in said stator member and having a flange portion;

b. said stator magnet portion being attached to said sleeve; and

c. said axial position actuator engaged with said flange portion, said axial position actuator controllably moving said flange member axially relative to said stator member to control an axial position of said sleeve member and said stator magnet portion attached thereto.

3. The blood pump apparatus of claim 2 further comprising an axial position sensor detecting an axial position of said sleeve member.

4. The blood pump apparatus of claim 2 further comprising:

a. said axial position actuator being an electrically controlled motor having an output shaft;

b. a screw member rotatably disposed in said stator member, said screw member having a first end and a threaded second end, said first end engaged with said output shaft and restrained against axial movement in said stator member; and

c. said flange portion having a threaded opening in which said threaded second end is engaged such that rotation of said screw member axially moves said flange portion and thus said sleeve member relative to said stator member thereby adjusting an axial position of said stator magnet portion.

5. The blood pump apparatus of claim 3 further comprising an axial position sensor for detecting an axial position of said sleeve member.

6. The blood pump apparatus of claim 5 wherein said axial position sensor further comprises:

a. a first sensor portion carried by said sleeve member; and

b. a second sensor portion carried by said stator member, said first and second sensor portions positioned such that said second sensor portion detects changes in an axial position of said first sensor portion relative to said second sensor portion.

7. The blood pump apparatus of claim 6 further comprising:

a. said first sensor portion being a magnetic member attached to said flange portion; and

b. said second sensor portion being a pair of sensors attached to said stator member, respective ones of said pair of sensors positioned on opposite axial sides of said magnetic member such that axial displacement of said magnetic member between said pair of sensors is detected.

8. The blood pump apparatus of claim 1 wherein said stator magnet portion and said rotor magnet portion further comprise first and second permanent magnet arrays, respectively, each of said first and second permanent magnet arrays comprising:

a. a plurality of adjacent permanent magnets;

b. each of said plurality of adjacent permanent magnets having a predefined polarity; and

c. said predefined polarity of each of said plurality of adjacent permanent magnets oriented to radially polarize said first and second permanent magnet arrays such that magnetic flux is directed in a radial direction between said first and second permanent magnet arrays.

9. The blood pump apparatus of claim 8 further comprising:

a. a Lorentz-force axial bearing having a stator axial bearing portion carried by said stator member and a rotor axial bearing portion carried by said rotor member, said stator axial bearing portion and said rotor axial bearing portion cooperating to magnetically support said rotor member axially relative to said stator member;

b. said stator and rotor axial bearing portions having third and fourth permanent magnet array portions, respectively, each of said third and fourth permanent magnet array portions being a plurality of adjacent permanent magnet rings, each of said plurality of adjacent permanent magnet rings having a predefined polarity orientation to radially polarize said third and fourth permanent magnet arrays such that magnetic flux is directed in a radial direction between said third and fourth permanent magnet arrays; and

c. wherein said third and fourth permanent magnet arrays are radially polarized in opposite radial directions.

10. The blood pump apparatus of claim 8 wherein said first and second permanent magnet arrays are radially polarized in opposite radial directions.

11. A blood pump apparatus implantable in a patient comprising:

a. a stator member;

b. a rotor member disposed adjacent said stator member for rotation relative thereto;

c. a magnetic suspension having a first permanent magnet array carried by said stator member and a second permanent magnet array carried by said rotor member, said first and second permanent magnet arrays cooperating to magnetically support said rotor member radially such that an annular magnetic suspension gap is created between said rotor member and said stator member;

d. each of said first and second permanent magnet arrays being a plurality of adjacent permanent magnet rings, each of said plurality of adjacent permanent magnet rings having a predefined polarity orientation to radially polarize said first and second permanent magnet arrays such that magnetic flux is directed radially between said first and second permanent magnet arrays, wherein at least one of said first and second permanent magnet arrays is made entirely from permanent magnets; and

e. a magnetic drive having a stator motor portion carried by said stator member and a rotor motor portion carried by said rotor member, said stator motor portion and said rotor motor portion cooperating to magnetically rotate said rotor member relative to said stator member to pump blood.

12. The blood pump apparatus of claim 11 further comprising:

a. said plurality of adjacent permanent magnet rings being three adjacent permanent magnet rings;

b. a first outer ring of said three adjacent rings having said predefined polarity oriented in a first direction;

c. a centrally disposed ring adjacent said first outer ring and having said predefined polarity oriented in a second direction normal to said first direction; and

d. a second outer ring adjacent said centrally disposed ring on a side thereof opposite said first outer ring, said second outer ring having said predefined polarity oriented in a third direction opposite said first direction to radially polarize said three adjacent rings such that magnetic flux through said three adjacent rings is directed radially between said first and second permanent magnet arrays.

13. The blood pump apparatus of claim 12 wherein said three adjacent rings of each of said first and second permanent magnet arrays are radially polarized in opposite radial directions.

14. The blood pump apparatus of claim 11 further comprising:

a. said plurality of adjacent permanent magnet rings being five adjacent permanent magnet rings;

b. an outer first ring of said five adjacent rings, said first ring having said predefined polarity oriented in a first direction;

c. a second ring disposed adjacent said first outer ring and having said predefined polarity oriented in a second direction normal to said first direction;

d. a third ring centrally disposed adjacent said second ring and having said predefined polarity oriented in a third direction parallel to but opposite said first direction;

e. a fourth ring adjacent said third ring on a side thereof opposite said second ring, said fourth ring having said predefined polarity oriented in a fourth direction parallel to but opposite said second direction;

f. an outer fifth ring of said five adjacent rings, said fifth ring having said predefined polarity oriented in said first direction;

g. a first magnetic flux path being established through said first, second and third adjacent rings and said first magnetic flux path directed radially between said first and second permanent magnetic arrays; and

h. a second magnetic flux path being established through said third, fourth and fifth adjacent rings and said second magnetic flux path directed radially between said first and second permanent magnetic arrays.

15. The blood pump apparatus of claim 14 wherein said first and second magnetic flux paths are radially polarized in opposite radial directions.

16. The blood pump apparatus of claim 14 wherein said first magnetic flux path of said second permanent magnet array has a radial polarity opposite a radial polarity of said first magnetic flux path of said first permanent magnet array and said second magnetic flux path of said second permanent magnet array has a radial polarity opposite a radial polarity of said second magnetic flux path of said first permanent magnet array.

17. The blood pump apparatus of claim 11 wherein said first and second permanent magnet arrays are radially polarized in opposite radial directions.

18. A blood pump apparatus implantable in a patient comprising:

a. a stator member;

b. a rotor member disposed adjacent said stator member for rotation relative thereto;

c. a magnetic suspension having a stator magnet portion carried by said stator member and a rotor magnet portion carried by said rotor member, said stator and rotor magnet portions cooperating to magnetically support said rotor member radially such that an annular magnetic suspension gap is created between said rotor member and said stator member;

d. a magnetic drive having a stator motor portion carried by said stator member and a rotor motor portion carried by said rotor member, said stator motor portion and said rotor motor portion cooperating to magnetically rotate said rotor member relative to said stator member to pump blood;

e. a flow sensor generating an output corresponding to a blood flow rate through said blood pump;

f. a flow rate controller receiving said output from said flow sensor and controlling said magnetic drive to produce a pulsatile flow rate; and

g. wherein said flow rate controller is responsive to said flow sensor output to control said magnetic drive to maintain at least a predetermined minimum blood flow rate during a low phase portion of said pulsatile flow rate.

19. The blood pump of claim 18 wherein said flow rate controller further comprises:

a. a heart measurement member attachable to a heart ventricle which is assisted by said blood pump;

b. said heart measurement member measuring at least one of distention and contraction of said ventricle; and

c. said flow rate controller utilizing said measurements of said at least one of distention and contraction to control said flow rate of said blood pump to produce said pulsatile flow rate.

20. The blood pump of claim 19 wherein said heart measurement member comprises:

a. a heart caliper having a pair of arms pivotable relative to each other;

b. each of said pair of arms having one end attachable to an outer surface of said ventricle and an opposite end connected at a pivot point; and

c. an angular measurement device measuring changes in angular position between each of said pair of arms.

21. The blood pump of claim 20 wherein said angular measurement device comprises an electronic eddy current position sensor measuring said changes in angular position between said pair of arms.

22. The blood pump of claim 19 wherein said heart measurement member comprises a pair of ultrasonic transducers positioned at generally opposing sides of said ventricle measuring a radial dimension of said ventricle based upon an elapsed time for an ultrasonic pulse to travel between said pair of transducers.

23. A blood pump apparatus implantable in a patient comprising:

a. a stator member;

b. a rotor member supported in said stator member for rotation therein and said rotor member having a rotor pump portion disposed adjacent said stator pump portion;

c. a motor engaged with said rotor member to rotate said rotor member relative to said stator member to pump blood;

d. a flow sensor generating an output corresponding to a blood flow rate through said blood pump;

e. a flow rate controller receiving said output from said flow sensor and controlling said magnetic drive to produce a pulsatile flow rate; and

f. wherein said flow rate controller is responsive to said flow sensor output to control said motor to maintain at least a predetermined minimum blood flow rate during a low phase portion of said pulsatile flow rate.

24. The blood pump of claim 23 wherein said flow rate controller further comprises:

a. a heart measurement member attachable to a heart ventricle which is assisted by said blood pump;

b. said heart measurement member measuring at least one of distention and contraction of said ventricle; and

c. said flow rate controller utilizing said measurements of said at least one of distention and contraction to control said flow rate of said blood pump to produce said pulsatile flow rate.

25. The blood pump of claim 24 wherein said heart measurement member comprises:

a. a heart caliper having a pair of arms pivotable relative to each other;

b. each of said pair of arms having one end attachable to an outer surface of said ventricle and an opposite end connected at a pivot point; and

c. an angular measurement device measuring changes in angular position between each of said pair of arms.

26. The blood pump of claim 25 wherein said angular measurement device comprises an electronic eddy current position sensor measuring said changes in angular position between said pair of arms.

27. The blood pump of claim 24 wherein said heart measurement member comprises a pair of ultrasonic transducers positioned at generally opposing sides of said ventricle measuring a radial dimension of said ventricle based upon an elapsed time for an ultrasonic pulse to travel between said pair of transducers.