Flow controlled blood pump system

• US 20030139643A1
• Filed: 03/03/2003
• Published: 07/24/2003
• Est. Priority Date: 09/24/1997
• Status: Active Grant

• Current Assignee: Cleveland Clinic Foundation
• Original Assignee: Cleveland Clinic Foundation
• Inventors: Smith, William A., Golding, Leonard A.R.
• Granted Patent: US 7,435,059 B2
• Time in Patent Office: Days
• US Class Current: 600/16
• CPC Class Codes: A61M 2205/3334 Measuring or controlling the flow rate
• CPC Class Codes: A61M 2205/8243 by induction
• 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 60/419 the force acting on the blood contacting member being permanent magnetic, e.g. from a rotating magnetic coupling between driving and driven magnets
• 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 60/546 of blood flow, e.g. by adapting rotor speed
• CPC Class Codes: A61M 60/806 Vanes or blades
• CPC Class Codes: A61M 60/873 specially adapted for wireless or transcutaneous energy transfer [TET], e.g. inductive charging
• CPC Class Codes: A61M 60/898 the blood pump being a membrane blood pump and the membrane acting as inlet valve

Abstract

A system for pumping blood to assist or assume the cardiac function of a patient is characterized by a blood pump that exhibits a steep performance curve such that only small changes in pump flow occur for large changes in differential pressure across the pump. The pump therefore exhibits flow-limiting characteristics to protect the physiological system against harmful flow rates or pressures. Pump flow may also be limited by controlling the current provided to a driver from a power supply or by suitable restrictions within or external to the pump housing.

Claims

1. A rotodynamic pump comprising:

a) a housing defining a chamber and an inlet and outlet in fluid communication with the chamber;

b) an impeller disposed within the chamber for urging fluid from inlet to outlet, the impeller being configured to provide a pressure differential/flow performance curve slope such that a flow of fluid through the pump is maintained within defined limits over a wide applied pressure differential across the pump.

2. The pump according to claim 1, wherein the performance curve of the pump exhibits a change in flow of no more than 1 liter-per-minute for a change in pressure of 50 mm-Hg between the pump inlet and pump outlet.

3. The pump according to claim 1, wherein the performance curve is linear thru a nominal operating set point of the pump.

4. The pump according to claim 1, wherein the impeller comprises a plurality of main blades and a plurality of splitter blades, shorter in length that the main blades, disposed between the main blades.

5. The pump according to claim 1, wherein the impeller comprises a plurality of flat blades.

6. The pump according to claim 1, wherein the direction of flow within the blades is at an acute angle with respect to the axis of rotation.

7. The pump according to claim 1, wherein the pump further comprises an axial extension having a conical tip and wherein the impeller comprises a plurality of blades having an angled inner edge configured to accommodate the conical tip.

8. A system for pumping blood comprising:

a) a rotodynamic pump including;

i) a housing defining a chamber and an inlet and outlet in fluid communication with the chamber; and

ii) an impeller disposed within the chamber for urging fluid from inlet to outlet;

iii) the pump having a performance curve at a nominal operating speed of the pump, the performance curve relating changes in the pressure differential across the pump to changes in flow through the pump;

b) a driver for imparting rotational motion to the impeller;

c) a power supply for supplying power to the driver;

d) a regulator for regulating the power supplied from the power supply to the driver;

e) flow limiting means for maintaining the flow through the pump within predefined limits throughout a wide range of pressure differentials across the pump.

9. The pump according to claim 8, wherein the performance curve of the pump exhibits a change in flow of no more than 1 liter-per-minute for a change in pressure of 50 mm-Hg between the pump inlet and pump outlet.

10. The pumping system according to claim 8, further comprising a means to vary the nominal set point of the pump output.

11. The pumping system according to claim 8, wherein the flow limiting means comprises an impeller configured to provide a performance curve slope, pressure differential/flow, with a valve such that a flow of fluid through the pump is maintained within defined limits over a wide applied pressure differential.

12. The pumping system according to claim 11, wherein said impeller includes a plurality of main blades and a plurality of splitter blades, shorter in length that the main blades, disposed between the main blades.

13. The pumping system defined in claim 10, wherein the impeller comprises a plurality of flat blades.

14. The pumping system according to claim 10, wherein the flow limiting means comprises a flow resistor in communication with the outlet of the pump.

15. The pumping system according to claim 14, wherein the flow resistor has a resistance value varying with flow rate.

16. The pumping system according to claim 10, the means to vary the nominal set point comprises a digital computer executing an algorithm that controls the set point according to measurement of pump input rpm, motor current, motor power, or a combination thereof.

17. A fluid pumping system according to claim 10, wherein the flow limiting means comprises a switch cooperating with a variable cross-section conduit in fluid communication with the outlet of the pump and operating to generate a signal to the energy regulator.

18. A fluid pumping system according to claim 17, wherein flow-limiting means is a flow resistor on pump inlet.

19. The blood pumping system according to claim 10, wherein the flow limiting means comprises a power regulator for limiting the power delivered to the pump driver, such that the pressure differential producing capability falls a flow increases, and rises as flow decreases.

20. The blood pumping system according to claim 19, wherein the power limiting means comprises an electrical current regulator.

21. The blood pumping system according to claim 20, further incorporating rotational speed regulation into the pump driver power regulation.

22. A method of providing a blood pumping system for the human body comprising the steps of:

a) providing a rotodynamic pump for assisting or assuming the cardiac function of the body;

b) configuring the pump to provide a performance curve with a slope, pressure differential/flow such that a flow of fluid through the pump is maintained within twenty percent (20%) or less of a defined baseline over a wide applied pressure differential of fifty percent (50%) or more across the pump;

c) wherein control of the power delivered to the pump driver according to feedback of a combination of driver electrical current and rpm forms a component of the means for providing an appropriate pump performance curve slope.