Implantable centrifugal blood pump with hybrid magnetic bearings

Abstract

A pump for pumping sensitive fluids, such as blood, has no mechanical contact between the impeller and any other structure.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is a divisional of U.S. patent application Ser. No. 11 / 925,294, filed on Oct. 26, 2007, which application is a national phase entry under 35 U.S.C. §371 of International Application No. PCT / US99 / 08870 filed Apr. 22, 1999, entitled “Implantable Centrifugal Blood Pump With Hybrid Magnetic Bearings,” which claims priority from abandoned U.S. patent application Ser. No. 09 / 064,352, filed Apr. 22, 1998, entitled “Implantable Centrifugal Blood Pump With Hybrid Magnetic Bearings,” which was a continuation-in-part of U.S. patent application Ser. No. 08 / 850,598, filed May 2, 1997, entitled “Hybrid Magnetically Suspended and Rotated Centrifugal Pumping Apparatus and Method,” now U.S. Pat. No. 6,074,180, which claims priority from U.S. Provisional Patent Application No. 60 / 016,856, filed May 3, 1996, entitled “Hybrid Magnetically Suspended and Rotated Centrifugal Pumping Apparatus and Method,” all of which patents and applica...

AI Technical Summary

Benefits of technology

[0011]Systems and methods of this disclosure include a pumping apparatus with a magnetically suspended impeller that is suitable for pumping blood and other sensitive fluids, by handling the fluid in a gentle manner with very low heating of the fluid. The systems and methods include a motor for a magnetically levitated pump impeller having a flux gap on one or both sides of the impeller that generates low attractive force between the rotor and stator relative to other systems. The systems and methods include a pumping apparatus of relatively compact size to allow implantation in the human body as either a heart assist device or as a total heart replacement. The systems and methods include a pump apparatus and system with parameters available for measurement that are inherently available without adding additional sensors, such as magnetic bearing current and / or motor current sensors, that can be used as an indicator of required flow and pressure when the pump is implanted in the human body, or can be used to keep the impeller controlled by the magnetic bearing. The systems and methods include a pump apparatus with a long product life which requires minimal maintenance. The systems and methods include a pump apparatus that can provide flow in either a constant manner or a flow that pulses on a periodic basis. The systems and methods include a pump apparatus which is configured to cause an acute change in direction of the fluid in one or more of the conduits while still handling the sensitive fluid in a gentle manner. The systems and methods include a blood pump in which all blood-contacting surfaces are coated with a biocompatible ceramic coating.

[0012]The above elements are realized in specific illustrated embodiments of an implantable centrifugal blood pump with hybrid magnetic bearings. The pump comprises a generally cylindrical pump housing, a generally cylindrical impeller disposed within the pump housing, a magnetic bearing system for supporting and stabilizing the impeller in five degrees of freedom, and a conformally shaped motor for rotating the impeller in the remaining degree of freedom, with no mechanical contact between the impeller and any other structure. The pump thus reduces damage to the fluid from the pump and damage to the pump from the fluid. The pump impeller, housing, and other components are also configured such that flow patterns are as smooth and laminar as possible, and eddies, flow separation, and re-circulation are reduced.

[0013]The magnetic bearing system and motor advantageously comprise both electromagnets and permanent magnets for stability and control of the impeller, and to reduce size, weight, and pump power consumption. The permanent and electromagnets are disposed on the pump housing and on the impeller, such that by controlling electric current through the electromagnets on the housing, the magnetically suspended impeller functions as the rotor, and the housing as the stator of a D.C. motor. A controller linked to the electromagnets allows for sensing of relative impeller position and dynamic properties without the need for additional sensors. It also allows for the adjustment of the impeller position by modification of the current flow to the electromagnets. The pump thus forms a lightweight, dependable, and compact unit suitable for short or long-term implantation as a ventricular assist device or a complete replacement heart in a human patient.

Problems solved by technology

However, pumps for pumping sensitive fluids, such as blood, introduce special design requirements.

The design problems associated with sensitive fluids, including blood, generally relate to problems caused by contact of the fluid with mechanical parts and other substances present in the pump.

For example, it is well known that rotating shaft seals are notoriously susceptible to wear, failure, and even attack by some fluids.

Many types of pumps may also increase mechanical working of the fluid and precipitate detrimental processes such as chemical reactions or blood clotting.

Thus, rolling element bearings are generally not practical for blood pumps.

However, such pumps known in the art present several drawbacks.

First, an external motor with its own means of bearing support (ball bearings) is still required to rotate the impeller.

Though the motor is sealed from contact with blood and other bodily fluids, and is magnetically coupled to the suspended impeller, it still employs bearings which produce heat and pose the potential of failure.

Naturally, such pumps tend to be bulky in part because of the size of the electric motor.

These pumps are frequently unsuitable for implantation in a human patient because of size, weight, power consumption, and durability problems.

This approach also leaves certain problems unsolved.

These problems are well known by designers of electromechanical devices, where significant steps are normally taken to reduce the dependency of device performance on homogeneous magnets.

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