Surgery – Devices transferring fluids from within one area of body to... – With flow control means
Reexamination Certificate
1999-01-19
2001-04-17
Nguyen, Anhtuan T. (Department: 3734)
Surgery
Devices transferring fluids from within one area of body to...
With flow control means
C604S151000, C623S003100, C415S900000
Reexamination Certificate
active
06217541
ABSTRACT:
FIELD OF THE INVENTION
The present invention concerns a novel blood pump, and more particularly, a blood pump that may be suitable as a ventricular assist device.
BACKGROUND OF THE INVENTION
Thousands of patients suffer cardiogenic shock following heart attacks or open heart surgery. These patients may benefit from mechanical circulatory support with a minimum output of 3 liters per minute. Many patients need temporary cardiac support during emergency transportation in an ambulance.
The need for a minimally invasive mechanical heart assist device has long been recognized. An ideal device would (1) have a cross-section of 12 French or less so that it could be adapted for insertion via a peripheral artery, such as the femoral artery (2) function intra-arterially and be inserted by a cardiologist without support from a surgeon and, (3) be capable of providing at least 3 liters per minute of flow at systemic pressures without a contribution from the native left ventricle. The intra-aortic balloon pump (IABP) has been used for years and is the industry standard because it is easy to insert and does not require surgery. It is readily inserted into the femoral artery by the cardiologist, but it has limited pumping capacity and can only be used for a patient who has some residual cardiac function. The flow of the IABP is limited to approximately 1.5 liters per minute to 2.0 liters per minute and is dependent upon synchronization with a left ventricle which must have some residual function.
There have been efforts to provide a temporary, minimally invasive pump for patients which require more cardiac output than can be provided by an IABP. The Hemopump is an axial flow blood pump which meets the criteria for blood flow (approximately 5 liters per minute) but it is too large (14 to 22 French) for easy insertion by a cardiologist. Although smaller versions of the Hemopump could be built, physics limits the flow because as the pump becomes smaller, the inlet area decreases. Losses in the pump increase in a rapid, non-linear manner as the inlet area decreases. To compensate for these rapidly increasing losses, the rotor speed must be increased exponentially. Although adequate flow may be achieved, hemolysis increases to unacceptable levels.
Thus the engineer faces theoretical and technical difficulties to make a traditional propeller pump or centrifugal pump with the diameter less than 4.0 mm and a flow of at least 3 liters per minute. One way to circumvent the physical limitations imposed by a decreasing inlet area is to make the pump expandable. In this way, inlet losses and shaft speed can be minimized since large areas can be achieved after the pump is inserted. Cable driven axial flow blood pumps have been described which use a hinged propeller that deploys after insertion into the arterial system. However, hemolysis has limited the adaptation of this concept as a clinical device. Other concepts for pumps that expand or deploy after insertion have been proposed. However, these miniature expandable pumps are challenging to manufacture and reliable mechanisms may be difficult to achieve.
The Hemopump and expandable pumps have constrained pump design by dictating that the inlet area must be located in a plane perpendicular to the axis of rotation. Consequently, an increase in the inlet area will also increase the diameter of the pump.
It is, therefore, an object of the present invention to achieve the benefits of a large inlet area without the necessity for enlarging the inlet diameter or making the blood pump expandable.
It is another object of the present invention to provide a blood pump which provides low inlet and outlet losses while maintaining a small diameter and without the need for an expandable mechanism.
A still further object of the present invention is to provide a blood pump that obviates the problems discussed above that are concomitant with prior art blood pumps.
A further object of the invention is to provide a blood pump having a 3 liter per minute or greater flow and having a diameter that is small enough to permit percutaneous insertion of the pump into a patient's blood vessel.
Another object of the invention is to provide a blood pump that is relatively simple in construction and relatively easy to manufacture.
Other objects and advantages of the present invention will become apparent as the description proceeds.
SUMMARY OF THE INVENTION
Cross-flow principles have been used in cross-flow air blowers. I have discovered that cross-flow air blower principles can be used effectively for a blood pump head.
In accordance with the present invention, a blood pump is provided which comprises a pump head having a cross-flow configuration. As used herein, a “cross-flow configuration” utilizes a housing in which an inlet is defined on a side of the housing and an outlet is defined on a side of the housing, with the flow from the inlet to the outlet being around and/or across the rotational axis of an impeller within the housing. The flow between the inlet and the outlet is preferably but not necessarily in a direction that is generally perpendicular to the rotational axis of the impeller.
In the illustrative embodiment of the present invention, the blood pump head has an elongated housing portion. The housing portion defines a blood inlet port on a surface thereof and a blood outlet port on a surface thereof. An impeller is located within the housing portion for providing cross-flow of the blood from the inlet port to the outlet port. A motor is provided for driving the cross-flow pump head.
In the illustrative embodiment, the blood inlet port and the blood outlet port have rectangular configurations. The blood inlet port is larger than the blood outlet port and the blood inlet port and blood outlet ports are defined on opposite surfaces.
In the illustrative embodiment, the housing portion is generally cylindrical and the blood inlet port defines an arc between 80° and 180° and the blood outlet port defines an arc less than 80°. The impeller has an axial length that is at least 2 times its diameter and the impeller has blades which rotate tangentially to the cylindrical planes that define the inlet and outlet ports.
In one embodiment, the impeller comprises a squirrel cage configuration. The impeller has a plurality of blades having a forward angle from 0° to 80° and a pair of axially spaced shrouds. The axial ends of the blades are attached to the axially spaced shrouds.
In that embodiment, the impeller has coaxial shafts extending outwardly from the shrouds. Bearings are provided for supporting the coaxial shafts within the housing. A wiper comprising either a ridge or a groove on an outside surface of a shroud is provided to aid in moving the blood around a shaft, to minimize the likelihood of thrombus deposition.
In another embodiment, instead of axially spaced shrouds, one shroud is located intermediate of the blades. In a further embodiment, one shroud is located only on one end of the blades. In one embodiment, the impeller shaft is magnetically coupled to the motor. In another embodiment, the motor is coupled to the impeller shaft via a flexible shaft and the motor is an air motor.
In one embodiment, the blood pump has an outer dimension that is small enough to permit percutaneous insertion of the pump into a patient's blood vessel. A collapsible polymeric outflow tube is provided and is coupled to the blood flow outlet of the pump and is adapted for directing the blood from the left ventricle of the patient to the aorta through the aortic valve.
In accordance with the present invention, a method is provided for pumping blood. The method comprises the steps of providing a cross-flow pump head having an elongated housing portion defining a blood inlet port on a surface thereof and a blood outlet port on a surface thereof; providing an impeller within said housing portion for providing cross-flow of the blood from the inlet port to the outlet port; and driving the cross-flow pump head with a motor to rotate the impeller and accelerate the blood from the inlet
Gerstman George H.
Kriton Medical, Inc.
Nguyen Anhtuan T.
Shaw Seyfarth
Thissell Jeremy
LandOfFree
Blood pump using cross-flow principles does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Blood pump using cross-flow principles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Blood pump using cross-flow principles will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2439663