A Concept for Direct Control of Rotary Blood Pump Speed by Inlet Pressure

Heart failure remains a major health problem for the world. Heart transplantation is the most effective treatment for end stage heart failure. A major problem with heart transplantation is finding adequate numbers of appropriate donors. The lack of donor numbers in the world creates a significant clinical need for blood pumping devices. The ability of ventricular assist devices to relieve the consequences of less than terminal heart failure further creates a need for assist therapy. Current new ventricular assist devices are built around continuous flow technology. These nonpulsatile assist devices have had major clinical success in relieving symptoms and increasing patient survival. However they have a control issue as opposed the first generation pulsatile Ventricular Assist Devices (VADs) in that their output is sensitive to pressure difference, not primarily to inlet pressure. We have developed a rotodynamic blood pump speed management concept that results in a pump that responds to inlet pressure in a Starling law-like manner without active electronic controls or pressure sensors. The long term goal of this project is to develop a VAD system which responds as the natural human heart does. The pump speed is controlled by an adjunct electromechanical inlet conduit. The inlet conduit has 2 integrated cylinders. The inner cylinder is the blood flow pathway, and is flexible in order to expand/collapse in response to inlet blood pressure. The outer cylinder is used as the coil of a tank circuit. There is also a ferrofluid reservoir which is connected to the space between the 2 cylinders. The majority of ferrofluid is in the reservoir when inlet pressure is high, but ferrofluid flows into the core of the coil when inlet pressure is low. The inductance of the coil varies in response to the volume of the ferrofluid within the core. Therefore the natural frequency of the tank circuit varies and the impedance of the tank circuit changes. The control circuit is connected in series with the motor leads. Thus the voltag