Axial flow rotary blood pumps have been successfully introduced clinically to provide prolonged mechanical circulatory support, but these devices do not provide load-responsive mechanisms for adjusting pump performance to match venous return and changes in physiologic demand. Most of these devices operate at an adjustable fixed speed, and they have the potential to generate excessive suction pressures that can have serious consequences for the patient. A new device is proposed to monitor the inlet pressure in rotary blood pumps to improve their safety and efficacy. Conventional strain gauge transducers are subject to drift and have stability issues that make them unsuitable for long-term implantation. The proposed device employs a comparatively large displacement diaphragm in an elliptical cross-section conduit whose excursion is sensed by a planar transformer system operating at radio frequencies. There is no direct physical contact with the moving diaphragm. Unlike control algorithms that infer hemodynamic conditions at the pump inflow from parameters such as the motor current, the proposed device will enable the development of control systems that dynamically adjust pump speed to avoid excessive suction pressures and optimize pump blood flow. In essence this will make these devices operate similar to Starling's law devices in which the available blood at the inflow determines the pump output. In Phase I we will design the new inlet pressure sensor and evaluate its static and dynamic performance to evaluate its applicability for controlling a rotary blood pump. A demonstration of feasibility will consist of showing that the device accurately measures inlet conduit pressure and that it has a response time that will permit automatic speed control on a beat-by-beat or short-term averaged basis.
The proposed device is an electromechanical component designed to measure pressure in the inlet conduit of a blood rotary pump in order to prevent excessive suction pressures. The device output will be referenced to intrathoracic pressure. It works by monitoring the deflection of an elliptical cross section elastomeric conduit in response to changes in its internal pressure. This deflection is measured using a planar transformer system operating at radio frequencies transparent to body tissues. No direct electrical or physical connection to the moving wall of the conduit is required. The output of the device will be usable as a control signal that may be employed to adjust the pump speed to prevent the development of excessive negative pressures in the pump inflow conduit, left ventricle, and upstream vasculature. ? ? ?
