Physiological control of blood pumps without implantable sensors

Abstract

Implantable flow and pressure sensors used to control implantable and extracorporeal blood pumps are unreliable in the long term. It is desirable to develop methods for physiological control of blood pumps that depend only on readily available measurements of the pump characteristics, such as measurements of pump current, voltage and speed. In this paper, we propose a model-based method for estimating pressure difference, AP, across the rotary blood pump. The proposed estimator requires differentiation of the measurements, which is carried out after Savitzky-Golay filtering of the measurement data. The Savitzky-Golay filtering is used in conjunction with the extended Kalman filter to generate, in real time, estimates of AP, which are used in the previously proposed control system for physiological control of blood pumps. The performance of the overall system for the broad range of physical activities and pathological scenarios is tested with a luinped parameter inodel of the circulatory system assisted by a left ventricular a5sist device. Simulations show that there is virtually 110 performance degradat,ion of the estimator-controller system compared to t,hc case when AP is directly measured.