An adaptive aortic pressure observer for the Penn State electric ventricular assist device

Abstract

This paper addresses the development of an aortic pressure observer for the Penn State Electric Ventricular Assist Device (EVAD). The observer estimates the aortic blood pressure by measuring the voltage of the electric motor and the pusher plate position. The estimated pressure is fedback to the EVAD's blood flow controller, which adjusts the beat rate of the device to accommodate the varying demand of cardiac output. The gains of the observer are deterministically optimized such that the optimal values are independent of the (often unknown) system state initial conditions. To improve the performance of the pressure observer an adaptation scheme is developed. In this scheme the initial pressure estimate of the succeeding systolic cycle is adjusted when the pressure does not match its corresponding second estimated value. In vitro test runs of the developed observer show that is is robust to parameter variations, and the error of the resultant estimated pressure is less than 5%.