Noninvasive Average Flow Estimation for an Implantable Rotary Blood Pump: A New Algorithm Incorporating the Role of Blood Viscosity

Abstract: The effect of blood hematocrit (HCT) on a non-invasive flow estimation algorithm was examined in a cen-trifugal implantable rotary blood pump (iRBP) used for ventricular assistance. An average flow estimator, based on three parameters, input electrical power, pump speed, and HCT, was developed. Data were collected in a mock loop under steady flow conditions for a variety of pump operat-ing points and for various HCT levels. Analysis was per-formed using three-dimensional polynomial surfaces to fit the collected data for each different HCT level. The poly-nomial coefficients of the surfaces were then analyzed as a function of HCT. Linear correlations between estimated and measured pump flow over a flow range from 1.0 to 7.5 L/min resulted in a slope of 1.024 L/min (R2 = 0.9805). Early patient data tested against the estimator have show