ESTABLISHMENT OF FLOW ESTIMATION FOR AN IMPLANTABLE CENTRIFUGAL BLOODPUMP

A less invasive and non thrombogenic flow estimation of an implantable centrifugal blood pump (ICBP) has been developed, which was derived f rom electric power consumption, the rotating speed of a motor, and blo od viscosity presumed by hematocrit and body temperature. The power co nsumption and the rotating speed of the motor were measured by a wattm eter every 0.2 sec. Accuracy and stability of the estimated flow (EF) were investigated during in vitro and in vivo experiments. The EF was compared with a measured flow rate (MF) monitored by an electromagneti c flowmeter. During in vitro experiments, the EF and MF were measured at 79 operating points. The ICBP was driven in a closed mock loop fill ed with goat blood with hematocrit values of 21.5, 28, 34, and 42%. Du ring in vivo experiments, the ICBP was implanted in the chest cavity o f a goat and driven for 40 days with continuous estimation of the bypa ss flow rate. Blood was taken to determine hematocrit value several ti mes a week. The temperature of the pleura away from the ICBP was measu red every 15 min. A linear correlation between the EF and MF was obser ved, and the correlation coefficient between the EF and MF was 0.99 du ring in vitro examinations. An averaged error of the EF was 0.5 L/min, with the MF ranging from 2.3 to 8.1 L/min during in vivo experiments. In conclusion, flow estimation was established with good stability an d accuracy in both in vitro and in vivo experiments.