Development of a control algorithm for a rotary blood pump: prediction of recovery from cardiac failure

Under extracorporeal membrane oxygenator (ECMO) support, it is difficult to predict recovery of cardiac function. The authors examined the rotary blood pump function curve and developed a new index of dynamic vascular impedance (DVI) for controlling the ECMO system. The cases of nine patients assisted by ECMO after cardiac surgery were analyzed. The index of DVI was calculated from the pump flow and the pressure difference (delta pressure) between the inlet and outlet of the pump. Seven patients were weaned from support. In the patients with recovery of cardiac function, the index of DVI was high and the delta pressure converged on the specific value. Analysis of the rotary blood pump function curve during ECMO support reflects the pump characteristics and provides data for the management of pump speed. The index of DVI can be used to predict the timing for weaning patients from ECMO support. The authors are developing an automatic control system that uses the index of DVI.