Basic research concerning control method of bi-ventricular assist with nonpulsatile flow pump

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Mechanical circulatory support is becoming an important therapeutic option both as a bridge to heart transplantation and for permanent use. Several types of nonpulsatile flow pumps are being developed for long-term circulatory support, having the advantage of compactness and low cost as compared to pulsatile pumps. The pathophysioloey of long-term nonpulsatile ventricular support, however, is not yet clearly understoocL The control method of continuous flow pumps especially in bi-ventncular assist with nonpulsatile flow pump has not been established. We have attempted basic research concerning control method of bi-ventricular assist with nonpulsatile flow pump. The hemodynamics under ventricular assist with continuous flow pump is quite particular including reduction in arterial pulsatility. We firstly evaluated physiological changes due to ventricular assist with the nonpusatile flow pump. We found that the diminution of systemic yasoconstrictive function and progression of cardiac parasympathetic nervous activity. However no obvious changes were not observed in central nervous system, baroreceptor function, hormonal factors, and pulmonary system. The control tactics for the optimized operation of a continuous-flow VAD using the driving motor current has been proposed. The good correlation between the motor current and flow rate allowed us to detect adverse pumping condition such as inflow cannulae sucking and even to estimate assist status by the VAD. The control of the continuous-flow pumps for biventricular support has also been examined. Maintenance of the circulatory balance between the left and the right pump was attempted by adjusting the hydrodynamic characteristics of the rignt pump. Use of additional resistance of the outflow tubing could successfully reduce the flow rate fluctuation caused by the change in circulatory resistance. The flow rate of the right pump was stabilized by this device.