A new control method that estimates the backflow in a centrifugal pump

The rotary blood pump will be widely used in the near future as an implanta ble left ventricular assist device (LVAD). However, one obstacle for the ce ntrifugal pump is a control method that can maintain an optimum flow rate i n a physiological condition. Thus, the object of this study is to develop t his optimum control system for the centrifugal pump. If the heart function and pump efficiency are stable, the ratio of the systole current to the the diastole current (S/D) will be a fixed value. However, if the heart functi on and pump efficiency are unstable, S/D will not be a fixed value. This co ntrol system was investigated with a calf that was subjected to an ex vivo LVAD study. The LVAD was a Gyro C1E3 centrifugal pump. The pump flow rate w as changed to 1.5, 3.5, 5.2, and 6.2 L/min. According to the changes of the pump flow rates, the S/D values were 1.01 +/- 0.01, 1.06 +/- 0.05, 1.03 +/ - 0.01, and 1.03 +/- 0.01, respectively. There was no statistical differenc e among the 3 groups. In a separate experiment, the backflow condition S/D was 1.88 +/- 0.6, and the normal condition S/D was 1.35 +/- 0.5. There was a statistical difference between the 2 groups. The results of this study su ggest that S/D is not influenced by the pump flow rate, However, the S/D wa s changed when the pump was in a backflow condition. This method will be us eful in controlling a centrifugal pump requiring only electrical current in formation.