AN AUTOMATIC FLOW CONTROLLER FOR A CENTRIFUGAL BLOOD PUMP

To regulate the perfusion now rate of a centrifugal blood pump, a micr ocomputer controller was developed. The computer monitored the flow ra te of the pump with an electromagnetic flowmeter or an ultrasonic puls e Doppler flowmeter, rotational speed of the pump, aortic pressure, an d the amount of blood in a reservoir. A discrete integral controller w ith a control interval of 1 s was adopted for the controller. For the safety of the control system, we added functions for detecting a clamp on the tubing, a dislocation of the flow sensor, or an inverse direct ion of the flow sensor. During a standby period, the computer calculat ed the rotational speed from aortic pressure to minimize the forward o r the backward flow at the start of the pump perfusion. The automatic flow controller was used on 5 patients during cardiac operations and m aintained the flow rate within +/-6% of the set point.