A COMPUTERIZED CONTROL-SYSTEM FOR CARDIOPULMONARY BYPASS

A pump control system using a microcomputer for cardiopulmonary bypass has been developed. The parameters monitored by the computer are central venous pressure, aortic pressure, blood volume in a reservoir, and collapsing of a small vinyl bag in a venous withdrawal tube. Both pumps in the arterial infusion and the venous withdrawal lines are automatically controlled through an interface unit throughout cardiopulmonary bypass. The system regulates central venous pressure with a proportional-integral control algorithm to maintain intravascular volume constant. A screening algorithm is devised to remove artifacts introduced to the pressure measurement. During the weaning period, a perfusionist can select either the central venous pressure control or a reservoir blood volume control. Computerized pump perfusion was applied on 15 children during cardiac operations. Perfusion flow and central venous pressure were controlled satisfactorily with stable operation. Compared with conventional manually controlled pump perfusion, no significant difference was noted in mean aortic pressure, central venous pressure, net fluid balance, total urination, blood chemistry, and urinalysis. This system is useful and is expected to improve the safety of pump perfusion.