Automatic modules for extracorporeal circulation control.

Abstract

Maintenance of a constant level in the oxygenator during surgical extracorporeal circulation (ECC) is of paramount importance. We propose a device able to regulate the pump speed accordingly to the level in the oxygenator, and an automatic clamp to control venous return from the patient. The level regulator permits pump speed control and also stops the pump when a prefixed low level is reached (during ECC). Linearization of the level sensor has been made in order to optimize the PI regulator. Simulation results are presented and the regulator is evaluated in a clinical environment. The automatic clamp provides a good solution for reproducible and easy transitions in venous return. When coupled with the level regulator, the pump speed will increase automatically from zero to the correct equilibrium speed, with variable duration (from 30 seconds to 5 minutes) chosen by the operator. The same technique is used for stopping the ECC. These two devices are, in fact, modules, making up part of an evolutive device for ECC automation. The modules can exchange data with a supervising microcomputer.