CLOSED-LOOP CONTROL OF PACO2 DURING ECC

A prototype for the control of blood gases during extracorporeal circu lation (ECC) has been built. It is composed of a CDI300 continuous gas blood analyzer, a programmable gas blender and an IBM PC. The air ble nder is composed of three mass flow controllers (air, oxygen and total flow rate). The microcomputer commands these controllers in order to obtain the desired mixture of air and oxygen. The system acquires the data sent by the blood gas analyzer every 6 seconds and commands the g as blender in order to maintain the desired arterial dioxide partial p ressure (PaCO2) in the arterial line. The first experimental results o n sheep show that if blood gas parameters are stable when beginning th e closed loop control, then the desired PaCO2 value may be obtained. O therwise, the value of PaCO, under control is slightly different but a stable value is obtained after 10 minutes. More experiments must be d one in order to establish the real limits of such a system and optimiz e the gain of the control system.