Automatic Control of Gas Exchange During Cardiopulmonary Bypass

~ An automatic oontml 'Y'~m wM :::~:~e~n:t" gM exchange during oacdiopulmo I nary hyp"' (CPB). Tho Automated Extmomponoal G"' Exchange Sy,tem (AEGES) control' the blood flow rate and/or the flow of gas to the oxygenator in order to meet user-defined setpoints for P02 and PC02 of blood drained from the patient while maintaining safe pressures in the CPB circuit and/or the patient's circulation. Venous blood gases were used as the basis for control because they reflect the amount of oxygen/C02 consumed/produced by the patient given the present rate of delivery via CPB. In the event of an alarm or upon the perfusionist' s command, AEGES reverts to manual control of blood flow and/or sweep flow. AEGES was tested in a hypothermia model of CPB in sheep, where it successfully regulated P02 and PC02 within 5% of setpoint during cooling from 38 to 2YC. In order to control the blood gases to setpoints of P02=45 mmHg and PC02=40 mmHg in the venous drainage, AEGES reduced blood flow from 2.4 to 1.6 L!min and sweep flow from 2.2 to 0.7 L!min. AEGES is intended to act as a tool for the perfusionist to assist in maintaining consistent blood gas conditions. AEGES can be integrated with other control systems (e.g., reservoir level control and blood temperature control), further automating the CPB procedure; however, in no way could this system replace the perfusionist.