Clinical evaluation of an automatic blood pressure controller during cardiac surgery

During surgery, computers can be of great use to support the anesthesiologist in providing task automation. In this paper we describe a closed loop blood pressure controller and show the results of its clinical evalua- tion.Methods. The controller is based on a simple and robust Proportional-Integral controller and a supervising, rule based, expert system. Adaptive control is necessary because the sensitivity of the patients to sodium nitroprusside varies over a wide range. Thirty-three clinical tests during cardiac surgery, including the cardiopulmonary bypass phase, were performed. Results. On average the controller was in auto- matic mode for 90.6 ?? 9.6% of the time. The performance during automatic control showed the mean arterial pressure to be within 10 mmHg of the setpoint for 71.4 ?? 15.5% of the time. The average absolute distance to the setpoint was 8.1 ?? 7.2 mmHg. Conclusions. The overall performance of the controller was noted as very satisfactory by the anes- thesiologists.