CLINICAL-EVALUATION OF AN AUTOMATIC BLOOD-PRESSURE CONTROLLER DURING CARDIAC-SURGERY

Objective. During surgery, computers can be of great use to support th e anesthesiologist in providing task automation. In this paper we desc ribe a closed loop blood pressure controller and show the results of i ts clinical evaluation. Methods. The controller is based on a simple a nd robust Proportional-Integral controller and a supervising, rule bas ed, expert system. Adaptive control is necessary because the sensitivi ty of the patients to sodium nitroprusside varies over a wide range. T hirty-three clinical tests during cardiac surgery, including the cardi opulmonary bypass phase, were performed. Results, On average the contr oller was in automatic mode for 90.6 +/- 9.6% of the time. The perform ance during automatic control showed the mean arterial pressure to be within 10 mmHg of che setpoint for 71.4 +/- 15.5% of the time. The ave rage absolute distance to the setpoint was 8.1 +/- 7.2 :mmHg. Conclusi ons, The overall performance of the controller was noted as very satis factory by the anesthesiologists.