Standard control theory approaches alone are not sufficient for the design of clinical control systems. Additional medical expertise has to be incorporated in order to achieve high quality and robust performance. The main problem to be overcome is the fact that no real time identifiability of the patient’s characteristics can be guaranteed, due to the low signal-to-noise ratio of the feedback signals in combination with unknown and possibly rapid changes in patient characteristics. Solutions to this problem are suggested by the manual control methods of expert clinicians. One solution is to adjust the controller’s parameters through monitoring its control performance. Another solution, in multi-input-multi-output controllers, is to allow variation of only one drug at a time. In addition, sometimes other goals are more important than keeping feedback signals at setpoint values. These goals need to be part of the clinical support system as well. The success of adding clinician-derived heuristics to standard control systems is illustrated by a number of single and multiple drug controllers, whose goal it is to support the clinician in the stabilization of the systemic arterial and/or the pulmonary artery pressure during and after cardiac surgery.
Background: We recently demonstrated the feasibility of computer controlled infusion of vasoactive drugs for the control of systemic hypertension during cardiac surgery. The objective of the current study was to investigate the effects of computer controlled blood pressures on hemodynamic stability when compared to conventional manual control. Method: Systemic artery blood pressures were managed either by computer (80 patients) or by a well‐trained anesthesiologist (80 patients). The vasodilator drugs sodium nitroprusside and nitroglycerin were used. Hemodynamic stability was determined from the standard deviation of the mean arterial pressure samples and from the percentages of time that arterial pressure was hypertensive or hypotensive. Results: The average standard deviation of the mean arterial pressure samples was smaller for the computer controlled than for the manually controlled group: 7.5±2.2 (mean±SD) versus 8.9±2.3 mmHg ( P <0.0001). The systemic artery pressure was less hypertensive and less hypotensive in the computer controlled than in the manually controlled group: 9.4±5.7 versus 13.1±6.0% ( P <0.0001) and 8.0±5.9 versus 11.8±7.4% ( P <0.0001), respectively. Conclusion: We conclude that, compared with manual control, computer control of systemic hypertension significantly improved hemodynamic stability during cardiac surgery.
