AN APPLICATION OF FUZZY INFERENCE TO THE BLOOD-PRESSURE CONTROL SYSTEM IN ANESTHESIA

Abstract

During a surgical operation, anesthesiologists evaluate the patient's vital signs at every moment. The control of blood pressure is the most important task for them in order to keep the patient's normal physiological conditions against surgical stimuli. In this system, we adopt two variables for the input informations, the value of blood pressure at the observation time and the value before 30 seconds, and also one variable for the output, the inhalational concentration of general anesthetics. The rule for the relationship between two input variables and one output is constructed upon clinical experiences. After converting the input data to the fuzzy information with the membership function, the inhalational concentration is determined by using a fuzzy inference. For the clinical demand, two types of rules, the "rapid rule" and the "slow rule" are prepared for responding to the abrupt and gradual changes of blood pressure, respectively. From the results of animal experiments and some clinical trials, it was suggested that this control system was a useful supporting system for anesthesiologists.