ARTERIAL-PRESSURE CONTROL WITH ISOFLURANE USING FUZZY-LOGIC

Arterial pressure is still one of the most important measures in estim ating the required dose of inhaled anaesthetics. It is measured easily and reacts rapidly which makes it suitable as a variable for feedback control of depth of anaesthesia. Fuzzy logic, a novel approach to fee dback control, was used to control arterial pressure in 10 patients du ring intraabdominal surgery by automatic adjustment of the concentrati on of isoflurane in fresh gas. During anaesthesia, fuzzy control perio ds of 45-min duration were alternated randomly with human control peri ods of equal duration. During the skin incision period (-3 to +12 min) 48.2% of all fuzzy control pressure values were within +/-10% of the desired mean arterial pressure compared with 40.4% of the human contro l values (P < 0.05). The corresponding values for the remainder of the operation were 78.3% and 83.2%, respectively. Thus fuzzy outperformed human control at skin incision, but was slightly inferior during the rest of the operation. We conclude that fuzzy logic is a promising new technique for control of isoflurane delivery during routine anaesthes ia.