FUZZY-LOGIC CONTROL OF MECHANICAL VENTILATION DURING ANESTHESIA

We have examined a new approach, using fuzzy logic, to the closed-loop feedback control of mechanical ventilation during general anaesthesia . This control system automatically adjusts ventilatory frequency (f) and tidal volume (V-T) in order to achieve and maintain the end-tidal carbon dioxide fraction (FE'(CO2)) at a desired level (set-point). The controller attempts to minimize the deviation of both f and V-T per k g body weight from 10 bpm and 10 ml kg(-1), respectively, and to maint ain the plateau airway pressure within suitable limits. in 30 patients , undergoing various surgical procedures, the fuzzy control mode was c ompared with human ventilation control, For a set-point of FE'(CO2) = 4.5 vol% and during measurement periods of 20 min, accuracy, stability and breathing pattern did not differ significantly between fuzzy logi c and manual ventilation control. After step-changes in the set-point of FE'(CO2) from 4.5 to 5.5 vol% and vice versa, overshoot and rise ti me did not differ significantly between the two control modes. We conc lude that to achieve and maintain a desired FE'(CO2) during routine an aesthesia, fuzzy logic feedback control of mechanical ventilation is a reliable and safe mode of control.