FUZZY-LOGIC CONTROL OF INSPIRED ISOFLURANE AND OXYGEN CONCENTRATIONS USING MINIMAL FLOW ANESTHESIA

In order to evaluate the performance of feedback fuzzy logic control o f inspired oxygen and isoflurane concentrations, we studied 30 patient s undergoing discectomy for lumbar (n = 26) or cervical (n = 4) disc h erniation. Patients were allocated random to one of two groups: a stan dard group (n = 15) with low flow anaesthesia (1.2-1.3 litre min(-1)) and manual control of gas concentrations; and a fuzzy group (n = 15) w ith minimal flow (0.5 litre min(-1)) and fuzzy logic feedback control of gas concentrations. Fuzzy logic control achieved and maintained ver y accurately the desired isoflurane concentration. Oxygen concentratio n was controlled more precisely than in the standard group. Delivery a nd costs of oxygen and nitrous oxide were significantly lower in the f uzzy group (P < 0.01). Accumulation of foreign gases was observed in o ne patient during low flow and in 11 patients during minimal flow anae sthesia. In conclusion, fuzzy logic control of inspired oxygen and iso flurane concentration during minimal flow anaesthesia was reliable and reduced anaesthetic gas delivery and costs.