ONLINE EXPIRATORY FLOW-VOLUME CURVES DURING THORACIC-SURGERY - OCCURRENCE OF AUTO-PEEP

Now-volume loops were monitored continuously in 39 patients undergoing thoracic surgery requiring one-lung ventilation. In 26 of the 39 pati ents (67%), auto-positive end-expiratory pressure (auto-PEEP) was seen on the flow-volume curves during both two-lung and one-lung ventilati on. Eighty-seven percent of the patients whose trachea was intubated w ith a smaller size (35- and 37-French gauge) double-lumen tracheal tub e exhibited auto-PEEP, compared with patients in whom the tube used wa s larger (39- or 41-French gauge: 54% and 50%, respectively). Before o peration, mean airway resistance was significantly greater in patients who exhibited auto-PEEP during anaesthesia (2.4 cm H2O litre(-1) s) t han in patients without auto-PEEP (1.7 cm H2O litre(-1) s).