EFFECT OF INTRAOPERATIVE MECHANICAL VENTILATION USING 50-PERCENT INSPIRED OXYGEN ON PULMONARY OXYGENATION

Forty-three ASA Grade I patients scheduled for elective abdominal surg ery received at random either 25% or 50% inspired oxygen for intra-ope rative mechanical ventilation lasting 4-6h. Pulse oximetry was monitor ed continuously. Venous admixture was assessed from the PaO2/FIO2 rati o and was measured twice intraoperatively: at the time of incision, an d during surgical wound closure. PaO2 was measured 1 h after extubatio n having breathed room air for 10 min, if tolerated. The patients in t he two groups were similar in regard to general characteristics, and h ad similar operations. Patients given oxygen 50% had operations that l asted longer, which made the trial more sensitive. The inspired oxygen did not affect pulmonary gas exchange either within each group or bet ween groups under the conditions of the study. In no patient did pulse oximetry record an oxygen saturation below 95% intra-operatively.