• Anil Agarwal, Prabhat K Singh, Sanjay Dhiraj, Chandra M Pandey, and Uttam Singh.
• Department of Anesthesia, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India. aagarwal@sgpgi.ac.in
• Can J Anaesth. 2002 Dec 1;49(10):1040-3.

PurposeOne hundred percent O(2) is used routinely for preoxygenation and induction of anesthesia. The higher the O(2) concentration the faster is the development of atelectasis, an important cause of impaired pulmonary gas exchange during general anesthesia (GA). We evaluated the effect of ventilation with 0.4 FiO(2) in air, 0.4 FiO(2) in N(2)O and 100% O(2) following intubation on the development of impaired gas exchange.MethodsTwenty-seven patients aged 18-40 yr, undergoing elective laparoscopic cholecystectomy were administered 100% O(2) for preoxygenation (three minutes) and ventilation by mask (two minutes). Following intubation these patients were randomly divided into three groups of nine each and ventilated either with 0.4 FiO(2) in air, 0.4 FiO(2) in N(2)O or 100% O(2). Arterial blood gases were obtained before preoxygenation and 30 min following intubation for PaO(2) analysis. Subsequently PaO(2)/FiO(2) ratios were calculated. Results were analyzed with Student's t test and one-way ANOVA. P value of < or = 0.05 was considered significant.ResultsVentilation of the lungs with O(2) in air (FiO(2) 0.4) significantly improved the PaO(2)/FiO(2) ratio from baseline, while 0.4 FiO(2) in N(2)O or 100% O(2) worsened the ratio (558 +/- 47 vs 472 +/- 28, 365 +/- 34 vs 472 +/- 22 and 351 +/- 23 vs 477 +/- 28 respectively; P < 0.05).ConclusionVentilation of lungs with O(2) in air (FiO(2) 0.4) improves gas exchange in young healthy patients during GA.

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