Oxygen in air (FIO2 0.4) improves gas exchange in young healthy patients during general anesthesia

Abstract

Purpose: One hundred percent O2 is used routinely for preoxygenation and induction of anesthesia. The higher the O2 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 F1O2 in air, 0.4 F1O2 in N2O and 100% O2 following intubation on the development of impaired gas exchange. Methods: Twenty-seven patients aged 18-40 yr, undergoing elective laparoscopic cholecystectomy were administered 100% O2 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 F1O2 in air, 0.4 F1O2 in N2O or 100% O2. Arterial blood gases were obtained before preoxygenation and 30 min following intubation for PaO2 analysis. Subsequently PaO2/F1O2 r-atios were calculated. Results were analyzed with Student's t test and one-way ANOVA. P value of ≤ 0.05 was considered significant. Results: Ventilation of the lungs with O2 in air (F1O2 0.4) significantly improved the PaO2 /F1O2 ratio from baseline, while 0.4 F1O2 in N2O or 100% O2 worsened the ratio (558 ± 47 vs 472 ± 28, 365 ± 34 vs 472 ± 22 and 351 ± 23 vs 477 ± 28 respectively; P < 0.05). Conclusion: Ventilation of lungs with O2 in air (F1O2 0.4) improves gas exchange in young healthy patients during GA.