Effect of high fractional inspiratory oxygen on postoperative pulmonary function: a randomized–controlled study

Background Although a high fraction of inspired oxygen (FiO2) could reduce surgical site infection, there is a concern that it could increase postoperative pulmonary complications, including hypoxemia. However, there is an advantage for preoperative high FiO2 before induction of anesthesia as it decreases the incidences of desaturation and wound infection. Our aim was to assess whether different levels of FiO2 affect pulmonary function tests. Patients and methods Ninety patients scheduled for elective abdominal hysterectomy were randomized to receive either preoxygenation with 1.0 FiO2 for 3 min, then continued on 1.0 FiO2 till the end of surgery (group A), or preoxygenation with 1.0 FiO2 for 3 min, then continued on 0.4 FiO2 till the end of surgery (group B), or preoxygenation with 0.4 FiO2 then continued on 0.4 FiO2 till the end of surgery (group C). The oxygenation index (PaO2/FiO2) was measured every 30 min during anesthesia and 2 h after extubation. Pulmonary function test was measured on the morning of surgery and 2 h after extubation. Results Five minutes after intubation, the median PaO2/FiO2 was 483 (371–490) mmHg in group A, 420 (336–490) mmHg in group B, and 450 (350–485) mmHg in group C (P = 0.24). Two hours after extubation, the PaO2/FiO2 was reduced to 333 (314–342) mmHg in group A, 328 (311–357) mmHg in group B, and 342 (303–316) mmHg in group C (P = 0.55). The median functional vital capacity were 1950 (1600–2120), 1850 (1570–2250), and 1900 (1490–2020) ml at baseline and 1650 (1370–1953), 1670 (1340–2350), and 1711 (1412–2410) ml 2 h after extubation in groups A, B, and C, respectively (P = 0.66). Conclusion We found no significant difference in the oxygenation index or pulmonary function tests between patients administered different levels of FiO2.