Efficacy of preoxygenation with end-tidal oxygen when using different oxygen concentrations in patients undergoing general surgery: a single-center retrospective observational study

Abstract

Background: Preoxygenation is a simple but very important procedure for preventing arterial desaturation.A higher fraction of inspired oxygen (FiO 2 ) increases atelectasis and 80% oxygen results in significantly less atelectasis than 100% oxygen. We investigated whether there was a difference in the duration of adequate preoxygenation when using 100% and 80% oxygen. The proportion of patients for whom >3 min was required to achieve adequate preoxygenation was also investigated. Methods: The VitalDB database of patients underwent general surgery between February 1, 2021 and November 12, 2021 was reviewed. The time between the start of preoxygenation and the point where a 10% difference between FiO 2 and end-tidal oxygen (EtO 2 ) was defined as the preoxygenation time. The patients were classified into 100% and 80% groups according to the oxygen concentration. Propensity score matching (PSM) was performed to control for potential confounding factors. Results: Only 330 of the 1,377 patients had sufficient data for analysis: 179 in the 80% group and 151 in the 100% group. After PSM, 143 patients in each group were analyzed. The median preoxygenation time was 143 s [interquartile range (IQR): 120.5-181.5 s] and 144 s (IQR: 109.75-186.25 s) in the 80% and 100% groups, respectively [P=0.605; median difference =−1 s; 95% confidence interval (CI): −13 to 10]. Of the patients, 27% required >3 min for adequate preoxygenation.Conclusions: No difference in preoxygenation time was found between the 80% and 100% groups. For some patients, breathing for 3 min is not sufficient for adequate preoxygenation. EtO 2 monitoring aids evaluation of whether preoxygenation was adequate.

Preoxygenation in pregnant women—is it time to update the 2015 OAA/DAS guidance in light of the expanding evidence base for high flow nasal oxygen?

“…Using 100% oxygen for preoxygenation may result in absorption atelectasis after induction of anaesthesia. Therefore Jung et al investigated using a lower fraction of inspired oxygen (FiO 2 ) of 80%, finding no difference in patient desaturation rates vs. FiO 2 100% in a low risk population (10). This would not be appropriate in pregnant women due to their high risk of desaturation, instead other measures to prevent and reverse absorption atelectasis such Editorial Preoxygenation in pregnant women-is it time to update the 2015 OAA/DAS guidance in light of the expanding evidence base for high flow nasal oxygen?…”