Objective To compare the preoxygenation efficacy of continuous positive airway pressure (CPAP) mode and conventional mode during induction of general anesthesia.

Methods From May 1st, 2020 to December 31st, 2021, 81 patients who were treated in Zhongshan Hospital (Xiamen Branch), Fudan University were included, they were divided into spontaneous breathing group before induction (n=27), pressure support assisted ventilation PSV group after induction (n=26), and CPAP group before induction (n=28). To compare the time for fraction of expirated oxygen (FeO₂) to reach 90%; FeO₂, arterial blood oxygen partial pressure (PaO₂), carbon dioxide partial pressure (PaCO₂) in 4 min without ventilation; incidence of reflux during intubation; hemodynamic changes.

Results The time required for FeO₂ to reach 90% in the CPAP group was shorter than that in the spontaneous breathing group (P=0.01), and there was no significant difference compared with the PSV group. Cox proportional-hazard regression analysis showed that the time required to reach 90% FeO₂ in the three groups was not significantly correlated with gender, age, and BMI. Compared with the spontaneous breathing mode, the CPAP mode was HR=0.430 (95%CI 0.243-0.761; P=0.04); compared with PSV mode, the CPAP mode was HR=0.810 (95%CI 0.474-1.383; P=0.44). The PaCO₂ in the CPAP group was lower than that in the spontaneous breathing group at 4 minutes without ventilation (P=0.03), and there was no significant difference compared with the PSV group. There was no significant difference in the hemodynamic changes before and after intubation.

Conclusion CPAP mode of pre-oxygenation before induction of general anesthesia is more effective than the spontaneous breathing mode before induction, the time required is shorter, and the PaCO₂ is lower in the 4-min non-ventilation state.