Effect of high-flow nasal preoxygenation on anesthetic preparation time for general anesthesia in emergency caesarean delivery: a prospective randomized cross-over simulation study

BACKGROUND: General anesthesia may be required for emergency caesarean deliveries when neuraxial anesthesia is not feasible. Anesthetic preparation, including adequate facemask preoxygenation, may take longer in the absence of a trained assistant, potentially prolonging the decision-to-delivery interval. High-flow nasal oxygenation (HFNO) offers hands-free preoxygenation, but its impact on anesthetic preparation time has not been assessed. METHODS: We conducted a prospective, randomised, single-centre, cross-over simulation study with eight obstetric anesthetists, each performing four predefined preoxygenation scenarios on the same healthy female volunteer in whom abdominal compression was applied to produce 20% reduction in functional residual capacity: standard facemask preoxygenation by a single anesthetist (Control), facemask preoxygenation with the mask held by the volunteer (Patient-Assisted) or assisted by a nurse anesthetist (nurse-assisted), HFNO preoxygenation by a single anesthetist (HFNO). The primary endpoint was time from entry-to-operating room to readiness-for-induction. RESULTS: All 32 simulations were completed. The median (IQR) times from the volunteer's entry in the operating room to readiness for anesthesia induction were 4.14 (3.96-4.80) minutes (Control), 3.16 (3.03-3.38) minutes (HFNO), 2.61 (2.45-2.81) minutes (Patient-Assisted), and 2.29 (2.25-3.09) minutes (Nurse-Assisted). A generalized linear mixed model found significant difference between the Control and the HFNO scenario (mean difference: -1.12 minutes, 95% CI: -2.04 to -0.18); the Patient-Assisted scenario (mean difference: -1.73 minutes, 95% CI: -2.61 to -0.86); and the Nurse-Assisted scenario (mean difference: -1.81 minutes, 95% CI: -2.71 to -0.91). CONCLUSIONS: HFNO preoxygenation was associated with reduced anesthetic preparation time compared with facemask preoxygenation in simulated emergency obstetric anesthesia managed by a single anesthetist without assistance.