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

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), high-flow nasal oxygenation preoxygenation by a single anesthetist (high-flow nasal oxygenation).