Contribution of high-flow nasal oxygenation to optimizing maternal preoxygenation and anesthetic preparation time for emergency cesarean delivery under general anesthesia : a prospective experimental study in a healthy volunteer (preoxce study)

Position du problème et objectif(s) de l’étude

Emergency cesarean delivery under general anesthesia carries a substantial risk of maternal hypoxemia, exacerbated by third-trimester physiological changes. Effective preoxygenation—defined as an end-tidal oxygen fraction (FeO₂) ≥90%—is recommended to mitigate this risk. In France, fewer than 5% of cesarean deliveries require general anesthesia, primarily in extreme emergencies (“code red”) involving patients not in labor or lack effective epidural analgesia, thereby necessitating general anesthesia. These clinical situations are often managed by a single anesthesiologist under intense time constraints, with a recommended decision-to-delivery interval of less than 15 minutes, which may compromise optimal preoxygenation. High-flow nasal oxygenation (HFNO) has demonstrated efficacy in delaying desaturation during apnea in non-obstetric patients, but data supporting its use in obstetrics are limited. Several randomized trials have failed to show HFNO’s superiority over standard facemask preoxygenation in achieving FeO₂ ≥90%, and most do not specify whether preoxygenation was conducted by a single provider or with assistance. Its role in time-critical obstetric settings—particularly when performed by a single anesthesiologist—has yet to be evaluated, despite frequent staffing limitations in emergency obstetric care.

Matériel et méthodes

We conducted a prospective, single-center, simulation-based study to evaluate whether HFNO can improve preoxygenation and anesthetic readiness times in this context. A healthy, non-pregnant female volunteer with no cardiopulmonary or neurological history was recruted. Pregnancy-related changes in third-trimester respiratory physiology—specifically a ≥20% decrease in functional residual capacity—were reproduced by applying abdominal compression in the supine position under pulmonary function monitoring. Eight experienced obstetric anesthesiologists each completed four randomized scenarios: (1, control) standard facemask preoxygenation by a single anesthesiologist; (2) patient-assisted facemask; (3) HFNO; and (4) facemask preoxygenation assisted by a nurse anesthetist. The primary outcome was the time from operating room entry to anesthetic “green light”—defined as complete cardiorespiratory monitoring and FeO₂ >90% sustained >10 seconds and rapid sequence induction medications prepared—, analyzed using a multiple linear mixed-effects regression model. Secondary outcomes were time comparisons across all four strategies, the number of medication errors and deviations from standards anesthetic practices. Registration: ClinicalTrials.gov (NCT04814628). Ethics approval: CPP 2021-A00047-34.

Résultats & Discussion

HFNO significantly reduced time to "green light" compared to the control (3.22 vs. 4.34 min; mean difference 1.12 min [0.19–2.05], p = 0.0159). Significantly shorter times were also observed in patient-assisted (2.60 min) and nurse-assisted (2.53 min) strategies. No significant differences were observed in medication errors or deviations.

Conclusion

HFNO represent a useful strategy to optimize maternal preoxygenation and anesthetic preparation times in emergency cesarean deliveries under general anesthesia, particularly when the anesthesiologist is solely responsible of perioperative managment, while maintaining patient safety. These findings also highlight the critical importance of adequate staffing in obstetric anesthesia. To our knowledge, this is the first study to evaluate HFNO in this specific context using a physiologically realistic volunteer model.

Auteurs

Charles PARIS (1) , Alexandre RISO (2), Marie NAAIM (2), Jean-Charles GLERANT (3), Dominique CHASSARD (2), Lionel BOUVET (2) - (1)Hospices Civils De Lyon, Lyon, France, Lyon, France, (2)Department Of Pediatric And Obstetric Anesthesiology And Critical Care, Hôpital Femme Mère Enfant, Hospices Civils De Lyon, Lyon, France, Lyon, France, (3)Pulmonary Function Testing Laboratory, Department Of Pulmonology, Groupement Hospitalier Est, Hospices Civils De Lyon, Lyon, France, Lyon, France

Orateur(s)

Charles PARIS (Lyon)