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Hypoxemia is the most common adverse event during sedated gastrointestinal endoscopy. Patients with high obstructive sleep apnea (OSA) risk (STOP-Bang ≥5) are susceptible due to sedation-induced loss of upper airway tone exacerbating airway collapsibility. Although high-flow nasal cannula (HFNC) benefits general at-risk populations, its efficacy in this specific cohort remains uncertain, as its mild positive pressure falls far below therapeutic continuous positive airway pressure levels for moderate-to-severe OSA, questioning its ability to stent the collapsible airway. Our prior proof-of-concept study in this cohort observed a 5% incidence of hypoxemia with HFNC, confirming feasibility and safety and justifying this confirmatory trial.

This prospective, multicenter, randomized controlled single-blind trial will enroll 600 adults (STOP-Bang score ≥5) undergoing elective sedated gastroenteroscopy across three centers. Participants will be 1:1 randomized (stratified by center) to HFNC (30 L/min pre-oxygenation, 60 L/min post-induction) or conventional nasal cannula (6 L/min). Both groups receive standardized propofol-alfentanil sedation. The primary outcome is the proportion of patients with at least one episode of hypoxemia (SpO₂ 75%-90% <60 s). Secondary outcomes include the proportion of patients with at least one episode of severe hypoxemia (SpO₂ <75% or 75%≤SpO₂<90% ≥60 s), the proportion with subclinical respiratory depression (90%≤SpO₂<95%), and the frequency of other adverse events.

This trial will provide definitive evidence on HFNC's efficacy in high-risk OSA patients, addressing whether it can overcome pressure limitations to prevent hypoxemia. Results are expected to inform sedation management guidelines, establish a new standard of care for this subgroup, and enhance procedural safety.

The trial was registered at the ClinicalTrials.gov on 14 December 2025 (NCT07307560).