Pulmonology · Medical Literature
High-flow nasal cannula oxygenation in sedated endoscopy for high-risk obstructive sleep apnea patients: study protocol for a multicentre randomised controlled trial.
Abstract
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).
Clinical relevance
Hypoxemia is the most frequent adverse event during propofol-based sedated gastrointestinal endoscopy, and patients with high-risk obstructive sleep apnea (STOP-Bang ≥5) are disproportionately vulnerable due to sedation-induced loss of pharyngeal muscle tone compounding pre-existing airway collapsibility. Despite growing adoption of high-flow nasal cannula (HFNC) oxygenation in broader at-risk endoscopy populations, its efficacy in this specific high-risk OSA cohort remains unestablished, as the modest positive airway pressure generated by HFNC falls well below therapeutic CPAP levels required to stent moderate-to-severe obstructed airways. A definitive randomised controlled trial is urgently needed to determine whether HFNC can meaningfully reduce hypoxemic events in this subgroup and thereby inform sedation safety guidelines.
Key findings
1. This is a prospective, multicentre, randomised controlled single-blind trial targeting 600 adults with STOP-Bang score ≥5 undergoing elective sedated gastroenteroscopy across three centres, powered to provide definitive evidence (specific power and alpha not reported in the abstract). 2. Participants are randomised 1:1 (stratified by centre) to HFNC versus conventional nasal cannula (CNC); no quantitative effect size, confidence intervals, p-values, or NNT/NNH are yet available as this is a protocol publication. 3. HFNC protocol: 30 L/min during pre-oxygenation phase, titrated to 60 L/min post-induction of sedation; CNC comparator delivers 6 L/min throughout. 4. Both arms receive standardised propofol-alfentanil sedation to minimise confounding from sedation regimen variability. 5. Primary outcome is the proportion of patients experiencing at least one hypoxemia episode (SpO2 75%–90% for <60 seconds); secondary outcomes include severe hypoxemia (SpO2 <75%, or SpO2 75%–<90% for ≥60 seconds) and subclinical respiratory depression (SpO2 90%–<95%). 6. A prior proof-of-concept study in this same cohort observed a 5% incidence of hypoxemia with HFNC, confirming feasibility and safety and serving as the basis for this confirmatory trial (no CI or p-value reported for this pilot estimate in the abstract).
Practice implications
Until trial results are available, clinicians should identify high-risk OSA patients prospectively using the STOP-Bang score (threshold ≥5) before elective sedated endoscopy and apply heightened respiratory monitoring regardless of oxygenation strategy chosen. The HFNC protocol tested in this trial — 30 L/min pre-oxygenation followed by 60 L/min post-induction with propofol-alfentanil — represents a pragmatic, protocol-driven approach that can be implemented across multicentre settings and should be considered investigationally for this subgroup pending definitive efficacy data. Results of this trial are anticipated to directly inform sedation management guidelines for high-risk OSA patients undergoing gastrointestinal endoscopy, potentially establishing HFNC as a new standard of care where conventional low-flow nasal cannula oxygenation has historically been insufficient.