Combination of COMBO endoscopy oropharyngeal airway and high-flow nasal cannula oxygenation in sedated gastrointestinal endoscopy for morbidly obese patients: a Simon two-stage trial

BACKGROUND: Hypoxemia during sedated gastrointestinal endoscopy affects over 40% of morbidly obese (BMI ≥ 35 kg/m2) patients. High-flow nasal cannula (HFNC) alone often fails due to persistent airway collapse. The COMBO endoscopy oropharyngeal airway provides mechanical support while delivering oxygen. This study aimed to assess the efficacy of combined COMBO-HFNC oxygenation for preventing hypoxemia in this high-risk population. METHODS: In a prospective, single-centre, Simon two-stage trial, 50 adults with morbid obesity scheduled for gastrointestinal endoscopy under propofol-alfentanil sedation received COMBO-HFNC oxygenation. The primary endpoint was hypoxemia (SpO₂ 75–90% for < 60 s) compared with a historical rate of 40%. Secondary endpoints were subclinical respiratory depression (SpO₂ 90–95%) and severe hypoxemia (SpO₂ < 75% or 75–90% ≥ 60 s). Rates were analysed with an exact one-sided binomial test (α = 0.05). RESULTS: All 50 participants completed the study. No patient developed hypoxemia (0%), significantly lower than the historical 40% (P < 0.001). Subclinical respiratory depression occurred in 8 patients (16%), and no severe hypoxaemic episodes were recorded. Transient hypotension occurred in 3 patients (6%), with no other complications. CONCLUSIONS: COMBO-HFNC oxygenation was associated with a 0% hypoxemia rate in morbidly obese patients undergoing sedated endoscopy without increasing adverse events. These findings suggest potential clinical value compared with historical conventional oxygenation strategies, but require confirmation in future multicentre randomized controlled trials to establish causal inference. TRIAL REGISTRATION: The trial was registered at the ClinicalTrials.gov on 1 February 2025 (NCT06812403).