Hypoxia represents the most frequent adverse event during propofol-sedated gastrointestinal endoscopy. The STOP-BANG questionnaire serves as a widely adopted, straightforward tool for screening obstructive sleep apnea (OSA) risk, with a score ≥5 identifying high-risk OSA patients who are particularly susceptible to hypoxia under sedation. Although preliminary research from our team suggests that High-Flow Nasal Cannula (HFNC) may lower the incidence of hypoxemia, evidence remains limited and inconsistent in studies specifically targeting high-risk OSA populations. Therefore, this multicenter randomized controlled trial aims to evaluate whether HFNC can effectively reduce the occurrence of hypoxia during sedated gastrointestinal endoscopy in patients identified as high-risk for OSA.

Inclusion Criteria:

• Age ≥18 years.
• STOP-Bang score ≥5.
• Scheduled for sedated gastrointestinal endoscopy (gastroscopy, colonoscopy, or combined gastroscopy + colonoscopy).
• The estimated duration of the procedure does not exceed 45 minutes.
• Patients have signed the informed consent form.

Exclusion Criteria:

• Coagulation disorders or bleeding tendency (e.g., oral/nasal bleeding risk, mucosal injury, space-occupying obstructions).
• Active upper respiratory tract infection (oral, nasal, or pharyngeal), or fever (core temperature >37.5°C).
• Chronic obstructive pulmonary disease or other acute/chronic pulmonary diseases requiring long-term or intermittent oxygen therapy, or preoperative SpO₂ ≤ 92% on room air.
• Severe organ dysfunction, including: Cardiac insufficiency (<4 METs), Severe renal insufficiency (requiring dialysis), Diagnosed severe hepatic insufficiency, Increased intracranial pressure, ASA physical status ≥ IV.
• Confirmed pregnancy or current breastfeeding.
• Known allergy to sedatives (e.g., propofol) or medical adhesives.
• Multiple traumatic injuries.
• Current participation in another clinical trial.
• Other conditions deemed unsuitable by the investigator