Hypoxia is the most common adverse event during propofol sedation for gastrointestinal endoscopy. The STOP-BANG questionnaire is a widely used, simple assessment tool for screening obstructive sleep apnea (OSA) risk. A STOP-Bang score ≥5 indicates high-risk OSA patients who are more prone to hypoxia during sedated endoscopy. Our team's preliminary clinical research found that High-Flow Nasal Cannula (HFNC) may reduce hypoxemia risk, but there are limited dedicated studies focusing specifically on high-risk OSA patients, with controversial results. This study aims to investigate whether HFNC can reduce the incidence of hypoxia during sedated gastrointestinal endoscopy in high-risk obstructive sleep apnea patients.

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.