Hypoxaemia during sedated gastrointestinal endoscopy exceeds 40 % in morbidly obese (BMI ≥ 35 kg m-²) patients. High-flow nasal cannula alone often fails because of persistent airway collapse. A recent innovation in this domain is the COMBO Endoscopy Oropharyngeal Airway-a multifaceted device that encompasses capnography monitoring, bite block , oxygenation support, and oropharyngeal airway management.The purpose of this study is to investigate whether the combination of the COMBO Endoscopy Oropharyngeal Airway and High-Flow Nasal Cannula oxygenation reduces the incidence of hypoxemia in this population.

Inclusion Criteria:

• Age ≥ 18 years.
• BMI ≥ 35 kg/m².
• Patients undergoing gastroscopy or gastrointestinal endoscopy.
• 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, oropharyngeal obstruction) making oropharyngeal airway placement unsafe or unfeasible.
• 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.