This multicenter, prospective, randomized controlled trial aims to evaluate whether a novel multifunctional oropharyngeal airway (MOPA) reduces the incidence of hypoxemia in 1,518 adult patients (ASA I-II, aged 18-80 years) undergoing elective sedated gastrointestinal endoscopy. Patients are randomized 1:1 to receive either the MOPA (which integrates oxygen delivery, PETCO₂ monitoring, and airway support) or conventional nasal cannula with standard mouthpiece. The primary endpoint is the incidence of hypoxemia (75% ≤ SpO₂ \< 90% for \<60 seconds) during the procedure. Secondary outcomes include severe hypoxemia, hypercapnia, PETCO₂ monitoring success, airway interventions, adverse events, and satisfaction scores. The study is conducted across 29 centers in China, with centralized randomization via an EDC system, blinded outcome assessment, and statistical analysis using a two-sided alpha of 0.05 (power 90%). Results are expected to provide high-level evidence for optimizing airway management during sedated endoscopy.