This prospective observational cohort study will evaluate the incidence and independent predictors of clinically relevant hypotension and hypoxemia during propofol-based diagnostic gastrointestinal endoscopy in adult patients at a tertiary referral hospital in Vietnam. Participants undergoing diagnostic upper gastrointestinal endoscopy, colonoscopy, or combined diagnostic procedures with propofol administration will be followed from pre-procedure assessment through the early recovery period. The study will assess demographic, clinical, airway, procedural, and sedation-related variables associated with clinically relevant cardiopulmonary adverse events.