This prospective randomized controlled trial aims to compare the effects of high-flow nasal oxygen (HFNO) and conventional face mask oxygen therapy on cerebral oxygenation during procedural sedation performed outside the operating room. Adult patients undergoing elective diagnostic or interventional procedures under procedural sedation will be randomly assigned to receive either HFNO or conventional face mask oxygen. Regional cerebral oxygen saturation will be continuously monitored using near-infrared spectroscopy (NIRS), while sedation depth will be assessed using the Patient State Index (PSI, SedLine) and the Modified Observer's Assessment of Alertness/Sedation (MOAA/S) scale. Secondary outcomes include peripheral oxygenation, ventilation parameters, arterial blood gas values, airway interventions, hemodynamic variables, and patient and practitioner satisfaction.