Nasal continuous positive airway pressure (nCPAP) has been shown to effectively relieve upper airway obstruction in patients with OSA as it creates a pneumatic stent in the hypopharynx that reduces obstruction and allows for continuous oxygenation. Nasal ventilation was also proven to be more effective than combined oral-nasal ventilation during induction of general anesthesia in adult subjects. However, it is not clear if nasal mask can be used safely for oxygenation and ventilation in patients undergoing colonoscopy.