High-flow Nasal Oxygen During Rigid Bronchoscopy Under General Anesthesia: a Randomized Controlled Trial

Inclusion Criteria: * 1\. Patients undergoing general anesthesia with stent placement or bougination, biopsy or removal of a foreign body or a mass through a rigid bronchoscope * 2\. Patients aged 19 or older who meet American Society of Anesthesiologists (ASA) physical class 2-4 Exclusion Criteria: * 1\. Patients with dementia or cognitive impairment * 2\. pregnant women * 3\. Patients undergoing extracorporeal membrane oxygenation (ECMO) * 4\. Patients with active nasal bleeding), severe nasal obstruction, recent nasal trauma of surgery * 5\. Patients with current maxillofacial trauma or basal skull fracture * 6\. Patients who had previously undergone rigid bronchoscopy / surgery * 7\. If the subject includes a person who can not read the written consent (eg, illiterate, foreigner, etc.)