The aim of this study is to evaluate the effect of high-flow nasal cannula oxygen administration on apnea in patients undergoing general anesthesia with rigid bronchoscopy compared with standard anesthesia methods.

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.)

triple (Participant, Care Provider, investigator)