The aim of this study is to evaluate the effect of high-flow nasal cannula oxygen administration on maintenance of oxygenation and removal of carbon dioxide during apnoeic period in pediatric patients undergoing general anesthesia with rigid bronchoscopy

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 7 or younger who meet American Society of Anesthesiologists (ASA) physical class 2-4

Exclusion Criteria:

• 1. Patients undergoing extracorporeal membrane oxygenation (ECMO)
• 2. Patients with active nasal bleeding), severe nasal obstruction, recent nasal trauma of surgery
• 3. Patients with current maxillofacial trauma or basal skull fracture
• 4. Patients with active nasal bleeding), severe nasal obstruction, recent nasal trauma of surgery
• 5. Extremely low birth weight infant and premature infant less than 28 weeks gestation age
• 6. Patients who had previously undergone rigid bronchoscopy / surgery
• 7. If the parent of subject includes a person who can not read the written consent (eg, illiterate, foreigner, etc.)

Patients 7 years or younger who undergo general anesthesia with rigid bronchoscopy