Inclusion and exclusion criteria
impaired consciousness, gastroesophageal disease, cranial fractures, craniofacial malformations
Patients aged ≥ 20 years who were scheduled to undergo orotracheal intubation for general anaesthesia from November 2020 to January 2021 were enrolled in this study. Patients with cranial fractures or craniofacial malformations that prevented oxygen delivery through the nostrils, those who could not cooperate due to impaired consciousness, and those who could not fast prior to surgery or were at risk of aspiration of gastric contents due to gastroesophageal disease were excluded from the study. Patients who required awake intubation were also excluded.