Study procedures
’s mouth, incisors
Patients were categorized into the following two groups: Group C (control group) and Group S (slow endotracheal tube advancement). A predetermined computer-generated random number sequence was used to generate a randomization sequence for the two groups in a ratio of 1:1. Group allocation was performed on the morning of the day of surgery using sealed, number-coded envelopes.On arrival at the operating room, electrocardiogram, sphygmomanometer, pulse oximeter, bispectral index (BIS), and temperature were monitored. All patients were preoxygenated with 100% oxygen for 3 min. General anesthesia was induced with intravenous propofol 1.5–2 mg/kg, a target-controlled intravenous infusion of remifentanil 3.5–4.5 ng/mL, and intravenous rocuronium 0.6 mg/kg. After reducing the BIS to < 50 and ablation of the train-of-four (TOF) response (TOF 0), an investigator performed fiberoptic‐guided tracheal intubation. A Shiley™ Lo-Contour flexible reinforced endotracheal tube (Covidien Ireland Limited, Tullamore, Ireland), which had an outer diameter of 7.0 mm, was used for tracheal intubation. The endotracheal tube was premounted near the proximal site of the bronchoscope (Olympus LF-GP, Olympus Optical Co., Tokyo, Japan), and the bronchoscope was inserted into the trachea through the patient’s mouth while an assistant pulled the patient’s jaw.Once the bronchoscope was inserted into the trachea and reached the level of the carina, the endotracheal tube was advanced over the bronchoscope to a depth where the proximal end of the tube cuff was in contact with the patient’s incisors. The tube was subsequently advanced by an additional 10 cm to a depth of 17 cm from the patient’s incisors; the time required to perform this step was measuredStart and end of time measurement of endotracheal tube advancement (arrows).Medical staff who did not participate in the study performed the maintenance of general anesthesia and emergence. Sevoflurane in O