Pulmonary aspiration during tracheal intubation for anesthesia can cause fatal respiratory complications. Takenaka's study of mannequins reported that the risk of airway contamination by reflux gastric contents could be minimized by applying a 15-degree Trendelenburg position and a Sellick position with neck extention. However, the clinical performance of tracheal intubation in this position has not been studied. Also, the difference between the effects of direct laryngoscope and video laryngoscope on tracheal intubation is not known yet.

Therefore, this study aims to compare the intubation time among intubation through direct laryngoscope and video laryngoscope in the Sellick and Trendelenburg position, and intubation in the conventional sniffing position.

Inclusion Criteria:

• Age >= 19 years old
• ASA I or II
• Patients who need nasotracheal intubation for surgery

Exclusion Criteria:

• Anatomical deformity in head and neck
• Patients who have risk of pulmonary aspiration
• Patients with cervical deformities or pain
• BMI >35