The aim of this study is to evaluate the appropriateness of the two kinds of nasotracheal tube (PORTEX POLAR [Smiths Medical International, Hythe, United Kingdom], Mallinckrodt TaperGuard [Covidien, Ireland]) depth in neutral, extended and flexed neck position when the upper border of the cuff of endotracheal tube is located 3cm below the vocal cords in neutral neck position.

Inclusion Criteria:

1. Adult patients who undergoes elective surgery under general anesthesia with nasotracheal intubation

Exclusion Criteria:

1. Patients under 20 years old
2. Patients with ASA class IV or higher
3. Pregnant women
4. Patients receiving emergency surgery
5. Patients who have nasal disease or who undergo nose surgery because of nasal disease
6. Patient with craniofacial anomaly
7. Patients with impaired cervical motion
8. Patients who can not read the consent form or are not fluent in Korean (illiterate, foreigner)
9. Patients who refused the clinical trial Patients with dementia or cognitive impairment