Nasotracheal tube is a commonly used for securing airways when performing general anesthesia in various oral and maxillofacial surgery such as tooth extraction, maxillary and mandibular fractures. After the nasotracheal tube is placed in the patient's trachea, the process of inflating the cuff at the end of the tube with air is required. If the cuff is inflated with excess air, the cuff may press the mucous membrane on the inner wall of the trachea, causing ischemia. Previous studies have shown that if the pressure in the cuff exceeds 30 cmH2O, it is highly likely to cause ischemia. In addition, it was found that the pressure in the excessively inflated cuff was associated with post-operative sore throat, vocal cord paralysis, and nerve damage. Moreover, the pressure in the cuff may vary according to the patient's head and neck posture. The pressure changes in the cuff may vary depending on the material and shape of the cuff. Therefore, we will investigate to evaluate the effect of head and neck posture on the pressure in the cuff of nasotracheal tube.

Inclusion Criteria:

• Adult patients over 20 years of age
• patients who require intubation of the nasotracheal tube to undergo oral and maxillofacial surgery under general anesthesia

Exclusion Criteria:

• Patients whose neck cannot be rotated due to cervical diseases, cervical fractures, and previous cervical surgery
• Patients undergoing emergency surgery
• Pregnant women