Endotracheal tube is a commonly used for general anesthesia in head and neck surgery. It is necessary to place the endotracheal tube in the trachea of the patient and then inflate the cuff with air. This is because the air-inflated cuff contacts the inner wall of the patient's trachea to deliver oxygen through the tube. If the cuff does not inflate, oxygen will leak through the space between the cuff and the patient's trachea. In addition, the risk of pneumonia increases. Therefore, after placing the endotracheal tube in the patient's trachea, the cuff is immediately inflated with air. However, when the cuff is inflated using an excess of air, the cuff may pressurize the mucous membrane of the tracheal wall and cause ischemia. Pressure in the over-inflated cuff was also found to be associated with post-operative sore throat, vocal cord paralysis, and nerve damage. Therefore, appropriate amount of air should be used to inflate the cuff into the air and adjust the pressure within the cuff to be within the range of 20-30 cmH2O. The authors thought that the pressure in the cuff could be changed during the operation due to various factors and that the pressure in the cuff should be monitored continuously. In this study, the investigators will monitor the cuff pressure during anesthesia and analyze the factors affecting the cuff pressure.

Inclusion Criteria:

• 1. Adults who require endotracheal intubation for head and neck surgery under general anesthesia

Exclusion Criteria:

• 1. Patients under 20 years old
• 2. Patients who should undergo tracheostomy
• 3. Patients who need to use an endotracheal tube without a cuff
• 4. Pregnant women
• 5. Patients who can not read the consent form or are not fluent in Korean
• 6. Patients who refused the clinical trial

Adults who require endotracheal intubation for head and neck surgery under general anesthesia