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 common method to inflate the endotracheal tube cuff is palpation method. However, the palpation of the cuff is not accurate because of the different size between the pilot balloon and the cuff. Thus, the investigators hypothesized that the different size of the tube will affect the accuracy of the palpation method.

Inclusion Criteria:

• 1. Adult male patients who require endotracheal intubation using the endotracheal tube size of 6.0 or 8.0

Exclusion Criteria:

• 1. Patients under 20 years old
• 2. Patients receiving emergency surgery
• 3. Patients with tracheostomy tubes
• 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
• 7. Patient with endotracheal mass in the trachea where the cuff is located
• 8. Tracheal deviation is observed in the neck due to tumor in the neck

Adult male patients who require endotracheal intubation using the endotracheal tube size of 6.0 or 8.0