The usefulness of videolaryngoscope has been verified by several studies, and the frequency of videolaryngoscopy is increasing in clinical practice. Data on the use of videolaryngoscopes, however, were not sufficiently accumulated when compared with data on the use of previously used macintosh laryngoscopes. In addition, videolaryngoscopy increases the success rate of endotracheal intubation compared to conventional macintosh laryngoscopy, but endotracheal intubation with videolaryngoscope is not successful in all cases with one intubation attempt. Therefore, if the difficult endotracheal intubation with the videolaryngoscope can be predicted in advance, it may be possible to improve the success rate of intubation by reducing unnecessary use of the videolaryngoscope and preparing other equipment. There are many studies on the preoperative examination that can predict the difficulty of intubation when using a macintosh laryngoscope. However, there are still attempts to find screening tests that predict precisely the difficult endotracheal intubation because the accuracy of screening tests is not high. In particular, there is a lack of research on factors that can predict difficult endotracheal intubation when using videolaryngoscope. Therefore, the investigators aimed to investigate the factors predictive of difficult endotracheal intubation when attempting intubation using videolaryngoscope.

Inclusion Criteria:

1. Patients who are scheduled for endotracheal intubation using a videolaryngoscope for general anesthesia

Exclusion Criteria:

1. Patients who are planned to receive awake intubation
2. Patients who have a tracheostomy tube
3. Patients who do not cooperate in evaluating the head and neck due to mental retardation
4. Trauma patient wearing a neck collar due to cervical fracture
5. Pregnancy

Patients who are scheduled for endotracheal intubation using videolaryngoscope for general anesthesia