In the case of tracheal intubation using a video laryngoscope, both techniques, one is 'conventional technique' in which intubation is performed by placing the blade tip on the vallecula and the other is 'sliding technique' performed by sliding the blade under the epiglottis, are commonly conducted by anesthesiologists. Investigators would like to compare if the sliding technique can improve the condition of tracheal intubation in patients wearing semi-rigid neck collars in cervical spine surgery.

For patients who need to limit the movement of the cervical spine, the tracheal intubation becomes difficult because the head must be positioned in the neutral position. Most of all, with a semi-rigid neck collar that maintains the neutral position of the head and neck, movement is limited and the mouth is not well-opened make the environment of tracheal intubation worse, which result in hypoxia or throat complications related to general anesthesia. Fortunately, it is possible that the development of video laryngoscope assists tracheal intubation easier for patients who have the limited movement of the cervical spine. However, the preferred intubation style and instrument selection for each operator are varied; the established method is required. In the case of tracheal intubation using a video laryngoscope, both techniques, one is 'conventional technique' in which intubation is performed by placing the blade tip on the vallecula and the other is 'sliding technique' performed by sliding the blade under the epiglottis, are commonly conducted by anesthesiologists. Investigators would like to compare if the sliding technique can improve the condition of tracheal intubation in patients wearing semi-rigid neck collars in cervical spine surgery.

Inclusion Criteria:

- Adult patients (over 19 years of age) with ASA class I-III undergoing cervical spine surgery at our institution in the department of spine neurosurgery

Exclusion Criteria:

• When rapid sequence induction is required
• When awake intubation is required
• If a subject is on the medication for asthma
• If as subject cannot read or understand the consent form of study