If the patients's teeth are weak or the mouth dose not open well, the lightwand is a useful device when endotracheal intubation is necessary.

Therefore, if the appropriate position of the light beam is determined and the distance of the light source suitable for intubation using the lightwand is obtained from anatomical structures such as thyroid cartilage and cricoid cartilage, it is clinically useful. Because it can prevent unnecessary deep insertion or shallow insertion that can cause damage to anatomical structures during intubation.

Studies have been reported on the proper position to bend the lightwand and the appropriate angle to bend when performing endotracheal intubation with lightwand. For ease of procedure, the assistant has to lift the patient's lower jaw or perform a neck extension.

However, there is no report on the position of the lightbulb when the light passes through the front of the airway and neck and appears bright in the midpoint.

The prodcedure is as follows.

1. FOB examination and check position of light below 1cm from vocal cord
2. lightwand intubation aimed at checkpoint
3. measurement of distance from thyroid cartilage/cricoid cartilage to light point

Inclusion Criteria:

• impossibility of neck extension
• trismus
• weak teeth

Exclusion Criteria:

• previous history of larynx or neck surgery
• no informed consent

This is an adult patient who is 18 years of age or older who undergoes general anesthesia requiring intubation.

Among them, patients who are unable to extend their necks, have trismus or have weak teeth are selected.