Failure of advanced airway security has been reported that it could lead lethal complication such as brain hypoxic damage. There have been controversial reports for the airway assessment tests which can predict difficult laryngoscopy. Therefore, we evaluated diagnostic validity of pre-existing airway assessment tests and scoring system using a gray zone approach in patients undergoing general anesthesia required endotracheal intubation.

POGO(percentage of glottic opening)will be evaluated by an attachable fiberoptic scope (AV scope. CAREtec CO.Ltd, Kangwon-Do, South Korea)

Inclusion Criteria:

• 20 to 80 years old patients undergoing general anesthesia for any operation.

Exclusion Criteria:

• previous difficult airway history
• upper airway obstruction disease
• congenital disorders that are known to relate with difficult airway
• neurologic symptom associated with neck extension
• emergent operation

Patients undergoing general anesthesia for any surgery at Samsung medical center