Inclusion Criteria:  Children under 11 years old undergoing general anesthesia with American Society of Anesthesiologists Physical Status 1 or 2.  Exclusion Criteria:  Refusal of enrollment from one or more legal guardians of the patient Plan of usage of supraglottic airway device as airway maintenance device Presence of upper respiratory tract infection of lung disease Premature infants younger than postconceptual age of 40 weeks Anticipation of difficult bag-mask ventilation due to facial anomaly or micrognathia Other conditions that are considered inappropriate for the study