The mask ventilation is a necessary procedure to provide oxygenation before the tracheal intubation although the gastric insufflation occurs during the mask ventilation. Sugammadex, which is recently introduced, enables the use of high-dose muscle relaxant without concerning the delayed recovery of neuromuscular blockade. It seems that there is no need to perform the mask ventilation in adults with normal airway if the investigators use high-dose muscle relaxant for the anesthetic induction because adequate muscle relaxation can be achieved within 1-2 minutes. Therefore, the investigators hypothesized that routine mask ventilation is not needed in adult patients with normal airway. The investigators will compare the incidence of desaturation and gastric insufflation between the patients with mask ventilation and the patients without mask ventilation.

Inclusion Criteria:

• adult patients of age over 20 years for scheduled surgery with more than one and a half hours under general anesthesia

Exclusion Criteria:

• anticipated difficult mask ventilation,
• anticipated difficult intubation,
• ASA class 3 or 4,
• preoperative saturation less than 92%.,
• saturation less than 98% after preoxygenation
• body mass index over 35 kg/m2,
• obstructive sleep apnea,
• mass in the oral cavity or in the trachea,
• pregnant woman