Inclusion Criteria:  Patients receiving tracheal intubation for general anesthesia Patients with physical status 1, 2, or 3 by American Society of Anesthesiologists Physical Status.  Exclusion Criteria:  Body mass index <18.5 kg/m2 or >35 kg/m2 Patients with a history of airway surgery Patients with increased risk of aspiration Patients who have any pathology (polyp, tumor, or inflammation) in the upper airway and larynx