Anesthesia and intervention
palate, glottis, epiglottis
The patients were positioned supine with their heads on a standard surgical pillow. Standard monitoring of vital signs included electrocardiography, non-invasive blood pressure measurement, and peripheral oxygen saturation measurement. After 3 min of denitrogenation with 100% oxygen, general anesthesia was induced with 1–1.5 mg kgIn the J group, an independent assistant in charge of airway maneuvers stood at the patient’s left side and applied a jaw-thrust maneuver prior to FOI. In the M group, a McIvor blade (size #4 from McIvor mouth gag set; Karl Storz GmbH, Tuttlingen, Germany) was placed with the patient’s head extended. The blade was fully inserted into the midline of the oropharyngeal space, placed at the base of the tongue, and gently lifted forward to clear the airway. This practice was performed by a maneuvering assistant who maintained the position of the patient’s head and continuously pulled the blade forward and upward (Fig. (In performing FOI, the anesthesiologist inserted the bronchoscope into the mouth along the dorsum of the patient’s tongue and advanced it through the vocal cords. Airway clearance at the level of the soft palate was assessed by checking the position of the uvula or the soft palate from the dorsum of the tongue and was classified as clear (If the uvula did not touch the tongue), partially obstructed (If the uvula was in contact with the tongue), and complete obstruction (If the whole soft palate abutted the tongue). On the contrary, airway clearance at the epiglottis level was assessed by observing whether the epiglottis touched the posterior pharyngeal wall or not and was classified as clear (full view of the glottis), partially obstructed (If the sides of the epiglottis touched the posterior pharyngeal wall and there is a partial view of the glottis), and complete obstruction (If the glottis was not completely in sight) (Fig. Bronchscopic assessment of airway clearance at the soft palate and epiglottis levels.If the approach to the vocal cord and carina was unsuccessful in 60 s or peripheral oxygen saturation decreased below 90%, two further trials were conducted after 2 min of mask ventilation with 3% sevoflurane in 100% oxygen. If successful insertion into the trachea was not performed after three trials, the FOI was recorded as a failure, and the anesthesiologist performed tracheal intubation using direct laryngoscopy.After the fiberoptic bronchoscope entered the glottis and approached the carina level, the tracheal tube was advanced over the bronchoscope into the trachea, and the bronchoscope was removed to complete the FOI. If resistance was met during tube advancement, the tracheal tube was pulled out, rotated counterclockwise in steps of 90°, and advanced until it overcame resistanceAfter FOI was completed, the tracheal tube was connected to a ventilator circuit, and manual ventilation was attempted to confirm successful intubation with the presence of end-tidal carbon dioxide (EtCO