Measurements of the epiglottic thickness
A SSA-780A ultrasound scanner (Canon, Japan) equipped with a 7-12 MHz linear transducer was used. Participants lied in the supine position with their neckextended slightly. The sonographers identified the thyroid and cricoid cartilage and gently moved the linear probe superiorly. After tilting the probe, the epiglottis appeared (Figure 1). The epiglottic thickness was determined at three sites: midpoint, right edge, and left edge. The thickness on each edge was determined at a fixed distance from the midpoint18.
The epiglottic thickness was measured by two independent physicians who were well-instructed and qualified for airway US after a 1-h standard lecture and 8-h hands-on practice. Each sonographer measured the epiglottic thickness at each site for three times. The measurements were supervised and confirmed by a senior physician with more than 10 years of experience in sonographic examinations and certification from the Society of Ultrasound in Medicine (Blinded for review).