"Using a linear probe in a transverse orientation on the midline, anterior neck, the subglottis may be found just inferior to the cricoid cartilage 15. Bordered superficially by the characteristic uniform hyperechoic echotexture of the thyroid gland, the anterior tracheal wall will appear as a curved, hyperechoic interface with reverberation artifacts posteriorly akin to an aerated lung. The greatest transverse diameter between hyperechoic air-mucosal interfaces should then be obtained; normal measurements fall between 17-24 mm, with values below 15 mm suspicious for stenosis 14. Measurement of this diameter may also subsequently, if intubation is required, inform the choice of the optimal endotracheal tube size 16."
"Using a linear probe in a transverse orientation on the midline, anterior neck, the subglottis may be found just inferior to the cricoid cartilage 15. Bordered superficially by the characteristic uniform hyperechoic echotexture of the thyroid gland, the anterior tracheal wall will appear as a curved, hyperechoic interface with reverberation artifacts posteriorly akin to an aerated lung. The greatest transverse diameter between hyperechoic air-mucosal interfaces should then be obtained; normal measurements fall between 17-24 mm, with values below 15 mm suspicious for stenosis 14. Measurement of this diameter may also subsequently, if intubation is required, inform the choice of the optimal endotracheal tube size 16."