This series of ultrasound images explores the airway in transverse section from the thyroid cartilage, through the cricothyroid membrane and on to the cricoid cartilage.
Upper thyroid cartilage – transverse view
The thyroid cartilage is triangular with an acute anterior angle in its cranial portion, rather like a steep sided volcano. This is more prominent in the male.
Mid thyroid cartilage – transverse view
As one proceeds caudally down the thyroid cartilage the anterior angle becomes less acute, like a less steeply sided volcano. In this image the false cords are seen.
Lower thyroid cartilage – transverse view
Cricothyroid membrane – transverse view
The air interface just deep to the cricothyroid membrane causes a bright linear reflection. The appearance of this has been likened to the caldera of a volcano.
Cricoid cartilage – transverse view
As one progresses further distally the rounded anterior part of the cricoid cartilage is seen. The appearance depends on the degree of age related calcification of this primarily cartilaginous structure.
Acoustic shadowing caused by calcification will completely obstruct the echogenic air interface. Whilst the cricoid remains cartilaginous and some ultrasound transmission occurs the air interface will be able to be seen, although less brightly than at the cricothyroid membrane.
Distal to the cricoid cartilage the tracheal rings and intervening spaces will be readily discernible.
The ultrasound appearance of the upper airway explained
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