Airway Ultrasound (POCUS) — Sonoanatomy & Tube Confirmation

🔊 Airway Ultrasound

"Point-of-care ultrasound has moved airway assessment from the purely external to the sonographic. A high-frequency linear probe on the anterior neck identifies the cricothyroid membrane before it is needed, confirms tracheal versus oesophageal intubation in real time, and screens the gastric antrum for aspiration risk — all at the bedside, without radiation."

Synthesised from Kristensen MS et al., ultrasound for airway management; Miller's Anesthesia.

Sonoanatomy of the anterior neck

Probe — high-frequency (7–15 MHz) linear transducer, transverse then longitudinal, sweeping from mentum to sternal notch.
Layers — skin, subcutaneous fat, strap muscles, then the cartilages: thyroid (inverted V), cricoid (rounded, hypoechoic), and the tracheal rings as a "string of pearls" longitudinally.
Air–mucosa interface — a bright hyperechoic line with posterior reverberation / comet-tail artefact (air blocks the beam, so you see the near wall, not the lumen).
Cricothyroid membrane — identified between thyroid and cricoid cartilages (longitudinal "string-of-pearls" method) and marked before an anticipated difficult airway/FONA.
Oesophagus — usually postero-lateral (commonly to the left) of the trachea; seen to distend with an oesophageal intubation.

Clinical use	What you look for
Confirm tracheal intubation	Single air–mucosa interface (tracheal); a second parallel interface = "double-tract sign" of oesophageal intubation. Bilateral lung sliding confirms ventilation and excludes endobronchial placement.
Locate the cricothyroid membrane	Mark before predicted difficult airway / obese / distorted necks — faster and more accurate than palpation for FONA.
Predict difficult laryngoscopy	Increased anterior neck soft tissue / distance from skin to hyoid, epiglottis or thyrohyoid membrane.
Gastric antrum	Antral cross-sectional area / content (empty, clear fluid, solid) to gauge aspiration risk in the fasted-uncertain patient.
Others	Predict paediatric tube size, confirm bougie/tube depth, screen for subglottic stenosis, guide percutaneous tracheostomy.

Real airway ultrasound — labelled images

Longitudinal airway ultrasound showing the cricothyroid membrane between thyroid and cricoid cartilage — **Cricothyroid membrane** (longitudinal) — the hyperechoic band linking the hypoechoic thyroid and cricoid cartilages, above the air–mucosal interface. Mark it before FONA.

Longitudinal airway ultrasound showing tracheal rings as a string of beads — **Tracheal rings** (longitudinal) — the "**string of beads**": cricoid then rings T1–T4 sitting on the bright air–mucosal interface.

Transverse airway ultrasound at the trachea with comet-tail artefact — **Trachea (transverse)** — inverted-U tracheal cartilage over the air–mucosal interface with posterior **comet-tail** artefact; thyroid gland and strap muscles alongside.

Transverse airway ultrasound of the vocal cords in abduction and adduction — **Vocal cords** (transverse, through the thyroid cartilage) — seen moving in **abduction** and **adduction**; a dynamic check of cord movement.

Transverse airway ultrasound showing the oesophagus lateral to the trachea — **Oesophagus (E)** — usually postero-lateral (often to the left) of the trachea, near the thyroid and carotid (CA); it distends with an oesophageal intubation.

Airway ultrasound showing the endotracheal tube double-tract sign — **ETT confirmation** — a tracheal tube produces the "**double-tract / double-lumen sign**"; a second parallel air column indicates oesophageal placement.

Ultrasound images: Osman A, Sum KM. Role of upper airway ultrasound in airway management. J Intensive Care. 2016;4:52 — CC BY 4.0, via PubMed Central. Used with attribution.