3. Calcified tracheal rings

Ultrasound machines are bedside tools readily available in most intensive care units. They allow for rapid evaluation of the upper airway. Recently, ultrasound has been demonstrated to predict difficult endotracheal intubations (ETT) and to confirm positions of the endotracheal tube within the tracheal lumen while excluding inadvertent esophageal intubation.

In a successful endotracheal intubation, a “Bullet sign” is visualized. A “Bullet sign” is the loss of reverberations in the central part of the tracheal lumen that is occupied by the ETT. Esophageal intubation will display on the short axis neck ultrasound two side by side lumens, one being the trachea and the other the inappropriately positioned ETT within the esophagus, also referred to as the “double track sign”.

Tracheal cartilage is rich in water and hypoechoic to US, the bright line delineates the air-tissue interface beyond which ultrasound waves are not transduced. Artifact reverberations (note asterisk) can be appreciated within the lumen of the trachea (Figures 3 & 4).

Figure 3 Short axis neck ultrasound from a healthy individual.


Figure 4. Long axis neck ultrasound from a healthy individual.

The thyroid gland is isoechoic to hyperechoic vascular tissue on both sides of the lower portion of the extra thoracic trachea (having an almost “granular” appearance) with an isthmus present anteriorly.

Figures 1, 2 and 5 belong to the patient in the clinical vignette, calcified tracheal cartilage acts as a barrier to US wave conduction and do not allow the normal ultrasound imaging of the tracheal wall. As stated, healthy tracheal rings are well delineated hypoechoic structures that cannot be clearly appreciated in (Figures 1 and 2). The presence of calcified trachea was confirmed on review of a recent CT of the chest (Figure 5).

Figure 5. Lateral view of thoracic CT scan in soft tissue windows showing the calcified tracheal rings.


  1. Dinsmore J, Heard AM, Green RJ. The use of ultrasound to guide time-critical cannula tracheotomy when anterior neck airway anatomy is unidentifiable. Eur J Anaesthesiol. 2011 Jul;28(7):506-10. [CrossRef] [PubMed]
  2. Osman A, Sum KM. Role of upper airway ultrasound in airway management. J Intensive Care. 2016 Aug 15;4:52. [CrossRef] [PubMed]
  3. Ding LW, Wang HC, Wu HD, Chang CJ, Yang PC. Laryngeal ultrasound: a useful method in predicting post-extubation stridor. A pilot study. Eur Respir J. 2006 Feb;27(2):384-9. [CrossRef] [PubMed]
  4. Shibasaki M, Nakajima Y, Ishii S, Shimizu F, Shime N, Sessler DI. Prediction of pediatric endotracheal tube size by ultrasonography. Anesthesiology. 2010 Oct;113(4):819-24. [CrossRef] [PubMed]
  5. Kundra P, Mishra SK, Ramesh A. Ultrasound of the airway. Indian J Anaesth. 2011 Sep;55(5):456-62. [CrossRef] [PubMed]

Home/Critical Care