airway US - Saving Lives With Sound

airway ultrasound

Airway ultrasound is a helpful technique in caring for critically ill patients to both identify the crico-thyroid membrane and/or guide placement (or displacement!) of an endotracheal tube.

The illustrations and images below will help you understand the key anatomy of the upper airway structures both externally and sonographically. We will also briefly cover lung ultrasound to confirm endotracheal tube placement.

Anatomy

Technique

Tracheal long axis

Ample amount of gel are required to acquire this view and a gentle technique to balance the probe on the bony prominences. Brace the hand on the chest to balance the probe. Be sure to line up the probe on the sagittal plane to capture the full trachea.

Tracheal long axis

In the clip shown here, we can see the trachea in long axis. The gap between the second and fourth arrow (arrow 3) points to the crico-thyroid membrane. This tissue-air interface often demonstrates A-lines secondary to a reverberation artifact (as seen in the lungs). The 4th arrow points to the cricoid cartilage.

Tracheal short axis

In this clip we can see a short-axis or transverse approach to imaging the trachea. While you can start caudad and move cephalad or vice versa, we recommend you start cephalad as the upside down V-shape of the thyroid cartilage is much easier to recognize than tracheal rings.

Guidance of ETT tube placement

Ultrasound can help identify esophageal intubation as shown in this video. The esophagus is often deep to the trachea and poorly visible (circled in yellow below), but can be seen readily with the introduction of the endotracheal tube and a tissue-plastic-air interface. Introduction of the tube into the airway will result in some turbulence of the trachea and occasionally, an enhancement of A-lines beneath the anterior surface of trachea.

Lung ultrasound to confirm pulmonary insufflation

Lung ultrasound can be used to detect lung sliding in both hemithoraces post intubation (reflecting appropriate placement of the tube in the main trachea). It can also be used to detect complications, including pneumothorax and right mainstem intubation.

Want to learn more about LUS for detection of pneumothorax? Please click the button below to learn more (will open another page).

References

Chou HC, Chong KM, Sim SS, et al. Real-time tracheal ultrasonography for confirmation of endotracheal tube placement during cardiopulmonary resuscitation. Resuscitation. 2013;84(12):1708-1712. doi:10.1016/j.resuscitation.2013.06.018.

Ebrahimi A, Yousefifard M, Kazemi HM, et al. Diagnostic accuracy of chest ultrasonography versus chest radiography for identification of pneumothorax: A systematic review and meta-analysis. Tanaffos. 2014;13(4):29-40.

Elliott DSJ, Baker PA, Scott MR, Birch CW, Thompson JMD. Accuracy of surface landmark identification for cannula cricothyroidotomy. Anaesthesia. 2010;65(9):889-894. doi:10.1111/j.1365-2044.2010.06425.x.

Hu WC, Xu L, Zhang Q, Wei L, Zhang W. Point-of-care ultrasound versus auscultation in determining the position of double-lumen tube. Med (United States). 2018;97(13). doi:10.1097/MD.0000000000009311.

Mallin M, Curtis K, Dawson M, Ockerse P, Ahern M. Accuracy of ultrasound-guided marking of the cricothyroid membrane before simulated failed intubation. Am J Emerg Med. 2014;32(1):61-63. doi:10.1016/j.ajem.2013.07.004.

Nicholls SE, Sweeney TW, Ferre RM, Strout TD. Bedside sonography by emergency physicians for the rapid identification of landmarks relevant to cricothyrotomy. Am J Emerg Med. 2008;26(8):852-856. doi:10.1016/j.ajem.2007.11.022.

Saporito A, Lo Piccolo A, Franceschini D, Tomasetti R, Anselmi L. Thoracic ultrasound confirmation of correct lung exclusion before one-lung ventilation during thoracic surgery. J Ultrasound. 2013;16(4):195-199. doi:10.1007/s40477-013-0050-9.

Sun JT, Chou HC, Sim SS, et al. Ultrasonography for proper endotracheal tube placement confirmation in out-of-hospital cardiac arrest patients: Two-center experience. J Med Ultrasound. 2014;22(2):83-87. doi:10.1016/j.jmu.2014.05.004.