In the emergency department (ED), colorimetric or quantitative capnography is the gold standard for confirmation of endotracheal tube placement. Capnography may be unreliable in patients with severe pulmonary obstruction, greatly reduced pulmonary circulation, or cardiac arrest. Transtracheal ultrasound imaging with a linear or curvilinear probe placed transversely at the cricothyroid membrane can confirm tracheal tube placement when capnography is unavailable or thought to be unreliable.
To evaluate the diagnostic accuracy of transtracheal ultrasound for detecting tracheal intubation, researchers performed a meta-analysis of human studies that compared ultrasound and capnography. Eleven studies (969 intubations), of which eight (713 intubations) evaluated emergency intubations, were included in the analysis. Ultrasound was predominantly performed by emergency physicians. The pooled sensitivity and specificity of ultrasound for detecting tracheal intubation were 98% and 98%, respectively, for all intubations and 98% and 94%, respectively, for emergency intubations.
Transtracheal ultrasound is simple and fast, provides real-time results, and uses a technology available in most EDs. Ultrasound, in addition to auscultation, should be used as an alternative method of confirming successful endotracheal tube placement when capnography is either not immediately available or thought to be unreliable.
This is especially useful during cardiac arrest situations when CPR is in progress and you can not wait to obtain a chest x-ray to confirm placement and capnography is not reliable unless ROSC has occurred.
Das SK et al. Transtracheal ultrasound for verification of endotracheal tube placement: A systematic review and meta-analysis. Can J Anaesth 2015 Apr; 62:413.