What is the role of ultrasonography in the evaluation of pneumothorax?

Updated: Apr 28, 2020
  • Author: Brian J Daley, MD, MBA, FACS, FCCP, CNSC; Chief Editor: Mary C Mancini, MD, PhD, MMM  more...
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Prehospital, portable ultrasonography may provide diagnostic and therapeutic benefit when conducted by a proficient examiner who used goal-directed and time-sensitive protocols, as determined in an air rescue setting. [43] Further study in this area may help to determine the indications and role of prehospital ultrasonography. In experienced hands, ultrasonography may be quicker and more accurate than radiography for distinguishing free pleural effusion (a finding in pneumothorax) in time-sensitive evaluations. [44]

Ultrasonography is increasingly used in the acute care setting as a readily available bedside tool, especially in the intensive care unit (ICU) and emergency department (ED) settings. This modality provides a rapid imaging option for diagnosis of pneumothorax, but this evaluation should not delay treatment of a clinically apparent tension pneumothorax. [45, 46, 47]

Many trauma centers are incorporating chest ultrasonography as an adjunct to the Focused Assessment with Sonography in Trauma (FAST) examination. Knudtson et al, in a prospective analysis of 328 consecutive trauma patients at a level 1 trauma center, obtained a specificity of 99.7% and an accuracy of 99.4%, and concluded that ultrasonography was a reliable modality for the diagnosis of pneumothorax in the injured patient. [46]

A prospective study by Brook et al designed to assess the accuracy of radiology residents in detecting pneumothoraces as part of the extended FAST (eFAST) examination concluded that ultrasonographic pneumothorax detection by these radiology residents was both accurate and efficient in the early detection of clinically important pneumothoraces. [48]

The investigators compared ultrasonographic pneumothorax detection (by the absence of parietal-over-visceral lung sliding with "comet tail" artifacts behind it) with the reference standard of chest CT in 169 consecutive trauma patients (ie, 338 lung fields). A sensitivity of 47%, specificity of 99%, positive predictive value of 87%, and negative predictive value of 93% was found; none of the small pneumothoraces missed by ultrasonography required drainage during the hospitalization period. [48]

In addition, Hernandez et al noted that ultrasonography is the only radiographic modality allowing patients with nonarrhythmogenic cardiac arrest to continue undergoing resuscitation while clinicians searching for easily reversible causes of asystole or pulseless electrical activity (PEA). [49] Their proposal is for further investigation into a protocol (using the acronym CAUSE for cardiac arrest ultrasound exam) in which cardiac arrest patients, concurrent with resuscitation, receive bedside ultrasonography to look for cardiac tamponade, massive pulmonary embolus, severe hypovolemia, and tension pneumothorax. [49] Their hope is that the eventual adoption of ultrasonography in this setting may allow increased "real-time" diagnostic acumen, decreasing the time required to receive appropriate condition-related therapy.

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