Comparison of Four Views to Single View Ultrasound Protocols to Identify Clinically Significant Pneumothorax

Abstract

Objective

Ultrasound has been shown to be effective at identifying a pneumothorax (PTX), however the additional value of adding multiple views has not been studied. Single and four-view protocols have both been described in the literature. The objective of this study was to compare the diagnostic accuracy of single-view vs. four-view lung ultrasound to detect clinically significant PTX in trauma patients.

Methods

This was a randomized, prospective trial on trauma patients. Adult patients with acute traumatic injury undergoing CT scan of the chest were eligible for enrollment. Patients were randomized to a single view or four views of each hemi-thorax prior to any imaging. Ultrasounds were performed and interpreted by credentialed physicians using a 7.5Mhz linear array transducer on a portable US machine with digital clips recorded for later review. Attending radiologist interpretation of the chest CT was reviewed for presence or absence of PTX with descriptions of small foci of air or minimal PTX categorized as clinically insignificant.

Results

A total of 260 patients were enrolled over a two-year period. 139 patients received a single view of each chest wall and 121 patients received four views. There were a total of 49 patients that had a pneumothorax (19%), and 29 of these were clinically significant (11%). In diagnosis of any PTX, both single-view and four-view techniques showed poor sensitivity (54.2% and 68%) but high specificity (99% and 98%). For clinically significant PTX, single-view ultrasound demonstrated a sensitivity of 93% (95% CI 64.1-99.6) and a specificity of 99.2% (95.5-99.9), with sensitivity of 93.3% (66-99.7) and specificity of 98% (92.1-99.7) for four views.

Conclusions

Single-view and four-view chest wall ultrasound demonstrate comparable sensitivity and specificity for PTX. The additional time to obtain four views should be weighed against the absence of additional diagnostic yield over a single view when using ultrasound to identify a clinically significant PTX.

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