Detection of pneumothoraces in patients with multiple blunt trauma: use and limitations of eFAST.

Background: Extended focused assessment with sonography for trauma (eFAST) has been shown to have moderate sensitivity for detection of pneumothorax in trauma. Little is known about the location or size of missed pneumothoraces or clinical predictors of pneumothoraces in patients with false-negative eFAST.

Methods: This retrospective cross-sectional study includes all patients with multiple blunt trauma diagnosed with pneumothorax who underwent both eFAST and CT performed in the ED of a level 1 trauma centre in Switzerland between 1 June 2012 and 30 September 2014. Sensitivity of eFAST for pneumothorax was determined using CT as the gold standard. Demographic and clinical characteristics of those who had a pneumothorax detected by eFAST and those who did not were compared using the Mann-Whitney U or Pearson's χ tests. Univariate binary logistic regression models were used to identify predictors for pneumothoraces in patients with negative eFAST examination.

Results: The study included 109 patients. Overall sensitivity for pneumothorax on eFAST was 0.59 and 0.81 for pneumothoraces requiring treatment. Compared with those detected by eFAST, missed pneumothoraces were less likely to be ventral (30 (47.6%) vs 4 (9.3%), p <0.001) and more likely to be apical and basal (7 (11.1%) vs 15 (34.9%), p=0.003; 11 (17.5%) vs 18 (41.9%), p=0.008, respectively). The missed pneumothoraces were smaller than the detected pneumothoraces (left side: 30.7±17.4 vs 12.1±13.9 mm; right side: 30.2±10.1 vs 6.9±10.2 mm, both p <0.001). No clinical variables were identified which predicted pneumothoraces in falsely negative eFAST. Among those pneumothoraces missed by eFAST, 30% required tube thoracostomy compared with 88.9% of those detected with eFAST.

Conclusion: In our study, pneumothoraces missed by eFAST were smaller and in atypical locations compared with those detected by eFAST and needed thoracic drainage less often.