Are expiratory radiographs more sensitive than inspiratory radiographs for the diagnosis of pneumothorax in the emergency department? A retrospective observational study.

Expiratory radiographs are sometimes performed in addition to inspiratory radiographs when a diagnosis of pneumothorax is suspected. There is little published evidence to support this practice and most studies suggest the additional radiograph does not confer any benefit in terms of increased sensitivity. The present study is the first to assess if specialist emergency physicians are more likely to detect a pneumothorax on an inspiratory radiograph compared to an expiratory radiograph. Across two urban district EDs 103 paired radiographs positive for pneumothorax and 112 negative controls were identified for inclusion in the study. These were reviewed by three specialist emergency physicians who rated them as either positive or negative for pneumothorax. The mean sensitivity for the three reviewers was 84.8% (95% CI 82.0-87.5) for the inspiratory radiographs and 91.9% (95% CI 88.2-95.6) for the expiratory radiographs, a mean absolute difference of 7.1% (95% CI 2.2-12.1, P = 0.025) in favour of expiratory radiographs. When reviewed by emergency physicians the present study found expiratory radiographs confer an increase in sensitivity for the diagnosis of pneumothorax compared with inspiratory radiographs. In certain patients where the clinical suspicion for pneumothorax is high performing an expiratory radiograph may increase the likelihood of the diagnosis being made in the ED.

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