Introduction: The supine antero-posterior (AP) chest radiograph (CXR) is an insensitive test for detecting post-traumatic pneumothoraces (PTXs). Computed tomography (CT) often identifies occult pneumothoraces (OPTXs) that were not diagnosed on CXR. The purpose of this study was to prospectively determine the incidence, and validate previously identified clinical predictors, of OPTXs after blunt trauma.
Methods: All severe blunt injured patients (injury severity score (ISS)>or=12) presenting to a level 1 trauma centre over a 17-month period were prospectively evaluated. Thoracoabdominal CT scans and corresponding CXRs were reviewed at the time of admission. Patients with OPTXs were compared to those with overt PTXs regarding incidence and previously identified predictive risk factors (subcutaneous emphysema, rib fractures, female sex and pulmonary contusion).
Results: CT imaging was performed concurrent to CXR in 405 blunt trauma patients (ISS>or=12) during the study period. PTXs were identified in 107 (26%) of the 405 patients. Eighty-one (76%) of these were occult when CXRs were interpreted by the trauma team. Concurrent chest trauma predictive of OPTXs was limited to subcutaneous emphysema (p=0.003). Rib fractures, pulmonary contusions and female sex were not predictive.
Conclusions: OPTXs were missed in up to 76% of all seriously injured patients when CXRs were interpreted by the trauma team. This is higher than previously reported in retrospective studies and is likely based on the difficult conditions in which the trauma team functions. Subcutaneous emphysema remains a strong clinical predictor for concurrent OPTXs.