It is traditionally taught that the location to place an ultrasound probe to detect a pneumothorax with point-of-care ultrasound (POCUS) is the anterior chest, given the theory that air will collect at the least dependent area in the supine patient. There is a wide variety of scanning protocols with varying accuracy and completeness. We sought to assess the optimal area to scan for diagnosing pneumothorax by mapping the location of traumatic pneumothorax on computed tomography (CT).

Patients were selected after a retrospective cohort of adult patients who presented to a regional trauma center with a pneumothorax diagnosed on CT. Data were extracted using a standardized data collection tool, and 20% of charts were reviewed by two reviewers. Predefined zones were used to map the areas of pneumothoraces. Theoretical sensitivity and 95% confidence intervals (CIs) are reported.

A total of 203 traumatic pneumothoraces were reviewed from 2006 to 2016. The majority of the pneumothoraces were found in an area defined by the para-sternal border and the mid-clavicular line from the inferior aspect of the clavicle to the physiologic lung point (liver on the right, heart on the left). The theoretical sensitivity for pneumothorax of scanning this area was 91.6% (95% CI, 86.9–95%).

This study suggests any POCUS scanning protocol for traumatic pneumothorax should include an area from the inferior border of the clavicle at the parasternal border down to the liver or cardiac lung points and then the mid clavicular line down to the liver or cardiac lung points.