Pneumothorax in the Supine Patient

Routine posteroanterior chest radiographs and computed tomography scans are more sensitive for detecting pneumothoraces than anteroposterior chest radiographs. However, supine chest radiographs are commonly performed as part of the initial and routine assessment of trauma and critically ill patients. Rates of occult pneumothorax can be as high as 50% and have a significant impact in the mortality of these patients; thus, a prompt diagnosis of this entity is important. This pictorial essay will illustrate the pleural anatomy, explain the distribution of air within the pleural space in the supine position, and review the radiologic findings that characterize this entity.