The chest x-ray shows extensive subcutaneous emphysema involving the chest wall and the neck. There is pneumomediastinum. The patient also has multiple rib fractures on the right. There is a small right sided pleural effusion (haemothorax in the context of trauma).

Subcutaneous emphysema can make interpretation of chest x-ray tricky. Detection of pneumothorax can be difficult on the chest x-ray. CT scan is the diagnostic test to characterize underlying injuries.

Air from subcutaneous emphysema may track to the face, neck and deeper into the mediastinum. Although harmless on its own, associated injuries (pneu/haemothorax etc) need attention. A sinister cause not to be missed is oesophageal rupture.