The frontal & lateral chest x-rays reveal pneumomediastinum & pneumopercardium.

The patient was not unstable. The x-rays were initially misinterpreted as normal and the patient was recalled. They underwent a repeat chest x-ray 24 hours after initial presentation which showed resolution of mediastinal air and were clinically asymptomatic.

A sinister cause for above presentation not to be missed is oesophageal rupture.