The chest x-ray shows ‘continuous diaphragm sign’, suggestive of pneumomediastinum.

Pneumomediastinum can be seen in cases of acute asthma exacerbation due to alveolar rupture secondary to air trapping.

Continuous diaphragm sign is seen when air appears between the pericardium & central diaphragm, allowing visualization of the central portion of the diaphragm in contiguity with the right and left hemidiaphragms.

Reference: Brant and Helms’ Fundamentals of Diagnostic Radiology, 5th Edition.