First described in 1819 by René Laennec,[2][3] the condition can result from physical trauma or other situations that lead to air escaping from the lungs, airways, or bowel into the chest cavity.

Other symptoms include laboured breathing, voice distortion (as with helium) and subcutaneous emphysema, specifically affecting the face, neck, and chest.

Pneumomediastinum may also present with symptoms mimicking cardiac tamponade as a result of the increased intrapulmonary pressure on venous flow to the heart.

[8] It can be caused by a pulmonary barotrauma induced by a person moving from a higher to a lower pressure environment, such as when a scuba or surface-supplied diver,[9][10] a free-diver after lung-packing,[11] or an airplane passenger[12] ascends.

[10] In rare cases, pneumomediastinum may also arise as a result of blunt chest trauma (e.g. car accidents, fights, over pressure of breathing apparatus), while still evolving in the same fashion as the spontaneous form.