Air can enter the mediastinum when
(See also Overview of Pleural and Mediastinal Disorders.)
Most often, people have chest pain below the breastbone. The pain may be severe.
When doctors do a physical examination, they may hear a crunching or crackling noise when they listen to the chest through a stethoscope. A chest x-ray is done to confirm the diagnosis.
Usually, treatment is not necessary. However, the problem that caused pneumomediastinum may require treatment.