Pneumomediastinum

Free air in the mediastinum (space betweens the lungs) which may give rise to pneumothorax or pneumopericardium and compromise the lungs or heart.

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Abnormal presence of air in mediastinal tissues; multiple causes include pulmonary interstitial emphysema, ruptured bleb, perforation of the cervical or thoracic esophagus or airways, cervicomediastinal infection, and perforated abdominal viscus. SYN: mediastinal emphysema. [G. pneuma, air, + mediastinum]

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pneu·mo·me·di·as·ti·num .n(y)ü-mō-.mēd-ē-ə-'stī-nəm n, pl -ti·na -nə

1) an abnormal state characterized by the presence of gas (as air) in the mediastinum

2) the induction of pneumomediastinum as an aid to radiography

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pneu·mo·me·di·as·ti·num (noo″mo-me″de-əs-tiґnəm) [pneumo- + mediastinum] the presence of air or gas in the mediastinum, which may interfere with respiration and circulation, and may lead to such conditions as pneumothorax or pneumopericardium. It may occur as a result of trauma or a pathologic process, or it may be induced deliberately as a diagnostic procedure. Called also Hamman disease or syndrome and mediastinal emphysema. See illustration.

Pneumomediastinum, showing characteristic continuous radiolucent line extending from one hemidiaphragm to the other (arrows) and air displacing the left mediastinal pleura (arrowheads).