Pneumomediastinum

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Overview
Pneumomediastinum (from Greek pneuma - "air", also known as mediastinal emphysema) is a condition in which air is present in the mediastinum.

First described in 1819 by René Laennec, the condition can result from physical trauma or other situations that lead to high pressure within the alveoli of the lung, causing them to burst and leak air into the chest cavity.

Differential diagnosis of causes of pneumomediastinum
It is most commonly caused by:


 * Oesophageal rupture, for example in Boerhaave syndrome


 * Asthma or other conditions leading to alveolar rupture

It has also been associated with:
 * Mycoplasma pneumoniae pneumonia


 * anorexia


 * obesity

It can be induced to assist thoracoscopic surgery.

It can be caused by a pulmonary barotrauma resulting when a person moves to or from a higher pressure environment, such as when a Scuba diver , a free-diver or an airplane passenger ascends or descends.

Clinical Presentation & Diagnosis
Pneumomediastinum is uncommon, it occurs when air leaks from any part of the lung or airways into the mediastinum and is often recognized on auscultation by a "crunching" sound timed with the cardiac cycle (Hamman's crunch). Subcutaneous emphysema is one of the symptoms of pneumomediastinum.

The diagnosis can be confirmed via chest X-ray showing a radiolucent outline around the heart and mediastinum or via CT scanning of the thorax.

Acknowledgements
The content on this page was first contributed by: C. Michael Gibson M.S., M.D.

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