|Classification and external resources|
A CT scan showing air in the mediastinum
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 air escaping from the lungs, airways or bowel into the chest cavity.
Pneumomediastinum is uncommon and occurs when air leaks into the mediastinum. 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.
It is most commonly caused by:
- Oesophageal rupture, for example in Boerhaave syndrome
- Asthma or other conditions leading to alveolar rupture
- Bowel rupture, where air in the abdominal cavity tracts up into the chest.
It has also been associated with:
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.
Signs and Symptoms 
The main symptom is usually severe central chest pain. Other symptoms include laboured breathing, voice distortion (as with helium) and subcutaneous emphysema. It is often recognized on auscultation by a "crunching" sound timed with the cardiac cycle (Hamman's crunch).
The tissues in the mediastinum will slowly resorb the air in the cavity so most pneumomediastinums are treated conservatively. Breathing high flow oxygen will increase the absorption of the air. If the air is under pressure and compressing the heart, a needle may be inserted into the cavity, releasing the air. Surgery may be needed to repair the hole in the trachea, esophagus or bowel.
If there is lung collapse, it is imperative the affected individual lies on the side of the collapse, although painful, this allows full inflation of the unaffected lung.
- Laënnec RTH. De l’auscultation médiate ou Traité du Diagnostic des Maladies des Poumon et du Coeur. 1st ed. Paris: Brosson & Chaudé; 1819.
- Roguin A (2006). "Rene Theophile Hyacinthe Laënnec (1781-1826): the man behind the stethoscope". Clinical medicine & research 4 (3): 230–5. doi:10.3121/cmr.4.3.230. PMC 1570491. PMID 17048358.
- Vázquez JL, Vázquez I, González ML, García-Tejedor JL, Repáraz A (2007). "Pneumomediastinum and pneumothorax as presenting signs in severe Mycoplasma pneumoniae pneumonia". Pediatric Radiology 37 (12): 1286–8. doi:10.1007/s00247-007-0611-1. PMID 17899058.
- Hatzitolios A, Ntaios G (2007). "Spontaneous Pneumomediastinum May Be Associated with Both Anorexia Nervosa and Obesity". Lung 185 (6): 373. doi:10.1007/s00408-007-9037-7. PMID 17909893.
- Utsumi T, Shiono H, Fukai I, Akashi A (2007). "Artificial pneumomediastinum facilitates thoracoscopic surgery in anterior mediastinum". Interactive cardiovascular and thoracic surgery 6 (3): 411–2. doi:10.1510/icvts.2006.147355. PMID 17669882.
- Tetzlaff K, Reuter M (1998). "Recurrent pulmonary barotrauma (PBT) in a previously healthy male scuba diver who suffered from repeated pneumomediastinum after shallow-water scuba dives". Undersea Hyperb Med 25 (2): 127–8. PMID 9670439. Retrieved 2008-06-05.
- Dr. Richard Moon, Diver's Alert Network Vice President and Medical Director, http://www.diversalertnetwork.org/medical/articles/article.asp?articleid=40
- Jacobson FL, Loring SH, Ferrigno M (2006). "Pneumomediastinum after lung packing". Undersea Hyperb Med 33 (5): 313–6. PMID 17091828. Retrieved 2008-06-05.
- Nicol E, Davies G, Jayakumar P, Green ND (April 2007). "Pneumopericardium and pneumomediastinum in a passenger on a commercial flight". Aviat Space Environ Med 78 (4): 435–9. PMID 17484349. Retrieved 2008-06-05.
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