View source for Pneumomediastinum

==Background==
[[File:Body Cavities Frontal view labeled 2.jpg|thumb|The pericardial cavity in this image is labeled d and is part of the inferior mediastium. Here we can see its relation to the superior mediastinum a, the pleural cavities c, and the diaphragm e.]]
[[File:Gray968.png|thumb|A transverse section of the thorax, showing the contents of the middle and the posterior mediastinum.]]
*Also known as mediastinal emphysema
*Definition: presence of free air in the mediastinum
*Can be Spontaneous or secondary (to violation of aerodigestive tract)<ref name="Bakhos">Bakhos CT, Pupovac SS, Ata A, et al. Spontaneous pneumomediastinum: an extensive workup is not required. J Am Coll Surg. 2014 Oct;219(4):713-7. doi: 10.1016/j.jamcollsurg.2014.06.001.</ref>
*Spontaneous pneumomediastinum usually occurs due to sudden increase in intra-alveolar pressure causing alveolar rupture → air dissects into pulmonary interstitium and then into mediastinum, neck, or pericardium<ref name="Niehaus">Niehaus M, Rusgo A, Roth K, Jacoby JL. Retropharyngeal air and pneumomediastinum: a rare complication of influenza A and asthma in an adult. Am J Emerg Med. 2015 Jun 14. pii: S0735-6757(15)00495-7. doi: 10.1016/j.ajem.2015.06.020.</ref>
*Life threatening causes include [[esophageal rupture]] or [[tension pneumothorax]]

===Etiology<ref>Kouritas VK, et al. Pneumomediastinum. J Thorac Dis. 2015 Feb; 7(Suppl 1): S44–S49. doi: 10.3978/j.issn.2072-1439.2015.01.11</ref>===
====Primary (i.e. Spontaneous)====
*No identified cause
*Smoking or tobacco use
*Recreational drug inhalation ([[cocaine]], [[methamphetamine]], [[marijuana]])<ref name="Johnson">Johnson JN, Jones R, Wills BK. Spontaneous Pneumomediastinum. Western Journal of Emergency Medicine. 2008;9(4):217-218.</ref>

====Secondary====
*Intrinsic Lung and Airway
**[[Asthma]] / [[COPD]] (most common co-morbidity<ref name="Bakhos" />)
**Bronchiectasis
**Interstitial lung disease
**Lung cancer
**[[Foreign body in the airway]]
**[[Mycoplasma pneumoniae]] [[pneumonia]]
**[[Influenza]] A<ref name="Niehaus" />
*Iatrogenic
**Endoscopy, bronchoscopy, or colonoscopy
**[[Intubation]]
**Central venous access procedures
**Thoracostomy / VATS
**Chest or abdominal surgeries
*Traumatic
**[[Thoracic trauma]] (blunt or penetrating)
**[[Blast injury]]
**Environmental [[pulmonary barotrauma]] (e.g. [[Scuba diving emergencies|scuba diving]], [[Commercial in-flight medical emergencies|flight]])
*Other
**Excessive vomiting (i.e., [[Boerhaave syndrome]], [[anorexia nervosa]])
**[[Esophageal rupture]] (rare)
**[[Hydrocarbons|Hydrocarbon]] inhalation
**Bowel rupture or other cause of air in abdominal cavity (tracts up into the chest)
**[[Childbirth]]

==Clinical Features==
*[[Chest pain]]
*[[Dyspnea]]
*[[Subcutaneous emphysema]], especially of face, neck, and chest.<ref>Quresi SA, Tilyard A (2008). "Unusual Presentation of Spontaneous Mediastinum: A Case Report". ''Cases Journal'' 1:349. doi:10.1186/1757-1626-1-349</ref> 
*Voice change, [[cough]], [[stridor]]
*"Crunching" sound on auscultation during systole (Hamman's crunch)
*Severe cases (generally after trauma) may mimic [[cardiac tamponade]]<ref>Beg MH, Reyazuddin, Ansari MM (1988). "Traumatic tension Pneumomediastinum Mimicking Cardiac Tamponade".  ''Thorax'' 43:576-677. doi: 10.1136/thx.43.7.576.</ref><ref>Jennings S, Peeceeyen S, Horton M. Tension pneumomediastinum after blunt chest trauma. ANZ J Surg. 2015 Jan;85(1-2):90-1. doi: 10.1111/ans.12378.</ref>

==Differential Diagnosis==
{{Template:Chest Pain DDX}}

{{Thoracic trauma DDX}}

==Evaluation==
[[File:PMC3047855 12245 2010 205 Fig1 HTML.png|thumb|Pneumomediastinum from nasal insufflation of cocaine.]]
[[File:PneumoMediastinum2008.jpg|thumb|Traumatic pneumomediastinum and right sided pneumothorax with first rib fracture.]]
[[File:Pneumomediastinum-003.jpg|thumb|Pneumomediastinum with Angel wing sign]]
[[File:Subcutaneous emphysema chest cropped.jpg|thumb|Pneumomediastinum with subcutanous emphysema on CT.]]
*CT Chest (preferred diagnostic test)
*[[CXR]]
**AP/PA - Ring around right pulmonary artery, air along left heart border, air in upper chest/neck soft tissue
**Lateral - air along anterior heart border
**Lateral neck - may see mediastinal air in neck
**30% with spontaneous pneumomediastinum will have normal CXR<ref name="Bakhos" />

==Management==
*Supportive care<ref name="Johnson" />
**Pneumomediastinum typically reabsorbs over 1-2 weeks.
*Treat underlying cause, if identified

==Disposition==
===Primary (Spontaneous)===
*Benign and self-limited disease
*Generally does not require repeat imaging, and can be managed conservatively on an outpatient basis with follow up in 24 to 48 hours<ref name="Bakhos" /><ref>Fitzwater JW, Silva NN, Knight CG, et al. Management of spontaneous pneumomediastinum in children. J Pediatr Surg. 2015 Jun;50(6):983-6. doi: 10.1016/j.jpedsurg.2015.03.024.</ref><ref>Smith BA, Ferguson DB. Disposition of spontaneous pneumomediastinum. Am J Emerg Med. 1991 May;9(3):256-9.</ref>
*Recommend analgesia, rest, and avoidance of actions that increase pulmonary pressure (i.e. Valsalva maneuvers, etc)

===Secondary<ref>de Virgilio C, Kim DY. Pneumomediastinum Following Blunt Trauma: Are We Closer to Unlocking Its Significance? JAMA Surg. 2015 Jun 24. doi: 10.1001/jamasurg.2015.1146.</ref>===
*Most cases are benign, but a minority of cases require additional testing and intervention.
*Have lower threshold for additional testing and admission.

==See Also==
*[[Pneumothorax (main)]]
*[[Thoracic Trauma]]
*[[Mediastinitis]]

==External Links==

==References==
<references/>

[[Category:Pulmonary]]