• Also known as mediastinal emphysema
  • Definition: presence of free air in the mediastinum
  • Can be Spontaneous or secondary (to violation of aerodigestive tract)[1]
  • 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[2]
  • Life threatening causes include esophageal rupture or tension pneumothorax

Primary (i.e. Spontaneous)

  • No identified cause
  • Smoking or tobacco use
  • Recreational drug inhalation (cocaine, methamphetamine, marijuana)[4]


Clinical Features

  • Chest pain
  • Dyspnea
  • Subcutaneous emphysema, especially of face, neck, and chest.[5]
  • Voice change, cough, stridor
  • "Crunching" sound on auscultation during systole (Hamman's crunch)
  • Severe cases (generally after trauma) may mimic cardiac tamponade[6][7]

Differential Diagnosis

Chest pain




Thoracic Trauma


  • 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[1]


  • Supportive care[4]
    • Pneumomediastinum typically reabsorbs over 1-2 weeks.
  • Treat underlying cause, if identified


Primary (Spontaneous)

  • Benign and self-limited disease
  • Generally does not require repeat imaging, and can be managed conservatively on an outpatient basis[1][8][9]


  • Most cases are benign, but a minority of cases require additional testing and intervention.
  • Have lower threshold for additional testing and admission.

See Also


  1. 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.
  2. 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.
  3. 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
  4. Johnson JN, Jones R, Wills BK. Spontaneous Pneumomediastinum. Western Journal of Emergency Medicine. 2008;9(4):217-218.
  5. Quresi SA, Tilyard A (2008). "Unusual Presentation of Spontaneous Mediastinum: A Case Report". Cases Journal 1:349. doi:10.1186/1757-1626-1-349
  6. Beg MH, Reyazuddin, Ansari MM (1988). "Traumatic tension Pneumomediastinum Mimicking Cardiac Tamponade". Thorax 43:576-677. doi: 10.1136/thx.43.7.576.
  7. 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.
  8. 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.
  9. Smith BA, Ferguson DB. Disposition of spontaneous pneumomediastinum. Am J Emerg Med. 1991 May;9(3):256-9.
  10. 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.
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