Typical Cause of Pneumomediastinum
The most common cause of pneumomediastinum is alveolar rupture due to increased intra-alveolar pressure, which allows air to dissect along vascular sheaths and connective tissue planes into the mediastinum 1, 2.
Etiology Framework
Pneumomediastinum can be categorized into three main types based on mechanism:
1. Spontaneous Pneumomediastinum (Most Common Overall)
- Occurs from rupture of marginal pulmonary alveoli when intra-alveolar pressure suddenly increases 1
- Typically affects healthy young men (average age 26.3 years, predominantly male) 2
- Risk factors include:
2. Traumatic Pneumomediastinum (Second Most Common)
- In trauma settings, post-traumatic pneumomediastinum occurs from blunt chest trauma causing alveolar rupture or tracheal/airway injury 4
- Blunt trauma mechanisms include:
- Rib fractures lacerating visceral pleura
- Increased alveolar pressure causing alveolar rupture 4
- Penetrating trauma can directly injure airways or esophagus 1
3. Secondary/Iatrogenic Causes (Less Common)
- Esophageal perforation (Boerhaave's syndrome) 5, 2
- Dental procedures and head/neck surgery 6
- Tracheal or bronchial rupture 1
- Hollow viscus perforation 7, 3
Important Clinical Context
The pathophysiology follows the Macklin effect: air dissects from ruptured alveoli along bronchovascular sheaths toward the mediastinum, then can extend to subcutaneous tissues of the neck, face, and chest wall 8, 3.
Common Pitfalls to Avoid:
- Don't assume trauma is always present—spontaneous pneumomediastinum is actually more frequent than traumatic in general populations 1, 7
- In COVID-19 patients, pneumomediastinum occurs without exogenous injury due to severe alveolar damage 8
- Iatrogenic causes (dental work, intubation) are often overlooked in the history 6
In summary: While trauma is a significant cause in emergency settings 4, spontaneous alveolar rupture from increased intra-alveolar pressure remains the overall most common etiology across all patient populations 1, 2.