Pneumomediastinum
Basics
Description
Description
- Presence of free air or gas within the mediastinum (mediastinal emphysema)
- May originate from esophagus, alveolar, or bronchial tree (aerodigestive process)
- May occur spontaneously (primary pneumomediastinum) or as result of trauma, surgery, or other pathologic processes (secondary pneumomediastinum)
- Spontaneous pneumomediastinum:
- Caused by extrapleural tracheobronchial injury:
- Increased intra-alveolar pressure, low perivascular pressures, or both
- Terminal alveolar rupture into the lung interstitium and bronchovascular tissue sheath
- Dissection of air into the hilum and subsequently the mediastinum along a pressure gradient
- Mediastinal air then dissects into the fascial planes, most commonly into the tissues of the neck
- Often in setting of a Valsalva maneuver, forceful vomiting, in association with bronchospasm (i.e., asthma exacerbations) or inhalational drug use
- Men > women (2:1 in some series)
- Young > old (most common in second/third decades of life in most series)
- Rare in pediatric patients, but with a bimodal age distribution of peak incidence (<7 and 13–17 yr)
- Caused by extrapleural tracheobronchial injury:
- Relatively rare, 1/30,000–50,000 hospital admissions
Etiology
Etiology
- Primary or spontaneous pneumomediastinum:
- Associated with forced Valsalva maneuvers:
- Forceful vomiting
- Forceful straining during exercise
- Straining during defecation
- Coughing/sneezing
- Intense screaming
- Labor and delivery
- Playing wind instruments
- Pulmonary function testing
- Anorexia nervosa
- Obesity
- Pre-existing lung disorders (interstitial lung disease, pulmonary fibrosis, pneumonitis)
- Illicit inhalation drug use (marijuana, cocaine, methamphetamine)
- Tobacco abuse
- Rapid ascent in scuba divers
- A majority of cases will have no identified precipitating event/cause
- Has been rarely described after dental extraction/procedures
- Associated with forced Valsalva maneuvers:
- Secondary pneumomediastinum:
- Secondary to thoracic barotrauma
- Blunt trauma is the most common mechanism
- Common traumatic mechanisms:
- Motor vehicle collision
- Fall
- Blows to chest or neck
- Open facial/neck injury
- Recent esophageal/tracheobronchial instrumentation/endoscopy
- Positive-pressure mechanical ventilation
- Esophageal rupture (Boerhaave syndrome)
- In association with mediastinal infection caused by gas-forming organisms
- Tension pneumomediastinum:
- Rare but life-threatening event
- Usually in patients on positive-pressure ventilation
- May be associated with pneumopericardium and/or extension of a pneumothorax/tension pneumothorax
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Citation
Schaider, Jeffrey J., et al., editors. "Pneumomediastinum." 5-Minute Emergency Consult, 6th ed., Lippincott Williams & Wilkins, 2020. Emergency Central, emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307382/all/Pneumomediastinum.
Pneumomediastinum. In: Schaider JJJ, Barkin RMR, Hayden SRS, et al, eds. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307382/all/Pneumomediastinum. Accessed December 3, 2024.
Pneumomediastinum. (2020). In Schaider, J. J., Barkin, R. M., Hayden, S. R., Wolfe, R. E., Barkin, A. Z., Shayne, P., & Rosen, P. (Eds.), 5-Minute Emergency Consult (6th ed.). Lippincott Williams & Wilkins. https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307382/all/Pneumomediastinum
Pneumomediastinum [Internet]. In: Schaider JJJ, Barkin RMR, Hayden SRS, Wolfe RER, Barkin AZA, Shayne PP, Rosen PP, editors. 5-Minute Emergency Consult. Lippincott Williams & Wilkins; 2020. [cited 2024 December 03]. Available from: https://emergency.unboundmedicine.com/emergency/view/5-Minute_Emergency_Consult/307382/all/Pneumomediastinum.
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