UMEM Educational Pearls

The Macklin Effect

Pneumomediastinum (click here for image) may be caused by many things:

  1. Esophageal perforation (e.g., complication from EGD)
  2. Tracheal / Bronchial injury (e.g., trauma, complication of bronchoscopy, etc.)
  3. Abdominal viscus perforation with translocation of air across the diaphragmatic hiatus
  4. Air may reach mediastinum along the fascial planes of the neck.
  5. Alveolar rupture, also known as the "Macklin Effect"

The "Macklin Effect" is typically a self-limiting condition leading to spontaneous pneumomediastinum and massive subcutaneous emphysema after the following:

  1. Alveolar rupture from increased alveolar pressure (e.g., asthma, blunt trauma, positive pressure ventilation, etc.)
  2. Air released from alveoli dissects along broncho-vascular sheaths and enters mediastinum
  3. Air may subsequently track elsewhere (e.g., cervical subcutaneous tissues, face, epidural space, peritoneum, etc.)

Pneumomediastinum secondary to the Macklin effect frequently leads to an extensive workup to search for other causes of mediastinal air. Although, no consensus exists regarding the appropriate workup, the patient's history should guide the workup to avoid unnecessary imaging, needless dietary restriction, unjustified antibiotic administration, and prolonged hospitalization.

Treatment of spontaneous pneumomediastinum includes:

  • Supplemental oxygen and observation for airway obstruction secondary to air expansion within the neck
  • Avoiding positive airway pressure, if possible
  • Avoiding routine chest tubes (unless significant pneumothorax is present)
  • Administering prophylactic antibiotics are typically unnecessary
  • Ordering imaging as needed


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