CTICasesPulmonary Interstitial Emphysema and Pneumomediastinum (Macklin Effect)
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Imaging findings
Bedside chest radiograph shows pneumomediastinum and extensive subcutaneous emphysema. High-resolution chest CT demonstrates interstitial emphysema, characterized by air tracking as linear, branching "lightning bolts" along the bronchovascular sheaths and within the intersegmental/intersublobar septa. Air is also visible in the subpleural space and along the interlobar fissures, tracking directly into the mediastinum.
Key takeaways
The Macklin effect describes the pathophysiology of pneumomediastinum resulting from alveolar rupture due to increased intra-alveolar pressure, often triggered by severe coughing, retching, or chemical inhalation. Ruptured alveolar air dissects proximally through the bronchovascular sheaths and pulmonary interstitium (pulmonary interstitial emphysema) to enter the mediastinum.
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