Answer: Pneumomediastinum from pneumothorax

Pneumomediastinum

Mediastinal air has multiple causes:

• Intrathoracic injury (e.g., Pneumothorax)
• Upper respiratory tract (e.g., Injury during intubation) 
• Digestive tract perforation (e.g., Boerhaave’s syndrome)
• Intra-abdominal perforation (e.g., EGD complication)
• Anaerobic infection at sites communicating with mediastinum
  • Ludwig’s angina
  • Pneumoperitoneum
  • Bacterial mediastinitis

Listen for Hamman's sign ("crunching" with cardiac auscultation) and feel for crepitus (distinct feeling on palpation).

Treat the precipitating cause.

Usually resolves without mediastinal decompression; air travels along tissue planes decompressing increased mediastinal pressure.