Subcutaneous emphysema

The abnormal presence of air or gas within the subcutaneous tissues, most commonly of the neck and chest wall. Typically arising from airway trauma, barotrauma (mechanical ventilator, scuba diving), pneumothorax, pneumomediastinum, gas-forming infection (gas gangrene, necrotizing fasciitis), or iatrogenic injury (dislodging chest tube, surgery, endoscopy).