Subcutaneous emphysema refers to air or gas present in which location?

• A. In the subcutaneous layer of the skin
• B. In the pleural space
• C. In the pericardial sac
• D. In the abdominal cavity

Answer: (A)

Subcutaneous emphysema is the presence of air or gas in the subcutaneous tissue just beneath the skin. This occurs when air leaks from the lungs or airways and tracks into the chest wall and neck tissues, so the gas ends up in the subcutaneous layer. It’s distinct from air in other spaces: air in the pleural space causes a pneumothorax, air in the pericardial sac is pneumopericardium, and air in the abdominal cavity is pneumoperitoneum. Clinically, crepitus underneath the skin from the gas can often be felt or heard as you palpate the swollen area.