When evaluating mediastinal emphysema, which condition must be ruled out?

• A. Asthma
• B. Acute coronary syndrome
• C. Arterial gas embolism
• D. Angina

Answer: (C)

Arterial gas embolism is the critical condition to consider when mediastinal emphysema is present, especially in divers. Pulmonary barotrauma from diving can rupture alveoli and allow air to enter the pulmonary venous circulation, with bubbles traveling into the arterial system. These bubbles can travel to the brain, heart, or spinal cord, causing serious neurologic or ischemic injury, making AGE an immediate emergency. Because of this risk, the evaluation and management focus on identifying AGE quickly and initiating high-flow oxygen therapy and hyperbaric treatment as needed. Other possibilities like asthma or chest-pain syndromes (acute coronary syndrome or angina) don’t explain mediastinal air and don’t carry the same urgent risk of systemic arterial gas embolism, so AGE is the key condition to rule out.