What initial step should be taken for mediastinal emphysema?

• A. Place diver on 100% O2
• B. Immediate recompression
• C. Administer broad-spectrum antibiotics
• D. Ignore if asymptomatic

Answer: (A)

Administering 100% oxygen is the first step because it speeds up the resorption of the nitrogen-rich gas that has entered the mediastinum after pulmonary barotrauma. By increasing the amount of oxygen breathed, the nitrogen partial pressure gradient drives nitrogen out of the trapped gas into the blood and then out through the lungs, reducing the size of the mediastinal emphysema and helping relieve symptoms. Oxygen also supports tissue oxygenation while the diver is evaluated.

Recompression is not the initial move unless there are signs of arterial gas embolism or significant decompression illness. Antibiotics aren’t indicated unless infection is suspected, and ignoring symptoms isn’t appropriate since mediastinal emphysema can progress or signal other injuries. After starting high‑flow oxygen, monitor the diver and arrange medical evaluation, with escalation to hyperbaric treatment if gas embolism symptoms develop.