This condition is literally defined as “air within the mediastinum”
The mediastinum is the space between the two lungs where the windpipe, gullet, blood vessels and nerves pass through the chest.
The cause is usually traumatic/impact (the most recent case we saw happened when a dog ran in to a tree) but infections and tumours can also be implicated. A penetrating injury, gullet perforation (from a sharp bone) or windpipe rupture (road accident) can lead to a pneumomediastinum. They all cause air to escape and collect in the mediastinum.
Diagnosis is suspected on history and clinical symptoms but needs to be confirmed by x-ray. Clinical symptoms are air under the skin around the neck, difficulty in breathing and a purple colour in the gums (cyanosis). If the gullet is involved then difficulty in eating is observed. When we x-ray the air in the mediastinum acts as a positive contrast meaning that structures not normally seen on x-ray are easily visible.
Normal Chest X-ray
For a condition which has such a dramatic onset the prognosis is surprisingly good. Most cases will resolve spontaneously but complications can occasionally occur and sometimes surgical intervention is required. Spontaneous recovery will occur in about 2 – 21 days as the air is reabsorbed and the underlying cause is dealt with by nature.