A 25-year-old woman with a history of well controlled asthma, polycystic ovarian disease and bipolar disorder was admitted with shortness of breath. On admission she was afebrile, hypotensive, tachycardic and tachypnoeic with normal chest examination and normal chest x ray with a peak expiratory flow rate (PEFR) of 20% predicted value. She was treated for acute exacerbation of asthma with steroids and bronchodilators. Eight hours after admission, her PEFR was 10% of predicted and she was in refractory hypoxaemia. She was intubated and was on ventilator for respiratory failure. Two days after intubation, she had chest pain with normal electrocardiogram (ECG) and cardiac enzymes, but at that point her chest x ray (fig 1) revealed pneumomediastinum with extensive subcutaneous emphysema with no pulmonary infiltrates. The patient died within a day of this finding on the chest x ray, due to tension pneumomediastinum from post-intubation tracheobronchial rupture, which is a consequence of poor ventilation strategy with high peek end exploratory pressure (PEEP), plateau pressure of 35 and coexisting bad asthma.

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Figure 1 Chest x ray revealing pneumomediastinum with extensive subcutaneous emphysema (superimposed pulmonary infiltrate-like shadow is not in the lung, it is the air beneath the skin) with no pulmonary infiltrates.

Pneumomediastinum can dissect tissue planes causing pneumopericardium, pneumothorax, subcutaneous emphysema, pneumoperitoneum, or pneumoretroperitoneum. Typically the patient presents with severe substernal chest pain with or without radiation to the neck and arms. Usually no treatment is required, but the mediastinal air will be absorbed faster if the patient inspires high concentrations of oxygen. Tension pneumomediastinum can cause direct cardiac or airway compression leading to death. If mediastinal structures are compressed, the compression can be relieved with needle aspiration.1