A 25-year-old woman presented to the emergency department with lethargy, weakness, dyspnoea, nausea and vomiting for 1 week. On examination she was lethargic with a blood pressure of 108/59 mm Hg, pulse of 126/min, respiration of 28/min and temperature of 95.3°F (35.2°C). She had dry oral mucosa, decreased skin turgor with fullness and palpable crepitations at the thoraco-cervical junction. Hamman’s sign, however, could not be appreciated.

Significant laboratory data included blood glucose 732 mg/dl; K⁺ 2.9 mmol/l, anion gap of 35; leucocyte count 29300 cells/μl with 8% bands. Arterial blood gas analysis showed a pH of 6.8, pCO₂ of 12 mm Hg, pO₂ of 181 mm Hg, bicarbonate of 1.6 mmol/l, and O₂ saturation of 98%. Serum ketones were reported as “large” and urine ketones were >80 mg/dl.

Chest radiograph showed thin radiolucent line along left heart border (fig 1A: arrows) and chest computed tomography (CT) scan showed air in tissue planes of mediastinum (fig 1B: arrows). Gastrograffin oesophagogram was negative for oesophageal rupture/leak. A diagnosis of diabetic ketoacidosis (DKA) with pneumomediastinum was made. Endotracheal intubation was performed for respiratory distress and the patient was treated with intravenous insulin, fluids, potassium and antibiotics. Following successful recovery she was discharged home.

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Figure 1

Chest radiograph (panel A), showing thin radiolucent line along the left heart border (white arrows), and chest computed tomography (panel B), showing presence of air in the mediastinal soft tissue planes (black arrows).

Pneumomediastinum is a rare pulmonary complication of DKA but its incidence is largely unknown.1 Kussmaul breathing and repeated vomiting increase the intra-alveolar pressure leading to alveolar rupture, with air dissecting along the peribronchovascular sheath into the mediastinum with possible extension into neck and subcutaneous tissue.

Patients usually present with chest pain and dyspnoea. Treatment is mostly supportive but patients should be carefully monitored in intensive care settings. Aggressive management of nausea/vomiting along with correction of acidosis to break Kussmaul breathing is warranted. Pneumomediastinum also raises concerns about Boerhaave’s syndrome which can be ruled out by gastrograffin oesophagogram. However, associated pneumopericardium, pneumothorax and/or pneumorrhachis can be life threatening.2