[Abdominal free air without signs of perforated abdominal viscus during non-invasive ventilation]

A 19-year-old patient suffering from Duchenne muscular dystrophy was admitted to our hospital with an acute bronchopulmonary infection. Four months ago noninvasive ventilation was started because of hypercapnic respiratory failure. Mechanical ventilation had been used so far only at night. At the time of admission spontaneous breathing was not possible due to exhaustion of the respiratory muscles. The patient suffered from fever, limited cough strength and dyspnoea at rest. The abdomen was distended because of intestinal gas without clinical signs of acute abdomen.

Blood gas analysis showed respiratory acidosis even under mechanical ventilation. Laboratory tests showed an elevation of the inflammation indicating parameters. X-rays of the chest showed elevated diaphragms. Within the next days pneumonia could be seen in the left lower lobe. The patient had to be under mechanical ventilation almost 24 hours per day. Hypercapnia and respiratory acidosis normalized and the patient was able to breathe spontaneously for longer periods. The following days cutaneous emphysema developed and X-rays revealed free abdominal air on day 9 of the hospital stay.

The radiological findings have been confirmed during follow up X-rays without any clinical correlate. Inflammatory markers were decreasing. After the pneumonia had healed almost completely, the times on mechanical ventilation could be reduced. Subphrenic air resolved completely without any intervention.

Free subphrenic air without any clinical signs of acute abdomen does not necessarily force a surgical exploration. Under frequent follow up investigations a wait-and-see strategy could be justified. An explanation for the subphrenic air could be an interstitial emphysema due to increased intrathoracic pressure caused by the prolonged noninvasive ventilation, releasing the air through the diaphragmatic gaps into the abdomen.