Pneumomediastinum in pulmonary fibrosis. Detection by computed tomography.

Pneumomediastinum was found in 5 of 34 patients (14.7 percent) with pulmonary fibrosis on computed tomographic (CT) scan of the chest. Small collection of air was seen in the retrosternal space in two patients, preaortic space in one patient, pretracheal space in two, subcarinal space in three, at the hilum in one, and perivertebral space in three patients. Concomitant pneumothorax was noted in two patients, both on the left side. Patients showed either honeycombing on CT (four patients) or presented with violent cough (four patients). Pneumomediastinum seen in these patients was thought to be the result of rupture of alveoli or honeycomb cysts due to raised intrapulmonary pressure on coughing, and subsequent tracking of air along the vascular sheath and accumulation in the mediastinum.