Interstitial Emphysema Leading to Pneumomediastinum in a Bone Marrow Transplant Patient

Abstract

A 43-year-old male patient presented with acute respiratory failure requiring mechanical ventilation in the intensive care unit. He underwent an allogeneic bone marrow transplant for acute myeloid leukemia and developed bronchiolitis obliterans syndrome as chronic graft-versus-host disease. Computer tomography scans revealed symmetrical ground-glass opacities in peripheral and basilar regions of the lungs and interstitial emphysema with pneumomediastinum. An open-lung biopsy made immediately afterward demonstrated acute interstitial pneumonitis. Despite immunosuppressive therapy, the patient died.The tomographic scans depict in detail the mechanism of pneumomediastinum. When pressure gradient between alveoli and interstitium exceeds a critical level, alveoli rupture occurs and air enters into the interstitium, causing perivascular interstitial emphysema (Figure 1A, white arrows). The pleura remains intact and air dissects the bronchovascular sheath through the inferior pulmonary veins (Figures 1B and 1C, white arrows) into the anterior mediastinum following a lower pressure gradient (Figure 1D, red star). When mediastinal pressure increases above critical levels, being insufficient to relieve the pressure tension, the mediastinal parietal pleura can rupture, causing an associated pneumothorax (1, 2), which did not occur in this case.The pneumomediastinum could possibly be explained by two mechanisms: alveolar overdistension from dynamic hyperinflation and auto-positive end-expiratory pressure caused by airway obstruction secondary to bronchiolitis obliterans syndrome; or barotrauma caused by heterogeneous ventilation and regional overdistension in normal lung areas in a patient with acute interstitial pneumonitis, even in a setting where protective lung ventilation strategies were adopted.

Pneumomediastinum, subcutaneous emphysema, and pneumothorax after a pulmonary function testing in a patient with bleomycin-induced interstitial pneumonitis

“…In a case report of pneumomediastinum in a bone marrow transplant recipient, some HRCT findings were similar to those of the present case, although they were of lesser magnitude and there was no pneumothorax. (8) between the alveolus and the perivascular sheath of the adjacent septum. A very negative pressure in the interstitial space could therefore lead to alveolar rupture even without the occurrence of extreme positive alveolar pressures.…”