Tension pneumomediastinum.

Tension pneumomediastinum is an infrequently diagnosed but potentially fatal condition. The collection of air under pressure in the mediastinum compromises venous return to the heart and compresses major bronchi, leading to sudden and profound cardiovascular collapse. Although its mechanism was elucidated in the 1940's, when tension pneumomediastinum was most commonly a complication of tuberculosis, the same mechanism explains its formation in neonates with respiratory distress and in patients ventilated with volume respirators. Awareness of this condition will lead to more frequent diagnosis, but, more important, will also lead to prompt mediastinotomy and relief of this rapidly fatal condition.