Stress failure of pulmonary capillaries in the intensive care setting.

Recent work shows that when the pressure in pulmonary capillaries is raised to high levels, ultrastructural changes occur in their walls including disruption of the capillary endothelium, alveolar epithelium, or sometimes all layers. Since the calculated wall stresses are extremely high, this condition is referred to as stress failure, and it results in a high permeability type of pulmonary edema, or even frank hemorrhage. Stress failure is believed to play a part in diseases where the capillary pressure is abnormally high, such as neurogenic pulmonary edema, high altitude pulmonary edema, exercise-induced pulmonary hemorrhage in racehorses, and perhaps some cases of the adult respiratory distress syndrome. Stress failure also occurs if the blood-gas barrier is weakened as in Goodpasture's syndrome. Another important cause is overinflation of the lung as may occur with mechanical ventilation and high inflation pressures. Stress failure of pulmonary capillaries is a hitherto overlooked and potentially important factor in the intensive care setting.