Noncardiogenic pulmonary edema.

Pulmonary edema is a consequence of high pressures in the pulmonary microcirculation (predominantly capillaries) or an increase in the permeability of the alveolar-capillary barrier (generally of its endothelial aspect) or a combination of both. It occurs when the rate of transudation from the capillaries exceeds the rate of lymphatic drainage from the interstitium. If the plasma oncotic pressure is low due to hypoproteinemia, transudation of fluid occurs at lower pressures. Permeability pulmonary edema is strongly influenced by fluctuations in pulmonary capillary pressures: an increase in pulmonary capillary pressure can add a large component of hemodynamic pulmonary edema to that originating in leaky vessels. Noncardiogenic forms of pulmonary edema are described.