Pulmonary edema.

The pathophysiology of pulmonary edema formation has been discussed under normal conditions and when pulmonary capillary endothelial (and possibly alveolar epithelial) permeability are increased. The potential anatomic sites for pulmonary edema formation and the clinical relevance of the various sites were discussed. The role of potential "safety factors"--including increased lung lymph flow, increased interstitial hydrostatic pressure, and decreased interstitial protein osmotic pressure--in cardiogenic and fluid overload versus increased permeability pulmonary edema, were addressed. The clinical usefulness of quantitating various variables including pulmonary vascular pressures and lung water were also briefly discussed. Pulmonary edema fluid contains potential mediators that may contribute to the severity and chronicity of the lung injury. It is hoped that the concepts explored here should eventually provide clinically relevant information to guide in the management of critically ill patients with pulmonary edema.