The clinical assessment of lung water.

T he importance of the balance of lung fluid and pulmonary edema in experimental and clinical medicine explains the effort made in the last 30 years to measure lung water content and to develop clinically applicable methods. Pulmonary edema is an essential component ofthe spectrum oflung reactions to injury. As defined by the Starling equation,’ damage to the endothelium increases the permeability of the capillary membrane to water and solutes (protein) and represents the pathophysiologic basis of increasedpermeability edema (or noncardiogenic edema). An increase in pulmonary capillary pressure (due, for instance, to left ventricular failure) determines the accumulation of lung water by increasing the hydrostatic pressure gradient between capillary and interstitium and explains the pathogenesis of highpressure (cardiogenic or hemodynamic) pulmonary edema. The alveolar epithelium may play an important role in the development and resolution of alveolar 1 Both the high-pressure type and the increased-permeability type of pulmonary edema have been extensively studied in experimental animals. In experimental pulmonary edema, measurements of lung water by various methods have provided essential information on the magnitude, distribution, and temporal course of the accumulation of water. Pulmonary edema is also a common clinical event in various areas of medicine (as exemplified by the high-pressure lung edema of cardiac patients and the increased-permeability lung edema of patients with the adult respiratory distress syndrome); however, the clinical value of measurements of lung water remains controversial, mainly because all of the available methods have limitations which reduce their sensitivity and accuracy or restrict their spectrum of applications. The purpose ofthis review is to analyze the methods