Clinical Utility of Extravascular Lung Water Measurements

In physiological conditions, the hydrostatic pressure of the pulmonary microvessels induces the transfer of a certain amount of fluid into the interstitial space. The lymphatic system drains this large amount of fluid toward the thoracic duct, avoiding alveolar edema. Thus, in physiology, the extravascular lung water (EVLW) is the volume of fluid that has been filtered from the vessels and that has been eliminated by lymphatic drainage. In physiological conditions, this volume is low, less than 7 ml/ kg of body weight.