Measurement of extravascular lung water in the ICU

The accumulation of fluid in the interstitium and alveolar space is known as extravascular lung water (EVLW). EVLW is associated with increased morbidity and mortality in critically ill patients and is elevated in patients with cardiogenic pulmonary oedema, acute lung injury (ALI), and the acute respiratory distress syndrome (ARDS). Pulmonary oedema is a consequence of increased pulmonary capillary hydrostatic pressure and/or an increased capillary permeability. The quantity of pulmonary oedema fluid is dependent on the balance of fluid formation and clearance, and this contributes to the overall dynamic net lung fluid balance. Measurement of EVLW is therefore an indirect surrogate measurement of the alveolar epithelial and endothelial damage in ALI/ARDS. The single indicator transpulmonary thermodilution technique is an available bedside technique to measure EVLW.