Abstract: The change of Extravascular Lung Water can quantitatively reflect the existence and severity of early pulmonary edema for the patients with ARDS,it is significant correlation with the prognosis and good for early diagnosis and making treatment guidline for ASDS. Pulmonary Vascular Permeability Index can indicate pulmonary vascular permeability directly which can be used to identify the reasons of pulmonary edema and reflect the injury severity of lung and to judge the prognosis of ARDS patients.

Key words: Key words:ARDS, extravascular lung water, Pulmonary vascular permeability