Evaluation of pulmonary edema is a key factor in monitoring and guidance of therapy in acute respiratory distress syndrome (ARDS) patients. To date, methods available at the bedside for estimating the physiologic correlate of pulmonary edema, extravascular lung water(EVLW), often are unreliable or require invasive measurements. The purpose of the this study is to develop a novel approach to reliably assess extravascular lung water by electrical impedance tomography(EIT).

Inclusion Criteria:

Patients will be included in this study if the following criteria have been met:

1. Males and females > 18 years old and <85 years old (non-pregnant, non-lactating females).
2. Patients fulfilled the Berlin diagnostic criteria of ARDS
3. Signed written informed consent has been obtained
4. Patients had monitoring system Pulse-Induced Contour Cardiac Output (PiCCO)

Exclusion Criteria:

1. Females who are pregnant or lactating.
2. Patients with contraindication of EIT(Skin abrasions or wounds in the chest area.Patients with pacemakers or paced EKG rhythms.Thoracic deformity. Severe subcutaneous emphysema)
3. Patients <18 years old or > 85 years old
4. Patients Without monitoring system Pulse-Induced Contour Cardiac Output (PiCCO)
5. Patients with Cardiac function of grade 4 or patients with acute myocardial infarction or acute coronary syndrome

Adult ICU patients with ARDS will be enrolled between August 2016 and August 2017 when they fulfilled the inclusion criteria,and unfulfilled the exclusion criteria below