To Select the Optimal Positive End-expiratory Pressure in Moderate and Severe Acute Respiratory Distress Syndrome Patients by Using:

1. the novel Non-invasive Electrical Impedance Tomography Guided Method
2. the Protective ventilation tool G5(MV)

1. To titrate PEEP guided by EIT. A global inhomogeneity (GI) index and regional compliance based on EIT were developed to quantify the tidal volume distribution within the lung. The aim of this study was to test the feasibility of optimizing PEEP with respect to ventilation homogeneity using the GI index and regional compliance.
2. To titrate PEEP with the Protective Ventilation Tool by G5(MV). The new generation of ventilator will deliver an optimal PEEP on ARDS patients based on their status automatically.

Inclusion Criteria:

1. ARDS patients
2. Transferred from FEMH emergency room or Ward into the medical intensive care unit.
3. Patients with invasive mechanical ventilation
4. Patient, agent or consent of families learn about and subjects were willing to sign the consent form.

Exclusion Criteria:

1. burning electric knife used
2. pacemaker used
3. Large area wound is used gauze to cover
4. Wound or burn injuries of the chest wall.
5. Patients included conditions are not met.

20-90 years old

no sharing plan, including what IPD are to be shared with other researchers