The Study of Regional Lung Ventilation-perfusion by EIT

Inclusion Criteria: 1. Admission to ICU was less than 72 hours; 2. Age ≥ 18 years old and ≤ 80 years old; 3. Volunteer to participate after communicating with patients' family members; Exclusion Criteria: 1. The patients with heart implants could not be monitored by EIT; 2. Patients or their families refused to participate in the study; 3. Hypernatremia