This is a prospective observational trial. The purpose of this study is to explore the feasibility of EIT monitoring pulmonary blood flow and the consistency and difference between EIT monitoring pulmonary local ventilation blood flow and SPECT and CTPA monitoring methods

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

Patients who need CTPA examination in the Department of nuclear medicine / radiology of Peking Union Medical College Hospital