Although the theoretical model of "cyclic on-off switching of pulmonary blood flow" provides a crucial perspective for understanding VILI, its clinical validation and real-time intervention face significant obstacles. The fundamental reason lies in the lack of pulmonary microcirculation monitoring technology capable of bedside, non-invasive, continuous operation with sufficient spatiotemporal resolution. Nowadays, a novel 3D-EIT can perform real-time and non-invasive assessment of the distribution of pulmonary blood flow. However, if 3D-EIT can help to identify "cyclic on-off switching of pulmonary blood flow" is still unclear.

Inclusion Criteria:

1. Adult patients with mechanical ventilation
2. diagnosis of moderate to severe ARDS no more than 72 hours

Exclusion Criteria:

1. Chronic respiratory diseases that required long-term oxygen therapy, such as pulmonary fibrosis or chronical obstructive pulmonary disease
2. Contraindications to EIT (e.g., active implantable device, chest malformation, unstable spinal injuries or fractures, and open chest wounds)
3. Undrained pneumothorax or pneumomediastinum,
4. Hemodynamic instability
5. Pregnancy
6. Refusal by family or the attending physician to participate in the study.

Consecutive adult patients admitted to our ICU were screened for inclusion and exclusion criteria