Impact of PEEP Trials on Ventilation-Perfusion Matching in ARDS Patients

"The first phase of the study is an observational study that does not alter the clinical treatment plan.~The experimental group（Sample size of 48 cases） in the second phase of the study needs to receive a central venous injection of 10ml of 10% saline to demonstrate pulmonary blood flow, while the control group （Sample size of 48 cases）requires no intervention.~The experimental group select the optimal pulmonary blood flow PEEP By Electrical impedance tomography.Change in ventilation-perfusion ratio measured by EIT during PEEP trials from baseline to 30 minutes at each PEEP level (5, 10, 15 cmH2O).~The control group was selected Best PEEP according to the PEEP table ."