Background: Electrical impedance tomography (EIT)-guided PEEP titration has been shown to improve regional ventilation distribution, increase respiratory system compliance, and reduce mechanical power in patients with acute respiratory distress syndrome (ARDS), but its effect on mortality remains unproven. In patients with moderate-to-severe ARDS, prone positioning for 4 hours allows pulmonary ventilation and perfusion to reach a new steady state, with optimization of ventilation-perfusion (V/Q) matching and other pulmonary physiological parameters. However, whether dynamic PEEP titration guided by EIT at this time point can further optimize V/Q matching and other pulmonary physiological parameters compared with conventional methods has not been reported.
Objective: To investigate whether EIT-guided PEEP titration performed at 4 hours after prone positioning initiation can further optimize V/Q matching and other pulmonary physiological parameters in patients with moderate-to-severe ARDS undergoing prone positioning.
Methods: This is a prospective, single-center, randomized, open-label, parallel-controlled physiological study. A total of 40 patients with moderate-to-severe ARDS (Berlin definition, PaO₂/FiO₂ \< 150 mmHg) will be enrolled and randomized in a 1:1 ratio to either the EIT-guided group or the control group. PEEP intervention will be performed at 4 hours after prone positioning initiation (T1) in both groups: the EIT group receives EIT-guided PEEP titration, while the control group receives PEEP set according to the ARDSNet/PEEP-FiO₂ table. The primary outcome is V/Q matching percentage assessed by EIT at 18 hours of prone positioning (T2) and 6 hours after supine repositioning (T3). Secondary outcomes include respiratory mechanics, EIT-derived parameters (regional ventilation distribution, global inhomogeneity index, center of ventilation), oxygenation indices, echocardiographic measures of cardiac function, and clinical outcomes (28-day mortality, ventilator-free days, ICU length of stay, etc.).
Conclusion: This study will provide physiological evidence for early EIT-guided PEEP titration in patients with moderate-to-severe ARDS undergoing prone positioning, and will lay the foundation for future large-scale clinical trials.
Diagnosis of moderate-to-severe ARDS according to the Berlin definition, with a PaO₂/FiO₂ ratio < 150 mmHg on optimal mechanical ventilation.
Clinical decision has been made to place a central venous catheter (internal jugular or subclavian vein) for clinical management.
Pregnancy or postpartum state.
BMI > 35 kg/m².
Duration of invasive mechanical ventilation > 48 hours at enrollment.
Severe hemodynamic instability (mean arterial pressure < 65 mmHg on norepinephrine ≥ 0.5 μg/kg/min).
Parallel
EIT-Guided PEEP Titration Group
Other interventionPEEP titration is performed during mechanical ventilation to optimize respiratory mechanics and ventilation-perfusion matching in patients with ARDS.
ARDSNet/PEEP-FiO₂ Table
Other interventionPEEP will be set according to the ARDSNet/PEEP-FiO₂ table at 4 hours after prone positioning initiation (T1).
Ventilation-Perfusion (V/Q) Matching Percentage
V/Q matching percentage assessed by electrical impedance tomography (EIT) using the EIT Evaluation Tool (SDMI) V2.7.1. V/Q matching reflects the efficiency of pulmonary gas exchange and is calculated from regional ventilation and perfusion distribution maps.
Respiratory System Compliance
Respiratory system compliance (Crs) calculated as tidal volume divided by driving pressure (plateau pressure minus PEEP), measured under volume-controlled ventilation.
Driving Pressure
Driving pressure (DP) calculated as plateau pressure (Pplat) minus PEEP, measured under volume-controlled ventilation.
EIT-Derived Regional Ventilation Distribution
Regional ventilation distribution assessed by EIT, expressed as percentage of tidal impedance variation in four regions of interest (ROIs): ventral (ROI 1), mid-ventral (ROI 2), mid-dorsal (ROI 3), and dorsal (ROI 4), each corresponding to 25% of the anteroposterior diameter, Center of Ventilation (CoV), Global Inhomogeneity Index (GI), Shunt, Dead Space.
RVEDA/LVEDA
Right Ventricular End-Diastolic Area to Left Ventricular End-Diastolic Area Ratio
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XIE MIN
Lead sponsor
Tongji Hospital
Sponsor institution
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