Electrical Impedance Tomography-Based Dynamic Ventilation-Perfusion Functional Phenotype Trajectory in Acute Respiratory Distress Syndrome

Design: Prospective, multicenter, observational cohort study * Setting: ≥2 tertiary ICUs equipped with EIT capability * Population: Adult patients with moderate-to-severe ARDS (Berlin definition, PaO₂/FiO₂ ≤ 200 mmHg) receiving mechanical ventilation * Intervention: Daily lung perfusion assessment using a 16-electrode EIT belt. Regional ventilation-perfusion (V/Q) ratios are calculated by combining tidal and pulsatile impedance changes. Phenotypes are classified as Matched V/Q, High V/Q (dead space), Low V/Q (shunt), or Globally Impaired V/Q. Trajectories are categorized as Stable, Improving, Deteriorating, or Fluctuating. * Endpoints: * Primary: Association between phenotype trajectory type and 28-day mortality * Secondary: Time to oxygenation improvement, duration of mechanical ventilation, ICU length of stay, interaction between trajectory and ventilator settings