EIT-Guided PEEP Optimization in Trauma and Postoperative ARDS

Inclusion Criteria: * Mechanically ventilated surgical intensive care patients with trauma- or postoperative-associated moderate to severe ARDS, as defined by the 2023 Global Definition of ARDS. Exclusion Criteria: * Age \<18 or \>90 years. * Severe acute brain injury or acute stroke with Glasgow Coma Scale \<8. * Thoracic trauma with pneumothorax or pneumomediastinum. * End-stage diseases under palliative care (e.g., metastatic cancer, cirrhosis, end-stage renal disease). * Severe multiorgan failure with expected survival \<7 days. * Conditions requiring prolonged mechanical ventilation (e.g., Guillain-Barré syndrome, cervical spinal cord injury). * Contraindications to hypercapnia (e.g., elevated intracranial pressure, acute coronary syndrome). * Prior use of advanced respiratory therapies (e.g., ECMO, inhaled nitric oxide, prone positioning, high-frequency ventilation). * Pregnancy, breastfeeding, or skin lesions at electrode placement sites. * Implanted electrical devices interfering with EIT (e.g., pacemaker, ICD). * Known allergy to electrode materials. * Refusal to participate or concurrent enrollment in another study