Efficacy Evaluation of Lung Recruitment After Endotracheal Suctioning on Regional Lung Ventilation in Patients with ARDS: a Prospective Randomized Crossover Study

INTERVENTION: Sequence A Group:First phase: Lung recruitment maneuver (RM) after suctioning; Second phase: Suctioning only;Sequence B Group:First phase: Suctioning only; Second phase: Lung recruitment maneuver (RM) after suctioning; CONDITION: Acute respiratory distress syndrome (ARDS) is a common critical illness in clinical practice, with an incidence rate exceeding 10% in intensive care units and an overall mortality rate of approximately 40%. Its core pathological features include alveolar collapse, significant reduction in lung volume, severe ventilation‐perfusion mismatch, and consequently profound hypoxemia. PRIMARY OUTCOME: Percentage change in end‐expiratory lung impedance (?EELI%); SECONDARY OUTCOME: Percentage change in end‐expiratory lung impedance (?EELI%);Regional parameters: ventral‐to‐dorsal ?EELI% ratio; global inhomogeneity inde X(GI);Physiological parameters: changes in HR, MAP, and SpO2 relative to baseline (T0); change in PaO2/FiO2 at T5 relative to T0;Incidence of clinical recruitment response; INCLUSION CRITERIA: 1. Age >= 18 years; 2. Meets the Berlin criteria for moderate‐to‐severe ARDS (PaO2/FiO2 <= 200 mmHg, with PEEP >= 5 cm^2); 3. Currently undergoing invasive mechanical ventilation (via oro/nasal endotracheal intubation or tracheostomy); 4. Presence of clinical indications for secretion suctioning; 5. No contraindications to EIT monitoring (no electronic implantable devices, intact chest skin); 6. Written informed consent signed by the legally authorized representative.