Clinical Research Directory

Inclusion Criteria: * Age ≥ 18 years. * Receiving respiratory support with one of the following: * High-flow nasal oxygen (HFNO) at a flow rate ≥ 30 L/min, * Noninvasive ventilation (NIV) with positive end-expiratory pressure (PEEP) of ≥ 5 cm H₂O, or * Invasive mechanical ventilation with PEEP of ≥ 5 cm H₂O. * Within 48 hours before or after eligibility screening, the following criteria must be met: * PaO₂/FiO₂ ≤ 300 mmHg under the above respiratory support. * Bilateral opacities on chest radiograph or computed tomography, not fully explained by effusions, lobar/lung collapse (atelectasis), or pulmonary nodules/masses. * Respiratory failure not fully explained by cardiac failure or fluid overload; when no clear ARDS risk factor is identified, an objective assessment (e.g., echocardiography) is required to exclude hydrostatic edema. Exclusion Criteria: * Refusal of informed consent by the patient or a legally authorized representative. * Chronic respiratory failure, defined as: * Patients receiving long-term oxygen therapy or home mechanical ventilation (except for CPAP used solely for obstructive sleep apnea), or * Outpatients with PaCO₂ \> 60 mmHg. * Diffuse alveolar hemorrhage. * Interstitial lung disease. * Moribund patients expected to survive \< 24 hours. * Patients expected to require high-flow nasal oxygen or mechanical ventilation for \< 48 hours. * Patients with a decision to withhold life-sustaining treatment (except those for whom full support is provided other than cardiopulmonary resuscitation).