Clinical Features, Treatments, and Outcomes in Acute Respiratory Distress Syndrome (ARDS-CTO)

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).