Noninvasive ventilation is commonly employed in patients with pneumonia or acute respiratory distress syndrome (ARDS) and has been shown to reduce the need for intubation and invasive mechanical ventilation. However, the rate of noninvasive ventilation failure remains substantial, at approximately 40%. Compared with patients in whom noninvasive ventilation succeeds, those who experience noninvasive ventilation failure have a higher likelihood of mortality during their intensive care unit or hospital stay. Therefore, improving the success rate of noninvasive ventilation is clinically important. In patients with lung consolidation receiving invasive mechanical ventilation, high positive end-expiratory pressure (PEEP) can improve oxygenation. Noninvasive ventilation operates on similar physiological principles and can also deliver high PEEP via a mask interface. Nevertheless, there is limited evidence regarding the use of high PEEP during mask-delivered noninvasive ventilation. This study aimed to evaluate whether high PEEP can increase intubation-free survival in patients with pneumonia or ARDS who are treated with noninvasive ventilation.

Inclusion Criteria:

• Age >18 years
• PaO2/FiO2 ≤300 mmHg or SpO2/FiO2 ≤315（SpO2 ≤97%)
• Anticipated NIV duration > 12 h
• Preserved consciousness (GCS≥13)

Exclusion Criteria:

• Use of NIV > 24 h before randomization
• Acute-on-chronic respiratory failure
• Congestive heart failure
• Use of NIV after extubation (within 48 hours)
• Contraindications to NIV (e.g., anatomical malformations, recent pulmonary/esophageal surgery [within 7 days])
• Pneumothorax
• NIV intolerance
• Refusal to participate
• Pregnancy
• Need for emergency intubation

These study data contain ethnic demographic information. Since it remains unclear whether Chinese laws permit the public disclosure of such data upon the completion of the research, a decision has been made to temporarily withhold data sharing during the study design phase.