This study aims to investigate the effects of high-intensity noninvasive positive pressure ventilation (NPPV), as compared with low-intensity NPPV, on hypercapnia, consciousness, inspiratory muscle effort, dyspnea, NPPV tolerance, inflammatory response, adverse events and other outcomes in patients with acute exacerbation of chronic obstructive pulmonary disease.

Inclusion Criteria:

1. Diagnosis of COPD according to the criteria of the Global Initiative for Chronic Obstructive Lung Disease in 2019
2. Presence of acute exacerbation
3. Arterial pH <7.35 with arterial carbon dioxide tension (PaCO2) >45 mmHg on room air or supplemental oxygen
4. PaCO2 >45 mmHg following low-intensity NPPV of ≥6 hours

Exclusion Criteria:

1. Age <18 years
2. Excessive amount of respiratory secretions or weak cough
3. Upper airway obstruction
4. Recent oral, facial, or cranial trauma or surgery; recent gastric or esophageal surgery
5. Potential risk factors for restrictive ventilatory dysfunction (eg, consolidation or removal of at least one pulmonary lobe, massive pleural effusion, chest wall deformity, continuous strapping with thoracic or abdominal bandage, and severe abdominal distention)
6. Active upper gastrointestinal bleeding
7. Cardiac or respiratory arrest
8. Arterial oxygen tension/fraction of inspired oxygen <100 mmHg
9. Pneumothorax
10. Severe ventricular arrhythmia or myocardial ischemia
11. Severe hemodynamic instability despite fluid repletion and use of vasoactive agents
12. Severe metabolic acidosis
13. Refusal to receive NPPV
14. Endotracheal intubation already performed before ICU admission