High-intensity noninvasive positive pressure ventilation (NPPV), which can well improve the gas exchange and reduce the work of breathing of patients, is a new strategy targeted at maximally reducing arterial carbon dioxide. However, no definitive conclusions have been drawn to decide whether high-intensity NPPV is the best setting for treating patients with chronic hypercapnic COPD. For now, no unified method for setting up high-pressure NPPV has been established. Most of the trials utilized gradually increased inspiratory positive airway pressure depending on the patient's tolerance. However, from a respiratory physiology point of view, excessive inspiratory positive airway pressure may lead to lung hyperinflation, increased intrinsic positive end expiratory pressures, increased oxygen consumption, and ineffective work of breathing.Therefore, seeking a method to establish individualized high-intensity NPPV is of vital importance.

Inclusion Criteria:

Clinically stable with chronic hypercapnic COPD (baseline arterial carbon dioxide pressure (PaCO2) of 50 mmHg or higher, measured resting in a sitting position and breathing room air without having used NPPV for at least 1 hour)

Exclusion Criteria:

• other lung/pleural diseases or thoracic deformity
• severe heart failure (New York Heart Association class IV), severe dysrhythmia
• unstable angina, or malignant comorbidity
• obesity (BMI ≥ 35 kg/m²)
• severe obstructive sleep apnea syndrome