RESET-COPD Cohort: Real-Time Monitoring and Early Warning in COPD Patients Receiving Home NPPV

Inclusion Criteria: * Age 18 years or older. * Diagnosis of COPD according to GOLD 2026 criteria, with post-bronchodilator FEV1/FVC \< 0.70. * Severe airflow limitation, defined as FEV1 \< 50% of predicted value, corresponding to GOLD grade III-IV. * Chronic hypercapnia, defined as arterial PaCO₂ ≥ 52 mmHg (approximately 7.0 kPa) in a clinically stable state (no acute exacerbation of COPD within at least 4 weeks before enrollment), with arterial blood gas analysis performed in the sitting position at rest and after discontinuation of NPPV for at least 2 hours. Exclusion Criteria: * Chronic respiratory failure caused by diseases other than COPD, including neuromuscular diseases, chest wall deformity, obstructive sleep apnea, or severe obesity with BMI \> 35 kg/m². * Severe cardiovascular disease, including NYHA class IV heart failure or unstable angina. * Severe renal disease receiving long-term renal replacement therapy. * Expected survival of less than 1 year, including active malignancy or end-stage systemic disease. * Inability to complete the study, including cognitive impairment, psychiatric disease, inability to cooperate with NPPV, inability to use wearable devices, or inability to complete follow-up. * Refusal to participate in the study or refusal to sign informed consent.