High-flow nasal cannula oxygen therapy(HFNC) has proved no significant difference compared with noninvasive positive pressure ventilation (NPPV) in preventing postextubation respiratory failure and reintubation in patients with acute hypoxemic respiratory failure.However, the efficacy of early postextubation sequential HFNC in COPD patients with hypercapnic respiratory failure is inconclusive.

The investigators conducted this prospective randomized controlled trial to explore the efficacy, safety of HFNC versus NPPV after early extubation in COPD patients with hypercapnic respiratory failure.The investigators hypothesized that the efficacy of HFNC after early extubation is non-inferior to that of NPPV.

Inclusion Criteria:

• 1. COPD patients with bronchopulmonary infection 2. Patients with hypercapnia respiratory failure treated with invasive mechanical 3.14 days ≥ invasive mechanical ventilation ≥ 48 hours; 4.Reached the pulmonary infection control (PIC) window; 5.Have self-care ability with oxygen supply during stable phrase

Exclusion Criteria:

• Severe organ dysfunction;Myopathy or myasthenia gravis;Upper airway obstruction;A large amount of secretions and inability to drain;