For moderate AECOPD(pH<7.35), several guidelines have strongly recommended NPPV as standard therapy, which can reduce the rate of intubation and mortality. A few previous studies have shown that HFNC can efficiently improve alveoli ventilation and breathing pattern in some severe AECOPD patients. Therefore, we hypothesize that HFNC is not inferior to NPPV for preventing endotracheal intubation in moderate AECOPD patients. To assess this hypothesis, we performed a multicenter, randomized, noninferiority trial of HFNV vs NPPV in moderate AECOPD patients.

Recently, many clinical studies have showed that HFNC can be successfully used in patients with hypoxemic respiratory failure to improve the comfort, to attenuate respiratory failure and to decrease the rate of tracheal intubation and mortality. Although theoretically HFNC is a potential and ideal treatment for AECOPD patients, the related clinical researches are very few. It still needs to further evaluate the safety and efficacy of HFNC in patients with AECOPD. For moderate AECOPD(pH<7.35), several guidelines have strongly recommended NPPV as standard therapy, which can reduce the rate of intubation and mortality. A few previous studies have shown that HFNC can efficiently improve alveoli ventilation and breathing pattern in some severe AECOPD patients. Therefore, we hypothesize that HFNC is not inferior to NPPV for preventing endotracheal intubation in moderate AECOPD patients. To assess this hypothesis, we performed a multicenter, randomized, noninferiority trial of HFNV vs NPPV in moderate AECOPD patients.

Inclusion Criteria:

• AECOPD; 7.35>pH≥7.25，PaCO2>50 mmHg

Exclusion Criteria:

• contraindications for NPPV, such as thick sputum, cough weakness, hemodynamic instability, etc.; need to be intubated immediately; refuse to engage in the study; severe organ dysfunction