The main oxygen therapy to the patients with acute exacerbation of Chronic obstructive pulmonary disease, who are mild to moderate respiratory insufficiency (arterial blood gas analysis showed pH = 7.35, PO2 < 60mmHg,PaCO2>45mmHg) or have achieved the traditional noninvasive ventilation support standard but can not tolerate or reject, was nasal catheter, venturi mask and other conventional oxygen therapy. All these inaccurate inhaled oxygen concentration methods with inadequate heating and humidifying lead to poor patient tolerance and adverse reactions such as airway secretions discharge disorders. The high flow nasal respiratory therapy (Nasal high flow, NHF) utilises higher gas flow rates than conventional low-flow oxygen systems. The devices used deliver heated and humidified oxygen at a flow of up to 60 litres per minute via nasal cannulas with low level continous positive airway pressure. This study is a prospective randomized study. AECOPD patients with no severe respiratory failure are treated with NHF and conventional oxygen therapy respectively. The target is that NHF can increase the comfort degree of patients,reduce the rate of endotracheal intubation, and shorten the time of hospitalization.

Inclusion Criteria:

• AECOPD patients.
• The results of blood gas analysis showed pH ≥7.35, PO2< 60mmHg, PaCO2> 45mmHg.

Exclusion Criteria:

• The study case has been incorporated into the hospital again.
• Refused to the NHF therapy.
• The Glasgow score < 8.
• Severe organ dysfunction (including liver and kidney dysfunction, decompensated acidosis, upper gastrointestinal bleeding, DIC, etc.)