2.1. Inclusion criteria for study selection

We will only choose randomized controlled trials (RCTs); other study designs, including non-randomized controlled trials, will be excluded.

All participants were adults (aged >18 years) meeting the following criteria:

diagnosis of COPD according to the COPD clinical guidelines;

experiencing AECOPD;

according to blood gas analysis, pH < 7.35 and partial pressure of arterial CO₂ (PaCO₂) >50 mm Hg;

unobstructed respiratory tract, adequate strength for spontaneous breathing, and absence of pneumothorax, pneumomediastinum, and lung bullae;

no facial deformity or facial triangle infection;

no severe cardiac, hepatic, or renal insufficiency, and no hemodynamic instability;

no malignant tumor or severe brain disease; and

conscious with no mental illness.

All participants will receive standard treatment, including bronchodilators, glucocorticoids, antibiotics, low flow oxygen therapy, and if necessary respiratory stimulants will be used to treat. The experimental group will receive BIPAP + routine treatment, generally selecting S/T mode. The inspiratory pressure (IPAP) will be greater than the expiratory pressure (EPAP), the oxygen flow rate will be adjusted to ensure an arterial oxygen saturation (SaO₂) greater than 90%, and the daily duration of treatment will be more than 5 hours.

These include results of blood gas analysis, including partial pressure of arterial oxygen (PaO₂), PaCO₂, and pH; intubation rate; and pulmonary function, including forced expiratory volume in 1 second and forced expiratory volume in 1 second/forced vital capacity.^[13]

These include heart rate, respiratory rate, hospitalization time, incidence of complications, blood pressure, and mortality.

The search strategy for this study will be applied to 4 Chinese databases: China National Knowledge Infrastructure (CNKI), Wanfang Database, Chinese Science and Technology Journal Database (VIP), and Chinese Biomedical Literature database (SinoMed); and 5 foreign literature databases: PubMed, Cochrane Library, Springer, EBSCO, and Web of Science. All the English and Chinese literature published from inception to October 2020 will be included. The search strategy for PubMed is shown in Table ​Table1,1, and searches in other databases also follow this search strategy.

Search strategy for Pubmed.