Data analysis
AECOPD
REGRESSION, PLEURAL EFFUSION, LOBAR PNEUMONIA, PULMONARY EDEMA
We described the distribution of baseline demographic and clinical characteristics of patients using numbers (proportions) and means [standard deviation (SD)], as appropriate. Univariable and multivariable logistic regression models were fit to investigate relationship between i) AECOPD with and without other conditions as the dependent variable, and potential risk factors as independent variables, ii) AECOPD alone as the dependent variable, and potential risk factors as independent variables. Five independent variables (subjective increase in sputum purulence, venous pCO2, radiographic evidence of pleural effusion, pulmonary edema, and lobar pneumonia) in multivariable analysis were selected based on univariate analysis results and clinical importance agreed among study investigators. All statistical analyses were conducted using SAS for windows version 9.4(SAS Institute, Cary, NC).