2.1. Study population

Three hundred thirty patients with AECOPD admitted to our hospital from June 2020 to June 2023 were retrospectively analyzed as a training set for the construction of the model. Three Hundred Twenty-five AECOPD patients admitted to the Second People’s Hospital of Hefei from 2006 to June 2023 were also collected as the validation set for the validation of the model. AECOPD was defined based on the International Classification of Diseases, Ninth Revision (ICD-9) code 491.21. For patients with multiple hospitalizations, only the first hospitalization was registered. Diagnosis of acute heart failure: clinical manifestations such as shortness of breath, orthopnea, pulmonary rales, pink foamy sputum; NT-proBNP: > 450 ng/L in patients under 50 years old, > 900 ng/L in patients over 50 years old, > 1800 ng/L in patients over 75 years old, and > 1200 ng/L in patients with renal insufficiency (glomerular filtration rate < 60 mL/minutes). Exclusion criteria : Combined with other respiratory diseases such as bronchial asthma, tuberculosis, etc.; Accompanied by severe heart, liver, and kidney dysfunction or abnormalities; Combined with immunodeficiency and malignant tumors; other exclusion criteria include length of hospital stay < 48 hours, data loss > 10%. This study was approved by the Ethics Committee of Fuyang Cancer Hospital and the Second People’s Hospital of Hefei.