To analyze the risk factors for secondary pulmonary infection in patients with chronic obstructive pulmonary disease (COPD) complicated by heart failure (HF).

All of 76 COPD patients with HF admitted to our hospital from January 2023 to December 2024 were selected as subjects. They were divided into groups based on the occurrence of pulmonary infection: 31 patients with secondary pulmonary infection were assigned to the observation group, and 45 patients without secondary infection were assigned to the control group. Clinical data were collected, and the occurrence of pulmonary infection was analyzed. Multivariate Logistic regression analysis was used to identify the influencing factors for secondary pulmonary infection in COPD patients with HF. A nomogram was constructed, and its predictive value was analyzed.

In the observation group 26 cases (83.87%) had a higher prevalence of diabetes history and 25 cases (80.65%)long-term use of glucocorticoids or antibiotics compared to the control group diabetes history 10 cases(22.23%); long-term glucocorticoid/antibiotic use 15 cases( 33.33%). Serum albumin levels were lower in the observation group (34.70±4.55) g/L than in the control group (39.58±4.60) g/L (P<0.05). Logistic regression analysis identified diabetes history (OR=1.050, 95%CI: 1.024~1.077), long-term use of glucocorticoids or antibiotics (OR=1.104, 95%CI: 1.043~1.169), and serum albumin level (OR=0.850, 95%CI: 0.792~0.912) as risk factors for secondary pulmonary infection in COPD patients with HF (P<0.05). The dataset was split into a training set (53 cases) and a validation set (23 cases) in a 7︰3 ratio. The area under the curve (AUC) (95% CI) of receiver operating characteristic (ROC) curve for predicting secondary pulmonary infection was 0.88 (0.77~0.98) in the training set and 0.90 (0.77~1.00) in the validation set. The calibration curve of the nomogram for predicting secondary pulmonary infection approximated the ideal curve (P=0.449, 0.188). Decision curve analysis (DCA) showed a positive net benefit within the nomogram probability threshold range of 20% to 85%. Among the 76 COPD patients with HF, 70 survived and 6 died, with 2 deaths due to pulmonary infection, 2 due to acute respiratory failure, and 2 due to malignant arrhythmia.

History of diabetes, long-term use of glucocorticoids or antibiotics, and low serum albumin levels are risk factors for secondary pulmonary infection in COPD patients with HF.