Previous studies suggested that plasma B-type natriuretic peptide (BNP) level was often elevated in patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD) and was associated with increased mortality. However, most studies did not consider the fact that conditions such as coronary ischemic heart disease can also increase BNP level. Therefore, we aimed to explore the association between BNP level and in-hospital mortality in patients with AECOPD without a history of coronary ischemic heart disease.
In this retrospective cohort study, data on patients with AECOPD but without a history of coronary ischemic heart disease who were admitted in a comprehensive hospital from January 2017 to December 2019 and were identified using International Statistical Classification of Diseases and Related Health Problems, Nineth Revision (ICD-9) codes were included. BNP level was determined within 24 hours after admission, and the value was log2 transformed. The primary outcome was in-hospital mortality, and the secondary outcome was a composite outcome of in-hospital mortality or invasive mechanical ventilation.
A total of 300 patients were included in this study (mean ages, 76.88 years; SD, 9.87; men, 63.33%). Sixteen patients (5.33%) showed in-hospital mortality; 29(9.67%) and 22 (6.67%) patients were assisted with invasive mechanical ventilators and noninvasive positive pressure ventilators, respectively. Univariate cox regression analysis showed that the unadjusted HRs of the primary and secondary outcomes were 1.85 (95% CI, 1.39-2.47) and 1.42 (95% CI, 1.19-1.71), respectively. After adjustment for age, sex, past medical history, smoking status, drinking status, CURB65 (Confusion, Urea > 7mmol/L, Respiratory rate≥30/min, Blood pressure systolic < 90 mmHg or diastolic <60 mmHg and age > 65 years), arterial partial pressure of O2(PaO2), arterial partial pressure of CO2 (PaCO2), neutrophil count, and D-dimer level (only secondary outcome), the adjusted HRs of the primary and secondary outcomes were 2.44 (95% CI, 1.43-4.14) and 1.36 (95% CI, 1.07-1.74), respectively. The results of subgroup analysis by age, sex, and lung function were robust.
The plasma log2BNP level was significantly associated with in-hospital mortality and a composite outcome of in-hospital mortality or invasive mechanical ventilation