In addition to being a biomarker for heart failure, BNP is also one of the biomarkers for the severity and prognosis of CAP.[15] The significant elevation of the BNP levels in patients with severe C. psittaci pneumonia was probably due to hypoxia and increased pro-inflammatory cytokine secretion.[16] The high levels of inflammatory factors (CRP, PCT) and low oxygenation index observed in this study supports this hypothesis. Here, NPPB is linked to heart failure.