NPPB and hydrops fetalis: Both B-type natriuretic peptide (BNP) and N-terminal prohormone of brain natriuretic peptide (NT-proBNP) are useful markers to exclude HF in patients with AECOPD [122,123,124,125] (Figure 3), but BNP is less reliable, and the related studies have major limitations such as the underuse of echocardiography to diagnose HF and misdiagnosis of HF due to advanced lung diseases that cause increased pulmonary arterial pressure (cor pulmonale) [126,127].