NPPB and chronic obstructive pulmonary disease: Several non-invasive tools may suggest the presence of PH in COPD patients, including laboratory testing (especially N-terminal pro-brain natriuretic peptide (NT-pro-BNP), diffusion capacity for carbon monoxide (DLCO), echocardiography, chest CT, 6-min walk test, cardiopulmonary exercise testing and electrocardiogram (ECG) [5].