NPPB and chronic obstructive pulmonary disease: No statistical difference was found among four groups in regard to age, sex ratio, smoking history, AE history, FEV1, GOLD stages, and COPD groups (P > 0.05 for all comparisons), except for BMI (P = 0.025), mPAP (P = 0.016), 6MWD (P = 0.003), NT-pro BNP (P<0.001), PaO2 (P = 0.006), peak VO2(P = 0.018) and hemoglobin (P = 0.036) at the baseline.