After the introduction of the Gut-Lung axis theory, extensive studies revealed diversity of microbiomes among healthy smokers and COPD patients form the respiratory samples or lung tissues. In the previous study, distinct difference in composition of microbiome in lung tissue between healthy smokers and COPD patients was reported. This is a cross sectional study to analyze composition of microbiome of various samples (e.g. feces, sputum, and urine) and to compare difference of composition between COPD patients and healthy smokers. This study would help establishing gut-lung axis model in humans.
