Chul-Ho Yoon

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BACKGROUND Chronic obstructive pulmonary disease (COPD) is now regarded as a heterogenous disease, with variable phenotypes. Acute exacerbation of COPD is a major event that alters the natural course of disease. The frequency of COPD exacerbation is variable among patients. We analyzed clinical features, according to the frequency of acute exacerbation in(More)
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