Phenotypes Of Copd

Chronic obstructive pulmonary disease (COPD) is characterized by chronic airflow limitation. Chronic airflow limitation is resulted from increases in small airway resistance and losses in elastic recoil pressure of the lung. Thus the chronic airflow limitation is caused by a small airway disease and/or emphysema.Although patients with COPD could have small airway disease and/or emphysema, in reality patients with COPD have been dealt as patients with a single disease entity. Not only the patients with COPD have been treated with the same therapeutics, but also they have been studied under the same name of COPD for the research of COPD. One of the reasons for this illogical practice could be due to no existence of practical tool, which can differentiate these two diseases. Emphysema is classified into two main phenotypes of centrilobular emphysema (CLE) and panlobular emphysema (PLE). CLE is found in upper and PLE is in the lower lobes. Pathologic studies and morphometric studies have shown that CLE is closely associated with small airway disease. Studies suggest that CT can differentiate upper-lobe dominant from lower-lobe dominant emphysema, therefore upper-lobe dominant CLE from lower-lobe dominant PLE. Then, CT can differentiate small airway disease, which is associated with CLE from PLE. However, further development of valid and simpler tests for differentiation of phenotypes of COPD is urgently needed.