Chronic obstructive pulmonary disea

Chronic obstructive pulmonary disease (COPD) is a group of disorders characterized by incompletely reversible
airfow obstruction. The understanding of true pathogenesis is limited due to heterogeneity of the disease1
. A “phenotype”
describes the outward physical manifestations of a particular disease, and compromises anything that is part of the
observable structure, function or behavior of an individual phenotype2
. The symptoms, radiography, physiology, or biology
will require an iterative validation process in which ‘‘candidate’’ phenotypes3
. Recognizing the different phenotypes of
COPD is important for understanding the underlying disease processes and also clinically relevant due to potential
differing responses to therapeutic interventions.4-5
According to American Thoracic Society non-proportional Venn diagram, major three obstructive lung diseases
includes emphysema, chronic bronchitis and asthma6
. These different phenotypes can occur alone or with combination.
However, the data are less valid due to non-standardized physician diagnoses without objective investigation. Frequent
exacerbation, defned by two or more exacerbation per year7
, is another interesting phenotype, and known to be associated
with poorer quality of life and increased risk of death.8