Chronic obstructive pulmonary disease (COPD) is a
progressive syndrome of expiratory airflow limitation
caused by chronic inflammation of the airways and lung
parenchyma. Closely linked to smoking, COPD is a public
health problem of epic proportions. In 2001, it was the
fourth leading cause of death in the United States,1 and it
is predicted to become the fifth greatest public health
problem worldwide by 2020.