Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is characterized by the progressive development of airflow limitation that is not fully reversible.1 The term COPD encompasses chronic obstructive bronchitis, with obstruction of small airways, and emphysema, with enlargement of air spaces and destruction of lung parenchyma, loss of lung elasticity, and closure of small airways. Chronic bronchitis, by contrast, is defined by the presence of a productive cough of more than three months' duration for more than two successive years. The cough is due to hypersecretion of mucus and is not necessarily accompanied by airflow limitation. However, there is some epidemiologic evidence that . . .