ABSTRACT
Chronic obstructive pulmonary diseases (COPD) is defined according to criteria of the American Thoracic Society (ATS) as a disease state characterized by the presence of airway obstruction due to chronic bronchitis or emphysema. The airflow limitation is generally progressive, is often accompanied by airway hyperresponsiveness, and is usually but not always persistent (1). There is some inconsistency in the definition of COPD in that COPD cannot be considered as one disease entity but rather as a complex of conditions that contribute to airflow limitation. COPD is defined functionally, whereas chronic bronchitis is defined by symptoms, and emphysema by gross pathology. Chronic bronchitis is, according to ATS criteria, defined as a disease with a chronic productive cough for 3 months in each of two successive years in a patient in whom other causes of chronic cough have been excluded (1). Emphysema is, according to these criteria, defined as a condition of the lung characterized by abnormal permanent enlargement of the air spaces distal to the terminal bronchioles accompanied by destruction of their walls and without obvious fibrosis (1,2). Given these defini-
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tions, it is clear that chronic bronchitis can be present in a patient with predominantly emphysema and vice versa.
