ABSTRACT
Introduction Chronic obstructive pulmonary disease (COPD) has been variously defined, but it includes the common thread of (expiratory) airflow limitation that is progressive and only partly, if at all, reversible. It is characterized by abnormal airway inflammation, may be accompanied by airway hyperreactivity, and encompasses both, primarily clinically defined, chronic bronchitis and, the more pathologically or radiographically evident, emphysema.1
