ABSTRACT
Chronic obstructive pulmonary disease (COPD) refers to a heterogeneous collection of disorders that share a common physiological abnormality: limitation of expiratory airflow (1,2). Rigorous definition of COPD has been difficult, in part because it represents a collection of disorders that are themselves heterogeneous. In general, many disorders including cystic fibrosis, bronchiectasis, and localized airway lesions are excluded from the definition of COPD. Current usage includes both chronic bronchitis and emphysema within the definition of COPD, recognizing that either condition may be present without clinically significant airflow limitation. Asthma is also characterized by airflow limitation, but, in contrast to COPD, where airflow limitation may be partially reversible, in asthma airflow limitation is largely reversible either spontaneously or with treatment. Recent evidence, however, suggests that asthma per se may be associated with progressive irreversible loss of expiratory airflow (3,4). This has led to semantic and nosological difficulties. The currently accepted best definition of COPD, adopted by the Global Initiative for Chronic
Obstructive Pulmonary Disease (GOLD) is: ‘‘COPD is a disease state characterized by airflow limitation that is not fully reversible. The airflow limitation is both progressive and associated with an abnormal inflammatory response of the lungs to noxious particles and gases’’ (5).
