ABSTRACT
In the 1990s, the two most commonly used definitions of chronic obstructive
pulmonary disease (COPD) were those proposed by the European Respiratory
Society (1) and American Thoracic Society (2). The ERS stated that ‘‘COPD is a
disorder characterized by reduced maximum expiratory flow and slow forced
emptying of the lungs-features which do not change markedly over several months.
Most of the airflow limitation is slowly progressive and irreversible. The airflow
limitation is due to varying combinations of airway disease and emphysema (1).
