Definition	Chronic obstructive pulmonary disease (COPD) is airflow obstruction caused by chronic bron-chitis or emphysema. Emphysema is abnormal permanent enlargement of the air spaces distal to the terminal bronchioles, accompanied by destruction of their walls and without obvious fibrosis. Chronic bronchitis is chronic cough or mucus production for at least three months in at least two successive years when other causes of chronic cough have been excluded.1
Incidence/Prevalence	COPD mainly affects middle-aged and elderly people. It is one of the leading causes of morbidity and mortality worldwide. In the United States, it affects about 14 million people and is the fourth leading cause of death. Morbidity and mortality are rising. Estimated prevalence in the United States has risen by 41 percent since 1982, and age-adjusted death rates rose by 71 percent between 1966 and 1985. All-cause age-adjusted mortality declined over the same period by 22 percent, and mortality from cardiovascular diseases declined by 45 percent.1 In the United Kingdom, physician-diagnosed prevalence was 2 percent in men and 1 percent in women between 1990 and 1997.2
Etiology/Risk Factors	COPD is largely preventable. The main cause is exposure to cigarette smoke. COPD is rare in lifetime non- smokers (estimated incidence 5 percent in three large representative U.S. surveys from 1971 to 1984), in whom exposure to environmental tobacco smoke will explain at least some diseases.3,4 Other proposed causes include airway hyperresponsiveness, air pollution, and allergy.5–7
Prognosis	Airway obstruction is usually progressive in those who continue to smoke, resulting in early disability and shortened survival. Smoking cessation reverts the rate of decline in lung function to that of nonsmokers.8 Many people will need medication for the rest of their lives, with increased doses and additional drugs during exacerbations.
Clinical Aims	To alleviate symptoms, to prevent exacerbations, to preserve optimal lung function, and to improve activities of daily living, quality of life, and survival.9
Clinical Outcomes	Short- and long-term changes in lung function, including changes in forced expiratory volume in one second (FEV1); exercise tolerance; peak expiratory flow rate; frequency, severity, and duration of exacerbations; symptom scores for dyspnea; quality of life; and survival.