Chronic obstructive pulmonary disease (COPD)—also called chronic obstructive lung disease— results from emphysema, chronic bronchitis, asthma, or any combination of these disorders. Usually, more than one of these underlying conditions coexist; most often, bronchitis and emphysema occur together. (See Understanding chronic obstructive pulmonary disease, pages 192 to 195.)

The most common chronic lung disease, COPD affects an estimated 17 million Americans, and its prevalence is rising. It affects more men than


women and more whites than blacks. It doesn’t always produce symptoms and causes only minimal disability in many patients. However, COPD tends to worsen with time.