Chronic obstructive pulmonary disease (COPD), also known as chronic obstructive lung disease, is a general term for a group of conditions in which there is persistent difficulty in expelling (or exhaling) air from the lungs. COPD commonly refers to two related, progressive diseases of the respiratory system, chronic bronchitis and emphysema. Because smoking is the major cause of both diseases, chronic bronchitis and emphysema often occur together in the same patient.

COPD is one of the fastest-growing health problems. Nearly 16 million people in the United States, 14 million with chronic bronchitis and 2 million with emphysema, suffer from COPD. COPD is responsible for more than 96,000 deaths annually, making it the fourth leading cause of death. Although COPD is more common in men than women, the increase in incidence of smoking among women since World War II has produced an increase in deaths from COPD...