Chronic obstructive pulmonary disease (COPD) refers to two lung diseases that are closely related: emphysema and chronic bronchitis. Although these diseases often occur together, you may have symptoms more characteristic of one than the other. In both conditions, airflow out of the lungs is restricted, making breathing difficult. Up to 90 percent of COPD cases are caused by smoking, and smokers are 10 times more likely to die from the disease. Frequent lung infections and exposure to certain industrial chemicals can also cause COPD, and in some cases are related to genetic abnormalities. Approximately 16 million Americans have been diagnosed with COPD. It is estimated that at least 12 million additional Americans have the disease but have not been diagnosed. Although the changes in lung tissue differ between the two diseases that characterize COPD, the causes and treatments are similar.
Chronic bronchitis is characterized by inflamed airway tissue and excessive mucus production. This leads to a persistent, productive cough that lasts for several months each year. Sometimes the large and small airways of the lungs become narrowed, and the lining of the passageways may become scarred. This makes it hard to move air in and out of your lungs, resulting in shortness of breath. More than 12 million Americans have chronic bronchitis.
In emphysema, the walls between the tiny air sacs in the lungs lose their ability to stretch, and they become weakened and break. As the lung tissue becomes less elastic, air is trapped inside the air sacs, and the exchange of oxygen and carbon dioxide is impaired. Nearly three million Americans have emphysema.