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Chronic Obstructive Pulmonary Disease (Chronic Bronchitis, Emphysema)

By Robert A. Wise, MD

Chronic obstructive pulmonary disease is persistent narrowing (obstruction) of the airways occurring with emphysema, chronic obstructive bronchitis, or both disorders.

  • Cigarette smoking is the most important cause of chronic obstructive pulmonary disease.

  • People develop a cough and eventually become short of breath.

  • Diagnosis is made with chest x-rays and tests of lung function.

  • Stopping smoking and taking drugs that help keep airways open are important.

  • People who have severe disease may need to take other drugs, use oxygen, or have pulmonary rehabilitation.

In the United States, about 15 million people have chronic obstructive pulmonary disease (COPD). It is the third most common cause of death, accounting for 135,000 deaths in 2010. From 1980 to 2000, the number of deaths due to COPD increased 64%, but since then, the number of deaths has been steady. More than 97% of all COPD-related deaths occur in people older than age 64. COPD affects women more often than men, but men and women die as a result of COPD at about equal rates. COPD is more often fatal in whites than in nonwhites and in people from lower income groups, probably because people in these groups are also more likely to smoke.

Worldwide, the number of people with COPD is increasing. Factors contributing to COPD include an increase in smoking in many developing countries and, throughout the world, exposure to toxins in biomass fuels such as wood and grasses. Death rates may be increasing in developing countries. By 2030, COPD is projected to become the third leading cause of death worldwide.

COPD leads to a persistent decrease in the rate of airflow from the lungs when the person breathes out (exhales), which is called chronic airflow obstruction. In most people, this airflow obstruction is partially reversible, either spontaneously or with treatment. COPD includes the diagnoses of chronic obstructive bronchitis and emphysema. Many people have both disorders.

  • Chronic bronchitis is defined as cough that produces sputum repeatedly during two successive years. When chronic bronchitis involves airflow obstruction, it qualifies as chronic obstructive bronchitis.

  • Emphysema is defined as widespread and irreversible destruction of the alveolar walls (the cells that support the air sacs, or alveoli, that make up the lungs) and enlargement of many of the alveoli.

The small airways (bronchioles) of the lungs contain smooth muscles and are normally held open by their attachments to alveolar walls. In emphysema, the destruction of alveolar wall attachments results in collapse of the bronchioles when a person exhales, causing airflow obstruction that is permanent and irreversible. In chronic bronchitis, the glands lining the larger airways (bronchi) of the lungs enlarge and increase their secretion of mucus. Inflammation of the bronchioles develops and causes smooth muscles in lung tissue to contract (spasm), further obstructing airflow. Inflammation also causes swelling of the airway passages and secretions in them, further limiting airflow. Eventually, the small airways in the lung become narrowed and destroyed. Asthma is also characterized by airflow obstruction (see Asthma). However, unlike airflow obstruction in COPD, airflow obstruction in asthma is completely reversible in most people, either spontaneously or with treatment.

Airflow obstruction in COPD causes air to become trapped in the lungs after a full exhalation, increasing the effort required to breathe. Also in COPD, the number of capillaries in the walls of the alveoli decreases. These abnormalities impair the exchange of oxygen and carbon dioxide between the alveoli and the blood. In the earlier stages of COPD, oxygen levels in the blood may be decreased, but carbon dioxide levels remain normal. In the later stages, carbon dioxide levels increase and oxygen levels fall.

If low oxygen levels are not treated with supplemental oxygen, complications can occur. Low oxygen levels in the blood, if not treated, stimulate the bone marrow to send more red blood cells into the bloodstream, a condition known as secondary polycythemia (also called erythrocythemia—see Polycythemia Vera). The low oxygen levels in the blood also constrict the blood vessels leading from the right side of the heart to the lungs, thereby increasing the pressure in these vessels. As a result of the increased pressure, called pulmonary hypertension, failure of the right side of the heart can occur (called cor pulmonale—see ). People with COPD also have an increased risk of developing heart rhythm abnormalities (arrhythmias). People with COPD who smoke have a higher risk of developing lung cancer than do people who do not have COPD but smoke the same amount. People with COPD seem to have an increased risk of developing osteoporosis, depression, coronary artery disease, muscle wasting (atrophy), and gastroesophageal reflux. However, it is not clear whether the risk is increased because of COPD or other factors.

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