COPD stands for chronic obstructive pulmonary disease."Chronic" means long term, "obstructive" means there is a blockage to air flow, and "pulmonary" refers to the lungs. COPD is used to describe a class of diseases characterized by relatively irreversible limitations of airflow in the lungs. The most familiar disease in this group is emphysema, in which the lung's tiny air sacs become damaged, then destroyed, and unable to participate in air exchange. This results in the trapping of "stale" air. Equally identifiable by most people is chronic bronchitis, in which the lung's airways become swollen and produce excessive amounts of mucus. This too results in obstruction of airflow and, as with emphysema, in increased difficulty breathing accompanied by shortness of breath.
While there are other obstructive lung diseases, most notably asthma, it is emphysema and chronic bronchitis that most lung specialists have in mind when they use the term COPD. Chronic obstructive pulmonary disease affects between 15 million and 30 million Americans and is the fourth leading cause of death in the United States. The annual direct and indirect medical costs related to COPD now exceed $30 billion.
While some individuals may have primarily emphysema or chronic bronchitis, most have both; some may, in addition, have asthmalike symptoms. While COPD affects different people in different ways, its main symptoms include shortness of breath (dyspnea) with activity and chronic coughing. In more than 95 percent of those with COPD in the United States, the disease has been caused by cigarette smoking.
The best way to keep from getting COPD is not to smoke—or to quit if you do. It is never too late to quit smoking. Even in the advanced stages of the disease, smoking cessation reduces the rate of loss of lung function, reduces the frequency of "exacerbations" (acute bouts of worsening of one's breathing that are often associated with lung infection and not infrequently require hospitalization), and results in increased longevity. In fact, the two major causes of increased longevity are smoking cessation and the administration of oxygen if it is needed.
There is no cure for COPD, but what was once deemed to be a disease with a hopeless prognosis is now known to be very treatable. Early diagnosis and treatment can enable people with COPD to take charge of their breathing and regain control of their lives. Common treatment goals include becoming more active, decreasing shortness of breath, a lowering of anxiety and depression, and an improved quality of life.
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COPD affects the lung's bronchial tubes, which branch from the windpipe or trachea, and the alveoli, the small air sacs where oxygen is transferred into the bloodstream to be carried to the tissues and carbon dioxide is transferred into the blood returning to the heart, to be exhaled by the lungs. The condition also affects the lining of the airways. This lining helps clean the lung tissue by producing mucus that traps particles (irritants, allergens, and infectious organisms), which are then swept up and out of the lungs by the wave motion of tiny hairlike projections called cilia. When exposed to cigarette smoke, the cilia stop moving, allowing the particles, viruses, and bacteria to remain in the lungs and cause further damage.
Smoking is unequivocally the No. 1 cause of COPD, which is why it is considered to be a very preventable disease. This conclusion is justified by the fact that, at least in the United States, the condition is seen so uncommonly among nonsmokers. Smoking can damage both the airways and air sacs. In emphysema, the walls of the air sacs are damaged and individual air sacs collapse into fewer, larger air sacs, which lose their ability to transfer gases in and out of the bloodstream. In addition, air is trapped in these large, diseased, nonfunctional air sacs. Over time, this causes the air sacs, and the lungs, to become bigger (hyperinflate), especially with exercise; the hyperinflation is accompanied by increased difficulty breathing and shortness of breath. (To demonstrate, take a deep breath and then, while holding the air in your hyperinflated lungs, attempt to take a series of normal breaths.)
In chronic bronchitis, excessive amounts of mucus are produced. This mucus is often of poor quality--tenacious and difficult to expel, even with coughing. This mucous defense against bacteria, viruses, and other foreign particles is seriously compromised, and these particles remain in the lungs to cause infection and inflammation. It then becomes increasingly difficult for the already damaged cilia to sweep the particle-laden mucus out of the lungs. The retained mucus further narrows the airways, and this narrowing acts in concert with hyperinflation to make it even more difficult to breathe.
Cigarette smoking is by far the most serious and common risk factor for COPD, but there are other risk factors that make it more likely that a person will develop the disease. These risk factors fall into two categories: host factors and environmental exposures.
- A history of frequent or severe childhood respiratory infection
- A personal or family history of asthma or COPD (so-called familial clustering)
- A personal history of airway hyperreactivity (a defining feature of asthma)
- A genetic predisposition to emphysema, including a hereditary deficiency of the blood protein alpha-1 antitrypsin, which, when combined with cigarette smoke, can result in precocious COPD, not infrequently in the third or fourth decade of life. There are likely more genetic factors leading to susceptibility to COPD, but these have yet to be determined.
- Exposure to sidestream (passive) tobacco smoke
- Exposure to tobacco smoke in utero
- Exposure to chemicals and dust on the job, including vapors, irritants, and fumes.
- Exposure to indoor or outdoor air pollution. Indoor pollution is a very important risk factor in Third World countries, particularly for women.
Last reviewed on 11/9/09
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