Information about Chronic Obstructive Pulmonary Disease
Chronic obstructive pulmonary disease encompasses both chronic bronchitis and emphysema. COPD symptoms develop slowly over several years and include wheezing, a chronic cough that produces phlegm and progressive shortness of breath.
Causes of COPD
Cigarette smoking causes the vast majority of COPD cases. Cigarette smoke is thought to release enzymes that damage a protein called elastin, which makes the lungs elastic. Smoking is also believed to inactivate alpha1 antitrypsin, a protein produced by the liver that normally protects elastin from the action of these enzymes.
Approximately one in 2,500 people worldwide has a genetic defect that prevents the secretion of alpha1 antitrypsin by the liver and increases the risk of developing premature emphysema, especially in smokers. Other factors that raise the risk of emphysema include a family history of COPD, male gender, respiratory illnesses in childhood, and work-related exposure to pollutants.
Typically, people who develop COPD began smoking at an early age and have a long history of a morning cough that produces phlegm. Lung function often declines slowly over many years. Most people only seek medical advice after age 50 when they begin to notice significant shortness of breath during exertion. As COPD worsens, breathlessness begins to severely limit their activities.
To help identify COPD at its earliest stages before it causes serious lung damage, anyone at risk for the disease should be tested at the first sign of any breathing difficulties. Although lung function tends to decrease slowly, the decline is frequently punctuated by acute episodes of worsening symptoms, usually because of a viral or bacterial infection. These acute episodes are marked by increased shortness of breath, wheezing, and a cough that produces greater than usual amounts of phlegm. Though acute episodes may be severe enough to be life threatening, they do not necessarily speed the rate of disease progression.
COPD may also cause low levels of oxygen in the blood, which can lead to pulmonary hypertension, a rise in pressure in the arteries that carry blood to the lungs. Pulmonary hypertension increases the workload of the right ventricle, one of the lower chambers of the heart, causing it to enlarge.
At advanced stages of COPD, individuals frequently become thin because they find it tiring even to eat and because the work of breathing burns more calories than it does in healthy people. There also may be other causes that have yet to be defined. People with advanced COPD also may become depressed and anxious. These problems are treatable, but many people with COPD are not receiving the help they need for depression and anxiety.
A doctor who suspects COPD will perform a physical exam and listen to the breath sounds with a stethoscope. He or she will also look at the results of spirometry, lung volume, and diffusing capacity tests, which not only can indicate the presence and severity of COPD but also can help define the prognosis.
Imaging tests also help with the diagnosis. A chest x-ray may show an increased volume of air in the lungs and enlargement of the central pulmonary artery, which extends from the heart's right ventricle to the lungs. Also, depending on the stage of the disease, changes are sometimes visible as abnormalities in the electrical activity of the heart, measured on an electrocardiogram (ECG).
Looking for a genetic cause by measuring alpha1 antitrypsin levels may be useful when COPD affects a young person or a nonsmoker.