Cigarette smoking is the cause in up to 90 percent of emphysema cases. A smoker is 10 times more likely to die of COPD than a nonsmoker. Scientists believe that, in addition to smoking-related processes, other factors are involved in the disease, because only 15 to 20 percent of smokers develop emphysema. The nature and role of these other factors in smokers' emphysema are not yet clear. Other factors that may contribute to emphysema include air pollution and fumes and dust in the workplace. There is also a form of emphysema that runs in families. People with this form of the disease have a deficiency of a blood component called alpha-l-protease inhibitor, also called alpha-l-antitrypsin (AAT). A blood test can detect this deficiency.

At first, shortness of breath occurs during a physical activity. As the disease progresses, shortness of breath is present all the time, even while sitting quietly.

In emphysema, the alveoli (tiny, elastic air sacs of the lung) are permanently destroyed. This occurs because of the irreversible destruction of a protein in the lungs called elastin, which helps maintain the strength of the alveolar walls. The loss of elastin also causes the collapse or narrowing of the smallest air passages, called bronchioles, which in turn limits airflow out of the lungs. Air continues to get into alveoli when the lungs expand during inhalation, but it is often unable to escape during exhalation because the air passages tend to collapse during exhalation, trapping the "stale" air in the lungs. The passageways become plugged with mucus.

The decline is gradual in healthy nonsmokers. Because healthy nonsmokers have excess lung capacity when younger, the slow loss of lung function isn't noticeable. The decline in smokers, however, is rapid and significant. If a smoker quits before COPD develops, the decline levels off until it is nearly normal for the person's age.

Emphysema and other forms of COPD make the heart work harder. The right ventricle enlarges and thickens because it must force blood into the lungs, which have been damaged or destroyed by the disease. Blood vessels in the lungs constrict because COPD reduces the amount of oxygen in the blood. The right ventricle works harder and harder to pump blood into these narrow vessels. An enlarged heart can cause abnormal heartbeats, which disturb the normal heart rhythm. People with this condition get tired easily and have chest pains and palpitations. The poor oxygen supply characteristic of emphysema also affects the brain, causing headaches, sleep problems, and irritability.

A person with emphysema or other forms of COPD usually has an enlarged heart because of damaged lungs. If the heart is put under extra strain because of a minor illness, it may not be able to supply enough blood to the liver and kidneys. If these organs can't carry out their functions, the person may develop swelling of the ankles, legs, and abdomen. Because of poor oxygen supply, a person with emphysema may have a bluish tinge to skin, lips, and nails.

The person should also get a pneumonia vaccination. A person with emphysema or other forms of COPD is less able to tolerate the flu and pneumonia. Complications of these illnesses can be fatal in a person with COPD. Other ways a person with emphysema can cope: Stop smoking. Avoid air pollution and cut back on physical activities during any air pollution alerts. Stay away from dust and fumes at work and people with respiratory infections. Avoid extreme hot and extreme cold, as well as very high altitudes. (Supplemental oxygen may be required for flying on commercial aircraft.) Drink plenty of fluids to keep sputum loose.

A chest X-ray can show over-inflation of the lungs, which can suggest emphysema, but it is not used to diagnose this disease. Instead, a doctor diagnoses emphysema through a physical exam and medical history. He or she will listen to the patient's breathing and measure lung capacity. The doctor also may order a high-resolution CT scan to help with diagnosis.