Chronic obstructive pulmonary disease (COPD) is a general term for a group of diseases that cause progressive damage to your lungs.
These diseases include:
Emphysema develops gradually, and you may not experience symptoms until long-term damage to the tiny air sacs in your lungs (alveoli) causes you to feel short of breath. In fact, shortness of breath is usually the first symptom of the disease.
Cigarette smoking is the major cause of emphysema, accounting for more than 80 percent of all cases. Emphysema occurs most often in people older than age 40 who have smoked for many years. Long-term exposure to secondhand smoke also may play a role.
In addition to affecting your breathing, emphysema increases your risk of pneumonia, asthma, acute and chronic bronchitis, and other serious respiratory diseases. It's not uncommon for smokers to have emphysema, chronic bronchitis and asthma at the same time. Smokers with COPD also have an increased risk of lung cancer.
Signs and symptoms
Emphysema may produce the following signs and symptoms:
When you inhale, air travels to your lungs through two major airways called bronchi. Inside your lungs, the bronchi subdivide nearly 20 times into a million smaller airways (bronchioles), which finally end in clusters of tiny air sacs. You have about 300 million air sacs in each lung. Within the walls of the air sacs are small blood vessels (capillaries) where oxygen is added to your blood and carbon dioxide — a waste product of metabolism — is removed.
The air sac walls also contain elastic fibers that help them expand and contract like small balloons when you breathe. But in emphysema, inflammation destroys these fragile walls, causing them to lose their elasticity. As a result, the bronchioles collapse when you exhale, and air becomes trapped in the air sacs, which overstretches them.
In time, this overstretching (hyperinflation) may cause several air sacs to rupture, forming one larger air space instead of many small ones. Because the larger air sacs aren't able to force air completely out of your lungs when you exhale, you have to breathe harder just to get enough oxygen and eliminate carbon dioxide.
What causes emphysema?
A small number of people are born with a deficiency of a protein called alpha-1-antitrypsin (AAT), which normally protects the elastic fibers in the walls of your air sacs. People who have too little AAT are likely to develop severe emphysema in their 30s or 40s — a condition called AAT deficiency-related emphysema.
The single greatest risk factor for emphysema is smoking, which accounts for at least 80 percent of all cases of the disease. Emphysema is most likely to develop in cigarette smokers, but cigar and pipe smokers also are at risk. Men are affected more often than women, but this statistic is changing as more women begin to smoke.
Other risk factors include: