Emphysema is a type of chronic obstructive airway disease, or COPD. People with COPD have limitations in the flow of air through their airways. Emphysema involves the gradual destruction of alveoli in the lungs. The alveoli are air spaces where oxygen is exchanged with carbon dioxide in the blood.
What is going on in the body?
The most common cause of emphysema is smoking. Long-term exposure to smoke causes destruction of the alveoli. The ability of the lungs to provide oxygen to the body decreases. As a result, the person finds it increasingly difficult to breathe and to exercise without discomfort.
The World Health Organization, or WHO, has recently developed a classification system for the severity of emphysema and other forms of COPD. There are four stages of severity, as outlined below:
Stage 0, or at risk for COPD. These people have chronic cough and sputum production. Their lung function tests are still normal.
Stage I, or mild COPD. Individuals in this group have mild limitations in their airflow and changes in their lung function tests. They generally have chronic cough and sputum production.
Stage II, or moderate COPD. People at this stage have worsening of airflow that leads to shortness of breath with exertion. Their lung function tests show marked limitations.
Stage III, or severe COPD. Individuals at this stage have severe airflow limitations that impair their quality of life. Their lung function tests are markedly abnormal.
What are the causes and risks of the disease?
Cigarette smoking is the most common cause of emphysema. The risk goes up with the amount of tobacco smoked and the number of years of smoking. Emphysema is most common in countries where smoking is prevalent. It is less common in countries where people smoke less. Passive smoking, or exposure to secondhand smoke, does increase a person's risk for emphysema.
No one knows why only 10% to 15% of smokers get emphysema. Scientists think that certain people are predisposed because of their genes. Another theory is that infections or asthma in childhood makes airways more sensitive to damage. Some think that deeper inhalation of cigarette smoke may deposit more chemicals in the lungs.
Some people produce too little alpha-1-antitrypsin, a protective enzyme secreted in the lungs. These people are much more likely to develop emphysema at an early age, even without exposure to cigarette smoke.
Following are some of the other risk factors for emphysema:
indoor air pollution, such as smoke from home cooking or home heating fuels
occupational dusts and chemicals
outdoor air pollution, such as motor vehicle exhaust fumes