Asthma

Asthma is a chronic inflammatory disorder of the airways. These airways are passages of the lungs through which air, containing oxygen, passes in and carbon dioxide passes out. The disease occurs because of chronically inflamed airways. The airways become hyper responsive; they become obstructed and airflow is limited. The process of being hyper responsive is characterized by swelling of the airway tissues due to fluid and collection of certain cells. The mucous glands of the airways secrete too much mucous. The combination of swelling, along with too much mucous, causes narrowing and obstruction of the airways.

The severity of asthma attacks varies among individuals, over time, and with the degree of exposure to the triggering factors. Approximately half of all cases of asthma develop during childhood. Another third develop before the age of 40. There are two basic types of asthma--intrinsic and extrinsic. Extrinsic asthma is triggered by allergens while intrinsic asthma is not. Extrinsic asthma, or allergic asthma, is classified as Type I or Type II, depending on the type of allergic response involved. Type I extrinsic asthma is the classic allergic asthma which is common in children and young adults who are highly sensitive to dust and pollen, and is often seasonal in nature. It is characterized by sudden, brief, intermittent attacks of bronchospasms that readily respond to bronchodilators. Type II extrinsic asthma, or allergic alviolitis, develops in adults under age 35 after long exposure to irritants. Attacks are more prolonged than Type I and are more inflammatory. Fever and infiltrates which are visible on chest x-rays often accompany bronchospasm.

Intrinsic asthma has no known immunologic cause and no known seasonal variation. It usually occurs in adults over the age of 35, many of whom are sensitive to aspirin and have nasal polyps. Attacks are often severe and do not respond well to bronchodilators.

A third type of asthma which occurs in otherwise normal individuals is called exercise induced asthma. Individuals with exercise induced asthma experience mild to severe bronchospasms during or after moderate to severe exertion. They have no other occurrences of bronchospasms when not involved in physical exertion. Although the cause of this type of asthma has not been established it is readily controlled by using a bronchodilator prior to beginning exercise.

Airways become inflamed and airflow is limited when the airways are exposed to various stimuli, or triggers. The term triggers will be used as the factors that make asthma worse. Common asthma triggers include:

* Viral infections, such as a "cold"

* Allergen such as:

o Dust mites (in bedding, carpets, and upholstered furnishings)

o Animals with fur

o Cockroach

o Pollens and molds

o Tobacco smoke

o Exercise