Asthma

Definition

Asthma is a chronic inflammatory disease of the airways in which periods of relatively free breathing are punctuated by episodes in which breathing becomes difficult. During an attack, inflammation causes the airways to fill with mucus secretions and become obstructed. Asthmatics cough, gasp for air, wheeze, gag, and feel choking sensations as they struggle to breathe. Obstruction to airflow usually responds to a wide range of treatments.

Depending of the type of asthma, attacks may be triggered by environmental factors such as cold temperatures, air pollution, smoke, pollen, dust, mildew, mold, and animal hair or dander. Exercise, allergic reactions, respiratory infections, and emotional stress may also trigger attacks. Like other chronic diseases, asthma can be controlled, but not cured.

According to the American Lung Association, in 1998 there were 26 million Americans asthmatics, 10.6 of whom had had an attack during the past year. About a third of all asthmatics are children under 18. Since asthma is often undiagnosed, these statistics probably under-estimate the true prevalence of the disease.

Description

The lungs of asthmatics are hypersensitive to stimuli that do not affect healthy lungs. Many patients with asthma react to allergens such as pollen, dust mites, or animal dander, but colds, viruses, and environmental irritants such as dust and pollution can also be triggers.

During an asthma attack, cells in the bronchial walls called mast cells release chemicals that force the bronchial muscle to contract in spasms These chemicals, which include histamine, acetylcholine, and a group of substances called leukotrienes, also bring white blood cells into the area, which is a key part of the inflammatory response. This process also stimulates mucus formation. The entire process creates bronchoconstriction, making it difficult for the asthmatic person to breathe.

Asthma usually begins in childhood or adolescence, but it also may first appear in adulthood. While the symptoms may be similar, certain important aspects of asthma are different in children and adults.