ASTHMA

chronic disease characterized by sporadic attacks of shortness of breath, wheezing, and coughing. The disease is the result of muscular constriction of the bronchi and swelling of the bronchial mucosa. (The bronchi are air passageways branching through the lungs.) Asthma may be caused by an allergic reaction (extrinsic asthma), infection in persons with susceptible bronchi (intrinsic asthma), or malfunction of the autonomic nervous system. Asthma is common, shows a familial incidence, affects all races, and is of generally equal incidence in males and females. In an asthma attack, contraction of the smooth muscle of the bronchial walls is accompanied by swelling of the bronchial tubes and the excessive secretion of mucus by the bronchial glands; the mucus in turn obstructs or plugs the bronchial airways, thus causing the symptoms of an asthma attack. (The distinctive wheezing sound made by asthma sufferers during an attack is caused by the passage of air through narrowed, mucus-filled bronchi.) The release of histamine and acetylcholine seems to play a role in producing the symptoms of asthma attacks, since these chemicals stimulate the smooth muscles of the bronchi to contract. Histamine is in turn released by cells that are affected by an allergic reaction. Thus, although there seems to be a hereditary predisposition present in asthma cases, the actual attacks themselves seem to be triggered by a person's exposure to allergens, i.e., substances to which he is allergic. Asthma attacks usually last from one-half hour to several hours. A person having an attack can be treated by inhaling a vapour of epinephrine (adrenaline), since this substance acts to widen the bronchi and inhibit the mucous glands. The epinephrine may also be injected. A person experiencing a prolonged attack that is resistant to treatment with drugs is said to be in status asthmaticus. Prolonged or frequent attacks of asthma may become dangerous if the sufferer is weakened by fatigue and inadequate nutrition, if his oxygen consumption is too low, or if emphysema develops. The preventive treatment of asthma is aimed at determining which substances the patient is allergic to and preventing his further exposure to them. Extrinsic asthma usually begins before age 30, but intrinsic asthma may have a later onset. Asthmatic patients may be allergic to materials such as pollen, mold spores, feathers, animal dander, and foods; established asthmatics may also experience attacks after exposure to sudden changes in temperature or humidity or both, exertion, emotional stress, strong odours, or smoke. Some 3540 percent of childhood asthma cases improve at puberty; a nearly equal number worsen, however, so that treatment of all childhood cases is necessary.