Common Characteristics of Asthma
Asthma is a chronic condition in which the upper airways become obstructed, resulting in wheezing and,
at times, severe difficulty in breathing. It may be triggered by an allergic response to a particular
environmental substance or circumstance--at home, at work, indoors or out--resulting in spasms that
obstruct the breathing apparatus. Allergic asthma is presumed to be an inherited tendency, but the
mechanisms involved are not fully understood. Onset may begin in early childhood, but in many people,
asthma starts in adulthood.
Asthma also may be caused by hypersensitive bronchi or chronic lung disease resulting from smoking.
Attacks in this type of asthma also may be triggered by environmental factors or other causes such as
bacterial infections. Asthma also may occur in people with congestive heart failure or pulmonary edema
(fluid in the lungs).
Attacks vary widely in duration, intensity and frequency. While milder cases are often more of a
nuisance than a threat to health, prompt investigation and treatment are advisable if future
complications are to be avoided. In typical cases, an attack comes on suddenly and is characterized by
distressful efforts to exhale, and as air is taken in, there are spells of coughing and wheezing.
These attacks occur because of the abnormal reaction of the windpipe (trachea) and the bronchial tree to
a precipitating stimulus, which constricts the airway passages in the following way: The smooth muscles
go into spasmodic contractions; there is a swelling of the membranes that line the bronchioles, and the
secretion of mucus increases. Because this bronchial mucus is abnormally sticky, coughing does not expel
it, and it therefore plugs up the smaller air passages.
Since greater difficulty is experienced in breathing out than in breathing in, increasing amounts of stale
air are retained as new breaths are taken. In a severe attack, this leads to a feeling of near suffocation.
An attack may be brief or it may last long enough to demand emergency measures.
