Dr. Donald Levy, Allergy, Asthma, and Immunology, Orange County Ca


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Office Location
:
705 W. La Veta Ave.
Suite 101
Orange, CA 92868
(714) 639-7847

 


Asthma

Complete Medical Encyclopedia
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Asthma is an immunological condition that causes inflammation, excessive mucus secretion, and reversible constriction of the smooth muscle in the lung's airway. Asthma can produce wheezing, coughing and shortness
of breath; these symptoms may vary in severity.

An asthma attack may be triggered by a person's
sensitivity to certain substances, exercise, dusts, viral infections and other conditions that produce inflammation of the airways.

Symptoms

A dry cough at night or during physical activity may be
the only symptom of asthma. The initial symptoms of an asthma attack are generally shortness of breath, coughing
or chest tightness. In children, an itching sensation on the chest or neck may be the first hint of an approaching attack. The attacks sometimes have a sudden onset that can rapidly progress to pronounced wheezing and shortness of breath. In other instances, the attack starts slowly and symptoms gradually increase in intensity. An asthma attack may last for several minutes, for several hours, or even for days at a time.

Anxiety may accompany an asthma attack, especially if breathing becomes difficult. In very severe attacks, speaking is difficult and little air moves in or out of the lungs. If a person's air supply becomes seriously restricted, confusion and lethargy can occur, and the skin may turn blue. Emergency medical treatment is essential if these symptoms are present. Patients rarely die, even in cases of severe asthma attacks, if proper treatment is obtained early in the course of the attack.

Causes

The airway inflammation associated with asthma may be triggered by contact with an allergen to which a person is sensitive, by a viral infection, or by strenuous exercise. In some people with defined allergies, asthma may be triggered by an abnormal reaction of the airways to specific stimuli. These stimuli may include pollens, dust mites or animal dander, which certain cells in the airway recognize as allergens. The result is an immune response that causes certain cells to release substances such as histamine and leukotrienes that stimulate the smooth muscles in the airways to contract. Mucus secretion increases; white blood cells, which secrete chemicals that cause an inflammation response, are transported to the area; and the tissues lining the airways become swollen and inflamed. This produces a narrowing of the airways, a condition that is called bronchoconstriction. Bronchoconstriction, which can impede air movement and make breathing difficult, can vary in frequency, duration, and severity.

Asthma also may occur in people who do not have defined allergies. Smoke, cold air, vigorous activity, stress, anxiety, a viral infection of the upper respiratory system, or any combination of these environmental conditions and events may produce similar changes that cause the narrowing of the airways in certain people. The resulting asthma attacks also vary in severity, frequency and duration.

Diagnosis

Asthma can be initially diagnosed on the basis of a description of characteristic symptoms. If a person has narrowed airways at the time he or she visits a doctor, the doctor may hear wheezing, in which case spirometry, a test that measures air movement in and out of the lungs, may confirm bronchoconstriction. Spirometry also may be used to determine the extent of airway obstruction and to monitor asthma treatment.

If the diagnosis of asthma seems likely and spirometry results are normal, the doctor may recommend a trial of bronchodilators. If the symptoms resolve, then asthma is the probable diagnosis. In rare cases in which the diagnosis is uncertain, the doctor may give a small amount of a bronchoconstrictor to inhale. Inhalation at this dosage does not produce narrowing of the airways in a healthy person, but does result in bronchoconstriction in a person with asthma.

Identifying and avoiding asthma triggers is the first line of defense against asthma attacks. In cases in which it is vital to identify the substance that triggers asthma attacks, allergy skin testing may be done. To diagnose exercise-induced asthma, a person is given spirometry tests before and following exercise on a treadmill or stationary bicycle.

Treatment

The most commonly used medications to relieve asthma symptoms are bronchodilators, which stimulate certain receptors in the airway to relax the smooth muscle and dilate (widen) the airways. Bronchodilators may be taken by mouth, by injection or by inhalation. Inhaling devices deposit the medication directly into the airways during an attack and immediately dilate the airways, but in cases of severe bronchoconstriction they may not transport the medication to all the affected airways. Oral bronchodilators can reach all the obstructed airways but act more slowly than inhaled forms and usually have more side effects than inhaled bronchodilators; oral agents must be taken on a regular basis to prevent asthma attacks. They may be taken orally via short-acting tablets, sustained-release capsules, or in syrup form. Bronchodilators can be given by injection, but these are usually used to treat severe asthma attacks.

Inhaled, oral or injected corticosteroids can counteract the inflammatory response and are very effective at controlling symptoms. Inhaled corticosteroids are used most often in those with moderate or severe asthma. When taken over time, these medications gradually act to prevent attacks by reducing inflammation and blocking the sensitivity of the airways to allergens and other stimuli. When severe asthma does not respond to other treatments, long-term oral corticosteroids may be prescribed to control symptoms. Long-term use of oral corticosteroids is limited to the most severely affected people because of the potential for serious side effects, including inhibited wound healing, weakening of the bones, slowed growth in children, bleeding from the stomach, cataracts, increased blood sugar level, weight gain, and mental disturbances. Inhaled corticosteroids used over the long-term do not have these same side effects.

Other medications that may be prescribed to prevent or control asthma include cromolyn sodium and nedocromil, which inhibit the release of inflammatory substances and help prevent airway constriction. The newest medications used to control asthma are leukotriene modifiers (for example, montelukast, zafirlukast and zileuton), which prevent the action of chemicals that cause the inflammation associated with asthma attacks.

Persons diagnosed with asthma are generally prescribed a handheld, metered-dose inhaler that uses pressurized gas to propel the bronchodilator medication, which is inhaled through the mouth into the airways. Inhaled bronchodilators work rapidly to relieve shortness of breath and wheezing by relaxing the smooth muscles of the airways. For people with frequent asthma attacks (more than two to three asthma attacks a week), cromolyn or inhaled corticosteroids may be added as daily medications. Another group of oral medications called leukotriene receptor antagonists is also used to control symptoms. Oral theophylline is prescribed less commonly but can be useful for treating persistent symptoms, particularly nighttime symptoms.

An acute asthma attack should be treated immediately using additional medications or higher doses or different forms of the medications used on an ongoing basis to control or prevent asthma. A handheld inhaler may be used by a person during an asthma attack, or a nebulizer may be used to direct pressurized air through a solution of the medication. The nebulizer produces a continuous mist that can be inhaled. Intravenous asthma medications, including epinephrine or corticosteriods, are sometimes used to treat severe asthma attacks. Oxygen and intravenous fluids also may need to be given, and antibiotics may be necessary if an underlying infection is present.

Excerpted from: Complete Medical Encyclopedia, American Medical Association, 2003.

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