Asthma is a chronic (long-lasting) inflammatory disease of the airways. It causes the airways to narrow periodically. This produces wheezing and breathlessness. Obstruction to air flow either stops spontaneously or responds to treatment, but continuing inflammation makes the airways hyper-responsive to stimuli such as cold air, exercise, dust mites, air pollution, stress, and anxiety.

About 10 million Americans have asthma, and the number seems to be increasing. Between 1982-92, the rate rose by 42% and the death rate from asthma increased by 35%.

Changes that take place in the respiratory system of an asthmatic person makethe airways (the bronchi and the smaller bronchioles) reactiveto stimuli that don't affect healthy people. In an asthma attack, the muscletissue in the walls of bronchi spasm, and the cells lining the airways swelland secrete mucus into the air spaces. Both these actions cause the airwaysto narrow which makes breathing more difficult. Many asthmatics react to suchas pollen, house dust mites, or animal dander. These are called allergens. On the other hand, asthma affects many people who do not respond to these allergens in this way.

Asthma often begins in childhood or adolescence, but it also may first appearduring adult years. When asthma begins in childhood, it often is due to a hereditary sensitivity to allergens. Allergens also play a role when adults become asthmatic. Exposure to toxic fumes or industrial pollution can cause adult onset asthma. Other adults may have asthma caused by sinusitis, nasal polyps, or sensitivity to aspirin and related drugs.

Because avoiding or minimizing exposure to allergens is the most effective way of treating asthma, it is important to identify which allergen is causing symptoms. In some people, symptoms are worsened by rhinitis, sinusitis, acid reflux, or respiratory viral infections (colds). Exposure to tobacco smoke ordust can also trigger an asthma attack. In other people, breathing cold air,exercise, and stress trigger attacks.

Besides wheezing and shortness of breath, the person with asthma may cough and feel a tightness in the chest. Wheezing is often loudest when the patient breathes out, in an attempt to expel used air through the narrowed airways. Some asthmatics are free of symptoms most of the time but may occasionally be short of breath (acute asthma). Others spend much time coughing and wheezing or have continual cold-like symptoms (chronic asthma).

Shortness of breath may cause anxiety. The asthmatic may sit upright, lean forward, use the muscles of the neck and chest wall to help breathe and be unable to speak. Confusion and a bluish tint to the skin are signs that emergencytreatment is needed immediately.

Asthma is diagnosed by family history of asthma or allergies and a physical examination. A test called spirometry measures how rapidly air is exhaled andhow much is retained in the lungs. Repeating the test after the patient inhales a drug that widens the air passages (a bronchodilator) shows whether the airway narrowing is reversible, which is a typical finding in asthma.

Often, it is difficult to determine what triggers asthma attacks. Allergy skin testing may be done, although an allergic skin response does not always mean that the allergen is causing the asthma. A chest x ray helps rule out otherrespiratory disorders. People with asthma should periodically have their lung function measured by spirometry to monitor their lung function and responseto treatment.

Drugs used to treat asthma include the anti-inflammatory drugs such as theophylline and bronchodilators such as albuterol. Steroids are also used to blockinflammation and are extremely effective in relieving symptoms of asthma. However, their long-term use can cause numerous unacceptable side-effects

Leukotriene modifiers are a new type of drug that can be used in place of steroids in older children or adults who have a mild degree of asthma that persists. They work by counteracting substances released by white blood cells in the airways that cause the passages to constrict and secrete mucus. Other anti-inflammatory drugs such as cromolyn and nedocromil are used to prevent asthmatic attacks over the long term in children.

Severe asthma attacks should be treated quickly. The patient suffering an acute attack may need extra oxygen. Medication to expand the breathing tubes isinhaled repeatedly or continuously. If the patient does not respond promptlyand completely, a steroid is given. Rarely, it may be necessary to use a mechanical ventilator to help the patient breathe.

Long-term asthma treatment is based using an inhaler that meters a dose of medication to expand the airways. Patients should be taught how to monitor their symptoms so that they will know when an attack is starting. Infants, youngchildren, and the elderly may need special help in managing their asthma.

Most patients with asthma respond well when to drug therapy, and lead relatively normal lives. More than half of affected children stop having attacks bythe time they reach age 21. Many others have less frequent and less severe attacks as they grow older. A minority of patients have progressively more trouble breathing and run the risk of respiratory failure without intensive treatment.

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