asthma: Definition and Much More from Answers.com

Definition

Today asthma is viewed as a chronic (long-lasting) inflammatory disease of the airways. In those susceptible to asthma, this inflammation causes the airways to narrow periodically. This, in turn, produces wheezing and breathlessness, sometimes to the point where the patient gasps for air. Obstruction to air flow either stops spontaneously or responds to a wide range of treatments, but continuing inflammation makes the airways hyper-responsive to stimuli such as cold air, exercise, dust mites, pollutants in the air, and even stress and anxiety.

Description

About 10 million Americans have asthma, and the number seems to be increasing. Between 1982-92, the rate actually rose by 42%. Not only is asthma becoming more frequent, but it also is a more severe disease than before, despite modern drug treatments. In the same 10-year period, the death rate from asthma in the United States increased by 35%.

The changes that take place in the lungs of asthmatic persons makes the airways (the "breathing tubes," or bronchi and the smaller bronchioles) hyper-reactive to many different types of stimuli that don't affect healthy lungs. In an asthma attack, the muscle tissue in the walls of bronchi go into spasm, and the cells lining the airways swell and secrete mucus into the air spaces. Both these actions cause the bronchi to become narrowed (bronchoconstriction). As a result, an asthmatic person has to make a much greater effort to breathe in air and to expel it.

Cells in the bronchial walls, called mast cells, release certain substances that cause the bronchial muscle to contract and stimulate mucus formation. These substances, which include histamine and a group of chemicals called leukotrienes, also bring white blood cells into the area, which is a key part of the inflammatory response. Many patients with asthma are prone to react to such "foreign" substances as pollen, house dust mites, or animal dander; these are called allergens. On the other hand, asthma affects many patients who are not "allergic" in this way.

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

Child-onset asthma

When asthma does begin in childhood, it often does so in a child who is likely, for genetic reasons, to become sensitized to common "allergens" in the environment (atopic person). When these children are exposed to house-dust mites, animal proteins, fungi, or other potential allergens, they produce a type of antibody that is intended to engulf and destroy the foreign materials. This has the effect of making the airway cells sensitive to particular materials. Further exposure can lead rapidly to an asthmatic response. This condition of atopy is present in at least one-third and as many as half of the general population. When an infant or young child wheezes during viral infections, the presence of allergy (in the child itself or a close relative) is a clue that asthma may well continue throughout childhood.

Adult-onset asthma

Allergenic materials may also play a role when adults become asthmatic. Asthma can actually start at any age and in a wide variety of situations. Many adults who are not allergic do have such conditions as sinusitis or nasal polyps, or they may be sensitive to aspirin and related drugs. Another major source of adult asthma is exposure at work to animal products, certain forms of plastic, wood dust, or metals.

— David A. Cramer, MD

n.

A chronic respiratory disease, often arising from allergies, that is characterized by sudden recurring attacks of labored breathing, chest constriction, and coughing.

[Middle English asma, from Medieval Latin, from Greek asthma.]

asthmatic asth·mat'ic (-măt'ĭk) adj. & n.
asthmatically asth·mat'i·cal·ly adv.

An allergic inflammatory disease of the airways, involving mast cells, eosinophils, macrophages, fibroblasts, and neutrophils. Such inflammatory changes are associated with widespread airflow obstruction, which is variable and improves (reverses) spontaneously or with appropriate therapy. Inflammation progresses to increased airway irritability (hyperresponsiveness) induced by the inhalation of allergens, cold air, and occupational factors. Although bronchospasm can be induced immediately after exposure to a specific allergen in an appropriately sensitized recipient, it is the late allergic response that most resembles the inflammatory reaction occurring in asthma. Central to this reaction is the release from mast cells, eosinophils, and lymphocytes of chemical mediators such as histamine, leukotrienes (potent bronchoconstricting agents), and various cytokines which perpetuate the response. Potent neurohumoral agents derived from neural pathways contribute further to the bronchospasm. See also Cytokinins; Hypersensitivity.

Wheezing, nocturnal breathlessness, coughing, and chest tightness often relieved by expectoration are highly suggestive of asthma. Episodes of breathlessness which result from exposure to an irritant (such as cold air) or an allergen (such as dust mites) following exercise or a viral infection and which are reversed spontaneously or with therapy are diagnostic of asthma. Eczema and edema in the folds of the nasal chambers are suggestive of a hereditary allergy, the major predictor of asthma. Objective measures of airflow obstruction which improved spontaneously or with therapy are also central to establishing an asthma diagnosis. Atopy, the genetic predisposition for developing an immunoglobulin-E (IgE) mediated (allergic) response to inhaled environmental allergens, is the strongest predisposing factor for developing asthma. Asthma may be classified, therefore, according to severity, etiology, or pattern of airflow obstruction. It is helpful to differentiate those factors that induce inflammation from those that incite acute bronchospasm in susceptible individuals. The association of an elevated serum IgE and the occurrence of asthma in all age groups, including those who are not atopic, makes antigenic stimulation causal in all instances of asthma. The severity of asthma can best be defined in terms of peak-flow monitoring (monitoring the severity of the allergy). Such evaluations as mild, moderate, and severe are useful in applying therapy in a stepwise manner contingent on severity. See also Immunoglobulin.

Successful management of asthma requires education of the sick individual coupled with the development of a partnership with an asthma management health-care team; assessing and monitoring the severity of asthma, with utilization of objective parameters of assessment (for example, the peak-flow meter, a device that measures the amount of air that enters and leaves the lungs); environmental management to avoid asthma triggers; and establishment of a drug regimen that controls asthma (medications include bronchodilators, which act as relievers, and bronchodilators, which act as preventers), as well as a written plan to prevent the condition from becoming worse. Adequate management of asthma should control the symptoms, prevent asthma attacks, return and maintain pulmonary function as close to normal as possible, maintain normal activity levels including exercise, avoid adverse side effects from the drugs, reduce and prevent irreversible airway changes, and prevent mortality. See also Allergy; Respiratory system disorders.

A respiratory disorder characterized by recurrent attacks of difficulty in breathing (described in medical books as ‘episodic wheezing’), particularly on exhalation. It is caused by an increased resistance to air flow through the respiratory bronchioles (small air tubes leading to the lungs). Sufferers are hypersensitive to a variety of stimuli (e.g. house dust mites; diesel exhaust particulates; and vehicle exhaust gases, such as ozone and nitrogen oxides) which cause the airways to narrow. Asthma may be induced by exercise (see exercise induced asthma) and food allergies. Sports vary in their tendency to induce asthma, with running having a high tendency, cycling a moderate tendency, and gymnastics and swimming a low tendency. Paradoxically, many asthmatics gain relief from bronchospasms by regular exercise, and exercise is now seen as important in the management of asthma. Asthmatic attacks are relieved by a number of drugs, but competitive sports people should be aware that some of these are banned by sports federations because, as well as controlling asthma, they may act as artificial stimulants.

(az′mə)
n

Paroxysmal wheezing and difficulty in breathing resulting from bronchospasms. Frequently has an allergic basis and occasionally an emotional origin. See also status asthmaticus.

Definition

Asthma is a chronic inflammatory disease of the airways in the lungs. This inflammation periodically causes the airways to narrow, producing wheezing and breath-lessness sometimes to the point where the patient gasps for air. This obstruction of the air flow either stops spontaneously or responds to a wide range of treatments. Continuing inflammation makes asthmatics hyper-responsive to such stimuli as cold air, exercise, dust, pollutants in the air, and even stress or anxiety.

Description

Between 16 and 17 million Americans have asthma and the number has been rising since 1980. As many as 9 million U.S. children under age 18 may have asthma. Blacks, Hispanics, American Indians, and Alaskan natives had higher rates of asthma-control problems than whites or Asians in the United States.

The changes that take place in the lungs of asthmatics make their airways (the bronchi and the smaller bronchioles) hyper-reactive to many different types of stimuli that do not affect healthy lungs. In an asthma attack, the muscle tissue in the walls of the bronchi go into spasm, and the cells that line the airways swell and secrete mucus into the air spaces. Both these actions cause the bronchi to narrow, a change that is called bronchoconstriction. As a result, an asthmatic person has to make a much greater effort to breathe.

Cells in the bronchial walls, called mast cells, release certain substances that cause the bronchial muscle to contract and stimulate mucus formation. These substances, which include histamine and a group of chemicals called leukotrienes, also bring white blood cells into the area. Many patients with asthma are prone to react to substances such as pollen, dust, or animal dander; these are called allergens. Many people with asthma do not realize that allergens are triggering their attacks. On the other hand, asthma also affects many patients who are not allergic in this way.

Asthma usually begins in childhood or adolescence, but it also may first appear in adult life. While the symptoms may be similar, certain important aspects of asthma are different in children and adults. When asthma begins in childhood, it often does so in a child who is likely, for genetic reasons, to become sensitized to common allergens in the environment. Such a child is known as an atopic person. In 2004, scientists in Helsinki, Finland, identified two new genes that cause atopic asthma. The discovery might lead to earlier prediction of asthma in children and adults. When these children are exposed to dust, animal proteins, fungi, or other potential allergens, they produce a type of antibody that is intended to engulf and destroy the foreign materials. This has the effect of making the airway cells sensitive to particular materials. Further exposure can lead rapidly to an asthmatic response. This condition of atopy is present in at least one third and as many as one half of the general population. When an infant or young child wheezes during viral infections, the presence of allergy (in the child or a close relative) is a clue that asthma may well continue throughout childhood.

Allergenic materials may also play a role when adults become asthmatic. Asthma can start at any age and in a wide variety of situations. Many adults who are not allergic have such conditions as sinusitis or nasal polyps, or they may be sensitive to aspirin and related drugs. Another major source of adult asthma is exposure at work to animal products, certain forms of plastic, wood dust, metals, and environmental pollution.

Causes & Symptoms

In most cases, asthma is caused by inhaling an allergen that sets off the chain of biochemical and tissue changes leading to airway inflammation, bronchoconstriction, and wheezing. Because avoiding (or at least minimizing) exposure is the most effective way of treating asthma, it is vital to identify which allergen or irritant is causing symptoms in a particular patient. Once asthma is present, symptoms can be set off or made worse if the patient also has rhinitis (inflammation of the lining of the nose) or sinusitis. When, for some reason, stomach acid passes back up the esophagus in a reaction called acid reflux, this condition also can make asthma worse. In addition, a viral infection of the respiratory tract can inflame an asthmatic reaction. Aspirin and drugs called beta-blockers, often used to treat high blood pressure, also can worsen the symptoms of asthma. But the most important inhaled allergens giving rise to attacks of asthma are:

• animal dander
• dust mites
• fungi (molds) that grow indoors

• cockroach allergens
• pollen
• occupational exposure to chemicals, fumes, or particles of industrial materials
• tobacco smoke
• air pollutants

In addition, there are three important factors that regularly produce attacks in certain asthmatic patients, and they may sometimes be the sole cause of symptoms. They are:

• inhaling cold air (cold-induced asthma)
• exercise-induced asthma (in certain children, asthma attacks are caused simply by exercising)
• stress or a high level of anxiety

Wheezing often is obvious, but mild asthmatic attacks may be confirmed when the physician listens to the patient's chest with a stethoscope. Besides wheezing and being short of breath, the patient may cough or report a feeling of tightness in the chest. Children may have itching on their back or neck at the start of an attack. Wheezing often is loudest when the patient exhales. Some asthmatics are free of symptoms most of the time but may occasionally be short of breath for a brief time. Others spend much of their days (and nights) coughing and wheezing until properly treated. Crying or even laughing may bring on an attack. Severe episodes often are seen when the patient gets a viral respiratory tract infection or is exposed to a heavy load of an allergen or irritant. Asthmatic attacks may last only a few minutes or can go on for hours or even days. Being short of breath may cause a patient to become very anxious, sit upright, lean forward, and use the muscles of the neck and chest wall to help breathe. The patient may be able to say only a few words at a time before stopping to take a breath. Confusion and a bluish tint to the skin are clues that the

oxygen supply is much too low and that emergency treatment is needed. In a severe attack, some of the air sacs in the lung may rupture so that air collects within the chest, which makes it even harder to breathe. The good news is that almost always, even patients with the most severe attacks will recover completely.

Diagnosis

Apart from listening to the patient's chest, the examiner should look for maximum chest expansion while taking in air. Hunched shoulders and contracting neck muscles are other signs of narrowed airways. Nasal polyps or increased amounts of nasal secretions are often noted in asthmatic patients. Skin changes, like dermatitis or eczema, are a clue that the patient has allergic problems. Inquiring about a family history of asthma or allergies can be a valuable indicator of asthma. A test called spirometry measures how rapidly air is exhaled and how much is retained in the lungs. Repeating the test after the patient inhales a drug that widens the air passages (a bronchodilator) will show whether the narrowing of the airway is reversible, which is a very typical finding in asthma. Often patients use a related instrument, called a peak flow meter, to keep track of asthma severity when at home.

Frequently, it is difficult to determine what is triggering asthma attacks. Allergy skin testing may be used, although an allergic skin response does not always mean that the allergen being tested is causing the asthma. Also, the body's immune system produces an antibody to fight off the allergen, and the amount of antibody can be measured by a blood test. The blood test will show how sensitive the patient is to a particular allergen. If the diagnosis is still in doubt, the patient can inhale a suspect allergen while using a spirometer to detect airway narrowing. Spirometry also can be repeated after a bout of exercise if exercise-induced asthma is a possibility. A chest x-ray will help rule out other disorders.

Treatment

There are many alternative treatments available for asthma that have shown promising results. One strong argument for these treatments is that they try to avoid the drugs that allopathic treatment (combating disease with remedies to produce effects different from those produced by the disease) relies upon, which can be toxic and addictive. Mainstream journals have reported on the toxicity of asthma pharmaceuticals. A 1995 New Zealand study showed that before 1940, death from asthma was very low, but that the death rate promptly increased with the introduction of bronchodilators. The New England Journal of Medicine in 1992 reported that albuterol and other asthma drugs cause the lungs to deteriorate when used regularly. A 1989 study in the Annals of Internal Medicine showed that respiratory therapists, who are exposed to bronchodilator sprays, develop asthma five times more often than other healthcare professionals, which could imply that the drugs themselves may induce asthma. Theophylline, another popular drug, has been reported to cause personality changes in users. Steroids can also have negative effects on many systems in the body, particularly the hormonal system. Thus, natural and non-toxic methods for treating asthma are the preferred first choice of alternative practitioners, while drugs are used to manage extreme cases and emergencies.

Alternative medicine tends to view asthma as the body's protective reaction to environmental agents and pollutants. As such, the treatment goal is often to restore balance to and strengthen the entire body and provide specific support to the lungs, immune and hormonal systems. Asthma sufferers can help by keeping a diary of asthma attacks in order to determine environmental and emotional factors that may be contributing to their condition.

Alternative treatments have minimal side effects, are generally inexpensive, and are convenient forms of selftreatment. They also can be used alongside allopathic treatments to improve their effectiveness and lessen their negative side effects.

Dietary and Nutritional Therapies

Some alternative practitioners recommend cutting down on or eliminating dairy products from the diet, as these increase mucus secretion in the lungs and are sources of food allergies. Other recommendations include avoiding processed foods, refined starches and sugars, and foods with artificial additives and sulfites. Diets should be high in fresh fruits, vegetables, and whole grains, and low in salt. Asthma sufferers should experiment with their diets to determine if food allergies are playing a role in their asthma. Some studies have shown that a sustained vegan (zero animal foods) diet can be effective for asthma, as it does not contain the animal products that frequently cause food allergies and contain chemical additives. A vegan diet also eliminates a fatty acid called arachidonic acid, which is found in animal products and is believed to contribute to allergic reactions. A 1985 Swedish study showed that 92% of patients with asthma improved significantly after one year on a vegan diet. On the other hand, some people feel weaker on a vegan diet. In addition, many people are allergic to vegetables rather than to meat.

Plenty of water should also be drunk by asthma sufferers, as water helps to keep the passages of the lungs moist. Onions and garlic contain quercetin, a flavonoid (a chemical compound/biological response modifier) that inhibits the release of histamine, and should be a part of an asthmatic's diet. Quercetin also is available as a supplement, and should be taken with the digestive enzyme bromelain to increase its absorption.

As nutritional therapy, vitamins A, C and E have been touted as important. Also, the B complex vitamins, particularly B₆ and B₁₂, may be helpful for asthma, as well as magnesium, selenium, and an omega-3 fatty acid supplement such as flaxseed oil. A good multivitamin supplement also is recommended. In 2004, a study of supplements at Cornell University showed that high levels of beta-carotene and vitamin C along with selenium lowered risk of asthma. However, the same study found that vitamin E had no effect.

Herbal Remedies

Chinese medicine has traditionally used ma huang, or ephedra, for asthma attacks. It contains ephedrine, which is a bronchodilator used in many drugs. However, the U.S. Food and Drug Administration (FDA) issued a ban on the sale of ephedra that took effect in April 2004 because it was shown to raise blood pressure and stress the circulatory system, resulting in heart attacks and strokes for some users. Ginkgo has been shown to reduce the frequency of asthma attacks, and licorice is used in Chinese medicine as a natural decongestant and expectorant. There are many formulas used in traditional Chinese medicine to prevent or ease asthma attacks, depending on the specific Chinese diagnosis given by the practitioner. For example, ma huang is used to treat socalled "wind-cold" respiratory ailments.

Other herbs used for asthma include lobelia, also called Indian tobacco; nettle, which contains a natural antihistamine; thyme; elecampane mullein: feverfew; passionflower: saw palmetto: and Asian ginseng. Coffee and tea have been shown to reduce the severity of asthma attacks because caffeine works as a bronchodilator. Tea also contains minute amounts of theophylline, a major drug used for asthma. Ayurvedic (traditional East Indian) medicine recommends the herb Tylophora asthmatica.

Mind/Body Approaches

Mind/body medicine has demonstrated that psychological factors play a complex role in asthma. Emotional stress can trigger asthma attacks. Mind/body techniques strive to reduce stress and help asthma sufferers manage the psychological component of their condition. A 1992 study by Dr. Erik Peper at the Institute for Holistic Healing Studies in San Francisco used biofeedback, a treatment method that uses monitors to reveal physiological information to patients, to teach relaxation and deep breathing methods to 21 asthma patients. Eighty percent of them subsequently reported fewer attacks and emergency room visits. A 1993 study by Kaiser Permanente in Northern California worked with 323 adults with moderate to severe asthma. Half the patients got standard care while the other half participated in support groups. The support group patients had cut their asthma-related doctor visits in half after two years. Some other mind/body techniques used for asthma include relaxation methods, meditation, hypnotherapy,, mental imaging, psychotherapy, and visualization.

Yoga and Breathing Methods

Studies have shown that yoga significantly helps asthma sufferers, with exercises specifically designed to expand the lungs, promote deep breathing, and reduce stress. Pranayama is the yogic science of breathing, which includes hundreds of deep breathing techniques. These breathing exercises should be done daily as part of any treatment program for asthma, as they are a very effective and inexpensive measure.

Controlled Exercise

Many people believe that those with asthma should not exercise. This is particularly true among parents of children with asthma. In a 2004 study, researchers reported that 20% of children with asthma do not get enough exercise. Many parents believe it is dangerous for their children with asthma to exercise, but physical activity benefits all children, including those with asthma. Parents should work with the child's healthcare provider and any coach or organized sport leader to carefully monitor his or her activities.

Acupuncture

Acupuncture can be an effective treatment for asthma. It is used in traditional Chinese medicine along with dietary changes. Acupressure can also be used as a self-treatment for asthma attacks and prevention. The Lung 1 points, used to stimulate breathing, can be easily found on the chest. These are sensitive, often knotted spots on the muscles that run horizontally about an inch below the collarbone, and about two inches from the center of the chest. The points can be pressed in a circular manner with the thumbs, while the head is allowed to hang forward and the patient takes slow, deep breaths. Reflexology also uses particular acupressure points on the hands and feet that are believed to stimulate the lungs.

Other Treatments

Aromatherapists recommend eucalyptus, lavender, rosemary, and chamomile as fragrances that promote free breathing. In Japan, a common treatment for asthma is administering cold baths. This form of hydrotherapy has been demonstrated to open constricted air passages. Massage therapies such as Rolfing can help asthma sufferers as well, as they strive to open and increase circulation in the chest area. Homeopathy uses the remedies Arsenicum album, Kali carbonicum, Natrum sulphuricum, and Aconite.

Allopathic Treatment

Allopaths recommend that asthma patients should be periodically examined and have their lung functions measured by spirometry. The goals are to prevent troublesome symptoms, to maintain lung function as close to normal as possible, and to allow patients to pursue their normal activities, including those requiring exertion. The best drug therapy is that which controls asthmatic symptoms while causing few or no side effects.

Drugs

The chief methylxanthine drug is theophylline. It may exert some anti-inflammatory effect and is especially helpful in controlling nighttime symptoms of asthma. When, for some reason, a patient cannot use an inhaler to maintain long-term control, sustained-release theophylline is a good alternative. The blood levels of the drug must be measured periodically, as too high a dose can cause an abnormal heart rhythm or convulsions.

Beta-receptor agonists (drugs that trigger cell response) are bronchodilators. They are the drugs of choice for relieving sudden attacks of asthma and for preventing attacks from being triggered by exercise. Some agonists, such as albuterol, act mainly in lung cells and have little effect on the heart and other organs. These drugs generally start acting within minutes, but their effects last only four to six hours. They may be taken by mouth, inhaled, or injected. In 2004, a new lower concentration of albuterol was approved by the FDA for children ages two to 12.

Steroids are drugs that resemble natural body hormones. They block inflammation and are effective in relieving symptoms of asthma. When steroids are taken by inhalation for a long period, asthma attacks become less frequent as the airways become less sensitive to allergens. Steroids are the strongest medicine for asthma, and can control even severe cases over the long term and maintain good lung function. However, steroids can cause numerous side effects, including bleeding from the stomach, loss of calcium from bones, cataracts in the eye, and a diabetes-like state. Patients using steroids for lengthy periods may also have problems with wound healing, may gain weight, and may suffer mental problems. In children, growth may be slowed. Besides being inhaled, steroids may be taken by mouth or injected, to rapidly control severe asthma.

Leukotriene modifiers are among a newer type of drug that can be used in place of steroids, for older children or adults who have a mild degree of persistent asthma. They work by counteracting leukotrienes, which are substances released by white blood cells in the lung that cause the air passages to constrict and promote mucus secretion. Other drugs include cromolyn and nedocromil, which are anti-inflammatory drugs that often are used as initial treatments to prevent long-term asthmatic attacks in children. Montelukast sodium (Singulair) is a drug taken daily that is used to help prevent asthma attacks rather than to treat an acute attack. In 2004, the FDA approved an oral granule formula of Singulair for young children.

If a patient's asthma is caused by an allergen that cannot be avoided and it has been difficult to control symptoms by drugs, immunotherapy may be worth trying. In a typical course of immunotherapy, increasing amounts of the allergen are injected over a period of three to five years, so that the body can build up an effective immune response. There is a risk that this treatment may itself cause the airways to become narrowed and bring on an asthmatic attack. Not all experts are enthusiastic about immunotherapy, although some studies have shown that it reduces asthmatic symptoms caused by exposure to dust mites, ragweed pollen, and cats.

Managing Asthmatic Attacks

A severe asthma attack should be treated as quickly as possible. It is most important for a patient suffering an acute attack to be given extra oxygen. Rarely, it may be necessary to use a mechanical ventilator to help the patient breathe. A beta-receptor agonist is inhaled repeatedly or continuously. If the patient does not respond promptly and completely, a steroid is given. A course of steroid therapy, given after the attack is over, will make a recurrence less likely.

Long-term allopathic treatment for asthma is based on inhaling a beta-receptor agonist using a special inhaler that meters the dose. Patients must be instructed in proper use of an inhaler to be sure that it will deliver the right amount of drug. Once asthma has been controlled for several weeks or months, it is worth trying to cut down on drug treatment, but this tapering must be done gradually. The last drug added should be the first to be reduced. Patients should be seen every one to six months, depending on the frequency of attacks. Starting treatment at home, rather than in a hospital, makes for minimal delay and helps the patient to gain a sense of control over the disease. All patients should be taught how to monitor their symptoms so that they will know when an attack is starting. Those with moderate or severe asthma should know how to use a flow meter. They also should have a written plan to follow if symptoms suddenly become worse, including how to adjust their medication and when to seek medical help. If more intense treatment is necessary, it should be continued for several days. When deciding whether a patient should be hospitalized, the physician must take into account the patient's past history of acute attacks, severity of symptoms, current medication, and the availability of good support at home.

Expected Results

Most patients with asthma respond well when the best treatment or combination of treatments is found and they are able to lead relatively normal lives. Patients who take responsibility for their condition and experiment with various treatments have good chances of keeping symptoms minimal. Having urgent measures to control asthma attacks and ongoing treatment to prevent attacks are important as well. More than one half of affected children stop having attacks by the time they reach 21 years of age. Many others have less frequent and less severe attacks as they grow older. A small minority of patients will have progressively more trouble breathing. Because they run a risk of going into respiratory failure, they must receive intensive treatment.

Prevention

Prevention is extremely important in the treatment of asthma, which includes eliminating all possible allergens from the environment and diet. Homes and work areas should be as dust and pollutant-free as possible. Areas can be tested for allergens and high-quality air filters can be installed to clean the air. If the patient is sensitive to a family pet, removing the animal or at least keeping it out of the bedroom (with the bedroom door closed) is advised. Keeping the pet away from carpets and upholstered furniture, and removing all feathers also helps. To reduce exposure to dust mites, it is recommended to remove wall-to-wall carpeting, keep the humidity low, and use special pillows and mattress covers. Cutting down on stuffed toys, and washing them each week in hot water, is advised for children with asthma. If cockroach allergen is causing asthma attacks, controlling the roaches (using traps or boric acid rather than chemicals) can help.

It is important to not to leave food or garbage exposed. Keeping indoor air clean by vacuuming carpets once or twice a week (with the asthmatic person absent), and avoiding use of humidifiers is advised. Those with asthma should avoid exposure to tobacco smoke and should not exercise outside when air pollution levels are high. When asthma is related to exposure at work, taking all precautions, including wearing a mask and, if necessary, arranging to work in a safer area, is recommended. For chronic sufferers who live in heavily polluted areas, moving to less polluted regions may even be a viable alternative.

Resources

Books

Bock, Steven J. Natural Relief for Your Child's Asthma. New York: HarperPerennial, 1999.

Cutler, Ellen W. Winning the War against Asthma and Allergies. New York: Delmar, 1998.

Periodicals

Allergy and Asthma Magazine. 702 Marshall St., Suite 611. Redwood City, CA 94063. (605) 780-0546.

"Allergy Season Can Mean Trouble." Respiratory Therapeutics Week (April 19, 2004):9.

"Asthma Antioxidants." Better Nutrition (May 2004):26–27.

"Children with Asthma Inactive Due to Parental Health Beliefs, Disease Severity." Obesity, Fitness & Wellness Week (May 1, 2004):8.

"Identification of New Asthma Genes Demonstrates Model for Improved Patient Care." Drug Week (April 30, 2004):27.

McNamara, Daniel. "Singulair." Family Practice News (February 1, 2004):108–109.

"Nine Million U.S. Children Diagnosed With Asthma, New Report Finds." Medical Letter on the CDC & FDA (April 25, 2004):11.

"Patent Granted for Pediatric Asthma Medication." Health & Medicine Week (April 12, 2004):552.

Ressel, Genevieve. "FDA Issues Regulation Prohibiting Sale of Dietary Supplements Containing Ephedra." American Family Physician (March 15, 2004):1343.

"U.S. Asthma Rates on the Rise." Medical Letter on the CDC & FDA (March 28, 2004):11.

Organizations

Asthma and Allergy Foundation of America. 1125 15th St. NW, Suite 502. Washington, DC 20005. 800-7ASTHMA. .

Center for Complementary and Alternative Medicine Research in Asthma, Allergy, and Immunology. University of California at Davis. 3150B Meyer Hall. Davis, CA 95616. (916) 752-6575. .

[Article by: Douglas Dupler; Teresa G. Odle]

Definition

Asthma is a chronic (long-lasting) inflammatory disease of the airways. In people susceptible to asthma, this inflammation causes the airways to narrow periodically. This narrowing, in turn, produces wheezing and breathlessness that sometimes causes the patient to gasp for air. Obstruction to air flow either stops spontaneously or responds to a wide range of treatments, but continuing inflammation makes the airways hyper-responsive to stimuli such as cold air, exercise, dust mites, pollutants in the air, and even stress and anxiety.

Description

The changes that take place in the lungs of people with asthma make the airways (the "breathing tubes," or bronchi and the smaller bronchioles) hyper-reactive to many different types of stimuli that do not affect healthy lungs. In an asthma attack, the muscle tissues in the walls of the bronchi go into spasm, and the cells lining the airways swell and secrete mucus into the air spaces. These two actions cause the bronchi to become narrowed (bronchoconstriction). As a result, a person with asthma has to make a much greater effort to breathe.

Cells in the bronchial walls, called mast cells, release certain substances that cause the bronchial muscles to contract and stimulate mucus formation. These substances, including histamine and a group of chemicals called leukotrienes, also bring white blood cells into the area, which play a key role in the inflammatory response. Many patients with asthma are prone to react to such "foreign" substances as pollen, house dust mites, or animal dander. These are called allergens. An acute asthma attack can begin immediately after exposure to a trigger or several days or weeks later.

When asthma begins in childhood, it often affects a child who is likely, for genetic reasons, to become sensitized to common "allergens" in the environment (atopic person). When these children are exposed to house dust mites, animal proteins, fungi, or other potential allergens, they produce a type of antibody that is intended to engulf and destroy the foreign materials. This makes the airway cells sensitive to particular materials. Further exposure can rapidly lead to an asthmatic response.

Demographics

Asthma affects about 17 million Americans, including nearly five million children. Asthma usually begins in childhood or adolescence, but it also may first appear in adulthood. Asthma is the leading cause of chronic illness in children, accounting for 14 million missed school days annually. It is the third-ranking cause of hospitalization among children under age 15.

Asthma affects as many as 10–12 percent of children in the United States and the number has been steadily increasing. Since 1980, asthma has increased by 160 percent among children at least four years of age. Asthma is becoming more frequent, and—despite modern drug treatments—it is more severe than in the past. Some experts suggest this is due to increased exposure to allergens such as dust, air pollution, second-hand smoke, and industrial components.

Asthma can begin at any age, but most children experience their first symptoms by the time they are five years old. Boys have a higher incidence of asthma than girls, and the disease is more prevalent in African American children. Children living in inner cities, low-income populations, and minorities have disproportionately higher morbidity and mortality due to asthma.

Causes and Symptoms

Causes

About 80 percent of childhood asthma cases are caused by allergies. In most cases, inhaling an allergen sets off the chain of biochemical and tissue changes leading to airway inflammation, bronchoconstriction, and wheezing characteristic of asthma. Because avoiding (or at least minimizing) exposure is the most effective way of treating asthma, it is vital to identify the allergen or irritant that is causing symptoms in a particular child.

Once asthma is present, symptoms can be triggered or made worse if the child also has rhinitis (inflammation of the lining of the nose) or sinusitis. Gastroesophageal reflux disease (GERD), a condition that causes stomach acid to pass back up the esophagus, can worsen asthma. Many pulmonary infections in early childhood, including those due to Chlamydia pneumoniae,Mycoplasma pneumoniae, and respiratory syncytial virus, have been linked with an increased risk for wheezing and asthma. Aspirin and a class of drugs called beta-blockers (often used to treat high blood pressure) can also worsen the symptoms of asthma. Foggy and cloudy environments have been noted to aggravate asthma, and obesity facilitates asthma, but does not cause it.

The most important inhaled allergens and triggers contributing to attacks of asthma are:

• animal dander
• smites in house dust
• fungi (molds) that grow indoors
• mold spores that grow outdoors
• cockroach allergens
• tree, grass, and weed pollen
• occupational exposure to chemicals, fumes, or particles of industrial materials in the air
• strong odors, such as from perfume
• wood smoke

Inhaling tobacco smoke (from secondhand smoke or smoking) can irritate the airways and trigger an asthmatic attack. Air pollutants can have a similar effect.

There are three important factors that regularly produce attacks in certain patients with asthma, and they may sometimes be the sole cause of symptoms. They are:

• humidity and temperature changes, especially inhaling cold air
• exercise (in certain children, asthma is caused simply by exercising, and is called exercise-induced asthma)
• stress, strong emotions, or a high level of anxiety

Risk Factors

There are many risk factors for childhood asthma, including:

• presence of allergies
• family history of asthma and/or allergies
• frequent respiratory infections
• low birth weight
• mother's exposure to tobacco smoke during pregnancy and/or child's exposure after birth
• wheezing with upper respiratory infections

Symptoms

Wheezing is often very obvious, but mild asthmatic attacks may be confirmed when the physician listens to the patient's chest with a stethoscope. Wheezing is often loudest when the child breathes out, in an attempt to expel used air through the narrowed airways. Besides wheezing and shortness of breath, the child may cough and experience pain or pressure in the chest. The child may have itching on the back or neck at the start of an attack. Infants may have feeding problems and may grunt while sucking or feeding. Tiring easily or becoming irritated are other common symptoms.

Some children with asthma are free of symptoms most of the time, but may occasionally experience brief periods during which they are short of breath. Others spend much of their days (and nights) coughing and wheezing, until the asthma is properly treated. Crying or even laughing may bring on an attack. Severe episodes, which are less common, may be seen when the patient has a viral respiratory tract infection or is exposed to a heavy load of an allergen or irritant. Asthmatic attacks may last only a few minutes or can go on for hours or even days (a condition called status asthmaticus).

Asthma symptoms can be classified as:

• Mild intermittent: Symptoms occur twice a week or less; nighttime symptoms occur twice a month or less; symptoms are brief and last a few hours to a few days; no symptoms occur between more severe episodes.
• Mild persistent: Symptoms occur more than twice a week but not every day; nighttime symptoms occur more than twice a month; episodes are severe and sometimes affect activity.
• Moderate persistent: Symptoms occur daily; nighttime symptoms occur more than once a week; quick-relief medication is used daily; symptoms affect daily activities; severe episodes occur twice a week or more and last for days.
• Severe persistent: Symptoms occur continually throughout the day and frequently at night; symptoms affect daily activities and cause the patient to limit activities.

Shortness of breath may cause a patient to become very anxious, sit upright, lean forward, and use the neck or chest wall muscles to help with breathing. These symptoms require emergency attention. In a severe attack that lasts for some time, some of the air sacs in the lung may rupture so that air collects within the chest. This makes it even harder to breathe in adequate amounts of air.

Almost always, even patients with the most severe attacks will recover completely.

When to Call the Doctor

If a child has the following symptoms, the parent should contact the child's pediatrician:

• inability to participate in normal activities
• missed school due to asthma symptoms
• symptoms that do not improve about 15 minutes after initial treatment with medication
• signs of infection such as increased fatigue or weakness, fever or chills, sore throat, coughing up mucus, yellow or green mucus, sinus drainage, nasal congestion, headaches, or tenderness along the cheekbones

If the parent is unsure about what action to take to treat the child's symptoms, he or she should call the child's doctor.

The parent or caregiver should seek emergency care by calling 911 in most areas when the child has these symptoms or conditions:

• bluish skin tone
• bluish coloration around the lips, fingernail beds, and tongue
• severe wheezing
• uncontrolled coughing
• very rapid breathing
• inability to catch his or her breath
• tightened neck and chest muscles due to breathing difficulty
• inability to perform a peak expiratory flow
• feelings of anxiety or panic
• pale, sweaty face
• difficulty talking
• difficulty walking
• confusion
• dizziness or fainting
• chest pain or pressure

Diagnosis

Early diagnosis is critical to proper asthma treatment and management. Asthma may be diagnosed by the child's primary pediatrician or an asthma specialist, such as an allergist.

The diagnosis of asthma may be strongly suggested when the typical symptoms and signs are present, including coughing, wheezing, shortness of breath, rapid breathing, or chest tightness. The physician will question the child (if old enough to provide an accurate history of symptoms) or parent about his or her physical health (the medical history), perform a physical examination, and perform or order certain tests to rule out other conditions.

The medical and family history help the physician determine if the child has any conditions or disorders that might be the cause of asthma. A family history of asthma or allergies can be a valuable indicator of asthma and may suggest a genetic predisposition to the condition. The physician will ask detailed questions about the child's symptoms, including when they first occurred, what seems to cause them, the frequency and severity, and how they are being managed.

During the physical exam, the pediatrician will listen to the patient's chest with a stethoscope to evaluate distinctive breathing sounds. He or she also will look for maximum chest expansion during inhalation. Hunched shoulders and contracting neck muscles are signs of narrowed airways. Nasal polyps or increased amounts of nasal secretions are often noted in patients with asthma. Skin changes, like atopic dermatitis or eczema, may demonstrate that the patient has allergic problems.

When asthma is suspected, the diagnosis can be confirmed using certain respiratory tests. Spirometry is a test that measures how rapidly air is exhaled and how much air is retained in the lungs. Usually the child should be at least five years of age for this test to be successful. During the test, the child exhales and the spirometer measures the airflow, comparing lung capacity to the normal range for the child's age and race. The child then inhales a drug that widens the air passages (a short-acting bronchodilator) and the doctor takes another measurement of the lung capacity. An increase in lung capacity after taking this medication often indicates the asthma symptoms are reversible (a very typical finding in asthma). The spirometer is similar to the peak flow meter that patients use to keep track of asthma severity at home.

Often, it is difficult to determine what is triggering asthma attacks. Allergy skin testing may be performed, especially if the doctor suspects the child's symptoms are persistent. An allergic skin response does not always mean that the allergen being tested is causing the asthma. Also, the body's immune system produces an antibody to fight off the allergen. The amount of antibody can be measured by a blood test that will show how sensitive the patient is to a particular allergen. If the diagnosis is still in doubt, the patient can inhale a suspect allergen while using a spirometer to detect airway narrowing. Spirometry can also be repeated after a bout of exercise if exercise-induced asthma is a possibility. A chest x ray will help rule out other disorders.

Treatment

Once asthma is diagnosed, a treatment plan should be initiated as quickly as possible to manage asthma symptoms.

In most cases, asthma treatment is managed by the child's pediatrician. Referral to an asthma specialist should be considered if:

• There has been a life-threatening asthma attack or severe, persistent asthma.
• Treatment for three to six months has not met its goals.
• Some other condition, such as nasal polyps or chronic lung disease, complicates the asthma.
• Special tests, such as allergy skin testing or an allergen challenge, are needed.
• Intensive steroid therapy has been necessary.

The first step in bringing asthma under control is to reduce or avoid exposure to known allergens or triggers as much as possible. Treatment goals for all patients with asthma are to prevent troublesome symptoms, maintain lung function as close to normal as possible, avoid emergency room visits or hospitalizations, allow participation in normal activities—including exercise and those requiring exertion—and improve the quality of life.

Medications

The best drug treatment plan will control asthmatic symptoms while causing few or no side effects. The child's doctor will work with the parent to determine the drugs that are most appropriate and may be the most effective, based on the severity of symptoms. Age and the presence of other medical conditions may affect the drugs selected.

Two types of asthma medications include short-acting, quick relief, medications and long-acting, controller, medications. Quick relief medications are used to treat asthma symptoms when they occur. They relieve symptoms rapidly and are usually taken only when needed. Long-acting medications are preventative and are taken daily to help a patient achieve and maintain control of asthma symptoms.

Asthma treatment guidelines may be based on these symptom classifications:

• Mild intermittent: No daily medication is needed but a short-acting beta2 agonist may be used when needed to treat symptoms.
• Mild persistent: Daily long-term medication may be prescribed.
• Moderate persistent: Two medications may be prescribed, including a long-term medication to control inflammation and a short-acting medication to use when symptoms are more severe.
• Severe persistent: Multiple long-term control medications are required.

When asthma symptoms worsen, medication is increased. When asthma symptoms are controlled, less medication is needed. It is very important to discuss any desired changes to the medication schedule with the doctor. The medication dose should never be changed without the doctor's approval. The condition can worsen if certain medications are not taken.

Inhaled medications have a special inhaler that meters the dose. The inhaler may have a spacer that holds the burst of medication until it is inhaled. Patients will be instructed on how to properly use an inhaler to ensure that it will deliver the right amount of medication.

A home nebulizer, also known as a breathing machine, may be used to deliver asthma medications at home. The nebulizer changes medication from liquid form to a mist. The child wears a face mask to breathe in the medications. Nebulizer treatments generally take seven to 10 minutes.

Quick relief medications include short-acting, inhaled beta2 agonists and anticholinergics. Long-acting medications include leukotriene modifiers, mast cell stabilizers, inhaled and oral corticosteroids, long-acting beta2 agonists, and methylxanthines.

SHORT-ACTING BETA-2 AGONISTS. These drugs, which are bronchodilators, open the airways by relaxing the muscles around the airways that have tightened (bronchospasm). The short-acting forms of beta-receptor agonists are the best choice for relieving sudden attacks of asthma and for preventing attacks triggered by exercise. These drugs generally start acting within minutes, but their effects last only four to six hours (although longer-acting forms are being developed). They may be taken by mouth, inhaled, or injected.

ANTICHOLINERGICS. Anticholinergics are medications that open the airways by relaxing the muscle bands that tighten around the airways. They also suppress mucus production. They do not provide immediate relief, but can be used to control severe attacks when added to an inhaled beta-receptor agonist.

LEUKOTRIENE MODIFIERS. Leukotriene modifiers, also called antileukotrienes, can be used in place of steroids for older children who have a mild degree of asthma that persists. They work by counteracting leukotrienes, substances released by white blood cells in the lung that cause the air passages to constrict and promote mucus secretion.

MAST CELL STABILIZERS. Available only in inhaled form, mast cell stabilizers, such as cromolyn and nedocromil, prevent asthma symptoms. These anti-inflammatory drugs are often given to children as the initial treatment to prevent asthmatic attacks over the long term. They can also prevent attacks when given before exercise or when exposure to an allergen cannot be avoided. They are not effective until three to four weeks after therapy is started. These medications need to be taken two to four times a day.

STEROIDS. These drugs, which resemble natural body hormones, block inflammation. Steroids are extremely effective in relieving asthma symptoms and can control even severe cases over the long term while maintaining good lung function. When steroids are taken by inhalation for a long period, asthma attacks become less frequent as the airways become less sensitive to allergens. Besides being inhaled, steroids may be taken by mouth or injected, to rapidly control severe asthma. Steroids are the strongest class of asthma medications and can cause numerous side-effects, including bleeding from the stomach, loss of calcium from bones, cataracts in the eye, and a diabetes-like state. Patients using steroids for lengthy periods also may have problems with wound healing, weight gain, and mental disorders. In children, growth may be slowed. To prevent serious side effects, the child will have periodic monitoring tests.

LONG-ACTING BETA-2 AGONISTS. Long-acting beta-2 agonists are used for better control—not relief—of asthma symptoms. The medications take longer to work and the effects last longer, up to 12 hours.

METHYLXANTHINES. Theophylline is the chief methylxanthine drug. It may exert some anti-inflammatory effect, and is especially helpful in controlling nighttime symptoms of asthma. If a patient cannot use an inhaler to maintain long-term control, sustained-release theophylline is a good alternative. The blood levels of the drug must be measured periodically, as too high of a dose can cause an abnormal heart rhythm or convulsions.

OTHER DRUGS. Some inhalers contain a combination of two different medications that can be delivered together to shorten treatment times and decrease the number of inhalers that need to be purchased. Clinical trials are continuously evaluating new asthma medications.

IMMUNOTHERAPY. If a patient's asthma is caused by an allergen that cannot be avoided, or if medications have not been effective in controlling symptoms, immunotherapy (also called allergy shots) may be considered. Immunotherapy is helpful when symptoms tend to occur throughout all or most of the year. Typically, increasing amounts of the allergen are injected over a period of three to five years, so that the body can build up an effective immune response. There is a risk that this treatment may cause the airways to become narrowed and bring on an asthmatic attack.

An international conference, Immunotherapy in Allergic Asthma, hosted by the American College of Allergy, Asthma, and Immunology (ACAII) in 2000 concluded that immunotherapy is an effective treatment for allergic asthma and can prevent the onset of asthma in children with allergic rhinitis. The Preventive Allergy Treatment study, published in 2002, confirmed the ACAII conference conclusions, documenting that immunotherapy reduces the risk of developing asthma and reduces lung airway inflammation in children with hay fever, a condition that predisposes them to asthma.

Managing Asthmatic Attacks

Urgent measures to control asthma attacks and ongoing treatment to prevent attacks are equally important. No matter how severe a person's asthma, quick-relief medications must be readily available to treat acute symptoms. If the patient's asthma symptoms are present most of the time, an anti-inflammatory medication should be used regularly.

A severe asthma attack should be treated as quickly as possible. It is most important for a patient suffering an acute attack to be given extra oxygen. Rarely, it may be necessary to use a mechanical ventilator to help the patient breathe. A beta-receptor agonist is inhaled repeatedly or continuously. A steroid is given if the patient's symptoms do not improve promptly and completely. Steroids also may help if a viral infection caused severe asthmatic symptoms. A course of steroid therapy, given after the attack is over, will make a recurrence less likely.

Starting treatment at home, rather than in a hospital, minimizes delays and helps the patient gain a sense of control over the disease. When deciding whether a patient should be hospitalized, the past history of acute attacks, severity of symptoms, current medication, and availability of adequate support at home must be taken into account.

Maintaining Control

Children with asthma should follow up with their doctor every one to six months, depending on the frequency of attacks. During the follow-up visits, the child's lung function should be measured by spirometry to make sure treatment goals are being met. Once asthma has been controlled for several weeks or months, the child's physician may adjust the medication dosage. If there is no clear improvement with the current treatment plan, another treatment plan should be established.

All patients with asthma should learn how to monitor their symptoms so that they will know when an attack is starting. Symptoms can be monitored with a peak flow meter (also called a peak expiratory flow meter). To effectively follow the instructions for using a peak flow meter, the child should be at least five years old. The peak flow meter measures the child's airflow when he or she blows into it quickly and forcefully. The peak flow meter can be used to determine when to call the doctor or seek emergency care.

Knowing the child's allergens or triggers will help parents reduce exposure by making improvements in the home environment. Specific guidelines may include reducing indoor humidity, using allergen-impermeable bedding covers, minimizing the use of carpet and upholstered furniture, and minimizing pet exposure. For more information, see the Prevention section.

All patients with asthma should have a written action plan to follow if symptoms suddenly become worse, including how to adjust medication and when to seek medical help. A Northwestern University study indicates that asthma symptoms and the need for emergency medications in children can be greatly reduced by using a planned-care method. This method involves regularly scheduled visits with specially trained nurses to help the patient and family learn how to anticipate and improve the management of asthma symptoms.

The health care provider should write out an asthma treatment plan for the child's school personnel or care providers. The plan should detail the early warning signs of an asthma attack, what medications the student uses and how they are taken, and when to contact the doctor or seek emergency care. Children with asthma often need medication at school to control acute symptoms or to prevent exercise-induced attacks. Proper management will usually allow a child to take part in play activities. Only as a last resort should activities be limited.

Alternative Treatment

Alternative and complementary therapies include approaches considered to be outside the mainstream of traditional health care. Alternative treatments for asthma include yoga to control breathing and relieve stress and acupuncture to reduce asthma attacks and improve lung function. Biofeedback, which teaches patients how to direct mental thoughts to influence physical functions, may be helpful for some patients. For example, learning to increase the amount of air inhaled may help some patients reduce fear and anxiety. Some Chinese traditional herbs, such as ding-chan tang, have been thought to help decrease inflammation and relieve bronchospasm.

Before learning or practicing any particular technique, it is important for the parent or caregiver and child to learn about the therapy, its safety and effectiveness, potential side effects, and the expertise and qualifications of the practitioner. Although some practices are beneficial, others may be harmful to certain patients.

Relaxation techniques and dietary supplements should not be used as a substitute for medical therapies prescribed by a doctor. Parents should discuss these alternative treatments with the child's doctor to determine the techniques and remedies that may be beneficial.

Nutritional Concerns

Some children have reportedly experienced improved symptoms by limiting dairy products and sugar in the diet. Some studies show that vitamin C helps improve asthma symptoms.

Food additives may trigger asthma symptoms in some children, although this is rare. If the parent suspects that certain foods trigger asthma symptoms in the child, the pediatrician may recommend keeping a food diary for a few weeks to identify problematic foods. Allergy skin testing may be recommended to rule out foods that may trigger asthma symptoms.

Prognosis

Although there is no cure for asthma, it can be treated and managed. Most patients with asthma respond well and are able to lead relatively normal lives when the best drug or combination of drugs is found. Asthma should not be a progressive, disabling disease; a child with asthma can have normal or near-normal lung function with the proper treatment.

Some children stop having attacks as they grow and their airways get bigger. About 50 percent of children have less frequent and less severe attacks as they grow older. However, symptoms can recur when the child reaches his or her thirties or forties.

A small number of patients will have progressively more difficulty breathing. These patients have an increased risk of respiratory failure, and they must receive intensive treatment. Asthma can be a deadly disease if it is not managed properly; an estimated 5,000 people die each year from asthma or its complications.

Prevention

Prolonged breastfeeding in infants for six to 12 months has been shown to reduce the child's likelihood for developing persistent asthma.

Minimizing Exposure to Allergens

There are a number of ways parents can reduce or prevent a child's exposure to the common allergens and irritants that provoke asthmatic attacks:

• If the child is sensitive to a family pet, the pet should be removed or kept out of the child's bedroom (with the bedroom door closed). The pet should be kept away from carpets and upholstered furniture. All products made from feathers should be removed. An air filter should be used on air ducts in the child's room.
• To reduce exposure to house dust mites, wall-to-wall carpeting should be removed, humidity should be kept down, and special pillow and mattress covers should be used. The number of stuffed toys should be reduced, and they should be washed in hot water weekly. Bedding should also be washing weekly in hot water, and dried in a dryer on the hot setting. The child should not be allowed to sleep on upholstered furniture. Carpets should be removed from the child's bedroom.

• If cockroach allergen is causing asthma attacks, the roaches should be killed (using poison, traps, or boric acid rather than chemicals). Food or garbage should not be exposed.
• Indoor air may be kept clean by vacuuming carpets once or twice a week (with the child absent), avoiding humidifiers, and using air conditioning during warm weather (so that windows remain closed).
• To reduce exposure to mold, indoor humidity should be decreased to less than 50 percent, leaky faucets and pipes should be repaired, and vaporizers avoided.
• Family members should quit smoking and others should not be allowed to smoke in the house or near the child.
• The child should not exercise outdoors when air pollution levels are high.

Parental Concerns

Parents should take an open and honest approach when explaining asthma to their child. They should explain that asthma does not define or limit the child. The success of the child's treatment plan will depend on parental guidance and support. As a child ages, the responsibility for personal asthma management can be increased. For example, toddlers can mimic treatment on a toy or doll; preschoolers can help parents in peak flow monitoring and discuss symptoms with them; schoolaged children can begin to take medications on their own (while supervised); and adolescents can be nearly independent in following the structured management plan.

Parents should stress the consequences of improper symptom management with their child. The main concern with older children is peer pressure and the desire to fit in; therefore, symptoms may not be reported accurately and medications may not be taken to avoid comments from peers or appearing different. Parents may want to counteract peer pressure by offering a contract that outlines the management plan and lists specific rewards and consequences.

Parents should work with school personnel to foster a supportive environment that so the child's symptoms can be managed properly. A specific action plan can be developed for school by the child's doctor. Parents should inform school personnel about the child's specific allergens and asthma triggers so steps can be taken to help the child avoid them at school. Students who are able to recognize symptoms requiring medication and know how to use their inhaler properly should be permitted to keep the medication with them. For younger children, parents must ensure that school personnel know how to administer the child's medications.

Asthma should not be used as an excuse to avoid exercise. Sometimes children with asthma avoid school activities because they are afraid of being embarrassed if symptoms occur. Parents should encourage athletic or physical activity participation and talk to gym teachers or coaches to ensure they understand the child's symptoms and treatment protocol. They should make sure the child knows what to do if exercise causes symptoms. Swimming is generally well-tolerated by many people with asthma because it is usually performed in a warm, moist environment. Other activities that involve brief, intermittent periods of exertion, such as volleyball, gymnastics, baseball, walking, and wrestling are usually well-tolerated. Cold-weather sports, such as skiing, ice skating, or hockey, may be not be tolerated as well. The child's doctor can provide specific exercise recommendations and guidelines.

See also Allergy shots.

Resources

Books

American Medical Association. The American Medical Association Essential Guide for Asthma (Better Health for 2003) Pocket, 2000.

Fanta, Christopher H., et al. The Harvard Medical School Guide to Taking Control of Asthma. New York, NY: Free Press, 2003.

Wolf, Rauol. Essential Pediatric Allergy, Asthma, and Immunology. New York, NY: McGraw-Hill Professional, 2004.

Organizations

Allergy and Asthma Network/Mothers of Asthmatics America, Inc. 2751 Prosperity Ave., Suite 150, Fairfax, VA 22031. (800) 878-4403. Web site: www.aanma.org..

American Academy of Allergy, Asthma and Immunology (AAAAI). 611 E. Wells St., Milwaukee, WI 53202. (800) 822-ASTHMA or (414) 272-6071. Web site: www.aaaai.org.

American College of Asthma, Allergy and Immunology (AACI). 85 W. Algonquin Rd., Suite 550, Arlington Hts., IL 60005. (800) 842-7777. Web site: www.aaci.org..

American Lung Association. 1740 Broadway, New York, NY 10019. (800) 586-4872. Web site: www.lungusa.org..

Asthma and Allergy Foundation of America. 1233 20th Street, NW, Suite 402, Washington, DC 20036. (800) 727-8462 or (202) 466-7643. Web site: www.aafa.org.

National Asthma Education Program. National Heart, Lung and Blood Institute Information Center. P.O. Box 30105, Bethesda, MD 20824-0105. (301) 592-8573. Web site: www.nhlbi.nih.gov/about/naepp/.

National Institute of Allergy and Infectious Diseases. NIAID Office of Communications and Public Liaison, Building 31, Room 7A-50, 31 Center Dr., MSC 2520, Bethesda, MD 20892-2520. Web site: www.niaid.nih.gov.

[Article by: David A. Cramer, M.D. Angela M. Costello]

Asthma is a common chronic lung disease characterized by a narrowing of the airways, resulting in obstruction of the flow of air and difficulty in breathing. The airflow obstruction is partially or completely reversible in most patients. Different designations of asthma include bronchial asthma, exercise-induced asthma, drug-induced asthma, occupational asthma, and cardiac asthma (airway narrowing in the setting of congestive heart failure). This discussion focuses primarily on bronchial asthma, a chronic inflammatory disorder of the airways (both the larger "bronchi" and the smaller "bronchioles"), resulting in airflow obstruction and increased sensitivity (responsiveness) of the airways to a variety of stimuli ("bronchial hyperreactivity").

About 15 million Americans, a third of whom are children, suffer from asthma, and more than 5,000 people die from it each year. The condition accounts for an estimated 100 million days of restricted activity and 470,000 hospitalizations annually in the United States. Over the last three to four decades both the prevalence and the death rate from asthma in the United States and many other developed countries have increased. In the United States, the increases in death rates have been higher in women than in men and higher in blacks than in whites.

The most important risk factor to develop bronchial asthma is atopy, an inherited predisposition to have allergies. An acute attack of asthma may occur if an atopic individual inhales allergy-provoking substances (allergens) such as ragweed, cat dander, or house dust. A variety of cells are involved in the asthmatic inflammatory reaction in the airway walls, including neutrophils, eosinophils, lymphocytes, mast cells, and macrophages. These cells release mediators (chemicals such as "cytokines") that provoke the inflammatory process. Asthma also occurs in people without allergies.

During an acute episode of asthma, bronchial narrowing ("bronchoconstriction") results from the buildup of plugs of mucus and cellular debris in the lumen, contraction of smooth-muscle cells ringing the airways, and inflammation and edema of the mucosa. Permanent changes in the airway, including enlargement of the submucosal mucous glands, proliferation of mucus-secreting cells and smooth-muscle cells, and deposition of fibrous tissue in the mucosa, may occur in chronic asthma, a process known as "airway remodeling."

The degree of airflow limitation in patients with asthma is measured by performing breathing tests (pulmonary function tests) such as spirometry and the recording of peak expiratory flow rates (PEFRs). This requires the patient to take in as deep a breath as possible and blow it out with maximum effort into a recording instrument. Obstructive dysfunction is detected if airflow rates are significantly less than predicted values. Partial or complete reversibility of the obstructive dysfunction is possible in most cases after the inhalation of a medication (e.g., albuterol) that dilates the airways. Between episodes of asthma, airflow rates may be normal. However, a patient who has had asthma for many years may display persistent and irreversible obstructive dysfunction as a result of airway remodeling. Spirometry is also employed in bronchial-provocation testing to determine if an individual with suspected asthma has bronchial hyperreactivity (an unusual degree of airway sensitivity to challenges such as exercise or the inhalation of dilute solutions of chemicals such as methacholine).

Patients with asthma suffer from shortness of breath, wheezing, chest tightness, and cough. These symptoms, which may be episodic or chronic, are often worse early in the morning and may disrupt sleep. Asthma often develops in childhood, but it may appear at any age. Episodes of asthma may be spontaneous, but more commonly they are "triggered" by various stimuli, such as inhaling allergens or nonspecific airway irritants (e.g., dusts, smoke, fumes, cold air), upper or lower respiratory tract infections, exercise, certain medications, and exposure to chemicals and other substances in the workplace. The frequency and severity of symptoms vary greatly from patient to patient and tend to be less episodic and more persistent with increasing age.

The diagnosis of bronchial asthma depends upon a medical history of one or more asthma symptoms, evidence of airflow limitation on physical examination or pulmonary function testing, and demonstration of some degree of reversibility of airflow obstruction. Other conditions that mimic asthma must be excluded. These include acute or chronic bronchitis, emphysema, bronchiectasis, cystic fibrosis, upper airway obstruction from various causes, abnormal function of the vocal cords, aspiration, lung cancer, congestive heart failure, pulmonary thromboembolism (blood clots in the pulmonary artery), and even certain psychiatric disorders.

Asthma is classified according to the severity and frequency of its symptoms and the results of pulmonary function tests. Mild intermittent asthma is managed by treating the occasional symptoms with inhaled bronchodilators, called beta₂-agonists. Persistent asthma is treated with daily anti-inflammatory drugs, especially inhaled corticosteroids, often in combination with one or more inhaled or oral bronchodilator drugs. A newer class of drugs called leukotriene modifiers is employed to manage some patients with persistent asthma. Severe persistent asthma requires the daily use of several medications, including oral corticosteroids such as prednisone. Acute, severe asthma may require the patient to be hospitalized to manage acute respiratory failure with supplemental oxygen and even respiratory support on a mechanical ventilator.

Patient education, environmental control, smoking cessation, and avoidance of factors known to provoke attacks are the mainstays of prevention. The importance of stopping smoking cannot be overemphasized. Patients with asthma must reduce exposure to allergens (such as house dust mites and animal danders), eliminate certain medications (such as beta-blocker drugs and aspirin), and avoid exposure to indoor and outdoor air pollutants. A diagnosis of occupational asthma requires that steps be taken to curtail workplace exposure to offending agents. Annual vaccination against influenza virus infection is recommended for patients with persistent asthma.

Fortunately, most patients with asthma respond well to appropriate medical management. Anti-inflammatory therapy for persistent asthma and immediate treatment for acute, severe attacks are essential steps to reduce morbidity and mortality from the disease. Death from bronchial asthma is considered to be preventable.

(SEE ALSO: Chronic Respiratory Diseases; Emphysema; Pulmonary Function)

Bibliography "Drugs for Asthma." The Medical Letter on Drugs and Therapeutics 41(2000):19–24.

McFadden, E. R., Jr. (1998) "Asthma." In Harrison's Principles of Internal Medicine, 14th edition, ed. A. S. Fauci et al. New York: McGraw-Hill.

McFadden, E. R., Jr., and Warren E. L. (1997). "Observations on Asthma Mortality." Annual of Internal Medicine 127:142–147.

National Asthma Education Program (1997). "Expert Panel Report 2: Guidelines for the Diagnosis and Management of Asthma." Bethesda, MD: National Heart, Lung, and Blood Institute. Available at http://www.nhlbi.nih.gov/nhlbi/lung/asthma/prof/asthgdln.htm.

Woolcock, A. J., and Barnes, P. J. (2000). "Asthma: The Important Questions. Part 4." American Journal of Respiratory and Critical Care Medicine 161(3):S157– S217.

— JOHN L. STAUFFER

Chronic disease with attacks of shortness of breath, wheezing, and coughing from constriction and mucous-membrane swelling in the bronchi (air passageways in the lungs). It is caused primarily by allergy or respiratory infection. Secondhand smoke can cause asthma in children. Asthma is common and runs in families; predisposition may be hereditary. In established asthmatics, exercise, stress, and sudden changes in temperature or humidity can bring on attacks. Attacks usually last from a half hour to several hours; severe attacks can be fatal. Corticosteroids can control asthma; injections of epinephrine can relieve acute attacks. Prevention involves avoiding exposure to allergens.

For more information on asthma, visit Britannica.com.

A respiratory disorder characterized by recurrent attacks of difficult breathing, particularly on exhalation, due to an increased resistance to airflow through the respiratory bronchioles. Asthmatics are usually hypersensitive to a variety of stimuli, which cause the airways to narrow by contraction of their smooth muscle, by a swelling of the mucous membrane, or due to an increased mucus secretion. All asthmatics wheeze upon exercise, but some seem to be particularly sensitive to exercise (see exercise-induced asthma). Sports vary in their tendency to induce asthma with running having a high tendency, cycling a moderate tendency, and gymnastics and swimming a low tendency. Paradoxically, many asthmatics gain relief from their bronchospasms by regular exercise, and exercise is now regarded as important in the management of asthma. Many drugs help to control asthma, but some are on the World Anti-Doping Agency's 2005 Prohibited List, e.g. those containing stimulants such as ephedrine. Several athletes have been disqualified from the Olympic Games because of pre-race administration of an oral anti-asthmatic drug. All beta₂ agonists (the group of drugs commonly used to treat asthma) are prohibited, except formoterol, salbutamol (less than 1000 ng/mL), salmeterol, and terbutaline, which are permitted by inhalation only when a Therapeutic Use Exemption has been granted.

Due to its frequent association with psychoaffective symptoms, asthma is considered a classic psychosomatic disorder. The Hungarian-American analyst Franz Alexander was an early proponent of psychosomatic medicine, and during the 1940s he and Thomas French applied the "specific emotion theory" to try to establish a link between the onset of asthmatic attacks and emotional conflicts. Their research suggested that pregenital instinctual desires, experienced as threatening to the dependent mother-child dyad, could give rise to bronchial symptoms, noting that breathing is the first independent post-natal physiological function. It is possible to view the infant's double separation from the mother—biological and psycho-affective—as reviving the Freud-Rank birth trauma debate. A generation later in 1963, research by Peter Hobart Knapp suggested that allergic diathesis was a necessary precondition to developing symptoms, and offered as possible triggering mechanisms either hysterical conversion or conflicts of oral incorporation expressed through the respiratory apparatus.

In France, Pierre Marty, one of the founders of the Ecole de Psychosomatique de Paris, theorized that asthma, like other allergic manifestations, arises from a specific type of object relationship that involves a form of profound and almost instantaneous mimetic identification that includes a projective movement identifying object with subject. The difficulty of maintaining such a state of confused fusion either produces some accommodation or, in the case of an intractable object, creates a distance from the object that may be considered at once symbolic and real. The separation from the object whose own characteristics are too distant from, or independent of, the subject, occurs without the work of mourning. The asthmatic attack breaks out during conflict between two objects, both equally invested but themselves in conflict. The asthmatic attack externalizes and diverts internal psychological destruction.

Bibliography

Alexander, Franz, and French, Thomas M. (1941). Psychogenic factors in bronchial asthma. Washington, DC: National Research Council.

Bauduin, Andrée. (1985). L'asthme bronchique, aspects dynamiques et psychanalytiques. Revue médicale de Liège, 90 (22).

Fenichel, Otto. (1953). The collected papers of Otto Fenichel. First and second series (H. Fenichel and D. Rapaport, Eds.). New York: Norton.

Knapp, Peter H. (1989). Psychosomatic aspects of bronchial asthma. Madison, CT: International Universities Press.

—ROBERT ASSÉO

(az-muh)

A chronic disease of the respiratory system, characterized by sudden, recurring attacks of difficult breathing, wheezing, and coughing. During an attack, the bronchial tubes go into spasms, becoming narrower and less able to move air into the lungs. Various substances to which the sufferer has an allergy, such as animal hair, dust, pollen, or certain foods, can trigger an attack.

A condition marked by recurrent attacks of dyspnea, with wheezing due to spasmodic constriction of the bronchi.
It is also known as bronchial asthma. Attacks vary greatly from occasional periods of wheezing and slight dyspnea to severe attacks that almost cause suffocation.

• acute equine a. — sudden attacks of respiratory distress in horses at pasture; the dyspnea responds dramatically to treatment with corticosteroids combined with antihistamines.
• allergic a. — extrinsic asthma; bronchial asthma due to allergy. Called also atopic asthma.
• atopic a. — see allergic asthma (above).
• bronchial a. — asthma.
• cardiac a. — a term applied to breathing difficulties due to pulmonary edema in heart disease, such as left ventricular failure.
• feline a. — see feline bronchial asthma.

Asthma
Classification & external resources

ICD-10	J45.
ICD-9	493
OMIM	600807
DiseasesDB	1006
MedlinePlus	000141
eMedicine	med/177  emerg/43
MeSH	C08.127.108

Asthma is a chronic illness involving the respiratory system in which the airway occasionally constricts, becomes inflamed, and is lined with excessive amounts of mucus, often in response to one or more triggers. These episodes may be triggered by such things as exposure to an environmental stimulant (or allergen), cold air, warm air, moist air, exercise or exertion, or emotional stress. In children, the most common triggers are viral illnesses such as those that cause the common cold.^[1] This airway narrowing causes symptoms such as wheezing, shortness of breath, chest tightness, and coughing. The airway constriction responds to bronchodilators. Between episodes, most patients feel well but can have mild symptoms and they may remain short of breath after exercise for longer periods of time than the unaffected individual. The symptoms of asthma, which can range from mild to life threatening, can usually be controlled with a combination of drugs and environmental changes.

Public attention in the developed world has recently focused on asthma because of its rapidly increasing prevalence, affecting up to one in four urban children.^[2]

History

The word 'asthma' is derived from the Greek aazein, meaning "sharp breath." The word first appears in Homer's Iliad;^[3] Hippocrates was the first to use it in reference to the medical condition, in 450 BC. Hippocrates thought that the spasms associated with asthma were more likely to occur in tailors, anglers, and metalworkers. Six centuries later, Galen wrote much about asthma, noting that it was caused by partial or complete bronchial obstruction. In 1190 AD, Moses Maimonides, an influential medieval rabbi, philosopher, and physician, wrote a treatise on asthma, describing its prevention, diagnosis, and treatment.^[4] In the 17th century, Bernardino Ramazzini noted a connection between asthma and organic dust. The use of bronchodilators started in 1901, but it was not until the 1960s that the inflammatory component of asthma was recognized, and anti-inflammatory medications were added to the regimens.

Signs and symptoms

In some individuals asthma is characterized by chronic respiratory impairment. In others it is an intermittent illness marked by episodic symptoms that may result from a number of triggering events, including upper respiratory infection, stress, airborne allergens, air pollutants (such as smoke or traffic fumes), or exercise. Some or all of the following symptoms may be present in those with asthma: dyspnea, wheezing, stridor, coughing, an inability for physical exertion. Some asthmatics that have severe shortness of breath and tightening of the lungs never wheeze or have stridor and their symptoms may be confused with a COPD-type disease.

An acute exacerbation of asthma is referred to as an asthma attack. The clinical hallmarks of an attack are shortness of breath (dyspnea) and either wheezing or stridor.^[5] Although the former is "often regarded as the sine qua non of asthma,^[5] some patients present primarily with coughing, and in the late stages of an attack, air motion may be so impaired that no wheezing may be heard. When present the cough may sometimes produce clear sputum. The onset may be sudden, with a sense of constriction in the chest, breathing becomes difficult, and wheezing occurs (primarily upon expiration, but can be in both respiratory phases).

Signs of an asthmatic episode include wheezing, rapid breathing (tachypnea), prolonged expiration, a rapid heart rate (tachycardia), rhonchous lung sounds (audible through a stethoscope), and over-inflation of the chest. During a serious asthma attack, the accessory muscles of respiration (sternocleidomastoid and scalene muscles of the neck) may be used, shown as in-drawing of tissues between the ribs and above the sternum and clavicles, and the presence of a paradoxical pulse (a pulse that is weaker during inhalation and stronger during exhalation).

During very severe attacks, an asthma sufferer can turn blue from lack of oxygen, and can experience chest pain or even loss of consciousness. Just before loss of consciousness, there is a chance that the patient will feel numbness in the limbs and palms may start to sweat. Feet may become icy cold. Severe asthma attacks, which may not be responsive to standard treatments (status asthmaticus), are life-threatening and may lead to respiratory arrest and death. Despite the severity of symptoms during an asthmatic episode, between attacks an asthmatic may show few or even no signs of the disease.^[6]

Diagnosis

Asthma is defined simply as reversible airway obstruction. Reversibility occurs either spontaneously or with treatment. The basic measurement is peak flow rates and the following diagnostic criteria are used by the British Thoracic Society:^[7]

• ≥20% difference on at least three days in a week for at least two weeks;
• ≥20% improvement of peak flow following treatment, for example:
  • 10 minutes of inhaled β-agonist (e.g., salbutamol);
  • six week of inhaled corticosteroid (e.g., beclometasone);
  • 14 days of 30mg prednisolone.
• ≥20% decrease in peak flow following exposure to a trigger (e.g., exercise).

In many cases, a physician can diagnose asthma on the basis of typical findings in a patient's clinical history and examination. Asthma is strongly suspected if a patient suffers from eczema or other allergic conditions—suggesting a general atopic constitution—or has a family history of asthma. While measurement of airway function is possible for adults, most new cases are diagnosed in children who are unable to perform such tests. Diagnosis in children is based on a careful compilation and analysis of the patient's medical history and subsequent improvement with an inhaled bronchodilator medication. In adults, diagnosis can be made with a peak flow meter (which tests airway restriction), looking at both the diurnal variation and any reversibility following inhaled bronchodilator medication.

Testing peak flow at rest (or baseline) and after exercise can be helpful, especially in young asthmatics who may experience only exercise-induced asthma. If the diagnosis is in doubt, a more formal lung function test may be conducted. Once a diagnosis of asthma is made, a patient can use peak flow meter testing to monitor the severity of the disease.

In the Emergency Department doctors may use a capnography PMID 16187465 which measures the amount of exhaled carbon dioxide along with pulse oximetry which shows the amount of oxygen dissolved in the blood, to determine the severity of an asthma attack as well as the response to treatment.

Differential diagnosis

Before diagnosing someone as asthmatic, alternative possibilities should be considered. A clinician taking a history should check whether the patient is using any known bronchoconstrictors (substances that cause narrowing of the airways, e.g., certain anti-inflammatory agents or beta-blockers).

Chronic obstructive pulmonary disease, which closely resembles asthma, is correlated with more exposure to cigarette smoke, an older patient, less symptom reversibility after bronchodilator administration (as measured by spirometry), and decreased likelihood of family history of atopy.

Pulmonary aspiration, whether direct due to dysphagia (swallowing disorder) or indirect (due to acid reflux), can show similar symptoms to asthma. However, with aspiration, fevers might also indicate aspiration pneumonia. Direct aspiration (dysphagia) can be diagnosed by performing a Modified Barium Swallow test and treated with feeding therapy by a qualified speech therapist. If the aspiration is indirect (from acid reflux) then treatment directed at this is indicated.

A majority of children who are asthma sufferers have an identifiable allergy trigger. Specifically, in a 2004 study, 71% had positive test results for more than 1 allergen, and 42% had positive test results for more than 3 allergens.^[8]

The majority of these triggers can often be identified from the history; for instance, asthmatics with hay fever or pollen allergy will have seasonal symptoms, those with allergies to pets may experience an abatement of symptoms when away from home, and those with occupational asthma may improve during leave from work. Occasionally, allergy tests are warranted and, if positive, may help in identifying avoidable symptom triggers.

After a pulmonary function test has been carried out, radiological tests, such as a chest X-ray or CT scan, may be required to exclude the possibility of other lung diseases. In some people, asthma may be triggered by gastroesophageal reflux disease, which can be treated with suitable antacids. Very occasionally, specialized tests after inhalation of methacholine — or, even less commonly, histamine — may be performed.

Asthma is categorized by the United States National Heart, Lung and Blood Institute as falling into one of four categories: intermittent, mild persistent, moderate persistent and severe persistent. The diagnosis of "severe persistent asthma" occurs when symptoms are continual with frequent exacerbations and frequent nighttime symptoms, result in limited physical activity and when lung function as measured by PEV or FEV₁ tests is less than 60% predicted with PEF variability greater than 30%.

There is no cure for asthma. Doctors have only found ways to prevent attacks and relieve the symptoms such as tightness of the chest and trouble breathing.

Links: http://www.mismr.org/educational/asthma.html http://www.newtoasthma.com/

Pathophysiology

Inflamed airways and bronchoconstriction in asthma. Airways narrowed as a result of the inflammatory response cause wheezing.

Bronchoconstriction

During an asthma episode, inflamed airways react to environmental triggers such as smoke, dust, or pollen. The airways narrow and produce excess mucus, making it difficult to breathe. In essence, asthma is the result of an immune response in the bronchial airways.^[9]

The airways of asthmatics are "hypersensitive" to certain triggers, also known as stimuli (see below). In response to exposure to these triggers, the bronchi (large airways) contract into spasm (an "asthma attack"). Inflammation soon follows, leading to a further narrowing of the airways and excessive mucus production, which leads to coughing and other breathing difficulties.

Stimuli

• Allergenic air pollution, from nature, typically inhaled, which include waste from common household pests, such as the house dust mite and cockroach, grass pollen, mould spores, and pet epithelial cells; ^{[citation needed]}
• Indoor allergenic air pollution from volatile organic compounds, including perfumes and perfumed products. Examples include soap, dishwashing liquid, laundry detergent, fabric softener, paper tissues, paper towels, toilet paper, shampoo, hairspray, hair gel, cosmetics, facial cream, sun cream, deodorant, cologne, shaving cream, aftershave lotion, air freshener and candles, and products such as oil-based paint.^{[citation needed]}
• Medications, including aspirin,^[10] β-adrenergic antagonists (beta blockers), and penicillin.^{[citation needed]}
• Food allergies such as milk, peanuts, and eggs. However, asthma is rarely the only symptom, and not all people with food or other allergies have asthma. ^{[citation needed]}
• Use of fossil fuel related allergenic air pollution, such as ozone, smog, summer smog, nitrogen dioxide, and sulfur dioxide, which is thought to be one of the major reasons for the high prevalence of asthma in urban areas;^{[citation needed]}
• Various industrial compounds and other chemicals, notably sulfites; chlorinated swimming pools generate chloramines—monochloramine (NH₂Cl), dichloramine (NHCl₂) and trichloramine (NCl₃)—in the air around them, which are known to induce asthma.^[11]
• Early childhood infections, especially viral respiratory infections. However, persons of any age can have asthma triggered by colds and other respiratory infections even though their normal stimuli might be from another category (e.g. pollen) and absent at the time of infection. 80% of asthma attacks in adults and 60% in children are caused by respiratory viruses.^{[citation needed]}
• Exercise, the effects of which differ somewhat from those of the other triggers;^{[citation needed]}
• Allergenic indoor air pollution from newsprint & other literature such as, junk mail leaflets & glossy magazines (in some countries).^{[citation needed]}
• Hormonal changes in adolescent girls and adult women associated with their menstrual cycle can lead to a worsening of asthma. Some women also experience a worsening of their asthma during pregnancy whereas others find no significant changes, and in other women their asthma improves during their pregnancy.^{[citation needed]}
• Emotional stress which is poorly understood as a trigger.^{[citation needed]}
• Cold weather can make it harder for asthmatics to breathe.^[12]

Bronchial inflammation

The mechanisms behind allergic asthma—i.e., asthma resulting from an immune response to inhaled allergens—are the best understood of the causal factors. In both asthmatics and non-asthmatics, inhaled allergens that find their way to the inner airways are ingested by a type of cell known as antigen presenting cells, or APCs. APCs then "present" pieces of the allergen to other immune system cells. In most people, these other immune cells (T_H0 cells) "check" and usually ignore the allergen molecules. In asthmatics, however, these cells transform into a different type of cell (T_H2), for reasons that are not well understood. The resultant T_H2 cells activate an important arm of the immune system, known as the humoral immune system. The humoral immune system produces antibodies against the inhaled allergen. Later, when an asthmatic inhales the same allergen, these antibodies "recognize" it and activate a humoral response. Inflammation results: chemicals are produced that cause the airways to constrict and release more mucus, and the cell-mediated arm of the immune system is activated. The inflammatory response is responsible for the clinical manifestations of an asthma attack. The following section describes this complex series of events in more detail.

Pathogenesis

The fundamental problem in asthma appears to be immunological: young children in the early stages of asthma show signs of excessive inflammation in their airways. Epidemiological findings give clues as to the pathogenesis: the incidence of asthma seems to be increasing worldwide, and asthma is now very much more common in affluent countries.

In 1968 Andor Szentivanyi first described The Beta Adrenergic Theory of Asthma; in which blockage of the Beta-2 receptors of pulmonary smooth muscle cells causes asthma.^[13] Szentivanyi's Beta Adrenergic Theory is a citation classic^[14] and has been cited more times than any other article in the history of the Journal of Allergy.

In 1995 Szentivanyi and colleagues demonstrated that IgE blocks beta-2 receptors.^[15] Since overproduction of IgE is central to all atopic diseases, this was a watershed moment in the world of allergy.^[16]

The Beta-Adrenergic Theory has been cited in the scholarship of such noted investigators as Richard F. Lockey (former President of the American Academy of Allergy, Asthma, and Immunology),^[17] Charles Reed (Chief of Allergy at Mayo Medical School),^[18] and Craig Venter (Human Genome Project).^[19]

Causes

Many studies have linked asthma, bronchitis, and acute respiratory illnesses to air quality experienced by children.^[20] One of the largest of these studies is the California Children's Health Study.^[21] From the press release [1]

The study showed that children in the high ozone communities who played three or more sports developed asthma at a rate three times higher than those in the low ozone communities. Because participation in some sports can result in a child drawing up to 17 times the “normal” amount of air into the lungs, young athletes are more likely to develop asthma.

Note that concentrations of ozone have risen steadily in Europe since 1870. [2]

Another theory of pathogenesis is that asthma is a disease of hygiene. In nature, babies are exposed to bacteria and other antigens soon after birth, "switching on" the T_H1 lymphocyte cells of the immune system that deal with bacterial infection. If this stimulus is insufficient, as it may be in modern, clean environments, then T_H2 cells predominate, and asthma and other allergic diseases may develop. This "hygiene hypothesis" may explain the increase in asthma in affluent populations. Support is provided by a recent European study which linked the use cleaning sprays and air fresheners to asthma. ^[22]

The T_H2 lymphocytes and eosinophil cells that protect us against parasites and other infectious agents are the same cells responsible for the allergic reaction. Charcot-Leyden crystals are formed when crystalline material in eosinophils coalesce. These crystals are significant in sputum samples of people with asthma. In the developed world, the parasites that eosinophils are programmed to combat are now rarely encountered, but the immune response remains and is wrongly triggered in some individuals by certain allergens.

It has been postulated that some forms of asthma may be related to infection, in particular by Chlamydia pneumoniae.^[23] This issue remains controversial, as the relationship is not borne out by meta-analysis of the research.^[24] The correlation seems to be not with the onset, but rather with accelerated loss of lung function in adults with new onset of non-atopic asthma.^[25] One possible explanation is that some asthmatics may have altered immune response that facilitates long-term chlamydia pneumonia infection.^[26] The response to targeting with macrolide antibiotics has been investigated, but the temporary benefit reported in some studies may reflect just their anti-inflammatory activities rather than their antimicrobic action.^[24]

One group of researchers suggested that, in part, asthma has a neurogenic paroxysmal component,^[27] and that several anti-eleptic drugs have an effect. However only one paper^[28] has been published as listed by PubMed and its conclusions criticized.^[29]

A study conducted by the National Jewish Medical and Research Center concluded that overweight and obesity are associated with a dose-dependent increase in the odds of incident asthma in men and women, suggesting asthma incidence could be reduced by interventions targeting overweight and obesity. ^[30]

Asthma and sleep apnea

It is recognized with increasing frequency, that patients who have both obstructive sleep apnea (OSA) and bronchial asthma, often improve tremendously when the sleep apnea is diagnosed and treated.^[31] CPAP is not effective in patients with nocturnal asthma only.^[32] Air pollution can cause asthma.

Asthma and gastro-esophageal reflux disease

If gastro-esophageal reflux disease is present, the patient may have repetitive episodes of acid aspiration, which results in airway inflammation and "irritant-induced" asthma.^{[citation needed]} GERD may be common in difficult-to-control asthma, but generally speaking, treating it does not seem to affect the asthma.^[33]

Treatment

The most effective treatment for asthma is identifying triggers, such as pets or aspirin, and limiting or eliminating exposure to them. Desensitization to allergens has been shown to be a treatment option for certain patients.^[34]

As is common with respiratory disease, smoking is believed to adversely affect asthmatics in several ways, including an increased severity of symptoms, a more rapid decline of lung function, and decreased response to preventive medications.^[35] Automobile emissions are considered an even more significant cause and aggravating factor. [3] Asthmatics who smoke or who live near traffic [4] typically require additional medications to help control their disease. Furthermore, exposure of both non-smokers and smokers to wood smoke, gas stove fumes and second-hand smoke is detrimental, resulting in more severe asthma, more emergency room visits, and more asthma-related hospital admissions.^[36] Smoking cessation and avoidance of second-hand smoke is strongly encouraged in asthmatics.^[37]

The specific medical treatment recommended to patients with asthma depends on the severity of their illness and the frequency of their symptoms. Specific treatments for asthma are broadly classified as relievers, preventers and emergency treatment. The Expert Panel Report 2: Guidelines for the Diagnosis and Management of Asthma (EPR-2)^[37] of the U.S. National Asthma Education and Prevention Program, and the British Guideline on the Management of Asthma^[38] are broadly used and supported by many doctors. On August 29, 2007 the final Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma was officially released. Bronchodilators are recommended for short-term relief in all patients. For those who experience occasional attacks, no other medication is needed. For those with mild persistent disease (more than two attacks a week), low-dose inhaled glucocorticoids or alternatively, an oral leukotriene modifier, a mast-cell stabilizer, or theophylline may be administered. For those who suffer daily attacks, a higher dose of glucocorticoid in conjunction with a long-acting inhaled β-2 agonist may be prescribed; alternatively, a leukotriene modifier or theophylline may substitute for the β-2 agonist. In severe asthmatics, oral glucocorticoids may be added to these treatments during severe attacks.

For those in whom exercise can trigger an asthma attack (exercise-induced asthma), higher levels of ventilation and cold, dry air tend to exacerbate attacks. For this reason, activities in which a patient breathes large amounts of cold air, such as skiing and running, tend to be worse for asthmatics, whereas swimming in an indoor, heated pool, with warm, humid air, is less likely to provoke a response.^[5]

Researchers at Harvard Medical School (HMS) have come up with convincing evidence that the answer to what causes asthma lies in a special type of natural "killer" cell. This finding means that physicians may not be treating asthma sufferers with the right kinds of drugs. For example, natural killer T cells seem to be resistant to the corticosteroids in widely used inhalers.^[39]

Relief medication

Symptomatic control of episodes of wheezing and shortness of breath is generally achieved with fast-acting bronchodilators. These are typically provided in pocket-sized, metered-dose inhalers (MDIs). In young sufferers, who may have difficulty with the coordination necessary to use inhalers, or those with a poor ability to hold their breath for 10 seconds after inhaler use (generally the elderly), an asthma spacer (see top image) is used. The spacer is a plastic cylinder that mixes the medication with air in a simple tube, making it easier for patients to receive a full dose of the drug and allows for the active agent to be dispersed into smaller, more fully inhaled bits. A nebulizer which provides a larger, continuous dose can also be used. Nebulizers work by vaporizing a dose of medication in a saline solution into a steady stream of foggy vapour, which the patient inhales continuously until the full dosage is administered. There is no clear evidence, however, that they are more effective than inhalers used with a spacer. Nebulizers may be helpful to some patients experiencing a severe attack. Such patients may not be able to inhale deeply, so regular inhalers may not deliver medication deeply into the lungs, even on repeated attempts. Since a nebulizer delivers the medication continuously, it is thought that the first few inhalations may relax the airways enough to allow the following inhalations to draw in more medication.

Relievers include:

• Short-acting, selective beta₂-adrenoceptor agonists, such as salbutamol (albuterol USAN), levalbuterol, terbutaline and bitolterol.
  Tremors, the major side effect, have been greatly reduced by inhaled delivery, which allows the drug to target the lungs specifically; oral and injected medications are delivered throughout the body. There may also be cardiac side effects at higher doses (due to Beta-1 agonist activity), such as elevated heart rate or blood pressure; with the advent of selective agents, these side effects have become less common. Patients must be cautioned against using these medicines too frequently, as with such use their efficacy may decline, producing desensitization resulting in an exacerbation of symptoms which may lead to refractory asthma and death.
• Older, less selective adrenergic agonists, such as inhaled epinephrine and ephedrine tablets, have also been used. Cardiac side effects occur with these agents at either similar or lesser rates to albuterol.^{[40] [41]} When used solely as a relief medication, inhaled epinephrine has been shown to be an effective agent to terminate an acute asthmatic exacerbation.^[40] In emergencies, these drugs were sometimes administered by injection. Their use via injection has declined due to related adverse effects.
• Anticholinergic medications, such as ipratropium bromide may be used instead. They have no cardiac side effects and thus can be used in patients with heart disease; however, they take up to an hour to achieve their full effect and are not as powerful as the β₂-adrenoreceptor agonists.
• Inhaled glucocorticoids are usually considered preventive medications; however, a randomized controlled trial has demonstrated the benefit of 250 microg beclomethasone when taken as an as-needed combination inhaler with 100 microg of albuterol.^[42]

Prevention medication

Current treatment protocols recommend prevention medications such as an inhaled corticosteroid, which helps to suppress inflammation and reduces the swelling of the lining of the airways, in anyone who has frequent (greater than twice a week) need of relievers or who has severe symptoms. If symptoms persist, additional preventive drugs are added until the asthma is controlled. With the proper use of prevention drugs, asthmatics can avoid the complications that result from overuse of relief medications.

Asthmatics sometimes stop taking their preventive medication when they feel fine and have no problems breathing. This often results in further attacks, and no long-term improvement.

Preventive agents include the following.

• Inhaled glucocorticoids are the most widely used of the prevention medications and normally come as inhaler devices (ciclesonide, beclomethasone, budesonide, flunisolide, fluticasone, mometasone, and triamcinolone).
  Long-term use of corticosteroids can have many side effects including a redistribution of fat, increased appetite, blood glucose problems and weight gain. In particular high doses of steroids may cause osteoporosis. For this reasons inhaled steroids are generally used for prevention, as their smaller doses are targeted to the lungs unlike the higher doses of oral preparations. Nevertheless, patients on high doses of inhaled steroids may still require prophylactic treatment to prevent osteoporosis.
  Deposition of steroids in the mouth may cause a hoarse voice or oral thrush (due to decreased immunity). This may be minimised by rinsing the mouth with water after inhaler use, as well as by using a spacer which increases the amount of drug that reaches the lungs.
• Leukotriene modifiers (montelukast, zafirlukast, pranlukast, and zileuton).
• Mast cell stabilizers (cromoglicate (cromolyn), and nedocromil).
• Antimuscarinics/anticholinergics (ipratropium, oxitropium, and tiotropium), which have a mixed reliever and preventer effect. (These are rarely used in preventive treatment of asthma, except in patients who do not tolerate beta-2-agonists.)
• Methylxanthines (theophylline and aminophylline), which are sometimes considered if sufficient control cannot be achieved with inhaled glucocorticoids and long-acting β-agonists alone.
• Antihistamines, often used to treat allergic symptoms that may underlie the chronic inflammation. In more severe cases, hyposensitization ("allergy shots") may be recommended.
• Omalizumab, an IgE blocker; this can help patients with severe allergic asthma that does not respond to other drugs. However, it is expensive and must be injected.
• Methotrexate is occasionally used in some difficult-to-treat patients.
• If chronic acid indigestion (GERD) contributes to a patient's asthma, it should also be treated, because it may prolong the respiratory problem.

Additionally, the antidepressant tianeptine has shown significant efficacy in children with asthma.

Long-acting β₂-agonists

Long-acting bronchodilators (LABD) are similar in structure to short-acting selective beta₂-adrenoceptor agonists, but have much longer sidechains resulting in a 12-hour effect, and are used to give a smoothed symptomatic relief (used morning and night). While patients report improved symptom control, these drugs do not replace the need for routine preventers, and their slow onset means the short-acting dilators may still be required. In November of 2005, the American FDA released a health advisory alerting the public to findings that show the use of long-acting β₂-agonists could lead to a worsening of symptoms, and in some cases death.^[43]

Currently available long-acting beta₂-adrenoceptor agonists include salmeterol, formoterol, bambuterol, and sustained-release oral albuterol. Combinations of inhaled steroids and long-acting bronchodilators are becoming more widespread; the most common combination currently in use is fluticasone/salmeterol (Advair in the United States, and Seretide in the United Kingdom). Another combination is budesonide/formoterol which is commercially known as symbicort.

A recent meta-analysis of the roles of long-acting beta-agonists may indicate a danger to asthma patients. "These agents can improve symptoms through bronchodilation at the same time as increasing underlying inflammation and bronchial hyper-responsiveness, thus worsening asthma control without any warning of increased symptoms," said Shelley Salpeter in a Cornell study. The study goes on to say that "Three common asthma inhalers containing the drugs salmeterol or formoterol may be causing four out of five US asthma-related deaths per year and should be taken off the market".^[44] This assertion has drawn criticism from many asthma specialists for being inaccurate. As Dr. Hal Nelson points out in a recent letter to the Annals of Internal Medicine,

"Salpeter and colleagues also assert that salmeterol may be responsible for 4000 of the 5000 asthma-related deaths that occur in the United States annually. However, when salmeterol was introduced in 1994, more than 5000 asthma-related deaths occurred per year. Since the peak of asthma deaths in 1996, salmeterol sales have increased about 5-fold, while overall asthma mortality rates have decreased by about 25%, despite a continued increase in asthma diagnoses. In fact, according to the most recent data from the National Center for Health Statistics, U.S. asthma mortality rates peaked in 1996 (with 5667 deaths) and have decreased steadily since. The last available data, from 2004, indicate that 3780 deaths occurred. Thus, the suggestion that a vast majority of asthma deaths could be attributable to LABA use is inconsistent with the facts."

Dr. Salpeter has since tempered her comments regarding LABAs.^{[citation needed]}

Emergency treatment

When an asthma attack is unresponsive to a patient's usual medication, other treatments are available to the physician or hospital:^[45]

• oxygen to alleviate the hypoxia (but not the asthma per se) that results from extreme asthma attacks;
• nebulized salbutamol or terbutaline (short-acting beta-2-agonists), often combined with ipratropium (an anticholinergic);
• systemic steroids, oral or intravenous (prednisone, prednisolone, methylprednisolone, dexamethasone, or hydrocortisone). Some research has looked into an alternative inhaled route.^[46]
• other bronchodilators that are occasionally effective when the usual drugs fail:
  • intravenous salbutamol
  • nonspecific beta-agonists, injected or inhaled (epinephrine, isoetharine, isoproterenol, metaproterenol);
  • anticholinergics, IV or nebulized, with systemic effects (glycopyrrolate, atropine, ipratropium);
  • methylxanthines (theophylline, aminophylline);
  • inhalation anesthetics that have a bronchodilatory effect (isoflurane, halothane, enflurane);
  • the dissociative anaesthetic ketamine, often used in endotracheal tube induction
  • magnesium sulfate, intravenous; and
• intubation and mechanical ventilation, for patients in or approaching respiratory arrest.
• Heliox, a mixture of helium and oxygen, may be used in a hospital setting. It has a more laminar flow than ambient air and moves more easily through constricted airways

Alternative and complementary medicine

Many asthmatics, like those who suffer from other chronic disorders, use alternative treatments; surveys show that roughly 50% of asthma patients use some form of unconventional therapy.^[47][48] There are little data to support the effectiveness of most of these therapies. A Cochrane systematic review of acupuncture for asthma found no evidence of efficacy.^[49] A similar review of air ionisers found no evidence that they improve asthma symptoms or benefit lung function; this applied equally to positive and negative ion generators.^[50] A study of "manual therapies" for asthma, including osteopathic, chiropractic, physiotherapeutic and respiratory therapeutic manoeuvers, found there is insufficient evidence to support or refute their use in treating asthma;^[51] these manoeuvers include various osteopathic and chiropractic techniques to "increase movement in the rib cage and the spine to try and improve the working of the lungs and circulation"; chest tapping, shaking, vibration, and the use of "postures to help shift and cough up phlegm." On the other hand, one meta-analysis found that homeopathy has a potentially mild benefit in reducing symptom intensity;^[52] however, the number of patients involved in the analysis was small, and subsequent studies have not supported this finding.^[53] Several small trials have suggested some benefit from various yoga practices, ranging from integrated yoga programs^[54] —"yogasanas, Pranayama, meditation, and kriyas"—to sahaja yoga,^[55] a form of meditation.

The Buteyko method, a Russian therapy based on breathing exercises, has been investigated. A randomized, controlled trial of just 39 patients in 1998 showed a substantial reduction in the need for beta-agonists and a 50% reduction in the need for inhaled steroids. Quality of life scores improved significantly as people were less afraid of their condition and more confident of the future. Lung function remained the same despite the decrease in medication.^[56] A trial in New Zealand in 2000 showed an 85% reduction in the use of beta-agonist medication and a 50% reduction in inhaled steroid use after six months.^[57]

In recent years Helminthic therapy has emerged as one of the most promising alternative therapies because research has identified a negative association between helminth infection (hookworm) and asthma and hay fever.^[58] Some have suggested that hookworm infestation, although not medically sanctioned, would cure asthma. There is both anectdotal evidence^[59][60] and peer-reviewed research to support this viewpoint. ^[61]

Guaifenesin, an expectorant available over the counter, may have a small effect in managing thickened bronchial mucus.

Prognosis

The prognosis for asthmatics is good; especially for children with mild disease. For asthmatics diagnosed during childhood, 54% will no longer carry the diagnosis after a decade. The extent of permanent lung damage in asthmatics is unclear. Airway remodelling is observed, but it is unknown whether these represent harmful or beneficial changes.^[9] Although conclusions from studies are mixed, most studies show that early treatment with glucocorticoids prevents or ameliorates decline in lung function as measured by several parameters.^[62] For those who continue to suffer from mild symptoms, corticosteroids can help most to live their lives with few disabilities. The mortality rate for asthma is low, with around 6000 deaths per year in a population of some 10 million patients in the United States.^[5] Better control of the condition may help prevent some of these deaths.

Epidemiology

The prevalence of childhood asthma has increased since 1980, especially in younger children.

More than 6% of children in the United States have been diagnosed with asthma, a 75% increase in recent decades. The rate soars to 40% among some populations of urban children.^{[citation needed]}

Asthma is usually diagnosed in childhood. The risk factors for asthma include:^{[citations needed]}

• a personal or family history of asthma or atopy;
• triggers (see Pathophysiology above);
• premature birth or low birth weight;
• viral respiratory infection in early childhood;
• maternal smoking;
• being male, for asthma in prepubertal children; and
• being female, for persistence of asthma into adulthood.

There is a reduced occurrence of asthma in people who were breast-fed as babies. Current research suggests that the prevalence of childhood asthma has been increasing. According to the Centers for Disease Control and Prevention's National Health Interview Surveys, some 9% of US children below 18 years of age had asthma in 2001, compared with just 3.6% in 1980 (see figure). The World Health Organization (WHO) reports that some 8% of the Swiss population suffers from asthma today, compared with just 2% some 25–30 years ago.^[63] Although asthma is more common in affluent countries, it is by no means a problem restricted to the affluent; the WHO estimate that there are between 15 and 20 million asthmatics in India. In the U.S., urban residents, Hispanics, and African Americans are affected more than the population as a whole. Globally, asthma is responsible for around 180,000 deaths annually.^[63]

On the remote South Atlantic island Tristan da Cunha, 50% of the population are asthmatics due to heredity transmission of a mutation in the gene CC16.^{[citation needed]}

Socioeconomic factors

The incidence of asthma is higher among low-income populations within a society (it is not more common in developed countries than developing countries [5]), which in the western world are disproportionately ethnic minorities, and more likely to live near industrial areas. Additionally, asthma has been strongly associated with the presence of cockroaches in living quarters, which is more likely in such neighborhoods.^[64]

Asthma incidence and quality of treatment varies among different racial groups, though this may be due to correlations with income (and thus affordability of health care) and geography. For example, Black Americans are less likely to receive outpatient treatment for asthma despite having a higher prevalence of the disease. They are much more likely to have emergency room visits or hospitalization for asthma, and are three times as likely to die from an asthma attack compared to whites. The prevalence of "severe persistent" asthma is also greater in low-income communities compared with communities with better access to treatment.^[65][66]

Asthma and athletics

Asthma appears to be more prevalent in athletes than in the general population. One survey of participants in the 1996 Summer Olympic Games, in Atlanta, Georgia, U.S., showed that 15% had been diagnosed with asthma, and that 10% were on asthma medication. ^[67] These statistics have been questioned on at least two bases. Athletes with mild asthma may be more likely to be diagnosed with the condition than non-athletes, because even subtle symptoms may interfere with their performance and lead to pursuit of a diagnosis. It has also been suggested that some professional athletes who do not suffer from asthma claim to do so in order to obtain special permits to use certain performance-enhancing drugs.

There appears to be a relatively high incidence of asthma in sports such as cycling, mountain biking, and long-distance running, and a relatively lower incidence in weightlifting and diving. It is unclear how much of these disparities are from the effects of training in the sport, and from self-selection of sports that may appear to minimize the triggering of asthma.^[67][68]

In addition, there exists a variant of asthma called exercise-induced asthma that shares many features with allergic asthma. It may occur either independently, or concurrent with the latter. Exercise studies may be helpful in diagnosing and assessing this condition.

See also

Wikimedia Commons has media related to:

• Reactive airway disease
• Atopy
• Hopkins syndrome
• Hygiene hypothesis
• Immune response
• Asthma and Allergy Foundation of America
• Melatonin
• Occupational asthma

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External links

• World Health Organization site on asthma
• World Health Organization fact sheet on asthma
• National Heart, Lung, and Blood Institute — Asthma – U.S. NHLBI Information for Patients and the Public page.
• National Heart, Lung, and Blood Institute — Asthma – U.S. NHLBI Information for Health Professionals page.
• MedLinePlus: Asthma – a U.S. National Library of Medicine page.
• American Academy of Allergy, Asthma, and Immunology – a U.S. organization of medical professionals with a special interest in treating and researching conditions such as allergic rhinitis, asthma, atopic dermatitis/eczema, and anaphylaxis.
• Asthma and Allergy Foundation of America – national nonprofit patient advocacy organization with information about asthma.
• Asthma clinical trials and findings from current research.
• Global Initiative for Asthma (GINA) – evidence-based guidelines for asthma management.
• Video: What is Asthma?
• Asthma UK – a patient-oriented site with information on asthma and ways that UK residents can help improve asthma-related policy.
• Asthma Foundation of Queensland Information and education for Australian asthma sufferers.
• Case Studies in Environmental Medicine (CSEM): Environmental Triggers of Asthma – Agency for Toxic Substances and Disease Registry, U.S. Department of Health and Human Services.
• Asthma as Neurogenic Inflammatory Disease Neurogenic aspects of asthma. Pathophysiological links with other inflammatory disorders.
• Asthma and Socio-economic Status
• India Asthma Care Society Easy to understand asthma information site for patients.
• The Segal Guide to Asthma by Michael Segal MD PhD.
• Ourasthma.com – a patient-oriented site with information on asthma inhalers.

Pathology of respiratory system (J, 460-519)
Acute upper respiratory infections	Upper respiratory tract infection · Common cold · Rhinitis · Sinusitis · Pharyngitis (Strep throat)  · Tonsillitis · Laryngitis · Tracheitis · Croup · Epiglottitis
Influenza and Pneumonia	Influenza · Pneumonia (Viral, Bacterial, Bronchopneumonia) · Severe acute respiratory syndrome
Other acute lower respiratory infections	Bronchitis (Acute, Chronic)  · Bronchiolitis
Other diseases of upper respiratory tract	Vasomotor rhinitis · Hay fever · Atrophic rhinitis · Nasal polyp · Deviated septum · Adenoid hypertrophy · Peritonsillar abscess · Vocal fold nodule · Laryngospasm
Chronic lower respiratory diseases	Emphysema · COPD · Asthma · Status asthmaticus · Bronchiectasis
Lung diseases due to external agents	Pneumoconiosis (Coalworker's pneumoconiosis, Asbestosis, Silicosis, Bauxite fibrosis, Berylliosis, Siderosis) · Byssinosis · Hypersensitivity pneumonitis (Farmer's lung, Bird fancier's lung)
Other, principally affecting the interstitium	Acute respiratory distress syndrome · Pulmonary edema · Hamman-Rich syndrome · Interstitial lung disease
Suppurative and necrotic conditions of lower respiratory tract	Lung abscess · Pleural effusion · Empyema
Other	Pneumothorax · Hemothorax · Hemopneumothorax · Mendelson's syndrome · Respiratory failure · Atelectasis · Mediastinal emphysema  · Mediastinitis
see also congenital (Q30-Q34, 748)

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
n. - astma

Nederlands (Dutch)
astma

Français (French)
n. - asthme

Deutsch (German)
n. - Asthma

Ελληνική (Greek)
n. - (παθολ.) άσθμα

Italiano (Italian)
asma

Português (Portuguese)
n. - asma (f) (Med.)

Русский (Russian)
астма

Español (Spanish)
n. - asma

Svenska (Swedish)
n. - astma

中文（简体） (Chinese (Simplified))
哮喘, 气喘

中文（繁體） (Chinese (Traditional))
n. - 哮喘, 氣喘

한국어 (Korean)
n. - 천식

日本語 (Japanese)
n. - 喘息

العربيه (Arabic)
‏(الاسم) الأزمه : دا الربو‏

עברית (Hebrew)
n. - ‮קצרת, גנחת, אסתמה‬

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