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Asthma is a recurring inflammatory lung disorder in which certain stimuli (triggers) inflame the airways and cause them to temporarily narrow, resulting in difficulty breathing.
Although asthma can develop at any age, it most commonly begins in children, particularly in the first 5 years of life. Some children continue to have asthma into the adult years. In other children, asthma resolves. Asthma has become much more common in recent decades. Doctors are not sure why this is so, but there are theories. More than 8.5% of children in the United States have been diagnosed with asthma, which is over a 100% increase in recent decades. The rate soars to 25% to 40% among some populations of urban children. Asthma is the leading cause of hospitalization for children and is the number one chronic condition causing elementary school absenteeism.
Most children with asthma are able to participate in normal childhood activities, except during flare-ups. A smaller number of children have moderate or severe asthma and need to take daily preventive drugs to enable them to engage in sports and normal play.
For unknown reasons, children with asthma respond to certain stimuli (triggers) in ways that children without asthma do not. There are many potential triggers, and most children respond to only a few. In some children, specific triggers for flare-ups cannot be identified.
These triggers all result in a similar response. Certain cells in the airways release chemical substances. These substances cause the airways to become inflamed and swollen and stimulate the muscle cells in the walls of the airways to contract. Repeated stimulation by these chemical substances increases mucus production in the airways, causes shedding of the cells lining the airways, and enlarges the muscle cells in the walls of the airways. Each of these responses contributes to a sudden narrowing of the airways (asthma attack). In most children, the airways return to normal between asthma attacks.
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| Common Asthma Triggers |
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Triggers
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Examples
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Allergens
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Dust or house mites, molds, outdoor pollen, animal dander, cockroach feces, and feathers
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Exercise
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Cold air exposure
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Infections
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Respiratory viruses and common colds
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Irritants
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Firsthand and secondhand tobacco smoke, perfumes, wood smoke, cleaning products, scented candles, outdoor air pollution, strong odors, and irritating fumes
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Other
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Emotions (such as anxiety, anger, and excitement), aspirin, and gastroesophageal reflux
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Risk Factors
Doctors do not completely understand why some children develop asthma, but a number of risk factors are recognized. A child with one parent who has asthma has a 25% risk of developing asthma. If both parents have asthma, the risk increases to 50%. Children whose mothers smoked during pregnancy are more likely to develop asthma. Asthma also has been linked to other factors related to the mother, such as young maternal age, poor maternal nutrition, and lack of breastfeeding. Prematurity and low birth weight are also risk factors.
In the United States, children in urban environments are more likely to develop asthma, particularly if they are from lower socioeconomic groups. Although it is not entirely understood, it is believed that poorer living conditions, greater potential exposure to triggers, and less access to health care contribute to the higher incidence of asthma in these groups. Although asthma affects a higher percentage of black children than white, the role that genetic aspects of race play in the increasing rate of asthma is controversial because black children are also more likely to live in urban areas.
Children who are exposed to high concentrations of allergens, such as dust mites or cockroach feces, at an early age are more likely to develop asthma. Children who have bronchiolitis (see Respiratory Disorders in Children: Bronchiolitis) at an early age often wheeze with subsequent viral infections. The wheezing may at first be interpreted as asthma, but these children are no more likely than others to have asthma during adolescence.
Symptoms
As the airways narrow in an asthma attack, the child develops difficulty breathing, chest tightness, and coughing, typically accompanied by wheezing. Wheezing is a high-pitched noise heard when the child breathes out. Not all asthma attacks cause wheezing, however. Mild asthma, particularly in very young children, may result only in a cough. Some older children with mild asthma tend to cough only when exercising or when exposed to cold air. Also, children with extremely severe asthma may not wheeze because there is too little air flowing to make a noise. In a severe attack, breathing becomes visibly difficult, wheezing usually becomes louder, the child breathes faster and with greater effort, and the ribs stand out when the child breathes in (inspiration). With very severe attacks, the child gasps for breath and sits upright, leaning forward. The skin is sweaty and pale or blue-tinged. Children with frequent severe attacks sometimes have a slowing of their growth, but their growth usually catches up to that of other children by adulthood.
Diagnosis
A doctor suspects asthma in children who have repeated episodes of wheezing, particularly when family members are known to have asthma or allergies. Doctors usually take x-rays, and they sometimes do allergy testing to help determine the cause.
Children with frequent wheezing episodes may be tested for other disorders, such as cystic fibrosis or gastroesophageal reflux. Older children sometimes undergo pulmonary function tests (see Diagnosis of Lung Disorders: Pulmonary Function Testing (PFT)), although in most children, pulmonary function is normal between flare-ups.
Older children or adolescents known to have asthma often use a peak flow meter (a small device that records how fast a person can blow out air) to measure the degree of airway obstruction. Doctors and parents can use this measurement to assess the child's condition during an attack and between attacks. X-rays are not done during an attack in children known to have asthma unless doctors suspect another disorder such as pneumonia or a collapsed lung.
Prognosis and Prevention
One half or more of children with asthma outgrow the disorder. Those with more severe disease are more likely to have asthma as adults. Other risk factors for persistence and relapse include female sex, smoking, developing asthma at a younger age, and sensitivity to household dust mites.
Asthma flare-ups often can be prevented by avoiding whatever triggers a particular child's attacks. Parents of children with allergies usually are advised to remove feather pillows, carpets, drapes, upholstered furniture, stuffed toys, and other potential sources of dust mites and allergens from the child's room. Secondhand tobacco smoke often worsens symptoms in children with asthma, so it is important to eliminate smoking in areas where the child spends time. If a particular allergen cannot be avoided, a doctor may try to desensitize the child by using allergy shots, although the benefits of allergy shots for asthma are not well known. Because exercise is so important for a child's development, doctors usually encourage children to maintain physical activities, exercise, and sports participation and use an asthma drug immediately before exercising if needed.
Treatment
Treatment of an acute attack consists of
A variety of inhaled drugs open the airways (bronchodilators—see Asthma: Prevention and Treatment). Typical examples are albuterol and ipratropium. Doctors do not recommend using long-acting bronchodilators, such as salmeterol and formoterol, as the only treatment for children. Older children and adolescents usually can take these drugs using a metered-dose inhaler. Children younger than 8 years or so often find it easier to use an inhaler with a spacer or holding chamber attached (see Asthma: Asthma ). Infants and very young children sometimes can use an inhaler and spacer if an infant-sized mask is attached. Those who cannot use inhalers may receive inhaled drugs at home through a mask connected to a nebulizer (a small device that creates a mist of the drug by using compressed air). Inhalers and nebulizers are equally effective at delivering the drug. Albuterol also can be taken by mouth, although this route is less effective than inhalation and usually is used only in infants who do not have a nebulizer. Children with moderately severe attacks also may be given corticosteroids by mouth.
Children with very severe attacks are treated in the hospital with bronchodilators given in a nebulizer or an inhaler at least every 20 minutes initially. Sometimes doctors use injections of epinephrine (a bronchodilator) in children with very severe attacks if inhaled drugs are not effective. Doctors usually give corticosteroids by vein to children having a severe attack.
Children who have mild, infrequent attacks usually take drugs only during an attack. Children with more frequent or severe attacks also need to take drugs even when they are not having attacks. Different drugs are used depending on the frequency and severity of the attacks. Children with infrequent attacks that are not very severe usually use a low dose of an inhaled corticosteroid every day to help prevent attacks. These drugs reduce inflammation by blocking the release of the chemical substances that inflame the airways.
Children with more persistent asthma or those at risk of frequent or more severe attacks inhale a moderate or high dose of a corticosteroid daily, with or without an additional drug such as a leukotriene modifier (montelukast or zafirlukast), a long-acting bronchodilator, or cromolyn. Drugs are increased or decreased over time to achieve optimal control of the child's asthma symptoms and to prevent severe attacks. If these drugs do not prevent severe attacks, children may need to take corticosteroids by mouth. Children who experience attacks during exercise usually inhale a dose of bronchodilator just before exercising.
Because asthma is a long-term disorderwith a variety of treatments, doctors work with parents and children to make sure they understand the disorder as well as possible. Adolescents and mature younger children should participate in developing their own asthma management plans and establishing their own goals for therapy to improve adherence to treatment. Parents and children should learn how to determine the severity of an attack, when to use drugs and a peak flow meter, when to call the doctor, and when to go to the hospital.
Parents and doctors should inform school nurses, child care providers, and others of the child's disorder and the drugs being used. Some children may be permitted to use inhalers in school as needed, and others must be supervised by the school nurse.
Last full review/revision February 2009 by Anand D. Kantak, MD; John T. McBride, MD
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