Section 23. Children's Health Issues

Chapter 274. Respiratory Disorders

Topics: Introduction | Asthma | Bronchiolitis | Croup

Asthma

Asthma is a recurring condition in which certain stimuli trigger the airways to temporarily narrow, resulting in difficulty breathing (see Section 4, Chapter 44).

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 others, it resolves. More children than ever have asthma. Doctors are not sure why this is so, although there are theories. 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.

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. Triggers include indoor irritants, such as strong odors and irritating fumes (perfume, tobacco smoke); outdoor pollution; cold air; exercise; emotional distress; viral respiratory infections; and various substances to which the child is allergic, such as animal dander, dust or house dust mites, molds, and outdoor pollen. 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.

Risk Factors

Doctors do not completely understand why some children develop asthma, but a number of risk factors are recognized. A child with one asthmatic parent 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. In the United States, children in urban environments are more likely to develop asthma, particularly if they are from lower socioeconomic 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 Section 23, Chapter 274) 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 and Diagnosis

As the airways narrow in an asthma attack, the child develops difficulty breathing, typically accompanied by wheezing. Wheezing is a high-pitched noise heard when the child breathes out. Not all asthma attacks produce 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.

A doctor suspects asthma in children who have repeated episodes of wheezing, particularly when family members are known to have asthma or allergies. 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 Section 4, Chapter 39), although in most children, pulmonary function is normal between flare-ups.

Prognosis, Prevention, and Treatment

One half or more of children with asthma outgrow the condition. Those with more severe disease are more likely to have asthma as adults.

Asthma flare-ups can often 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 and allergens from the child's room. Secondhand tobacco smoke often worsens symptoms in children with asthma. If a particular allergen cannot be avoided, a doctor may try to desensitize the child 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 recommend that a child not avoid exercise, but rather use an asthma drug immediately before exercising if needed.

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. This measurement can be used as an objective assessment of the child's condition.

Treatment of an acute attack consists of opening the airways (bronchodilation) and stopping inflammation. A variety of inhaled drugs open the airways (bronchodilators (see Section 4, Chapter 44)). Typical examples are albuterol and ipratropium. 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 Section 4, Chapter 44). 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 drug 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 is usually 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 at least every 20 minutes initially. Sometimes doctors use injections of epinephrine, a bronchodilator, in children with very severe attacks if they are not able to breathe enough of the nebulized mist. Doctors usually give corticosteroids intravenously 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 child's attacks. Children with infrequent attacks that are not very severe usually use inhaled drugs, such as cromolyn or nedocromil, or a low dose of an inhaled corticosteroid every day to help prevent attacks. These drugs block the release of the chemical substances that inflame the airways, and they reduce inflammation. Long-acting theophylline preparations are a less expensive alternative for prevention in some children. Children with more frequent or more severe attacks also receive one or more other drugs, including long-acting bronchodilators such as salmeterol, leukotriene modifiers such as zafirlukast or montelukast, and inhaled corticosteroids. If these drugs do not prevent severe attacks, children may need to take corticosteroids by mouth. Children who experience attacks mainly during exercise usually inhale a dose of bronchodilator just before exercising.

Because asthma is a long-term condition with a variety of treatments, doctors work with parents and children to make sure they understand the condition as well as possible. 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, childcare providers, and others of the child's condition and drugs being used. Some children may be permitted to use inhalers in school as needed, and others must be supervised by the school nurse.