What Is Asthma?

Asthma is characterized by hyperresponsiveness to a variety of stimuli that provoke reversible airway obstruction. Airway obstruction is caused by two main processes: bronchospasm from constriction of smooth muscles around the airway and inflammation with edema of the respiratory mucosa and increased mucus production. Symptomatically, airway obstruction may produce cough, chest tightness or pain, decreased air flow, and wheezing.

What Are the Common Clinical Patterns of Asthma?

Intermittent asthma is the most common pattern of asthma in children. Other patterns are persistent asthma and seasonal allergic asthma (Table 69-1). Although the National Asthma guidelines classify intermittent asthma as “mild,” symptoms during an exacerbation of intermittent asthma in a child may be severe enough to warrant hospitalization. Therefore, intermittent asthma in childhood is best considered to have a range of severity from mild to severe. Young children commonly have a pattern of frequent, recurrent exacerbations of asthma, usually triggered by viral upper respiratory infections (URIs). Approximately 15% of children have 12 or more URIs a year, each of which may trigger an acute asthma exacerbation. This translates to approximately one URI-triggered asthma “attack” every 3 to 4 weeks for many young asthmatics during the fall and winter viral infection season. The frequency of URI-induced exacerbations makes the distinction between intermittent and persistent asthma difficult in infants and toddlers.

Table 69-1 Common Patterns of Asthma in Infants and Children

Do the National Asthma Guidelines Apply to Children?

The guidelines from the National Asthma Education and Prevention Program (NAEPP) place major emphasis on persistent asthma, the most common form in adults. The guidelines classify asthma as mild intermittent, mild persistent, moderate persistent, and severe persistent. Asthma in infancy and early childhood tends to have an intermittent pattern, although as children reach school age, the prevalence of atopic, IgE-mediated, and persistent asthma increases. Frequent recurrent viral-induced intermittent exacerbations that are commonly seen in early childhood are less well covered by the guidelines. As mentioned earlier, symptoms of intermittent asthma in children range from mild to severe.

What Are Common Triggers for Childhood Asthma?

Table 69-2 shows common triggers for asthma and their usual timing. All patterns of asthma can be exacerbated by viral illnesses. Up to 85% of acute exacerbations that require emergency department (ED) or hospital care are associated with viral illnesses.

Table 69-2 Common Triggers for Asthma

What History and Examination Findings Are Important?

The asthmatic child or adolescent often comes to attention because of cough (see Chapter 25). Table 69-3 shows important history and physical findings in asthma. Asthma diagnosis is primarily made from the patient’s history and response to medications.

Table 69-3 Findings in Asthma

What Tests Are Helpful in Diagnosing Asthma?

Pulmonary function tests can document reversibility of airway obstruction. Pulse oximetry obtained during an asthma exacerbation may show decreased oxygen saturation, and any value below 92% should be viewed with concern as this is the start of the steep portion of the oxygen desaturation curve. A blood gas determination will occasionally detect increased PaCO₂, but this is a late finding that may indicate impending respiratory failure. If a chest radiograph is obtained, it may show hyperinflation but could also have areas of streaky atelectasis and peribronchial thickening, similar in pattern to viral bronchiolitis. Methacholine challenge or exercise testing can provoke bronchoconstriction in a patient who is not currently symptomatic. Radioallergosorbent testing (RAST) or skin testing can be useful to identify potential allergens. A symptom diary helps identify the timing, pattern and triggers of asthma.

How Does a Therapeutic Trial Help with Diagnosis?

A therapeutic trial of bronchodilators usually relieves symptoms of bronchospasm, but there may be little or no relief if bronchospasm is accompanied by airway inflammation. A therapeutic trial of oral corticosteroids (5 to 7 days, maximum 10 days) should completely reverse the inflammation and relieve all asthma symptoms. If a patient’s symptoms fail to clear completely after an adequate course of steroids, then diagnoses other than asthma should be considered.

How Can Peak Flow Meters Be Used to Monitor Asthma?

Peak expiratory flow rate falls during asthma exacerbations. A child older than 5 or 6 years can usually be taught to use a peak flow meter to allow symptom monitoring, which can guide medication use. The peak flow meter is especially useful for those patients who underestimate or do not recognize the severity of their symptoms. The predicted average peak flow for a child is based on height, but peak flow should be determined individually for each child by frequent measurements when the patient is well.

How Would I Treat an Acute Exacerbation of Asthma?

An inhaled bronchodilator should be the first medication prescribed. Oral bronchodilators are much less effective than inhaled forms and have increased side effects. If there is incomplete response to inhaled bronchodilators, or if treatments are needed more often than every 4 hours (or more than four times a day), then a short course of oral corticosteroids should be started. For older patients who are able to check peak flows, persistent flows in the “red zone” should also prompt treatment with oral steroids. Early intervention with oral steroids can decrease hospitalizations by 90% and clinic visits by 50%. Pediatricians often prescribe oral steroids to be kept on hand at home and teach parents how to recognize symptoms that warrant use of steroids. This decreases the time to initiation of therapy and duration of symptoms.

When Should an Asthmatic Be Hospitalized?

Most asthmatics can be treated as outpatients. Table 69-4 shows key reasons for hospitalization.

Table 69-4 Criteria for Hospital Admission in Asthma

How Are Oral Steroids Prescribed for Acute Asthma?

For acute exacerbations of asthma, daily oral prednisone or prednisolone is typically prescribed at a dose of 1 to 2 mg/kg/day divided into two equal doses and continued until the patient’s symptoms are entirely resolved for at least 1 day. This generally takes from 5 to 7 days. Discontinuation of treatment before complete resolution of symptoms may result in a rebound of cough and wheeze. There is usually a 1- to 3-day lag time between starting oral steroids and improvement of symptoms, although response may be slower if the inflammation is severe or more chronic. Oral steroid treatment for asthma generally should not be continued past 10 days.

Should Steroids Be Tapered?

Tapering of steroids is not necessary for courses shorter than 14 days. Tapering increases the length of steroid therapy, subjects the patient to subtherapeutic doses that are not clinically useful, and increases the potential for side effects.

What Are the Side Effects of Steroids?

Short courses of oral steroids generally have minor, but often distressing, temporary side effects that include increased appetite, irritability, joint aches, and stomach ache. If steroids must be used frequently in short courses or for prolonged courses (> 14 days), more prominent side effects may occur, including Cushingoid features and hyperglycemia. Table 69-5 shows common corticosteroid side effects. Oral steroids also have a bitter taste, which complicates adherence to the treatment plans for young children.

Table 69-5 Corticosteroid Side Effects

How Is Persistent Asthma Treated?

Patients with persistent asthma have daily or near-daily symptoms, including difficulty with exercise and night waking with shortness of breath or cough. These patients often use albuterol daily but have inadequate relief of symptoms. Maintenance medications taken daily may reduce or prevent the symptoms of persistent asthma. Intermittent asthmatics do not benefit from maintenance asthma medications because these medications neither prevent symptoms of viral-induced intermittent asthma nor decrease the frequency of asthma exacerbations.

How Do I Choose a Medication for Persistent Asthma?

Table 69-6 lists different classes of maintenance medications for persistent asthma and shows some advantages and disadvantages of each. Inhaled steroids are generally the first line treatment for persistent asthma. The newer inhaled steroids—budesonide (Pulmicort), fluticasone (Flovent), or beclomethasone HFA (Qvar)—are more effective at lower doses than older preparations. Although long-acting beta-agonists are not as effective as inhaled steroids for monotherapy, medications such as salmeterol (Serevent) act synergistically with inhaled steroids and allow a decrease in steroid dose. They are available in combination with inhaled steroids, such as fluticasone/salmeterol (Advair). Recently, a small but significant increase in asthma-related deaths or life-threatening experiences was found in African-Americans older than 12 years using salmeterol in addition to their usual asthma care (Nelson et al., 2006). Montelukast (Singulair) is the preferred leukotriene modifier because it is a once-a-day medication with almost no side effects. Other leukotriene modifiers are either more difficult to administer or have more side effects: zileuton (Zyflo) must be given four times a day and can have hepatotoxicity, and zafirlukast (Accolate) must be given twice a day and has some drug-drug interactions. Mast cell stabilizers, cromolyn (Intal) and nedocromil (Tilade), have almost no effective role in the treatment of childhood asthma. Although theophylline (Theo-Dur, Slo-bid) is effective, it is not often prescribed because of the potential side effects and narrow therapeutic window.

Table 69-6 Maintenance Medications for Asthma

What Dose of Inhaled Steroid Should I Prescribe?

The preferred approach to inhaled steroid dosing is to start at a mid- to-high-level dose (400 or 800 mg/day) to establish good control of the asthma. The dose should then be decreased every few months until the minimum dose is reached that maintains good control (usually 100 to 200 mg/day). Growth delay can occur with inhaled steroids when total daily dose is above 500 mg/day; doses less than 500 mg/day are generally believed to be safe in children older than 5 years. For younger children and infants, safety is not well studied, and lower doses should be used if possible.

When Should I Make a Referral to a Pulmonologist?

The decision to make a referral to a pulmonary specialist depends on the severity of the asthma, the experience and comfort of the physician, and the comfort level of the family. In general, patients are referred to a specialist when asthma is not well controlled on one maintenance medication, when they have severe or frequent exacerbations, or when the history is complicated or confusing.

What Is Bronchiolitis?

Bronchiolitis is an acute viral infection that occurs most commonly in the winter months, usually affects children younger than 2 years, and is most problematic in young infants. Prematurity, congenital heart disease, and chronic lung disease greatly increase the risk of adverse outcomes. Bronchiolitis causes inflammation and edema of the bronchioles and is characterized by wheezing and respiratory distress. Respiratory syncytial virus (RSV) accounts for about one-third of cases. Other less common causes include parainfluenza virus, adenovirus, rhinovirus, enterovirus, influenza A and B, and Mycoplasma pneumoniae.

What History and Examination Findings Are Important?

History and examination findings for bronchiolitis are shown in Table 69-7.

Table 69-7 Findings in Bronchiolitis

What Tests Are Helpful in Diagnosing Bronchiolitis?

RSV can be identified rapidly by a direct fluorescent antibody test or by antigen detection with enzyme immunoassay [EIA]. Other respiratory viruses are detected by direct or indirect fluorescent antibodies. Viral cultures can be obtained but take 2 to 4 days to grow. All patients with suspected bronchiolitis should have pulse oximetry to guide use of supplemental oxygen. An infant whose respiratory rate is more than 60 breaths/min is likely to be hypoxic. A chest radiograph should be obtained in severe cases.