Wheezing and Asthma in Infants and Young Children
Wheezing is a relatively high-pitched whistling noise produced by movement of air through narrowed or compressed small airways. It is common in the first few years of life and is typically caused by viral respiratory tract infection or asthma, but other possible causes include inhaled irritants or allergens, esophageal reflux, and heart failure.
Recurrent episodes of wheezing are common in the first few years of life; 1 in 3 children have at least one acute wheezing episode before 3 yr of age (1). Because such wheezing typically responds to bronchodilators, this problem has historically been considered asthma. However, recent evidence that many children who have had recurrent wheezing in early childhood do not have asthma later in childhood or adolescence suggests that alternative diagnoses should be considered in young children with recurrent wheezing.
In some young children, recurrent wheezing episodes are the initial manifestations of asthma, and these children will continue to wheeze later in childhood or adolescence. In other children, wheezing episodes stop by age 6 to 10 yr and are not thought to represent asthma. In infants and young children, wheezing with viral illnesses, particularly those caused by respiratory syncytial virus and human rhinovirus, is associated with an increased risk of developing childhood asthma (2). An eventual diagnosis of asthma is more likely in children who have atopic symptoms, more severe wheezing episodes, and/or a family history of atopy or asthma.
Wheezing usually results from bronchospasm that may be worsened by inflammation of the small and medium airways that causes edema and further airway narrowing. An acute wheezing episode in infants and young children is usually caused by respiratory viral infections, but airway inflammation may also be caused (or worsened) by allergies or inhaled irritants (eg, tobacco smoke). Recurrent wheezing may be caused by frequent viral respiratory infections, allergies, or asthma. Less common causes of recurrent wheezing include chronic dysphagia that causes recurrent aspiration, gastroesophageal reflux, airway malacia, a retained aspirated foreign body, or heart failure. Often, the cause of recurrent wheezing is unclear.
1. Sigurs N, Bjarnason R, Sigurbergsson F, et al: Respiratory syncytial virus bronchiolitis in infancy is an important risk factor for asthma and allergy at age 7. Am J Respir Crit Care Med161:1501–1507, 2000. doi: 10.1164/ajrccm.161.5.9906076.
Wheezing is often accompanied by recurrent dry or productive cough. Other symptoms depend on the etiology and may include fever, runny nose (viral infection), and feeding difficulties (eg, due to heart failure or dysphagia).
On examination, wheezing manifests mainly on expiration, unless airway narrowing is severe, in which case wheezing can be heard on inspiration. Other findings present with more severe illness may include tachypnea, nasal flaring, intercostal and/or subxiphoid retractions, and cyanosis. Children with respiratory infection may have fever.
For a first episode of severe wheezing, most clinicians do a chest x-ray to detect signs of an aspirated foreign body, pneumonia, or heart failure and pulse oximetry to assess the need for oxygen therapy. The presence of generalized hyperinflation on plain x-rays suggests diffuse air trapping as seen in asthma, whereas localized findings suggest structural abnormalities or foreign body aspiration. Chest x-ray may also indicate the presence of a vascular ring as the cause of wheezing (eg, right aortic arch).
For children with recurrent episodes, exacerbations typically do not require testing unless there are signs of respiratory distress. Tests such as swallowing studies, contrast esophagram, CT, or bronchoscopy may be helpful for the few children with frequent or severe exacerbations or symptoms who do not respond to bronchodilators or other asthma drugs.
Infants and young children with acute wheezing are given inhaled bronchodilators and, if the wheezing is severe, systemic corticosteroids (see Treatment of acute exacerbation).
Children who are unlikely to develop persistent asthma, such as children who do not have atopy or a family history of atopy or asthma, and whose wheezing episodes are relatively mild and infrequent can usually be managed with only intermittent inhaled bronchodilators used as needed. Most young children with more frequent and/or severe wheezing episodes benefit from maintenance therapy with bronchodilators and anti-inflammatory drugs (eg, inhaled corticosteroids) as used for asthma (see Asthma : Treatment). However, although chronic use of a leukotriene modifier or low-dose inhaled corticosteroid decreases the severity and frequency of wheezing episodes, it does not alter the natural history of the disorder.