Recurrent Wheezing in Infants, Toddlers, and Preschoolers
Miles Weinberger, MD, FAAP
•Bronchiolitis is the name given to the first episode of symptomatic airway obstruction in infancy and is associated with lower respiratory tract infection.
•The affected infant typically presents with increased work of breathing manifested by retractions and associated with polyphonic wheezing heard audibly, with or without a stethoscope.
•The term bronchiolitis should not be applied to repeated episodes of wheezing that are seen in infants and toddlers with an asthma phenotype.
•Asthma includes several phenotypical disorders that share a common end-organ pathway, characterized by an increased responsiveness of the trachea and bronchi to various stimuli and manifested by a widespread narrowing of the airways that changes in severity, either spontaneously or as a result of therapy.
•Bronchial smooth muscle constriction causes narrowing of the airways.
•Airway inflammation in predisposed individuals with mucosal edema and mucous secretions results in decreased lumen diameter of the airways.
•Airway responsiveness to various stimuli increases.
•Airway obstruction results from inflammation and bronchospasm.
•Evidence for a defect of innate immunity related to deficient airway epithelial interferon production seems to be why common cold viruses, rhinovirus, respiratory syncytial virus, coronavirus, and others cause infection and inflammation of the lower airways, whereas those without such a defect have only typical upper respiratory symptoms commonly associated with a cold.
•The sequence of symptoms during an exacerbation (which may or may not progress beyond cough and/or wheezing) are as follows.
—Wheezing, an expiratory musical sound
—Increased work of breathing, manifested by intercostal, suprasternal, and substernal retractions
—Hypoxemia from continued perfusion of poorly ventilated areas of the lung that result from areas of increased airway obstruction
—Respiratory failure manifested by increased PCO2
—Asphyxia and death
•Symptoms vary greatly in severity, from mild to life-threatening.
•Frequency of symptoms varies greatly, from occasional to frequently episodic to continuously persistent.
•Protracted bacterial bronchitis, an infection in the peripheral airways from the same bacteria that causes otitis media, is primarily seen in infants and toddlers; it is commonly associated with airway malacia, which may be an important contributing mechanism.
•Cystic fibrosis (see Chapter 67, Cystic Fibrosis) is a congenital disease caused by a defect in innate immunity of the airways that results in chronic bacterial infection, with inflammation and viscous mucous that interferes with airway clearance.
•Primary ciliary dyskinesia (see Chapter 70, Primary Ciliary Dyskinesia) is a congenital disease that results in absent ciliary mucous airway clearance.
•Anatomic causes of cough and/or wheeze include tracheal or bronchial malacia and intra-airway polyps.
Diagnostic Considerations and Characterizing the Clinical Pattern
•Obtain a careful and detailed history, including
—Age of onset of symptoms
—Description of symptoms
—Duration of symptoms if currently symptomatic
—Chronic and persistent or intermittent clinical pattern
—Frequency of symptomatic periods if not persistent since onset
—Duration of symptoms when they occur
—Presence of related comorbidities
▪Immunoglobulin E (IgE)–mediated food allergies
• Diagnosis of asthma is supported by complete response of current symptoms to an observed initial administration of an inhaled bronchodilator such as albuterol, but failure to respond to a bronchodilator does not exclude the diagnosis of asthma, since albuterol has no effect on the airway obstruction from airway inflammation.
•The diagnosis of asthma is supported by complete response of current prolonged or increasing symptoms to a short course (7–10 days maximum) of an oral corticosteroid.
•Response to a prolonged course of an inhaled corticosteroid is not a reliable means of establishing the diagnosis.
•Once the diagnosis is confirmed, use the obtained historical information to identify common asthma phenotypes present in the preschool child on the basis of the clinical pattern.
—The recurrent viral respiratory infection (VRI)–induced pattern of asthma has a complete clearing between acute episodes.
▪This is the most common asthma phenotype, particularly in the preschool-aged child.
▪Fall and spring exacerbations are most common because of the seasonality or the common cold viruses.
▪These children are typically much more free of symptoms during the summer months, when VRIs are less frequent.