What's new for seasonal wheezing (CME)

Key Points

A 3-month old male infant is brought to your office in mid-February for trouble breathing. This previously healthy full-term infant began showing symptoms of an upper respiratory infection three days ago but now has been having an intermittent cough and periods of respiratory distress. On physical exam he has a temperature of 101° F (38.4° C), a respiratory rate of 65 bpm, oxygen saturation of 95%, is alert and active with nasal congestion, mild intercostal retractions, and diffuse wheezes with good air movement on lung examination. The remainder of his exam is unremarkable.

The scenario described above is a common and frustrating one for pediatricians. An infant presenting with clinical symptoms that are consistent with viral bronchiolitis raises a variety of questions that have been the subject of numerous research studies. These questions include: Is there a need for diagnostic testing, either to confirm the clinical suspicion of viral disease or to rule out other etiologies or concomitant infections? What is the risk for this infant, and can we predict who will go on to have severe illness and require hospitalization or intensive care? What are the benefits of therapies such as bronchodilators and corticosteroids? What is the best way to counsel and communicate with families about what to expect?

Concern about these issues has led the American Academy of Pediatrics (AAP) and other professional organizations to summarize the available evidence, and provide guidance to clinicians about proven approaches to diagnosis and therapy.^1-3 This article presents a practical approach to these recommendations, be it in a hospital or office setting. We will focus in particular on the 2006 AAP Bronchiolitis Clinical Practice Guideline, as well as recently published studies.

Bronchiolitis facts: Good news and bad

Much has been learned about the etiology and epidemiology of bronchiolitis, but misconceptions can be a source of anxiety for families and clinicians. Parents, for example, may hear about respiratory syncytial virus (RSV) and be concerned about this sinister-sounding agent without understanding its ubiquitous nature. Thus, reviewing some basic facts about RSV may provide some reassurance.

Almost all children (90%) are infected with RSV during the first two years of life, primarily within the annual epidemic that usually peaks between December and March.² Most are limited to cold symptoms, but about one third will develop a lower respiratory infection (bronchiolitis) with varying degrees of mucus plugging, bronchospasm, and airway inflammation.

Approximately 70% of all bronchiolitis cases are attributed to RSV,⁴ with other possible causes including influenza, adenovirus, rhinovirus, and parainfluenza. Increased attention has also been paid to metapneumovirus, a recently discovered paramyxovirus. Clinical information is still emerging about metapneumovirus, but currently it appears to have a similar course to RSV. An examination of metapneumovirus samples banked from older studies, however, suggests that the virus is not actually a new agent and only accounts for about 5 to 15% of bronchiolitis cases.⁴

Perhaps one of the most concerning trends surrounding bronchiolitis has been the increase in hospital admissions. Hospitalization rates for bronchiolitis have more than doubled in recent decades, and bronchiolitis is the leading cvause of hospitalization for infants.⁵ On the other hand, recent studies suggest that deaths from bronchiolitis are much lower than older estimates, with currently fewer than 500 deaths nationwide annually.^5.6 The causes for increased hospitalization are unclear, but some have suggested that they relate to differences in admission criteria and the introduction of new technologies such as pulse oximetry.^7,8

Assessment and prediction

One of the greatest challenges for health care providers assessing a child with bronchiolitis is estimating the risk that the child will progress to severe disease. A few research studies have attempted to predict this progression, both in inpatient and outpatient settings.^9,10 A number of large prospective studies are currently underway, and much more data will be available in the next few years. The strongest risk factors appear to lie with young age (less than 12 weeks), underlying conditions including prematurity (less than 37 weeks gestation), cardiopulmonary disease, and immunodeficiency.