Australian Regenerative Medicine Institute

Airway Response to a Bronchodilator in Healthy Parents of Infants With Bronchiolitis: Discussion

Our study shows that healthy parents of infants with bronchiolitis have a high prevalence of bronchial hyperresponsiveness as defined by the bronchodilator response. The number of parents (24.2 percent) with a positive bronchodilator response suggests that there may be a genetic predisposition to the development of bronchiolitis and airway hyperresponsiveness.
The design of our study included two subsequent steps. First, we showed an increased airway response to an inhaled bronchodilator in the parents of infants with bronchiolitis, compared with the response after placebo administration. Second, we observed that the former response was absent in a control group.
Our results cannot be influenced by the design of the study, since the spirometric maneuvers were always well performed at the baseline evaluation: at this step, there was no difference between patients and control subjects. Moreover, the study of parents of infants with bronchiolitis was double-blind, and it was performed on two subsequent days.
Our evaluation agrees with the results obtained by Gurwitz and associates. In their study, 33 percent of healthy relatives of children with a history of bronchiolitis and a bronchial hyperreactivity had a positive methacholine response  . Also Konig and Godfrey, studying healthy relatives of children with wheezy bronchitis, found an increased occurrence of exercise-induced bronchial lability, which was very similar to that observed in relatives of children with asthma.
Indeed, a bronchial hyperreactivity was observed by some investigators’ in surveys carried out on healthy individuals or parents belonging to families of asthmatic patients. These and other observations would suggest either a heritability component in bronchial hyperresponsiveness or an interrelationship between infections, in particular bronchiolitis, and bronchial lability. Thus, there may be a subgroup of infants with bronchiolitis who develop respiratory problems in response to a number of triggers besides viral infections.
Our interpretation should, however, be viewed with caution. In fact, there is epidemiologic evidence that airway hyperresponsiveness may be present in normal subjects and may be absent in asthmatic subjects. Moreover, our study design has not been able to establish a relationship between the airway responsiveness of the parents and the outcome of the infants with bronchiolitis during later childhood.
Hence, further studies are necessary to explain fully the importance of the increased bronchodilator response in parents of children with a history of bronchiolitis. Such surveys should include investigation of respiratory characteristics of a large number of parents, together with long-term follow-up of their infants with bronchiolitis. Indeed, only these studies might elucidate whether it is possible to predict the outcome of the infants with bronchiolitis from the enhanced response to an inhaled bronchodilator in their parents.

Category: Respiratory Symptoms

Tags: bronchodilator, bronchodilator response, hyperreactivity, hyperresponsiveness, infants bronchiolitis, lung function