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Bronchodilator responsiveness in infants with bronchiolitis
R S Tepper1, D Rosenberg, H Eigen
1Indiana University School of Medicine, Department of Pediatrics, Indianapolis.
Insights
Inhaled metaproterenol improved airway function in some infants with bronchiolitis, particularly younger ones and females. However, the specific subgroup benefiting from this bronchodilator remains unclear due to age and gender influences.
Area of Science:
- Pediatrics
- Respiratory Medicine
- Pharmacology
Background:
- Bronchiolitis is a common viral respiratory infection in infants.
- Airway obstruction is a key feature of bronchiolitis.
- Bronchodilator use in bronchiolitis is controversial.
Purpose of the Study:
- To evaluate the effect of inhaled metaproterenol on airway function in infants with bronchiolitis.
- To identify factors influencing bronchodilator responsiveness in this population.
Main Methods:
- 34 infants with bronchiolitis underwent spirometry to measure forced expiratory flows (VmaxFRC) at functional residual capacity.
- Measurements were taken at baseline, after normal saline (NS) inhalation, and after metaproterenol inhalation.
- Flows were analyzed as Z-scores, comparing them to predicted values.
Main Results:
- Younger infants (< 2 months) and females showed improved airway function after metaproterenol.
- Outpatients, older infants (> 2 months), and males had more significant airway obstruction at baseline.
- Normal saline slightly decreased airflow; metaproterenol improved airflow in younger infants and females, but not older infants or males.
Conclusions:
- Inhaled metaproterenol can improve airway function in a subset of infants with bronchiolitis.
- Age and gender appear to be significant factors influencing response to metaproterenol.
- Further research is needed to clearly define the subgroup that benefits from bronchodilators in bronchiolitis.
Abstract:
We evaluated 34 infants with bronchiolitis, (17 of both genders; mean age, 4.6 mos; ranges, 0.7-14.5 mos). The 20 inpatients were significantly younger than the 14 outpatients (2.6 vs. 8.2 months, P < 0.05), and more females were inpatients. Forced expiratory flows at functional residual capacity (VmaxFRC) were obtained at baseline, after aerosolized normal saline (NS), and metaproterenol (0.025 mL/kg in 2 mL NS). Flows were expressed as Z-scores, the difference between the measured and predicted flows, divided by the standard deviation for the predicted value. At baseline, outpatients were more obstructed than inpatients (-1.64 vs. -0.95, P < 0.05), infants > 2 months old were more obstructed than infants < or = 2 months old (-1.54 vs. -0.80, P < 0.05), and males more than females (-1.45 vs. -1.02, P < 0.05). Following NS the whole group had a small but significant decrease in Z-scores (-1.23 to -1.31, P < 0.05). Following metaproterenol, the younger infants had significantly (P < 0.05) higher Z-scores compared to baseline and NS (-0.80 vs. -0.86 vs. -0.59). However, no significant changes occurred in older infants. Females also had an increased flow after metaproterenol and were less obstructed than after NS (-1.11 vs. -0.86, P < 0.015). In males no increased flows occurred after metaproterenol (-1.45 vs. -1.48). Bronchodilator responsiveness did not relate to severity of airway obstruction, history of family asthma, allergy, or passive smoke exposure. We conclude that inhaled metaproterenol improves airway function in a subgroup of infants with bronchiolitis, but the subgroup could not clearly be identified because age and gender were confounding factors.