Airway responsiveness in infants following bronchiolitis
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R S Tepper1, D Rosenberg, H Eigen
1James Whitcomb Riley Hospital for Children, Department of Pediatrics, Indiana University School of Medicine, Indianapolis.
Insights
Infants recovering from bronchiolitis show increased airway responsiveness, indicating a persistent effect of the illness. This heightened response, measured by methacholine challenges, suggests potential long-term respiratory implications for affected infants.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
Background:
- Bronchiolitis is a common viral respiratory infection in infants.
- Long-term effects of bronchiolitis on infant lung function are not fully understood.
Purpose of the Study:
- To assess airway responsiveness in infants following bronchiolitis.
- To compare airway responsiveness between infants with and without a history of bronchiolitis.
Main Methods:
- Airway responsiveness was measured using methacholine inhalation challenges in infants aged 4 and 10 months.
- Pulmonary function was assessed via partial expiratory flow-volume curves (VmaxFRC).
- Key metrics included threshold concentration (log TC) and concentration for 30% flow reduction (log PC30).
Main Results:
- Infants post-bronchiolitis exhibited lower baseline VmaxFRC compared to controls.
- Bronchiolitic infants demonstrated significantly heightened airway responsiveness (lower log TC and log PC30, steeper log SPC30).
- Bronchiolitis was a significant independent factor for heightened responsiveness at 10 months post-infection.
Conclusions:
- Infants show persistent heightened airway responsiveness after bronchiolitis.
- This suggests a potential for altered lung development or increased susceptibility to respiratory issues.
- Bronchiolitic infants do not show the typical age-related decline in airway responsiveness.
Abstract:
Airway responsiveness to inhaled methacholine was assessed in 18 infants, 4 and 10 months old, following bronchiolitis. Pulmonary function was measured from partial expiratory flow-volume curves generated by the rapid compression technique. Sleeping infants inhaled increasing concentrations of methacholine until maximal expiratory flows at functional residual capacity (VmaxFRC) decreased by 30% or 2.5 mg/mL was inhaled. Airway responsiveness was quantitated by: 1) the threshold concentration (log TC) required to decrease VmaxFRC by 2 standard deviations from baseline; 2) the concentration required to decrease VmaxFRC by 30% (log PC30); and 3) the slope of the dose-response curve between TC and PC30 (log SPC30). At both the first and second evaluation, the bronchiolitic infants had lower baseline VmaxFRC (% pred.) than 24 control infants. In addition, the bronchiolitic infants had heightened airway responsiveness compared to controls, demonstrating lower values for logTC and logPC30 and steeper slopes to their dose-response curves (logSPC30). After accounting for the relationship between airway responsiveness and age, the occurrence of bronchiolitis was found to be a significant independent factor 10 months but not 4 months following bronchiolitis. The bronchiolitic infants did not demonstrate the decline in airway responsiveness with increasing age that occurs in normal infants. We conclude that infants exhibit heightened airway responsiveness following bronchiolitis.