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Factors related to methacholine airway responsiveness in children
D R Ownby1, E L Peterson, C C Johnson
1Department of Pediatrics, Medical College of Georgia, Augusta, Georgia, USA. downby@mail.mcg.edu
Insights
Airway responsiveness (AR) in children is not linked to height or age. Instead, lung function measures like FEF(25-75%) and FVC are key indicators of methacholine responsiveness.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
Background:
- Standard methacholine challenge protocols may not account for size variations in children.
- Observed age-related changes in airway responsiveness might be influenced by dose adjustments relative to body size.
Purpose of the Study:
- To investigate the relationship between anthropometric measures (height, age) and lung function parameters with airway responsiveness in children.
- To identify key predictors of methacholine responsiveness in a pediatric cohort.
Main Methods:
- Spirometry and methacholine challenge testing were performed on 471 children aged 6-8 years.
- Stepwise regression analysis was used to model airway responsiveness using various clinical and physiological variables.
Main Results:
- Height and age were not significantly associated with airway responsiveness after controlling for asthma or wheezing status.
- Baseline forced vital capacity (FVC), FEV(1)/FVC ratio, and forced expiratory flow rate between 25-75% of FVC (FEF(25-75%)) were significantly related to airway responsiveness.
- FEF(25-75%) emerged as the strongest predictor of airway responsiveness when all lung function measures were considered.
Conclusions:
- In children, lung function measures, particularly FEF(25-75%) and FVC, are significant determinants of methacholine responsiveness.
- Height and age are not significant independent predictors of airway responsiveness in this pediatric population.
Abstract:
Studies of airway responsiveness (AR) have typically used similar dose schedules of methacholine for adults and children despite large ranges in subject size. Reported declines in AR with increasing age in children could be due to maturational changes or to proportionately smaller doses of methacholine in taller (older) children. Other investigators have related both height and various measures of lung function to AR. We examined data related to AR in 471 children, aged 6 to 8 yr, from a birth cohort. Each child underwent spirometry followed by sequential challenge with five doses of methacholine, ranging from 0.025 to 25 mg/ml, given with a dosimeter. Continuous slope and end FEV(1)-change indexes of responsiveness were computed. Using stepwise regression modeling, we found no significant association between AR and either height or age after entering a variable reflecting asthma or wheezing. In contrast, we found that baseline measures of FVC, FEV(1)/FVC, and FEF(25-75%) were significantly related to AR after controlling for other variables (p = 0.001). However, when all three of the latter measures were added to models, FEF(25-75%) was most closely related to AR. We conclude that after control for other variables, FEF(25-75%) and FVC, but not height, are significantly related to methacholine responsiveness in children.