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Heightened airway responsiveness in normal female children compared with adults
R S Tepper1, J Stevens, H Eigen
1James Whitcomb Riley Hospital for Children, Department of Pediatrics, Indiana University School of Medicine, Indianapolis.
Insights
Female children exhibit greater airway responsiveness to methacholine than adults, irrespective of body size or lung function. This finding highlights developmental differences in the airways, suggesting maturation influences reactivity.
Area of Science:
- Pulmonology
- Pediatric Respiratory Medicine
- Physiology
Background:
- Airway responsiveness is thought to decrease with age, but studies are often confounded by body size and maturation differences.
- Previous research comparing pediatric and adult populations has yielded inconclusive results regarding airway responsiveness due to confounding variables.
Purpose of the Study:
- To investigate the effect of maturation on airway responsiveness by comparing normal female children and adults matched for body size.
- To determine if differences in airway responsiveness between children and adults are attributable to maturation rather than physical size.
Main Methods:
- Bronchial challenge tests using increasing concentrations of methacholine were administered to female children (mean age 13.6 years) and adults (mean age 42.4 years).
- Subjects were matched for body size to isolate the effect of maturation.
- Lung volumes (TGV, RV, TLC) and flow-volume curves (FEV1, FEF25-75, FVC) were assessed at baseline.
Main Results:
- Children showed a significantly greater percentage decline in FEV1 (forced expiratory volume in 1 second) compared to adults (17% vs 7%, p < 0.03).
- While the percentage decline in FEF25-75 (forced expiratory flow rate between 25% and 75% of vital capacity) was greater in children, the difference was not statistically significant (35% vs 20%, p < 0.10).
- Adults demonstrated a plateau in their methacholine dose-response curves more frequently than children for both FEV1 and FEF25-75.
Conclusions:
- Normal female children possess greater airway responsiveness to inhaled methacholine compared to adults.
- This heightened responsiveness in children is not linked to differences in baseline lung size, airway caliber, or the methacholine dose administered.
- Maturation appears to be a significant factor influencing airway responsiveness, with younger individuals exhibiting greater reactivity.
Abstract:
Studies have suggested that airway responsiveness declines with maturation; however, studies comparing infants, children, and adults are confounded by differences in size as well as maturation. Therefore, to determine whether maturation has a significant affect on airway responsiveness, we compared normal female children (n = 9; mean age = 13.6 yr) and adults (n = 7; mean age = 42.4 yr) who were matched for body size. Bronchial challenge tests were performed with increasing methacholine concentrations to a maximum of 30 mg/ml. At baseline, there were no significant differences between the two groups in lung volumes (TGV, RV, TLC) or flow-volume curves (FEV1, average forced expiratory flow rate between 25% and 75% of the vital capacity [FEF25-75], FVC). All subjects but one adolescent completed the challenge (30 mg/ml). The children had a greater percentage decline from baseline in FEV1 than the adults (17 versus 7%, p < 0.03). The percentage decline in FEF25-75 was greater for the children than for the adults, but the difference was not statistically significant (35 versus 20%, p < 0.10). Compared with the children, the adults more often demonstrated a plateau in their dose-response curves for FEV1 (22 versus 86%) and for FEF25-75 (33 versus 100%). We conclude that normal female children have a greater airway responsiveness to inhaled methacholine than do adults, and that this difference is not related to baseline lung size, airway caliber, or delivered methacholine dose.