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The effect of size and age of subject on airway responsiveness in children
P N Le Souëf1, M R Sears, D Sherrill
1Department of Respiratory Medicine, Princess Margaret Hospital for Children, Perth, Australia.
Insights
Airway responsiveness (AR) in children is size dependent, with smaller children showing higher responsiveness. This suggests current testing methods may overestimate AR in younger or smaller individuals.
Area of Science:
- Pediatric Pulmonology
- Respiratory Physiology
- Longitudinal Cohort Studies
Background:
- Standard airway responsiveness (AR) assessments in children use fixed dosages.
- This approach does not account for significant variations in subject size within age groups.
Purpose of the Study:
- To investigate if airway responsiveness (AR) in children is dependent on physical size.
- To examine AR variations within the same age group and across different ages.
Main Methods:
- Longitudinal analysis of 818 children (ages 9-15) from a birth cohort of 1,037.
- Spirometry and a four-dose methacholine inhalation challenge were performed.
- A continuous slope index of methacholine responsiveness was calculated.
Main Results:
- Airway responsiveness (AR) was lowest in taller children, irrespective of age.
- Boys exhibited higher AR than girls.
- AR tended to decrease with age in children reporting wheeze.
Conclusions:
- Airway responsiveness (AR) is significantly influenced by physical size in children.
- Smaller or younger children may experience a disproportionately higher methacholine dose, potentially inflating AR measurements.
- Current AR assessment methodologies may require size-adjustment for accurate interpretation.
Abstract:
Methodologies used to assess airway responsiveness (AR) in children administer the same dosage schedule to all children despite the great range in the size of subjects. The aim of this study was to examine the hypothesis that the level of AR is size dependent within same-age cohorts and between different ages. Among a birth cohort of 1,037 New Zealand children participating in a longitudinal study, 818 had at least two measurements of airway responsiveness between ages 9 and 15 yr. Each child performed spirometry and a four-dose methacholine inhalation test. A continuous slope index of methacholine responsiveness was computed. AR slope indexes were analyzed using longitudinal methods, which included an indicator variable for subjects who reported having any wheeze. AR was lowest in both males and females in the upper quartile for height than those in the lower quartile, independently of age. AR tended to be higher (responded to lower concentrations of methacholine) in boys than girls and to decline with age among wheezers. The greater level of responsiveness in smaller or younger children could be explained by these individuals having received a dose of methacholine that was relatively large for their size.