Bronchial reactivity to inhaled methacholine in infants with asthma and age-matched controls

To evaluate bronchial hyperresponsiveness (BHR) in infants with asthma and the influence of aging on BHR during the infantile period, bronchial reacti vity to inhaled methacholine (BRm) in infants was monitored using the trans cutaneous oxygen pressure (tcPO(2)) method. One hundred thirty-seven infant s with asthma (from 1 to 5 years, mean 3.4 years) and 97 age-matched childr en without chronic respiratory diseases (from 6 months to 5 years, mean 2.1 years) were enrolled in this study. Consecutive doses of methacholine were doubled until a 10% decrease in tcPO(2) from the baseline was reached. The cumulative dose of methacholine at the inflection point of tcPO(2) (D-min- PO2) was considered to represent the reactivity of tCPO(2) to inhaled metha choline. D-min-PO2 values in the asthma groups were lower than those in the control groups in each year-group from 1 to 5. There was no statistical di fference in D-min-PO2 among the 1-4-year-old asthma groups, but D-min-PO2 i n the 5-year-old asthma group was significantly lower than D-min-PO2 in the 1-4-year-old asthma groups. The same age-related change in D-min-PO2 was a lso seen in the control groups. There was no difference in age-related D-mi n-PO2 change between the female group and the male group. We concluded that BRm in asthmatic children increases during the infantile period, and that the age-related changes in BRm, observed in both asthmatic and control infa nts, may have an effect on the clinical symptoms of asthma during childhood .