Bronchial Reactivity to Inhaled Methacholine in Infants with Asthma and Age-Matched Controls

Abstract

To evaluate bronchial hyperresponsiveness (BHR) in infants with asthma and the influence of aging on BHR during the infantile period, bronchial reactivity to inhaled methacholine (BRm) in infants was monitored using the transcutaneous oxygen pressure (tcPO₂) method. One hundred thirty-seven infants with asthma (from 1 to 5 years, mean 3.4 years) and 97 age-matched children 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 tcPO₂ from the baseline was reached. The cumulative dose of methacholine at the inflection point of tcPO₂ (D_min-PO₂) was considered to represent the reactivity of tcPO₂ to inhaled methacholine. 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 difference in D_min-PO₂ among the 1-4-year-old asthma groups, but D_min-PO₂ in 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 also seen in the control groups. There was no difference in age-related D_min-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 infants, may have an effect on the clinical symptoms of asthma during childhood.

Key Words:

• Bronchial hyperresponsiveness
• Infants with asthma
• Methacholine inhalation challenge
• Transcutaneous oxygen pressure