Am. J. Respir. Crit. Care Med., Vol 152, No. 3, Sep 1995, 906-910.
Age-related changes in bronchial hyperreactivity to methacholine in asthmatic children
H Mochizuki, M Shigeta, M Kato, S Maeda, T Shimizu and A Mirokawa
Department of Pediatrics, Gunma University School of Medicine, Maebashi, Japan.
To evaluate the influence of aging on bronchial hyperreactivity (BHR)
during the childhood period, age-related changes in bronchial reactivity to
methacholine (BRm) in children from 2 to 13 yr of age were studied using
the same method, employing a methacholine inhalation challenge with
transcutaneous oxygen pressure (tcPO2) monitoring. Three hundred and
thirty-nine asthmatic subjects (male:female = 200:139, aged [mean +/- SEM]
7.2 +/- 0.2 yr) and 107 age-matched controls (male:female = 55:52, aged 5.3
+/- 0.3 yr) were enrolled in this study. TcPO2 was measured by a tcPO2
monitor, and subsequent doses of methacholine were then doubled until a 10%
decrease in tcPO2 from its baseline value was reached. The cumulative dose
of methacholine at the inflection point of tcPO2 (Dmin-PO2) was considered
to represent the BRm. For the sake of comparison, respiratory resistance
(Rr) in subjects more than 6 yr old was measured by the oscillation
technique during methacholine inhalation challenge, and the threshold point
of Rr (Dmin-Rr) was also considered to represent the BRm. In the asthmatic
children aged 2 to 7 yr, Dmin-PO2 decreased significantly from 12.2 +/- 2.1
to 3.1 +/- 0.8 units, but after age 8 yr the values gradually increased
from 3.1 +/- 0.7 to 6.4 +/- 1.6 units. In children aged 6 to 13 yr, Dmin-Rr
showed the same increase as Dmin-PO2, from 2.0 +/- 0.5 to 5.8 +/- 1.4
units. These age-related changes in BRm reflected in both Dmin-PO2 and
Dmin-Rr were also seen in the age-matched controls.(ABSTRACT TRUNCATED AT
250 WORDS)
