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Bronchial hyperresponsiveness before and after the diagnosis of bronchial asthma in children
H Mochizuki1, M Shigeta, H Arakawa
1Department of Pediatrics, Gunma University School of Medicine, Maebashi, Gunma, Japan. mochihi@akagi.sb.gunma-u.ac.jp
Insights
Bronchial hyperresponsiveness (BHR) in children with asthma appears to be acquired after experiencing asthma attacks, rather than being present from birth. This finding suggests a potential link between asthma episodes and the development of BHR.
Area of Science:
- Pediatric Pulmonology
- Allergy and Immunology
- Respiratory Medicine
Background:
- Infantile wheezing diseases are linked to bronchial hyperresponsiveness (BHR).
- Viral infections and genetic predispositions may trigger or induce BHR in infants.
- The exact timing of BHR acquisition in childhood asthma remains unclear.
Purpose of the Study:
- To determine the age at which bronchial hyperresponsiveness (BHR) is acquired in children diagnosed with asthma.
- To investigate whether BHR is congenital or develops after asthma attacks.
Main Methods:
- A methacholine inhalation challenge using transcutaneous oxygen pressure (tcPO(2)) monitoring was conducted on 205 children aged 6 months to 6 years.
- 18 children who developed asthma during follow-up (group N-A) were tested twice, along with control groups (N-N and A-A).
- BHR was quantified by the minimal dose of methacholine (Dmin-PO(2)) causing a 10% decrease in tcPO(2).
Main Results:
- No significant change in Dmin-PO(2) was observed between the first and second challenges in control groups (N-N and A-A).
- The Dmin-PO(2) significantly decreased from the first to the second challenge in the N-A group, indicating acquired BHR.
- Initial BHR in newly diagnosed asthmatics (N-A) was similar to non-asthmatic controls (N-N), while later BHR resembled that of established asthmatics (A-A).
Conclusions:
- Data suggest that bronchial hyperresponsiveness (BHR) in many infants with asthma is acquired after experiencing multiple asthma attacks.
- This implies that asthma attacks may play a role in the development or exacerbation of BHR in early childhood.
- Further research into the mechanisms of BHR acquisition post-asthma onset is warranted.
Objective:
To assess at what age bronchial hyperresponsiveness (BHR) is acquired in children with asthma.
Background:
A relationship between BHR and infantile wheezing diseases has been reported. Infants with a genetic predisposition to atopy are more likely to wheeze with respiratory viral infection or bronchiolitis, and it is suspected that the continued BHR after the first attack of asthma may be induced or triggered by some viral infections. Also, recent studies have reported the existence of atopic and BHR-related genes. However, whether BHR is congenital or acquired after asthma attacks, and when BHR in children with asthma is established or acquired remain unclear.
Methods:
We performed methacholine inhalation challenge using a transcutaneous oxygen pressure (tcPO(2)) monitoring system in 205 children without asthma from 6 months to 6 years of age. During follow-up, 18 of these participants were diagnosed with asthma (group N-A). This group and 15 age-matched children without asthma (group N-N) were tested twice using methacholine inhalation challenge. For comparison, 39 age-matched atopic-type asthmatic children (group A-A) were also given the inhalation challenge twice. Methacholine inhalation challenge using a tcPO(2) monitoring system was performed while the participants were asleep in the supine position. Sequential doses of inhaled methacholine delivered by oxygen mask 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) (minimal dose of methacholine [Dmin]-PO(2)) was considered to represent BHR.
Results:
In groups N-N and A-A, there was no difference in Dmin-PO(2) between the first and second challenge. However, the Dmin-PO(2) in group N-A significantly decreased from the first challenge to the second challenge. There was no significant difference between the Dmin-PO(2) in group N-N and the first Dmin-PO(2) in group N-A; or between the Dmin-PO(2) in group A-A and the second Dmin-PO(2) in group N-A.
Conclusions:
These data suggest that BHR in many infants with asthma is acquired after several asthma attacks.bronchial hyperresponsiveness, childhood asthma, methacholine inhalation challenge, transcutaneous oxygen pressure.