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Increased peak flow variability in children with asymptomatic hyperresponsiveness
P G Gibson1, S Mattoli, M R Sears
1Dept of Medicine, St Joseph's Hospital, Hamilton, Ontario, Canada.
Insights
Asymptomatic children with methacholine airway hyperresponsiveness show increased diurnal peak expiratory flow (PEF) variability, similar to asthmatic children. This suggests mild airflow obstruction even without asthma symptoms.
Area of Science:
- Pediatric Pulmonology
- Respiratory Medicine
- Allergy and Immunology
Background:
- Increased methacholine airway responsiveness is detected in children without current or past asthma symptoms.
- The clinical significance of this airway hyperresponsiveness in asymptomatic children remains unclear.
- Investigating associated airflow obstruction markers like peak expiratory flow (PEF) variability is crucial.
Purpose of the Study:
- To determine if airway hyperresponsiveness in asymptomatic children is associated with abnormal peak expiratory flow (PEF) variability.
- To compare PEF diurnal variation in asymptomatic hyperresponsive children with symptomatic asthmatic children and normal controls.
- To assess the perception of airway constriction in these groups.
Main Methods:
- Studied 12 asymptomatic children with methacholine hyperresponsiveness, 12 symptomatic asthmatic children, and 12 normal children (aged 9-14).
- Examined diurnal variation of peak expiratory flow (PEF) and response to inhaled bronchodilator in all groups.
- Assessed perception of methacholine-induced airway constriction.
Main Results:
- Asymptomatic hyperresponsive children exhibited increased diurnal PEF variation (9.3%), comparable to symptomatic asthmatics (10.7%) and greater than normal children (5.7%).
- Methacholine-induced airway constriction was perceived as symptoms in subjects from all groups.
- This indicates asymptomatic hyperresponsive children experience mild variable airflow obstruction.
Conclusions:
- Asymptomatic children with methacholine airway hyperresponsiveness demonstrate evidence of mild variable airflow obstruction.
- Increased diurnal PEF variability in these children suggests subclinical airway dysfunction.
- Lack of symptoms may relate to insufficient stimulus or absence of eosinophilic airway inflammation.
Abstract:
The relevance of increased methacholine airway responsiveness detected in children with no current or past symptoms of asthma is not known. We wished to determine whether the presence of airway hyperresponsiveness in asymptomatic children is also associated with abnormal variability of peak expiratory flow (PEF). In 12 asymptomatic children with methacholine hyperresponsiveness, we examined the diurnal variation of peak expiratory flow (PEF) and response to inhaled bronchodilator. Twelve asthmatic children with a comparable range of methacholine hyperresponsiveness, and 12 normal children without methacholine responsiveness, were used as positive and negative controls. The children were aged 11 (range 9-14) yrs. The mean diurnal variation of PEF in those children with asymptomatic hyperresponsiveness was increased at 9.3%, to a degree comparable to the symptomatic asthmatic children (10.7%), and greater than the normal children (5.7%). Methacholine stimulated airway constriction was associated with symptoms in subjects from each group, indicating that the children were capable of perceiving airway constriction. We conclude that asymptomatic children with methacholine airway hyperresponsiveness have other evidence of mild variable airflow obstruction with increased diurnal PEF variability, and can perceive airflow limitation. The lack of symptoms in the children with airway hyperresponsiveness could be due to an insufficient stimulus to cause symptomatic obstruction, or the absence of eosinophilic airway inflammation, which may be a requirement for the development of symptomatic airway hyperresponsiveness.