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Comparison of maximal airway narrowing to methacholine between children and adults
S de Pee1, M C Timmers, J Hermans
1Dept of Pulmonology, University Hospital Leiden, The Netherlands.
Insights
Maximal airway narrowing to methacholine is similar in children and adults with asthma. This study found no difference in the maximal response to inhaled bronchoconstrictors between pediatric and adult populations.
Area of Science:
- Pulmonology
- Pediatric Respiratory Medicine
- Clinical Physiology
Background:
- Bronchial hyperresponsiveness (BHR) in adults involves increased sensitivity and maximal response to bronchoconstrictors.
- The relationship between sensitivity and maximal airway narrowing in children with BHR remains unclear.
Purpose of the Study:
- To investigate the maximal degree of airway narrowing to methacholine in children (7-12 yrs) and adults.
- To compare the maximal methacholine response between nonasthmatic and asthmatic children and adults.
Main Methods:
- Subjects (19 children, 19 adults; normal and asthmatic) underwent two methacholine challenge tests.
- Dose-response curves were analyzed for provocative dose (PD20) and maximal response (MFEV1).
- Response measured as percentage fall in forced expiratory volume in one second (FEV1).
Main Results:
- Plateaus in dose-response curves were observed in 13 children and 9 adults.
- An inverse relationship between log PD20 and MFEV1 was found, similar in children and adults (p > 0.15).
- Maximal response (MFEV1) did not significantly differ between pediatric and adult subjects.
Conclusions:
- For a given bronchial sensitivity, the maximal degree of airway narrowing to inhaled methacholine is comparable between children and adults.
- This suggests similar upper limits of airway narrowing response regardless of age in this context.
Abstract:
Bronchial hyperresponsiveness in adults is characterized by an increased sensitivity as well as an elevated maximal response to inhaled bronchoconstrictors. In children, however, it is unknown whether the maximal response increases with increasing sensitivity. We investigated the maximal degree of airway narrowing to methacholine in nonasthmatic and asthmatic children (7-12 yrs), and compared it to that in adults. Nineteen children (9 normals, 10 asthmatics) and 19 adults (8 normals, 11 asthmatics) were selected in order to cover a wide distribution of bronchial responsiveness. All subjects underwent 2 methacholine challenge tests on separate days, by inhaling doubling doses using a standardized dosimeter technique (up to a noncumulative dose of 59 mumol). The response was measured by forced expiratory volume in one second (FEV1) and expressed as a percentage fall from baseline value. The complete dose-response curves were characterized by their position (PD20, the provocative dose causing a 20% fall in FEV1) and maximal response (MFEV1, the mean response on the plateau, defined as greater than or equal to 2 points within a 5% response range). Plateaus were observed in 13 children and 9 adults, the coefficient of repeatability of MFEV1 being 10.8 and 10.4% fall, respectively. There was an inverse relationship between log PD20 and MFEV1, which did not differ between children and adults (p greater than 0.15). In most of the asthmatic children and adults the plateau could not be measured (exceeding 50% fall in FEV1) if PD20 was less than 1 mumol. We conclude that, for a given bronchial sensitivity, the maximal response to inhaled methacholine is similar between children and adults.(ABSTRACT TRUNCATED AT 250 WORDS)