Abstract
Background It is recommended to measure interrupter resistance during expiration (RintExp) for bronchodilation test and during inspiration (RintInsp) for bronchial hyperreactivity (BHR) detection, to minimize laryngeal influence. But no study assessed the clinical implication of using RintInsp rather than RintExp to detect BHR.
Objectives To compare RintInsp and RintExp ability to correctly detect BHR defined as a 20% decrease in transcutaneous partial pressure in oxygen (TcPO2), in young children.
Methods Prospective monocentre study in children referred for methacholine challenge because of non specific chronic respiratory symptoms, and unable to perform reliable spirometry. Baseline Rint (MicroMedical, UK) measurement lay within the normal range. Methacholine was administered using the dosimeter method (Atomisor, France). Rint changes were considered consistent to that of TcPO2 if there was a 35% Rint increase from the post-diluant value at the dose TcPO2 decreased ≥20% or a less than 35% Rint increase in children without BHR.
Results 14 children (7 girls, median age 5.7 years) performed the test and 9 had BHR between 50 and 400µg of methacholine. Consistency between TcPO2 and Rint was present in 9 (RintIns) and 4 (RintExp) children, with no false positive with RintIns (vs 3 with RintExp).
Conclusion Although Rint measurement cannot always, on its own, correctly detect BHR in young children, inspiratory measurement should be used as it is more often consistent with TcPO2 changes and do not falsely detect BHR compare to expiratory Rint measurement.
- © 2014 ERS