[Isocapnic hyperventilation test adjusted to child's resting ventilation rate]

In order to validate an Isocapnic Voluntary Hyperventilation (IVH) test applicable to daily practice and to adapt the stimulus to height, 9 healthy and 15 asthmatic children performed a Resting Ventilation Rate (RVR)-corrected IVH. They performed a three-minute IVH with room temperature dry air achieving twice (IVH2) and three times (IVH3) their RVR. Mean Maximal Expiratory Flow (MEF) in the middle half of Forced Vital Capacity (FVC) (MEF25-75%) and mean MEF at 25% of FVC (MEF25%) are decreased in the asthmatic group 10 minutes IVH3 (p = 0.02 and < 0.002) compared to healthy group. Mean FEV1 of both group are not different. Comparing Forced Expiratory Flows variation after IVH to baseline intrasubject coefficient of variation, sensitivity of the test is 80% and specificity 100% when variations of MEF25-75% and MEF25% together with FEV1 variations are considered. This suggests an easy way to adapt an hyperventilation stimulus to size and emphasizes the utility of taking account of MEF25-75% and MEF25% in detecting non specific bronchial hyperreactivity in asthmatic children.