TY - JOUR T1 - Interrupter resistance and oxygen saturation for methacholine challenge in young children JF - ERJ Open Research JO - erjor DO - 10.1183/23120541.00025-2015 VL - 1 IS - 2 SP - 00025-2015 AU - Nicole Beydon AU - Iulia Marian Y1 - 2015/10/01 UR - http://openres.ersjournals.com/content/1/2/00025-2015.abstract N2 - In young children unable to perform reliable and reproducible spirometry, non-cooperative lung function techniques are necessary to measure bronchial hyperreactivity (BHR) during bronchial challenge [1]. Measuring the decrease in transcutaneous partial pressure of oxygen (PtcO2) is a robust technique that detects increased ventilation–perfusion mismatch during bronchial challenge [2] in preschool and school-aged children [3–5], and a 20% decrease in PtcO2 correlates to a 20% forced expiratory volume in 1 s (FEV1) decrease in children aged 6–14 years [3] and in adults (with correlation to arterial oxygen tension) [6]. When neither spirometry nor PtcO2 is available, other BHR outcomes can be measured such as wheezing that appears for mean±sd decreases of −44.7±14.5% in FEV1 and −6.3±2.7% in transcutaneous saturation of oxygen (SpO2) [7]. Respiratory resistances are easy to measure [8–10] but the relevant threshold for BHR is not yet defined and an at least 35% increase variably correlates with PtcO2 changes [8, 11]. First, we aimed to better study two alternative outcomes (i.e. interrupter resistance (Rint) and SpO2) and challenge the current recommendations [1] of measuring resistance during inspiration (as opposed to measuring during expiration for reversibility testing [12]), because the physiological expiratory glottis closure can be enhanced during bronchial challenge-induced bronchoconstriction and specific extrathoracic airway reactivity to bronchoconstrictor agents can occur. Second, we wished to evaluate the proposed thresholds for Rint and SpO2 (+35% and −5% baseline, respectively), as only a 3% decrease is considered to be significant in sleep studies and a mean±sd SpO2 decrease of −5.2±3.1% corresponds to a much larger than 20% decrease in FEV1 in 5–8-year-old asthmatic children (−33.3±7.4% decrease in FEV1) [13].Inspiratory Rint better detects BHR than expiratory Rint and might better match PD20PtcO2 changes http://ow.ly/TrMvBWe are grateful to Michèle Boulé, Houda Guillo, Marc Koskas, Marie-Claude La Rocca, Lucia Maingot and Noria Medjahdi for their help in recruiting the children, and to Claire Goaguen, Pascal Jacquemart, Valérie Le Bail, Isabelle Schmit and Françoise Vallée (APHP, hôpital Armand Trousseau, Paris, France) for technical assistance. We thank Corinne Alberti (Robert Debré Hospital, Paris, France) for her help with the statistical analysis and Evan Knight for his help in preparing this manuscript. ER -