PT - JOURNAL ARTICLE AU - Kanika Jetmalani AU - Nathan J. Brown AU - Chantale Boustany AU - Brett G. Toelle AU - Guy B. Marks AU - Michael J. Abramson AU - David P. Johns AU - Alan L. James AU - Michael Hunter AU - Arthur W. Musk AU - Norbert Berend AU - Claude S. Farah AU - David G. Chapman AU - Cindy Thamrin AU - Gregory G. King TI - Normal limits for oscillometric bronchodilator responses and relationships with clinical factors AID - 10.1183/23120541.00439-2021 DP - 2021 Oct 01 TA - ERJ Open Research PG - 00439-2021 VI - 7 IP - 4 4099 - http://openres.ersjournals.com/content/7/4/00439-2021.short 4100 - http://openres.ersjournals.com/content/7/4/00439-2021.full SO - erjor2021 Oct 01; 7 AB - Introduction We aimed to determine normal thresholds for positive bronchodilator responses for oscillometry in an Australian general population sample aged ≥40 years, to guide clinical interpretation. We also examined relationships between bronchodilator responses and respiratory symptoms, asthma diagnosis, smoking and baseline lung function.Methods Subjects recruited from Sydney, Melbourne and Busselton, Australia, underwent measurements of spirometry, resistance (Rrs6) and reactance (Xrs6) at 6 Hz, before and after inhalation of salbutamol 200 μg. Respiratory symptoms and/or medication use, asthma diagnosis, and smoking were recorded. Threshold bronchodilator responses were defined as the fifth percentile of decrease in Rrs6 and 95th percentile increase in Xrs6 in a healthy subgroup.Results Of 1318 participants, 1145 (570 female) were analysed. The lower threshold for ΔRrs6 was −1.38 cmH2O·s·L−1 (−30.0% or −1.42 Z-scores) and upper threshold for ΔXrs6 was 0.57 cmH2O·s·L−1 (1.36 Z-scores). Respiratory symptoms and/or medication use, asthma diagnosis, and smoking all predicted bronchodilator response, as did baseline oscillometry and spirometry. When categorised into clinically relevant groups according to those predictors, ΔXrs6 was more sensitive than spirometry in smokers without current asthma or chronic obstructive pulmonary disease (COPD), ∼20% having a positive response. Using absolute or Z-score change provided similar prevalences of responsiveness, except in COPD, in which responsiveness measured by absolute change was twice that for Z-score.Discussion This study describes normative thresholds for bronchodilator responses in oscillometry parameters, including intra-breath parameters, as determined by absolute, relative and Z-score changes. Positive bronchodilator response by oscillometry correlated with clinical factors and baseline function, which may inform the clinical interpretation of oscillometry.Normative values for bronchodilator responses measured by oscillometry were derived. Responsiveness related to clinical factors and baseline function. Reactance was more sensitive in detecting bronchodilator response than spirometry mild airways disease. https://bit.ly/3wtWVeV