• Hayley Lewthwaite, Omar Elsewify, Frank Niro, Jean Bourbeau, Jordan A Guenette, François Maltais, Darcy D Marciniuk, Denis E O'Donnell, Benjamin M Smith, Michael K Stickland, Wan C Tan, Dennis Jensen, CanCOLD Collaborative Research Group, and Canadian Respiratory Research Network.
• Clinical Exercise and Respiratory Physiology Laboratory, Department of Kinesiology and Physical Education, Faculty of Education, McGill University, Montréal; UniSA: Allied Health and Human Performance, Innovation, IMPlementation And Clinical Translation in Health (IIMPACT), University of South Australia, Adelaide, SA, Australia. Electronic address: Hayley.Lewthwaite@mcgill.ca.
• Chest. 2021 May 1; 159 (5): 1922-1933.

BackgroundPhysiologic and symptom responses at the ventilatory threshold (Tvent) during incremental cardiopulmonary exercise testing (CPET) can provide important prognostic information.Research QuestionThis study aimed to develop an updated normative reference set for physiologic and symptom responses at Tvent during cycle CPET (primary aim) and to evaluate previously recommended reference equations from a 1985 study for predicting Tvent responses (secondary aim).Study Design And MethodsParticipants were adults 40 to 80 years of age who were free of clinically relevant disease from the Canadian Cohort Obstructive Lung Disease. Rate of oxygen consumption (V˙O2) at Tvent was identified by two independent raters; physiologic and symptom responses corresponding to V˙O2 at Tvent were identified by linear interpolation. Reference ranges (5th-95th percentiles) for responses at Tvent were calculated according to participant sex and age for 29 and eight variables, respectively. Prediction models were developed for nine variables (oxygen pulse, V˙O2, rate of CO2 production, minute ventilation, tidal volume, inspiratory capacity, end-inspiratory lung volume [in liters and as percentage of total lung capacity], and end-expiratory lung volume) using quantile regression, estimating the 5th (lower limit of normal), 50th (normal), and 95th (upper limit of normal) percentiles based on readily available participant characteristics. The two one-sided test of equivalence for paired samples evaluated the measured and 1985-predicted V˙O2 at Tvent for equivalence.ResultsReference ranges and equations were developed based on 96 participants (49% men) with a mean ± SD age of 63 ± 9 years. Mean V˙O2 at Tvent was 50% of measured V˙O2 peak; the normal range was 33% to 66%. The 1985 reference equations overpredicted V˙O2 at Tvent: mean difference in men, -0.17 L/min (95% CI, -0.25 to -0.09 L/min); mean difference in women, -0.19 L/min (95% CI, -0.27 to -0.12 L/min).InterpretationA contemporary reference set of CPET responses at Tvent from Canadian adults 40 to 80 years of age is presented that differs from the previously recommended and often used reference set from 1985.Trial RegistryClinicalTrials.gov; No.: NCT00920348; URL: www.clinicaltrials.gov.Copyright © 2020 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

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