Lewthwaite H; Elsewify O; Niro F; Bourbeau J; Guenette JA; Maltais F;
Marciniuk DD; O’Donnell DE; Smith BM; Stickland MK; Tan WC; Jensen D;
Chest. 159(5):1922-1933, 2021 05.
RESEARCH QUESTION: This 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
STUDY DESIGN AND METHODS: Participants 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 (VO2) at Tvent was
identified by two independent raters; physiologic and symptom responses
corresponding to VO2 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, VO2, 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
VO2 at Tvent for equivalence.
RESULTS: Reference ranges and equations were developed based on 96
participants (49% men) with a mean +/- SD age of 63 +/- 9 years. Mean VO2
at Tvent was 50% of measured VO2 peak; the normal range was 33% to 66%.
The 1985 reference equations overpredicted VO2 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).
INTERPRETATION: A 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.