Repeatability and Meaningful Change of CPET Parameters in Healthy Subjects

Cardiopulmonary exercise testing (CPET) plays an important role in clinical medicine and research. Repeatability of CPET parameters has not been well characterized, but is important to assess variability and determine if there have been meaningful changes in a given CPET parameter.

We recruited 45 healthy subjects and performed two symptom-limited CPET within 30 d using a cycle ergometer. Differences in relevant CPET parameters between CPET-1 and CPET-2 were assessed using a paired t-test. Coefficient of variation (CoV) and Bland-Altman plots are reported. Factors that may be associated with variability were analyzed (sex, age, time of day, fitness level). The coefficient of repeatability was calculated for peak oxygen consumption (V˙O2) and V˙O2 at lactate threshold (LT) to establish a 95% threshold for meaningful change.

There were no significant differences between tests in the parameters reported. Specifically, we found overall low CoV in peak V˙O2 (4.9%), V˙O2@LT (10.4%), peak O2 pulse (4.6%), peak minute ventilation (V˙E; 7.4%), V˙E/V˙CO2@LT (4.0%), and V˙E/V˙O2@LT (4.8%). The CoV for peak respiratory exchange ratio@LT was significantly affected by diurnal factors; age, sex, and fitness level did not affect variability. The 95% threshold for meaningful change was 0.540 L·min in peak V˙O2 and 0.520 L·min in V˙O2@LT.

Repeatability of CPET parameters is generally higher than previously reported. There were no significant differences in variability related to sex, age, and fitness level; diurnal factors had a limited effect. The threshold for meaningful change in peak V˙O2 and for V˙O2@LT should be considered when gauging a response to therapies or training.