Abstract
PURPOSE: Gas exchange variables derived from cardiopulmonary exercise tests (CPETs) need to be reliable for evaluating interventions and clinical decision making. Whereas peak oxygen uptake (
O2) has shown to be a highly reliable parameter in patients with coronary artery disease (CAD), little is known about the reproducibility of these parameters in patients with CAD. Therefore, the purpose of this study was to confirm the reliability of peak
O2 and to investigate the reliability of submaximal CPET variables in patients with CAD.
METHODS: Eighty-five patients with CAD (57.6 +/- 8.5 years; 79 males) performed 2 CPETs within 10 days before starting a rehabilitation program. Reliability of peak and submaximal exercise variables was assessed by using intraclass correlation coefficients (ICC), coefficients of variation, Pearson correlation coefficients, paired t tests, and Bland-Altman plots.
RESULTS: Maximal and submaximal exercise parameters showed adequate reliability. Overall, there was a good correlation across both testing occasions (r = 0.63-0.95; P < .05 for all). Peak
O2 (ICC, 0.95; 95% CI, 0.92-0.97) demonstrated excellent reliability. Of the submaximal exercise variables, oxygen uptake efficiency slope (OUES) was as reliable as peak
O2 (ICC, 0.97; 95% CI, 0.95-0.98). The ventilation/carbon dioxide production (
E/
CO2) slope showed very good test-retest reliability (ICC, 0.87; 95% CI, 0.80-0.91) and the
O2/work rate slope showed good reliability (ICC, 0.76; 95% CI, 0.64-0.85).
CONCLUSIONS: Both peak
O2 and OUES show excellent test-retest reliability. Accordingly, in the case of no or unreliable peak
O2 data, we suggest using OUES to evaluate cardiorespiratory fitness in patients with CAD.