Multicentre study of the determination of peak oxygen uptake and ventilatory threshold during bicycle exercise in chronic heart failure: Comparison of graphical methods, interobserver variability and influence of the exercise protocol

Assessment of the ventilatory threshold (VT) has been proposedto assess exercise tolerance more objectively, particularlyin clinical trials, but reproducibility, interobserver variabilityand feasibility of the graphical methods for determination ofVT have not been properly studied in patients with chronic heartfailure (CHF). Fifty-one patients with mild to moderate CHF(mean peak oxygen uptake (VO₂): 20·5 ml. min^–1. kg^–1) were assessed during two consecutive bicycle exercisetests within 8 days. Two graded exercise protocols were comparedwith stages of 30 Wevery 3min (22 patients) or 10 W$$$ min (29patients). VT was determined separately by five trained physiciansusing five different graphical methods. The ‘crossing method’ (first crossing of the VCO₂and VO² curves) yielded the highest rate of determination (88%)but tended to overestimate the mean VT. The VE method (disproportionateincrease of ventilation relative to VO₂) produced the best interobserveragreement (coefficient of variation=78%). Peak VO₂ was very highly reproducible in both exercise protocols(relative difference test 2-test l/test 1=–0.32% for the30 W3 min protocol;+2·18% for the 10 W. min^–1 protocol).The reproducibility of VT was slightly lower regardless of thegraphical method used to determine it (relative cflfferencesvaried from –3·3% to+7·3%). Therefore, peakVO₂ appears more suitable than VT for assessment of exercisetolerance in CHF.