Predicting peak oxygen consumption during a conservative ramping protocol implications for the heart failure population

PURPOSE: A significant discrepancy between measured oxygen consumption (VO₂) (via ventilatory expired gas analysis) and estimated VO₂ (via the imposed workload) frequently is reported in the heart failure (HF) population during symptom-limited exercise testing. The purpose of this investigation was to examine the difference between measured and estimated VO₂ (VO₂ discrepancy) during a highly conservative ramping protocol. METHODS: For this study, 28 subjects with compensated HF (20 men and 8 women; age, 51.1 ± 14.6 years) and 19 healthy control subjects (age-, gender-, and activity-matched to an HF subgroup) underwent symptom-limited exercise testing (treadmill) with ventilatory expired gas analysis. RESULTS: Peak estimated and measured VO₂ values were significantly higher in the age-, gender-, and activity-matched control group than in the HF group, but the change in measured VO₂ per change in estimated VO₂ (Δmeasured/Δestimated VO₂ slope) and the VO₂ discrepancy did not reach statistical significance. Peak estimated VO₂ was a significant predictor of peak measured VO₂ in the overall HF group (R² = 0.90; P < .001). CONCLUSIONS: Although estimated VO₂ is not considered a replacement for measured VO₂, these results indicate that a highly conservative exercise protocol may allow for a more accurate prediction of peak measured VO₂ via the estimated oxygen cost for a given workload in patients with compensated HF.