A novel cardiopulmonary exercise test protocol and criterion to determine maximal oxygen uptake in chronic heart failure

Abstract

Cardiopulmonary exercise testing for peak oxygen uptake (V̇o2peak) can evaluate prognosis in chronic heart failure (CHF) patients, with the peak respiratory exchange ratio (RERpeak) commonly used to confirm maximal effort and maximal oxygen uptake (V̇o2max). We determined the precision of RERpeak in confirming V̇o2max, and whether a novel ramp-incremental (RI) step-exercise (SE) (RISE) test could better determine V̇o2max in CHF. Male CHF patients ( n = 24; NYHA class I–III) performed a symptom-limited RISE-95 cycle ergometer test in the format: RI (4–18 W/min; ∼10 min); 5 min recovery (10 W); SE (95% peak RI work rate). Patients ( n = 18) then performed RISE-95 tests using slow (3–8 W/min; ∼15 min) and fast (10–30 W/min; ∼6 min) ramp rates. Pulmonary gas exchange was measured breath-by-breath. V̇o2peak was compared within patients by unpaired t-test of the highest 12 breaths during RI and SE phases to confirm V̇o2max and its 95% confidence limits (CI95). RERpeak was significantly influenced by ramp rate (fast, medium, slow: 1.21 ± 0.1 vs. 1.15 ± 0.1 vs. 1.09 ± 0.1; P = 0.001), unlike V̇o2peak (mean n = 18; 14.4 ± 2.6 ml·kg−1·min−1; P = 0.476). Group V̇o2peak was similar between RI and SE ( n = 24; 14.5 ± 3.0 vs. 14.7 ± 3.1 ml·kg−1·min−1; P = 0.407); however, within-subject comparisons confirmed V̇o2max in only 14 of 24 patients (CI95 for V̇o2max estimation averaged 1.4 ± 0.8 ml·kg−1·min−1). The RERpeak in CHF was significantly influenced by ramp rate, suggesting its use to determine maximal effort and V̇o2max be abandoned. In contrast, the RISE-95 test had high precision for V̇o2max confirmation with patient-specific CI95 (without secondary criteria), and showed that V̇o2max is commonly underestimated in CHF. The RISE-95 test was well tolerated by CHF patients, supporting its use for V̇o2max confirmation.