Reduced Confounding by Impaired Ventilatory Function With Oxygen Uptake Efficiency Slope and VE/VCO2 Slope Rather Than Peak Oxygen Consumption to Assess Exercise Physiology in Suspected Heart Failure

Heart failure and ventilatory disease often coexist; both create abnormalities in cardiopulmonary exercise test measurements. The authors evaluated the relative dependency of a well-recognized index of heart failure, peak oxygen consumption (VO2), and 2 newer indices, the minute ventilation (VE)/carbon dioxide production (VCO2) slope and oxygen uptake efficiency slope (OUES), on standard markers of impaired cardiac and ventilatory function. One hundred twenty-four patients (median age, 65.8; range, 22.6-84.9), with functional limitation from clinical heart failure were exercised. Peak VO2 was 17.14±7.58 mL/kg/min, VE/VCO2 slope 50.1±20.1, OUES 1.46±0.68 L/min, and forced expiratory volume in 1 second (FEV1) 1.88±0.75 L. Peak VO2 is substantially more sensitive to FEV1 than ejection fraction (4.0 mL/kg/min difference between above- and below-median FEV1 and 1.5 mL/kg/min between above- and below-median ejection fraction). OUES does not share this peculiar excess sensitivity to FEV1 (0.12 L/min difference between above- and below-median FEV1 and 0.01 L/min between above- and below-median ejection fraction). VE/VCO2 slope has a borderline effect by FEV1 (7.07 difference between above- and below-median FEV1 and 2.07 between above- and below-median ejection fraction). Although widely used as a marker of heart failure severity, peak VO2 is very sensitive to spirometry status and is indeed more affected by FEV1 than by ejection fraction. OUES in contrast does not show this preferential sensitivity to impaired FEV1. Congest Heart Fail. © 2010 Wiley Periodicals, Inc.