Resting Oxygen Consumption and Heart Failure: Importance of Measurement for Determination of Cardiac Output With the Use of the Fick Principle.

Background: Resting oxygen consumption (VO) is often estimated and frequently used to guide therapeutic decisions in symptomatic heart failure (HF) patients. The relationship between resting VO and symptomatic HF and the accuracy of estimations of VO in this population are unknown.

Methods And Results: We performed a cross-sectional study of HF patients (n = 691) and healthy control subjects (n = 77). VO was measured with the use of a metabolic cart, and estimated VO was calculated with the use of the Dehmer, LaFarge, and Bergstra formulas and the thermodilution method. The measured and estimated VO were compared and the potential impact of estimations determined. In the multivariable model, resting VO decreased with increasing New York Heart Association (NYHA) functional class in a stepwise fashion (β NYHA functional class IV vs control = -36 mL O/min; P < .001). Estimations of VO with the use of derived equations diverged from measured values, particularly for patients with NYHA functional class IV limitations. The percentage difference of measured VO versus estimated VO was >25% in 39% (n = 271), 25% (n = 170), 82% (n = 566), and 39% (n = 271) of HF patients when using the Dehmer, LaFarge, Bergstra, and thermodilution-derived estimations of VO respectively.

Conclusions: Resting VO decreases with increasing NYHA functional class and is lower than in control subjects. Using estimations of VO to calculate CO may introduce clinically important error.