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 (VO₂) is often estimated and frequently used to guide therapeutic decisions in symptomatic heart failure (HF) patients. The relationship between resting VO₂ and symptomatic HF and the accuracy of estimations of VO₂ 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). VO₂ was measured with the use of a metabolic cart, and estimated VO₂ was calculated with the use of the Dehmer, LaFarge, and Bergstra formulas and the thermodilution method. The measured and estimated VO₂ were compared and the potential impact of estimations determined. In the multivariable model, resting VO₂ decreased with increasing New York Heart Association (NYHA) functional class in a stepwise fashion (β NYHA functional class IV vs control = -36 mL O₂/min; P < .001). Estimations of VO₂ with the use of derived equations diverged from measured values, particularly for patients with NYHA functional class IV limitations. The percentage difference of measured VO₂ versus estimated VO₂ 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 VO₂ respectively.

Conclusions: Resting VO₂ decreases with increasing NYHA functional class and is lower than in control subjects. Using estimations of VO₂ to calculate CO may introduce clinically important error.