New Equations for Predicting Maximum Oxygen Uptake in Patients With Heart Failure.

We obtained directly measured maximal oxygen uptake (VO2 max) by open-circuit spirometry in 1,453 patients with chronic heart failure (HF) who completed a treadmill test (n = 1,453) or cycle ergometry (n = 1,838), as participants in The Fitness Registry and the Importance of Exercise National Data Base (FRIEND) dataset. We developed a new equation to predict measured VO2 max in those using a treadmill by randomly sampling 70% of the participants from each of the following age categories: <40, 40 to 50, 50 to 70, and >70 and used the remaining 30% for validation. Multivariable linear regression analysis was applied to identify the most relevant variables and construct the best prediction model for VO2 max. Treadmill speed and treadmill speed * grade were considered in the final model as predictors of measured VO2 max and the following equation was generated: VO2 max in ml O2 kg/min = speed (m/min) * (0.17 + fractional grade * 0.32) +3.5. To assess the efficacy of the equation, we applied it to 1,612 patients in the HF-ACTION cohort. To assess the efficacy of the FRIEND cycle ergometry equation developed for healthy individuals we applied it to 1,838 HF patients in the FRIEND cohort and 306 patients in a Greek population of HF patients with directly measured VO2 max. The FRIEND equations were superior to ACSM equations in predicting VO2 max regardless of the cohort or exercise mode used (treadmill or cycle ergometry) to access VO2 max.