Quantifying assumptions underlying peak oxygen consumption equations across the body mass spectrum

Area of Science:

• Exercise Physiology
• Cardiopulmonary Exercise Testing
• Predictive Equation Validation

Background:

• Accurate prediction of peak oxygen consumption (pVO2) is crucial for assessing cardiorespiratory fitness.
• Existing predictive equations, such as Wasserman-Hansen (WH) and FRIEND, may have differential accuracy across body mass index (BMI) spectrums.
• Understanding these differences is vital for appropriate clinical interpretation of cardiopulmonary exercise test (CPET) results, especially in individuals with obesity.

Purpose of the Study:

• To quantify the assumptions of the Wasserman-Hansen (WH) and FRIEND predictive peak oxygen consumption (pVO2) equations concerning body mass index (BMI).
• To evaluate the performance of these equations in predicting pVO2 across various BMI categories using simulation and clinical data.
• To compare the differences in pVO2 estimations between the WH and FRIEND equations, particularly in individuals with obesity.

Main Methods:

• Assumptions of WH and FRIEND pVO2 equations were determined via simulation and validated using the Stanford Exercise Testing registry.
• Percent-predicted VO2 (ppVO2) values were calculated and compared using Bland-Altman analysis.
• Age-adjusted VO2 ratios (pVO2/pre-exercise VO2) and ppVO2 slopes were analyzed across BMI categories to quantify fitness differences.

Main Results:

• Simulation indicated the FRIEND equation predicted lower fitness in adults with obesity compared to WH equations.
• Bland-Altman analysis of 2471 patients showed an average relative difference of -1.7% between WH and FRIEND ppVO2, with larger discrepancies in individuals with BMI >30 kg/m².
• Analysis confirmed lower fitness in individuals with obesity, a trend more pronounced with the FRIEND equation, indicating significant differences in pVO2 estimations.

Conclusions:

• Peak VO2 estimations from WH and FRIEND equations differ significantly, especially in individuals with obesity.
• The FRIEND equation attributes a greater reduction in pVO2 to obesity compared to the WH equations.
• These findings highlight the importance of considering BMI when interpreting ppVO2 values from CPETs and may refine clinical assessments.