Exploring Methods of Adjusting VO2max for Body Size to Estimate Aerobic Capacity in People Presenting for Metabolic and Bariatric Surgery.

Background: In perioperative settings exercise testing can be used to assess a patient's physical fitness, with VO2max used as a marker to indicate fitness and subsequent risk of adverse surgical outcomes. However, the commonly used reporting methods of VO2max may be problematic in populations with excessive FM such as those awaiting MBS for obesity. Hence, alternative ways of expressing VO2max will be explored. Methods: Historical data from individuals presenting for MBS were analyzed. Predicted VO2max values were adjusted relative to the participants measured and "normative" body mass, where each prediction was assigned a classification score. Predicted VO2max adjusted to the participants measured FFM was also considered. Data were compared to individuals that are lean and sedentary as well as those with obesity from a previous study. Results: Data from 20 participants awaiting MBS (43.15 ± 11.82 years, 68.50 ± 8.39 cm, 115.29 ± 16.82 kg and 59.93 ± 8.69 kg FFM) were examined. Predicted VO2max relative: to total mass was 20.15 ± 5.00 mL/kg/min; normative body mass was 30.04 ± 6.58 mL/kg/min; and FFM was 38.55 ± 9.08 mL/kg FFM/min. Median fitness classifications increased from very poor to poor when predicted VO2max was expressed relative to normative body mass. Conclusions: Reporting predicted VO2max results relative to body mass may be underestimating fitness and overestimating surgical risk in people who are very obese.