Exploring Methods of Adjusting VO ₂ max 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 VO 2 max used as a marker to indicate fitness and subsequent risk of adverse surgical outcomes. However, the commonly used reporting methods of VO 2 max may be problematic in populations with excessive FM such as those awaiting MBS for obesity. Hence, alternative ways of expressing VO 2 max will be explored. Methods Historical data from individuals presenting for MBS were analyzed. Predicted VO 2 max values were adjusted relative to the participants measured and “normative” body mass, where each prediction was assigned a classification score. Predicted VO 2 max 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 VO 2 max 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 VO 2 max was expressed relative to normative body mass. Conclusions Reporting predicted VO 2 max results relative to body mass may be underestimating fitness and overestimating surgical risk in people who are very obese.