Comparison of six-minute walk test distance vs. estimated maximum oxygen consumption for predicting postoperative pulmonary complications in patients undergoing upper abdominal surgery: a prospective cohort study

Abstract

Objective Estimated maximum oxygen consumption (eVO2max) is superior to six-minute walk distance (6MWD) in predicting functional capacity. The hypothesis that eVO2max is a better predictor of postoperative pulmonary complications (PPCs) than 6MWD in patients undergoing major upper abdominal surgery is evaluated. Method Patients scheduled for elective major upper abdominal surgery from July 2018 to May 2021 were included. The six-minute walk test was carried out on all patients before surgery. eVO2max was calculated using the Burr equation incorporated with 6MWD, age, gender, weight, and resting heart rate. The patients were divided into the PPC and the non-PPC group according to the occurrence of clinically significant PPCs. The sensitivity, specificity, and optimum cutoff point of 6MWD and eVO2 max were analyzed in the prediction of PPCs. The area under the receiver operating characteristic curve (AUC) of 6MWD vs. eVO2max was compared by Z test. Results A total of 308 patients were included in this study; 71/308 developed clinically significant PPCs. Compared to the non-PPCs group, the value of 6MWD (P < 0.001) and eVO2max (P < 0.001) were significantly lower in the PPC group. The optimum cutoff point for 6MWD in predicting PPCs was 372. 5m with a sensitivity of 63.4% and specificity of 79.3%. The optimum cutoff point for eVO2max was 8.8 MET with a sensitivity of 91.6% and specificity of 79.3%. A significantly increased AUC was observed in eVO2max compared to 6MWD (P < 0.001, Z = 4.713). Conclusion eVO2max has a better validity than 6MWD for predicting PPCs in patients undergoing major upper abdominal surgery. The results suggested that eVO2max has the potential to be a valid tool to screen patients with a high risk of PPCs.