Assessing the accuracy of algorithm-derived cardiorespiratory fitness in surgical patients: a prospective cohort study.

Purpose: To determine if a non-exercise algorithm-derived assessment of cardiorespiratory fitness (CRF _A ) accurately predicted estimated values obtained using a six-minute walk test (CRF _6MWD ) and the Duke Activity Status Index (CRF _DASI ).
Methods: Following research ethics board approval, an observational cohort study was conducted in selected, consenting patients undergoing elective surgery. Participants completed questionnaires assessing their self-reported exercise capacity. Their height, weight, waist circumference, and vital signs were measured. A six-minute walk test was performed twice with a 45-min rest interval between tests. The correlation between CRF _A and both CRF _6MWD and CRF _DASI was determined.
Results: Two hundred forty-two participants were included. Mean age was 62 (range 45-88 yr); 150 (62%) were male, 87 (36%) self-reported walking or jogging > 16 km per week, and 49 (20%) were current smokers. The CRF _A and CRF _6MWD were highly correlated (Pearson r = 0.878; P < 0.001). CRF _A and CRF _DASI were less strongly correlated (Pearson r = 0.252; P < 0.001). Among patients capable of walking > 427 m in the six-minute walk test, CRF _A , CRF _6MWD , and CRF _DASI were equivalent.
Conclusion: A non-exercise algorithm can estimate cardiorespiratory fitness in patients presenting for elective surgery. The variables required to compute CRF _A can be obtained in a clinic setting without the need to engage in formal exercise testing. Further evaluation of CRF _A as a predictor of long-term outcome in patients is warranted.