Assessing fitness for surgery: a comparison of questionnaire, incremental shuttle walk, and cardiopulmonary exercise testing in general surgical patients

Abstract

Morbidity and mortality are higher in patients with poor preoperative cardiorespiratory reserve. This study aimed to ascertain fitness and therefore risk in elective patients, comparing three measures: Duke Activity Status Index (DASI) questionnaire, incremental shuttle walk test (ISWT), and cycle cardiopulmonary exercise testing (CPET). We looked for correlation between the measures and for thresholds on the questionnaire or shuttle test which could identify fit patients and render CPET unnecessary. A prospective cohort trial of 50 patients having intra-abdominal surgery. Each performed DASI, ISWT, and CPET during a single visit to the hospital. There was a significant correlation between measured oxygen consumption and both ISWT and DASI. Receiver operator curve showed both the shuttle walk test and the DASI are sensitive and specific predictors of VO₂peak >15 ml O₂ kg⁻¹ min⁻¹ and anaerobic threshold (AT) >11 ml O₂ kg⁻¹ min⁻¹. Thirty-two patients would be considered lower risk, having achieved both VO₂peak and AT cut-offs. Setting an ISWT threshold of 360 m identified 13 of the lower risk patients [positive predictive value (PPV) 1.0, negative predictive value (NPV) 0.49]. Setting a DASI threshold score of 46 identified nine lower risk patients (PPV 1.0, NPV 0.44). We found a significant correlation between the tests. However, many patients with poor questionnaire scores or shuttle walks had satisfactory CPET results. Hence, the ability of either simple test to determine risk in a heterogeneous surgical population is poor. CPET provides an objective measurement of cardiopulmonary fitness; however, evidence for this information improving patient outcome is limited and requires further research.