Overview
This lecture discusses a project assessing functional capacity in preoperative colorectal patients over 70, comparing the shuttle walk test to CPET for risk stratification and potential pathway optimization.
Functional Capacity Assessment in Preoperative Patients
- Functional capacity assessment evaluates a patient's ability to withstand surgery and predicts postoperative risks.
- Better functional capacity correlates with lower complication rates, shorter hospital stays, and reduced perioperative mortality.
- Risk stratification using functional capacity enables shared decision-making and perioperative planning.
Assessment Methods: Subjective vs Objective
- Functional capacity can be measured subjectively (patient-reported) or objectively (performance-based tests).
- CPET (cardiopulmonary exercise testing) is the gold standard but is costly, time-consuming, and requires specialized staff.
- The shuttle walk test is an objective, simple, inexpensive alternative.
Shuttle Walk Test and CPET Explained
- The shuttle walk test involves walking between cones at increasing speed, measuring maximum distance achieved.
- CPET provides multiple thresholds: peak VO2 (<15 ml/kg/min = higher risk), anaerobic threshold (<11 = higher risk), and VE/VCO2 at anaerobic threshold (>40 = higher risk).
- Accumulating sub-threshold CPET variables increases predictive value for identifying high-risk patients.
Evidence Comparing Shuttle Walk Test and CPET
- Less than 250 meters on shuttle walk predicts higher complications and mortality in several surgical populations.
- More than 360 meters predicts normal or acceptable CPET parameters and lower perioperative risk.
- Patients achieving over 360-400 meters may not require further CPET testing.
Project Methods and Results
- Retrospective audit on colorectal patients over 70, assessing those who completed both tests.
- 21 of 111 patients walked >360 m; 19 had acceptable CPET peak VO2 (PPV = 0.91).
- 20 of 21 patients with >360 m also had acceptable anaerobic threshold; similar results for VE/VCO2.
- Concluded >360 m on shuttle walk can screen out patients unlikely to benefit from CPET, reducing unnecessary tests by 19%.
Implementation & Limitations
- New preoperative pathway: colorectal patients over 70 with >360 m on shuttle walk no longer routinely get CPET.
- Poor shuttle walk performance doesn’t always indicate poor CPET, possibly due to musculoskeletal limitations.
- High prevalence of acceptable CPET results in this group supports high positive predictive value.
- Outcome comparison between groups remains a future research goal.
Key Terms & Definitions
- Functional Capacity — The physical ability to perform activities requiring sustained effort.
- CPET (Cardiopulmonary Exercise Testing) — Gold standard objective test measuring physiological response to exercise.
- Shuttle Walk Test — Field test assessing exercise capacity by walking back and forth between cones at increasing speed.
- Peak VO2 — Maximum oxygen uptake, indicator of aerobic fitness.
- Anaerobic Threshold — Exercise intensity at which lactate begins to accumulate, indicating switch to anaerobic metabolism.
- VE/VCO2 — Ventilatory efficiency ratio, reflects gas exchange efficiency during exercise.
- PPV (Positive Predictive Value) — Likelihood that a positive test result correctly identifies the condition.
Action Items / Next Steps
- Review and monitor the impact of the new preoperative pathway on outcomes and cost savings.
- Consider outcomes comparison between pathway groups in future studies.