Oxygen consumption, shuttle walking test and the evaluation of lung resection

Background: Assessment of peak oxygen uptake (VO₂) is recommended in the evaluation of patients with borderline pulmonary function as VO₂ is the strongest independent predictor of postoperative pulmonary complications. However, the measurement of VO₂ requires expensive equipment not available in many medical facilities. The shuttle walking test (SWT) has been proposed to be used as a screening tool prior to performing a cardiopulmonary exercise test. Although an association exists between SWT distance and VO₂, only one small study directly measured VO ₂ during the SWT. Objectives: The aim of this study was to further validate the VO₂-SWT association by directly measuring VO₂ during SWT in a larger cohort of patients with stable chronic obstructive pulmonary disease (COPD). Methods: Fifty stable COPD patients with mild/severe disease were studied. Each patient performed an SWT while wearing a validated portable metabolic monitor. Results: Mean VO₂ (ml/kg/min) measured after each finalized minute of the SWT was (95% confidence interval): 6 (5-7), 9 (8-10), 11 (10-12), 13 (11-14), 15 (14-16), 18 (16-20) and 21 (18-26) for minutes 1-7, respectively. Patients that completed the British Thoracic Society-recommended 25 shuttles (5 min or 250 m) in the SWT had a mean VO ₂ of 15 (14-16). The positive predictive value for walking 25 shuttles (predicting a VO₂ of ≥15ml/kg/min) was 90% and the negative predictive value was 90%. Conclusions: Our findings validate the association between VO₂ and SWT distance and facilitate the interpretation of the test in general practice, particularly when deciding the candidacy of a patient for surgical resection.