CHRONIC OBSTRUCTIVE PULMONARY DISEASE Six-minute walking versus shuttle walking: responsiveness to bronchodilation in chronic obstructive pulmonary disease

Background: The responsiveness of the endurance shuttle walk to functional changes following bronchodilation has recently been reported. The current literature suggests that the 6 min walking test (6MWT) is less responsive to bronchodilation than the endurance shuttle walk. Aim: To compare bronchodilator-induced changes in exercise performance with the 6MWT and the endurance shuttle walk. Methods: In a randomised, double-blind, placebo-controlled, crossover trial, 14 patients with chronic obstructive pulmonary disease (forced expiratory volume in 1 s (FEV1) 50 (8)% predicted) completed two 6MWTs and two endurance shuttle walks, each preceded by nebulised placebo or 500 mg ipratropium bromide. Cardiorespiratory parameters were monitored during each walking test with a portable telemetric gas analyser. Quadriceps twitch force was measured by magnetic stimulation of the femoral nerve before and after each walking test. Results: The 6 min walking distance did not change significantly after bronchodilation despite a significant increase in FEV1 of 0.18 (0.09) litres (p,0.001). A similar change in FEV1 (0.18 (0.12) litres, p,0.001) was associated with a significant improvement in the distance walked on the endurance shuttle walk (Ddistance ipratropium bromide – placebo = 144 (219) m, p = 0.03). Quadriceps muscle fatigue was infrequent (,15% of patients) after both walking tests. Conclusion: The endurance shuttle walk is more responsive than the 6MWT for detecting changes in exercise performance following bronchodilation.