Significance of changes in endurance shuttle walking performance.

BACKGROUND: The endurance shuttle walking test (ESWT) has shown good responsiveness to interventions in patients with chronic obstructive pulmonary disease (COPD). However, the minimal important difference (MID) for this test remains unknown, therefore limiting its interpretability. METHODS: Patients with COPD who completed two or more ESWTs following pulmonary rehabilitation (n=132; forced expiratory volume in 1 s (FEV1) 48 ± 22%) or bronchodilation (n=69; FEV1 50 ± 12%) rated their performance of the day in comparison with their previous performance on a 7-point scale ranging from -3 (large deterioration) to +3 (large improvement). The relationship between subjective perception of changes and objective changes in performance during the shuttle walk was evaluated. RESULTS: Following pulmonary rehabilitation, the anchor-based approach did not allow a valid estimation of the MID in the ESWT performance to be obtained. After bronchodilation, patient ratings of change correlated significantly with the difference in walking distance (r=0.53, p<0.001) and endurance time (r=0.55, p<0.001). For the pharmacotherapy data, regression analysis indicated that a 65 s (95% CI 45 to 85) change in endurance time and a 95 m (95% CI 60 to 115) change in walking distance were associated with a 1-point change in the rating of change scale. These changes represented 13-15% of the baseline values. CONCLUSIONS: A change in endurance shuttle walking performance of 45-85 s (or 60-115 m) after bronchodilation is likely to be perceived by patients. This MID value may be specific to the intervention from which it was derived.

Comparison of the peak exercise response measured by the ramp and 1-min step cycle exercise protocols in patients with exertional dyspnea.

STUDY OBJECTIVES: To compare the peak exercise response and determine the limits of agreement between the ramp and the 1-min step cycle protocols in a representative population of patients with exertional breathlessness attending a respiratory outpatient clinic. DESIGN: Crossover with the test order double blinded and randomized. SETTING: Outpatient exercise physiology laboratory. PATIENTS: Twenty-two patients (12 men; mean [SD] age, 59 [8] years; FEV(1), 71% [21%]) with lung disease and/or exertional breathlessness. INTERVENTION: Symptom-limited, maximum cycle exercise tests using a ramp and a 1-min step work rate (WR) protocols. The two protocols were assigned to subjects in a randomized manner. MEASUREMENTS AND RESULTS: Oxygen uptake (O(2)), minute ventilation (E), heart rate (HR), WR, exercise time, and Borg scores were compared at symptom-limited peak exercise. The mean (SD) peak values for the ramp and the step protocols, respectively, were as follows: peak O(2), 1.51 (0.44) L/min and 1.49 (0.43) L/min; peak E, 50.8 (12.9) L/min and 49.9 (14.5) L/min; and peak HR, 133 (24) beats/min and 131 (22) beats/min (p > 0.05). There were no significant differences between breathlessness and perceived exertion at peak exercise. Peak WR (WRpeak) and exercise time were significantly higher using the ramp protocol: 110.5 (37.1) W vs 105.6 (35.6) W, and 8.2 (2.0) min vs. 7.6 (1.9) min, respectively. CONCLUSIONS: The ramp protocol leads to a higher WRpeak, and this may have implications for exercise prescription. However, there were no significant differences between the two protocols for the peak physiologic responses. The choice of protocol for the measurement of maximal exercise capacity remains one of laboratory preference.