Previous studies focusing on the changes of heart rate, systolic blood pressure and dyspnea caused by the six-minute (6MWT) and shuttle walking distance tests (ISWT) have produced conflicting data. The present study aims at comparing the cardiovascular and dyspnea responses to 6MWT and ISWT in patients with chronic obstructive pulmonary disease (COPD). Twenty patients with clinically stable COPD (age, 56 +/- 9 yrs; BMI, 27.8 +/- 7.7 kg.m(-2); FEV1%pred, 42 +/- 19%; mean +/- Sx) performed three 6MWTs and two ISWTs using standardised protocols. The distances walked in the third 6MWT and second ISWT were 458 +/- 105 and 365 +/- 116 m, respectively. There was a significant correlation between the distances covered in the two tests (r = 0.87; p < 0.001). The 6MWT and ISWT showed similar correlation coefficients with the Baseline Dyspnea Index (r = 0.86; p < 0.001 and r = 0.76; p < 0.001), the Clinical Symptom Scale (r= -0.72; p < 0.001 and r= -0.55; p = 0.011), FEV1 L (r = 0.36; NS and r = 0.30; NS), PImax (r = 0.59; p < 0.008 and r = 0.60; p = 0.001) and the mean pulmonary artery pressure, Doppler echocardiography (r= -0.51; p < 0.029 and r = -0.51; p = 0.032). Although the response to ISWT tended to be greater, we found no statistically significant differences between the two tests in the changes of heart rate (HR), systolic blood pressure (SBP) and dyspnea (Borg) (deltaHR, 17.9 +/- 13.4 vs 23.8 +/- 15.4; deltaSBP, 7.7 +/- 14.6 vs 13.0 +/- 17.0 and deltaBorg, 1.7 +/- 1.1 vs 2.2 +/- 0.9; NS).
Conclusion: The cardiovascular and dyspnea response caused by ISWT is greater (but statistically not significant) than that generated by 6MWT. The more limited the functional capacity of COPD patients the more similar the response generated by 6MWT and ISWT.