Paced-walk and step tests to assess exertional dyspnea in COPD

This study reports on the development and test-retest reproducibility of a modified shuttle walking and step testing protocols to assess exertional dyspnea in patients with COPD. Patients with COPD randomly performed four externally paced 3-min bouts of shuttle walking at 1.5, 2.5, 4.0 and 6.0 km x h(- 1) or stepping at constant rate of 18, 22, 26 and 32 steps x min(- 1). Walking and stepping procedures were repeated once, on a separate occasion. Ventilation, heart rate, gas exchange parameters and dyspnea Borg scores were obtained at the end of each exercise bout. Most patients completed walking or stepping at the slow and middle speed cadences but only 33% completed walking at 6.0 km x h(- 1) and 40% completed stepping at 32 steps x min(- 1). Walking and stepping at progressively faster pace caused a progressive increase in ventilation and dyspnea. Test-retest Pearson correlation coefficients for ventilation, heart rate, gas exchange parameters and dyspnea scores over the four exercise bouts, all exceeded 0.80. Intra-class correlation coefficients were at least as strong as Pearson coefficients. Bland & Altman representation showed that for repeated Borg scores, 92 and 96% of points lied within 2 SD of the mean difference between test-retest values for walking and stepping. The majority of moderate and severe COPD patients completed the 3-min shuttle waking testing at 1.5 to 4.0 km x h(- 1) and the 3-min of step testing at rates between 18 and 26 steps x min(- 1). Both field tests were highly reproducible in patients with COPD.