Test-retest Reproducibility of Constant Rate Step and Shuttle Walk Test for the Assessment of Exertional Dyspnea in patients with COPD

Background: Alternatives for laboratory exercise testing are needed to better reflect symptoms of physical activities of daily living in chronic disease. Such a tool should accurately set the exercise intensity and show good reproducibility. This study examined the reproducibility of constant rate walking (CRWT) and stepping tests (CRST) to assess exertional dyspnea in patients with COPD. Methods: Stable COPD patients (n=43; 65 ± 6.5 yr; FEV1= 49 ± 16% pred.) equipped with a portable Jaeger Oxycon Mobile® metabolic system completed both the CRWT and the CRST. Each test included four 3-min constsant rate stages separated by a 10-min rest period on two occasions separated by 7 to 14 days. For both exercise modalities the selected rates targeted intensities between 25 and 80% VO2 peak for moderately-severe COPD patients. Ventilation (VE) and gas exchange were obtained during the third minute and the Borg dyspnea score at the end of each exercise bout. Results: An equal proportion of patients (35%) completed stage 4 of the CRWT and of the CRST. The test-retest correlation coefficients for dyspnea scores ranged from 0.79 to 0.95 for stages 1 through 4 for theCRWTand from 0.88 to 0.85 for the CRST while those for VE (L·min-1) ranged from 0.95 to 0.98 and 0.91 to 0.95 respectively. Conclusion: These results show both the CRWT and the CRST to be highly reproducible for the assessment of exertional dyspnea in patients with moderate-severe COPD. However, a better linearity in VE and VO2 with exercise stages was seen for the CRST than for the CRWT since patients complied more easily to the imposed external load with stepping than with walking.