Seventeen patients (six men and 11 women, mean age 66 years) with severe chronic obstructive lung disease (mean FEV1 0.8 (SD 0.3)1) performed three different types of exercise test on four occasions within one week. Three daily doses of placebo tablets were given between the third and fourth attempt at each test. The tests were the 12 minute walking test, a fixed rate and height paced step test, and a cycle ergometer test in which the work rate was increased by 10 watts each minute. Performance increased significantly (p less than 0.01) between the first and fourth attempts in each type of test (12 min walking distance 16% (SD 20%); steps climbed 96% (74%); duration of cycling 29% (41%]. There was a trend for the increase in performance between successive attempts to become progressively smaller but this was not significant. No effect of placebo on exercise performance was detected. The greatest intersubject range of performance was seen in the step test (14-126 steps) and the least in the walking test (438-1014 m). Significant correlations (p less than 0.01) were observed between performance in all three types of exercise test, but the correlations found between the results of the various tests of exercise performance and the FEV1 and the FVC were either weak (p less than 0.05) or non-significant. Ventilation (VE) and oxygen consumption (VO2) were subsequently measured and compared in eight patients during all three types of exercise test. Both the VE and the VO2 that were achieved in the step test were significantly greater than in either the cycle or the walking test. No patient was able to reach and sustain steady state values of VE and VO2 in the step test, whereas a steady state for both VE and VO2 was reached and sustained by all eight patients in the walking test. It is suggested that at least three practice attempts at any exercise test should be made before the introduction of either placebo or specific pharmacological treatment and that even then it may be necessary to allow for the effects of further repeated testing in the assessment of the results of treatment.
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