The ESWT was performed on a 10 m long course at a
speed corresponding with 85% of VO2 peak, which was
estimated from an earlier performed incremental shuttle
walking test [20]. For both tests a practice walk was
done during the run-in period of the study. Patients
were instructed to walk as long as possible at the speed
that was dictated by the auditory signal. The test was
ended when a patient was more than 0.5 m away from
the marker before the signal was given on two successive
shuttles, or when he or she indicated to be exhausted.
The 6MWD was assessed indoors on a 40 m long
course. Patients used their usual walking aids and, if
applicable, their usual ambulatory oxygen therapy during
the test. The test assistant gave standardized encouragements
every 30 seconds and told the patient after 2 and
after 4 minutes that he/she was 2 and 4 minutes on his/
her way [21]. All patients performed a practice test first,
the results of which were discarded.
During the walking tests supplemental oxygen was
permitted, but conditions were the same at all tests. The
walking tests were not stopped because of desaturation.
Quality of life was assessed with the interviewed version
of the Chronic Respiratory Questionnaire [22]. The
CRQ is a widely used disease specific questionnaire
which has shown to be reliable and valid in COPD patients
[23].