Reproducibility of a 6-minute cycle ergometer test protocol in patients with COPD.

Patients with Chronic Obstructive Pulmonary Disease (COPD) have a reduced
exercise tolerance. Therefore, improvement of exercise capacity is considered
to be a key dimension of response in lung rehabilitation interventions and
exercise tolerance and has become an important outcome measure for lung
rehabilitation evaluation. As exercise intolerance cannot be predicted at rest,
cardiopulmonary exercise tests (CPET) are used to evaluate exercise intolerance
in patients with COPD. CPET is based on the principle that system failure
typically occurs while the system is under stress. These tests can provide an
objective measure of exercise capacity in patients with COPD as they can;
identify the mechanisms limiting exercise tolerance; establish indices of the
patient*s prognosis; and monitor disease progression and/ or the response to
specific interventions by evaluating the changes in exercise variables before
and after rehabilitation. Submaximal exercise tests such as the constant load
exercise test (CLET) protocols are used to evaluate changes in exercise
variables after interventions in a everyday life work rate domain. In these
CLET protocols on a cycle ergometer work rate is constant (usually 75 - 85% of
peak work rate measured at an symptom limited incremental exercise test), and
patients are asked to exercise as long as they can. Time to limitation (TLIM)
is measured and used to evaluate intervention effects on exercise tolerance.
These CLET protocols are called open- ended test protocols. In open- ended test
protocols there is no clearly defined ending point of the test as the total
work performed in this test depends on the exercise capacity of the patient. In
contrast, in closed-ended test protocols an ending point of the test is clearly
defined as the total work performed or total time is determined in advance. In
time trial tests, the exercise capacity of the patient determines the time that
is needed to complete the total work. The reproducibility of closed- ended time
trial performance tests is much higher than open- ended performance test
protocols in healthy subjects. Reproducibility of a closed- end 6 minute cycle
protocol in patients with COPD has never been evaluated. The 6-minute walk
(6-MWT) test is a closed-end (time is determined in advance) self paced
standardized field test to evaluate exercise tolerance in patients with COPD.
Because most activities of daily living are performed at submaximal levels of
exertion, the 6-MWT more likely reflects the functional exercise level for
daily physical activities. However, to our knowledge, there is no such closed
end cycling equivalent exercise test for evaluation of performance in patients
with COPD. Given the ubiquity of cycling activities in many countries (and
especially the Netherlands,) and the fact that cycling is an often-used
training modality in pulmonary rehabilitation, there is a need for a validated
closed-ended cycling performance test. We expect closed- ended test protocols
(time trials) to be more suitable than open-ended tests to assess performance
capacity in patients with COPD in a clinical setting. These tests are presumed
to be less sensitive to the effect of motivation and other psychological
factors on exercise performance, as the end-point of the test protocol is
determined in advance. This is an important issue in COPD patients since they
often experience breathing discomfort during exercise.

The objective of this study is to evaluate the reproducibility (CV) of a
6-minute cycle exercise performance test in patients with COPD.

Patients will perform the same 6-minute cycle test protocol five times in a
two-week period. Between each test there is a 48 to 72 hour period. All tests
will be performed at the same the time of the day. Patients will be instructed
not to eat in the two hours preceding the test, and to avoid strenuous physical
work 24 hours prior to the tests. Within 30 minutes before the test, patients
are told to use their regular medication. An electromagnetically braked
ergometer (Lode Excalibur Sport, Lode, Groningen) is used to perform the tests.
The cycle ergometer was set in a linear mode; work rates increased with
increased pedalling rate. After a short warm-up period (3 min, 20%Wmax)
patients will be asked to perform a maximal amount of work in 6-minutes. There
is a 6-minute countdown visualised on a monitor during the test. During these
tests, patients received no information about time and pedalling rate (rpm).
Total work in 6 minutes to complete is the main measure of performance. The
test will be aborted when pedalling rates drop below 40 rpm or when oxygen
saturation (SpO2) falls below 85%. Patients are free to stop the test at any
time without consequences. A modified Borg Dyspnea Scale is used to assess
perceived exertion in the legs and dyspnoea before and after completion of the
6-minute cycle test.

Not applicable.

The risk and burden in this study is deemed minimal in comparison with the
regular exercise testing and exercise training in pulmonary rehabilitation
programmes. Patients with comorbidities that limit their exercise tolerance
will not be included in the study. Closed-end tests as the 6 - minute walk test
(6MWT) are widely used to examin exercise tolerance of patients with COPD. The
6MWT has proven to be safe and the use of these tests to evaluate aerobic
capacity is widely accepted. However, there is no 6- minutes cycle equivalent.
The use of such a equivalent cycle test provides no additional risks as the
burden to the patient is simular to the 6MWT. In this study, patient can always
contact the main investigator or independent medical doctor at any time during
the course of the study should they have questions or comments regarding
protocol adherence tor any other questions related to the study. Patients in
this study will receive an invitation letter with a written explanation of the
aims and procedures of the study and a verbal explanation; Attached to the
invitation letter, an explanation about the insurance will be provided.
Patients can contact investigator Willem Gosens (PhD) and the independent
medical doctor, during and after the study. The research data will be analyzed,
described and kept by Mr. Willem Gosens, (PhD). Patient can end their
participation at any time without explanation.