Comparing peak and submaximal cardiorespiratory responses during field walking tests with incremental cycle ergometry in COPD


Hill, K.; Dolmage, T.E.; Woon, L.; Coutts, D.; Goldstein, R.; Brooks, D.

Respirology 17(2): 278-284

2012


Official
journal
of
the
Asian
Pacific
Society
of
Respirelogy
Respirology
ORIGINAL
ARTICLE
Comparing
peak
and
submaximal
cardiorespiratory
responses
during
field
walking
tests
with
incremental
cycle
ergometry
in
COPD
KYLIE
HILL,"
2,5,6
THOMAS
E.
DOLMAGE,
3
LYNDA
WOON,'
DEBBIE
COUTTS,
4
ROGER
GOLDSTEINL
2
AND
DINA
BROOKS"
'Respiratory
Medicine,
West
Park
Healthcare
Centre,
2
Department
of
Physical
Therapy
and
Medicine,
University
of
Toronto,
3
Respiratory
Evaluation
and
Diagnostic
Services,
West
Park
Healthcare
Centre,
Toronto,
4
Department
of
Respiratory
Medicine,
Credit
Valley
Hospital,
Mississauga,
Ontario,
Canada,
5
School
of
Physiotherapy
and
Curtin
Health
Innovation
Research
Institute,
Curtin
University,
Bentley,
and
6
Lung
Institute
of
Western
Australia
and
Centre
for
Asthma,
Allergy
and
Respiratory
Research,
University
of
Western
Australia,
Crawley,
Western
Australia,
Australia
ABSTRACT
Background
and
objective:
Field
and
laboratory-
based
tests
are
used
to
measure
exercise
capacity
in
people
with
COPD.
A
comparison
of
the
cardiorespira-
tory
responses
to
field
tests,
referenced
to
a
laboratory
test,
is
needed
to
appreciate
the
relative
physiological
demands.
We
sought
to
compare
peak
and
submaximal
cardiorespiratory
responses
to
the
6-min
walk
test,
incremental
shuttle
walk
test
and
endurance
shuttle
walk
test
with
a
ramp
cycle
ergometer
test
(CET)
in
patients
with
COPD.
Methods:
Twenty-four
participants
(FEV,
50
±
14%;
66.5
±
7.7
years;
15
men)
completed
four
sessions,
separated
by
z24
h.
During
an
individual
session,
par-
ticipants
completed
either
two
6-min
walk
tests,
incre-
mental
shuttle
walk
tests,
endurance
shuttle
walk
tests
using
standardized
protocols,
or
a
single
CET,
wearing
a
portable
gas
analysis
unit
(Cosmed
K4b
2
)
which
included
measures
of
heart
rate
and
arterial
oxygen
saturation
(SpO2).
Results:
Between
tests,
no
difference
was
observed
in
the
peak
rate
of
oxygen
uptake
(F
3
,
69
=
1.2;
P=
0.31),
end-test
heart
rate
(F2,
50
=
0.6;
P=
0.58)
or
tidal
volume
(F
3
,
66
=
1.5;
P=
0.21).
Compared
with
all
walking
tests,
the
CET
elicited
a
higher
peak
rate
of
carbon
dioxide
output
(1173
±
350
mL/min;
F
3
,
62
=
4.8;
P=
0.006),
minute
ventilation
(48
±
17
L/min;
F3,69
=
10.2;
P<
0.001)
and
a
higher
end-test
SpO
2
(95
±
4%;
F
3
,
63
=
24.9;
P<
0.001).
Conclusions:
In
patients
with
moderate
COPD,
field
walking
tests
elicited
a
similar
peak
rate
of
oxygen
uptake
and
heart
rate
as
a
CET,
demonstrating
that
Correspondence:
Dina
Brooks,
Department
of
Physical
Therapy,
University
of
Toronto,
160-500
University
Ave,
Toronto,
Ontario,
Canada
M5G
1W.
Email:
Received
2
June
2011;
invited
to
revise
18
July
2011;
revised
4
August
2011;
accepted
29
August
2011
(Associate
Editor:
Shu
Hashimoto).
SUMMARY
AT
A
GLANCE
In
patients
with
moderate
COPD,
the
6MWT,
ISWT
and
ESWT
elicited
a
similar
peak
rate
of
oxygen
uptake
and
heart
rate
response
compared
with
a
ramp
CET,
demonstrating
that
both
self-
and
exter-
nally
paced
field
tests
progress
to
high
intensities.
both
self-
and
externally
paced
walking
tests
progress
to
high
intensities.
Key
words:
chronic
obstructive
pulmonary
disease,
exercise
test,
oxygen
uptake,
repeatability,
6-min
walk
test.
INTRODUCTION
In
people
with
COPD,
impaired
lung'
and
peripheral
muscle
function
compromise
exercise
capacity.
2
Accurate
assessment
of
exercise
capacity
yields
prog-
nostic
information
3
and
has
important
implications
for
an
individual's
clinical
management
such
as
evaluating
the
response
to
an
intervention
and
pre-
scribing
exercise
training
intensities
capable
of
inducing
adaptation."
Laboratory-based
incremen-
tal
cycle
ergometer
tests
(CETs)
are
generally
accepted
as
the
gold
standard
for
quantifying
exercise
capac-
ity.'
Such
tests
are,
however,
costly
and
require
sophis-
ticated
equipment
and
resources
that
are
not
available
in
all
facilities
or
to
all
clinicians.
Therefore,
field
walking
tests
are
often
used."
Such
tests
are
reproducible
after
one
practice
and
respon-
sive
to
exercise
training."
-
M
However,
it
is
unclear
how
the
peak
cardiorespiratory
responses
during
walking
tests
compare
with
a
CET.
That
is,
although
the
incre-
mental
shuttle
walk
test
(ISWT)
consistently
elicits
a
similar
peak
rate
of
oxygen
uptake
(
VO
2
)
and
heart
2011
The
Authors
Respirology
(2012)
17,
278-284
Respirology
2011
Asian
Pacific
Society
of
Respirology
doi:
10.1111/j.1440-1843.2011.02089.x
A
comparison
of
exercise
tests
in
COPD
279
rate
as
a
CET,
15-18
the
6-min
walk
test
(6MWT)
elicits
similar
peak
responses
in
some
16,18,19
but
not
all
studies.
17
'
20-22
No
study
has
compared
response
during
the
endurance
shuttle
walk
test
(ESWT)
1
°
with
the
ISWT,
6MWT
and
CET.
Such
information
is
needed
to
appreciate
the
physiologic
demands
of
each
test,
rela-
tive
to
one
another.
Further,
the
pattern
of
submaxi-
mal cardiorespiratory
responses
is
needed
to
explain
previous
findings
of
higher
dyspnoea
at
time
points
prior
to
test
completion
during
the
6MWT
relative
to
the
ISWT
and
CET.
16
The
primary
aim
of
this
study
was
to
compare
peak
and
submaximal
cardiorespiratory
responses
during
the
6MWT,
ISWT
and
ESWT
with
a
CET
in
people
with
COPD.
A
secondary
objective
was
to
report
the
coef-
ficient
of
repeatability
of
gas
exchange
and
breathing
pattern
variables.
METHODS
Design
This
cross-sectional
study
was
approved
by
the
rel-
evant
Human
Research
Ethics
Committees.
Written
informed
consent
was
obtained
from
every
person
before
participation.
Each
participant
attended
four
2-h
assessment
sessions,
each
separated
by
at
least
24
h.
During
a
session,
participants
completed
either
6MWTs,
ISWTs,
ESWTs
or
a
CET.
To
account
for
poten-
tial
improvements
resulting
from
familiarization,
1
°
,11
each
walldng
test
was
performed
twice,
separated
by
a
20-
to
30-min
rest.
To
eliminate
day-to-day
vari-
ability,
23
the
same
test
protocol
was
performed
twice
on
a
given
day.
The
order
of
sessions
differed
among
participants.
Study
criteria
Participants
were
eligible
for
the
study
if
they
had
a
diagnosis
of
COPD,
24
a
smoking
history
>
10
pack-
years
and
were
clinically
stable
(i.e.
had
not
used
oral
corticosteroids
or
antibiotics
within
the
preceding
2-week
period).
Exclusion
criteria
comprised
evi-
dence
of
a
comorbid
condition
that
might
adversely
affect
exercise
performance,
a
history
of
lung
surgery,
the
use
of
a
rollator
or
long-term
oxygen
therapy
or
evidence
of
marked
desaturation
during
exercise
(i.e.
Sp02
<
80%)
that
would
have
necessitated
premature
cessation
of
the
test.'
Most
participants
were
familiar
with
the
6MWT
prior
to
participating
in
this
study.
Measurements
Exercise
capacity
All
walldng
tests
were
overseen
by
two
experienced
physiotherapists
on
a
quiet,
level,
enclosed,
temperature-controlled
corridor.
Before
and
after
each
walk
test,
and
every
minute
during
the
CET,
mea-
surements
were
obtained
of
dyspnoea
and
leg
fatigue
using
the
modified
Borg
scale
25
During
all
tests,
breath-by-breath
measurements
of
gas
exchange
and
breathing
pattern
were
collected
using
a
calibrated
portable
gas
analysis
system
(K4b
2
,
Cosmed,
Rome,
Italy).
Arterial
oxygen
saturation
(forehead
sensor,
Nellcor
Max
Fast,
Pleasanton,
CA,
USA)
and
heart
rate
(Polar
al
heart
rate
monitor,
Polar
Electro
Oy,
Kempele,
Finland)
were
monitored
continuously.
Walk
tests.
The
ISWTs
and
ESWTs
were
performed
according
to
standardized
protocols,
'°'2°
modified
to
include
one
standardized
warning
to
increase
walldng
speed
the
first
time
each
participant
lagged
behind
the
pace
dictated
by
the
audio
-signal.
16
The
speed
selected
for
the
ESWTs
was
equivalent
to
85%
of
the
peak
VO
2
estimated
using
the
distance
achieved
during
the
best
ISWT.
1
°
This
test
was
preceded
by
a
90-s
warm-up
period
during
which
the
participant
walked
slowly.
The
ESWT
was
terminated
by
the
tester
at
20
min.
1
°
For
patients
who
achieved
20
min
during
their
first
ESWT,
the
second
test
was
conducted
at
a
faster
walldng
pace.
Similarly,
to
reduce
the
likelihood
of
walking
for
20
min
during
the
second
ESWT,'3'26
those
who
walked
for
more
than
10
min
with
minimal
progression
in
heart
rate
or
change
in
arterial
oxygen
saturation
(SpO2)
for
three
consecutive
minutes
during
the
first
test,
also
completed
their
second
test
at
a
faster
pace.
The
6MWTs
were
performed
accord-
ing
to
the
American
Thoracic
Society
guidelines?'
Cycle-ergometry
test.
A
symptom-limited
ramp
CET
was
performed
on
an
electronically
braked
bicycle
ergometer
(Lode
Excalibur
926851V3.00,
Lode,
Groningen,
the
Netherlands).
Peak
exercise
responses
during
CET
are
reproducible
in
people
with
COPD
28,2
°
and
therefore
the
CET
was
performed
once.
Partici-
pants
pedalled
without
a
load
for
3
min
and
thereafter
the
load
increased
by
5,
10
or
15
W/
min
based
on
each
participant's
history
of
daily
physical
activity
and
symptoms,
to
induce
symptom
limitation
within
approximately
10
min.
Anthropometric
and
resting
lung
function
During
the
first
assessment
session,
age,
sex
and
Modi-
fied
Medical
Research
Council
dyspnoea
grade
3
°
were
recorded
and
measurements
were
made
of
height
and
weight.
The
most
recent
measurements
of
resting
lung
function
were
extracted
from
the
medical
notes.
Analyses
Breath-by-breath
data
were
exported
to
Sigmaplot
(version
11.0)
for
analyses.
To
plot
the
submaximal
responses,
for
every
test,
measures
of
V0
2
,
rate
of
carbon
dioxide
output
(VCO
2
),
minute
ventilation
(V,
),
tidal
volume,
heart
rate
and
SO2
p
were
grouped
into
epochs
equivalent
to
10%
increments
of
the
total
test
duration
(i.e.
deciles)
using
a
two-dimensional
data
transformation.
Data
collected
during
the
90-s
warm-up
and
3
min
of
unloaded
pedalling
that
preceded
the
ESWT
and
CET,
respectively,
were
excluded
from
analyses.
Data
collected
across
both
0
2011
The
Authors
Respirology
(2012)
17,
278-284
Respirology
0
2011
Asian
Pacific
Society
of
Respirology
280
6MWTs,
ISWTs
and
ESWTs
were
averaged
for
analysis,
with
the
exception
of
those
participants
who
com-
pleted
the
ESWTs
at
different
speeds.
In
this
instance,
only
data
performed
at
the
faster
walldng
speed
were
used
in
the
analysis.
Before
undertaking
statistical
analysis,
a
natural
logarithmic
transformation
was
applied
to
all
cardio-
respiratory
variables
to
improve
the
extent
to
which
they
approached
a
normal
distribution.
Peak
(end-
test)
responses
were
compared
among
tests
using
one-way
repeated
measures
analysis
of
variance
with
paired
t-tests
for
post-hoc
comparisons
(SPSS
ver-
sion
17.0,
SPSS
Inc.,
Chicago,
IL,
USA).
For
heart
rate,
VCO
2
and
leg
fatigue,
Mauchly's
test
indicated
that
the
assumption
of
sphericity
was
violated,
and
therefore
the
degrees
of
freedom
were
corrected
using
Huynh-Feldt
estimates.
P-values
0.05
were
con-
sidered
significant.
Repeatability
of
variables
collected
on
completion
of
the
walk
tests
was
assessed
using
methods
of
Bland
and
Altman.'
We
calculated
the
bias,
defined
as
the
mean
difference
between
two
6MWTs,
ISWTs
and
ESWTs
as
well
as
the
coefficient
of
repeatability,
defined
as
1.96
times
the
standard
deviation
of
the
difference.
Patients
who
performed
ESWTs
at
differ-
ent
speeds
were
excluded
from
this
analysis.
Sample
size
calculations
A
prospective
sample
size
calculation
was
based
on
detecting
a
10%
difference
in
the
primary
outcome,
peak
V0
2
,
between
any
walldng
test
and
CET.
Using
data
available
in
the
literature
that
reported
a
peak
VO,
during
a
CET
of
1.41
L/min,
19
we
estimated
that
24
participants
would
yield
80%
power
(a
=
0.05)
to
detect
a
difference
of
0.14
L/
min
in
the
peak
VO,
(i.e.
10%
difference
and
the
coefficient
of
repeatability
for
this
measure)
29
with
a
standard
deviation
of
0.24
L/
min
(average
standard
deviation
of
the
two
tests
reported
by
Troosters
et
al.)
19
using
a
paired
t-test.
RESULTS
Of
the
33
individuals
who
consented
to
participate
in
this
study,
five
(15%)
were
unable
to
tolerate
the
mask
for
portable
gas
analysis
equipment,
one
(3%)
was
withdrawn
due
to
hypertension
and
one
(3%)
with-
drew.
Data
from
two
individuals
(6%)
was
ineligible
due
to
equipment
failure.
Characteristics
of
the
24
participants
who
completed
the
study
are
summa-
rized
in
Table
1.
ISWTs
were
performed
before
6MWTs
by
13
(54%)
participants.
Three
(12%)
participants
rested
during
the
6MWT.
The
ESWT
and
ISWT
were
each
performed
only
once
by
one
participant
(4%)
due
to
an
abnor-
mally
high
end-test
heart
rate.
A
higher
walldng
speed
was
selected
for
the
second
ESWT
in
five
(21%)
participants.
Performance
during
each
test
is
summarized
in
Table
2.
Average
speed
during
the
6MWT
was
76.5
m/
min
(95%
confidence
interval
(CI):
71.8-81.1
m/min).
Peak
walking
speed
achieved
during
the
ISWT
was
K
Hill
et
al.
Table
1
Participant
characteristics
(n
=
24;
15
men)
Variable
Mean
±
SD
Range
Age
(years)
66.5
±
7.7
48-83
Height
(m)
1.64
±
0.10
1.42-1.86
Weight
(kg)
71.5
±
14.1
46.7-91.6
BMI
(kg/m
2
)
26.8
±
5.5
19.1-39.7
MRC
dyspnoea
grade
2
±
1
1-
0-2
FEV,
(L)
1.18
±
0.44
0.57-2.51
FEV,
(%
predicted)
50
±
14
20-85
FEV,/FVC
(%)
40
±9
25-69
FRC
(L)
5.19
±
1.48
1.46-8.04
FRC
(%
predicted)
169
±
37
98-213
D
L
CO
(mL/min/mm
Hg)
12.6
±
3.3
6.3-17.9
D
L
CO
(%
predicted)
58
±
18
26-95
t
Data
are
median
±
interquartile
range.
MRC,
modified
Medical
Research
Council
(scores
range
from
0
to
4).
Table
2
Results
of
exercise
tests
Mean
±
SD
Range
6-min
walk
test
Learning
effect
(m)
t
3
±
11
-24
to
24
Distance
(m)*
459
±
66
355-631
End-test
dyspnoea*
3.6
±
1.7
0.5-7.5
End-test
leg
fatigue
*
2.3
±
2.1
0-6
Incremental
shuttle
walk
test
Learning
effect
(m)
t
25
±
35
-20
to
100
Distance
(m)
*
338
±
102
180-540
End-test
dyspnoea*
4.0
±
1.1
1-6
End-test
leg
fatigue
*
2.2
±
2.2
0-6.5
Endurance
shuttle
walk
test
Learning
effect
(s)
6
50
±
83
-90
to
256
Time
(s)
*
313
±
160
123-765
Distance
(m)
*
384
±
193
136-873
End-test
dyspnoea*
4.4
±
1.7
1-8
End-test
leg
fatigue
*
3.0
±
2.4
0-8.5
Cycle
ergometry
test
Peak
power
(W)
72
±
28
27-129
End-test
dyspnoea
6.2
±
2.0
0.5-9
End-test
leg
fatigue
5.7
±
2.7
0.5-10
t
Difference
between
second
and
first
test.
*Average
of
two
tests
(for
ESWT,
only
tests
performed
the
same
walk
speed
were
averaged,
otherwise
the
test
performed
at
the
faster
speed
was
included
in
the
analysis).
§
Includes
data
from
n=
18.
85.9
m/
min
(95%
CI:
80.3-91.5
m/min).
Average
speed
during
the
ESWT
was
73.4
m/min
(95%
CI:
68.3-
78.4
m/
min).
Compared
with
each
walking
test,
the
CET
elicited
greater
peak
dyspnoea
(F
3
,
69
=
27.9;
P
<
0.001)
and
leg
fatigue
(F
3
,
54
=
27.5;
P
<
0.001).
Pat-
terns
of
response
for
cardiorespiratory
variables
are
illustrated
in
Figure
la
to
lf.
The
submaximal
pattern
of
change
during
the
ESWT
and
6MWT
was
curvilinear
for
all
variables
and
the
submaximal
pattern
of
change
during
the
ISWT
and
CET
was
linear
for
all
variables.
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(2012)
17,
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2011
The
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2011
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Respirology
A
comparison
of
exercise
tests
in
COPD
281
Peak
cardiorespiratory
responses
for
each
test
are
presented
in
Table
3.
Compared
with
each
walldng
test,
the
CET
elicited
a
greater
VCO
2
,
respiratory
exchange
ratio
and
V
E
as
well
as
a
smaller
decrease
in
SpO2.
There
was
no
difference
in
peak
V0
2
,
heart
rate
or
tidal
volume
among
the
tests.
The
small
variability
between
tests
observed
in
resting
measures
in
Figure
la
to
lf,
reflects
the
metabolic
load
associated
with
the
warm-up
period
and
unloaded
cycling
that
preceded
the
ESWT
and
CET,
respectively.
The
bias
and
coefficient
of
repeatability
for
gas
exchange
and
breathing
pattern
variables
collected
during
each
walldng
test
are
presented
in
Table
4.
Compared
with
data
collected
during
the
ISWT,
the
coefficients
of
repeatability
tended
to
be
narrower
for
data
collected
during
the
6MWT
and
ESWT.
DISCUSSION
This
is
the
first
study
to
compare
the
peak
and
sub-
maximal
cardiorespiratory
responses
across
three
field
walldng
tests
with
a
laboratory-based
CET
in
patients
with
COPD.
The
important
findings
of
this
study
are:
(i)
all
tests
elicited
similar
peak
V0
2
,
heart
rate
and
tidal
volume;
(ii)
the
CET
elicited
a
greater
peak
VCO
2
,
respiratory
exchange
ratio,
V
E
and
smaller
decrease
in
SpO2
compared
with
all
walldng
tests;
(iii)
the
submaximal
pattern
of
change
during
the
ISWT
and
CET
were
similar,
being
linear
for
all
variables;
and
(iv)
the
submaximal
pattern
of
change
during
the
6MWT
and
ESWT
were
similar,
being
cur-
vilinear
for
all
variables.
Further,
this
is
the
first
study
to
report
the
bias
and
coefficient
of
repeatability
for
measures
of
gas
exchange
and
breathing
pattern
variables
measured
during
walldng
tests.
Generally,
the
bias
for
each
measure
was
small
with
variables
measured
on
completion
of
the
6MWT
and
ESWT
demonstrating
narrower
coefficients
of
repeatability
compared
to
the
ISWT.
The
similar
peak
VO
2
and
heart
rate
during
the
ISWT
and
CET
corroborates
earlier
reports.'
5-
'
8
It
has
been
suggested
that
the
6MWT
is
most
likely
to
elicit
peak
cardiorespiratory
responses
in
people
with
COPD
following
an
acute
exacerbation,
32
or
in
those
with
profound
functional
limitation
33
or
severe
airflow
obstruction2
6
"
9
However,
our
data
reveal
that
among
Table
3
Peak
(end-test)
cardiorespiratory
responses
6MWT
ISWT
ESWT
CET
ANOVA
results
V0
2
(mL/min)
1168
±
344
1227
±
310
1232
±
368
1186
±
314
F
3
,
69
=
1.2;
P=
0.31
VCO
2
(mL/min)
1009
±
270t
1036
±
327t
1060
±
342*
1173
±
350
F3,62
=
4.8;
P=
0.006
Respiratory
exchange
ratio
0.87
±
0.11
t
0.84
±
0.10
t
0.86
±
0.12
t
0.99
±
0.17
F
3
,
69
=
18.7;
P<
0.001
V
E
(L/min)
41
±
17
1
43
±
15
1
44
±
16*
48
±
17
F
3
,
69
=
10.2;
P<
0.001
Tidal
volume
(L)
1.39
±
0.46
1.35
±
0.42
1.36
±
0.46
1.45
±
0.46
F
3
,
69
=
1.5;
P=
0.21
Heart
rate
(beats/min)
128
±
17
127
±
14
130
±
15
128
±
19
F2,50
=
0.6;
P=
0.58
SpO
2
(%)
88
±
5
t
88
±
5
t
88
±
5
t
95
±
4
F
3
,
63
=
24.9;
P<
0.001
Data
are
mean
±
SD.
*
P<
0.05
vs
CET;
t
P<
0.01
vs
CET.
The
subscripted
numbers
that
accompany
the
F-statistics
refer
to
the
degrees
of
freedom
available
for
the
between
and
within-group
comparisons.
ANOVA,
analysis
of
variance;
CET,
cycle
ergometry
test;
ESWT,
endurance
shuttle
walk
test;
ISWT,
incremental
shuttle
walk
test;
6MWT,
6-min
walk
test;
Sp0
2
,
arterial
oxygen
saturation
measured
via
pulse
oximetry;
1
.
70
2
,
rate
of
oxygen
uptake;
VCO2,
rate
of
carbon
dioxide
output;
V
E
,
minute
ventilation.
Table
4
Mean
difference
(bias)
and
coefficient
of
repeatability
for
peak
(end-test)
cardiorespiratory
responses
6MWT
ISWT
ESWT
t
Bias
Coefficient
Bias
Coefficient
Bias
Coefficient
V0
2
(mL/min)
-33
322
-56
414
-138
287
VCO
2
(mL/min)
-32
218
56
329
-76
218
Respiratory
exchange
ratio
-0.01
0.19
0.09
0.24
0.027
0.12
V
E
(L/min)
-0.61
9.62
3.21
12.60
-1.30
10.84
Tidal
volume
(L)
-0.03
0.38
0.03
0.45
-0.05
0.27
Heart
rate
(beats/min)
2
10
4
13
2
9
SpO
2
(%)
-1
6
0
4
1
8
t
Only
tests
performed
the
same
walk
speed
were
included
in
these
analyses.
Differences
between
tests
were
not
systematic
and
therefore
coefficients
of
repeatability
could
be
calculated
for
all
variables.
ESWT,
endurance
shuttle
walk
test;
ISWT,
incremental
shuttle
walk
test;
6MWT,
6-min
walk
test;
Sp0
2
,
arterial
oxygen
saturation
measured
via
pulse
oximetry;
1
.
70
2
,
rate
of
oxygen
uptake;
VCO
2
,
rate
of
carbon
dioxide
output;
V
E
,
minute
ventilation.
0
2011
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E
ci
>
a
1400
1200
1000
800
600
400
200
282
K
Hill
et
al.
b
1400
1200
1000
rc
800
E
600
ci
>
u
400
200
0
0
2
4
6
Time
(min)
c
0
10
0
2
4
6
Time
(min)
d
10
60
50
40
-
1.8
1.6
1.4
-
Lt
1.2
>:-
30
-
1.0
0.8
20
-
0.6
10
0
2
4
6
8
10
0
2
4
6
8
10
Time
(min)
Time
(min)
e
140
-
100
130
-
120
-
98
96
6
4--
4,--4
1:_,
--
E'
a
_a
110
-
N
94
92
cc
0
a
100
-
v
90
88
90
-
86
80
0
2
4
6
8
10
Time
(min)
0
2
4
6
8
10
Time
(min)
Figure
1
Data
are
mean
and
standard
error.
All
participants
contribute
to
each
data
point.
Figures
are
patterns
of
response
for;
(a)
rate
of
oxygen
uptake
(V0
2
),
(b)
rate
of
carbon
dioxide
output
(VCO
2
),
(c)
minute
ventilation
(V
E
),
(d)
tidal
volume
(V
T
),
(e)
heart
rate
(HR)
and
(f)
arterial
oxygen
saturation
measured
via
pulse
oximetry
(SpO
2
)
for
each
test.
•,
cycle
ergometry
test;
0,
6-min
walk
test;
M,
incremental
shuttle
walk
test;
El,
endurance
shuttle
walk
test;
*P<
0.05
for
difference
between
cycle
ergometry
with
all
other
tests.
Respirology
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2011
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Pacific
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A
comparison
of
exercise
tests
in
COPD
283
stable
participants
with,
on
average,
moderate
disease
(FEV
I
=
50
±
14
%
predicted)
and
modest
functional
limitation
(6-min
walk
distance
=
459
±
66
m),
the
6MWT
elicited
similar
peak
VO
2
and
cardiac
demands
as
both
the
CET
and
ISWT.
This
relates,
at
least
in
part,
to
the
utilization
of
a
6MWT
protocol
that
included
standardized
instructions,
encouragement
and
con-
sistent
performance
of
two
6MWTs
under
identical
conditions
on
the
same
day.
Many
of
the
participants
had
experience
with
the
6MWT;
a
factor
likely
to
account
for
the
modest
learning
effect
and
may
have
contributed
to
the
magnitude
of
response
elicited
during
the
6MWT.
Although
the
CET
elicited
greater
VCO
2
and
1
.
T
E
.
than
the
6MWT,
exercise
inten-
sity
is
usually
expressed
in
terms
of
VO
2
or
heart
rate
(as
a
surrogate
for
V0
2
)
and
therefore
our
data
reveals
that
a
standardized,
encouraged
6MWT
elicited
a
maximum
exercise
response
in
people
with
moderate
COPD,
with
modest
functional
limitation,
who
were
clinically
stable.
Our
data
show
remarkable
similarity
in
the
pattern
of
response
and
walldng
speeds
used
for
the
ESWT
and
6MWT.
This
contrasts
with
the
study
by
Pepin
et
al.
34
who
reported
a
greater
V
E
,
respiratory
rate
and
heart
rate
on
completion
of
the
ESWT
compared
with
the
6MWT,
despite
both
tests
being
conducted
at
similar
walldng
speeds.
This
disparity
may
be
related
to
differences
in
lung
function
and
exercise
capacity
between
the
study
samples.
Although
FEVI
(per
cent
predicted)
was
similar
between
samples,
the
absolute
FEV
I
and
the
forced
expiratory
ratio
were
lower
in
our
participants
(1.31
vs
1.18
L
and
46
vs
40%).
Further,
the
V0
2
and
distances
achieved
during
the
walldng
tests
were
considerably
greater
in
the
study
by
Pepin
et
al.
34
Taken
together,
it
appears
that
the
participants
in
this
earlier
study
were
characterized
by
less
severe
disease
and
better
exercise
capacity
34
and
the
capac-
ity
of
the
6MWT
and
ESWT
to
elicit
similar
cardio-
respiratory
responses
may
be
contingent
on
these
factors.
In
agreement
with
earlier
reports,
there
was
a
smaller
decrease
in
Sp0
2
16,19,39
together
with
a
higher
VCO
2
,
respiratory
exchange
ratio
and
V
E
during
the
CET
compared
with
the
walldng
tests.
19
'
19
These
differences
have
been
demonstrated
to
persist
when
walldng
and
cycling
modalities
were
matched
for
V0
2
36
and
appear
to
relate
to
the
greater
specific
load
placed
on
the
quadriceps
during
CET
32
eliciting
a
greater
accumulation
of
lactate
which
is
buffered
by
bicarbonate,
thereby
increasing
V
E
.
36
Regarding
the
pattern
of
response,
cardiorespiratory
variables
during
the
ISWT
and
CET
increased
in
a
linear
pattern
reflecting
the
incremental
increase
in
power"
whereas
the
cardiorespiratory
response
to
the
6MWT
and
ESWT
was
characterized
by
a
similar
magnitude
of
exponential
increase
over
the
first
50%
of
the
test,
followed
by
a
relative
plateau
in
response.
34
Figure
lc
demonstrates
that
at
time
points
before
test
comple-
tion,
V
E
was
higher
during
the
6MWT
and
ESWT,
compared
with
the
ISWT
and
CET;
data
that
support
a
previous
finding
of
greater
dyspnoea
during
the
6MWT
at
time
points
before
test
completion,
com-
pared
with
incremental
test
protocols.
16
It
appears
that
performance
during
the
6MWT
and
ESWT
was
influenced
by
the
capacity
of
an
individual
to
tolerate
near
maximum
levels
of
V
E
.
The
repeatability
of
cardiorespiratory
measures
collected
at
the
end
of
the
walldng
tests
was
similar
to
that
previously
reported
for
variables
measured
on
completion
of
CET.
29
The
somewhat
wider
coefficients
for
measures
collected
during
the
ISWT,
relative
to
the
6MWT
and
ESWT,
is
likely
to
reflect
that
any
increase
in
performance
during
the
ISWTs
resulting
from
familiarization
may
have
necessitated
an
increase
in
walldng
speed
and
considerable
increase
in
cardio-
respiratory
demand.
In
contrast,
the
coefficients
of
repeatability
calculated
for
data
collected
during
the
ESWT
pertain
only
to
tests
during
which
the
partici-
pants
walked
at
identical
speeds
and
there
was
a
trivial
difference
in
walking
speeds
during
the
two
6MWTs.
A
practical
application
of
these
data
is
that,
following
an
intervention,
to
be
95%
confident
that
any
difference
in
cardiorespiratory
response
collected
during
the
6MWT,
ISWT
or
ESWT
was
not
simply
due
to
normal
variability
inherent
in
these
tests,
the
magnitude
of
change
must
exceed
the
coefficient
of
repeatability.
Limitations
As
we
excluded
those
who
required
long-term
oxygen
therapy
or
ambulatory
aids,
our
results
may
not
extend
to
these
individuals.
It
is
possible
that
the
use
of
a
treadmill
rather
than
cycle
ergometer
would
have
allowed
the
participants
to
achieve
greater
a
VO
2
peak
during
the
laboratory
test.
36
Nevertheless,
the
CET
was
chosen
as
it
is
the
most
common
laboratory-
based
cardiopulmonary
exercise
test
in
people
referred
to
pulmonary
rehabilitation.'
We
did
not
collect
measures
of
inspiratory
capacity
and
therefore
cannot
comment
on
differences
in
hyperinflation
among
the
tests.
Although
a
similar
number
of
par-
ticipants
completed
the
6MWT
or
ISWT
during
the
first
assessment
session,
practical
issues
(e.g.
labora-
tory
availability)
prevented
full
compliance
with
the
randomization
sequence,
and
it
is
possible
that
our
results
were
affected
by
an
order
bias.
CONCLUSIONS
In
clinically
stable
participants
with
moderate
disease,
field
walking
tests,
when
conducted
accord-
ing
to
a
standardized
protocol,
elicited
similar
peak
VO
2
and
heart
rate
responses
as
a
CET.
These
data
suggest
that
both
self-
and
externally
paced
walking
tests
progress
to
very
high
intensities
and
therefore
appear
to
provide
a
basis
on
which
to
pre-
scribe
training
intensities
capable
of
inducing
physi-
ologic
adaptation.38'39
ACKNOWLEDGEMENTS
For
financial
support,
we
acknowledge
Physicians
Services
Incorporated
Foundation
(Canada).
Dr.
Brooks
is
supported
by
a
Canadian
Research
Chair
0
2011
The
Authors
Respirology
(2012)
17,
278-284
Respirology
0
2011
Asian
Pacific
Society
of
Respirology
284
K
Hill
et
al.
and
Dr.
Goldstein
by
the
NSA
Chair
in
Respiratory
Rehabilitation
Research.
We
also
acknowledge
the
assistance
of
Clarissa
Muere,
Sachi
O'Hoski,
Gail
Lang
and
Dr.
Diane
Flood
in
recruitment
and
data
collec-
tion
for
this
study.
REFERENCES
1
O'Donnell
DE,
Revill
SM,
Webb
KA.
Dynamic
hyperinflation
and
exercise
intolerance
in
chronic
obstructive
pulmonary
disease.
Am.
J.
Respir.
Crit.
Care
Med.
2001;
164:
770-7.
2
Saey
D,
Debigare
R,
LeBlanc
P
et
al.
Contractile
leg
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