Copyright #ERS Journals Ltd 2004
European Respiratory Journal
ISSN 0903-1936
Eur Respir J 2004; 24: 385–390
DOI: 10.1183/09031936.04.00128903
Printed in UK – all rights reserved
Dynamic hyperinflation and tolerance to interval exercise in patients
with advanced COPD
I. Vogiatzis*,#, S. Nanas*, E. Kastanakis}, O. Georgiadou#, O. Papazahou*, Ch. Roussos*
Dynamic hyperinflation and tolerance to interval exercise in patients with advanced
COPD. I. Vogiatzis, S. Nanas, E. Kastanakis, O. Georgiadou, O. Papazahou,
Ch. Roussos. #ERS Journals Ltd 2004.
ABSTRACT: Dynamic hyperinflation (DH) contributes importantly to the limitation
of constant-load exercise (CLE) in patients with chronic obstructive pulmonary disease
(COPD). However, its role in the limitation of interval exercise (IE) remains to be
explored.
The change (D) in inspiratory capacity (IC) was measured to reflect changes in DH in
27 COPD patients (forced expiratory volume in one second mean¡SEM % predicted:
40¡3) at the end of a symptom-limited CLE test at 80% of peak work capacity
(WRmax) and an IE test at 100% WRmax (30 s of work, alternated with 30 s of
unloaded pedalling).
At the limit of tolerance in both IE and CLE, patients exhibited similar DH (DIC:
0.39¡0.05 L and 0.45¡0.05 L, respectively). However, exercise endurance time (tend)
for IE (32.7¡3.0 min) was significantly greater than for CLE (10.3¡1.6 min). The IE
tend correlated with resting IC, expressed as % pred normal. At 30 and 90% of total IE
tend, DIC (0.43¡0.06 and 0.39¡0.05 L, respectively) and minute ventilation (31.1¡1.6
and 32.7¡2.2 L?min-1, respectively) were not significantly different.
Resting hyperinflation helps to explain the limitation of interval exercise.
Implementation of interval exercise for rehabilitation should provide important clinical
benefits because it prolongs exercise endurance time and allows sustaining higher stable
ventilation.
Eur Respir J 2004; 24: 385–390.
Recent studies have demonstrated the benefits of rehabilitative exercise training on exercise capacity, quality of life and
utilisation of healthcare resources in patients with chronic
obstructive pulmonary disease (COPD) [1]. Most rehabilitation programmes are based on constant-load exercise (CLE)
training, consisting of sustained exercise for 30–40 min [1].
Generally, high-intensity training is argued to be needed for
the improvement of exercise capacity [2]. Although patients
with moderately severe COPD (mean forced expiratory
volume in one second (FEV1) w45% predicted) can tolerate
high levels (80%) of their peak tolerance for several minutes
[3, 4], patients with more severe disease are unable to tolerate
such exercise intensities for sufficiently long periods [5, 6].
The factors that limit exercise tolerance in these patients are
linked with the development of dynamic hyperinflation (DH)
and the concurrent mechanical constraints on ventilation that
contribute importantly to perceived respiratory discomfort.
Secondary to DH and concomitant high mean intrathoracic
pressure, cardiac performance and, hence, supply of oxygenated blood to the malfunctioning peripheral muscles are
further compromised [7, 8]. This contributes to perceived leg
discomfort and exercise intolerance. The importance of
DH in exercise limitation in patients with advanced COPD
arises from studies which demonstrated that alleviation
of dyspnoea with acute bronchodilator therapy or oxygen
*Dept of Pulmonary and Critical Care
Medicine, Cardiopulmonary Rehabilitation
Centre, Eugenidion Hospital, #Dept of
Physical Education and Sport Science,
National and Kapodistrian University of
Athens, and }Third Pulmonary Dept, Seismanoglion Hospital, Athens, Greece.
Correspondence: I. Vogiatzis, National and
Kapodistrian University of Athens Medical
School, Dept of Pulmonary and Critical Care
Medicine, Eugenidion Hospital 2nd Floor,
20 Papandiamantopoulou Str 115-28 Ilisia,
Athens, Greece.
Fax: 30 2107242785
E-mail: gianvog@phed.uoa.gr
Keywords: Chronic obstructive pulmonary
disease, dynamic hyperinflation , dyspnoea,
interval exercise
Received: November 19 2003
Accepted after revision: May 10 2004
This work was supported in part by
the European Community. Project title: Computer Aided Rehabilitation of Respiratory
Disabilities (CARED) FP5 (contract no.
QLG5-CT-2002-0893).
supplementation is due, in part, to decreased operating lung
volumes [9–11]. Both interventions improved exercise endurance time (tend), which, nonetheless, remained brief (typically
y8–10 min).
Interval exercise (IE) training, which consists of maximalintensity exercise loads on peripheral muscles, has been used
by the current authors as an equally effective alternative to
CLE in patients with moderately severe COPD (mean FEV1
45% pred) [12]. Interestingly, the levels of dyspnoea in the IE
group during the training sessions were significantly lower
than in the CLE group. On the basis of the well-established
mechanistic link between the intensity of dyspnoea and the
degree of DH [13], the lower symptoms of dyspnoea during IE
might reflect smaller increases in dynamic lung volumes as
compared with CLE. However, there are no studies demonstrating the degree to which the behaviour of operating lung
volumes during IE influences exercise tolerance in patients
with severe COPD. Moreover, as IE consists of a sequence
of on and off high-intensity muscular loading events, its
tolerability in the context of perceived respiratory and
peripheral muscle discomfort is still unknown.
Accordingly, the objectives of the current study were as
follows: 1) to determine the range and pattern of change in the
operating lung volume components during IE in patients with
different degrees of airflow limitation; and 2) to investigate
386
I. VOGIATZIS ET AL.
whether IE could enable patients with advanced COPD to
tolerate high-intensity exercise for sufficiently long periods of
time.
Methods
Subjects
Subjects included 27 male patients with stable COPD who
satisfied the following criteria: 1) postbronchodilator FEV1
v50% pred and FEV1/forced vital capacity v65% without
significant reversibility (v12% change of the initial FEV1
value); 2) optimised medical therapy; and 3) no clinical
evidence of exercise-limiting cardiovascular or neuromuscular
diseases.
Study design
Patients underwent three symptom-limited exercise tests on
different days in the following order: 1) a ramp-incremental
test to define the peak work rate (WRmax); 2) a CLE test at a
work rate equivalent to 80% WRmax; and 3) an IE test at a
work rate that corresponded to 100% WRmax with 30 s work,
interspersed with 30 s of unloaded pedalling. All patients
signed an informed consent and the protocol was approved by
the current authors9 hospital ethics committee.
Pulmonary function tests
Spirometry and lung diffusion capacity for carbon monoxide (DL,CO) were performed by a spirometer (Masterlab;
Jaeger, Wurzburg, Germany) according to recommended
techniques [14], whereas maximum voluntary ventilation
(MVV) was directly measured (Vmax 229; Sensor Medics,
Anaheim, CA, USA). Arterial blood was drawn by puncture
of the radial artery at rest, whilst breathing room air for the
analysis of arterial oxygen tension (Pa,O2), carbon dioxide
tension (Pa,CO2) and pH (ABL330; Radiometer, Copenhagen,
Denmark).
capacity (IC), assuming that total lung capacity (TLC)
remained constant during exercise [18], thus reflecting changes
in end-expiratory and end-inspiratory lung volumes (EILV).
By subtracting VT from the coinciding IC, changes in
inspiratory reserve volume (IRV) were calculated. Prior to
exercise testing, patients were familiarised with the IC
manoeuvre, where they were instructed to make 3–5 maximal
efforts according to previously described methods, i.e. "at the
end of the next normal expiration, take a deep breath all the
way in", followed by verbal encouragement to make a
maximal effort before relaxing [18, 19]. Throughout exercise
testing, IC was measured every 3 min and at the end of
exercise. During the IE tests, IC measurements were carried
out during the 30-s work phases. Arterial blood for the
determination of Pa,O2, Pa,CO2, pH, alveolar–arterial oxygen
pressure difference, arterial–end tidal carbon dioxide pressure
difference and arterial lactate concentration was drawn before
and at the end of the tests.
Data analysis
Data were presented as mean¡SEM. A statistical significance of 0.05 was used for all analyses, with appropriate
Bonferroni corrections for multiple comparisons. During IE,
temporally matched (at 30, 60 and 90% of the total exercise
time) measurements for V9O2, fC, and V9E, corresponding to
successive 30-s intervals of work and unloaded pedalling, were
analysed by a two-way analysis of variance (ANOVA) with
repeated measures and the appropriate post hoc analysis.
Similarly, changes in IC and rates of perceived dyspnoea and
leg discomfort across the different work phases were assessed
by ANOVA with repeated measures. Within and between
group comparisons were performed using paired and
unpaired t-tests, respectively. Linear regression analysis was
performed using the least square method. When this analysis
was carried out using IE tend as a dependent variable, the
independent variables included the resting pulmonary function and IE measurements. The strongest significant contributors to tend were selected using stepwise multiple
regression analysis.
Results
Exercise testing
All tests were performed on an electromagnetically braked
cycle ergometer (Ergoline 800; Sensor Medics), with the
subjects maintaining a pedalling frequency of 60 rpm. Tests
were preceded by a 2-min rest period, followed by 3 min of
unloaded pedalling. The following pulmonary gas exchange
and ventilatory variables were recorded breath-by-breath
(Vmax 229; Sensor Medics): oxygen uptake (V9O2), carbon
dioxide output (V9CO2), respiratory exchange ratio, minute
ventilation (V9E), tidal volume (VT), and breathing frequency.
Cardiac frequency (fC) and percentage oxygen saturation
measured by pulse oximetry were determined using the R–R
interval from a 12-lead online electrocardiogram (Marquette
Max; Marquette Hellige GmbH, Freiburg, Germany) and a
pulse oximeter (Nonin 8600; Nonin Medical, Plymouth, MN,
USA), respectively. The modified Borg Scale was used to rate
the magnitude of perceived dyspnoea and leg discomfort
every 3 min throughout and upon cessation of exercise [15].
During the ramp-incremental test (increments of 5–10 W), the
anaerobic threshold (AT) was determined via the V-slope
technique [16]. The peak V9O2 values were compared with
those of JONES [17].
During exercise tests, changes in operational lung volumes
were evaluated from measurements of dynamic inspiratory
Patient characteristics
As shown in table 1, patients were characterised by severe
airflow limitation, moderate hypoxaemia and a substantially
reduced DL,CO with considerable alveolar ventilation/perfusion
inequality, as reflected by the high physiological dead space
(VD)/VT. Mean resting IC was reduced below normal limits
(v80% pred) at 1.98¡0.09 L or 67¡3% of the predicted
normal; predicted normal values for IC were calculated as
pred TLC–pred functional residual capacity [13, 18]. The 95%
confidence interval (CI) for resting IC measurements was
¡0.20 L or ¡6.9% pred. Exercise capacity was severely compromised because of ventilatory limitation, as peak exercise
V9E approached the maximal ventilatory capacity, i.e. mean
V9E/MVV was 90¡3% (table 2). The latter constitutes one
of the criteria when patient effort is usually considered to
be maximal [20]. At the limit of tolerance, patients9 EILV
closely approached their TLC, whereas IRV was reduced
to 0.28¡0.03 L or 4.4¡0.8% pred TLC. The lowest IRV value
that was achieved at the peak of symptom-limited incremental
exercise test was defined as minimal IRV [13]. At the limit
of tolerance, the change (D) in IC from its resting value
amounted to -0.52¡0.06 L or -17.6¡2.0% pred, which was
387
INTERVAL EXERCISE AND HYPERINFLATION IN COPD
well beyond the 95% CI of the resting value. The AT could be
identified in 22 out of 27 patients.
Table 1. – Physical and baseline pulmonary function characteristics of patients
Age yrs
Height cm
Weight kg
BMI kg?m-2
FEV1 L
FEV1 % pred
FVC L
FVC % pred
FEV1/FVC % pred
DL,CO % pred
Pa,O2 mmHg
Pa,CO2 mmHg
pH
Arterial lactate conc. mMol?L-1
VD L
VD/VT %
IC L
IC % pred
MVV L?min-1
67¡1
170¡1
76¡3
25.8¡0.8
1.14¡0.07
39.7¡2.6
2.44¡0.13
65.7¡3.8
47.3¡2.0
52.2¡3.6
71.0¡1.7
42.6¡1.0
7.42¡0.04
1.3¡0.1
0.36¡0.03
44¡2
1.98¡0.09
67¡3
46¡4
Data are presented as mean¡SEM. BMI: body mass index; FEV1:
forced expiratory volume in one second; % pred: percentage of
predicted value; FVC: forced vital capacity; DL,CO: transfer factor
for carbon monoxide; Pa,O2: arterial oxygen tension; Pa,CO2: arterial
carbon dioxide tension; conc.: concentration; VD: physiological dead
space; V T: tidal volume; IC: inspiratory capacity; MVV: maximum
voluntary ventilation. 1 mmHg=0.1 kPa.
Physiological responses during interval exercise
Average tend (32.7¡3.0 min) was significantly longer compared with the mean tend recorded for CLE (10.3¡1.6 min)
in the present study (table 3). The time course of changes
in V9O2, V9CO2, V9E and IC during the IE protocol in
two representative patients is shown in figure 1. ANOVA
with repeated measures revealed that measurements of V9O2,
V9CO2 and V9E did not differ significantly between work and
unloaded pedalling phases in either of the temporally matched
measurements that were taken at time points corresponding
to 30, 60 and 90% of the total duration during IE (table 4).
Similarly, IC did not differ significantly across the different
work phases (table 4).
Measurements of operational lung volumes
At the end of symptom-limited IE, IC was significantly
reduced from its baseline value by 0.39¡0.05 L; this
corresponded to a mean DIC of -20¡4% or -13¡2% pred,
which was well beyond the 95% CI for IC. IE produced
significant volume constraints on VT expansion, indicated
by the higher reduction in IRV in the current authors9
COPD population than in normal populations (table 3) [13].
However, at the end of IE, the IRV value (8.9¡0.8% pred
TLC) was significantly higher compared to the minimal IRV
that was recorded at the limit of tolerance during the rampincremental and CLE tests (tables 2 and 3).
Table 3. – Responses to constant-load exercise (CLE) and
interval exercise (IE) protocols
Table 2. – Peak responses to the ramp-incremental exercise
test
WR W
WR % pred
V9O2 L?min-1
V9O2 % pred
V9CO2 L?min-1
R
V9E L?min-1
V9E/MVV %
BR L?min-1
V9E/V9O2
V9E/V9CO2
VT L
f breaths?min-1
fC beats?min-1
fC % pred
AT L?min-1
SP,O2 %
IC L
IC % pred
DIC from rest L
DIC from rest % pred
VT/IC %
IRV L
IRV % pred TLC
Dyspnoea Borg
Leg discomfort Borg
76¡5
51¡3
1.09¡0.07
54¡3
1.10¡0.08
1.01¡0.03
40.0¡2.1
90¡3
6.4¡3.9
37.9¡1.4
38.6¡1.4
1.18¡0.06
34¡1
126¡4
83¡2
0.74¡0.04
90¡2
1.46¡0.10
49.5¡3.1
-0.52¡0.06
-17.6¡2.0
80.8¡1.7
0.28¡0.03
4.4¡0.8
4.7¡0.3
5.0¡0.3
Data are presented as mean¡SEM. WR: work rate in watts; % pred:
percentage of predicted value; V9O2: oxygen uptake; V9CO2: carbon
dioxide output; R: respiratory exchange ratio; V9E: minute ventilation;
MVV: maximum voluntary ventilation; BR: breathing reserve; V9E/
V9O2: ventilatory equivalent for V9O2; V9E/V9CO2: ventilatory equivalent
for V9CO2; VT: tidal volume; f: breathing frequency; fC: cardiac
frequency; AT: anaerobic threshold (identified in 22 out of 27 patients);
SP,O2: arterial oxygen saturation measured by pulse oximetry; IC:
inspiratory capacity; DIC from rest: change in IC from rest; IRV:
inspiratory reserve volume; TLC: total lung capacity.
Exercise time min
V9O2 L?min-1
V9CO2 L?min-1
R
V9E L?min-1
V9E/MVV %
VT L
f breaths?min-1
fC beats?min-1
IC L
IC % pred
DIC L
DIC % pred
VT/IC %
IRV L
IRV % pred TLC
Pa,O2 mmHg
Pa,CO2 mmHg
pH
VD L
VD/VT %
Arterial lactate conc. mMol?L-1
Dyspnoea Borg
Leg discomfort Borg
End of CLE
End of IE
10.3¡1.6
0.94¡0.07
0.95¡0.07
1.00¡0.02
38.4¡2.2
85¡3
1.14¡0.06
34¡1
128¡5
1.53¡0.08
51.9¡3.0
-0.45¡0.05
-15.2¡2.4
75.2¡1.7
0.38¡0.03
5.9¡0.5
66.7¡2.6
45.4¡1.2
7.34¡0.07
0.53¡0.02
46¡6
5.81¡0.41
4.8¡0.3
4.9¡0.4
32.7¡3.0#
0.81¡0.05#
0.75¡0.04#
0.95¡0.02#
33.1¡1.5#
76¡4#
1.01¡0.05#
33¡1
123¡5
1.59¡0.08}
53.9¡2.6}
-0.39¡0.05}
-13.3¡1.5}
66.4¡2.0#,}
0.58¡0.06#,}
8.9¡0.8#,}
68.7¡2.5
44.0¡1.3#,z
7.38¡0.06#,z
0.48¡0.02#,z
47¡8z
3.89¡0.36#,z
4.3¡0.3
4.6¡0.5
Data are presented as mean¡SEM. V9O2: oxygen uptake; V9CO2: carbon
dioxide output; R: respiratory exchange ratio; V9E: minute ventilation;
MVV: maximum voluntary ventilation; VT: tidal volume; f: breathing
frequency; fC: cardiac frequency; IC: inspiratory capacity; DIC: change
in IC from rest; IRV: inspiratory reserve volume; IRV % pred TLC:
IRV as a percentage of the predicted value for total lung capacity;
Pa,O2: arterial oxygen tension; Pa,CO2: arterial carbon dioxide tension;
VD: physiological dead space; conc.: concentration. #: significant
differences between IE and CLE; }: significant differences between the
incremental exercise test (table 2) and the terminal point of the IE test;
z
: significant differences between baseline and the terminal point of the
IE test. 1 mmHg=0.1 kPa.
388
a)
I. VOGIATZIS ET AL.
b)
1.20
1.20
l
l l
l
l
l
l l
l
l l
ll
lll l
llll l ll l l lll
l
l
l
l
l
l
l
l
ll
ll lll
l
ll l l
ll ll l
lll
l
l
l lll
l
ll
ll l
l
l l lllllllllllll l l ll l lll
l l
lll l l
lll l l lll l lll
0.90
V'CO2 L·min-1
V'O2 L·min-1
0.90
l
l
s
s
s
sss sss
s sssss s ss
sssss s s s
ss
s ss
s
s s ss ssss
s ss s
l s
s
s
0.60
l
l ll s
s
0.30 uuuulss
ls s
l
l
uuuus s s
uuuus
0.00
40.0
l
l
ll
l
l l
l
l l lll
l
l
l
l
l
l
l
l
l
l
ll
l
l l
l ll
l
l
lll l
l ll
l
l l lll
s
l
l l l
l
s
l
ls
l
ss s sssss
s
s
s
s
s
s
s
s
ll
s
s
s s
s
ss s
s
s
s ss
s
l
s
ss
d)
s
s
IC L
0.00
32.5
V'E L·min-1
s
sss ss s
s
sss ss
sss ss sssss ss sssssss s sss s
s
s
ss
s ss
ss
l
l ll s
l ss
l s
0.30
uuuus
c)
l
0.60
l
ll
u
2.00
s
s
s
l ss
ss
s
l
25.0
2.30
l
1.70
l
l
s
s
l
l
l
u
s
s
l
17.5 uuuu lss s
1.40
s
s
uuu s
uu
s
10.0
0.0
s
s
8.5
17.0
25.5
Endurance time min
34.0
1.10
0.0
8.5
17.0
25.5
Endurance time min
34.0
Fig. 1. – Time course of a) oxygen uptake (V9O2), b) carbon dioxide output (V9CO2), c) minute ventilation (V9E) and d) inspiratory capacity (IC)
in a patient with CO2 retention (arterial carbon dioxide tension w45 mmHg; + and ') and a patient without CO2 retention ($ and #) during
the interval exercise protocol. Gas exchange values are 30-s average measurements of baseline (% and )), unloaded pedalling phases (open
symbols) and interval exercise loaded phases (closed symbols). Dashed lines represent the onset of interval exercise.
r=-0.58, pv0.001, respectively) and Pa,O2 (r=0.55, pv0.001 and
r=0.44, pv0.02, respectively).
Correlates of interval exercise tolerance
The tend (32.7¡3.0 min) correlated with resting IC,
expressed as % pred normal (r=0.46, pv0.01), and, additionally, with the Pa,CO2 (r=-0.44, pv0.02) and the VT (r=0.43,
pv0.01), both recorded at the limit of tolerance during IE.
Using stepwise multiple regression analysis, tend was best
described by the combination of VT and IC % pred recorded
at the terminal point of IE (r=0.55, pv0.02). In turn, IC %
pred and VT at the limit of tolerance during IE correlated
strongly with the end exercise Pa,CO2 (r=-0.64, pv0.0001 and
Exertional symptoms
During IE, symptoms of dyspnoea and leg discomfort
increased significantly across the temporally matched time
points (table 4). At the limit of tolerance, symptoms were not
significantly different compared with those recorded at the
end of the incremental (table 2) and the CLE (table 3)
protocols.
Table 4. – Responses to interval exercise at temporally matched time points between work and unloaded pedalling phases
30% total time
V9O2 L?min-1
V9E L?min-1
fC beats?min-1
IC L
Dyspnoea Borg
Leg discomfort Borg
60% total time
90% total time
Work phase
Unloaded phase
Work phase
Unloaded phase
Work phase
Unloaded phase
0.74¡0.04
31.1¡1.6
113¡5
1.55¡0.08
2.9¡0.2
3.1¡0.3
0.74¡0.04
31.0¡1.5
114¡6
0.77¡0.05
32.0¡1.8
118¡5#
1.61¡0.08
3.3¡0.3#
3.6¡0.4#
0.77¡0.05
32.0¡2.0
118¡7
0.78¡0.04
32.7¡2.2
120¡4#
1.59¡0.08
4.3¡0.4#
4.6¡0.5#
0.78¡0.05
32.3¡2.0
120¡5
Data are presented as mean¡SEM. V9O2: oxygen uptake; V9E: minute ventilation; fC: cardiac frequency; IC: inspiratory capacity. #: significant
differences between the work phases of the temporally matched time points recorded at 30% of the total exercise time and those recorded at 60 and
90% of the total exercise time.
389
INTERVAL EXERCISE AND HYPERINFLATION IN COPD
Arterial blood gases, arterial lactate concentration and
anaerobic threshold
At the limit of tolerance during IE, there was a significant
increase in Pa,CO2 and VD from rest (table 3). Arterial lactate
concentration was significantly higher, and arterial pH
was lower, at the end of IE compared to baseline. Compared
to the terminal point of CLE (table 3), arterial lactate
concentration, Pa,CO2 and VD were significantly lower, and
arterial pH was higher, at the end of IE. V9O2 at the AT
(0.74 L?min-1) was not significantly different to the mean V9O2
(0.78 L?min-1) sustained during IE in the 22 patients whose
AT was identified.
Discussion
The principal aim of the present study was to evaluate the
influence of DH on IE tolerance in patients with severe
airflow limitation. Additionally, it was examined whether IE
would enable such patients to tolerate high-intensity exercise
for a sufficient time to achieve physiological training effects.
The main findings were as follows: 1) the total exercise
duration during IE was significantly greater than at CLE; 2)
IE was associated with stable metabolic and ventilatory
responses as the mean exercise V9O2 was slightly above the
patients9 AT; this, in turn, allowed patients to exercise for a
prolonged period of time before symptoms limited the
exercise endurance capacity; and 3) symptom-limited IE tend
correlated with resting hyperinflation.
Historically, the rationale for IE training has been the
ability to impose very high power outputs to peripheral
muscles without overloading the cardiorespiratory capacity
[21]. Classical studies [21] have shown that the metabolic
response during IE is very similar to continuous moderate
exercise and, thus, is associated with a stable pattern of
cardiorespiratory responses and low lactate concentration
in the muscle throughout the relatively long exercise and
recovery periods. This was shown in the present study by the
fact that IE was associated with a relatively stable metabolic
and ventilatory response, i.e. V9O2 and V9E changed very
little throughout the exercise and unloaded pedalling phases,
and corresponded to values typically seen during CLE at
markedly lower intensity (50–70% WRmax) in patients with
similar degrees of airflow limitation [22, 23]. Interestingly, in
spite of the fact that mean symptom-limited V9O2 was slightly
above the patients9 AT, the tend was relatively long, which
was not the case during CLE (table 3) above the AT [3].
Moreover, the small increase in arterial lactate concentration
to the terminal point of exercise further supports the notion
that IE closely resembled steady-state exercise. The capacity
to reload myoglobin stores during the recovery phases,
allowing a more oxidative degradation of glycogen and,
hence, a partially reduced demand, has been proposed as
the principal mechanism for the slowed glycolysis observed
during IE [21]. As lactic acidosis puts particular stress on
the ventilatory system, the small increase in arterial lactate
concentration observed during IE as compared to CLE
(table 3) appeared to be beneficial to the COPD patients by
reducing some of the acid stimulus to breathe [4], thereby
maintaining ventilation and dyspnoea at sustainable levels for
a prolonged period of time.
This is the first study to document DH during IE in COPD
patients. Patients were dynamically hyperinflated throughout
the IE test, as shown by the significant reduction in IC
from baseline, which averaged y0.40 L or 13% of IC pred
normal. This is similar to the values reported by O9DONNELL
and colleagues [9, 22, 23] during CLE in patients with a
comparable degree of severity and close to the value (0.45 L)
recorded during the CLE protocol in the present study
(table 3). An interesting feature of the present study was that
IC did not change significantly throughout IE in contrast to
CLE [9, 23]. In spite of DH, the current authors9 patients were
able to sustain bouts of maximal-intensity loads for a period
of time that was several times longer compared to the present
and other CLE protocols [3, 4, 9, 10, 11, 22, 23]. Whilst facing
steady metabolic and ventilatory demands during IE, patients
were able to sustain levels of pulmonary ventilation averaging
76% MVV at the terminal point of exercise for a prolonged
period. This is further supported by the finding that, even at
the limit of tolerance, the patients9 IRV was significantly
higher (p=0.01) than the IRV attained at the end of the
incremental and CLE tests (0.58¡0.06 L versus 0.28¡0.03 L
and 0.38¡0.03 L, respectively).
In agreement with previous studies [6, 9, 10, 23, 24], it was
found that, at the limit of interval exercise tolerance, IC and
VT were the most important contributors to tend. This is not
surprising as the dynamic IC has been shown to reflect the
operating limits for VT expansion during incremental [13, 24]
and CLE protocols [9, 10, 23]. The Pa,CO2 also emerged as
a significant contributory variable to endurance capacity,
confirming previous findings that the propensity to develop
CO2 retention during exercise reflects ventilatory constraints
due to prolonged hyperinflation [6–26]. In turn, IC % pred
normal and the curtailed VT response at the limit of IE
tolerance were strongly correlated with changes in Pa,CO2 and
Pa,O2 from baseline, thus reflecting the effects of worsening
alveolar ventilation/perfusion inequalities.
In summary, it has been shown that, in severely disabled
chronic obstructive pulmonary disease patients, interval
exercise is associated with stable metabolic demands, minute
ventilation and rates of dynamic hyperinflation, and that the
total exercise duration is much greater than at constant-load
exercise. Hence, the application of this method in the
rehabilitation setting has the potential to convey important
clinical benefits, as it allows the application of intense loads
on peripheral muscles for sufficiently long periods of time in
order to obtain the desired physiological training effects.
Interval exercise may, therefore, provide a good alternative
to constant-load rehabilitative exercise training in order to
improve compliance with high-intensity exercise and, thus,
the effectiveness of this treatment.
References
1.
2.
3.
4.
5.
6.
ACCP/AACVPR Pulmonary Rehabilitation Guidelines
Panel, American College of Chest Physicians, American
Association of Cardiovascular and Pulmonary Rehabilitation. Pulmonary rehabilitation: joint ACCP/AACVRR
evidence based guidelines. Chest 1997; 112: 1363–1396.
Casaburi R. Special considerations for exercise training. In:
ACSM resource manual for guidelines for exercise testing
and prescription. 4th Edn. ACSM, 2001; pp. 346–352.
Neder A, Jones PW, Nery LE, Whipp BJ. Determinants of
the exercise endurance capacity in patients with chronic
obstructive pulmonary disease. Am J Respir Crit Care Med
2000; 162: 497–504.
Casaburi R, Patessio A, Ioli F, Zanaboni S, Donner CF,
Wasserman K. Reductions in lactic acidosis and ventilation
as a result of exercise training in patients with obstructive
lung disease. Am Rev Respir Dis 1991; 143: 9–18.
Maltais F, LeBlank P, Jobin J, et al. Intensity of training and
physiologic adaptations in patients with chronic obstructive
pulmonary disease. Am J Respir Crit Care Med 1997; 155:
555–561.
O9Donnell DE, D9Arsigny, Fitzpatrick M, Webb KA.
Exercise hypercapnia in advanced chronic obstructive
390
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
I. VOGIATZIS ET AL.
pulmonary disease. The role of lung hyperinflation. Am
J Respir Crit Care Med 2002; 166: 663–668.
A statement of the American Thoracic Society and the
European Respiratory Society. Skeletal muscle dysfunction
in chronic obstructive pulmonary disease. Am J Respir Crit
Care Med 1999; 159: S1–S40.
Aliverti A, Maklem PT. How and why exercise is impaired in
COPD. Respiration 2001; 68: 229–239.
O9Donnell DE, Lam M, Webb KA. Spirometric correlates of
improvement in exercise performance after anticholinergic
therapy in chronic obstructive pulmonary disease. Am
J Respir Crit Care Med 1998; 160: 542–549.
O9Donnell DE, D9Arsigny C, Webb KA. Effects of
hyperoxia on ventilatory limitation during exercise in
advanced chronic obstructive pulmonary disease. Am
J Respir Crit Care Med 2001; 163: 892–898.
Somfay A, Porszasz SM, Lee SM, Casaburi R. Doseresponse effect of oxygen on hyperinflation and exercise
endurance in nonhypoxaemic COPD patients. Eur Respir J
2001; 18: 77–84.
Vogiatzis I, Nanas S, Roussos C. Interval training as an
alternative modality to continuous exercise in patients with
COPD. Eur Respir J 2002; 20: 12–19.
O9Donnell DE, Revill SM, Webb KA. Dynamic hyperinflation and exercise intolerance in chronic obstructive
pulmonary disease. Am J Respir Crit Care Med 2001; 164:
770–777.
Gardner RM, Hankinson JL, Clausen JL, Crapo RO,
Johnson Jr RO, Epler GR. American Thoracic Society
standardization of spirometry: 1987 update. Am Rev Respir
Dis 1987; 136: 1285–1298.
Borg GA. Psychophysical bases of perceived exertion. Med
Sci Sports Exerc 1982; 14: 377–381.
Sue DY, Wasserman K, Moricca RB, Casaburi R. Metabolic
acidosis during exercise in patients with chronic obstructive
pulmonary disease. Chest 1988; 94: 931–938.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
Jones NJ. Clinical exercise testing. 3rd Edn. Philadelphia,
WB Saunders Company, 1988; pp. 243–247.
Yan S, Kaminski D, Sliwinsky P. Reliability of inspiratory capacity for estimating end-expiratory lung volume
changes during exercise in patients with chronic obstructive
pulmonary disease. Am J Respir Crit Care Med 1997; 156:
55–59.
O9Donnell DE, Webb KA. Exertional breathlessness in
patients with chronic airflow limitation: the role of lung
hyperinflation. Am J Respir Crit Care Med 1993; 148: 1351–
1357.
Joint ATS/ACCP statement on cardiopulmonary exercise
testing. Assessment of patient effort. Am J Respir Crit Care
Med 2003; 167: 211–277.
Astrand PO, Rodahl K. Physical training. In: Astrand PO,
Rodahl K, eds. Textbook of work physiology. New York,
McGraw-Hill, 1986; pp. 412–476.
O9Donnell DE, McGuire M, Samis L, Webb KA. General
exercise training improves ventilatory and peripheral muscle
strength and endurance in chronic airflow limitation. Am
J Respir Crit Care Med 1998; 157: 1489–1497.
O9Donnell DE, Lam M, Webb KA. Measurement of symptoms, lung hyperinflation and endurance during exercise
in chronic obstructive pulmonary disease. Am J Respir Crit
Care Med 1998; 158: 1557–1565.
Diaz O, Villafrance C, Ghezzo H, et al. Breathing pattern
and gas exchange at peak exercise in COPD patients with
and without tidal flow limitation at rest. Eur Respir J 2001;
17: 1120–1127.
Cloosterman SG, Hofland ID, van Schayck CP, Folgering HT.
Exertional dyspnoea in patients with airway obstruction, with
and without CO2 retention. Thorax 1998; 53: 768–774.
Diaz O, Villafrance C, Ghezzo H, et al. Role of inspiratory
capacity on exercise tolerance in COPD patients with and
without tidal flow limitation at rest. Eur Respir J 2000; 16:
269–275.