Online Data Supplement
PARADOXICAL MOVEMENT OF THE LOWER RIB CAGE DURING EXERCISE IN
COPD PATIENTS
Andrea Aliverti, Marco Quaranta, Biswajit Chakrabarti
Andre Luis Pereira Albuquerque, and Peter M. Calverley
1
Methods
Ensemble average
Inspiratory Paradox time and Phase shift at each level of workload were calculated starting
from time courses of chest wall volumes. After the identification of end-expiratory times, the
ensemble average time courses of each compartment were obtained by time normalizing three
consecutives breaths (i.e., obtaining by linear interpolation a volume value every 1% from 0 to
100% of respiratory cycle time) and then averaging the corresponding values.
Repeatability test
An intra-observer repeatability test was performed to verify if the choice of the breaths could
influence the results. In each patient, at each level of workload, two different series of three
consecutive breaths were chosen randomly. After the calculation of the ensemble average (see
above), Inspiratory Paradox time (IP) and Phase shift (θ) were computed by applying the
methods described in the main manuscript. Successively, the algebraic differences of the
values of IP and θ (∆IP and ∆θ respectively) obtained in the two cases were calculated.
Results were analyzed with descriptive statistics and reported in the whisker plots of figures
E1-a and E1-b (control group) and E2-a and E2-b (COPD patients).
Control group. The measurements previously described for COPD were applied to the
control group to verify in particular if the choice of different breaths could alter significantly
the thresholds and therefore the subdivision of the COPD patients in the two subgroups. As
reported in the table E1, different choices of breaths during QB implied an absolute difference
in the thresholds for Phase shift and IP of 0.4° and 4.6% respectively. Such a small difference
2
was not enough to determine any change in the subdivision of the patients group into P+ and P. Differences in phase shift both at rest and during exercise had a distribution whose 25th and
75th were always lower than 10° (figures E1-a and E1-b). The variability in the distribution of
∆IP was higher, especially at maximum workload (75th percentile=16.97); however, values at
rest and during unloaded to moderate exercise had a distribution very close to their median
(25th and 75th percentile always lower than 10%) (Fig. E1-b).
COPD patients’ group. During quiet breathing the differences of Phase shift and Inspiratory
Paradox time obtained from two different series of consecutive breaths were very small as in
the control group. As shown in figures E2-a and E2-b, differences had a median value of
0.415° and 0.0%, respectively for ∆θ and ∆IP. Furthermore, the values were distributed very
close to their median: 25th and 75th percentiles of the distributions are 0.074° and 4.694° for
∆θ, -0.078% and 4.935% for ∆IP. Thus, during quiet breathing a different choice of the
breaths for the analysis of lower rib cage paradox causes in 75% of the samples a variation of
the values of θ and IP which is lower than 4.694° and 4.935% respectively. Again, different
choices of the series of consecutive breaths did not influence the inclusion of the patients in
one of the two subgroups (Table E1). During exercise the variability of the differences
increased, probably due to increased noise overlapped to the signal. However, the median
absolute values never overcame 3.9° and 6.8% for ∆θ and ∆IP respectively. The 25th and 75th
percentiles of the distributions of ∆θ and ∆IP were always included in the range of abut ±10°
and ±10%, except for ∆IP during unloaded exercise (25th =-12.9%).
Reproducibility test
3
The reproducibility of the method was tested in 14 patients to verify if the positioning of the
markers by different operators could affect the obtained results. The boundaries between the
three compartments, represented by the xiphoid process (between RC,p and RC,a) and the
lower costal margin (between RC,a and Ab) are in fact determined by the positioning of the
markers and this could be influenced by different operators.
Three of the subjects included in the study (specifically subjects #3, #5 and #12) underwent
the protocol in three different occasions, with markers positioned by two different operators.
The period between the first and the last test was no longer than 6 months. Figures E3-a and
E3-b show the values of Phase shift and Inspiratory Paradox time obtained during quiet
breathing in the three tests. In all the subjects these values were not significantly different in
the three tests. In subject #3 (black circles, classified as P+), θ varied between 135.88° and
163.27° and IP varied between 50.00% and 65.52%. Therefore, both indices were above
thresholds in all the three tests. In subject #5 (white circles, classified as P-), θ varied between
1.75° and 8.38° and IP between 8.57% and 17.50%. Therefore, both indices were always below
the threshold. In subject #12 (black triangles, classified as P-), θ varied between 18.38° and
38.08° while IP varied between 10.00% and 14.71%.
Expiratory flow limitation
A full presentation for all 20 individuals of the tidal and maximum flow volume loops together
with the individual plots of pulmonary and abdominal ribcage volume variations at rest and
end-exercise are presented figures E4a-e. Tidal flow volume loops were obtained by
integrating the flow signal measured by a pneumotachograph during rest, maximal exercise and
forced expiratory maneuvers. The correction of the integration drift in the volume signal was
4
performed by aligning it with chest wall volumes at end-inpiration in the different conditions.
In some individuals, data from either Negative Expiratory Pressure (NEP) [1] or Forced
Oscillation Technique (FOT) [2] or both methods were available and in table E2 the results
obtained from this analysis are reported. The comparison of flow volume loops with the NEP
and FOT data at rest showed that instances where the tidal flow volume loop exceeded the
maximum throughout the course of the breath were consistently associated with expiratory
flow limitation detected by NEP and/or FOT and this was not true when the tidal loop fell
below the maximum loop for some part or all of the breath. As known, the analysis of the
presence of expiratory flow limitation by tidal flow-volume loops is however critical, because
affected by the effect of gas compression during forced expiration [3].
REFERENCES
1. Koulouris NG, Valta P, Lavoie A, Corbeil C, Chassé M, Braidy J, Milic-Emili J. A simple
method to detect expiratory flow limitation during spontaneous breathing. Eur Respir J. 1995
Feb;8(2):306-13
2. Dellacà RL, Santus P, Aliverti A, Stevenson N, Centanni S, Macklem PT, Pedotti A,
Calverley PM. Detection of expiratory flow limitation in COPD using the forced oscillation
technique. Eur Respir J. 2004 Feb;23(2):232-40.
3. Ingram RH Jr, Schilder DP. Effect of thoracic gas compression on the flow-volume curve of
the forced vital capacity. Am Rev Respir Dis. 1966 Jul;94(1):56-63.
5
FIGURES AND TABLES LEGENDS
Fig. E1-a. Whisker plots of ∆θ during exercise in the control group (n=10). Grey boxes: lower
limit: 25th percentile, upper limit 75th percentile, continuous line: median, dashed line: mean.
Error bars: 10th and 90th percentile. Black dots: 5th and 95th percentile. QB: quiet breathing, UL:
unloaded exercise.
Fig. E1-b. Whisker plots of ∆IP during exercise in the control group (n=10). Grey boxes:
lower limit: 25th percentile, upper limit 75th percentile, continuous line: median, dashed line:
mean. Error bars: 10th and 90th percentile. Black dots: 5th and 95th percentile. QB: quiet
breathing, UL: unloaded exercise
Fig. E2-a. Whisker plots of ∆θ during exercise in the COPD group (n=14). Grey boxes: lower
limit: 25th percentile, upper limit 75th percentile, continuous line: median, dashed line: mean.
Error bars: 10th and 90th percentile. Black dots: 5th and 95th percentile. QB: quiet breathing, UL:
unloaded exercise.
Fig. E2-b. Whisker plots of ∆IP during exercise in the COPD group (n=14). Grey boxes: lower
limit: 25th percentile, upper limit 75th percentile, continuous line: median, dashed line: mean.
Error bars: 10th and 90th percentile. Black dots: 5th and 95th percentile. QB: quiet breathing, UL:
unloaded exercise.
Fig. E3-a. Phase shift (θ) during QB in the 3 tests. Black circles: Subject #3, white circles:
Subject #5, black triangles: Subject #12, dashed straight line: threshold.
Fig. E3-b.Inspiratory Paradox time (IP) during QB in the 3 tests. Black circles: Subject #3,
white circles: Subject #5, black triangles: Subject #12, dashed straight line: threshold.
6
Fig. E4
Left panels: dynamic flow-volume loops during quiet breathing, maximal exercise and forced
expiratory maneuver.
Right panels: dynamic loop of volume changes of pulmonary rib cage vs abdominal rib cage
during quiet breathing (thin lines) and maximal exercise (thick line). Closed circles: endexpiration; closed triangles: end-inspiration; arrows: direction of the loops. Volumes of each
compartment is referred to mean end-expiratory volume of that compartment at rest.
In figures E4-a and E4-b are reported data of P+ patients, while in figures E4-c, E4-d and E4-e
data of P- patients.
Fig. E5
Volume variations of upper (solid lines) and lower (dashed lines) rib cage during quiet
breathing (black lines) and maximal exercise (blue lines). As in fig. E4, volumes of each
compartment is referred to mean end-expiratory volume of that compartment at rest.
In figures E5-a are reported data of P+ patients, while in figures E5-b and E5-c data of Ppatients.
7
Table E1. Phase shift (θ) and Inspiratory Paradox time (IP) at rest in COPD patients. 1 st trial
refers to the values used in the paper, 2nd trial refers to the values calculated to test the
repeatability of the method.
Table E2. Classification of patients as expiratory flow limited (FL) or not flow limited (NFL)
in which data from either Negative Expiratory Pressure (NEP) or Forced Oscillation Technique
(FOT) or both methods were available.
8
Fig. E1-a
40
Phase shift (Deg)
30
20
10
0
-10
-20
-30
-40
QB
UL
50
100
% Maximum workload
Fig. E1-b
IP (% Inspiratory time)
40
30
20
10
0
-10
-20
-30
-40
QB
UL
50
100
% Maximum workload
9
Figure E2-a
40
Phase shift (Deg)
30
20
10
0
-10
-20
-30
-40
QB
UL
50
100
% Maximum workload
Figure E2-b
IP (% Inspiratory time)
30
20
10
0
-10
-20
-30
-40
QB
UL
50
100
% Maximum workload
10
Figure E3-a
Phase shift (Degrees)
180
160
140
120
100
80
60
40
20
0
st
1 test
2
nd
test
rd
3 test
Figure E3-b
IP (% Inspiratory time)
70
60
50
40
30
20
10
0
st
1 test
nd
2
11
test
rd
3 test
Table E1
Patient
#1
#2
#5
#6
#7
#10
#12
#13
#3
#4
#8
#9
#11
#14
 (degrees)
1st
2nd
11.1
12.4
10.2
10.1
6.7
4.7
7.9
7.7
18.0
18.0
8.4
3.7
18.4
7.2
5.4
4.8
135.9
148.7
37.4
31.1
16.9
17.8
58.4
44.4
27.3
23.3
43.5
43.7
IP (%)
1st
28.9
5.3
17.5
5.6
17.2
5.3
14.7
16.7
65.5
36.4
25.0
30.6
41.0
28.6
2nd
20.0
22.5
28.9
7.9
18.0
2.9
7.3
9.8
65.5
31.4
25.0
30.6
40.5
30.0
Table E2
Patient
#3
#4
#5
#10
#12
#16
Classification
NEP
FOT
FL
FL
FL
NFL
NFL
NFL
FL
FL
FL
FL
12
Classification
1st
2nd
PPPPPPPPPPPPPPPPP+
P+
P+
P+
P+
P+
P+
P+
P+
P+
P+
P+
Figure E4-a
0.6
3
Patient #3
Patient #3
2
0.5
quiet breathing
exercise
0.4
Vrc,p (liters)
flow (L/sec)
1
0
-1
-2
quiet breathing
0.3
0.2
0.1
=136°
IP=66%
=0.20
-3
0.0
-4
exercise
-0.1
-0.2
0.8
-5
3
2
1
0
-1
-2
4
0.8
1.0
0.6
Vrc,p (liters)
2
flow (L/sec)
0.2 0.6
Patient #4
Patient #4
0
-2
0.4
0.2
=37°
IP=36%
=0.16
0.0
-4
-0.2
-0.1
0.7
-6
3
2
1
0
3
Patient #8
0.0
0.1
0.2
0.3
0.4
Patient #8
2
0.6
1
0.5
Vrc,p (liters)
flow (L/sec)
0.0
0
-1
-2
0.4
0.3
0.2
=17°
IP=25%
=0.11
0.1
-3
0.0
-4
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
0.0
0.1
0.2
0.3
0.4
0.5
0.20
0.25
0.35
3
Patient #9
Patient #9
0.30
2
0.25
Vrc,p (liters)
flow (L/sec)
1
0
-1
0.20
0.15
0.10
0.05
-2
=58°
IP=31%
=0.13
0.00
-3
2
1
0
-1
-0.05
-0.05
volume (liters from resting EELV)
0.00
0.05
0.10
0.15
Vrc,a (liters)
13
Figure E4-b
3
0.6
Patient #11
Patient #11
0.5
2
quiet breathing
0.4
Vrc,p (liters)
flow (L/sec)
1
0
-1
exercise
0.3
quiet breathing
0.2
0.1
=27°
IP=41%
=0.11
-2
0.0
exercise
-3
2
1
0
-0.1
-0.04-0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16
0.30
-1
3
Patient #14
Patient #14
=44°
IP=29%
=0.22
0.25
2
Vrc,p (liters)
flow (L/sec)
0.20
1
0
0.15
0.10
0.05
-1
0.00
-0.05
-0.1
1.0
-2
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
3
0.1
0.2
0.3
0.4
0.5
Patient #18
Patient #18
2
0.8
Vrc,p (liters)
1
flow (L/sec)
0.0
0
0.6
0.4
-1
 =33°
IP=23%
=0.21
0.2
-2
0.0
-3
2.0
1.5
1.0
0.5
0.0
-0.1
0.8
-0.5
6
0.1
0.2
0.3
0.4
0.2
0.4
Vrc,a (liters)
0.6
0.8
Patient #19
Patient #19
4
0.6
Vrc,p (liters)
2
flow (L/sec)
0.0
0
0.4
=36°
IP=22%
=0.22
0.2
-2
0.0
-4
-0.2
-0.2
-6
3
2
1
0
-1
-2
volume (liters from resting EELV)
14
0.0
Figure E4-c
1.2
4
Patient #1
Patient #1
0.8
2
Vrc,p (liters)
quiet breathing
flow (L/sec)
exercise
1.0
3
1
0
-1
quiet breathing
0.6
0.4
0.2
-2
=11°
IP=29%
=0.13
0.0
exercise
-3
3
2
1
0
-1
-2
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.20
2.0
Patient #2
Patient #2
1.5
0.15
Vrc,p (liters)
flow (L/sec)
1.0
0.5
0.0
-0.5
0.10
0.05
0.00
=10°
IP=5%
=0.04
-1.0
-0.05
-1.5
-0.10
-0.1
-2.0
2
1
0
-1
4
0.0
0.1
0.2
0.3
0.4
0.5
0.20
Patient #5
Patient #5
3
0.15
Vrc,p (liters)
flow (L/sec)
2
1
0
0.10
0.05
-1
=7°
IP=17%
=0.01
0.00
-2
-3
1.5
1.0
0.5
0.0
-0.5
-1.0
-0.05
-0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12
-1.5
Patient #6
Patient #6
2
0.4
1
0.3
Vrc,p (liters)
flow (L/sec)
0.14
0.5
3
0
-1
0.2
0.1
=8°
IP=6%
=0.04
0.0
-2
-0.1
-0.05
-3
2
1
0
-1
volume (liters from resting EELV)
15
0.00
0.05
0.10 0.15 0.20
Vrc,a (liters)
0.25
0.30
Figure E4-d
0.4
3
Patient #7
Patient #7
2
quiet breathing
0.3
Vrc,p (liters)
flow (L/sec)
1
0
-1
-2
quiet breathing
exercise
0.2
0.1
-3
=18°
IP=17%
=0.17
0.0
-4
exercise
-0.1
-0.1
-5
3
2
1
0
-1
-2
6
0.6
Patient #10
0.0
0.1
0.2
0.3
0.4
0.5
Patient #10
0.5
4
0.4
Vrc,p (liters)
flow (L/sec)
2
0
-2
=8°
IP=5%
=0.12
0.3
0.2
0.1
0.0
-4
-0.1
-6
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
-0.2
-0.05
-1.0
4
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.5
Patient #12
Patient #12
3
0.4
Vrc,p (liters)
flow (L/sec)
2
1
0
-1
0.3
0.2
0.1
-2
=18°
IP=15%
=0.04
0.0
-3
-4
2
1
0
-0.1
-1
0.00
4
0.05
0.10
0.15
0.20
0.25
0.4
Patient #13
Patient #13
3
0.3
Vrc,p (liters)
flow (L/sec)
2
1
0
0.2
0.1
-1
=5°
IP=17%
=0.03
0.0
-2
-3
2.0
1.5
1.0
0.5
0.0
-0.5
volume (liters from resting EELV)
-1.0
-0.1
16
0.0
0.1
0.2
0.3
Vrc,a (liters)
0.4
0.5
0.6
Figure E4-e
4
0.5
Patient #15
Patient #15
3
0.4
quiet breathing
quiet breathing
Vrc,p (liters)
flow (L/sec)
2
1
0
0.3
0.2
exercise
0.1
-1
=10°
IP=2%
=0.08
0.0
-2
exercise
-3
-0.1
-3
-2
-1
0
1
2
0.0
3
0.2
0.3
0.4
0.5
0.6
Patient #16
2
0.4
1
0.3
Vrc,p (liters)
flow (L/sec)
Patient #16
0
-1
-2
0.2
0.1
=28°
IP=14%
=0.06
0.0
-3
2
1
0
-0.1
-0.04
1.2
-1
3
Patient #17
0.00
0.04
0.08
0.12
0.16
0.20
Patient #17
1.0
2
0.8
Vrc,p (liters)
1
flow (L/sec)
0.1
0.5
0
-1
0.6
0.4
0.2
-2
-3
3
2
1
0
-1
-0.2
-0.2
-2
4
0.5
Patient #20
0.0
Vrc,p (liters)
0
-2
0.4
0.6
0.8
0.3
0.2
0.1
=11°
IP=15%
=0.09
-4
0.0
-6
-3.0
0.2
Patient #20
0.4
2
flow (L/sec)
=15°
IP=14%
=0.08
0.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
-0.1
-0.1
0.5
volume (liters from resting EELV)
17
0.0
0.1
0.2
0.3
0.4
Vrc,a (liters)
0.5
0.6
0.7
Figure E5-a
Patient #3
Volume change (L)
1.0
0.8
0.4
0.6
0.3
0.4
0.2
0.2
0.1
0.0
0.0
-0.2
-0.1
0.8
0.5
1.0
1.5
2.0
2.5
3.0
Patient #4
1
2
3
4
1
2
3
4
Patient #14
0.4
0.6
0.3
0.4
0.2
0.2
0.1
0.0
0.0
-0.1
0
0.7
Volume change (L)
0
0.5
-0.2
1
2
3
4
5
6
7
0
1.0
Patient #8
0.6
Patient #18
0.8
0.5
0.6
0.4
0.3
0.4
0.2
0.2
0.1
0.0
0.0
-0.1
-0.2
0.0
0.35
Volume change (L)
Patient #11
0.5
0.0
Volume change (L)
0.6
0.5
1.0
1.5
2.0
2.5
0.0
0.8
Patient #9
0.5
1.0
1.5
2.0
2.5
Patient #19
0.30
0.6
0.25
0.20
0.4
0.15
0.2
0.10
0.05
0.0
0.00
-0.05
-0.2
0
1
2
3
4
0.0
0.5
time (sec)
1.0
1.5
time (sec)
Vrc,p (quiet breathing)
Vrc,a (quiet breathing)
Vrc,p (exercise)
Vrc,a (exercise)
18
2.0
2.5
3.0
Figure E5-b
Patient #1
Volume change (L)
1.2
0.5
1.0
Patient #7
0.4
0.8
0.3
0.6
0.2
0.4
0.1
0.2
0.0
0.0
-0.1
0
Volume change (L)
0.5
1
2
3
4
5
6
Patient #2
0.6
0.4
2
3
4
Patient #10
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0.0
0.0
-0.1
-0.2
0.0
0.20
Volume change (L)
1
0.5
-0.1
0.5
1.0
1.5
2.0
2.5
3.0
0
0.5
Patient #5
1
2
3
4
5
6
Patient #12
0.4
0.15
0.3
0.10
0.2
0.05
0.1
0.00
0.0
-0.05
-0.1
0.0
0.5
Volume change (L)
0
0.5
1.0
1.5
2.0
2.5
3.0
0.0
0.6
Patient #6
0.5
1.0
1.5
2.0
2.5
Patient #13
0.5
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0.0
0.0
-0.1
-0.1
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.0
0.5
time (sec)
1.0
1.5
time (sec)
Vrc,p (quiet breathing)
Vrc,a (quiet breathing)
Vrc,p (exercise)
Vrc,a (exercise)
19
2.0
2.5
3.0
Figure E5-c
Volume change (L)
Patient #15
0.6
1.2
0.5
1.0
0.4
0.8
0.3
0.6
0.2
0.4
0.1
0.2
0.0
0.0
-0.1
Patient #17
-0.2
0
1
2
3
4
5
6
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
Patient #16
Volume change (L)
0.5
0.7
Patient #20
0.6
0.4
0.5
0.3
0.4
0.2
0.3
0.2
0.1
0.1
0.0
0.0
-0.1
-0.1
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0
1
2
3
time (sec)
Vrc,p (quiet breathing)
Vrc,a (quiet breathing)
Vrc,p (exercise)
Vrc,a (exercise)
20
4
5