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Original research article

Diaphragm dome height in chest X-ray as apredictor of dynamic lung hyperinflation in COPD
Masashi Shiraishi, Yuji Higashimoto, Ryuji Sugiya, Hiroki Mizusawa, Yu Takeda, Masaya Noguchi,
Osamu Nishiyama, Ryo Yamazaki, Shintarou Kudo, Tamotsu Kimura, Yuji Tohda, Hisako Matsumoto

Please cite this article as: Shiraishi M, Higashimoto Y, Sugiya R, et al. Diaphragm dome heightin chest X-ray as a predictor of dynamic lung hyperinflation in COPD. ERJ Open Res 2023; inpress (https://doi.org/10.1183/23120541.00079-2023).

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Unmarked manuscript

TITLE:

Diaphragm dome height in chest X-ray as a predictor of dynamic lung hyperinflation in
COPD
Authors’ full names:
Masashi Shiraishi,1 Yuji Higashimoto,1 Ryuji Sugiya,1 Hiroki Mizusawa,1 Yu Takeda,1Masaya Noguchi,1 Osamu Nishiyama,2 Ryo yamazaki,2 Shintarou Kudo,3 Tamotsu Kimura,1Yuji Tohda,2 Hisako Matsumoto2
Authors’ affiliation(s):Department of Rehabilitation Medicine, Kindai University School of Medicine, Osaka, Japan(1)
Department of Respiratory Medicine and Allergology, Kindai University School of Medicine,
Osaka, Japan (2)Inclusive Medical Science Research Institute, Morinomiya University of Medical Sciences,
Osaka, Japan (3)Corresponding author details:
Name: Masashi Shiraishi
Email: masashi-shiraishi@med.kindai.ac.jp

Summary of take-home message
Diaphragm dome height on chest X-ray, a basic and inexpensive measure, is a good predictorof high dynamic hyperinflation in COPD, independent of the low attenuation area on chest
computed tomography and %FEV1.

Abstract
Background and objective: Dynamic lung hyperinflation (DLH) can play a central role inexertional dyspnoea in patients with chronic obstructive pulmonary disease (COPD). Chest
X-ray is the basic tool for assessing static lung hyperinflation in COPD. However, thepredictive capacity of DLH using chest X-ray remains unknown. This study was conducted todetermine whether DLH can be predicted by measuring the height of the right diaphragm(dome height) on chest X-ray.
Methods: This single-centre, retrospective cohort study included patients with stable COPD
with pulmonary function test, cardiopulmonary exercise test, constant load test, andpulmonary images. They were divided into two groups according to the median of changes ofinspiratory capacity (∆IC = IC lowest − IC at rest). The right diaphragm dome height andlung height were measured on plain chest X‐ray.
Results: Of the 48 patients included, 24 were classified as having high DLH (ΔIC ≤ −0.59 Lfrom rest; −0.59 L, median of all) and 24 as having low DLH. Dome height correlated withΔIC (r = 0.66, p < 0.001). Multivariate analysis revealed that dome height was associatedwith high DLH independent of %low attenuation area on chest computed tomography
and %FEV1. Furthermore, the area under the receiver operating characteristic curve of domeheight to predict high DLH was 0.86, with sensitivity and specificity of 83% and 75%,
respectively, at a cutoff of 20.5 mm. Lung height was unrelated to ΔIC.
Conclusion: Diaphragm dome height on chest X-ray may adequately predict high DLH inpatients with COPD.

Short title:
Diaphragm dome height on X-ray and DLH

Keywords: dynamic lung hyperinflation, COPD, plain chest X-ray, diaphragm

Conference presentation: none in the International ConferenceIntroduction
Chronic obstructive pulmonary disease (COPD) is a progressive disorder characterisedby minimally reversible airflow limitation.[1] Its primary feature is the inability to cope withactivities of daily living due to exertional dyspnoea. Although the pathophysiologicalmechanisms involved in dyspnoea development and poor exercise tolerance in patients with
COPD are complex, dynamic lung hyperinflation (DLH) can play a central role[2] byincreasing ventilatory workload and decreasing the pressure-generating capacity of theinspiratory muscles despite the compensatory mechanisms.[3] Therefore, DLH evaluation isimportant in COPD management.
In patients with COPD, the diaphragm, which is the main muscle employed forrespiration, significantly changes in terms of mass, thickness, and area, and its mobility is
associated with DLH. We previously reported that increased dyspnoea caused by DLH on
exercise is associated with decreased exercise capacity in patients with COPD and reduced
diaphragm mobility, which was assessed by the maximum level of diaphragm excursion(DEmax) using ultrasonography.[4] Other research groups also reported that ultrasonographic
assessment of diaphragmatic mobility in COPD is useful in understanding its association with
6-minute walk distance, dyspnoea,[5] and increased mortality.[6]Given that a plain chest X-ray is readily available and inexpensive, it is a quick andbasic diagnostic tool for evaluating patients’ lungs. Chest X-ray is essential in COPD
management; thus, most of the patients with COPD undergo this diagnostic examination. The
applied radiation dose is relatively low, with an average effective dose of 0.05 mSv for asingle posterior–anterior image.[7, 8] Chest X-ray also provides information on physiologicalchanges in COPD. On a frontal chest radiograph, the normal dome of each hemidiaphragmshould rise at least 15 mm above a line connecting the costophrenic angle laterally andcardiophrenic angle medially.[8, 9] Meanwhile, in lung hyperinflation, the diaphragm isflattened, generally because of emphysema, which is one of the most sensitive signs on chest
radiographs.[10, 11] However, the relationship between plain chest X-ray measurements ofthe diaphragm and DLH remains unreported.
Thus, this study aimed to determine the predictive capacity of DLH according to domeheight on chest X-ray. We hypothesized that measuring the dome height is useful in assessing
DLH in patients with COPD, reflecting diaphragmatic mobility.

Methods
Study design and subjects
This was a single-centre, retrospective cohort study. The participants had clinicallystable COPD, who visited the Department of Respiratory Medicine and Allergology at Kindai
University Hospital between January 2018 and November 2022. We included patients who
received the cardiopulmonary exercise test (CPET) and the following examinations andmeasurements within 3 months before and after CPET: (1) ultrasonographic measurement of
maximum diaphragmatic excursion, (2) spirometry, (3) DLH finding by constant load test,(4) chest X-ray, and (5) computed tomography (CT). The exclusion criteria were unclear
diaphragm angle on radiographic images caused by pleural effusion or adhesions,diaphragmatic eventration, phrenic nerve palsy, and post lung surgery. This study included
our previously reported 46 participants and an additional 20 participants. All participants
were those whose attending physicians considered outpatient rehabilitation necessary inactual clinical practice and who had no problems with time constraint or accessibility.[4] [12]Measurements
Symptom-limited cardiopulmonary exercise test (CPET) was conducted on a bicycle
ergometer according to the Ramp 10 W protocol (load increase of 10 watts per 1 minute −1．
watt per 6 seconds). We analysed the following: peak oxygen consumption (peak VO2) and． ．
ventilation equivalents for carbon dioxide (VE/VCO2). Inspiratory capacity (IC) manoeuvres
were performed at rest, and during constant load exercise (peak 70%). Throughout exercise
testing, IC was measured every 1 min and at the end of the exercise.
We measured the change in IC (∆IC = IC lowest − IC at rest) during exercise as asurrogate marker of DLH.[13, 14] Using the data obtained from the exercise test, we divided
the patients into two groups according to the median ΔIC: low DLH group and high DLHgroup.
Lung hyperinflation was evaluated by plain chest X-ray as follows: (a) the dome heightof the right and left diaphragm was assessed by drawing a line from costophrenic angles tocardiophrenic angles and measuring the longest line perpendicular to the diaphragmsilhouette (Figure 1a); and (b) lung height was measured as the distance from the top of theright and left diaphragm dome to the tubercle of the first rib (lung height) (Figure 1b).[9, 15]
Drawing lines and measuring the distance were performed using Synapse (Fujifilm Medical).
Moreover, emphysema was quantified by calculating the percentage of the low attenuationarea, determined according to the cutoff value of −950 HU on whole-lung computed

tomographic images (Aquilion 64 scanner; Toshiba, Tokyo, Japan) using Synapse Vincent(Fujifilm Medical), as described previously.[16, 17]
We also measured DEmax through ultrasonography (Xario 200; Canon Medical Systems,
Tokyo, Japan). Excursions of the right hemidiaphragm were measured using a 3.5-MHz
convex probe according to previously described techniques.[4] The liver was used as anacoustic window. We rotated the M-mode cursor was rotated placed it on the axis ofdiaphragmatic displacement on the stored image, measured the displacement (Figure S1)during each of three deep breaths, and then measured the DEmax.
Patients underwent spirometry (CHESTAC-800; Chest, Tokyo, Japan) according to the2014 American Thoracic Society recommendations [18] for measuring forced vital capacity(FVC), forced expiratory volume in one second (FEV1), and IC. FEV1% predicted and FVC%
predicted were calculated using the Global Lung Function Initiative (GLI) method that wasrecommended by the 2022 European Respiratory Society/American Thoracic Society
technical standard [19] and had been used in the Japanese Respiratory Society to calculate
reference values for spirometry. [20]To assess respiratory muscle strength, we measured the maximum inspiratory pressure(PImax) generated against an occluded airway at residual volume[21] (IOP-01; Kobata
Instrument Manufacturing Ltd., Osaka, Japan).
The ethics committee of Kindai University School of Medicine approved this study(approval No.: R04-192). Informed consent was obtained from each patient by using an
opt-out approach in agreement with the institutional review board.
Sample size
The sample size was estimated using the R software. The inclusion of 40 patients was
required if the expected area under the curve (AUC) of the receiver operating characteristic(ROC) was 0.80, the power was 90%, and the significance level was 0.01.
Statistical analysis
Continuous data are expressed as mean ± standard deviation or median and interquartile
range (IQR) for parametric and nonparametric values. The high DLH and low DLH groups
were compared using the t-test, Wilcoxon rank-sum test (%LAA and IC), or χ2 test (GOLDstage), as appropriate.
The ROC curve method was used to determine the ability of dome height to predict thepresence of high DLH. The ability of variables to predict ΔIC was also evaluated using themultivariate logistic regression model, which included height, age, and sex as covariates.
Given that ΔIC and dome height were normally distributed, the association between
independent variables and ΔIC or dome height was analysed using the Pearson correlation
coefficient. Univariate linear regression was included with ΔIC as the dependent variable andright dome height as the independent variable. Statistical data were analysed using the IBM
SPSS statistics software, version 22 (IBM SPSS, Armonk, NY, USA), and JMP software,version 14 (JMP®, SAS Institute Inc., Cary, NC, USA). A p value < 0.05 was considered
statistically significant.

Results
Out of 66 enrolled patients with COPD, 48 were eligible for the analysis (Figure 2). We
excluded 18 patients because of pleural effusion in 2, pleural adhesions in 2, post lungsurgery in 2, and incomplete data in 12 patients. Incomplete data (n = 12) included four caseswith chest X-ray images that were taken more than 3 months after CPET, four cases without
chest CT images, and four cases without DLH measurements.
Table 1 presents the participants’ baseline characteristics. The ΔIC values were varied
from −0.12 L to −1.50 L, and the median was −0.59 L. Furthermore, 24 patients wereclassified as the high DLH group (ΔIC from rest ≤ −0.59 L), and 24 as the low DLH group(ΔIC from rest > −0.59 L). Body mass index (BMI), PImax, GOLD stage, DEmax, diaphragm．
dome height, FEV1, FEV1% predicted, and peak VO2 were significantly lower,． ．
whereas %LAA and VE/VCO2 were higher in the high DLH group than in the low DLH
group (Table 1). Lung height showed no difference between groups.
The ΔIC positively correlated with BMI, PImax, DEmax, right dome height (Figure 3),．
and left dome height, FEV1% predicted, and peak VO2 and negatively correlated with %LAA
． ．
and VE/VCO2 (Table 2). The correlation between ΔIC and right dome height was stronger
than that between ΔIC and left dome height (Table 2). Univariate linear regression was
performed with delta IC as the dependent variable and dome height as the independent
variable, and the results were R2 = 0.44, β = 0.66, 95% CI = 0.022–0.045, and p < 0.001. The
right dome height positively correlated with BMI, QMS, PImax, DEmax, IC, FEV1, FEV1%．
． ．
predicted, FVC, and peak VO2 and negatively correlated with VE/VCO2 (Table 3). The
association between ΔIC and right dome height remained significant, even when analysed by
COPD subtype (GOLD 2, n = 19, r = 0.64, p = 0.003, GOLD 3, n = 19, r = 0.53, p = 0.019).
Regarding GOLD 1 and 4, they also showed moderate-to-strong correlation, but they did notmeet the 5% significance level due to the small sample size, i.e., each with five cases (GOLD1, r = 0.86, p = 0.062 ; GOLD 4, r = 0.62, p = 0.27).
The area under the ROC curve of dome height for predicting high DLH was 0.86, witha sensitivity of 83% and a specificity of 75% at a cutoff value of 20.5 mm (Figure 4).
In the multivariate analysis, high DLH (ΔIC from rest ≤−0.59L) was the dependent
variable, and dome height, %LAA, and FEV1% predicted were the independent variables;
variables %LAA and %FEV1 were considered clinically important. The right dome heightand %LAA were found to be the significant independent explanatory variables, with rightdome height being the most significant independent explanatory variable (odds ratio, 0.67;
95% confidence interval, 0.516–0.862, p = 0.002, Table 4).
Finally, we performed multivariate ROC curve analysis with high DLH (ΔIC ≤ −0.59L
from rest) as the dependent variable. Compared with models that included height as acovariate, the conformity as expressed as lower Akaike Information Criterion corrected forsmall samples (AICc) appeared to be the best for Model 3, i.e., a model without any
adjustment including height (Table S1).

Discussion
Airflow limitation and DLH can be major contributors to dyspnoea in patients with
COPD, and DLH is tightly linked to dyspnoea and exercise tolerance.[2] To our best
knowledge, this is the first study to demonstrate that dome height on plain chest X-ray was
useful for predicting ΔIC reflecting DLH in patients with COPD.
In this study, reduced dome height by plain chest X-ray was a better predictor of high
DLH than %LAA or %FEV1 in the multivariate analysis. In addition, dome height had highsensitivity (83%) and specificity (75%) at a cutoff value of 20.5 mm for predicting high DLH.
Although mechanisms underlying the association between reduced dome height and high
DLH during exercise remain unclear, they may be explained by the association between the
degree of hyperinflation at rest and the degree of DLH during exercise.[22] DLH consists ofstatic and dynamic components. The static component results from pulmonary parenchyma
destruction and elastic recoil loss by the lung. Even in the static phase, patients with COPD
have an elevated resting end-expiratory lung volume (EELV; total lung capacity [TLC]-IC)
caused by airway resistance increase resulting from airway inflammation and airway wall
thickening, and/or by lung elastic recoil reduction resulting from alveolar destruction andemphysema. The dynamic component occurs when patients with COPD breathe in before
achieving a complete exhalation, and EELV further increases in association with respiratory
rate elevations because it occurs during exercise.[23] Critical inspiratory constraint (CIC)

resulted in a plateau in tidal volume and an associated increase in dyspnoea as a function ofventilation volume, and CIC was useful in explaining the presence and severity of exertional
dyspnoea.[24-27] Although we did not have the data of IC/TLC that reflects static
hyperinflation, reduced dome height may reflect the degree of hyperinflation at rest.
Therefore, patients with reduced dome height, that is, diaphragm flattening, possibly had
higher resting EELV at rest, resulting in even higher dynamic EELV during exercise andmore high DLH.
Previous studies also investigated other possible biomarkers for DLH, includingexertional oxygen desaturation during 6-min-walk testing, [28] or even 8-isoprostane levels
in exhaled breath condensate.[29] However, the former is time-consuming and not always
implemented in the outpatient clinic. The latter needs specific equipment and cost comparedwith routine chest X-ray.
Emphysema, as evaluated by CT, is associated with shorter 6-min-walk distances, lower．
peak VO2, and lower exercise ventilation efficiency in patients with COPD.[30-33] CT is avalidated imaging technique used to visually and quantitatively assess the presence, extent,
and pattern of emphysema,[34] whereas plain chest X-ray has low sensitivity for detecting
emphysema.[35] Computed tomography emphysema and airway metrics [33] andhomogeneous and heterogeneous emphysema on CT [36] have been reported as markers of
DLH. However, currently chest CT is not considered a standard of care in the diagnosis andmanagement of mild-to-moderate COPD.[37] Furthermore, the use of CT is limited becauseof the high radiation exposure compared with plain chest X-ray.[7] In this study, %LAA
correlated with DLH but was only marginally as a predictor. One reason why dome height
was a better predictor than %LAA might be that CT is taken in the supine position, whereas
X-ray is taken in the same standing position as during exercise. Therefore, plain chest X-ray
evaluation of diaphragm height may be superior in DLH prediction when consideringcost-effectiveness and radiation exposure, and the prediction accuracy is higher than that byother methods.
Dome height by plain chest X-ray also correlated with DEmax measured byultrasonography that was strongly associated with DLH and dyspnoea during exercise, as wereported previously.[4] However, DEmax assessment has a limitation. The procedures
pertaining to patient positioning, breathing patterns, and the selected hemidiaphragm arecurrently not standardized, thereby likely hampering the routine use of DEmax. Therefore,
diaphragm evaluation by plain chest X-ray may be useful for facilities that cannot perform
ultrasonography and achieve equivalent results in DLH prediction.

This study has some limitations. It is a single-centre study involving a relatively small
sample size, and the patients’ baseline condition was relatively preserved. However, DLH
assessment is also warranted in patients with relatively preserved pulmonary function, giventhat proactive intervention may prevent deterioration of activities of daily living. In addition,owing to the retrospective nature of this study, we could not confirm if the chest X-ray was
obtained at the TLC level. However, in erect chest radiographs, individuals with normal
respiratory function routinely inhale to approximately 95% of TLC without vigorously
coaxing;[38] therefore, our study findings may be largely reliable. Finally, due to the small
sample size of mild (GOLD 1) and most severe (GOLD 4) cases, it is not clear whether this“biomarker” is clinically relevant in all severities of COPD. Further studies are required toincrease the number of cases so that subtyping can also be included. In conclusion, plain
chest X-ray measurements of the diaphragm dome height could adequately predict DLH inpatients with COPD. A plain chest X-ray is a rapid and basic diagnostic tool for evaluating
patients’ lungs. Measurement of plain chest X-ray is easy to perform, safe, and well tolerated
in patients with chronic lung disease. This ease of use makes the assessment of dome heightin this study a more feasible and attractive option in routine clinical practice. Therefore,
assessing the diaphragm dome height may aid in making medical decisions associated withtherapeutic strategies.

Acknowledgements: This work was supported by Grants-in-Aid for Scientific Research(22K17664).

Conflict of Interest: None declared

Data Availability Statement: The data supporting the findings of this study are available on
reasonable request from the corresponding author. The data are not publicly available due toprivacy or ethical restrictions.
Human/Animal Ethics Approval Declaration: This study was approved by the Ethics
Committee of Kindai University School of Medicine (R04-192).

Abbreviations: AUC: area under the curve, COPD: chronic obstructive pulmonary disease,
CPET: cardiopulmonary exercise test, DEmax: maximum level of diaphragm excursion, DLH:
dynamic lung hyperinflation, EELV: end-expiratory lung volume, FEV1: forced expiratory

volume in 1 s, FVC: forced vital capacity, IC: inspiratory capacity, %LAA: low attenuationarea, PImax: maximum inspiratory pressure, ROC: receiver operating characteristic, TLC:．
． ．
Total Lung Capacity,:, VO2: oxygen uptake, VE /VCO2: minute ventilation/carbon dioxide

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Table 1. Baseline characteristics of study participantsHigh DLH

Low DLH(ΔIC ≤ -0.59 L)(ΔIC > -0.59 L)

n＝48

n＝24

n＝24

Male/female, %44 / 4 (91 / 9)

20 / 4 (80 / 20)

24 / 0 (100 / 0)

0.68

Age, yr

75 ± 575 ± 6

76 ±5

0.24

Body mass index, kg/m2

21.4 ± 3.3

20.3 ± 3.1

22.4 ± 3.2< 0.05

Body height, cm

163.9 ± 6.9

161.9 ± 7.7

165.3 ± 5.5

0.08

QMS, Kgf/Kg

0.52 ± 0.13

0.52 ± 0.14

0.57 ± 0.16

0.36

PImax, cm H2O

54.4 ± 21.8

41.8 ± 15.0

67.0 ± 24.1

< 0.01%PImax, %80.3 ± 33.4

66.0 ± 26.0

94.7 ± 33.8

< 0.01

GOLD（1/2/3/4）

6 / 19 / 18 / 5

1/ 8 / 10 / 5

5 /11 / 8 / 0< 0.05‡%LAA

20.4 (2.05–37.1)

33.9 (11.1–39.3)

8.9 (1.2–25.0)< 0.01†

DEmax, mm

46.7 ± 8.6

40.5 ± 5.6

53.0 ± 6.2< 0.01

Right dome height, mm

21.2 ± 5.9

17.6 ± 5.2

24.7 ± 4.1< 0.01

Left dome height, mm

21.6 ± 6.1

20.0 ± 6.2

23.2 ± 5.5

0.07

Right lung height, mm

250.3 ± 27.3

256.5 ± 28.9

244.1 ± 23.9

0.14

Left lung height, mm

260.3 ± 41.7

270.2 ± 30.1

259.6 ± 20.2

0.17

ALL

p value*

Plain chest X-ray

Spirometry
IC, L

1.99 (1.61–2.43 ) 1.89 (1.42–2.17)

2.39 (1.70–2.50)< 0.01†

FEV1, L1.39 ± 0.55

1.14 ± 0.51

1.60 ± 0.50

< 0.01%predicted FEV1, %55.6 ± 22.0

47.0 ± 20.4

64.3 ± 20.1

< 0.01

FVC, L2.98 ± 0.72

2.83 ± 0.70

3.13 ± 0.68

0.23

%predicted FVC, %89.2 ± 18.4

87.7 ± 17.2

90.8 ± 19.4

0.58

Peak exercise measurements．
peak VO2, ml/min/kg． ．
VE/ VCO2, ml/ml

11.6 ± 3.5

9.0 ± 2.3

14.2 ± 2.3< 0.01

48.6 ± 7.3

52.1 ± 7.1

45.2 ± 5.6< 0.01ΔIC from rest, L-0.57 ± 0.30

-0.81 ± 0.21

-0.33 ± 0.15

< 0.01

Values are presented as mean ± standard deviation or median (interquartile). DEmax =maximum diaphragmatic excursion; DLH = dynamic lung hyperinflation; FEV1 = forced
expiratory volume in 1 s; FVC = forced vital capacity; GOLD = Global Initiative for Chronic

Obstructive Lung Disease; IC = inspiratory capacity; ΔIC = change of IC from rest during
exercise; LAA = low attenuation area; PImax = maximum inspiratory pressure; QMS =． ．
．
quadriceps muscle strength; VE/ VCO2 = minute ventilation/carbon dioxide; VO2 = oxygen
uptake. * = t-test, unless otherwise stated. †= Wilcoxon rank-sum test, ‡ = χ2

Table 2. Correlation coefficients for ΔIC
Total patients (n = 48)
Independent variable

Pearson correlation
p valuecoefficient (r)Age, yr

0.12

0.43

Body mass index, kg/m2

0.31< 0.05

Quadriceps muscle strength, Kgf/Kg

0.23

0.13

PImax, cm H2O

0.58< 0.001%PImax, %

0.24

0.95

%LAA, %

-0.34

< 0.05

DEmax, mm0.75< 0.001

Right dome height, mm

0.66< 0.001

Left dome height, mm0.38< 0.01

Right lung height, mm

0.21

0.16

Left lung height, mm

0.16

0.28

FEV1 %predicted

0.43< 0.010.81< 0.001-0.44< 0.01．
peak VO2, ml/min/kg． ．
VE/ VCO2, ml/ml

DEmax = maximum diaphragmatic excursion; FEV1 = forced expiratory volume in 1 s; ΔIC =change of inspiratory capacity from rest during exercise; LAA = low attenuation area; PImax:． ．
．
maximum inspiratory pressure; VE/ VCO2 = minute ventilation/carbon dioxide; VO2 =oxygen uptake.

Table 3. Correlation coefficients for dome height
Total patients (n = 48)
Independent variable

Pearson correlation

p valuecoefficient (r)Age, yr

0.10

0.43

Body mass index, kg/m2

0.32< 0.01

Quadriceps muscle strength, Kgf/Kg

0.32< 0.05

PImax, cm H2O

0.53< 0.01%PImax, %0.49< 0.01%LAA, %

-0.19

0.18

DEmax, mm0.65< 0.001

IC, L

0.32

< 0.05

ΔIC, L

0.66< 0.001

FEV1, L0.44

< 0.01%predicted FEV1, %0.34< 0.05

FVC, L

0.40< 0.01%predicted FVC, %

0.18

0.22

0.63

< 0.01-0.32< 0.05．
peak VO2, ml/min/kg． ．
VE/ VCO2, ml/ml

DEmax = maximum diaphragmatic excursion; FEV1 = forced expiratory volume in 1 s; ΔIC =change of inspiratory capacity from rest during exercise; LAA = low attenuation area; PImax:． ．
．
maximum inspiratory pressure; VE/ VCO2 = minute ventilation/carbon dioxide; VO2 =oxygen uptake.

Table 4. Multivariate analysis for high DLH (ΔIC from rest ≤ -0.59 L)

Index

Odd ratios

95%CI

p value

Right dome height, mm

0.67

0.516–0.862

0.002%LAA, %

0.59

1.002–1.123

0.044%predicted FEV1, %0.97

0.929–1.012

0.161

DLH = dynamic lung hyperinflation; FEV1 = forced expiratory volume in 1 s; ΔIC = change
of inspiratory capacity from rest during exercise; LAA: low attenuation area;.

Figure legends

Figure 1.
Illustrative example demonstrating the measurement of diaphragm dome height (a) andlung height (b).

Figure 2.
Flow diagram of study participants.

Figure 3.
Correlation between ΔIC and dome height of the right diaphragm: r = 0.66, p < 0.001 in
all patients (n = 48); r = 0.86, p = 0.062 in GOLD 1 (n = 5); r = 0.64, p = 0.003 in
GOLD 2 (n = 19); r = 0.53, p = 0.019 in GOLD 3 (n = 19); r = 0.62, p = 0.27 in GOLD
4 (n = 5).

Figure 4.
Receiver operating characteristic (ROC) curve of the dome height of the right
diaphragm measured by plain chest X-ray: The area under the ROC curve of domeheight to predict high DLH was 0.86, with a sensitivity of 83% and a specificity of 75%
at a cutoff value of 20.5 mm of dome height.

Figure 1 (a)Figure 1 (b)Figure 2

Eligible subjects(n = 66)

Excluded from the study (n = 18)••••

Pleural effusion (n = 2)
Pleural adhesions (n = 2)
Post-lung surgery(n = 2)
Incomplete data (n = 12)

Included subjects (n = 48)

Severe DLH (n = 24)

Mild DLH (n = 24)

ΔIC ≤ -0.59L

ΔIC > -0.59L

Figure 3
0
-0.2
-0.4

Δ IC (L)

-0.6

-0.8
-1
-1.2
-1.4
-1.6

0

10

20

Dome height, mm

30

40

Figure 4

Sensitivity

ROC curve

1-Specificity

SUPPLEMENTARY INFORMATION
Diaphragm dome height in chest X-ray as a predictor of dynamic lung hyperinflation in COPD

Masashi Shiraishi,1 Yuji Higashimoto,1 Ryuji Sugiya,1 Hiroki Mizusawa,1 Yu Takeda,1 Masaya Noguchi,1 Osamu Nishiyama,2 Ryoyamazaki,2 Shintarou Kudo,3 Tamotsu Kimura,1 Yuji Tohda,2 Hisako Matsumoto2

1

Department of Rehabilitation Medicine, Kindai University School of Medicine, Osaka, Japan2

Department of Respiratory Medicine and Allergology, Kindai University School of Medicine, Osaka, Japan3

Inclusive Medical Science Research Institute, Morinomiya University of Medical Sciences, Osaka, Japan

Figure S1: Representative image of the right diaphragm.
Table S1: Multivariate ROC curve analysis with three models.

Figure S1: Representative image of the right diaphragm.

TableS1. Multivariate ROC curve analysis with three models.

Model 1AICc

AUC

p value

Model 2AICc

AUC

p value

Model 3AICc

AUC

p value

Right dome height

48.8

0.858

＜0.001 Right dome height

50.9

0.859

＜0.001 Right dome height

54.5

0.859

＜0.001Height

0.914

Age

0.567

Sex

0.999

HeightAICc = Akaike Information Criterion corrected, AUC = Area under the curve

0.756