Objectives: To identify the correlation between the severity of emphysema on chest CT with clinical characteristics, FEV1 and chest X-ray in stable COPD patients. Subjects: 112 COPD patients in stable stage, managed at the Respiratory Consultation Unit of Cantho Central Hospital.
Trang 1THE CORRELATION BETWEEN EMPHYSEMA’S SEVERITY ON THE CHEST COMPUTED TOMOGRAPHY AND CLINICAL
WITH STABLE COPD
Cao Thi My Thuy*; Dong Khac Hung**; Nguyen Van Thanh*
SUMMARY
Objectives: To identify the correlation between the severity of emphysema on chest CT with clinical characteristics, FEV 1 and chest X-ray in stable COPD patients Subjects: 112 COPD patients in stable stage, managed at the Respiratory Consultation Unit of Cantho Central Hospital Study design: Descriptive cross-sectional study based on the percentage of low attenuation area less than the threshold - 950 Hounsfield Unit (%LAA ≤ 950 HU) on high resolution computed topography (HRCT) in order to identify the severity of emphysema The clinical characteristics were selected as well as frontal and lateral chest X-ray, lung function test, classification COPD into groups A - D from GOLD 2017 Results: The severity of emphysema
on chest CT is direct correlation with MRC scales (PCC = 0.389, p = 0.0001) and CAT (PCC = 0.268, p = 0.004), but inversely correlation to the value of FEV 1 after bronchodilation (PCC= -0.278, p = 0.003) The results from emphysema evaluated on chest X-ray and
%LAA ≤ 950 HU were correlated (PCC: 0.22, p: 0.018) Conclusions: The severity of emphysema
leads to cause the airway limitation in COPD Chest X-ray has still the role for emphysema’s
diagnosis The severity of emphysema correlates with dyspnea degrees and poor health status
* Keywords: Stable chronic obstructive pulmonary disease; Emphysema; Chest CT; Clinical characteristics
INTRODUCTION
Chronic obstructive pulmonary disease
(COPD) is a disease characterized by
incompletely reversible airway limitation
That consequence results from the increase
in airway resistance due to small airway
obstruction and loss of lung elastic recoil
due to emphysema The lung function
testing only helps to confirm the airway
limitation, but not to identify the pathological
changes as well as not to reflect all of
clinical characteristics of the COPD patients
[9] Unlike previous versions, GOLD 2017 classifies the patients with the groups A - D, that do not depend on results of lung
function [9]
Computed topography (CT), especially the HRCT and multislide computed topography is the most accurate imaging method for detection and classification of emphysema’s severity The way how to identify and classify the emphysema’s severity on CT could be qualilative and quantitative The quantitative method could
* Cantho Central Hospital
** Vietnam Military Medical University
Corresponding author: Cao Thi My Thuy (bscaothimythuy@gmail.com)
Date received: 20/08/2017
Date accepted: 28/09/2017
Trang 2identify the correlation with damaging
histology by emphysema Applying imaging
techniques for phenotype of COPD
classification is likely to help us to understand
more about the heterogeneity of COPD,
to make a better prognosis and an appropriate
approach in treatment In Vietnam, there
have been a few studies about imaging
characteristics regarding chest of COPD
patients and also have no consistent
conclusions about the correlation between
the emphysema’s severity and ventilatory
lung function [1, 2]
The aim of this study is: To identify the
correlation between the emphysema’s
severity classified by chest CT with
X-ray of patients with stable COPD
SUBJECTS AND METHODS
1 Subjects
The study was carried out on 112 patients
with stable COPD, managed in the
Respiratory Consultation Unit of Cantho
Central Hospital The criteria of COPD
diagnosis are based on GOLD 2017
guidelines [9] The patients with diagnosis
of asthma, tuberculosis, lung tumor,
bronchiectasis, previous chest operation,
pneumothorax, without permission to
perform spirometry, without agreement to
participate in the study were excluded
2 Method
- Study design: Descriptive cross-sectional
study
- Variables selected such as age,
gender, smoking status (packs-year),
number of exacerbation during the last 12
previous months, BMI, cough, expectoration,
chronic dyspnea on exertion, degree of
dyspnea based on MRC, scales, assessment
of COPD test (ACT), classification COPD into groups A - D from GOLD 2107 [9]
- Lung function testing: Patients were measured their lung function apart from exacerbation, by using KoKo - Spirometer (nSpire Health, USA) They were performed spirometry before and 15 minutes after bronchodilation test with salbutamol 400 µg (ventolin) through spacer The measurement techinique followed ATS/ERS standards [5] Diagnosis of COPD is confirmed when the ratio FEV1/FVC < 0.7 after bronchodilation use The severity of airway obstruction is based on GOLD 2017, by the value of % FEV1 predicted after bronchodilation [9]
- Chest X-ray: All of the patients were performed frontal and lateral chest X-ray
by the digital machine (Quantum, USA) The results were interpreted as existing emphysema, no emphysema and unidentifiable The analysis was taken from the cases with emphysema or not The unclear cases were classified in the unidentified group The criteria for emphysema should meet at least 2 among 4 points below [8]: On the frontal chest X-ray: diaphragm is flat and low: the distance from the highest point of diaphragm outline to the line between cardio phrenic angle and costo phrenic angle < 1.5 cm; heterogious lucency in two lung fields On the lateral chest X-ray: increased retrosternal space: measurement from the sternum to the anterior margin of ascending aorta
≥ 2.5 cm; flattening of diaphragm: sterno phrenic angle ≥ 900
- Chest HRCT procedure: GE 64 slices scanner machine (USA) was used with the thickness of slide about 0.625 mm,
Trang 3permeability: 120 kV, mA = 600 Patients
were taken the chest HRCT in inspiration
without contrast The percentage of low
attenuation area that was less than the
threshold - 950 HU Hounsfield unit (%LAA
≤ 950 HU) to identity the severity of emphysema based on Rutten EP criteria [7]
RESULTS
1 Patient’s characteristics
There were 112 patients recruited for the study Population characteristics (gender, age) and clinical manifestations were presented in the table 1
Table 1: Patients’s characteristics
Patient’s characteristics Results (n, %)
Gender (n, %):
Male
Female
110 (98,2)
2 (1,8)
Respiratory symptoms (n, %)
Cough and/or chronic expectoration
Chronic dyspnea
Cough, expectoration and chronic dyspnea
5 (4,5)
15 (13,4)
92 (82,1)
Classification GOLD into groups (A, B, C, D) (n, %)
Group A
Group B
Group C
Group D
14 (12,5)
25 (22,3)
26 (23,2)
47 (43,0) Severity of airway limitation (n, %)
GOLD 1
GOLD 2
GOLD 3
GOLD 4
14 (12,5)
57 (50,9)
35 (31,2)
6 (5,4) Emphesema’s severity on the chest CT (%LAA ≤ 950 HU) (n, %)
No emphesema
Minor
Moderate
Severe
48 (42,9)
60 (53,6)
4 (3,6)
0
(Abbreviations: SD: Standard deviation; BMI: Body mass index); MRC: Medical research council; CAT: COPD assssment test; %LAA: % low attenuation area)
Trang 42 Correlation between %LAA ≤ 950 HU and respiratory symptoms, multiple exacerbation, BMI, MRC scales, CAT score and classification groups A - D
The results from analyzing the correlation between the severity of emphysema and clinical respiratory symptoms, multiple exacerbation, BMI, MRC scales, CAT score,
classification groups A - D had shown in table 2
Table 2: The correlation between %LAA ≤ 950 HU with clinical respiratory signs,
multiexacerbation characteristics of MRC scales, CAT scores, A - D groups classification
Compared
variables
Clinical respiratory signs
Multiexacerbation MRC
scales
CAT score
BMI A - D
groups
%LAA
≤ 950 HU
PCC
p value
-0,01
0.93
0,073
0.44
0,389 0.0001(*)
0,268 0.004(*)
-0.279 0.003(*)
0,019
p = 0.84
(*: significant correlation if < 0.01)
The value %LAA ≤ 950 HU has the direct correlation with MRC scale and CAT,
but inverse correlation with BMI (p < 0.01)
3 Results of emphysema in chest X-ray, %LAA ≤ 950 HU and their correlation
Results considered if there was an emphysema or not in conventional chest X-ray and the percentage of low attennuation area in chest CT (%LAA ≤ 950 HU) were presented
in table 3
Table 3: Results from evaluation of existing emphysema in conventional chest X-ray,
%LAA ≤ 950 HU and their correlation
Emphysema: 14 (13.5%) Not emphysema: 43 (38.4%)
Existing emphesema;
n (%)
Unidentifiable 55 (49.1%)
Minimal value: 0.1 Maximal value: 42.4
PCC: 0.22 p: 0.018 (*)
(* p < 0.05)
The result of analyzing this correlation is statistically significant with p < 0.05
Trang 54 Correlation between emphysema
evaluated on chest X-ray, percentage
of low attenuation area on chest CT
(%LAA) with value of %FEV 1 predicted
after bronchodilaton
Table 4: Correlation between emphysema
evaluated on chest Xray, %LAA ≤ 950 HU
and FEV1
FEV 1
Conventional chest
X ray
PCC (r)
p value
-0.043 0.650
%LAA ≤ 950 HU PCC (r)
p value
-0.278(**) 0.003
Graph 1: Correlation between the severity
of emphysema (%LAA ≤ 950HU) and
%FEV1 predicted after bronchodilation
The value of %LAA ≤ 950 HU and FEV1
were inversely proportional with p < 0.01
DISCUSSION
In this study, males were predominant
with 98.2%, females only 1.8% The average
age was 69.5 (8.9) and the past history
smoking was on average about 33.4 (10.7)
pack-years The patients had the mean BMI 20.3 (3.3), that was underweight The majority of patients (82.1%) had both symptoms as cough, expectoration and chronic dyspnea The classification COPD into groups A - D based on GOLD guidelines was applied and revealed that COPD patients in group D had the highest percentage (43%), followed by group B and C (22.3% and 23.2%, respectively), finally group A (12.5%) The number of patients with high risks (multiple exacerbation) and more symptoms outweight those with low risks and less symptoms The patients with the severity of airway limitation GOLD 2 and GOLD 3 were predominant (50.9% and 30.2%, respectively), GOLD 1 and GOLD 4 with 12.5% and 5.4%, respectively The parameters of patient’s characteristics are similar to those of Pham Kim Lien et al’s study [2] The difference about age, clinical manifestations and the severity of airways were compatible with the smoking habit as men smoke more than women, and compatible with natural change of diseases and the needs for healthcare with COPD patients
The role of quantitative CT was more and more confirmed in evaluation of the pathological changes in COPD Identifying the severity of emphysema on chest CT based on the percentage of low attenuation area less than the threshold - 950 Houndsfield unit (%LAA ≤ 950 HU), is correlated with histological change In this study, patients with minor and moderate emphysema were 53.6% and 3.6%, respectively, and no case with severe emphysema Pham Kim Lien et al had shown the same results [2]
Trang 6The severity of emphysema on the
chest CT (%LAA ≤ 950 HU) did not correlate
with clinical respiratory symptoms, multiple
exacerbations and classification of COPD
patients in groups A - D based on GOLD
On the contrary, the severity of emphysema
was directly correlation to MRC scales
(PCC = 0.389, p = 0.0001) and to CAT
(PCC = 0.268, p = 0.004), as well as with
BMI (PCC = -0.279, p = 0.003) The results
of this study were similar to those of Yan
Zhang [10] Patients COPD with predominant
emphysema phenotype were recognized
that they are thinner, more dyspneique and
less well-being
Although chest CT could make an
accurate diagnosis of emphysema, it does
not still become the routine method due to
its high cost In the contrary, conventional
chest X-ray could be used routinely for
COPD patients, but its accuracy in
emphysema diagnosis is not consistent in
other studies This study had shown that,
identifying emphysema on chest X-ray and
%LAA ≤ 950 HU on the chest CT were
correlated (p < 0.05) In the two recent
studies, chest X-ray had demonstrated its
value in emphysema diagnosis with sensitivity
and specitivity more than 80% [4, 6]
COPD is characterized by the airway
limitation with incomplete reversibility
which results from the changes in airways
and parenchymal lungs Emphysema status
has led to lose elastic lung recoil causing
the airway limitation in COPD The study
results had shown that emphysema’s
severity on the chest CT is insversly
proportional to %FEV1 predicted value
after bronchodilation (p < 0.01), and compatible with the study of Dang Vinh Hiep et al [1], Gupta P [3] and Yan Zhang [10]
CONCLUSION
The chest CT has the key role to evaluate specific damage and lesions of COPD The severity of emphysema based on the percentage of low attenuation area ≤ 950 HU
on the chest CT is directly correalation with MRC scales and CAT score, inversely correalation with value of post-bronchodilation FEV1 Results from evaluation of existing emphysema by conventional chest X-ray correlated with %LAA ≤ 950 HU Chest X-ray and chest CT could have the significant role to identify the emphysema phenotype
in patients with COPD That is likely to contribute to approach and treat effectively for patients with COPD
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