Influence of Emphysema and Air Trapping Heterogeneity on Pulmonary Function in Patients with COPD

Figures & data

Table 1 Patient Characteristics

Parameter	N=179
Age, years	64 (60, 69)
Sex: male: female	156 (87.2%)/23 (12.8%)
Height	1.67 (1.63, 1.72)
BMI	24.38±3.25
Smoking status, current: former: never	57 (31.8%)/103 (57.5%)/19 (10.6%)
Pack-years	34.5 (18.5, 46.75)
FEV1 (L)	1.52 (1.11, 2.00)
FEV1(%pred)	56% (41%, 71%)
FVC (L), mean ±SD	3.07±0.74
FEV1/FVC	49% (42%, 61%)
IC/TLC	24% (17%, 33%)
CAT	13(8, 18)
mMRC	1(1, 2)
N1AE	0(0, 1)
GOLD
Mild-to-moderate	105 (58.7%)
Severe	74 (41.3%)
EI of the total lung	13.11 (5.36, 22.21)
AT of the total lung	53.74 (36.88, 65.72)
Absolute value of EI_CC_HI	19.04 (9.40, 31.78)
Absolute value of AT_CC_HI	9.76 (3.50, 19.58)
Absolute value of EI_LR_HI	10.42 (4.84, 19.46)
Absolute value of AT_LR_HI	4.44 (1.58, 9.75)

Note: Values are presented as mean ± SD, n (%) or median (interquartile range).

Abbreviations: BMI, body mass index; FEV₁, forced expiratory volume in 1 second; FEV₁(%pred), the FEV₁% predicted; FVC, forced vital capacity; IC/TLC, inspiratory capacity/total lung capacity; CAT, COPD assessment test; mMRC, modified British Medical Research Council; N_1AE, number of COPD acute exacerbations in the past year.

Table 2 Comparison of the Absolute Values of HI Between Patients with Mild-to-Moderate and Severe Disease (GOLD Stage I and II vs GOLD Stage III and IV)

CT	Mild-to-Moderate N=105	Severe N=74	P-Value
Absolute value of EI_CC_HI	20.33 (8.30, 36.01)	18.95 (11.08, 30.29)	>0.05
Absolute value of AT_CC_HI	12.69 (4.82, 23.94)	6.50 (2.36, 12.72)	<0.001
Absolute value of EI_LR_HI	9.55 (3.49, 19.53)	10.66 (6.43, 17.96)	>0.05
Absolute value of AT_LR_HI	5.38 (1.94, 12.11)	3.33 (1.32, 6.43)	<0.05

Note: Values are presented as median (interquartile range).

Abbreviations: Absolute value of EI_CC_HI, absolute value of the cranial-caudal heterogeneity index on full-inspiration; Absolute value of AT_CC_HI, absolute value of the cranial-caudal heterogeneity index on full-expiration; Absolute value of EI_LR_HI, absolute value of the heterogeneity index between the left–right lungs on full-inspiration; Absolute value of AT_LR_HI, absolute value of the heterogeneity index between the left–right lungs on full-expiration.

Figure 1 An example of air trapping heterogeneous distribution on full-expiration (A–D). The blue colored areas showed pixels of <-856 HU, suggestive of air trapping. (A,B) which were the different coronal slices of the same patients (not same with C,D) showed a heterogeneous distribution of AT. (A₁,A₂) were the same coronal slice and (B₁,B₂) were the same coronal slice. FEV₁ (L)= 2.18, FEV₁(%pred)= 71%, FVC (L)= 3.67, FEV₁/FVC= 59%, IC/TLC= 40%. (C,D) which were the different coronal slices of the same patients showed a homogeneous distribution of AT. (C₁,C₂) were the same coronal slice and (D₁,D₂) were the same coronal slice. FEV₁ (L)= 0.74, FEV₁(%pred)= 30%, FVC (L)= 2.16, FEV₁/FVC= 34%, IC/TLC= 20%.

Abbreviations: FEV₁, forced expiratory volume in 1 second; FEV₁(%pred), the FEV₁% predicted; FVC, forced vital capacity; IC/TLC, inspiratory capacity/total lung capacity.

Figure 2 An example of emphysema heterogeneous distribution on full-inspiration (A–D). The blue colored area showed pixels of <-950HU, suggestive of emphysema. (A,B) were the different coronal slices of the same patients (not same with C,D). (A₁,A₂) were the same coronal slice and (B₁,B₂) were the same coronal slice. FEV₁ (L)= 2.18, FEV₁(%pred)= 71%, FVC (L)= 3.67, FEV₁/FVC= 59%, IC/TLC= 40%. (C,D) were the different coronal slices of the same patients. (C₁,C₂) were the same coronal slice and (D₁,D₂) were the same coronal slice. FEV₁ (L)= 0.74, FEV₁(%pred)= 30%, FVC (L)= 2.16, FEV₁/FVC= 34%, IC/TLC= 20%.

Abbreviations: FEV₁, forced expiratory volume in 1 second; FEV₁(%pred), the FEV₁% predicted; FVC, forced vital capacity; IC/TLC: inspiratory capacity/total lung capacity.

Table 3 A Comparison of PFT Parameters Between Patients with Upper-Zone and Lower-Zone Predominance

		Upper-Zone Predominant Cluster	Lower-Zone Predominant Cluster	P-Value
EI	n	89	90
	FVC	3.17±0.75	2.96±0.71	0.054
	FEV1	1.65 (1.13, 2.09)	1.39 (1.05, 1.92)	0.081
	FEV1/FVC	0.50 (0.43, 0.61)	0.48 (0.42, 0.60)	0.281
	FEV1(%pred)	0.60 (0.44, 0.78)	0.55 (0.39, 0.70)	0.100
	IC/TLC	0.25 (0.18, 0.34)	0.22 (0.16, 0.30)	0.245
AT	n	67	112
	FVC	3.33±0.70	2.91±0.71	<0.001
	FEV1	1.77 (1.38, 2.25)	1.36 (0.98, 1.79)	<0.001
	FEV1/FVC	0.56 (0.47, 0.63)	0.46 (0.40, 0.58)	0.001
	FEV1(%pred)	0.65 (0.47, 0.81)	0.50 (0.38, 0.69)	<0.001
	IC/TLC	0.28 (0.19, 0.34)	0.22 (0.15, 0.30)	0.105

Note: Values are presented as mean ± SD or median (interquartile range).

Abbreviations: EI, emphysema index; AT, air trapping; FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; FEV₁(%pred), the FEV₁% predicted; IC/TLC, inspiratory capacity/total lung capacity.

Table 4 A Comparison of PFT Parameters Between Patients with Left-Lung and Right-Lung Predominance

		Left–Lung Predominance Cluster	Right-Lung Predominance Cluster	P-Value
EI	n	85	94
	FVC	3.03±0.65	3.10±0.80	0.491
	FEV1	1.49 (1.13, 1.97)	1.54 (1.06, 2.01)	0.738
	FEV1/FVC	0.49 (0.41, 0.61)	0.50 (0.42, 0.60)	0.971
	FEV1(%pred)	0.55 (0.40, 0.73)	0.57 (0.42, 0.71)	0.936
	IC/TLC	0.24 (0.19, 0.34)	0.23 (0.15, 0.32)	0.320
AT	n	122	57
	FVC	3.02±0.73	3.17±0.75	0.199
	FEV1	1.39 (1.05, 1.95)	1.75 (1.30, 2.18)	0.012
	FEV1/FVC	0.47 (0.41, 0.59)	0.58 (0.46, 0.63)	0.004
	FEV1(%pred)	0.51 (0.39, 0.69)	0.67 (0.53, 0.80)	0.002
	IC/TLC	0.22 (0.16, 0.30)	0.27 (0.23, 0.36)	0.027

Note: Values are presented as mean ± SD or median (interquartile range).

Abbreviations: EI, emphysema index; AT, air trapping; FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; FEV₁(%pred), the FEV₁% predicted; IC/TLC, inspiratory capacity/total lung capacity.

Table 5 Multivariate Linear Regression Analysis Showing the Relationship Between CT Parameters and Pulmonary Function Parameters

Variables	FEV1			FEV1(%pred)			FVC			FEV1/FVC			IC/TLC
	β	p-Value	R^2	β	p-Value	R^2	β	p-Value	R^2	β	p-Value	R^2	β	p-Value	R^2
Sex				0.212	<0.001					0.15	0.004
Age	−0.165	0.003					−0.264	<0.001
Height	0.275	<0.001					0.474	<0.001					0.257	0.004
Pack_year													−0.195	0.025
EI	−0.172	0.037		−0.197	0.017					−0.288	<0.001
AT	−0.432	<0.001		−0.427	<0.001		−0.203	0.002		−0.484	<0.001		−0.576	<0.001
Absolute value of EI_CC_HI
Absolute value of AT_CC_HI	0.202	0.002		0.207	0.002		0.149	0.022		0.175	0.003
Absolute value of EI_LR_HI
Absolute value of AT_LR_HI	−0.139	0.026		−0.137	0.028					−0.188	0.001
Cumulative R^2			0.497			0.503			0.419			0.609			0.364

Abbreviations: EI, emphysema index; AT, air trapping; FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second; FEV₁(%pred), the FEV₁% predicted; IC/TLC, inspiratory capacity/total lung capacity; Absolute value of EI_CC_HI, absolute value of the cranial-caudal heterogeneity index on full-inspiration; Absolute value of AT_CC_HI, absolute value of the cranial-caudal heterogeneity index on full-expiration; Absolute value of EI_LR_HI, absolute value of the heterogeneity index between the left–right lungs on full-inspiration; Absolute value of AT_LR_HI, absolute value of the heterogeneity index between the left–right lungs on full-expiration.

Figure 3 The correlation between the absolute value of AT_ CC_HI and pulmonary function. (A-E) showed the correlation between the absolute value of AT_CC_HI and PFT parameters, including FEV₁(A), FEV₁(%pred) (B), FVC (C), FEV₁/FVC (D) and IC/TLC (E).

Abbreviations: Absolute value of AT_CC_HI, absolute value of the cranial-caudal heterogeneity index on full-expiration; PFT, pulmonary function tests; FEV₁, forced expiratory volume in 1 second; FEV₁(%pred), the FEV₁% predicted; FVC, forced vital capacity; IC/TLC, inspiratory capacity/total lung capacity.