Contributions of Emphysema and Functional Small Airway Disease on Intrapulmonary Vascular Volume in COPD

Figures & data

Figure 1 Flowchart of participant selection.

Abbreviations: COPD, chronic obstructive pulmonary disease; CT, computed tomography; PFTs, pulmonary function tests; PRISm, Preserved Ratio Impaired Spirometry.

Figure 2 Schematic diagram of parameter measurement in biphasic quantitative CT.

Notes: (A) Identification and segmentation of lung fissures and lobes on CT images by the 3D adaptive border marching algorithm and the implicit surface functions. The principal curvatures and the principal directions were used to distinguish pulmonary vessels from lung tissue, and the vascular tree was automatically extracted and segmented to calculate IPVV in the whole lung. (B) Normal lung tissue areas (green), emphysema areas (red), and functional small disease areas (yellow) were quantified by the PRM method.

Table 1 Comparison of Subject’s Baseline Characteristics and PFTs

Variables	Normal	PRISm	Mild COPD	Severe COPD	F/H/X^2	P value
	(n=41)	(n=22)	(n=32)	(n=15)
Sex (Male/Female)	(40/1)	(22/0)	(27/5)	(15/0)	1.214	0.271
Age (y)	50 (39, 59)	52 (49, 60)	63 (57, 71)	60 (53, 71)	45.636	<0.001
BMI (kg/m^2)	24.143±2.888	25.549±2.920	23.315±2.188	22.157±3.698	3.102	0.032
Smoking Index (pieces/y)	380 (200, 600)	400 (120, 700)	800 (250, 1600)	1600 (700, 2000)	27.476	<0.001
FEV1% (%)	91.000 (83.250, 96.000)	72.000 (69.500, 76.000)	64.000 (52.900, 77.000)	41.000 (34.000, 44.000)	60.281	<0.001
FEV1/FVC (%)	83.000 (75.500, 85.000)	79.000 (76.000, 84.000)	60.000 (50.000, 64.000)	46.500 (37.100, 54.000)	60.367	<0.001

Abbreviations: PRISm, Preserved Ratio Impaired Spirometry; COPD, chronic obstructive pulmonary disease; BMI, body mass index; FEV1, forced expiratory volume in 1 second; FEV1%, predicted value of forced expiratory volume in 1 second; FVC, forced vital capacity.

Table 2 Comparison of Subjects’ Quantitative CT Indexes

Variables	Normal	PRISm	Mild COPD	Severe COPD	F/H	P value
	(n=41)	(n=22)	(n=32)	(n=15)
IPVVin (mL)	170.724±24.855	164.890±30.569	150.375±19.728	163.583±12.469	1.843	0.144
IPVVex (mL)	119.800 (104.093, 134.270)	135.040 (122.540, 139.415)	141.490 (123.440, 154.730)	160.130 (157.630, 164.690)	25.657	<0.001
IPVV relative value	0.726 (0.624, 0.837)	0.827 (0.772, 0.891)	0.928 (0.898, 0.971)	0.981 (0.961, 0.987)	74.709	<0.001
IPVV difference value (mL)	−36.150 (−71.768, −29.915)	−30.540 (−37.580, −15.735)	−10.280 (−15.440, −4.540)	−3.170 (−6.610, −1.960)	70.962	<0.001
Emph% (%)	4.205 (2.350, 7.458)	5.706 (2.995, 8.715)	13.390 (5.090, 22.970)	33.290 (28.210, 38.320)	60.383	<0.001
fsAD% (%)	15.701±10.880	18.664±11.996	24.935±9.028	31.037±4.581	4.561	0.005
Normal% (%)	58.790±10.533	57.577±12.853	43.821±17.947	17.744±3.886	36.852	<0.001

Abbreviations: PRISm, Preserved Ratio Impaired Spirometry; COPD, chronic obstructive pulmonary disease; IPVV, intrapulmonary vascular volume; IPVVin, inspiratory intrapulmonary vascular volume; IPVVex, expiratory intrapulmonary vascular volume; Emph%, emphysema volume ratio; fsAD%, functional small airway lesions volume ratio; Normal%, normal areas volume ratio.

Table 3 Correlations Between IPVV and PFTs

Variables	IPVVin		IPVVex		IPVV Relative Value		IPVV Difference Value
	r	P value	r	P value	r	P value	r	P value
FEV1%	0.060	0.557	−0.464	<0.001	−0.680	<0.001	−0.662	<0.001
FEV1/FVC	0.114	0.259	−0.481	<0.001	−0.759	<0.001	−0.740	<0.001

Abbreviations: IPVV, intrapulmonary vascular volume; IPVVin, inspiratory intrapulmonary vascular volume; IPVVex, expiratory intrapulmonary vascular volume; FEV1, forced expiratory volume in 1 second; FEV1%, predicted value of forced expiratory volume in 1 second; FVC, forced vital capacity.

Table 4 Correlations Between PRM Indexes and PFTs

Variables	Emph%		fsAD%		Normal%
	r	P value	r	P value	r	P value
FEV1%	−0.547	<0.001	−0.470	<0.001	0.490	<0.001
FEV1/FVC	−0.683	<0.001	−0.612	<0.001	0.662	<0.001

Figure 3 Correlations between IPVV and PFTs.

Notes: Scatter plots were drawn, and Spearman’s rank correlation was used. A P value <0.05 was considered statistically significant. (A) Correlation between inspiratory IPVV and FEV1%. (B) Correlation between inspiratory IPVV and FEV1/FVC. (C) Correlation between expiratory IPVV and FEV1%. (D) Correlation between expiratory IPVV and FEV1/FVC. (E) Correlation between IPVV relative value and FEV1%. (F) Correlation between IPVV relative value and FEV1/FVC. (G) Correlation between IPVV difference value and FEV1%. (H) Correlation between IPVV difference value and FEV1/FVC.

Abbreviations: FEV1, forced expiratory volume in 1 second; FEV1%, predicted value of forced expiratory volume in 1 second; FVC, forced vital capacity; IPVV, intrapulmonary vascular volume; IPVVin, inspiratory intrapulmonary vascular volume; IPVVex, expiratory intrapulmonary vascular volume.

Figure 4 Correlations between PRM indexes and PFTs.

Notes: Scatter plots were drawn, and Spearman’s rank correlation was used. A P value <0.05 indicated a statistically significant difference. (A) Correlation between Emph% and FEV1%. (B) Correlation between Inspiratory Emph% and FEV1/FVC. (C) Correlation between fsAD% and FEV1%. (D) Correlation between fsAD% and FEV1/FVC. (E) Correlation between Normal% and FEV1%. (F) Correlation between Normal% and FEV1/FVC.

Abbreviations: Emph%, emphysema volume ratio; fsAD%, functional small airway lesions volume ratio; Normal%, normal areas volume ratio; FEV1, forced expiratory volume in 1 second; FEV1%, predicted value of forced expiratory volume in 1 second; FVC, forced vital capacity.

Table 5 Correlations Between IPVV and PRM Indexes

Variables	IPVVin		IPVVex		IPVV Relative Value		IPVV Difference Value
	r	P value	r	P value	r	P value	r	P value
Emph%	−0.071	0.459	0.488	<0.001	0.737	<0.001	0.713	<0.001
fsAD%	−0.073	0.451	0.390	<0.001	0.544	<0.001	0.527	<0.001
Normal%	0.097	0.312	−0.438	<0.001	−0.696	<0.001	−0.679	<0.001

Abbreviations: IPVV, intrapulmonary vascular volume; IPVVin, inspiratory intrapulmonary vascular volume; IPVVex, expiratory intrapulmonary vascular volume; Emph%, emphysema volume ratio; fsAD%, functional small airway lesions volume ratio; Normal%, normal areas volume ratio.

Figure 5 Correlations between IPVV and PRM indexes.

Notes: Scatter plots were drawn, and Spearman’s rank correlation was used. A P value <0.05 indicated a statistically significant difference. (A) Correlation between Inspiratory IPVV and Emph%. (B) Correlation between inspiratory IPVV and fsAD%. (C) Correlation between inspiratory IPVV and Normal%. (D) Correlation between expiratory IPVV and Emph%. (E) Correlation between expiratory IPVV and fsAD%. (F) Correlation between expiratory IPVV and Normal%. (G) Correlation between IPVV relative value and Emph%. (H) Correlation between IPVV relative value and fsAD%. (I) Correlation between IPVV relative value and Normal%. (J) Correlation between IPVV difference value and Emph%. (K) Correlation between IPVV difference value and fsAD%. (L) Correlation between IPVV difference value and Normal%.

Abbreviations: IPVV, intrapulmonary vascular volume; IPVVin, inspiratory intrapulmonary vascular volume; IPVVex, expiratory intrapulmonary vascular volume; Emph%, emphysema volume ratio; fsAD%, functional small airway lesions volume ratio; Normal%, normal areas volume ratio.

Table 6 Multiple Linear Regression Analysis of IPVV in Emph% and fsAD%

		β	95% CI	P value
IPVVin	Emph%	−0.256	(−0.739, 0.227)	0.295
(R^2=0.016)	fsAD%	−0.057	(−0.541, 0.427)	0.815
IPVVex	Emph%	0.805	(0.374, 1.237)	<0.001
(R^2=0.182)	fsAD%	0.249	(−0.183, 0.682)	0.256
IPVV Relative Value	Emph%	0.006	(0.005, 0.008)	<0.001
(R^2=0.462)	fsAD%	0.002	(0.000, 0.003)	0.047
IPVV difference value	Emph%	1.062	(0.735, 1.388)	<0.001
(R^2=0.397)	fsAD%	0.307	(−0.021, 0.634)	0.066

Abbreviations: IPVV, intrapulmonary vascular volume; IPVVin, inspiratory intrapulmonary vascular volume; IPVVex, expiratory intrapulmonary vascular volume; Emph%, emphysema volume ratio; fsAD%, functional small airway lesions volume ratio.