Correlations of Computed Tomography Measurement of Distal Pulmonary Vascular Pruning with Airflow Limitation and Emphysema in COPD Patients

Figures & data

Figure 1 Flowchart of the study.

Figure 2 (A) Segmented lung field by setting the threshold between −500 HU and −1024 HU; (B) Converted into binary image where pulmonary vessels were displayed in black with a window level of −720 HU; (C) Mask image after setting the circularity from 0.9 to 1.0 and the vascular size range from 0–5mm².

Table 1 Characteristics of Study Participants

Characteristic	Never-Smoking Control Subjects	Smoking Control Subjects	GOLD 1	GOLD2	GOLD3	GOLD4	P1	P2	P3
Subject n	37	34	30	91	75	20
Age (years)	56.38±9.70	58.41±7.11	67.40±7.04	67.54±9.02	65.51±7.08	63.50±7.72	0.315	0.029	<0.001
Sex							<0.001	0.078	<0.001
Male	14	32	25	85	72	19
Female	23	2	5	6	3	1
BMI (kg/m2)	24.27(22.67–26.59)	25.63(22.73–27.40)	21.13 (20.40–24.42)	24.11 (22.26–26.03)	21.13 (18.39–23.37)	21.06 (20.25–22.70)	0.44	<0.001	<0.001
mMRC dyspnea score							0.772	<0.001	<0.001
0	14	18	6	13	3	0
1	8	8	20	44	22	0
2	3	2	4	27	32	7
3	0	0	0	3	15	12
4	0	0	0	2	1	1
CAT score	2 (1–5.75)	4 (2–8)	7(5–9)	7(5–10)	10(7–14)	13.5(10–20.25)	0.163	<0.001	<0.001
Smoking status							<0.001	0.171	<0.001
Never-smoker	37	-	9	13	4	1
Ex-smoker	-	15	9	49	42	14
Current smoker	-	19	12	29	29	5
Pack-years	-	30(14.38–40)	23 (0–39)	26.25 (9.73–40)	40 (22.5–60)	40 (31.25–50)	<0.001	<0.001	<0.001
%CSA<5(%)	0.60 (0.55–0.78)	0.61 (0.46–0.71)	0.50 (0.42–0.58)	0.47 (0.41–0.55)	0.38 (0.32–0.45)	0.35 (0.30–0.41)	0.105	<0.001	<0.001
%CSA5–10(%)	0.31 (0.24–0.38)	0.29 (0.24–0.34)	0.23 (0.21–0.28)	0.25 (0.21–0.29)	0.20 (0.15–0.24)	0.18 (0.16–0.20)	0.369	<0.001	<0.001
PA:AO	0.86 (0.81–0.97)	0.82 (0.75–0.94)	0.84 (0.73–0.91)	0.81 (0.73–0.88)	0.83 (0.75–0.88)	0.83 (0.80–0.91)	0.173	0.484	0.007
%LAA-950	0.43 (0.26–1.15)	0.68 (0.31–1.27)	2.06 (0.66–4.72)	4.46 (1.52–11.41)	18.97 (9.07–27.16)	25.83 (18.64–38.36)	0.239	<0.001	<0.001
WT (mm)	1.57 (1.51–1.65)	1.66 (1.58–1.69)	1.59 (1.50–1.69)	1.61 (1.48–1.69)	1.54 (1.45–1.60)	1.55 (1.45–1.62)	0.013	0.088	0.005
WA (%)	0.64 (0.63–0.68)	0.65 (0.61–0.67)	0.65 (0.62–0.66)	0.66 (0.61–0.68)	0.66 (0.64–0.67)	0.66 (0.63–0.67)	0.555	0.663	0.233
TDR	0.20 (0.19–0.21)	0.20 (0.19–0.20)	0.20 (0.18–0.20)	0.20 (0.18–0.21)	0.20 (0.19–0.21)	0.20 (0.19–0.21)	0.491	0.641	0.403

Notes: The continuous variable are presented as mean±SD or median with IQR as appropriate; categorical variables are presented as number of subjects; P₁-value: comparison between never-smoking control subjects and smoking control subjects. P₂-value: trend test across GOLD stage. P₃-value: comparison between healthy control subjects and COPD patients.

Abbreviations: BMI, body mass index; mMRC dyspnea score, modified British Medical Research Council dyspnea score; CAT score, the score of a questionnaire call COPD assessment test; %CSA<5, the percentage of total cross-sectional area of pulmonary vessels <5 mm² to the total lung area of the selected slices; %CSA5–10, the percentage of total cross-sectional area of pulmonary vessels among 5–10 mm² to the total lung area of the selected slices; PA:AO ratio, the ratio of diameter of the main pulmonary artery (PA) to the diameter of ascending aorta (AO) at the level of the bifurcation; %LAA-950, Percentage of low-attenuation areas less than −950 Hounsfield units to the total lung volume; WT, mean wall area of this airway; WA%, airway wall percentage; TDR, thickness–diameter ratio;

Figure 3 Relationship between %CSA<5 and FEV1%pred (r=0.564, P<0.001).

Figure 4 ROC curve of %CSA<5 for the discrimination of COPD. (AUC, 0.816; cut-off value, 0.537; Youden index J, 0.501; sensitivity, 78.24%; specificity, 71.83%).

Table 2 Comparison of Characteristics of Participants Above and Below the Inflection Point

%CSA<5	≥0.524	<0.524	P
Subjects n	104	183
Age (years)	62.60±1.03	65.86±0.61	<0.001
Sex			<0.001
Male	75	172
Female	29	11
BMI (kg/m2)	24.18±0.35	22.29±0.25	<0.001
mMRC dyspnea score			<0.001
0	31	23
1	37	65
2	15	60
3	3	27
4	1	3
CAT score	6 (2.5–10)	8 (6–11)	<0.001
Smoking status			<0.001
Never-smoker	40	24
Ex-smoker	32	97
Current smoker	32	62
Pack-years	22.50 (0–40)	30.40 (12.50–49.15)	<0.001
FEV1%pred	83.30 (66.60–100.75)	52.60 (36.10–75.40)	<0.001
PA:AO	0.87 (0.78–0.94)	0.81 (0.73–0.88)	<0.001
%LAA-950	0.68 (0.36–2.23)	12.00 (3.54–23.94)	<0.001
WT (mm)	1.61 (1.50–1.69)	1.58 (1.48–1.64)	0.153
WA (%)	0.65 (0.61–0.67)	0.65 (0.63–0.67)	0.464
TDR	0.20 (0.18–0.21)	0.20 (0.19–0.21)	0.908

Notes: The continuous variable are presented as mean±SD or median with IQR as appropriate; categorical variables are presented as number of subjects; P-value: comparison between subjects upper and below the inflection point.

Abbreviations: BMI, body mass index; mMRC dyspnea score, modified British Medical Research Council dyspnea score; CAT score, the score of a questionnaire call COPD assessment test; %CSA<5, the percentage of total cross-sectional area of pulmonary vessels <5 mm² to the total lung area of the selected slices; %CSA5–10, the percentage of total cross-sectional area of pulmonary vessels among 5–10 mm² to the total lung area of the selected slices; PA:AO ratio, the ratio of diameter of the main pulmonary artery (PA) to the diameter of ascending aorta (AO) at the level of the bifurcation; %LAA-950, Percentage of low-attenuation areas less than −950 Hounsfield units to the total lung volume; WT, mean wall area of this airway; WA%, airway wall percentage; TDR, thickness–diameter ratio.

Figure 5 Association between %CSA<5 and %LAA-950. The fitting effect of segmented regression (adjust R2, 0.474; P <0.001) was much better than ordinary linear regression (adjust R2, 0.332, P<0.001). The slope of the ordinary linear regression line was β0 = −41.308. In the segmented regression, before %CSA<5 decrease to inflection point (0.524), the regression line was nearly flat (β₁ = −3.104, P < 0.001), while the slope of the regression line suddenly flared up when the %CSA<5 went down below the inflection point (β₂ = −96.615, P < 0.001).