Analysis of airway structural parameters in Han Chinese adults: a prospective cross-sectional study

Figures & data

Figure 1. Diagram of central airway measurement. (A) A three-dimensional reconstruction of the tracheobronchial tree from a 25-year-old female, presenting cross-sectional views of zones I-III and V-VIII. Annotations in the lower left corner of each section provide the mean airway wall thickness (AWT in mm) and airway luminal area (ALA in mm²). Subcarinal angle (SCA in degrees) is denoted in the green box, measured at 80.9 degrees; (B) a longitudinal cross-section matched to the yellow line in (a), with the blue line marking the measurement path along the airway’s length. Progressing from the left, the first yellow marker on the blue trajectory signifies the division into the right and left main bronchi, the second marker signals the entry to the right lung’s upper lobe, and the third marker delineates the convergence points to the right lung’s middle and lower lobes. ‘AL’ refers to airway length, ‘RMB’ is an abbreviation for the right main bronchus, and ‘RMLB’ represents the right middle lobar bronchus.

Figure 2. The demographics of the entire study Population and a comparison of males and females. (A) (B) (C) are divergent bar charts displaying the distribution of age, height, and weight, respectively, among the 888 examinees included in the study, categorized by sex. The inset tables in the lower left corner of each chart detail the mean, median, and standard deviation (SD) and the range [minimum, maximum] for each examinee. Additionally, the tables provide P-values for assessing statistical differences in age, height, and weight between male and female examinees.

Figure 3. Comparative airway lengths and SCA by sex. The figure presents a series of box-and-whisker plots with superimposed individual data points, delineating the distribution of airway lengths in millimeters (mm) across various segments: trachea, right main bronchus (RMB), right superior lobar bronchus (RSLB), right middle lobar bronchus (RMLB), left main bronchus (LMB), left superior lobar bronchus (LSLB), and left inferior lobar bronchus (LILB). Additionally, the subcarinal angle (SCA) is depicted in degrees (deg). Data are stratified by sex, with each plot detailing the mean ± standard deviation (SD) and the median along with the range [minimum, maximum] for females (N = 456, in red) and males (N = 432, in blue). Levels of statistical significance are marked by asterisks (*** for p < 0.001); ‘NS’ indicates a lack of significant difference.

Figure 4. Comparative AWT by sex. This figure features a series of box-and-whisker plots with superimposed individual data points, displaying the distribution of airway wall thickness (AWT) in millimeters (mm) for seven zones: I zone, II zone, III zone, V zone, VI zone, VII zone, and VIII zone. The plots are color-coded to differentiate between female (N = 456, in red) and male (N = 432, in blue) examinees, with each plot providing detailed statistics including mean ± standard deviation (SD), median, and the range [minimum, maximum]. Significant differences between sexes are indicated by asterisks (*** for p < 0.001).

Figure 5. Comparative ALA by sex. This figure features a series of box-and-whisker plots with superimposed individual data points, displaying the distribution of airway lumen area (ALA) in square millimeters (mm²) for seven zones: I zone, II zone, III zone, V zone, VI zone, VII zone, and VIII zone. The plots are color-coded to differentiate between female (N = 456, in red) and male (N = 432, in blue) examinees, with each plot providing detailed statistics including mean ± standard deviation (SD), median, and the range [minimum, maximum]. Significant differences between sexes are indicated by asterisks (*** for p < 0.001).

Figure 6. Correlation analysis of airway structural parameters and influencing factors (mean values). This heatmap depicts the correlation coefficients reflecting the strength and direction of associations between comprehensive airway structural parameters—airway lumen area (ALA) and airway wall thickness (AWT) across seven zones (I, II, III, V, VI, VII, VIII), the subcarinal angle (SCA), and the airway lengths(AL) (trachea, right main bronchus (RMB), right superior lobar bronchus (RSLB), right middle lobar bronchus (RMLB), left main bronchus (LMB), left superior lobar bronchus (LSLB), and left inferior lobar bronchus (LILB))—and influencing factors (age, height, weight) in both female and males. The color gradient encodes the correlation’s nature and strength: reds indicate positive correlations, with darker hues signifying stronger positive relationships, and blues represent negative correlations, with deeper blues denoting stronger negative relationships. Each cell specifies the correlation coefficient and asterisks (*) mark statistical significance at p < 0.05. The color scale on the side provides a reference from -1.0, indicative of a strong negative correlation, to +1.0, indicative of a strong positive correlation.

Figure 7. Relationships with absolute values of correlation coefficients greater than 0.2. (A) The relationship between LMB length and height; (B) The relationship between LMB length and age; (C) The relationship between SCA and weight; (D) The relationship between ALA in Zone I and height; (E) The relationship between ALA in Zone III and age; (F) The relationship between ALA in Zone VIII and age; (G) The relationship between AWT in Zone V and age; (H) The relationship between AWT in Zone VII and age. Data for females (red triangles) and males (blue circles) are indicated separately. Abbreviations: left main bronchus (LMB), the subcarinal angle (SCA), airway lumen area (ALA), airway wall thickness (AWT), and correlation coefficient (r).

Table 1. Multiple linear regression analysis of AL and SCA.

Response	Variable	Estimate	SE	p-value	β
Trachea AL (R^2=0.159)	Sex, Male	2.580	1.158	<0.05	0.033
	Age, y	1.603	0.419	<0.05	0.057
	Height, cm	5.080	0.633	<0.05	0.120
	Weight, kg	−2.433	0.480	<0.05	−0.076
RMB AL (R^2=0.062)	Sex, Male	1.713	0.491	<0.05	0.052
	Age, y	0.316	0.178	0.075	0.027
	Height, cm	0.695	0.268	<0.05	0.039
	Weight, kg	−0.431	0.203	<0.05	−0.032
RSLB AL (R^2=0.175)	Sex, Male	1.178	0.285	<0.05	0.062
	Age, y	0.351	0.103	<0.05	0.051
	Height, cm	0.601	0.156	<0.05	0.058
	Weight, kg	0.323	0.118	<0.05	0.041
RMLB AL (R^2=0.096)	Sex, Male	1.467	0.509	<0.05	0.043
	Age, y	0.343	0.184	0.063	0.028
	Height, cm	1.318	0.278	<0.05	0.071
	Weight, kg	−0.510	0.211	<0.05	−0.036
LMB AL (R^2=0.163)	Sex, Male	0.985	0.519	0.058	0.028
	Age, y	−0.109	0.188	0.563	−0.009
	Height, cm	1.876	0.284	<0.05	0.099
	Weight, kg	0.042	0.215	0.844	0.003
LSLB AL (R^2=0.135)	Sex, Male	1.455	0.260	<0.05	0.084
	Age, y	0.306	0.094	<0.05	0.049
	Height, cm	0.192	0.142	0.178	0.020
	Weight, kg	0.203	0.108	0.059	0.028
LILB AL (R^2=0.089)	Sex, Male	1.246	0.270	<0.05	0.069
	Age, y	0.056	0.098	0.570	0.009
	Height, cm	0.414	0.148	<0.05	0.042
	Weight, kg	−0.259	0.112	<0.05	−0.035
SCA (R^2=0.120)	Sex, Male	0.930	0.910	0.308	0.015
	Age, y	−0.784	0.330	<0.05	−0.036
	Height, cm	−3.352	0.498	<0.05	−0.101
	Weight, kg	3.929	0.377	<0.05	0.156

AL: airway length; SCA: subcarinal angle; RMB: Right main bronchus; RSLB: Right superior lobar bronchus; RMLB: Right middle lobar bronchus; LMB: Left main bronchus; LSLB: Left superior lobar bronchus; LILB: Left inferior lobar bronchus.

Table 2. Multiple linear regression analysis of AWT.

Response	Variable	Estimate	SE	p-value	β
I Zone (R^2=0.451)	Sex, Male	0.368	0.024	<0.05	0.232
	Age, y	0.033	0.009	<0.05	0.057
	Height, cm	0.055	0.013	<0.05	0.064
	Weight, kg	−0.027	0.010	<0.05	−0.041
II Zone (R^2=0.316)	Sex, Male	0.447	0.042	<0.05	0.161
	Age, y	0.043	0.015	<0.05	0.043
	Height, cm	0.121	0.023	<0.05	0.080
	Weight, kg	−0.092	0.017	<0.05	−0.080
III Zone (R^2=0.164)	Sex, Male	0.243	0.040	<0.05	0.092
	Age, y	0.039	0.014	<0.05	0.041
	Height, cm	0.072	0.022	<0.05	0.050
	Weight, kg	−0.013	0.016	0.446	−0.011
V Zone (R^2=0.245)	Sex, Male	0.465	0.048	<0.05	0.144
	Age, y	0.096	0.018	<0.05	0.082
	Height, cm	0.075	0.026	<0.05	0.043
	Weight, kg	−0.076	0.020	<0.05	−0.057
VI Zone (R^2=0.378)	Sex, Male	0.434	0.031	<0.05	0.208
	Age, y	0.034	0.011	<0.05	0.045
	Height, cm	−0.017	0.017	0.323	−0.015
	Weight, kg	0.064	0.013	<0.05	0.074
VII Zone (R^2=0.283)	Sex, Male	0.290	0.031	<0.05	0.139
	Age, y	0.087	0.011	<0.05	0.115
	Height, cm	0.040	0.017	<0.05	0.035
	Weight, kg	0.006	0.013	0.647	0.007
VIII Zone (R^2=0.338)	Sex, Male	0.259	0.026	<0.05	0.151
	Age, y	0.056	0.009	<0.05	0.090
	Height, cm	0.075	0.014	<0.05	0.080
	Weight, kg	−0.023	0.011	<0.05	−0.033

Table 3. Multiple linear regression analysis ALA.

Response	Variable	Estimate	SE	p-value	β
I Zone (R^2=0.665)	Sex, Male	85.235	3.552	<0.05	0.360
	Age, y	1.330	1.286	0.301	0.016
	Height, cm	12.847	1.942	<0.05	0.099
	Weight, kg	−4.940	1.471	<0.05	−0.05
II Zone (R^2=0.609)	Sex, Male	68.294	3.305	<0.05	0.310
	Age, y	8.311	1.196	<0.05	0.104
	Height, cm	12.430	1.807	<0.05	0.103
	Weight, kg	−6.869	1.369	<0.05	−0.075
III Zone (R^2=0.560)	Sex, Male	59.321	3.636	<0.05	0.245
	Age, y	11.527	1.316	<0.05	0.131
	Height, cm	14.265	1.988	<0.05	0.108
	Weight, kg	−2.144	1.506	0.155	−0.021
V Zone (R^2=0480)	Sex, Male	39.582	2.696	<0.05	0.220
	Age, y	3.619	0.976	<0.05	0.056
	Height, cm	8.176	1.474	<0.05	0.083
	Weight, kg	−0.780	1.116	0.485	−0.01
VI Zone (R^2=0.537)	Sex, Male	33.052	1.829	<0.05	0.271
	Age, y	3.525	0.662	<0.05	0.080
	Height, cm	2.759	1.000	<0.05	0.041
	Weight, kg	1.577	0.757	<0.05	0.031
VII Zone (R^2=0.485)	Sex, Male	33.337	2.399	<0.05	0.209
	Age, y	6.086	0.868	<0.05	0.105
	Height, cm	10.159	1.312	<0.05	0.116
	Weight, kg	−4.338	0.994	<0.05	−0.066
VIII Zone (R^2=0.504)	Sex, Male	29.046	1.973	<0.05	0.221
	Age, y	6.988	0.714	<0.05	0.147
	Height, cm	6.700	1.079	<0.05	0.093
	Weight, kg	−1.872	0.817	<0.05	−0.034

Table 4. AIC values from univariable models for subcategories of AWT and ALA.

Subtype	Sex	Age	Height	Weight
Airway Wall Thickness
I Zone	1.950	499.499	247.002	438.734
II Zone	1010.339	1300.071	1123.961	1282.620
III Zone	896.483	1037.417	940.835	1009.037
V Zone	1281.461	1460.103	1396.744	1474.710
VI Zone	495.597	875.394	716.644	742.777
VII Zone	521.278	713.153	650.836	708.101
VIII Zone	161.349	460.479	285.917	428.971
Airway Lumen Area
I Zone	8912.548	9837.813	9355.622	9711.347
II Zone	8819.671	9554.752	9210.252	9494.454
III Zone	9001.138	9607.998	9286.009	9525.965
V Zone	8412.684	8953.344	8627.479	8846.467
VI Zone	7724.414	8357.950	8067.344	8223.719
VII Zone	8254.353	8740.110	8455.126	8697.819
VIII Zone	7924.682	8399.178	8178.433	8368.333

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.