Tracheobronchial Angle Measurements in Children: An Anthropometric Retrospective Study With Multislice Computed Tomography

Identification of age-dependent features of human bronchi using explainable artificial intelligence

Background

Ageing induces functional and structural alterations in organs, and age-dependent parameters have been identified in various medical data sources. However, there is currently no specific clinical test to quantitatively evaluate age-related changes in bronchi. This study aimed to identify age-dependent bronchial features using explainable artificial intelligence for bronchoscopy images.

Methods

The present study included 11 374 bronchoscopy images, divided into training and test datasets based on the time axis. We constructed convolutional neural network (CNN) models and evaluated these models using the correlation coefficient between the chronological age and the "bronchial age" calculated from bronchoscopy images. We employed gradient-weighted class activation mapping (Grad-CAM) to identify age-dependent bronchial features that the model focuses on. We assessed the universality of our model by comparing the distribution of bronchial age for each respiratory disease or smoking history.

Results

We constructed deep-learning models using four representative CNN architectures to calculate bronchial age. Although the bronchial age showed a significant correlation with chronological age in each CNN architecture, EfficientNetB3 achieved the highest Pearson's correlation coefficient (0.9617). The application of Grad-CAM to the EfficientNetB3-based model revealed that the model predominantly attended to bronchial bifurcation sites, regardless of whether the model accurately predicted chronological age or exhibited discrepancies. There were no significant differences in the discrepancy between the bronchial age and chronological age among different respiratory diseases or according to smoking history.

Conclusion

Bronchial bifurcation sites are universally important age-dependent features in bronchi, regardless of the type of respiratory disease or smoking history.

Determining normal values for lower trachea and bronchi size in children by computed tomography (CT)

BACKGROUND

Normative data for central airway dimensions are a prerequisite to objectively assess large airway pathologies. Studies with computed tomography (CT) measurements of normal trachea and bronchi size in children are scarce.

OBJECTIVE

The purpose of this study is to establish normal values of central airway dimensions in children by CT.

METHODS

The study included chest CT studies from children aged 0-18 years. Any condition that predisposed the patient to have an abnormal tracheal or bronchial size was excluded. Airway diameters and cross-sectional area (CSA) were measured using double oblique reconstructions at five levels: proximal trachea, mid-trachea, distal trachea, right main bronchus, and left main bronchus.

RESULTS

The inclusion criteria were met by 110 subjects (mean age, 10.8 years; SD, 5.2 years). Various regression models that considered the relationship between patient demographics and anteroposterior (AP) diameter, transverse diameter, and CSA at each of the five levels were assessed. R² was utilized to select the best model. Multiple formulae (using patient age) were developed to calculate expected normal dimensions for five levels in the central airways on the natural log scale. Finally, z-scores were obtained for central airway dimensions at these five levels.

CONCLUSION

Normative data in pediatric central airways are crucial to identify large airway pathologies. We propose using the formulae devised in our study to calculate the predicted dimensions of central airways and their z-scores in pediatric patients. Normative data from our study will aid in objective quantification of central airways, increase clinician confidence, and provide appropriate patient care.

Transmission of Oscillatory Volumes into the Preterm Lung during Noninvasive High-Frequency Ventilation

Rationale: There is increasing evidence for a clinical benefit of noninvasive high-frequency oscillatory ventilation (nHFOV) in preterm infants. However, it is still unknown whether the generated oscillations are effectively transmitted to the alveoli.Objectives: To assess magnitude and regional distribution of oscillatory volumes (V_Osc) at the lung level.Methods: In 30 prone preterm infants enrolled in a randomized crossover trial comparing nHFOV with nasal continuous positive airway pressure, electrical impedance tomography recordings were performed. During nHFOV, the smallest amplitude to achieve visible chest wall vibration was used, and the frequency was set at 8 hertz.Measurements and Main Results: Thirty consecutive breaths during artifact-free tidal ventilation were extracted for each of the 228 electrical impedance tomography recordings. After application of corresponding frequency filters, Vt and V_Osc were calculated. There was a signal at 8 and 16 Hz during nHFOV, which was not detectable during nasal continuous positive airway pressure, corresponding to the set oscillatory frequency and its second harmonic. During nHFOV, the mean (SD) V_Osc/Vt ratio was 0.20 (0.13). Oscillations were more likely to be transmitted to the non-gravity-dependent (mean difference [95% confidence interval], 0.041 [0.025-0.058]; P < 0.001) and right-sided lung (mean difference [95% confidence interval], 0.040 [0.019-0.061]; P < 0.001) when compared with spontaneous Vt.Conclusions: In preterm infants, V_Osc during nHFOV are transmitted to the lung. Compared with the regional distribution of tidal breaths, oscillations preferentially reach the right and non-gravity-dependent lung. These data increase our understanding of the physiological processes underpinning nHFOV and may lead to further refinement of this novel technique.

Evaluation of the Physiological Changes in the Central Airway on Multi-Detector Computed Tomography

BACKGROUND

Most data about the trachea are collected during deep inspiration breath holding (DIBH) using multi-detector computed tomography (MDCT). Images of the physiological changes in the central airway are lacking.

OBJECTIVE

The aim of this study was to explore the physiological changes in the central airway on MDCT during DIBH and deep expiration breath holding (DEBH).

METHOD

The data from 62 patients (38 men and 24 women) who underwent enhanced computed tomography in our hospital were collected. Patients were grouped according to sex and age (18-45, 46-60, and >61 years). Anteroposterior diameter (APD) and transverse diameter (TD) at 3 levels (cricoid, intrathoracic inlet, and 2 cm above the carina), tracheal length, bronchial length, and subcarina angle (SCA) were measured.

RESULTS

The average length of the trachea from the cricoid cartilage to the carina was 103.91 ± 10.37 mm at DEBH and 108.63 ± 11.31 mm at DIBH (p < 0.001). The APD of the trachea at the level of the cricoid, intrathoracic inlet, and 2 cm above the carina showed no differences between DEBH and DIBH. The TD of the trachea at the level of the cricoid, intrathoracic inlet, and 2 cm above the carina showed no differences between DEBH and DIBH. The average length of the right main bronchus during DEBH and DIBH was measured as 13.21 ± 3.60 and 13.24 ± 3.49 mm, respectively (p = 0.956). The average length of the left main bronchus at DEBH and DIBH was measured as 44.19 ± 5.50 and 44.27 ± 5.11 mm, respectively (p = 0.929). The average SCA was 81.74 ± 14.56 at DIBH, while it was 80.53 ± 14.38 at DEBH. The change in SCA between DIBH and DEBH showed no significant difference (p = 0.642).

CONCLUSIONS

The APD at the level of the intrathoracic inlet is larger than that at the cricoid and 2 cm above the carina, while the TD is the opposite. These findings about the trachea and bronchus in our study may contribute to bronchoscopy examinations, tube applications, stent design, and stenting.

Clinical and structural aspects of tracheal stenosis and a novel embryological hypothesis of left pulmonary artery sling

OBJECTIVES

To identify the imaging features peculiar to congenital tracheal stenosis (CTS) complicated with left pulmonary artery sling (LPAS) with the aim of presenting a hypothesis of tracheal stenosis embryology in LPAS.

METHODS

We retrospectively reviewed CTS patients (with complete cartilaginous rings) admitted between April 2010 and July 2018. All the patients were classified into the LPAS or non-LPAS group, and their clinical characteristics and qualitative variables on computed tomography (CT) imaging were compared.

RESULTS

Of the 72 patients enrolled, 61 had bilateral lungs. Among the bilateral lung patients, 26 (43%) had LPAS. The tracheal bifurcation was significantly deeper, the stenotic region was longer, and the bronchial angle (especially in the right) was wider, in the LPAS group. The cut-off values for the thoracic vertebral level at the tracheal bifurcation (>4.8), subcarinal angle (>118.1), and right bronchial angle (>61.9) were useful for diagnosing suspected cases of LPAS. In the time-dependent course, LPAS complicated with a congenital heart defect was a statistically significant risk factor of respiratory symptoms (hazard ratio, 3.01; 95% confidence interval, 1.23-7.37; P = .02).

CONCLUSIONS

The CT findings described here should immediately raise suspicion of LPAS on chest X-ray and also suggest tracheal "squeezing and milking" by the surrounding vessels in the embryo. Patients with LPAS complicated with a heart defect should be followed carefully to determine the optimal timing of intervention.

Morphologic Analysis of Congenital Heart Disease With Anomalous Tracheobronchial Arborization

BACKGROUND

This study investigated the morphologic characteristics of congenital heart disease (CHD) combined with anomalous tracheobronchial arborization (ATBA) to provide new considerations for surgically treating congenital tracheal stenosis.

METHODS

A retrospective review of surgical experience with ATBA was conducted of 147 patients. The proportion of patients with ATBA combined with tracheal stenosis was determined. Four ATBA types were identified: type A, tracheal bronchus (n = 58); type B, bronchial trifurcation (n = 46); type C, bridging bronchus (n = 38); and type D, tracheal bronchus combined with bronchial trifurcation (n = 5). The rate of tracheoplasty for each type was determined. We measured the carina/pseudocarina angle and assessed the distribution of CHD, especially pulmonary artery sling.

RESULTS

The tracheal diameter of 14 patients (24.1%) with type A and 5 patients (10.9%) with type B was normal. There were 128 patients with tracheal stenosis and complete tracheal rings; of them, 113 patients received tracheoplasty. The tracheoplasty rate was higher for type C than type A (100% vs 62.1%, P < .001). The carina/pseudocarina angle was significantly reduced postoperatively (P < .001). The repair in 78 patients (60.9%) was combined with a pulmonary artery sling. A pulmonary azygos lobe was found in 10 patients (6.8%) and was resected.

CONCLUSIONS

ATBA is common in patients with congenital tracheal stenosis and may be associated with abnormal embryonic development. The new classification of ATBA has clinical significance in treating patients with congenital tracheal stenosis. The poor tracheal development cannot be explained merely with vascular compression. Tracheoplasty is currently the optimal option for every type.

3D-measurement of tracheobronchial angles on inspiratory and expiratory chest CT in COPD: respiratory changes and correlation with airflow limitation

Purpose

To assess tracheobronchial angles and their changes on combined inspiratory and expiratory thoracic computed tomography (CT) scans and to determine correlations between tracheobronchial angles and several indices of chronic obstructive pulmonary disease (COPD).

Materials and methods

A total of 80 smokers underwent combined inspiratory and expiratory CT scans. Of these, 65 subjects also performed spirometry and 55 patients were diagnosed with COPD. On CT scans, 3-dimensinal tracheobronchial angles (trachea–right main bronchus [RMB], trachea–left main bronchus [LMB], and RMB–LMB) were automatically measured by software. Lung volumes at inspiration and expiration were also automatically calculated. Changes in tracheobronchial angles between inspiration and expiration were assessed by the Mann–Whitney test. Correlations of the angles with lung volume, airflow limitation, and CT-based emphysema index were evaluated by Spearman rank correlation.

Results

The trachea–LMB angle was significantly smaller and the RMB–LMB angle was significantly larger at expiration than inspiration (P<0.0001). The trachea–LMB and RMB–LMB angles were significantly correlated with lung volume, particularly at expiration. The RMB–LMB angle was significantly correlated with airflow limitation and CT emphysema index (P<0.001–0.05) at inspiration and expiration, suggesting that narrowed RMB–LMB angle indicates more severe airflow limitation and larger extent of emphysema.

Conclusion

Tracheobronchial angles change during respiration and are correlated with severity of COPD and emphysema.

Tracheobronchial angles in children: Three-dimensional computed tomography-based measurements

BACKGROUND

Studies have shown significant variation in the tracheobronchial angles in pediatric-aged patients. The current study revisits tracheobronchial angle measurements in children using accurate computed tomography-based 3-dimensional images to add clarity to the understanding of tracheobronchial angles. The primary objective of the current study was to measure the right and left bronchial angle take off from the trachea using 3-dimensional computed tomography-based images of the air column in the tracheobronchial tree.

METHODS

Computed tomography-based images of 45 children younger than 8 years were reviewed. The children were evaluated during spontaneous ventilation either during natural sleep or with sedation. The right and left bronchial angles were computed between the central axes of the respective main bronchi and a vertical line passing through the central axis of the longitudinal tracheal air column. The right and left bronchial angles were compared using paired t tests, and the age dependence of the right bronchial angle and left bronchial angle difference was evaluated using Pearson's correlation coefficient.

RESULTS

The study cohort included 18 males and 27 females with an average age of 49 ± 25 months. The right bronchial angle ranged from 23° to 56° (mean 42 ± 7°), whereas left bronchial angle varied between 25° and 68° (mean 43 ± 9°). The difference in means of 1 degree was not statistically significant (95% confidence interval of difference: -1°, 4°; P = .282). No association was found between left and right bronchial angle difference and patient age (r = -.019).

CONCLUSION

According to computed tomography-based 3-dimensional imaging, right and left bronchial angles are virtually identical in children up to 8 years of age, and the difference between right and left bronchial angles does not vary with age in this population.

Lower airway dimensions in pediatric patients-A computed tomography study

BACKGROUND

The aim of this study was to obtain lower airway dimensions in children by means of computed tomography (CT).

METHODS

Chest CT scans from 195 pediatric patients (118 boys/77 girls) aged 0.04-15.99 years were analyzed. Tracheal and bronchial lengths, anterior-posterior and lateral diameters, as well as cross-sectional area were assessed at the following levels: mid trachea, right proximal and distal bronchus, proximal bronchus intermedius, and left proximal and distal bronchus. Mediastinal angles of tracheal bifurcation were measured. Data were analyzed by means of linear and polynomial regression plots.

RESULTS

The strongest correlations were found between tracheal and bronchial diameters and age as well as between tracheal and bronchial lengths and body length. All measured airway parameters correlated poorly to body weight. Bronchial angles revealed no association with patient's age, body length, or weight.

CONCLUSION

This comprehensive anatomical database of lower airway dimensions demonstrates that tracheal and bronchial diameters correlate better to age, and that tracheal and bronchial length correlate better to body length. All measured airway parameters correlated poorly to body weight.