Airflow in Tracheobronchial Tree of Subjects with Tracheal Bronchus Simulated Using CT Image Based Models and CFD Method
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Tracheal Bronchus (TB) is a rare congenital anomaly characterized by the presence of an abnormal bronchus originating from the trachea or main bronchi and directed toward the upper lobe. The airflow pattern in tracheobronchial trees of TB subjects is critical, but has not been systemically studied. This study proposes to simulate the airflow using CT image based models and the computational fluid dynamics (CFD) method. Six TB subjects and three health controls (HC) are included. After the geometric model of tracheobronchial tree is extracted from CT images, the spatial distribution of velocity, wall pressure, wall shear stress (WSS) is obtained through CFD simulation, and the lobar distribution of air, flow pattern and global pressure drop are investigated. Compared with HC subjects, the main bronchus angle of TB subjects and the variation of volume are large, while the cross-sectional growth rate is small. High airflow velocity, wall pressure, and WSS are observed locally at the tracheal bronchus, but the global patterns of these measures are still similar to those of HC. The ratio of airflow into the tracheal bronchus accounts for 6.6–15.6% of the inhaled airflow, decreasing the ratio to the right upper lobe from 15.7–21.4% (HC) to 4.9–13.6%. The air into tracheal bronchus originates from the right dorsal near-wall region of the trachea. Tracheal bronchus does not change the global pressure drop which is dependent on multiple variables. Though the tracheobronchial trees of TB subjects present individualized features, several commonalities on the structural and airflow characteristics can be revealed. The observed local alternations might provide new insight into the reason of recurrent local infections, cough and acute respiratory distress related to TB.
KeywordsTracheal bronchus The tracheobronchial tree Computational fluid dynamics Airflow CT scan
Chronic obstructive pulmonary disease
Computational fluid dynamics
Left lower lobe
Left upper lobe
Pulmonary function tests
Right lower lobe
Right middle lobe
Right upper lobe
The authors also acknowledge Mr. Paul Young for his helpful language editing.
SQ: proposed the idea, performed experiments, analyzed the data, made discussions and composed the manuscript together with BZ, YT. YY and JS: provided CT images and radiology instruction, and made the discussions. WQ and JW: directed the experiments and made discussions. All authors read and approved the final manuscript.
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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