Effect of upper airway on tracheobronchial fluid dynamics

Abstract

The upper airways play a significant role in the tracheal flow dynamics. Despite many previous studies, however, the effect of the upper airways on the ventilation distribution in distal airways has remained a challenge. The aim of this study is to experimentally and computationally investigate the dynamic behaviour in the intratracheal flow induced by the upper respiratory tract and to assess its influence on the subsequent tributaries. Patient-specific images from 2 different modalities (magnetic resonance imaging of the upper airways and computed tomography of the lower airways) were segmented and combined. An experimental phantom of patient-specific airways (including the oral cavity, larynx, trachea, down to generations 6-8) was generated using 3D printing. The flow velocities in this phantom model were measured by the flow-sensitised phase contrast magnetic resonance imaging technique and compared with the computational fluid dynamics simulations. Both experimental and computational results show a good agreement in the time-averaged velocity fields as well as fluctuating velocity. The flows in the proximal trachea were complex and unsteady under both lower- and higher-flow rate conditions. Computational fluid dynamics simulations were also performed with an airways model without the upper airways. Although the flow near the carina remained unstable only when the inflow rate was high, the influence of the upper airways caused notable changes in distal flow distributions when the 2 airways models were compared with and without the upper airways. The results suggest that the influence of the upper airways should be included in the respiratory flow assessment as the upper airways extensively affect the flows in distal airways and consequent ventilation distribution in the lungs.

Inhalation Health Risk Assessment for the Human Tracheobronchial Tree under PM Exposure in a Bus Stop Scene

“…The experimental models only contained trachea and bronchial airways, and do not include an oral or nasal cavity. It was suggested that the upper airways affected the flow and ventilation distribution in the distal airways (Kim et al, 2018). Overall our results for particle deposition in trachea were reasonable.…”

“…Most of these airway models only contained trachea and the upper bronchial tree airways. However, Kim et al (2018) suggested that upper airways affected the flow and ventilation distribution in the distal airways. It was essential to utilize a complete respiratory airway to better understand the particle deposition distribution in lung bifurcations.…”

Bench Assessment of the Effect of a Collapsible Tube on the Efficiency of a Mechanical Insufflation-Exsufflation Device

“…Finally, the upper airways could be directly, dynamically, and noninvasively assessed during the MI-E procedure with modern imaging techniques. 30 In conclusion, we found that PEF was higher with a collapsible tube than without a collapsible tube at all respiratory mechanics profiles tested.…”

Computational investigation of prolonged airborne dispersion of novel coronavirus-laden droplets

“…We performed simulations for four cases (Re = 1000 and RH = 30%, Re = 1000 and RH = 60%, Re = 1000 and RH = 90%, and Re = 2000 and RH = 60%). Considering the low Reynolds number conditions, the use of fine meshes, and the relationship between the time required for a cough (i.e., 0.5 s) and the whole simulation time (i.e., 90 min), we applied the laminar flow model ( Kim et al, 2018 ; Zhang & Kleinstreuer, 2002 ) to the simulations. Additionally, we assumed that the flow field was isothermal.…”