Three Dimensional Reconstruction and Airflow Simulation in a Realistic Model of the Human Respiratory Airways

Respiratory tract diseases are a common cause of medical consultation. Indeed, most of this patients need an adequate treatment to improve their airway conditions. In order to understand how the airflow works through the lower airway and how disease condi

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Bioinstrumentation and Clinical Engineering Research Group - GIBIC, Bioengineering Department, Engineering Faculty, Universidad de Antioquia UdeA; Calle 70 No. 52-21, Medellín, Colombia

Abstract— Respiratory tract diseases are a common cause of medical consultation. Indeed, most of this patients need an adequate treatment to improve their airway conditions. In order to understand how the airflow works through the lower airway and how disease condition may affect it, this paper presents an airflow simulation based on a three dimensional model from a real human airway constructed from a Computed Tomography scan. Methodology used to perform the simulation, include the implementation of Materialise’s medical image software R MIMICS (v. 18.0), in order to segment the lower airway using region based segmentation procedures. Moreover, a computational fluid dynamic simulation was carried out by R using the finite element software Comsol (v. 5.2); to this end, this paper shows a comprehensive workflow integrating both software to obtain a realistic airflow simulation through the lower airway. Velocity and pressure profiles are presented to assess the effectiveness of the simulation, showing a parabolic non-compressive flow and high pressure in complex anatomical geometric areas, validating the expected physiologic behavior. Keywords— Human lower computational fluid dynamics

airway,

realistic

model,

I. I NTRODUCTION Human respiratory system is a complex structure consisting of two main anatomical divisions: upper airways and lower airways, whose primary function is oxygen supply to the body cells and removing carbon dioxide, through a process called gas exchange [1]. Lower airways geometry is not homogeneous due to peculiarities in its own structure, as anatomical constriction zones, asymmetric branching patterns, distinct radius of curvatures and constant change of branching angles and orientation; which generate rapid changes in the flow direction [2]. Therefore, it is necessary to carry out different analysis to allow understanding flow behaviour within the airway under different conditions including normal physiologic function [3–5], particle deposition [4], [6], some pathologies as obstructive sleep apnea [7] and congenital glottic web [8]

and situations under mechanical ventilation [9–11]; in the latter case, this is a procedure that can involve multiple complications such as airway edema, bleeding, obstruction, collapse, respiratory failure and arrest [12]. For this purpose, Computational Fluid Dynamics (CFD) simulation has been widely applied [2–9, 13–15], since fluid flow characteristics can be predicted in detail, under controlled conditions and noninvasive way. Nevertheless, some of these works have been performed in idealized and simplified models of human airways defined by only diameters and lengths of cylindrical structures. In these cases, particularities derived from asymmetry are ignored and the complexity of real airway is not considered. In this paper an airflow simulation in a realistic model of the human respira