Simulation of Pharyngeal Airway Interaction with Air Flow Using Low-Re Turbulence Model

Abstract

This paper aims to simulate the interaction between a simplified tongue replica with expiratory air flow considering the flow in the pharyngeal airway to be turbulent. A three-dimensional model with a low-Re SST turbulence model is adopted. An Arbitrary Eulerian-Lagrangian description for the fluid governing equation is coupled with the Lagrangian structural solver via a partitioned approach, allowing deformation of the fluid domain to be captured. Both the three-dimensional flow features and collapsibility of the tongue are presented. In addition, examining initial constriction height ranging from 0.8 mm to 11.0 mm and tongue replica modulus from 1.25 MPa to 2.25 MPa, the influence of both of these parameters on the flow rate and collapsibility of the tongue is also investigated and discussed. Numerical simulations confirm expected predisposition of apneic patients with narrower airway opening to flow obstruction and suggest much severe tongue collapsibility if the pharyngeal flow regime is turbulent compared to laminar.

Numerical and Experimental Analysis of Inhalation Airflow Dynamics in a Human Pharyngeal Airway

“…Further downstream an additional but larger recirculation is formed downstream of the narrowest site of the airway at the level of epiglottis (label C). These separation points and large flow gradients give rise to high susceptibility for airway collapse since it correlates with sharp pressure gradients [29,30]. However, more detailed flow features such as secondary flow vortices could not be revealed here, but it will be shown numerically later.…”

“…The posterior wall is bounded by a muscular wall, while the lateral pharyngeal wall is a complex composition of muscle, lymphoid tissue, and pharyngeal mucosa. In combination, considering the venturi effect, the surrounding tissue composition and their biomechanical properties, strong possibility of airway constriction by the collapse of the tongue and soft palate onto the posterior muscular wall is anticipated [29,30,32].…”

Computational fluid dynamics simulation of the upper airway response to large incisor retraction in adult class I bimaxillary protrusion patients

“…Therefore, a 3D fluid-structure interaction simulation of the upper airway, which considers the interaction between the airflow and around soft tissues, is needed to assess the functional changes of the upper airway272829. Another limitation is that the OSAS occurs during sleeping, when the upper airway dilator muscles andrespiratory pump muscles are less activated thus cannot adjust the shape and posture of the soft tissues.…”

A combined planning approach for improved functional and esthetic outcome of bimaxillary rotation advancement for treatment of obstructive sleep apnea using 3D biomechanical modeling

“…Narrow and mechanically compliant airway walls cause turbulences in pharyngeal airflow that, in turn, exert negative pressure on soft tissue walls resulting in their further collapse [ 19 ]. Bimaxillary advancement is capable to efficiently widen constricted airways, especially in the velopharyngeal region, which reduces the risk of irregular jet-like airflow [ 20 , 21 ]. In the absence of reliable tools for individual planning of bimaxillary advancement, surgeons tend to undertake maximal admissible bone displacement to achieve a therapeutically sufficient extension of the constricted pharyngeal regions.…”