Computational fluid-structure interaction simulation of airflow in the human upper airway

Pirnar, Jernej; Dolenc‐Grošelj, Leja; Fajdiga, Igor; Žun, Iztok

doi:10.1016/j.jbiomech.2015.08.017

Cited by 53 publications

(37 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These geometries may differ from those found at peak flow. Those simulations that do incorporate motion use FSI calculations [18][19][20][21][22][23] and have only modeled passive motion to date, but not neuromuscular motion, and require tissue properties to be determined. As this study and others 24,25,62 have shown, much of the motion in the upper airways may not be passive.…”

Section: Discussionmentioning

confidence: 99%

“…Some studies have employed fluid‐structure interaction (FSI) techniques to model the motion of the airway, but these studies have only modeled passive motion of the airway walls due to pressure forces, taking into account mechanical properties of the structures surrounding the airway, such as Young's modulus, but not the active motion of the muscles surrounding the airway. The patency of the upper airway during breathing is maintained through a balance of muscle tone, neuromuscular activation of the surrounding structures, airway anatomy, external forces such as gravity, and passive response of the airway walls to the flow of air.…”

Section: Introductionmentioning

confidence: 99%

“…However, many airway conditions are characterized by abnormal motion (eg, obstructive sleep apnea [OSA], tracheomalacia, bronchomalacia, laryngomalacia), and therefore static CFD studies are inadequate for assessing the effect motion has on factors such as airway resistance and particle deposition in these conditions. Some studies have employed fluid-structure interaction (FSI) techniques to model the motion of the airway, [18][19][20][21][22][23] but these studies have only modeled passive motion of the airway walls due to pressure forces, taking into account mechanical properties of the structures surrounding the airway, such as Young's modulus, but not the active motion of the muscles surrounding the airway. The patency of the upper airway during breathing is maintained through a balance of muscle tone, neuromuscular activation of the surrounding structures, airway anatomy, external forces such as gravity, and passive response of the airway walls to the flow of air.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A novel method to generate dynamic boundary conditions for airway CFD by mapping upper airway movement with non‐rigid registration of dynamic and static MRI

Bates

Schuh

McConnell

et al. 2018

Numer Methods Biomed Eng

View full text Add to dashboard Cite

Computational fluid dynamics (CFD) simulations of airflow in the human airways have the potential to provide a great deal of information that can aid clinicians in case management and surgical decision making, such as airway resistance, energy expenditure, airflow distribution, heat and moisture transfer, and particle deposition, as well as the change in each of these due to surgical interventions. However, the clinical relevance of CFD simulations has been limited to date, as previous models either did not incorporate neuromuscular motion or any motion at all. Many common airway pathologies, such as obstructive sleep apnea (OSA) and tracheomalacia, involve large movements of the structures surrounding the airway, such as the tongue and soft palate. Airway wall motion may be due to many factors including neuromuscular motion, internal aerodynamic forces, and external forces such as gravity. Therefore, to realistically model these airway diseases, a method is required to derive the airway wall motion, whatever the cause, and apply it as a boundary condition to CFD simulations. This paper presents and validates a novel method of capturing in vivo motion of airway walls from magnetic resonance images with high spatiotemporal resolution, through a novel combination of non-rigid image, surface, and surface-normal-vector registration. Coupled with image-synchronous pneumotachography, this technique provides the necessary boundary conditions for dynamic CFD simulations of breathing, allowing the effect of the airway's complex motion to be calculated for the first time, in both normal subjects and those with conditions such as OSA.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A novel method to generate dynamic boundary conditions for airway CFD by mapping upper airway movement with non‐rigid registration of dynamic and static MRI

Bates

Schuh

McConnell

et al. 2018

Numer Methods Biomed Eng

View full text Add to dashboard Cite

show abstract

“…As no experimental data was available for the soft tissues of the soft palate, material parameters were taken from the literature. For the homogeneous soft tissue model (Table ), parameters describing the overall properties of the soft palate were found in the studies by Birch and Srodon, Pirnar et al, and Yu et al For the layered material model parameters of the soft palate, the material parameters for adipose, glandular, muscular, tendinous, and mucosal tissue were obtained from the works of Kuehn and Kahane, Etterna and Kuehn, Kuehn and Moon, and Cho et al All papers used to describe the parameters are stated in Table . Soft tissues were modelled as hyperelastic whereas bone was modelled as linear elastic.…”

Section: Methodsmentioning

confidence: 99%

“…As no experimental data was available for the soft tissues of the soft palate, material parameters were taken from the literature. For the homogeneous soft tissue model (Table I), parameters describing the overall properties of the soft palate were found in the studies by Birch and Srodon, Pirnar et al, and Yu et al [12][13][14] For the layered material model parameters of the soft palate, the material parameters for adipose, glandular, muscular, tendinous, and The Youngs modulus is the stiffness of the material. The Poisson ratio explains the contraction of the soft tissue material when an external pulling force is being exerted.…”

Section: Fe Modelsmentioning

confidence: 99%

Simulation of the upper airways in patients with obstructive sleep apnea and nasal obstruction: A novel finite element method

Moxness

Wülker

Skallerud

et al. 2018

Laryngoscope Investig Oto

View full text Add to dashboard Cite

ObjectiveTo evaluate the biomechanical properties of the soft palate and velopharynx in patients with obstructive sleep apnea (OSA) and nasal obstruction.Study designProspective experimental study.Materials and methodsTwo finite element (FE) models of the soft palate were created in six patients undergoing nasal surgery, one homogeneous model based on CT images, and one layered model based on soft tissue composition. The influence of anatomy on displacement caused by a gravitational load and closing pressure were evaluated in both models. The strains in the transverse and longitudinal direction were obtained for each patient.ResultsThe individual anatomy influences both its structural stiffness and its gravitational displacement. The soft palate width was the sole anatomical parameter correlated to the critical closing pressure, but the maximal displacement due to gravity may have a relationship to closing pressure of possibly an exponential order. The airway occlusion occurred mainly at the lateral attachments of the soft palate. The total transverse strain showed a strong correlation with maximal closing pressure. There was no relationship between the critical closing pressure and the preoperative AHI levels, or the change in AHI after surgery.ConclusionHyperelastic FE models both in the homogeneous and layered model represent a novel method of evaluating soft tissue biomechanics of the upper airway. The obstruction occurs mainly at the level of the lateral attachments to the pharyngeal wall, and the width of the soft palate is an indicator of the degree of critical closing pressure. A less negative closing pressure corresponds to small total transverse strain. The effect of nasal surgery on OSA is most likely not explained by change in soft palate biomechanics.Level of EvidenceNA.

show abstract

Effect of upper airway on tracheobronchial fluid dynamics

Kim

Collier

Wild

et al. 2018

Numer Methods Biomed Eng

View full text Add to dashboard Cite

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.

show abstract

Computational fluid-structure interaction simulation of airflow in the human upper airway

Cited by 53 publications

References 27 publications

A novel method to generate dynamic boundary conditions for airway CFD by mapping upper airway movement with non‐rigid registration of dynamic and static MRI

A novel method to generate dynamic boundary conditions for airway CFD by mapping upper airway movement with non‐rigid registration of dynamic and static MRI

Simulation of the upper airways in patients with obstructive sleep apnea and nasal obstruction: A novel finite element method

Effect of upper airway on tracheobronchial fluid dynamics

Contact Info

Product

Resources

About