Turbulent Kinetic Energy of Flow during Inhale and Exhale to Characterize the Severity of Obstructive Sleep Apnea Patient

This paper aims to investigate and present the numerical investigation of airflow characteristics using Turbulent Kinetic Energy(TKE)to characterize the upper airway with obstructive sleep apnea(OSA)under inhale and exhale breathing conditions.The importance of TKE under both breathing conditions is that it showan accuratemethod in expressing the severity of flow in sleep disorder.Computational fluid dynamics simulate the upper airway’s airflow via steady-state Reynolds-averaged Navier-Stokes(RANS)with k–ωshear stress transport(SST)turbulencemodel.The three-dimensional(3D)airway model is created based on the CT scan images of an actual patient,meshed with 1.29 million elements using Materialise Interactive Medical Image Control System(MIMICS)and ANSYS software,respectively.High TKE were noticed around the region after the necking(smaller cross-sectional area)during the inhale and exhale breathing.The turbulent kinetic energy could be used as a valuablemeasure to identify the severity of OSA.This study is expected to provide a better understanding and clear visualization of the airflow characteristics during the inhale and exhale breathing in the upper airway of patients for medical practitioners in the OSA research field.

Computational Analysis of Airflow in Upper Airway under Light and Heavy Breathing Conditions for a Realistic Patient Having Obstructive Sleep Apnea

Background:Obstructive sleep apnea is a sleeping disorder that has troubled a sizeable population.There is an active area of research on obstructive sleep apnea that intends to better understand airflow behaviors and therefore treat patients more effectively.This paper aims to investigate the airflow characteristics of the upper airway in an obstructive sleep apnea(OSA)patient under light and heavy breathing conditions by using Turbulent Kinetic Energy(TKE),an accurate method in expressing the flow concentration mechanisms of sleeping disorders.It is important to visualize the concentration of flow in the upper airway in order to identify the severity level of the obstruction during sleep.Methods:Computational fluid dynamic(CFD)analysis was used as a solution tool to evaluate the airflow during light and heavy breathing conditions.A medical imaging technique was used to extract the 3D model from the CT scan images.Additionally,mesh generation and simulation were carried out via CFD software to evaluate the light and heavy breathing characteristics related to obstructive sleep apnea.Steady state Reynold’s averaged Navier-Stoke(RANS)with the k-ωshear stress transport(SST)turbulence model was utilized.The airflow characteristics were quantified using parameters such as pressure distribution,skin friction coefficient,velocity profile,Reynolds number,turbulent Reynolds number and turbulence kinetic energy.Results:Contour plots at different planes were used to visualize the airflow distribution as it passed through different cross-sectional areas of the airway.The results revealed that the presence of a smaller cross-sectional area of the airway caused an increase in airflow parameters,especially during heavy breathing.Furthermore,turbulent airflow conditions along the airway were noticed during heavy breathing.The severity of OSA could be measured by the turbulent kinetic energy which is able to show the behavior and concentration of mean flow.This study is expected to provide crucial and important results by visualizing the concentration of airflow mechanisms and characteristics of a patient’s airway during light and heavy breathing. These findings enable TKE to be used as a new tool for characterizing theseverity of obstructive sleep apnea in the upper airways of patients.