Computational fluid dynamics simulation of changes in the morphology and airflow dynamics of the upper airways in OSAHS patients after treatment with oral appliances.

Baolong Song,Jianwei Sun,Yongming Li,Peng Li,Yibo Li,Yizhe Qi,Zexu Gu,Josué Sznitman

doi:10.1371/journal.pone.0219642

Baolong Song, Jianwei Sun + Show 6 more

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https://doi.org/10.1371/journal.pone.0219642

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Abstract

ObjectivesTo explore the changes of morphology and internal airflow in upper airways (UA) after the use of oral appliances (OAs) in patients with obstructive sleep apnea hypopnea syndrome (OSAHS), and investigate the mechanisms by which OAs function as a therapy for OSAHS.MethodsEight OSAHS patients (all male, aged 37–58, mean age 46.25) underwent CT scans before and after OA use. Then, computational fluid dynamics(CFD) models were built on the base of the CT scans using Mimics and ANSYS ICEM CFD software. The internal airflow of the upper airways was simulated using ANSYS-FLUENT and the results were analyzed using ANSYS-CFD-Post. The data were analyzed to identify the most important changes of biomechanical properties between patients with and without OA intervention. Upper airway morphology and the internal airflow changes were compared using t-tests and Spearman correlation coefficient analysis.ResultsThe narrowest area of upper airways was found to be located in the lower bound of velopharynx, where the volume and pressure were statistically significantly increased (P<0.05) and the air velocity was statistically significantly decreased (P<0.05) in the presence of the OA(P<0.05). After wearing OA, pharyngeal resistance was significantly decreased (P<0.05), from 290.63 to 186.25Pa/L, and the airflow resistance of the pharynx has reduced by 35.9%.ConclusionThe enlargement of the upper airway after wearing the OA changed its airflow dynamics, which decreased the negative pressure and resistance in narrow areas of the upper airways. Thus, the collapsibility of the upper airways was reduced and patency was sustained.

Highlights

The obstructive sleep apnea-hypopnea syndrome (OSAHS) is a common respiratory sleep disorder that is characterized by repeated partial or complete obstruction of upper airway at the end-expiratory phase during sleep [1]
The narrowest area of upper airways was found to be located in the lower bound of velopharynx, where the volume and pressure were statistically significantly increased (P
After wearing OA, pharyngeal resistance was significantly decreased (P

Summary

Introduction

The obstructive sleep apnea-hypopnea syndrome (OSAHS) is a common respiratory sleep disorder that is characterized by repeated partial or complete obstruction of upper airway at the end-expiratory phase during sleep [1]. OSAHS is a highly prevalent disorder which can have serious effects on daily functioning, social life and general health and may even have potentially life-threatening consequences. Prevalence studies estimate that 24% of men and 9% of women in middle age are affected by OSAHS [2]. The prevalence of OSAHS increases with age and in older persons ( 65 years) there is a 2- to 3-fold higher prevalence compared with those in middle age (30–64 years) [3]. There is increasing evidence that untreated OSAHS is associated with ischemic heart disease, arterial hypertension stroke [4,5], hypertension [6], daytime sleepiness, and road traffic accidents [7]. It is recognized that OSAHS is a serious public health problem

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