The Study Of Morphology And Airflow Dynamics In Upper Airway By The Use Of Oral Appliance In OSAHS Patients

Obstructive sleep apnea-hypopnea syndrome(OSAHS) caused by the frequentcollapse and obstruction of the upper airway during sleep, and accompanied byoccurrence of oxygen desaturation. The main clinical manifestations have early morningheadaches, daytime sleepiness, snoring. OSAHS is characterized by episodes of partial orcomplete obstruction of the upper airway during sleep, interrupting (apnea) or reducing(hypopnea) the flow of air. OSAHS is disease of a high incidence and high-impactpatients living standards. In recent years, the reports showed a clear upward trend of theincidence of OSAHS. Common treatment of OSAHS include continuous positive airwaypressure (CPAP), surgery and oral appliance (OA) treatment. OA was widely used in thetreatment of OSAHS for its low price, safety, comfort, easy-making, portable andnon-invasion. The curative effect of OA was affirmed by more and more researchers,however, current research on the specific mechanism of OA for OSAHS mainly confinedto description of morphological. It’s generally believed that after wearing OA for thepatients with OSAHS, the surrounding tissue of the upper airway was pulled out, theupper airway was expanded, so the local stenosis of the upper airway was released ordisappeared. The patients can breath easily and have a higher blood oxygen saturation, alower snoring sound or even without snoring. But what happened to the flow dynamics of the upper airway after wearing the OA is not clear. The research of the dynamics of theupper airway of the patients with OSAHS will conductive to the understanding of therelationship between the morphology of the airway and the function of the airway. It alsohelp the understanding of the pathogenesis of OSAHS and the therapeutic mechanism ofOA.Objective:This study was to stimulate the morphology and the internal flow of the upperairway before and after wearing the OA for the patients with OSAHS under quietbreathing through computational fluid dynamics (CFD). The change of the morphologyand the internal flow of the upper airway was compared and analyzed before and afterwearing the OA. To investigated the mechanism of OA for the treatment of OSAHS andprovide a theoretical for the clinical use of OA.Method:Eight cases of OSAHS patients was collected who met the inclusion criteria, allmale, aged37-58,mean age46.25, mean body mass index24.46kg/cm2. The sufferer ofOSAHS accepted CT scan before and three months after he wore oral appliance. CFDmodel was built on the base of CT scans through Mimics10.01and ANSYS ICEMCFD14.0. The internal flow of upper respiratory tract was simulated byANSYS-FLUENT14.0and the result was analyzed by ANSYS-CFD-Post14.0.The datewere analyzed to find the change between the situations of with and without OA.The change of the morphology and the internal flow of the upper airway wascompared by T-test and Spearman correlation coefficient analysis.Statistical softwareSPSS (version17.0;SPSS Inc.,USA).OutcomesThere was no significant difference(P>0.05) as to the nasopharyngeal area beforeand after wearing OA, but there was an increase for the volume of palate pharynx, tonguepharynx and hypopharynx region(P<0.05), while the major change occurred in thepharyngeal region (increased by39.5%) and glossopharyngeal (increased by44.48%).The most narrowed areas of upper airway were located in the lower bound of pharyngopalatiae, and it has augmented after wearing OA compared with before(P<0.05),it has augmented by129.06%. There was no significant change (P>0.05)for the flow rateat nasopharyngeal and epiglottis region(P<0.05) before and after wearing OA, while theflow rate was apparently decreased at palate pharynx and tongue pharynxregion(P<0.05),especially in the area of narrow airway-lower bound of pharyngopalatiae,the flow rate significantly decreased（P<0.01), it decreased from11.55m/s before to8.81m/s after, which has decreased by23.7%. The pressure did not changesignificantly(P>0.05)at the area of nasopharynx and epiglottis after wearing OA, Whilethe pressure apparently increased at the area of palate pharynx, tonguepharynx(P<0.05),especially the pressure increasing largely at lower bound ofpharyngopalatiae(P<0.01),which has increased from-84.75Pa to-60.87Pa,and thenegative pressure was reduced by28.2%. The resistance of the pharyngeal wassignificant decreased after wearing OA(P<0.05),which has decreased from290.63Pas/Lbefore to186.25Pas/L and the airflow resistance of the pharynx of the patients hasreduced by35.9%. There was a negative relevance between the volume change ofpharynx and AHI change after wearing OA, and the pharyngeal resistance change wassignificant positive correlated with AHI change.ConclusionAfter the patients with OSAHS wearing the OA, the upper airway can be expanded,the airflow dynamics can be changed, the negative pressure at the narrow area of theairway and the resistance of the pharyngeal can be decreased, so as that the upper airwaycan not easy to collapse and at last a smooth airflow can be maintained.