The Clinical Study On The Relationship Between Adult OSA And Craniofacial And Upper Airway Morphological Structure And On The Outcome Evaluation Of Orthognathic Surgery

Background and objectivesObstructive sleep apnea(OSA)is a sleep-related breathing disorder characterized by recurrent episodes of partial or complete upper-airway obstruction during sleep.It is associated with oxygen desaturations and sleep fragmentments.The World Health Organization estimates that 100 million individuals worldwide have OSA,and that up to 90%remain undiagnosed and untreated.OSA poses a serious threat to general health and is an important public health problem worldwide.A large number of OSA patients are in urgent need of effective treatment.The etiology of OSA is complex and its diagnosis and treatment involves many disciplines.The craniofacial complex is an important component of the upper airway bone structure,and anatomical structures such as the maxilla.mandible,upper and lower dentition.and hyoid bone affect the size of the inherent oral space and the morphology and function of the upper airway.3D reconstruction,measurement and analysis techniques of craniofacial and upper airway,and orthodontics and orthognathic surgery techniques in dental discipline give dentists/oral health providers a unique advantage in exploring the anatomical risk factors of OSA and participating in the multidisciplinary diagnosis and treatment of OSA.Dentists/oral health providers also have the responsibility to shoulder the mission of maintaining the physiological health of patients’ upper airway.With the emergence and development of dental sleep medicine,it has become a scientific and clinical need to incorporate OSA into oral practice.This study will focus on the relationship between adult OSA and craniofacial and upper airway morphology and the outcome evaluation of orthognathic surgery,and carry out a series of clinical studies to supplement the current knowledge of dentists/oral health providers,to fully explore their role in screening OSA and potential in improving upper airway respiratory physiology and to provide a theoretical basis for dentists/oral health providers to participate in OSA multidisciplinary diagnosis and treatment and to carry out oral therapy that is beneficial to upper airway physiology.Materials and methods1.The morphologic study of craniofacial and upper airway in adult OSA.The samples in this study consisted of 95 adult OSA patients referred from Key Laboratory of Otorhinolaryngology,National Health Commission Shandong University)to the orthodontic clinic of Stomatology Hospital of Shandong University between June 2017 to August 2020.All patients underwent an overnight PSG recoding and a CBCT scanning.Three-dimensional craniofacial and upper airway anatomical analysis were performed using 12 CBCT variables,including sagittal and vertical j aw relationships,maxillary width,the volume,length,minimum axial area of upper airway and the cross-sectional shape.The severity of OSA was evaluated through the apnea-hypopnea index(AHI).A hierarchical regression was performed to analyze the relationship between OSA severity and craniofacial and upper airway anatomical variables after controlling patients’ demographic characteristics(gender,age.and BMI).2.The computional fluid dynamics study based on upper airway morphology in adult OSA.The subjects were recruited from the first part of the study until January 2022,which included 97 patients with OSA under the new inclusion and exclusion criteria.All patients had polysomnography and CBCT data.The upper airway models were reconstructed based CBCT images,which were used to evaluate the morphological characteristics.Computational fluid dynamics(CFD)was carried out to evaluate the hydrodynamic characteristics of the upper airway.Hierarchical regression analysis was used to explore the relationship between upper airway hydrodynamics variables and OSA severity(represented by AHI)after controlling patients’ demographic characteristics(gender,age,and BMI),and curve fitting was used to analyze the correlation between upper airway morphological variables and the most relevant AHI hydrodynamics variables.Pearson Chi-square test was used to analyze whether the distribution of OSA patients with different severity was different in samples with In-Vmax>4 m/s or<4 m/s.3.Effects of orthognathic surgery on upper airway morphology and function in patients with severe skeletal class Ⅱ and OSA and screening of key factors.This study included 16 patients with severe skeletal class Ⅱ and OSA who underwent combined orthodontic-orthognathic surgery at the orthodontic clinic of Stomatology Hospital of Shandong University from September 2019 to March 2022.All patients underwent mandibular bilateral sagittal split osteotomy advancement surgery,whose cephalometric radiography,CBCT and polysomnography were performed before and at least 6 months after surgery.Cephalogram radiographs and CBCT were used to measure and analyze the morphological changes of craniofacial skeletal and soft tissue and upper airway before and after surgery.The respiratory function during sleep of patients before and after surgery was evaluated by polysomnography.Paired t test or Wilcoxon signed rank test were used to compare outcome variables before and after surgery and the changes of each index were analyzed.Pearson correlation coefficient was calculated to determine the correlation between changes in craniofacial and upper airway variables and changes in AHI.4.The study of the upper airway mechanical mechanism of patients with severe skeletal class Ⅱ and OSA treated by orthognathic surgery.The subject was a patient severe skeletal class II and OSA from the third part of the present study.Based on CBCT images,three-dimensional reconstruction of the upper airway and oropharyngeal airway wall models of the patient before and after surgery was done,and then fluid-structure interaction simulation was conducted to evaluate the changes in airflow characteristics inside the upper airway and the deformation of oropharyngeal flexible airway wall before and after orthognathic surgery.Results1.In the study of three-dimensional craniofacial and upper airway morphology of OSA patients,the inclusion of CBCT variables(representing craniofacial and upper airway morphology)can increase the explanatory ability of regression model for AHI variation.The retropalatal airway length(L-RPA)and the mandibular body length(Go-Me)were significant predictors of AHI.After controlling the demographic characteristics(gender,age.and body mass index)of the patients,four CBCT variables were detected to be significantly correlated with AHI.namely,minimum axial area(MAA),the volume of retroplatal airway(V-RPA),L-RPA and Go-Me.We finally added MAA,L-RPA and Go-Me into the final hierarchical regression analysis model.and the results showed that the addition of CBCT variable increased the explanatory ability of the model to AHI variation by 0.102,which was statistically significant(ΔF(3.88)=5.176,P=0.002).Among these CBCT variables.L-RPA,Go-Me and AHI were significantly correlated(P<0.05).2.In the study of upper airway hydrodynamics in OSA patients,the inclusion of the maximum velocity during inspiration(In-Vmax)led to the largest increase in the explanatory power of AHI variation and the varible correlated closely with minimum axial area(MAA).After controlling the demographic characteristics(gender,age.and body mass index)of the patients,the inclusion of the maximum velocity during inspiration(In-Vmax)led to the largest increase in the explanatory power of AHI variation,with an increase of 0.08 7(F(4.92)=15.778.P<0.001).Moreover.In-Vmax showed a stronger correlation with AHI than correlations between anatomical variables with AHI.In-Vmax correlated closely with minimum axial area(MAA)and their relationship was represented by an inversely proportional fitted curve(In-Vmax=67.88 × MAA-0.75,R2=0.944).In the samples with In-Vmax>4 m/s or<4 m/s,the Pearson Chi-square test P value of the distribution of OS A patients with different severity was<0.001,suggesting that patients were more likely to be diagnosed with severe OS A when In-Vmax>4 m/s。3.After orthognathic surgery of severe skeletal class Ⅱ patients accompanied with OSA,the upper airway dimensions significantly increased and PSG parameters related to respiration significantly improved,and the change of Go-Me showed a significant correlation with the change of AHI.The mean increase of mandibular body length(Go-Me)was 10.63 mm after orthognathic surgery.The mean advancements of B-point and pogonion were 6.31 mm and 10.45 mm respectively.After surgery,Pog’-TVL and C-Gn’indicating soft tissue protrusion of mandible and chin significantly increased(P<0.001).And the minimum axial area(MAA)significantly increased from 91.20(IQR 82.85,114.65)mm2 to 134.50(IQR 109.10,176.30)mm2(P<0.001),sRDI decreased significantly from 12.95(IQR 8.30.25.58)times/hour to 7.90(IQR 5.10,11.23)times/hour(P=0.002).The mean LSAT significantly increased after surgery(P=0.028).The change of Go-Me showed a significant correlation with the change of AHI(r=0.603,P=0.013).Furthermore,the change of Pog’-TVL and C-Gn’ also showed significant correlations with the change of AHI(r=-0.663,P=0.005;r=-0.589,P=0.016).4.The results of fluid-structure interation simulation showed that after orthognathic surgery,the internal airflow characteristics of the upper airway and the deformation of the oropharyngeal airway wall improved in patients with severe skeletal class Ⅱ and OSA,which was consistent with the patient’s clinical response.Pre-surgical FSI simulation showed that in the early inspirations(t=0.56 s),the anterior wall collapse resulted in partial obstruction of the upper airway,which was located in the retropalatal airway,and the maximum mesh displacement was 5.152 mm.After the surgery,a whole inspiration cycle could be completed smoothly(t=2 s),the deformation of the airway wall was significantly reduced,and the maximum mesh displacement was 2.707 mm.Compared with the pre-surgical results,the post-surgical airflow velocity in the upper airway decreased(6.769 n/s to 3.749 m/s),the minimum wall static pressure increased(-40.51 Pa to27.50 Pa),and the maximum wall shear stress decreased(1.676 Pa to 0.459 Pa).The pressure drop in the oropharyngeal airway decreased(21.34 Pa to 2.93 Pa).The AHI value of this patient decreased from 28.4 times/hour to 9.2 times/hour after surgery and the LSAT increased from 80%to 90%.The FSI results showed improved fluid flow characteristics and less-deformable airway wall,and revealed a positive response which matched the clinical treatment.Conclusions1.Three-dimensional craniofacial and upper airway morphology played an essential role in OSA severity.The most relevant anatomical characteristic with OSA severity were the length of retropalatal airway and mandibular body.The mandibular body length was a significant predictor of OSA severity,confirming the direct etiological role of craniofacial morphological abnormalities in OSA.2.After controlling for gender,age,and body mass index,the maximum velocity during inspiration(In-Vmax)was the most relevant aerodynamic characteristic of the upper airway related to OSA severity,was significant inversely related to mimimum axial area(MAA)of the upper airway.Patients were more likely to be diagnosed with severe OSA when In-Vmax>4 m/s.3.The orthognathic surgery improved the profile esthetics,increased upper airway dimensions and improved the respiratory function during sleep significantlt for patients with severe skeletal class Ⅱ accompanied with OSA.The increase of the mandibular body length was the key factor for the favorable changes of respiratory function during sleep,which echoed and verified the conclusions of the first part,confirming the importance of mandibular body size in maintaining the respiratory physiological function of the upper airway once again.4.Orthognathic surgery can expand the space of the posterior airway by relocating the abnormal craniofacial structure in the patient with severe skeletal class Ⅱ and OSA,improve the airflow characteristics in the upper airway and reduce the incidence of airway collapse,thus showing improvement in respiratory physiology.