| Objective:The biomechanical numerical simulation was used to study the characteristics of the typical different obstruction planes on the upper airway airflow field in OSAHS patients,as well as the movement of the soft palate with certain compliance in the soft tissue of the pharyngeal wall of OSAHS patients in different positions and the degree of pharyngeal airway obstruction.And a preliminary simulation study on the collapse of the oropharyngeal wall was carried out;with a view to expand the understanding of the pathogenesis of OSAHS from the perspective of biomechanical numerical simulation.Method:Endoscopy,nasal（pharyngeal）acoustic reflex,and PSG were used to select 3 cases of severe OSAHS patients with typical different obstruction planes.They are nasal airway stenosis（nasal septal deviation,bilateral inferior turbinate unequal hypertrophy）,oropharyngeal airway stenosis（both tonsilsⅢ?）,nasal airway stenosis and oropharyngeal airway stenosis patients,and obtained Airway CT data,using Mimics 20.0,Geomagic Studio 12.0,3D finite element model reconstruction of upper airway thin scan CT image data of 3 severe OSAHS patients with different obstruction planes;using Ansys Workbench software to perform 3D finite element model of upper airway,setting of entrance and exit planes,grid division,quality inspection,setting air flow to 600ml,and giving corresponding boundary conditions,calculation and analysis of upper airway air flow field of OSAHS patients before operation.Using Mimics 20.0,Geomagic Studio 12.0 on airway reconstruction of the upper airway of an additional part of the oral airway,the soft palate,oropharyngeal wall model,Boolean combinations the upper airway of an additional part of the oral airway and the soft palate,upper airway and oropharyngeal wall,Ansys Workbench software perfect meshing and inspection,set to the additional part of the oral airway airway relevant boundary conditions,respectively assignment（including the soft palate accessory muscles）,the soft palate oropharyngeal wall elastic modulus,poisson’s ratio;Fixed the soft palate and the free end of the hard palate junction and affiliated muscle,simulation gives the soft palate supine and side-lying position（left,right）and Zuo Wei Ti condition to the earth’s gravity parameters,and the counterpart to pharyngeal model up and down side and front wall after your tongue,soft palate and pharyngeal wall fixed sewing parts,use of fluid-solid coupling operation of the soft palate respectively under the different position of moving range and oropharyngeal wall collapse for preliminary numerical simulation research.Use Ansys Workbench software to improve the meshing and inspection,set the upper airway-related boundary conditions of the upper airway of an additional part of the oral airway,and assign the elastic modulus and Poisson’s ratio of the soft palate（including the soft palate muscles）,oropharyngeal wall;Fix the free end of the soft palate and the hard palate and the free ends of the attached muscles,simulate the gravity parameters given to the soft palate in the supine,lateral（left,right）,and sitting positions,the upper and lower ends of the oropharyngeal wall model and the anterior wall of the tongue base,soft palate and pharyngeal suture were fixed,and the fluid-solid coupling calculation was used to carry out preliminary numerical simulations of the movement amplitude of the soft palate in different positions and the collapse of the oropharyngeal side wall.Outcomes:1.Combined with the pressure cloud diagram,flow velocity vector diagram,flow form distribution diagram and the average distribution table of pressure and flow velocity in each section of the upper airway related to the exhalation and inhalation of the upper airway flow field.Different to the typical block plane in OSAHS patients with airway flow in a multi-angle,intuitive analysis.It was found that in 3 patients with OSAHS,the changes in upper airway nasal threshold pressure drop,nasal resistance and oropharyngeal cross-sectional pressure have certain characteristics,including cases:（1）Case 1 is an OSAHS patient with nasal airway stenosis:there is greater resistance in the nasal airway,the pressure drop in the nasal threshold is relatively small,and the location of the upper middle airway medium pressure and the largest change in flow rate is located in the oropharynx;The inspiratory nasal airway resistance was 0.775 k Pa·s·L-1,and the pressure drop in the nasal threshold and oropharynx were-11.7 Pa and-209 Pa,respectively;（2）Case 2 was a patient with pharyngeal airway stenosis:The nasal resistance and the pressure drop in the nasal threshold area are large,and the pressure and flow rate of the oropharynx in the upper airway are the most obvious.The inspiratory nasal airway resistance is 0.71 k Pa·s·L-1,the nasal threshold area The pressure drop in the oropharynx is-27.4 Pa and-70 Pa respectively;（3）Case 3 is an OSAHS patient with narrow nasal cavity and oropharynx:the nasal resistance is greater,the pressure drop in the nasal threshold area changes less,and the upper air The pressure and flow velocity of the oropharynx are the most obvious in the whole tract;the inspiratory nasal airway resistance is0.835k Pa·s·L-1,and the pressure drop in the nasal threshold and oropharynx are-16.8Pa and-261 Pa respectively.2.The soft palate numerical simulation results show that the amplitude of soft palate movement in patients with OSAHS differs according to the position.Among them,the supine position has the largest movement range,and the displacement of the free edge of inspiratory and expiratory uvula is 1.50cm and 1.18cm respectively;The lateral and sitting positions are smaller than those in the supine position,and the displacement of the free edge of inspiratory and expiratory uvula in the left lateral position is 0.56 cm and 0.40 cm,respectively;The displacement of the free edge of the right lateral inspiratory and exhalation uvula is 0.50cm and 0.40cm respectively;The displacements of the free edges of the inspiratory and expiratory uvula in the sitting position were 0.55 cm and 0.76 cm,respectively.In the left and right lying positions,the movement amplitude on both sides of the soft palate was inconsistent,and the movement amplitude on the near ground side was small.The numerical simulation results of the oropharyngeal wall show that there are local collapsed areas in the posterior oropharyngeal posterior wall of the lingual area,and a preliminary simulation of the collapse of the oropharyngeal side wall was carried out.Conclusion:1.OSAHS patients with stenosis in different parts of the upper airway affectlocal ventilation function,but also affect the ventilation function of other parts of the upper airway:nasal airway stenosis case 1 nasal threshold physiological function and nasal and pharyngeal ventilation function All were reduced;the nasal and pharyngeal airway stenosis cases 2 part of the physiological function of the nasal threshold area was normal,but the nasal and pharyngeal ventilatory functions were reduced;Subside.2.For the first time,from the perspective of biomechanical numerical simulation,we expanded the knowledge and quantitatively compared the movement range of the soft palate with certain compliant positions in OSAHS patients.The degree of airway obstruction in the supine position of the velopharynx was more serious than otherpositions;and the clinical analysis of OSAHS patients in different positions was analyzed.Relevant reasons for the performance of the disease.3.From the perspective of biomechanical numerical simulation,a preliminary visual and quantitative simulation of the compliance of the oropharyngeal sidewallcollapse was carried out,which laid the foundation for the further research application and improvement of the model. |
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