Dissertation > Medicine, health > Otorhinolaryngology > To pharynx Science, pharyngeal disease

Adult OSAHS Preoperative and Postoperative Nasal and Pharynx Cavity and Soft Palate of the Numerical Analysis of Fluid-structure Interaction

Author SunYu
Tutor SunXiuZhen
School Dalian Medical University
Course Otorhinolaryngology
Keywords obstructive sleep apnea structural correction of nasal surgery the numerical simulation fluid-structure interaction
CLC R766
Type Master's thesis
Year 2011
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Objective: To Study the curative effect of Structural correction of nasal surgery of audlt obstructive sleep apnea-hypopnea syndrome patients and the change characteristics of nasal, pharynx cavity and soft palate of the numerical simulation of fluid-structure interaction by applying polysomnogram and three- dimensional finite element numerical simulation.Methods: Apply polysomnogram on 4 cases of adult OSAHS patients to carry out preoperative detection and 3 to 5 monthes postoperative review of Structural correction of nasal surgery;and proceed preoperative and postoperative 5 monthrs later CT scan of the upper airway and its surrounding tissue of 3 patients,lead the 3 patients’preoperative and postoperative imaging data into the mimics software and build three-dimensional model of the human upper airway and soft palate,establish preoperative and postoprative three-dimensional finite element model of 3 cases by applying the ansys finite element analysis software.Study the interaction of the upper airway fluid field and the soft palate movement by applying fluid-structure interaction method, analysis the change characteristics of preoperative and postoperative the upper airway fluid field and soft palate solid field of adult OSAHS patients.Results:1.Polysomnogram Monitoring(PSG):For case 1 and 2,in 3 to 5 monthes after the surgery, AHI turns to be simple snore from mild-moderate,sleep apnea, hypoventilation and other relevant symptoms disappear mainly,operative effect is cured; for case 3 and 4,AHI is decreased 24.7% and 9% respectively 5 months after the surgery,there is no obvious improvement of OSAHS symptom, operative effect is invalid. 2. Measurement of Three-Dimensional Rebuilt Model: Nasal airways of patients in these 3 cases have been widened obbiously.3. Fluid-Solid Coupling Numerical Simulation Result:Pressure Field: For case 1and 2,pressure distribution trend of nasal cavity of both sides in inspiratory period is different before the surgery,pressure difference from the anterior narits to the front of middle meatus ,deviation side is relatively larger than that of contralateral sides,and pressure gradient has changed sharply;for case 3,nasal cavity pressure distribution trend of both sides in inspiratory period is similar before the surgery,but is different from that of normal nasal cavity.After surgery,the 3 paitents’two sides nasal cavity pressure distribution trend and the pressure difference is similar,and primary pressure difference is focused on the limen nasi,postoperative pressure difference from anterior narits to Nasopharynx is decreased.Velocity Field: For case 1and 2,the maximum velocity in the soft palate back area airflow is reduced after surgery;for case 3,its has been increased.Shear Stress at the Wall: For case 1,there are three higher shear stress at the wall areas appeared on the upper airway before and after the surgery:near to the limen nasi,the Velopharyngeal area,glottic area,but after the surgery,the highest shear stress at the wall has been reduced; the change trend of shear stress at the wall near the Velopharyngeal area has been slowed down;nasal cavity shear stress at the wall distribution trend of both side is different before the surgery,but become similar after the surgery;for case 3,there are three high wall shear stress areas on the upper airway before the surgery:area from the limen nasi back to the front of middle meatus,area near to the Velopharyngeal area and glottic area,and the highest shear stress at the wall appeared near to the Velopharyngeal area;but after the surgery,the highest shear stress at the wall only appeared near the Velopharyngeal area,which has been increased. Soft Palate Displacement Field: For case 1 and 2,Uvula tip’displacement has been reduced after the surgery;for case 3,its has been enlarged.Conclusion:1.The study in this section,we believe that the OSAHS patients whose mainly block plane is structural abnormalities of the nasal cavity(Including the adenoidal), surgery on the nasal obstruction flat,expanding the volume of nasal airway,removing nasal obstruction plane, to be an effective method to treatment of OSAHS.2.For multiple upper airway obstruction plane, nose, throat plane, the Velopharyngeal plane,such as case 3 and 4,after the surgery the Nasal airway is widened,the treatment on the nasal obstruction plane is effective. But according to the nasal airway more“smooth”,there may be more higher pressure difference in the Velopharyngeal area,which will increase the movement range of the soft palate,the treatment of OSAHS is negative,and the treatment needs to improve.3.It is necessary to study OSAHS through numerical simulation method and carry out preoperative personalized assessment for choosing of its treatment;it provides quantitative and analyzable platform for clinic,which is a kind of effective, recommendable method that could be investigated sequentially.Due to the limited of the cases number,we need more convincing results by the depth study in the further expanded samples.

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