Study On Biomechanical Model Of Human Nasal Cavity And Its Clinical Application

Nasal cavity is the main passage of oxygen airflow. Except the main function of respiration nasal cavity provides the functions to filters, warms, and humidifies inspired air and protects the delicate structure of the lower respiratory system. The nasal cavity places itself at risk from the respiratory system sickness. Clinical medical treatment and research work demonstrate that nasal functions and nasal diseases are related to the structure of nasal cavity. In recent years it has been proved that the abnormal nasal structure will lead to some nasal diseases. The complex nasal structure and the lack of biomechanical model and numerical model make it is difficult to deeply explore. It has influenced the clinical forecast, diagnose, selection of treatment project and estimation of curative effect for the disease.In this paper, the nasal cavity structure is reconstructed based on the CT images and the numerical simulation for nasal airflow is performed. The relationship between nasal cavity structure and distribution of nasal airflow is investigated based on many reconstructed nasal cavity models. Then the change of distribution of nasal airflow is investigated that caused by the partly change of nasal structure. Based on these works two medical wares are designed to help the doctors and the patients. Five parts of this paper are summarized as follows:In the first part an efficient method for building nasal model is introduced. The nasal cavity structure of a healthy volunteer is reconstructed by the method of surface rendering based on his CT images. The numerical simulation and the analysis for the airflow in the nasal cavity was made by the finite element method and the results are compared with the data from the literature. The comparison indicates that the result is believable and this method is feasible.In the second part the relationship between nasal structure and distribution of nasal airflow is investigated. Numerical simulation for the airflow in 24 nasal models is performed. The characters of airflow distribution in all nasal models are investigated and classified. The numerical simulation and analysis for airflow field in the nasal models with turbinate removed partly are performed by the numerical simulation method. The simulation results from new models are compared with that from the original model to study the influence of change of nasal structure on the distribution of nasal airflow.In the third part the relationship between nasal airway dimension of normal adults and the degree of nasal obstruction will be investigated. The nasal airway resistance of 17 volunteers is measured through active anterior rhinomanomety. Curve fitting for the rhinomanometer data is performed to find the obstruction coefficient of nasal airway. We obtain the geometry dimensions of the nasal cavities from the CT images of volunteers. Nasal obstruction coefficient is considered as a function of the nasal airway dimensions. The undetermined coefficient is identified by curves fitting for the data of geometry dimensions and obstruction coefficients. It can be concluded that the nasal obstruction coefficient can be identified closely by geometry dimensions of nasal cavity such as nasal coronal section area, length of nasal airway and perimeter of coronal section of nasal airway.In the fourth part the drainage ware is designed for postoperative care after functional endoscopic sinus surgery. It can prevent the ostium of maxillary sinus from closing, drain the empyemata from maxillary sinus and send the medicament to the field of ostiomeatal complex. Based on the results of numerical simulation of airflow in nasal cavity and the data obtained from Rhinomanometry the characters of airflow in the middle nasal meatus are acquired. The numerical model of drainage ware is generated. Based on the tow-phase flow theory numerical simulation for the liquid in the drainage ware is performed to explain how the drainage ware dose its work. Changing the tube diameter or viscosity parameters of liquid-phase flow different results of numerical simulation are acquired. Comparing the computational results the fit diameter of drainage tube is obtained. The drainage ware designed in this study can accomplish the work of keeping ventilation, draining the empyemata, sending medicament and preventing the ostium of maxillary sinus from closing.In the fifth part the packing-fixer is designed as packing material for nasal that can keep breathing, fix the nasal septum and arrest bleeding after nasal septum mucous membrane surgery. Numerical simulation is performed to study the function of packing-fixer and expansive sponge in nasal cavity by means of finite element method. The compression stress and the first principal stress are compared between tow conditions. From the simulation results it can be demonstrated that the packing-fixer designed in this study can keep breathing, fix the nasal septum and arrest bleeding after nasal septum mucous membrane surgery and would not break the nasal septum mucous membrane.The study would contribute to nasal clinical application in clinical diagnose, design of treatment project and estimation of curative effect for the disease.