Numerical investigation of airflow in the human nasal cavity and virtual septoplasty

Breathing is an inherent feature that needs to be done to provide the body with the oxygen it needs. Human is able to transmit this oxygen to the brain and other organs of the body by means of blood to survive. Even though a person can survive for several weeks without eating and several days without drinking, cannot survive without oxygen for more than a few minutes. When adequate oxygen does not enter the body, negative reactions such as vision, hearing disorders, negative state, psyhcological problems, mental depression, depression occur. Even brain deprivation causes permanent damage and paralysis. Inadequate oxygen is also a great factor for people to feel tired during the day. The structure of the nose, where breathing begins in the body, is of great importance for easy breathing. Genesis, sleep apnea, deviation, traumas that occur later cause intaking insufficient oxygen from the nose during breathing. For this reason, many people today undergo surgical treatment for their noses. In recent years; developments in computational engineering and informatics, as well as in many fields, have also had an impact on the field of medicine and has led to the emergence and advance of branches of bioengineering and biomechanics, which are the common fields of study of medicine and engineering disciplines. As a result of developments in the field of biomechanics; physicians prefer not only treatment methods in branches they specialize in, but also diagnosis and possible surgical intervention and engineering-based methods such as "virtual surgery" to predict and interpret gains and / or losses.It is a very important development for both the patient and the physician to predict the results of a possible operation in the computer environment, especially when the patient is at risk of surgery and the surgical decision is difficult. Nasal septum deviation, defined as the midline shift of the middle wall of the nose adversely affects the patient health and quality of life negatively in many respects, is seen in an average of 20% to 35% of the population from newborns to adults and its treatment is possible only by a surgical method called septaplasty. However, the efficacy of septoplasty is still being questioned today and it has been revealed by some studies in the literature that the patient has a psychological recovery in the short term but the long-term satisfaction rate has decreased. Therefore, it is of great importance that the gains and / or losses of a nasal surgical operation can be demonstrated in advance by a virtual surgery approach. If it is concluded that virtual septoplasty can be applied effectively or has the potential to be effectively applied, it will be possible to prevent unnecessary surgeries in the long term and contribute to the national economy and eliminate the negative effects of risky septoplasty on patient health. This thesis; is an interdisciplinary study solved by numerical methods based on virtual septoplasty. The numerical part of the study includes modeling of the air flow in the nasal cavity before and after septoplasty by Computational Fluid Dynamics (CFD) methods, estimating the benefits and / or damages to be obtained from surgical intervention by examining the results and determining the most appropriate surgical intervention scenario in terms of patient health and quality of life. In this context, before the septoplasty, computed tomography (CT) or magnetic resonance (MR) images of the patient's nasal cavity were processed with 3D modeling program and adapted to HAD analysis, a network was formed with ICEM-CFD program and CFD analyzes is made with ANSYS-Fluent software. After evaluating the current situation through the parameters in the flow area, nasal resistance etc., the necrotic cavity geometry was changed with Sculptor software and virtual septoplasty was applied. With CFD analysis of air flow in nasal cavity undergoing virtual septoplasty it is able to estimate the results obtained from real septoplasty. In order to verify the methods to be used within the scope of the thesis, the method has been developed over the Standard Carleton-Civic Nose Model which has been studied previously. CFD results were compared with numerical and experimental studies in the literature and the success of this study was compared with the literature. In this thesis, flow rates in which the flow is turbulent or laminar for different flow rates are determined. Which turbulence model should be selected if the flow is turbulent is revealed. Solution methods to be applied in the analysis of CFD analysis, input-output boundary conditions and initial conditions were determined. The method of study is prepared by examining the independence of the solution network. As it was in the literature, by taking sections of different parts of nasal cavity at 30 l/min air flow rate, the results are compared by taking the turbulance kinetic energy and velocity contours. By collecting pressure values of the air inlet and outlet points of the nose, flow-pressure graphics are created. Velocity taken from the appropriate section is drawn without any dimension on the profile and nasal resistance which is in the cavity, loss coefficient and nasal strength were calculated and interpreted. The method applied is considered valid based on the consistency of the results, a septal deviation was performed on the standard Carleton model in order to make a comparison of the preoperative and postoperative status, CFD analysis was repeated. It is concluded that virtual septoplasty can be applied by looking at the differences between deviated and non-deviated models. In this study, it is aimed to predict the possible outcomes of the planned therapies before the surgery for nasal septal deviation by virtual septoplasty. When the results are evaluated, how the nasal resistance of the patients with nasal septum deviation will change after the operation, physicians planned to make the treatment in the virtual environment and thanks to developing technology, The assistance of advances in medicine and engineering has been calculated by conducting CFD analysis with this interdisciplinary study. It has been predicted how nasal resistance may change after septoplasty. Positive or negative feedback to the patient can only be confirmed by taking CT images again after the actual operation. This method may help our physicians to develop the appropriate treatment method before surgery, to provide psychological relief by providing the patients with the possible surgical results before septoplasty, to facilitate the surgical decision, to decide whether the surgery is necessary and to reduce the unnecessary use of the operating rooms. There have also been cases in the septoplasty that require inadequate repetition of treatment. Thanks to this method, the patient will be prevented from lying under the knife again. The results obtained are promising in this respect. This method can be seen as the first stages of a study that will help to see the possible septoplasty results of the patient in the practice by shortening the duration of CFD analysis over time and perhaps within minutes. It is also a good example for the engineering and medical sciences to work together. In addition to this study, the effect of the acceptance of the nasal cavity can be examined. Without neglecting the effects of approach of dynamic wall approach, particle, heat transfer, sinus, sil and similar structures in the nose, this study can be more realistic in mathematical modeling of physical event. The results of CFD obtained from the virtual surgery method mentioned within the scope of the thesis can be questioned by comparing the results of the CFD analysis with repeated images taken from the patient after a real septoplasty operation. In this way, it can be provided to physicians to increase the confidence of physicians in virtual operations by expressing the availability of virtual septoplasty method in determining the appropriate treatment method.