疾患鼻気道における空気流と粒子堆積の計算流体力学的研究

Understanding the properties of airflow in the nasal cavity is very important in determining the nasal physiology and in diagnosis of various anomalies associated with the nose. The complex anatomy of the nasal cavity has proven to be a significant obstacle in the understanding of nasal obstructive disorders. Due to their non-invasiveness, Computational Fluid Dynamics (CFD) has now been utilized to assess the effects of surgical interventions on nasal morphological changes as well as local breathing airflow characteristics through the upper airway of individual patients. Furthermore, nasal inhalation is a major route of entry into body for airborne pollutions. Therefore, the function of the upper airway to filter out the inhaled toxic particles is considered important. The determination of the total particle filtering efficiency and the precise location of the induced lesion in the upper airway is the first step in understanding the critical factors involved in the pathogenesis of the upper airway injury. The present work involved development of three-dimensional diseased upper airway models from Computed Tomographic (CT) scan images derived from a nasal airway without any nasal diseased and an upper airway which was diagnosed with chronic nasal obstruction and obstructive sleep apnea. Numerical simulation of airflow and transport and deposition of inhaled pollutant through chronic diseased nasal airway, constricted pharyngeal representing Obstructive Sleep Apnea (OSA) and diseased upper airway with OSA for pre- and post-operative cases have been studied. Detailed flow pattern and characteristics for inspiratory airflow for various breathing rates (7.5-40 L/min) were evaluated. Simulation of the particle transport and deposition of micro-sized particles with particle diameter ranging from 1-40 ?m were also investigated. In the first part of this study, the surgical treatment performed in the nasal cavity which include septoplasty, inferior turbinate reduction and partial concha bullosa resection substantially increased nasal volume, which influenced flow partitioning and decreases the pressure drop and flow resistance of the nasal passage. The removal of the obstruction in the nasal airway significantly improve the breathing quality. However, the nasal airway experienced approximately about a 50 % decrease in total particle filtering efficiency after surgery. Therefore, careful consideration should be given to this matter before nasal operation especially for a patient with breathing allergic history. In the second part of this study, the morphology of the constricted pharyngeal representing OSA was found to significantly affect the airflow pattern and the deposition fraction of microparticles. The morphology of the upper airway, the size of the inhaled particle and breathing rate was found significantly affect the total particle deposition efficiency and local deposition fraction in the upper airway. The presented regional deposition fraction may be used in specifying the site of highest possibility for respiratory lesions according to the breathing rate and the size of the inhaled toxic particles. Results obtained from this study can be also used to estimate the location of airway obstruction in upper airway of patient with sleep apnea symptom. In the third part of this study, the surgical conducted procedure has cleared out the obstructions in the nasal airway hence improve the airflow distribution through the upper airway during inhalation process. This study shows that the nasal surgery alone can help improve the breathing quality in the upper airway with OSA. The reduction of the airflow resistance in the nasal cavity affect the pressure distribution in the lower part of the upper airway. Obstruction in the nasal passage and sudden airway expansion in the upper airway increased number of particles trap, recirculated and finally deposited in the airway. Finally, the experimental data obtained from the experimental study utilizing the developed pharyngeal airway further validate the result obtained from the numerical study.九州工業大学博士学位論文 学位記番号：生工博甲第315号 学位授与年月日：平成30年3月23日1: INTRODUCTION|2: LITERATURE REVIEW|3: MODELLING THE HUMAN UPPER AIRWAY|4: NUMERICAL SIMULATION METHODOLOGY|5: NUMERICAL INVESTIGATION ON AIRFLOW CHARACTERISTICS IN NASAL CAVITY HAVING TURBINATE HYPERTROPHY, CONCHA BULLOSA, AND SEPTUM DEVIATION WITH OSA: PRE- AND POST SURGERY|6: COMPUTATIONAL FLUID DYNAMICS STUDY OF AIRFLOW AND MICROPARTICLE DEPOSITION IN A CONSTRICTED PHARYNGEAL SECTION REPRESENTING OBSTRUCTIVE SLEEP APNEA DISEASE|7: NUMERICAL SIMULATION OF AIRFLOW AND AEROSOL DEPOSITION IN REALISTIC HUMAN UPPER AIRWAY WITH OBSTRUCTIVE SLEEP APNEA AND CHRONIC NASAL OBSTRUCTION: PRE- AND POST-SURGERY|8: EXPERIMENTAL INVESTIGATION|9: CONCLUSIONS AND FUTURE RECOMMENDATIONS九州工業大学平成29年

Biomechanics of Snoring and Sleep Apnea

To understand the mechanisms of snoring and sleep apnea a first-principles biomechanical analysis was done for airflow through branched parallel channels, separated by a freely movable soft palate, and converging to a common channel at the base of the tongue in a “Y-shaped” configuration. Branches of the Y describe slit-like passages on the nasal and oral sides of the soft palate, when the palate is pushed by backward movement of the tongue to form a wedge between the tongue surface and the posterior pharyngeal wall. The common channel of the Y describes the oropharyngeal passage between the base of the tongue and posterior pharyngeal wall. Channel resistances are characterized by a generalized Poiseuille Law for laminar flow. Pressure changes from flow through channel resistances and also from the Venturi effect are specified quantitatively. The resulting equations are solved both algebraically and numerically to describe motion of the soft palate and tongue during snoring and sleep apnea. Soft tissue motions are produced by counterbalanced Venturi pressures on opposite sides of the soft palate and by counterbalanced Venturi pressure and elastic recoil at the base of the tongue. Multiple physical mechanisms were discovered that can produce tissue motion at typical snoring frequencies in this system, some with the mouth open and some with the mouth closed. These palatal and tongue movements resemble motions of pendulums that oscillate in potential energy wells. Specific physical conditions leading to sleep apnea are identified, in which narrow gaps and unbalanced Venturi pressures lead to stable and effort-independent airway occlusion. The present analysis shows how the phenomena of both snoring and sleep apnea are fundamentally related and are governed by the same equations

Biomechanical Models of Human Upper and Tracheal Airway Functionality

The respiratory tract, in other words, the airway, is the primary airflow path for several physiological activities such as coughing, breathing, and sneezing. Diseases can impact airway functionality through various means including cancer of the head and neck, Neurological disorders such as Parkinson\u27s disease, and sleep disorders and all of which are considered in this study. In this dissertation, numerical modeling techniques were used to simulate three distinct airway diseases: a weak cough leading to aspiration, upper airway patency in obstructive sleep apnea, and tongue cancer in swallow disorders. The work described in this dissertation, therefore, divided into three biomechanical models, of which fluid and particulate dynamics model of cough is the first. Cough is an airway protective mechanism, which results from a coordinated series of respiratory, laryngeal, and pharyngeal muscle activity. Patients with diminished upper airway protection often exhibit cough impairment resulting in aspiration pneumonia. Computational Fluid Dynamics (CFD) technique was used to simulate airflow and penetrant behavior in the airway geometry reconstructed from Computed Tomography (CT) images acquired from participants. The second study describes Obstructive Sleep Apnea (OSA) and the effects of dilator muscular activation on the human retro-lingual airway in OSA. Computations were performed for the inspiration stage of the breathing cycle, utilizing a fluid-structure interaction (FSI) method to couple structural deformation with airflow dynamics. The spatiotemporal deformation of the structures surrounding the airway wall was predicted and found to be in general agreement with observed changes in luminal opening and the distribution of airflow from upright to supine posture. The third study describes the effects of cancer of the tongue base on tongue motion during swallow. A three-dimensional biomechanical model was developed and used to calculate the spatiotemporal deformation of the tongue under a sequence of movements which simulate the oral stage of swallow

Numerical modelling of fluid-structure interactions for fluid-induced instability in the upper airway

This study is concerned with fluid-structure interactions (FSI) involved in the human upper airway, in particular, those associated with snoring and obstructive sleep apnoea/hypopnoea syndrome (OSAHS). Further examining this area of interest, the goal of the current research is to contribute further understanding and enhance development of computational modelling, for retroglossal obstruction and palatal snoring. To that end, the investigation was divided into three major parts. Firstly, extending previous laminar, 2-D reduced Navier-Stokes model, an idealised 3-D computational model was constructed for studying retroglossal obstruction. A full Navier-Stokes solver in an Arbitrary Lagrangian-Eulerian (ALE) framework was coupled to a linear thin shell, where both laminar and turbulent flow was investigated. Numerical results showed increase flow-induced tongue replica deflection under turbulent conditions and demonstrated cross-flow pressures that may encourage side wall collapse. In the second part of the thesis, palatal snoring was further examined and its potential to detect retroglossal obstruction was proposed. In order to investigate this, flow-induced instability of a cantilever plate in an obstructed channel was modeled and a relationship between critical velocity and obstruction depth was established. Correlating the critical velocity with typical breathing flow curve, a time difference between palatal snoring episodes or onset of palatal snoring, may represent a key variable for non-invasive measurement of retroglossal obstruction severity. Further enhancement of the 2-D computational model by including contact was proposed using an immersed boundary method (IBM). This may represent a more complete model of palatal snoring by modelling pre- and post-contact response of unstable cantilever plate, which showed potential to capture more complicated palatal snoring signals. Finally, the third part of this thesis examined flow-induced instability of a soft palate in a 3-D realistic upper airway. To model this, a full 3-D Navier-Stokes solver under an ALE framework was coupled to a non-linear soft palate model. Appropriate soft palate properties were applied giving palatal snoring frequency within range of clinically measured values. Palatal flutter was observed at high flow rates, demonstrating irreversible transfer of flow energy to soft palate. This computational model may perhaps be exploited for future investigation of more accurate palatal snoring, necessary for developing non-invasive snoring signals for measurement or diagnosis of retroglossal obstruction

Effect of Orthognathic Surgery on the Upper Airway System

Sleep apnea is a disease which has not been getting an adequate amount of attention in the research community for a long time. However, the strain on the cardiovascular system and other serious problems, such as daytime sleepiness and even neurocognitive dysfunction, that it causes may be severe in advanced cases of the illness, as such it can significantly affect the heart especially and lead to cardiac arrest. Thus, it has been receiving a lot of attention recently. Tampere University Hospital has a goal of creating a comprehensive upper airway airflow model for surgery outcome prediction. That requires knowledge of available models and analysis of static magnetic resonance images, among other things. This document deals with these two main issues. This thesis has two major parts, one of them being a literature review of sleep apnea and models used in airflow modelling in the upper airways. Modelling of airflow generally includes acquisition of a static upper airway system model (in the case of upper airway modelling) and then adding a dynamic component to it. The second part of this thesis deals with acquisition of the static model, which involves segmentation of MRI image sets from 3 patients (pre- and post-operative sequences). It also answers the question, whether the effect of orhtognathic surgery on the upper airway system can be seen from volumetric analysis of the segmented images and the segmented images themselves. The main methods of adding a dynamic component to the static model turned out to be computational fluid mechanics and finite element modelling, including their sub-methods, such as direct numerical simulation of large eddy simulation. As with the second part of the thesis, the volumetric segmentation data is rather inconclusive and should not be related solely for evaluation of the effect of orthognathic surgery on the upper airway system. It can be said, nonetheless, that the volume of the upper airway itself is rather easily obtainable and reliable. The images themselves, however, provide very visual information about that, and shifting of certain muscles and muscle groups and other structures can be seen

A Numerical Study of Airflow Through Human Upper Airways

Ph.DDOCTOR OF PHILOSOPH

Feasibility of Individualized Airway Surgery in Horses

This thesis describes a progressive series of studies that was conducted to investigate the use of benchtop and computational models in the investigation of multiple upper airway surgeries for recurrent laryngeal neuropathy (RLN) in horses. Overall, the objective was to build the knowledge of laryngeal conformation and fluid mechanics with various surgical procedures for application in patients as an evaluation for the surgery of best outcome and as a step toward patient-specific diagnosis and treatment of upper airway disorders. The first study built upon a previously reported vacuum-based box setup that was used to compare RLN to four different surgical procedures within twenty-eight different equine larynges. Each larynx underwent these procedures in order and inhalation was simulated while measuring resistance to airflow (translaryngeal impedance). Two of the procedures, the combined laryngoplasty, ipsilateral ventriculocordectomy with arytenoid corniculectomy (LLPCOR) and laryngoplasty with ipsilateral ventriculocordectomy (LLP) were found to be significantly different from the RLN, arytenoid corniculectomy (COR) and partial arytenoidectomy (PA). The adapter used to mount the larynges was found to have a significant effect for the RLN, LLP and LLPCOR procedures. There was also a residual intraclass correlation of 27.6% in the final statistical model from individual laryngeal differences which were observed during the study. The variation of laryngeal features observed during the first study led to questions about the interaction between these geometries and airflow development. To capture the three-dimensional geometry effectively, similar methodology was repeated with concurrent computed tomography (CT) scans. These scans were analyzed focusing on cross-sectional area and changes along the airstream. Each procedural run was analyzed and used to simulate a pipe constriction. Entrance and exit conformations were modeled with respect to the ratio of the inlet cross-sectional area (CSA), constriction CSA and the divergent CSA downstream. The entrance characteristics were found to be significant; specifically, the angle of constriction and the ratio of the larger and smaller areas had a significant effect on laryngeal impedance. A frictional coefficient was measured as a function of energy lost by air passing through the constricted area and was found to be significant. This confirmed the importance of detail in surgically addressing disease affecting the laryngeal entrance. To provide a more thorough analysis of geometry and flow application of computational fluid dynamics (CFD) analysis was next reasonable step. The next study consisted of CFD analysis of the CT scans to determine the accuracy of CFD in reflecting the findings of the vacuum box airflow model. CFD provides a three-dimensional analysis of flow through complex geometries but also reduces the expense and intensive labor of complex flow experiments. Given these potential applications, this study reported the use of CFD to predict the procedure with the lowest impedance for each larynx. CFD results were compared to the measured values. Additionally, qualitative characteristics of the flow within the anatomical paradigm were examined. The CFD models corroborated the procedure of lowest impedance for 7 out of 10 of the larynges; 2 larynges had 2 procedures that were very close in impedance and the last larynx had unique collapse characteristics that may explain the lack of agreement. The measured pressure and impedance values showed a linear trend compared to the calculated values with measured impedance about 0.7 times that of the calculated (CFD) values. Qualitatively, areas of negative pressure and high velocity were noted in the higher impedance procedures and around tissue irregularities. While the CFD model was reasonably successful for the laryngeal study, demonstration of use in a more realistic equine patient application is needed. The final study took an additional step toward the equine patient by incorporating an entire head with measured translaryngeal impedance similar to the previous studies. A cadaver head was used and RLN, LLP, LLPCOR, COR and PA were simulated and subjected to negative airflow. The impedance values measured during this study were higher than expected, but the computational model reported values that were similar to the previous literature. The observed flow characteristics showed some differences to previous studies but the CFD model clarified these differences by highlighting the differences in three-dimensional geometry between the heads used in each study. The PA was the lowest impedance procedure both as measured and as calculated. Thus, CFD continued to demonstrate a predictive capability when it comes to determining the procedure of lowest impedance for the whole equine upper airway. Although there have been a large number of biomechanical models investigating the equine upper airway, they have not kept up with the technological advancements in human respiratory mechanics and CFD. CFD consistently confirmed the procedure of lowest impedance while incorporating individual patient geometry and can be performed much more efficiently than when the first equine application was reported over a decade ago. While more studies are needed, these models unquestionably provide a foundation for individual patient analysis in the future

A Cephalometric Study of the Maxillofacial Structure in Obstructive Sleep Apnoea

Sleep is essential for life. We spend somewhere between one quarter and one third of our lives sleeping, depending upon our sleep pattern. Sleep is a normal physiological process, and as with all such processes there are some differences between individuals that are simply variations of normal. Likewise sleep may be associated with variations that are deemed to be outside the boundaries of those considered normal and is therefore considered pathologic. The investigation of a known abnormality of sleep, namely Obstructive Sleep Apnoea (OSA) syndrome, forms the basis of this thesis and an understanding of normal sleep physiology is essential prior to considering the alterations in normal sleep architecture exhibited in this condition. Chapter 1 considers the definition of normal sleep, the diagnosis of pathologic sleep and the characteristic alterations in sleep and wakefulness demonstrated in a person suffering from obstructive sleep apnoea. Obstructive Sleep Apnoea syndrome is a medical condition that has been intensively studied by investigators in various fields of medicine and dentistry since being characterized by Guilleminault et al (1976). The classical description of patients with this syndrome was made by Burwell et al (1976). These patients were said to be obese, suffering from hypersomnolence, periodic breathing with hypoventilation and cor pulmonale. Pickwickian syndrome was the term used in 1918 by Sir William Osler when describing patients with a similar clinical presentation. The research into obstructive sleep apnoea syndrome has revealed pathophysiologic alterations in a variety of bodily systems in these people when compared to non-apnoeic people. These pathophysiologic findings are discussed in Chapter 2. Assessment of the upper airway may be performed clinically, endoscopically, radiographically or using other imaging modalities such as magnetic resonance imaging or manometry. The assessment method evaluated in this thesis is lateral cephalometric radiography. In selecting a method of imaging, it is necessary to have a thorough understanding of the anatomy of the region under examination. Chapter 3 of this thesis outlines the pertinent anatomy of the upper airway and an overview of the available methods of imaging is given. Lateral cephalometric assessment of the upper airway is discussed in particular because it was the modality under investigation. Chapter 4 reviews the literature with respect to known errors using this technology. Although only recently used in relation to obstructive sleep apnoea, lateral cephalometric radiographs have long been utilised by orthodontists and oral and maxillofacial surgeons in the diagnosis and treatment planning of people with malocclusion. Despite a large number of studies reported in the literature regarding lateral cephalometric radiographs and OSA direct comparison between studies is often difficult. Many studies purport to measure the same parameters e.g. pharyngeal airway width but use different landmarks. Some studies use control subjects who are age and/or weight matched, other studies use controls not matched for these parameters. Yet other studies use no control subjects at all. Chapter 5 and Chapter 6 of this thesis provide a review of the literature where lateral cephalometric radiographs have been used to assess subjects with obstructive sleep apnoea syndrome. The imaging of the upper airway is obviously no treatment in itself. One of the problems as with many medical conditions, is the cure may not be acceptable to the patients with the condition. In the case of obstructive sleep apnoea syndrome tracheostomy will cure the patient of the upper airway obstruction however at a personal cost not accepted by most patients. The standard treatment for obstructive sleep apnoea syndrome since 1981 has been nasal continuous positive airway pressure ventilation, reported by Sullivan et al (1981). This modality is reported in the literature to be efficacious however compliance remains an issue. Chapter 7 considers the non-surgical treatment modalities that have been and are used in the treatment of obstructive sleep apnoea syndrome. Surgical treatment for obstructive sleep apnoea syndrome, apart from tracheostomy, has been reported in the literature since 1981 when Fujita reported uvulopalatopharyngoplasty as a surgical technique for the treatment of snoring and obstructive sleep apnoea syndrome. Since that time a number of surgical procedures have been reported with varying degrees of success. These surgical modalities reported in the literature are considered in Chapter 8. On the basis of the literature review, several aims were established using material from the Oral and Maxillofacial Surgery unit, The University of Adelaide and the Thoracic Medicine Unit, The Royal Adelaide Hospital. The objectives of the study were to: 1. Acquire cephalometric data on I 00 consecutive patients undergoing a polysomnographic overnight sleep study for investigation of a suspected sleep breathing disorder as assessed by a thoracic medicine physician. 2. Quantify the airway dimensions of this series of patients using measurements previously reported in the literature. 3. Establish whether BMI has any predictive value for OSA. 4. Establish whether neck circumference is related to BMI or the incidence of OSA. 5. Establish whether age or sex has any influence on the incidence of OSA. 6. Compare airway dimensions measured from the lateral cephalometric radiograph and the severity of OSA to determine if any measurement is predictive for the presence of OSA. 7. Compare airway dimensions measured from lateral cephalometric radiograph and quantify any differences between the study population of OSA patients and simple snorers compared with comparable results reported in the literature. 8. Investigate the sources of error in cephalometry and quantify the error associated with the present study. 9. Quantify the error associated with selected cephalometric variables used in this study. 10. Determine if lateral cephalometric radiographs are a useful adjunct to treatment planning for patients with OSA. Chapter 9 and Chapter 10 report the methodology used in order to achieve the aims of the study. Chapter 11 reports the results of this study. The linear and angular variables measured from the lateral cephalometric radiographs was initially assessed with respect to body mass index (BMI) and respiratory disturbance index (RDI). Subjects were then divided upon the basis of RDI into groups of "snorers" and "obstructive sleep apnoeics". Further statistical evaluation was then performed on the groups. To allow comparison with other results from the literature, the division by RDI was performed three times, at an RDI 10, 15 and 20 events per hour. These results are discussed and compared with the findings in the literature in Chapter 12. Chapter 13 summarises the key findings of this thesis and suggests areas of future investigation to further our understanding of the upper airway changes reported in obstructive sleep apnoeic subjects. A glossary of terms is provided at Chapter 14. The Appendix is a copy of the consent and patient information given to participants prior to their enrolment in this study.Thesis (MDS) -- University of Adelaide, Dept. of Oral and Maxillofacial Surgery, 200

Tracheal Breath Sounds - instrumentation and origin

Tässä työssä tehtiin kirjallisuuskatsaus trakeasta kuultavien hengitysäänien instrumentointiin, normaaleihin ja epätavallisiin trakeasta kuultaviin ääniin. Katsauksessa havaittiin, että hengitysäänten rekisteröintiin käytettävien sensoreiden suunnittelulla voidaan vaikuttaa rekisteröityihin ääniin. Erityisesti ilmakytkettyjen kontaktimikrofonien ilmakammiolla voi olla suuri vaikutus mitattuihin ääniin. Normaalien trakeahengitysäänien alkuperä on aeroakustinen. Ilmavirtauksen nopeuden kasvaessa laminaarinen virtaus irtautuu henkitorven seinämästä ja virtaukseen syntyy pyörteitä. Virtaus on muuttunut turbulenttiseksi. Kun nämä pyörteet kulkeutuvat kapeikon läpi, mikä voi olla pelkkä muutos henkitorven poikkipinta-alassa, osa pyörteen liike-energiasta muuttuu akustiseksi häiriöksi. Tämän lisäksi kirjallisuuskatsauksessa tutkittiin epätavallisten trakeasta kuultavien hengitysäänten syntyä. Avoimen, osittain ahtautuneen ja kokonaan ahtautuneen hengitystien tapaukset tarkasteltiin erikseen Sterling-vastusmallin avulla. Kuorsausta ja kudosvärinää havaittiin tilanteessa, jolloin hengitystie oli osittain ahtautunut. Pirkanmaan sairaanhoitopiirin unilaboratoriossa käytetylle trakeaäänien rekisteröintilaitteistolle tehtiin laatumittauksia. Mittauksissa havaittiin, että mikrofonissa oli hieman harmonista vääristymää ja käytetyn äänikortin taajuusvaste ei ollut suora, kun näytteenottotaajuutena oli 11kHz. Yhteenvetona voidaan sanoa, että eri tutkimusryhmien tulisi käyttää laadultaan korkeatasoisia mittalaitteita, kun trakeasta kuuluvia hengitysääniä rekisteröidään. Jos näin toimittaisiin, korkealaatuinen trakea-hengitysääni voisi tuoda uutta tietoa unen hengitysfysiologiaan liittyen. Nykyisessä tilanteessa eri tutkimusryhmien mittaukset eivät ole täysin vertailukelpoisia keskenään ja tämän vuoksi tieteellistä luotettavuutta on vaikea saavuttaa