Numerical studies of fluid-particle dynamics in human respiratory system

 This thesis investigates particle inhalation and its deposition in the human respiratory system for therapeutic and toxicology studies. Computational Fluid Dynamics (CFD) techniques including the Lagrangian approach to simulate gas-particle flows based on the domain airflow are used. The Lagrangian approach is used as it tracks each individual particle and determines its fate (e.g deposition location, or escape from computational domain). This has advantages over a Eulerian approach for respiratory inhalation flows as the volume fraction of the second phase can be neglected and a disperse phase for one-way coupling can be used. However, the very first step is to simulate and detail airflow structures. For the external airflow structures, the heat released from the human body has a significant effect on the airflow micro-environment around it in an indoor environment, which suggests that the transport and inhalation characteristics of aerosol particulates may also be affected since they are entrained by the air and their movement is dependent on the airflow field. Emphasis was put on the effect of human body heat on particle tracks. It was found that body heat causes a significant rising airflow on the downstream side of the body, which transports particles from a lower level into the breathing zone. The importance of body heat decreases with increasing indoor wind speed. Since the rising airflow exists only on the downstream side of an occupant, the occupant-wind orientation plays an important role in particle inhalation. The effect of body heat has to be taken into account when an occupant had his or her back to the wind, and the effect of body heat could be neglected when the occupant is facing the wind. A CFD model that integrates the three aspects of contaminant exposure by including the external room, human occupant with realistic facial features, and the internal nasal-trachea airway is presented. The results from the simulations visualize the flow patterns at different contaminant concentrations. As the particles are inhaled, they are transported through the respiratory airways, where some are deposited onto surrounding mucus walls while others may navigate through the complex geometry and even reach the lung airways, causing deleterious health effects. The studies in this thesis demonstrated that the transport and deposition of micron sized particles are dominated by its inertial property while submicron and nano sized particles are influenced by diffusion mechanisms. Studies based on an isolated model of the human nasal cavity or tracheobronchial airway tree rely on idealised inlet boundary condition imposed at the nostril or where, were a blunt, parabolic or uniform profile is applied. It is apparent that an integrated model made up of: i) room and ventilation, ii) aspiration efficiency, iii) and particle deposition efficiencies in the respiratory airway is needed. This leads to a more complete and holistic set of results, which can greatly contribute towards new knowledge in identifying preventative measures for health risk exposure assessment. With regards to the internal airflow structures and particle inhalation, ultrafine particle deposition sites in the human nasal cavity regions often omit the paranasal sinus regions. Because of the highly diffusive nature of nanoparticles, it is conjectured that deposition by diffusion may occur in the paranasal sinuses, which may affect the residual deposition fraction that leaves the nasal cavity. Thus a nasal-sinus model was created for analysis. In general there was little flow passing through the paranasal sinuses. However, flow patterns revealed that some streamlines reached the upper nasal cavity near the olfactory regions. These flow paths promote particle deposition in the sphenoid and ethmoid sinuses. Some differences were discovered in the deposition fractions and patterns for 5 and 10nm particles between the nasal-sinus and the nasal cavity models. This difference is amplified when the flow rate is decreased and at a flow rate of 4L/min the maximum difference was 17%. It is suggested that future evaluations of nanoparticle deposition should consider some deposition occurring in the paranasal sinuses especially if flow rates are of concern. Inhaled particles with pharmacological agents (e.g. histamine, methacholine) are introduced into the nasal cavity for targeted delivery. Effective nasal drug delivery is highly dependent on the delivery of the drug from the nasal spray device. Atomization of liquid spray occurs through the internal atomizer that can produce many forms of spray patterns and two of these, hollow-cone and full-cone sprays, are evaluated in this study to determine which spray pattern produced greater deposition in the middle regions of the nasal cavity. Past studies of spray particle deposition have ignored the device within the nasal cavity. Experimental measurements from a Particle Droplet Image Analyzer (PDIA) were taken in order to gain confidence to validate the initial particle conditions for the computational models.. Subsequent airflow patterns and its effects on particle deposition, with and without a spray device, are compared. Contours and streamlines of the flow field revealed that the presence of a spray device in the nasal vestibule produced higher levels of disturbed flow, which helped the dispersion of the sprayed particles. Particle deposition was found to be high in the anterior regions of the nasal cavity due to its inertia. Evaluation of the two spray types found that hollow spray cones produced more deposition in the middle regions of the nasal cavity

A design tool for use in simulation and training of sinus surgery

The traditional approaches to training surgeons are becoming increasingly difficult to apply to modern surgical procedures. The development of Minimally Invasive Surgery (MIS) techniques demands new and complex psychomotor skills, and means that the apprentice-based system described by “see one, do one, teach one” can no longer be expected to fully prepare surgeons for operations on real patients, placing patient safety at risk. The use of cadavers and animals in surgical training raises issues of ethics, cost and anatomical similarity to live humans. Endoscopic sinus surgery involves further risk to the patient due to the proximity of vital structures such as the brain, eyes, optic nerve and internal carotid artery. In recent years, simulation has been used to overcome these problems, exposing surgeons to complex procedures in a safe environment, similarly to its use in aviation. However, the cases simulated in this manner may not be customised by training staff to present desired pathology. This thesis describes the design and development of a new tool for the creation of customised cases for the training of sinus surgery. Users who are inexperienced and non-skilled in the use of three-dimensional (3D) Computer Aided Design (CAD) modelling software may use the tool to implement pathology to the virtual sinus model, which was constructed from real CT data. Swelling is applied in five directions (four horizontal, one vertical) to the cavity lining of the frontal and sphenoid sinuses. Tumours are individually customised and positioned in the frontal, sphenoid and ethmoid sinuses. The customised CAD model may then be latterly manufactured using Three-Dimensional Printing (3DP) to produce the complex anatomy of the sinuses in a full colour physical part for the realistic simulation of surgical procedures. An investigation into the colouring of the physical model is also described, involving the study of endoscopic videos to ascertain realistic shades. The program was evaluated by a group of medical professionals from a range of fields, and their feedback was taken into account in subsequent redevelopment of the program, and to suggest further work

Comparison of different rhinomanometry methods in the measurement of nasal airway resistance

Various rhinomanometry methods can be used to measure nasal airway resistance, which include the classic method at fixed pressure of 150 Pa or 75 Pa, Broms method at radius of 200 and 4-phase rhinomanometry method. This thesis compared the unilateral nasal resistance measurements obtained using these methods, when applied across four artificial model noses, to further improve our understanding of their relationship. The first comparison was made between the classic and 4-phase rhinomanometry method. No statistically significant differences were found between the values obtained from both methods (U>Ucritical, p>0.05). Bland- Altman plots also showed good agreement between both methods with narrow limits of agreement. The second comparison was made between the classic and Broms method. The measurements from the classic (at 75 Pa or 150 Pa) and Broms method gave either statistically significant similarities or differences (U>Ucritical, p<0.05) depending on the level of nasal resistances. The magnitude of change in resistance was also dependent on the method used, with bigger changes in resistance observed when using Broms method at certain levels of nasal resistances compared to classic measurements in the same patient. The last part of the thesis was to evaluate the reproducibility of the rhinomanometry methods and the rhinomanometer used in this study over a 24-hour period. Bland-Altman plots showed high level of agreement between measurements taken in both days and CV value ranges from 0.49-14.3%, which were acceptable levels of reproducibility. In conclusion, there was a high degree of conformity between resistances measured by the classic and 4-phase rhinomanometry methods. Broms method either gave similar or different measurements to the classic and, by extension of this study, 4-phase rhinomanometry measurements, depending on the level of nasal resistance. Applying the principle of Ockham’s razor, the simple classic method is recommended as the method of choice for rhinomanometry

European Position Paper on Rhinosinusitis and Nasal Polyps 2020

The European Position Paper on Rhinosinusitis and Nasal Polyps 2020 is the update of similar evidence based position papers published in 2005 and 2007 and 2012. The core objective of the EPOS2020 guideline is to provide revised, up-to-date and clear evidence-based recommendations and integrated care pathways in ARS and CRS. EPOS2020 provides an update on the literature published and studies undertaken in the eight years since the EPOS2012 position paper was published and addresses areas not extensively covered in EPOS2012 such as paediatric CRS and sinus surgery. EPOS2020 also involves new stakeholders, including pharmacists and patients, and addresses new target users who have become more involved in the management and treatment of rhinosinusitis since the publication of the last EPOS document, including pharmacists, nurses, specialised care givers and indeed patients themselves, who employ increasing self-management of their condition using over the counter treatments. The document provides suggestions for future research in this area and offers updated guidance for definitions and outcome measurements in research in different settings. EPOS2020 contains chapters on definitions and classification where we have defined a large number of terms and indicated preferred terms. A new classification of CRS into primary and secondary CRS and further division into localized and diffuse disease, based on anatomic distribution is proposed. There are extensive chapters on epidemiology and predisposing factors, inflammatory mechanisms, (differential) diagnosis of facial pain, allergic rhinitis, genetics, cystic fibrosis, aspirin exacerbated respiratory disease, immunodeficiencies, allergic fungal rhinosinusitis and the relationship between upper and lower airways. The chapters on paediatric acute and chronic rhinosinusitis are totally rewritten. All available evidence for the management of acute rhinosinusitis and chronic rhinosinusitis with or without nasal polyps in adults and children is systematically reviewed and integrated care pathways based on the evidence are proposed. Despite considerable increases in the amount of quality publications in recent years, a large number of practical clinical questions remain. It was agreed that the best way to address these was to conduct a Delphi exercise. The results have been integrated into the respective sections. Last but not least, advice for patients and pharmacists and a new list of research needs are included.Peer reviewe

European position paper on rhinosinusitis and nasal polyps 2020

The European Position Paper on Rhinosinusitis and Nasal Polyps 2020 is the update of similar evidence based position papers published in 2005 and 2007 and 2012. The core objective of the EPOS2020 guideline is to provide revised, up-to-date and clear evidence-based recommendations and integrated care pathways in ARS and CRS. EPOS2020 provides an update on the literature published and studies undertaken in the eight years since the EPOS2012 position paper was published and addresses areas not extensively covered in EPOS2012 such as paediatric CRS and sinus surgery. EPOS2020 also involves new stakeholders, including pharmacists and patients, and addresses new target users who have become more involved in the management and treatment of rhinosinusitis since the publication of the last EPOS document, including pharmacists, nurses, specialised care givers and indeed patients themselves, who employ increasing self-management of their condition using over the counter treatments. The document provides suggestions for future research in this area and offers updated guidance for definitions and outcome measurements in research in different settings. EPOS2020 contains chapters on definitions and classification where we have defined a large number of terms and indicated preferred terms. A new classification of CRS into primary and secondary CRS and further division into localized and diffuse disease, based on anatomic distribution is proposed. There are extensive chapters on epidemiology and predisposing factors, inflammatory mechanisms, (differential) diagnosis of facial pain, allergic rhinitis, genetics, cystic fibrosis, aspirin exacerbated respiratory disease, immunodeficiencies, allergic fungal rhinosinusitis and the relationship between upper and lower airways. The chapters on paediatric acute and chronic rhinosinusitis are totally rewritten. All available evidence for the management of acute rhinosinusitis and chronic rhinosinusitis with or without nasal polyps in adults and children is systematically reviewed and integrated care pathways based on the evidence are proposed. Despite considerable increases in the amount of quality publications in recent years, a large number of practical clinical questions remain. It was agreed that the best way to address these was to conduct a Delphi exercise . The results have been integrated into the respective sections. Last but not least, advice for patients and pharmacists and a new list of research needs are included

European Position Paper on Rhinosinusitis and Nasal Polyps 2020

The European Position Paper on Rhinosinusitis and Nasal Polyps 2020 is the update of similar evidence based position papers published in 2005 and 2007 and 2012. The core objective of the EPOS2020 guideline is to provide revised, up-to-date and clear evidence-based recommendations and integrated care pathways in ARS and CRS. EPOS2020 provides an update on the literature published and studies undertaken in the eight years since the EPOS2012 position paper was published and addresses areas not extensively covered in EPOS2012 such as paediatric CRS and sinus surgery. EPOS2020 also involves new stakeholders, including pharmacists and patients, and addresses new target users who have become more involved in the management and treatment of rhinosinusitis since the publication of the last EPOS document, including pharmacists, nurses, specialised care givers and indeed patients themselves, who employ increasing self-management of their condition using over the counter treatments. The document provides suggestions for future research in this area and offers updated guidance for definitions and outcome measurements in research in different settings. EPOS2020 contains chapters on definitions and classification where we have defined a large number of terms and indicated preferred terms. A new classification of CRS into primary and secondary CRS and further division into localized and diffuse disease, based on anatomic distribution is proposed. There are extensive chapters on epidemiology and predisposing factors, inflammatory mechanisms, (differential) diagnosis of facial pain, allergic rhinitis, genetics, cystic fibrosis, aspirin exacerbated respiratory disease, immunodeficiencies, allergic fungal rhinosinusitis and the relationship between upper and lower airways. The chapters on paediatric acute and chronic rhinosinusitis are totally rewritten. All available evidence for the management of acute rhinosinusitis and chronic rhinosinusitis with or without nasal polyps in adults and children is systematically reviewed and integrated care pathways based on the evidence are proposed. Despite considerable increases in the amount of quality publications in recent years, a large number of practical clinical questions remain. It was agreed that the best way to address these was to conduct a Delphi exercise . The results have been integrated into the respective sections. Last but not least, advice for patients and pharmacists and a new list of research needs are included. The full document can be downloaded for free on the website of this journal: http://www.rhinologyjournal.com