Open Theses & Dissertations

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Tuwhera Open Access Theses & Dissertations contains digital copies of theses, dissertations and research projects from AUT's postgraduate research, deposited with the Library since 2002. The full text digital files are available if the author has given permission for their thesis, dissertation or research projects to be available open access.

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A Simulation Model of Infant-Incubator-Feedback System With Humidification and Temperature Control
(Auckland University of Technology, 2006) Al-Taweel, Yasser Amer
A comprehensive simulation model for the infant-incubator-feedback system was developed in a Matlab/Simulink® environment to investigate all heat exchange relationships, variables and factors that have an influence on the overall thermo-neutrality of the environment. The model was also used to determine the benefits and limitations of using a convectively heated single-walled incubator in nursing preterm infants with very low birth weight < 1000 grams and low gestational age 28 weeks. The infant was modelled as one-lump with two layers; core and skin. The infant shape was approximated to a cylinder. The model incorporated all compartments of the infant-incubator system including core, skin, incubator air space, mattress, incubator walls, air-circulating fan, heating element, added oxygen (for resuscitation purposes), and humidification chamber, which has not previously been considered. The results of the simulation were in terms of the temperature variation over time, of the following parts of the system: core and skin temperatures and incubator air space temperature. Results of the simulation with added humidity showed that the body temperature of a 900 gram infant, with an initial body temperature of 35.5 ºC, did not reach the thermo-neutral range between 36.5-37.5 ºC in two hours, on air mode. Whereas, on skin mode, both core and skin temperature reached to 36.87 ºC and 36.5 ºC in two hours, and thus a thermo-neutral environment was achieved. These outcomes are consistent with clinical empirical reports. The simulation model is a closed-loop system with a PID controller for each mode; air servo controlled and skin servo controlled. The controller parameters were virtually estimated by the Zeigler-Nichols Method as real values were not available. Nevertheless, the overall stability of the whole system has been achieved by applying a step input which was verified by the Root Locus Method.
Airway smooth muscle dynamics
(Auckland University of Technology, 2010) IJpma, Gijs
The current study aims to investigate the relative contributions of each of the processes that govern airway smooth muscle mechanical behaviour. Studies have shown that breathing dynamics have a substantial effect on airway constriction in healthy and diseased subjects, yet little is known about the dynamic response of the main instigator of airway constriction, Airway Smooth Muscle (ASM). In this work several models are developed to further the understanding of ASM dynamics, particularly the roles and interactions of the three dominant processes in the muscle: contractile dynamics, length adaptation and passive dynamics. Three individual models have been developed, each describing a distinct process or structure within the muscle. The first is a contractile model which describes the contractile process and the influence of external excitation on contractile behaviour. The second model incorporates the contractile model to describe length adaptation, which includes the reorganisation and polymerisation of contractile elements in response to length changes. The third model describes the passive behaviour of the muscle, which entails the mechanical behaviour of all non-contractile components and processes. As little data on the passive dynamics of the muscle was available in the literature, a number of experiments were conducted to investigate relaxed ASM dynamics. The experimental data and mathematical modelling showed that passive dynamics plays not only a dominant role in relaxed ASM, but contributes considerably to the dynamics of contracted muscle as well. A novel theory of sequential multiplication in passive ASM is proposed and implemented in a mathematical model. Experiments and literature validated the model simulations. Further integration of the models and improved force control modelling of length adaptation is proposed for future study. It is likely that the coupling of the models presented here with models describing other airway wall components will provide a more complete picture of airway dynamics, which will be invaluable for understanding respiratory disease.
Airway Smooth Muscle Response to Vibrations
(Auckland University of Technology, 2006) Du, Youhua
The main goal of this research was the in vitro investigation of the stiffness response of contracted airway smooth muscles under different external oscillations. Living animal airway smooth muscle tissues were dissected from pig tracheas and stimulated by a chemical stimulus (acetylcholine). These tissues were then systematically excited with different external vibrations. The force change was recorded to reflect the muscle stiffness change under vibration. The static and dynamic stiffness of contracted airway smooth muscles in isometric contraction were determined before, during and after vibrations. A continuum cross-bridge dynamic model (the fading memory model) was modified to accommodate smooth muscle behaviour and dynamically describes the cross-bridge kinetics. A two-dimensional finite element model (FEM) was developed to simulate longitudinal and transverse vibrations of the tissue. An empirical equation, derived from the experiments, is incorporated into the FEM. The results indicate that the stiffness of active smooth muscles can be physically reduced using external vibrations. This reduction is caused by a certain physical position change between actin and myosin. The dynamic stiffness has the tendency of decreasing as the frequency and/or amplitude of external vibration increases. However, the static stiffness decreases with an increase in the frequency and amplitude of excitation until it reaches a critical value of frequency where no variation in stiffness is observed. It is postulated that the tissue elasticity and mass inertia are the main contributors to the dynamic stiffness while the actin-myosin cross-bridge cycling is the main contributor to the static stiffness.
An Investigation Into 5-Lobe Lung Modelling
(Auckland University of Technology, 2005) Vuong, Xuan Tung
To understand how the input impedance of the respiratory system relates to pressure and volume airflow of the airway branched structure, this thesis focuses on developing a mathematical model of the branched airway including trachea and branching airways. The 5-Lobe lung model is developed mathematically and experimentally. A computer model is constructed in the MathlabTM programming environment. It accounts for the effects of airways with varying cross-sectional area, flexible wall properties, and the bronchial tree within the lung using the mathematical methods developed in previous researches. The terminal impedances are determined by proposed idealized lobe models. A range of frequencies up to 256 Hz are tested on this model. Cases of study on obstructions by varying lung stiffness from healthy to unhealthy conditions are investigated.Mathematical model is validated by experiment investigations on the mechanical lung simulator, which is built in Diagnostic & Control Research Centre at Auckland University of Technology. The results conclude that mathematical methods used in this research are capable to produce predictable results of the input impedance.
An Investigation Into the Dynamic Response of Vocal Folds
(Auckland University of Technology, 2006) Lan, Hai
During phonation, the vocal folds collision during the glottal closure is considered to be a risk factor for pathological development. This thesis is aimed at designing a dependable finite element analysis (FEA) model of the vocal folds for frequency and dynamic analysis and for calculating the impact stress between the vocal folds during glottal closure. A three-dimensional model with irregular geometry and a layered structure was designed. The measured viscoelastic properties of the vocal-fold mucosa and the transverse isotropic elastic properties of the vocal fold muscle are applied to the model. The boundary conditions are assumed to be fixed on lateral, anterior and posterior surfaces based on anatomical structure analysis. This model is symmetrical about the right and left vocal folds. The frequency and dynamic characters are presented using the software ABAQUS. The FEA model is validated by both experimental modal analysis (EMA) model results and in-vivo experimental results from the literature. In the vibration analysis, the eigenfrequency and eigenmode of the FEA model are determined. The model results compare well with the experiments performed on a silicone vocal fold model. The eigenmodes show the vibration direction at different excitation frequencies. In the closure process, the closure and collision dynamic results are obtained. The results show that: (1) the closure process is independent of the subglottal pressure; (2) the glottal opening amplitude and closing velocity vary approximately linear with the subglottal pressure; (3) the maximum impact stress occurs on the mid area of the inferior surfaces; (4) the impact stress is approximately linear with the subglottal pressure; and (5) the impact stress will cause vocal fold tissue damage when the subglottal pressure is over 800 Pa. It is anticipated that the model will help to identify voice disorders such as vocal-fold paralysis and vocal-fold nodules.
An Investigation into Using Ultrasound for Airway Humidification
(Auckland University of Technology, 2023) Uddin, Riaz
Humidification is an essential process required in many lungs therapeutic devices to overcome the complications caused by dry air in the lungs. The humidification requirements for medical devices are quite different from those for currently available ultrasonic humidifiers. For breathing devices, humidifiers need to produce vapours with droplets of less than 1 µm in diameter, while all other ultrasonic droplet generation devices reported to date cannot consistently generate required diameter droplets. The existing humidifier mechanisms for medical devices are traditional heat transfer devices that add bulky circuitry to the system. The required vaporisation for lung therapeutic devices can be achieved through accelerated evaporation using high-intensity ultrasound impact on droplets. This study explores an alternative approach for generating a strong ultrasonic field that can facilitate the rapid evaporation of droplets, a key requirement for human airway humidification in therapeutic devices such as the Continuous Positive Airway Pressure (CPAP) device. The technique involves applying high-intensity ultrasound to droplets to accelerate their evaporation. The ultrasonic levitation mechanism uses high-intensity ultrasound that can hold droplets. By precisely controlling the frequency and intensity of the ultrasound waves, it can also be used to effectively impact droplets during evaporation if placed as the second stage ultrasonic field. Various options for high-intensity ultrasound field transducers were researched, and with the aid of theoretical investigation and CAD with FEA analysis, the design of a levitator was formed and implemented. The levitator's output was measured, and its interaction with droplets was experimented. The results provide the significant impact of the ultrasonic field on droplets accelerated evaporation. The research has proposed a novel design for an ultrasonic humidifier that can be used in human airways and will help reimagine humidifiers for CPAP systems. It will aid in decreasing the size of the humidifier, which will allow better equipment mobility and improve power efficiency. Ultrasonic humidifier studies will not be restricted to the humidification and miniaturization of the CPAP system but will also help in redesigning humidification systems for other relevant respiratory therapy equipment, such as ventilators.
Artificial Neonatal Airway Model
(Auckland University of Technology, 2011) Mussa, Jibril Siraj
The main aim of this project is to establish the effectiveness of Bubble CPAP in transmitting pressure oscillations through the neonatal tracheobronchial tree. As it is very difficult to establish how much of the pressure oscillation delivered to the mouth can reach the various branches during in-vivo measurements, this research focuses in developing an in-vitro experiment on the lung model. Hollow lung models for 128 and 142 day gestation lambs were created from existing silicon lung casts. An experimental setup using a lung simulator and pressure sensors was developed. Different combinations of respiratory rate and frequencies with different amplitudes were used to perform experimental tests. The current ovine respiratory system which was available at IBTec was modified to reflect the current experimental setup. Computer simulations were performed and compared with the experimental results. The study indicates that pressure waves with different frequencies can be delivered to different locations of the lung by controlling the pressure oscillation source to the lung.
Asthma and COPD Risk Prediction From Respiratory Sounds Using Deep Learning
(Auckland University of Technology, 2024) Ali, Md Jahan
In recent years, Deep Learning (DL) models have offered many promising improvements for the early detection of respiratory diseases like asthma and Chronic Obstructive Pulmonary Disease (COPD), using techniques such as audio analysis and imaging. Chronic respiratory diseases, as documented in global health statistics, have emerged as the third most prevalent cause of mortality worldwide. In the year 2019 alone, these diseases were responsible for an estimated 4 million deaths internationally. This substantial figure serves to illuminate the extensive and profound impact that respiratory diseases exert on the global health landscape. Statistical analyses indicate that a significant majority of chronic respiratory disease cases, exceeding two-thirds, are primarily attributed to either asthma or COPD. However, the high degree of diagnostic overlap between chronic pulmonary conditions of asthma and COPD, owing to their similar symptomatology, significantly contributes to diagnostic inaccuracies, leading to considerable mortality annually. To confront the pressing challenge presented by the high prevalence of respiratory diseases, particularly asthma and COPD, this study introduces an enhanced DL framework, employing a sophisticated multilayer Convolutional Neural Network (CNN) as the basis for a classifier model. This model is meticulously designed to identify and distinguish between asthma and COPD. Through the application of advanced CNN methodologies, the proposed model aims to augment the accuracy and efficiency in the diagnosis and differentiation of these two prevalent respiratory conditions, thereby contributing significantly to the field of medical diagnostics and treatment optimization. It entailed a comprehensive analysis involving the extraction of features and the development of a DL model aimed at differentiating between these two predominant respiratory diseases. The study utilized a sample of 200 respiratory sound recordings, of which 120 were allocated for training purposes and 80 for testing. The methodology encompassed extracting log energy (LE) and Mel energy from the Mel Frequency Cepstral Coefficients (MFCC) features of lung sounds as the foundational elements for classification. A variety of classifiers, including Support Vector Machine (SVM), Random Forest, k-Nearest Neighbor (KNN), and Multilayer Perceptron (MLP), were utilized. These classifiers primarily focused on discriminating between asthma and COPD based on lung sound features. Notably, the enhanced DL model achieved a significant classification accuracy of 86.25% when employing the SVM classifier. Moreover, the model demonstrates notable enhancements across key performance metrics, achieving a Sensitivity of 87.81%, Specificity of 55.31%, and an F1 Score of 77.51%. Tailored to precisely predict asthma and COPD, this model stands out for its capability to accurately identify these conditions. The adoption of such an advanced diagnostic tool in clinical settings can enhance the efficiency of medical practitioners, enabling them to make quicker, data-driven decisions.
Biodegradable Polymer Blends/Composites, With High Performance Characteristics, for Packaging Application
(Auckland University of Technology, 2021) Govindan, Srinivasan
This research project focuses on developing biodegradable polymer films for flexible packaging applications with high-performance characteristics. During this research, three biodegradable polymers, namely, Polybutylene succinate (PBS), Polyhydroxybutyrate (PHB), and Polylactic acid (PLA), were selected and investigated to improve their performance. Three strategies were adopted for improvement; namely, i) by blending with Polycaprolactone (PCL), a highly biodegradable polymer, ii) by plasticization with three plasticizers, and iii) by the fabrication of nanocomposites/ by incorporating nanomaterials such as nano-cellulose and nano-clay. Polymer films of various compositions were fabricated by injection molding, followed by hot-pressing and carried out an investigation of the tensile properties, water vapor transmission rate (WVTR)/ barrier properties, and biodegradability characteristics (in-home compost & seawater medium) of polymer films, and analyzed the effect of blending, plasticization, and nanomaterials. The investigation carried out on blending of PBS, PHB, and PLA with PCL (with 10, 20, 30, and 40 wt% PCL) demonstrated enhancement of tensile elongation (ε), improvement in water vapor barrier property (decrease in WVTR), and increase in the biodegradation rate (in-home compost and seawater), with the addition of PCL, though with a slight decrease in tensile strength (σ). It was concluded from the studies on blending that polymer blending with approximately 10-20wt % PCL offer overall enhancement of polymer properties. Studies carried out on plasticization of PBS-PCL20, PHB-PCL20, and PLA-PCL20 blends, with three plasticizers, [GTA, a monomeric plasticizer P1; Ultramoll, a polymeric plasticizer P2; and mixed plasticizer P3 ( 1: 1 mix of P1 and P2)], with 5 wt% plasticizer loading, indicated, a substantial increase in elongation at break and biodegradability, with the addition of all the three plasticizers, though with a decrease in tensile strength (σ) and water vapor barrier property. It was concluded from the plasticization study that mixed plasticizer P3 offers the best overall performance enhancement. An investigation carried out on nanocomposites of PBS, PHB and PLA, prepared by incorporating nano cellulose and nano clay ( 1, 3, and 6 wt%) in plasticized blends, ( PBS-PCL20-P3, PHB-PCL20-P3, and PLA-PCL20-P3) demonstrated improved water vapor barrier properties (decrease in WVTR), improved tensile strength (except for PLA), and higher biodegradation rate with the addition of both nano cellulose and nano clay. Though a decrease in elongation at break was observed with nanomaterials' addition to the plasticized blends, the cumulative improvement was observed for neat polymers. Studies on nanomaterial content's effect indicated that the best performance was obtained with 1wt % nano cellulose and 6% nano clay, which differ only slightly in properties. The nanocomposites with nano cellulose (1wt%), namely PBS-PCL20-P3-nCell1, PHB-PCL20-P3- nCell1, and PLA-PCL20-P3- nCell1 was found to have improved properties, such as higher tensile elongation by 50%, 168%, and 494%; higher water vapor barrier properties (lesser WVTR) by 59%, 46% and 48%; higher biodegradation rate in home compost media by 56%, 13%, and 93%; and higher biodegradation rate in seawater media (after 180 days) by 79%, 10%, and 92% respectively, compared to neat PBS, PHB and PLA. The nanocomposites with 6 wt% nano clay were found to have slightly higher tensile strength and water vapor barrier properties, though slightly lower ductility and biodegradability. Hence nanocomposites with 1% nano cellulose or 6% nano clay may be used depending on the application requirement. The present investigation thus demonstrated the overall performance improvement of PBS, PHB, and PLA polymers through blending, plasticization, and nanomaterials. The present investigation has also generated valuable data on biodegradation of PBS, PHB and PLA polymers, PCL blends, plasticized blends, and nanocomposites under ambient temperature/ home composting conditions and marine environment, which will be of great help for future researchers.
Breathing Therapy Air Delivery Unit: Simulation, Design and Development
(Auckland University of Technology, 2003) White, David Edward
Although constant positive airway pressure therapy is currently the most effective form of non-invasive treatment to relieve obstructive sleep apnea symptoms, it has relatively low treatment compliance due to pressure related side effects. Existing commercial continuous positive airway pressure (CPAP) devices rely on the combined airflow characteristics of both the air delivery unit and nasal mask vent to regulate treatment pressure. Fluctuation in mask pressure occurs however, due to patient breathing, presenting an opportunity to develop an alternative breathing therapy device capable of achieving dynamic control of mask pressure. Within this research, a computer model of a proposed patient breathing therapy device, based on characteristics of a prototype system, is developed to determine the breathing system air delivery requirements whilst operating under a simulated patient breathing load. This model initially utilises an idealised, zero order, air delivery unit behaviour, since this system element is yet to be built. A review of different types of air compressors is undertaken and the diaphragm type compressor selected as being best suited for practical implementation within the air delivery unit of the breathing system, based on constraints of air quality, available machining resource and materials. Thermodynamic design of the compressor is undertaken to determine physical dimensions and a range of actuation methods are reviewed, based on force and speed requirements. A speed controlled 3 phase AC induction motor is selected to actuate the compressor. The diaphragm compressor is built and tested under both steady state and dynamic conditions and proven capable of meeting the breathing system air supply for both air pressure and flow requirements. The air delivery unit within the model simulation, previously based on an idealised, zero order element, is characterised with the same dynamic behaviour as the prototype unit built, established during testing, and shown by simulation to meet the breathing system requirements under dynamic patient breathing load. Implementation of the air delivery unit within the completed prototype breathing system shows the mask pressure to fluctuate outside the desire pressure tolerance range; however, to remedy this situation, the compressor requires the development of an appropriate control scheme which is beyond the scope of this work.
Combined Map Personalisation Algorithm for Delivering Preferred Spatial Features in a Map to Everyday Mobile Device Users
(Auckland University of Technology, 2010) Bookwala, Avinash Turab
In this thesis, we present an innovative and novel approach to personalise maps/geo-spatial services for mobile users. With the proposed map personalisation approach, only relevant data will be extracted from detailed maps/geo-spatial services on the fly, based on a user’s current location, preferences and requirements. This would result in dramatic improvements in the legibility of maps on mobile device screens, as well as significant reductions in the amount of data being transmitted; which, in turn, would reduce the download time and cost of transferring the required geo-spatial data across mobile networks. Furthermore, the proposed map personalisation approach has been implemented into a working system, based on a four-tier client server architecture, wherein fully detailed maps/services are stored on the server, and upon a user’s request personalised maps/services, extracted from the fully detailed maps/services based on the user’s current location, preferences, are sent to the user’s mobile device through mobile networks. By using open and standard system development tools, our system is open to everyday mobile devices rather than smart phones and Personal Digital Assistants (PDA) only, as is prevalent in most current map personalisation systems. The proposed map personalisation approach combines content-based information filtering and collaborative information filtering techniques into an algorithmic solution, wherein content-based information filtering is used for regular users having a user profile stored on the system, and collaborative information filtering is used for new/occasional users having no user profile stored on the system. Maps/geo-spatial services are personalised for regular users by analysing the user’s spatial feature preferences automatically collected and stored in their user profile from previous usages, whereas, map personalisation for new/occasional users is achieved through analysing the spatial feature preferences of like-minded users in the system in order to make an inference for the target user. Furthermore, with the use of association rule mining, an advanced inference technique, the spatial features retrieved for new/occasional users through collaborative filtering can be attained. The selection of spatial features through association rule mining is achieved by finding interesting and similar patterns in the spatial features most commonly retrieved by different user groups, based on their past transactions or usage sessions with the system.
Computational Fluid Dynamic Modelling for Arterial Diseases Assessment
(Auckland University of Technology, 2012) Al-Rawi, Mohammad
One of the leading causes of death is cardiovascular disease, being 30% of all deaths worldwide and 40% of those in New Zealand. In other words, every 90 minutes a New Zealander dies due to cardiovascular disease. Cardiovascular mortality is higher in New Zealand than Australia, but the reasons for this are not clear. Although Australia and New Zealand are similar politically, culturally, and socioeconomically, mortality from cardiovascular disease is about 25% higher in New Zealand than in Australia. In recent years, engineers and scientists have collaborated with the medical community to find new methods and approaches for assessing and investigating the development of cardiovascular diseases such as abdominal aortic aneurysm and atherosclerosis. In this thesis, atherosclerosis and aneurysm diseases are investigated and analysed using computational fluid dynamic/finite element (CFD/FE) methods. These models are validated against the in vivo and in vitro experiments performed on animals. The experimental models are also investigated; the assessment of arterial blockages using blood pressure waveforms obtained invasively at the right femoral artery. The animal experiments are performed following appropriate ethical protocols (R915) on Wistar rats weighing between 250-350g. An arterial blockage is created surgically within the abdominal aorta of healthy animals to create an unhealthy condition. Blood pressure waveforms are measured by injecting catheter into the right femoral artery of the rat. These measurements are taken at the baseline (healthy condition) and at four different severities of arterial blockage of the abdominal aorta for the same specimen. In vivo and in vitro measurements of the arterial diameter and wall thickness are also taken using Magnetic Resonance Imaging (MRI) and microscopic techniques, respectively. These data are then input onto CFD/FE models in order to develop a new, non-invasive method of assessing arterial blockage. The experimental and computational results indicate that arterial blockages occurring within the abdominal aorta could be assessed, and the development of the disease diagnosed, very clearly and non-invasively at the right femoral artery. The findings of the animal model are then implemented in the human model for screening atherosclerosis and aneurysm at the brachial artery. These diseases are modelled and simulated in a 3D CFD/FE aorta geometry using the fluid–structure interaction (FSI) approach on the commercial software ANSYS®14.0. Literature blood flow waveform datum is assumed at the inlet and invasive catheter pulsatile pressure waveforms data is imposed at the four outlets of the aorta (provided by Green Lane Hospital under ethic approval number NTX/09/11/109). Correlations between the stress phase angle (SPA), augmentation index (AI), lumen diameter and blood pressure waveforms for various scenarios of diseased models are made and compared to the control model. The results show that CFD/FE models with different radii and thicknesses at the abdominal aorta significantly influence blood pressure waveforms, high negative SPA values, and high AI detected at the brachial artery.
Design and Development of an Optimised Telemetry Control System
(Auckland University of Technology, 2011) Salig, Avinash
Designing an optimised telemetry control system will improve the quality of service for Supervisory Control And Data Acquisition (SCADA) systems implemented by CSE-W. Arthur Fisher and enable system expansion thus minimising revenue for their future system designs. The telemetry control system ensures a high degree of data reliability and integrity to meet SCADA operational requirements. This thesis presents the design and development of an optimised telemetry control system using Kingfisher Remote Terminal Units (RTU’s) with Kingfisher Series 2 protocol. To determine the system response for data transmission over the bandwidth, quantitative research methods were undertaken to evaluate communication blocks within the Kingfisher protocol. There are usually different techniques used to collect data from remote stations. The Kingfisher S2 protocol implements two techniques namely “Exception Reporting” and the “Polling” technique for data acquisition. The polling technique was the most efficient in terms of bandwidth utilization for transferring data therefore the system was designed using a pure polling system approach. It also enabled the communication links for remote stations to be monitored and enabled a deterministic system design approach to be implemented. Research focused on polling system optimization whereby efficient polling frequencies were calculated based on theory presented by (O. J. Boxma, Levy, & Weststrate, 1991). The aim was to efficiently allocate the limited bandwidth resource to a number of remote stations thus optimising the system performance. The proposed theory was implemented for system optimisation. It enables efficient polling frequencies to be calculated for a polling cycle hence optimising the bandwidth utilisation and eliminating fairness problems for the medium access control. Bandwidth optimisation enables system expansion thus reducing the networks need for additional resources. A pure polling telemetry communication system was implemented in this design using point to multipoint network topology over half duplex radio channel. Empirical data modelling enabled the design of the service duration period to allow for time sharing between the remote stations to share the bandwidth. The bandwidth was designed to share real time data and event log for SCADA systems monitoring and control. Queuing analysis was performed to establish system parameters and enable system optimisation. From the literature review the implemented design methodology uses the “mean delay approximation” method which was used to calculate efficient visit frequencies and enabled the optimisation of the bandwidth to the remote stations based on the workload of each remote site. The software for the telemetry control system was developed and tested using ladder logic. The results prove that the bandwidth utilisation can be efficiently controlled thus optimising the telemetry control system. The implemented design improves the quality of service for the SCADA system by providing regular real time system status poll requests for control purposes and was given the highest priority for medium access. It also performs a polling of individual sites according to the “mean delay approximation method” to efficiently allocate bandwidth amongst the remote stations depending on their workload thus optimising the system. The system was designed to be responsive to high priority event log data thus enabling system flexibility.
Development of a Novel Humidifier for Air Breathing Devices
(Auckland University of Technology, 2011) Brizio, Pablo Joaquin
Continuous positive pressure of air on the airways (CPAP) is the most common treatment for the obstructive sleep apnea syndrome. Humidification of the air applied to the patient improves patient compliance by preventing congestion and nasal and throat dryness. Most humidifiers used in CPAP systems are traditional heating-type humidifiers which consume large amount of energy. In this thesis, a non-traditional humidification technique was developed to be used in various respiratory supportive device applications such as CPAP therapy. Atomization processes were reviewed and ultrasonic atomizers were found to be the most suitable in terms of power consumption, droplets size distribution of the spray generated and size of the device. Four setups were used for experiments with these atomizers using five frequencies (1.5, 1.7, 2.1, 2.6 and 3.0 MHz). The experiments demonstrated that excitation with sine pulses has better efficiency than square pulses. In order to avoid overheating of the ultrasonic atomizer, the pulses must be sent in bursts and the frequency at which this bursts are sent (duty cycle) was proportional to the heating of the transducer. The droplet size distribution was measured by three different methods (photographic, impact and optic) and it did not have a significant change with the power applied to the transducer. The power did have a direct relationship with the atomization rate. Ultrasonic transducers with resonant frequency of 1.5 MHz are recommended for this application since the generated droplets have a small diameter (which facilitates its evaporation). The complexity of a driving circuit also increases with the frequency. Ideally there should be no water droplets in the air supplied to the patient. The evaporation of the droplets was mathematically modelled and experimentally tested to determine if the air that will be supplied needs to be heated to reach the fully evaporation. With an airflow rate of 60 L/min, the full evaporation of the droplets was reached in a relatively short distance (0.05 m) compared with the normal separation between the equipment and the patient (1.50m). There is no need to use a heater achieve such evaporation of the droplets. In this device, the pathogen risk could be reduced with the use of hydrophobic filters. This work demonstrates that ultrasonic transducers are capable of atomizing sufficient quantities of water for this application with low power consumption.
Effect of Mechanical Pulse Oscillations on Airway Smooth Muscle
(Auckland University of Technology, 2011) Theodore, Solomon
The airway smooth muscle (ASM) plays an important role in the mechanism of respiratory system. Asthma, a common respiratory disease is associated with ASM hyper-contraction and shortening of airway diameter. This results in occlusion of the airway lumen leading to breathing difficulties. Various studies have shown that ASM can be relaxed by length oscillations. Previous experiments on ASM by applying sinusoidal oscillation at low frequencies and high amplitudes have showed a clear reduction in active force. Similar tests for a larger frequency range on ASM have also shown large reduction in dynamic force. But, it is not well known what parameters induce relaxation the most on ASM. The purpose of our research is to see the degree of relaxation when superimposed oscillations are applied on breathing and see which parameter relaxes smooth muscle the most. This research also focuses on investigating the effect of pulse oscillation rather than sinusoidal oscillation on contracted ASM. Isolated ASM were tested using pulse oscillations with wide range of frequency, amplitude and duration. Results obtained from these experiments showed that pulse oscillation with short duration had significant effect on the relaxation of ASM compared to sinusoidal oscillations with longer duration.
The Effect of Pressure Oscillations on Respiratory Performance
(Auckland University of Technology, 2009) Reddy, Prasika Inderjeeth
This thesis is aimed at understanding the effective operation of the Bubble CPAP System when treating neonates with respiratory distress syndrome (RDS). It is also aimed at determining the effect that pressure oscillations have on respiratory performance in terms of the work of breath (WOB) and surfactant dynamics. The principle objectives were to: • Create an original multi-compartmental model of the neonatal lung that includes compartment-specific inertance and viscoelasticity for 128 day (premature) and 142 day (near-term) gestation lambs. • Validate the model with experimental data obtained from clinical trials. • Use the model to determine the effect of pressure oscillations as produced by the Bubble CPAP System on respiratory performance. • Determine the frequencies of oscillation that provide the optimal respiratory support. • Build a surface tension model that simulates surface tension dynamics in an alveolus exposed to pressure oscillation frequencies in the range typically produced by the Bubble CPAP System. • Validate the surface tension model with experiments conducted on a custom-built pulsating bubble surfactometer (PBS). To fulfill the first four objectives, a mathematical model of the neonatal ovine lung was developed in Simulink within the Matlab environment. Mechanical and physical parameters that were required for the model were either empirically determined from measurements on preterm lamb lungs or derived from the literature. Simulations were then performed to determine the effectiveness of Bubble CPAP and the use of ‘optimal frequencies’ in neonatal respiration. To study the surface tension dynamics, a PBS was constructed to study the effect of frequencies on a surfactant bubble which simulated an alveolus. Modulated frequencies (10-70 Hz) were superimposed on the breath cycle at 3 different amplitudes expressed as a percentage of the tidal volume (TV) excursion (15%TV, 22.5%TV and 30%TV). A numerical model was also built in Matlab to characterize the surfactant behaviour and help determine the mechanisms responsible for any observed changes in surface tension. The experimental results and computer simulations resulted in the following conclusions: • The model is able to accurately predict the respiratory parameters at the airway opening during CPAP and Bubble CPAP operation. • The model shows the ability to predict the uneven ventilation profiles in the neonatal lung. • Both model predictions and experimental measurements show the trend that the mechanical WOB is greater (improved) during ventilation under Bubble CPAP when compared to CPAP. • Pressure oscillation frequencies which show improved WOB measures in the 128 day gestation lamb lung were identified as 19, 23, 28, 33, 44, 49, 54, 81, 88, 99, 111 and 113 Hz. • Model predictions showed that the improvement in WOB (due to mechanical effects) relative to CPAP-only treatment was 1-2% when introducing single frequencies at the generator, but increased to 4-6% when introducing ‘mixed frequencies’ at the generator and 4-10% when introducing ‘mixed frequencies’ at the patient interface. • It was shown that the Bubble CPAP System delivers frequencies similar to the identified optimal frequencies of the 128 day gestation lung (17 and 23 Hz) which contribute to the noticed improvement in WOB. • The average trends of all the experiments on a PBS and results from the numerical model revealed that the minimum and maximum surface tension in an alveolus decreases with increasing frequency and increasing amplitude. • The mechanism of improvement of surface tension in the alveolus with frequency and amplitude is due to the increased diffusion and adsorption of surfactant molecules to the air-liquid interface, increasing the interfacial surface concentration and decreasing the surface tension.
Effects of Combined Bronchodilators and Oscillations on the the Airway Smooth Muscle Response
(Auckland University of Technology, 2011) Mathur, Meha
The current study aims to investigate the combined effects of oscillations and bronchodilators on the dynamics of the isolated contracted airway smooth muscle. Current day asthma treatments commonly use bronchodilators such as Isoproterenol to reduce the symptoms of asthma. Previous studies have shown the ability of length oscillations (such as those occurring during tidal breathing and deep inspirations) to have a bronchodilatory effect on normal activated airway smooth muscle both in vitro and in vivo. However, this effect is absent or transient in asthmatic airway smooth muscle. Although, many studies have been conducted to possibly understand the role of oscillations on the airway smooth muscle (ASM) dynamics, the exact mechanism is still unclear. Many studies have been conducted to look at the effects of length oscillations or perturbations on the contracted ASM dynamics, along with separate set of studies investigating the behaviour of ASM in the presence of bronchodilators. This study is novel in the sense that it experimentally investigates the effects of bronchodilators combined with length oscillations of varying parameters on the isolated airway smooth muscle. The experimental data suggest that the combined effect of the bronchodilator Isoproterenol and length oscillations is higher than that of each when applied alone. This response has been tested by varying the amplitudes and frequencies of the oscillations. The relaxation of the ASM subsequent to the application of oscillations was found to be proportional to the amplitude, but independent of the frequency of oscillations. This study gives more insight into the role of bronchodilators and oscillations (such as while breathing) on the contracted airways in an optimal goal of developing a new treatment methodology for asthma.
Elimination of Skin-stretch Induced Motion Artefacts from Electrocardiogram Signals
(Auckland University of Technology, 2017) Kalra, Anubha
Electrocardiography (ECG) is widely used in clinical practice, for example to diagnose coronary artery disease or the cause of chest pain during a stress test, while the patient is running on a treadmill. Ambulatory ECG monitoring is used for long term recording of ECG signals, while the patient carries out his/her daily activities. Artefacts in ECG are caused by the patient’s movement, moving cables, interference from outside sources, electromyography (EMG) interference and electrical contact from elsewhere on the body. Most of these artefacts can be minimised by using proper electrode design and ECG circuitry. However, artefacts due to subject’s movement are hard to identify and eliminate and can be easily mistaken for symptoms of arrhythmia and the physiological effects of exercise, leading to misdiagnosis and false alarms. Skin stretch has been identified as a major source of motion artefacts in ECG signals, which arise due to the flow of current, called the ‘injury current’ across the epidermis. Thus, the skin is generally abraded or punctured to minimize variations in injury current. This is unpleasant and not useful for long term monitoring, as the skin regrows after 24 hours. Present motion sensing approaches to artefact reduction in ECG do not measure motion in terms of skin stretch. The main goal of this study is to quantify and eliminate motion artefacts from ECG pertaining to skin stretch. A polymer patch electrode with Young’s modulus lower than of skin has been developed to simultaneously measure ECG and skin stretch using an optical sensing technique. These signals were combined with infinitesimal strain theory to quantify skin stretch as two dimensional strains. Principal component analysis (PCA) and independent component analysis (ICA) were utilised for motion artefact removal from ECG signals. A motion Artefact Rejection (AR) system has been developed to validate the approach implemented in this study. As this study mainly focuses on skin stretch induced artefacts, a plastic tube has been used to stretch the forearm skin of 7 subjects across the following age groups: 18–35 years (3 subjects), 36–55 years (2 subjects), and 56 years and above (2 subjects). ECG with motion artefacts were measured using CNT/PDMS electrodes and dry Ag electrodes. The reference ECG (ECG at rest) was measured from the chest using conventional Ag/AgCl electrodes. The average improvements in SNRs using PCA and ICA algorithms were found to be 4.249 dB and 9.586 dB respectively, while the average of maximum deviation from rest/reference ECG was 0.0843 for ECG with motion artefacts, 0.0702 for ECG after PCA and 0.0442 for ECG after ICA. Both PCA and ICA algorithms also aided in removing baseline wander and high frequency noises in the cases of less or no motion artefact. The system performed well in removing artefacts generated due to EMG interference and stretching the skin perpendicular, diagonal and parallel to Langer’s lines. Higher SNRs were achieved when PCA and ICA were performed by using 2D strains as motion information than when no motion information was used. In conclusion, ICA used for motion artefact reduction in ECG signals shows better performance than other techniques employing adaptive filtering, PCA and ICA. A novel, state-of-the-art technique to identify and eliminate motion artefacts from ECG signals has been developed through this study which is feasible for practical implementations.
An Experimental Investigation Into Heatless Self-Humidifying Breathing System
(Auckland University of Technology, 2022) Al-Attar, Ahmed Kaleem Muez
Many developments have been conducted on heat and moisture exchange devices to recover heat and moisture from expired air to condition the inspired air for lung supportive devices. Available methods typically require an external heat source to achieve the objectives. However, most available HME devices have limited capabilities, such as delivering insufficient heat and moisture to the patient, causing breathing restriction and increasing dead space levels in the system. The Institute of Biomedical Technologies (IBTec) at Auckland University of Technology (AUT) has developed a novel moisture exchanger material for a self-humidification feature. However, this material requires a micro-electrical heat generator as a heat source to achieve its objectives. The device absorbs water vapor from human exhalation when the surrounding temperature is lower than its thermal threshold and releases the vapor when temperature increases by the micro-electrical heat generator above that edge. This research aims to investigate further the possibilities of optimizing this respiratory supporting system to become a heatless system and eliminate the need for the micro-electrical heat generator by integrating a suitable self-heating element utilizing an exothermic chemical reaction to absorb heat during the exhalation process and delivers the heat in the inhalation process. Such development is expected to reduce device expense, power usage, and size of the breathing system, become user-friendly, and increase efficiency safely and securely. This research will investigate different approaches to develop and optimize a new system with self-humidification and heatless features.
Experimental Techniques to Determine the Young's Modulus of the Trachea
(Auckland University of Technology, 2004) Hermawan, Vera
In addition to its usefulness in modeling and simulation processes, the modulus of elasticity is an index which is highly used in biomedical identifications and tissue characterizations. For many composite and viscoelastic materials an "accurate modulus" is an idealistic hypothesis and an "equivalent modulus" is normally of a high biomechanical significance. The composite shape of the trachea, which consists of the smooth muscles and cartilage rings, renders the fact that an equivalent modulus is in place for many applications. In this paper three in-vitro nondestructive testing techniques are presented to determine the Young modulus of elasticity of the trachea and the results are compared with the standard uniaxial state of stress method. These techniques are based on: (1) simulating the trachea as a pressurized vessel and deducing a special relationship between the pressure and the radial strain; (2) using two hydrophones and studying the variation in acoustic transmittance caused by the presence of the trachea in a water-bath; (3) considering the trachea as a thin cylindrical shell and determining the resonance vibration response. Elaborate discussion is presented to identify the "pros" and "cons" of each technique and final practical recommendations are made.

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