Current Research
Respiratory disorders are common in both developed and developing countries. Many of these disorders are directly connected to constrictions in the airways of the human respiratory system. Asthma and bronchitis are typical examples of diseases which arise from the constriction of airways. Asthma is a respiratory disease that is characterised by chronic inflammation, hypersensitivity and obstruction of the airways. During an asthma attack contraction of airway smooth muscles and mucous production cause reduction of the bronchial diameter, significantly changing the airflow resistance in and out of the lungs.
While medicine helps relieving pains and curing diseases, there is no medicine without side effects. In asthma these side-effects can be terminal, and often the effectiveness of the medications is limited. The main aim of the respiratory system dynamics group is to identify non-conventional techniques of relieving constrictions in the airway passages such as those caused by asthma to minimise the need for medication. Using our expertise in the vibration response of biomedical systems IBTec is investigating the feasibility of using vibrations to relax airway smooth muscle and consequently relieve asthma.
Current Research
CRT presently conducts research into four main areas involving respiratory and sinus conditions. These include asthma, obstructive sleep apnea (OSA), respiratory distress syndrome (RDS) and chronic rhino-sinusitis.
Asthma
- Vibration relaxation of airway smooth muscle
We have shown that airway smooth muscle can be relaxed using vibrations. The aim of this research is to identify which processes in airway smooth muscle are responsible for the relaxation, and to determine the amount of force reduction caused by vibrations in the range between 0 and 100 Hz.
Firstly, this research is conducted at tissue level, using finite element modelling with purpose built material models to describe force reduction due to vibrations.
Secondly, the actual processes responsible for force generation and relaxation in the airway smooth muscle cell are investigated to create an all-inclusive mathematical model of the dynamic response of airway smooth muscles.
- A Dynamic Investigation of Airways
The respiratory system consists of a series of branching tubes which become narrower, shorter and more numerous as they penetrate deeper into the lung. From a mechanics point of view, the walls of these passages are composed of viscoelastic material. A system that possesses mass and elastic properties exhibits natural frequencies at different modes of vibration, which are inherent to the system.
The respiratory system and devices group has focused on the area of the acoustic and vibration response of the lung for the last nine years. This has resulted in a published theoretical model, supported by experimental validation that predicts the dynamic characteristics of airways in terms of the natural frequencies of the branched tree structure.
Obstructive sleep apnea (OSA)
Some of IBTec’s most significant research projects have involved work on Continuous Positive Airway Pressure(CPAP) and Bubble CPAP devices with Fisher & Paykel Healthcare. These include:
- Transient Breathing System
This project focuses on the development of a dynamic model for an artificial breathing system designed by Fisher and Paykel Healthcare Ltd. The main air supply for this system is a variable-stroke compressor, which controls the mask pressure. The model is computer simulated to investigate the response of the system for various input parameters including controller analysis.
- Design & Development of Adaptive Positive Airway Pressure (APAP) Device (4 projects involved)
This project is very significant in developing a new type of constant positive airway pressure (CPAP). It further extends the previous theoretical model by relaxing some of the imposed constraints and allowing more realistic physical and practical variations to develop a final compressor design. An optimisation for the whole breathing circuit including a new control scheme was achieved. A compressor is built and we investigated its performance as embedded within the "Transient Breathing System".
- Control of Pressure Source for Treating Sleep Apnea
The purpose of the project was to investigate, develop and test various control schemes to enable dynamic control of the mask pressure in an existing (CPAP) blower used by sufferers of Obstructive Sleep Apnea, i.e. a Bi-Level Positive Airway Pressure (Bi-PAP) system.
- Effect of Continuous Positive Airway Pressure on Upper Respiratory Airways Performance
A Nasal Continuous Positive Airway Pressure (nCPAP) breathing-assistance device involves using a small air blower to produce positive pressure and transfer the pressurized air to the nose through a supply tube and a mask. A common side effect for patients who are using an nCPAP machine is a sore and dry nose and throat. To prevent the side effects of using nCPAP, a humidifier has to be added to the system. However, analyses on the nasal cavity and upper airway mechanisms do not yet exist for this purpose. This research intends to create simulation models to predict the behaviour of nasal cavity and upper airways under various nCPAP settings (i.e. positive pressure, humidifier and heated breathing tube settings). The model will be validated with experiments.
- CPAP MASK-Thermo-fluid Dynamics for Carbon Dioxide Reduction
The goal is to build a CPAP mask which can reduce carbon dioxide (co2) concentration to a safe threshold over the entire pressure range of 0 to 20 cm H2O(0-0.2 KPa) inside the mask.
- The Relationship Between Incubator Radiant and Convective Heating with Body Size
Premature infants are incapable of maintaining their core body temperature. This research aims to investigate the heat exchange relationships that occur between the infant in the incubator, the radiant warmer and the surrounding environment.
The research involves studying all the interactions between the compartments of each device separately. This involves creating a model which contains a mixture of physiological data related to the infant and normal heat transfer formulas.
- Modelling and Optimisation of the CPAP flow sensor
This project aims to model and optimise the CPAP machine flow sensor. This will improve the accuracy of the machine and help Fisher & Paykel Healthcare in determining the optimum placement of the Sensor.
- Simulation of humidification in CPAP incorporating the human breath cycle
The level of humidity at the mouth when using the CPAP machine is crucial in order to avoid dry and sore throat. This project aims to simulate the humidification in the CPAP machine and incorporate the breath cycle.
- The Effect of tube back flow in Mask Conditions
The goal of this project is to develop a mathematical model validated by experimentation that can predict the condensation and potentially, the carbon dioxide levels in the CPAP breathing tube.
- Simulation and Design and Feasibility study of an automatic regulation CPAP Device
This project intends to develop an automatic positive airway pressure device that uses airway models and physiological information of the lungs to regulate the applied pressure. Therefore system will apply the minimum pressure to the airway to keep it open and will change the minimum pressure depending on changes in the breathing pattern. This will hopefully increase compliance as the machine will be less invasive and the pressure induced side effects should be reduced as only a minimal needed pressure will be applied.
- Self- Regulating Heating Tube
In this research an experimental investigation was conducted to develop a low resistivity material which possesses positive temperature (PTC) characteristics, has heating capability and can regulate its own temperature in a relatively moderate range. Several composites made of various compositions of non-conducting ethylene vinyl acetate (EVA), plastomer (Octene-1) polymers with conductive carbon black (CB) were prepared and tested for resistivity and PTC behavior. The results showed an increase in resistivity with higher temperature. Thus the conductive filler as a host can introduce electrical conductivity; however, the polymers control the mechanical properties of the composites. The advantage of using two or more polymers over one polymer composite was clearly demonstrated. An optimum composite made of EVA, plastomer and CB was determined to give the required heating purpose and control action within the above temperature range. A heating coil made of this material was inserted in a corrugated plastic tube made of linear low-density polyethylene LLDPE and tested for supplying humid air at a temperature of 40oC. The experimental results supported by mathematical modeling have demonstrated a self-regulating temperature controlled tube is feasible for future production.
Respiratory distress syndrome (RDS)
- Effect of pressure oscillations on improvement of the Bubble CPAP method
The creation of the pressure oscillations in regard to amplitude and frequency has been studied by Fisher & Paykel Healthcare in some detail. The goal of this research is to further investigate the effects of the pressure oscillations and further improve the benefits of Bubble CPAP. The project was able to answer the following questions:
- Does CPAP with pressure oscillations more effectively open a fluid filled lung than CPAP alone?
- What pressure oscillation amplitude or power is necessary to open a liquid filled lung?
- What is the relationship between the absorption of the pressure oscillations and lung compliance?
- Can the frequency/ compliance relationship be used to determine the compliance of a non-homogenous lung?
- The Effect of Pressure Oscillations on Neonatal Breathing
This project aims to create mathematical models of the neonatal respiratory system which are able to predict its mechanical response to the pressure oscillations produced by the Bubble CPAP system. The model will consider both the viscoelastic and surface tension effects within the respiratory system. The models are to be validated by trials on live subjects in both experimental and clinical settings.
Chronic rhino-sinusitus
- Use of Vibration therapy for treatment of sinus disorders
- Use of Ultrasound therapy for treatment of sinus disorders
- Use of Electric Field therapy for treatment of sinus disorders