An investigation of cochlear dynamics in surgical and implanation processes

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The aim of this research is to improve the understanding of the impact on the cochlear dynamics corresponding to surgical tools, processes and hearing implants such that these can be designed more appropriately in the future. The results suggest that enhanced performance of implants can be achieved by optimisation of the location with respect to the cochlea and have shown that robotic surgical tools used to enable precise, simplified processes can reduce harm and offer other benefits. With an ageing population, and where exposure to noise on daily basis is increased rather than industrial settings, at least two factors of age and noise, will contribute to a greater incidence of hearing loss in the population in the future. In the research a mathematical model of the passive cochlea was produced to increase understanding of the sensitivity and behaviour of the fluid, structure and pressure transients within the cochlea. The investigation has been complemented by an innovative experimental technique developed to evaluate the dynamics in the cochlear fluids while maintaining the integrity of the cochlear structure. This technique builds on the success of the state-of-the-art surgical robotic micro-drill. The micro-drill enables removal of bone tissue to prepare a consistent aperture onto the endosteal membrane within the cochlea. This is known as preparing a ‘Third window’. In this technique the motion of the exposed endosteal membrane is treated as the diaphragm element of a pressure transducer and is measured using a Micro- Scanning Laser Vibrometer operating through a microscope. There are two principal outcomes of the research: First, the approach has enabled disturbances in the cochlea to be contrasted for different surgical techniques, which it is expected to allude preferential methods in future surgery in otology. In particular it was shown that when using the robotic micro-drill to create a cochleostomy that the disturbance amplitude reduces to 1% of that experienced when using conventional drilling. Secondly, an empirically derived frequency map of the cochlea has been produced to understand how the location of implants affects maximum power transmission over the required frequency band. This has also shown the feasibility of exciting the cochlea at a third window in order to amplify cochlear response

Epidurals for liver transplantation – Where are we?

Thoracic epidural analgesia (TEA) has been used as a mode of postoperative pain relief for orthotopic liver transplants (OLT) in a selected group of patients. It is not widely practiced in view of the impaired haemostasis associated with end-stage liver disease and severe unpredictable intraoperative coagulopathy. TEA in OLT may not be the technique of choice for routine administration of postoperative analgesia, but can be considered in patients who have a normal coagulation profile preoperatively. Safe conduct of TEA in OLT involves anaesthetic expertise and stringent monitoring in the postoperative period. This review discusses the status of thoracic epidural analgesia in patients undergoing an orthotopic liver transplant

Intraoperative cardiovascular monitoring in hypertensive patients

Bacground and Purpose: Hypertensive patients are more prone to perioperative ischaemia, arrythmias and cardiovascular instability. Attention should be paid to the presence of target organ damage, such as coronary artery disease. Material and Method: Haemodynamically unstable patients undergoing major surgery require more complex haemodynamic monitoring. Multiple studies have demonstrated the favourable outcome achieved by goal-directed fluid management during the intraoperative period. Conclusion: The trend in intraoperative haemodynamic monitoring, a key feature of anaesthetic practice is towards less invasive systems that provide continuous information. A balance is needed between the hazards of an invasive approach and the desire for a continuous stream of accurate information that is robust enough to withstand the surgical and physiological challenges in hypertensive patients. In spite of its importance for anaesthetists, there is no consensus as to which system is best. This review examines the recent developments in haemodynamic monitoring

Feasibility study of a hand guided robotic drill for cochleostomy

The concept of a hand guided robotic drill has been inspired by an automated, arm supported robotic drill recently applied in clinical practice to produce cochleostomies without penetrating the endosteum ready for inserting cochlear electrodes. The smart tactile sensing scheme within the drill enables precise control of the state of interaction between tissues and tools in real-time. This paper reports development studies of the hand guided robotic drill where the same consistent outcomes, augmentation of surgeon control and skill, and similar reduction of induced disturbances on the hearing organ are achieved. The device operates with differing presentation of tissues resulting from variation in anatomy and demonstrates the ability to control or avoid penetration of tissue layers as required and to respond to intended rather than involuntary motion of the surgeon operator. The advantage of hand guided over an arm supported system is that it offers flexibility in adjusting the drilling trajectory. This can be important to initiate cutting on a hard convex tissue surface without slipping and then to proceed on the desired trajectory after cutting has commenced. The results for trials on phantoms show that drill unit compliance is an important factor in the design

Application of Multi-Objective Evolutionary Optimization Algorithms to Reactive Power Planning Problem

This paper presents a new approach to treat reactive power (VAr) planning problem using multi-objective evolutionary algorithms. Specifically, Strength Pareto Evolutionary Algorithm (SPEA) and Multi-Objective Particle Swarm Optimization (MOPSO) approaches have been developed and successfully applied. The overall problem is formulated as a nonlinear constrained multi-objective optimization problem. Minimizing the total incurred cost and maximizing the amount of Available Transfer Capability (ATC) are defined as the main objective functions. The proposed approaches have been successfully tested on IEEE 14 bus system. As a result a wide set of optimal solutions known as Pareto set is obtained and encouraging results show the superiority of the proposed approaches and confirm their potential to solve such a large scale multi-objective optimization problem

Large volume dye spread in transversus abdominis plane block via three injection sites: a cadaveric study

Background: Transversus abdominis plane (TAP) block is a recently described regional anaesthesia technique that provides analgesia for the abdominal wall. Three access points for injection have been described: via the lumbar triangle of Petit (LTOP), via the midaxillary line and via the subcostal region (SC). This study aimed to investigate the spread of dye following injection via all 3 sites with a large volume injectate. Materials and Methods: 24 hemiabdomens were injected with 40 mL 25% black food dye: 8 via the LTOP) 4 via the MAL, 4 via the SC. Dissection was performed to reveal the extent of nerve involvement and dye spread. Results: Variation in the size and shape of the LTOP was found between cadavers. Mean areas of dye spread (range of nerve involvement) in the remaining 16 hemiabdomens for LTOP, MAL and SC were 77.9 cm2 (T10-ilioinguinal), 50.3 cm2 (T10-ilioinguinal) and 91.3 cm2 (T7-ilioinguinal) respectively. Communications were seen between nerves within the TAP in one dissection. Dye staining was seen to involve nerves outside the TAP. Conclusion: Subcostal injection gives more superior dye spread, with a greater area and awider range of nerve involvement. This should perhaps be the preferred injection site, and could have broader indications

An Adaptive Load Frequency Control Based on Least Square Method

Modern power system becomes a complex system consisted with various load and power stations. Therefore, it may spread into some areas of power system in neighborhood, and so a load frequency control (LFC) is a necessity device to regulate the frequency of the power system by distributing the load to the generating units and controlling tie-line power interchange between areas. The integration of renewable energy sources (RES) into a power grid has presented important issues about stability and security of power system. In such conditions, the use of conventional LFC may not be sufficient to protect the power system against the power changes. In this chapter, an adaptive LFC controller is proposed using the least square method (LSM). The controller adopts an internal model control (IMC) structure in two scenarios, i.e., static controller gain with adaptive internal model and both the adaptive controller gain and adaptive internal model. A two-area power system is used to test and to validate both performance and the effectiveness of this controller through some case studies

An Investigation on the Nonlinear Vibration Behavior of Mistuned Bladed Disk Assemblies

One of the critical components of turbomachinery is the bladed disk assembly (BDA). BDAs operate in a harsh environment and under dynamic pressure during operation. In aero engines, the pressure inhomogeneities in airflow and friction forces due to contact at different locations can cause vibrations of the blades and disk. These vibrations result in a range of damages to the machine, from damage to the blade and casing, such as wear, to catastrophic engine failure. The following two factors may have a critical influence on the vibrations of BDAs: (i) the contact between the blade root and disk, (ii) the unavoidable imperfections in manufacturing or mounting of the blades, referred to as mistuning. The former leads to friction forces between the blade root and disk, while the latter adds a significant amount of uncertainty to the system and may lead to the localization of vibration energy to a few blades. The friction forces at the joints and other contact areas introduce nonlinear terms into the governing equations. The analysis of nonlinear vibrations of BDAs is a time-consuming process. Many studies have focused on the separate effects of nonlinearity and mistuning on the vibration characteristics of BDA in turbomachinery. The combined effects of these two phenomena, however, are not well understood. This area has attracted great interest in recent years, and engineers are working to uncover the correlation between mistuning and nonlinearity and their effects on the vibration characteristics of BDAs. This study is concerned with the mathematical modeling, numerical analysis, and statistical analysis of vibration characteristics of BDAs, including both nonlinear forces and mistuning. The governing equations are written for a lumped parameter model replicating the behavior of BDA with six blades. The nonlinear forces are due to the dry friction between the roots of the blades and the disk. The nonlinear governing equations are then solved for the tuned BDA. The steady-state forced response of the mistuned nonlinear system is then computed, with mistuning introduced as a small blade-to-blade deviation in the elasticity of the blades with respect to the tuned BDA. The effects of changing the mistuning and excitation levels are investigated. Two different mistuning realizations are considered to study the effect of mistuning on the vibrations of a BDA. A preliminary statistical analysis is then performed on an ensemble of 150 realizations of mistuned BDAs

A liquid metal encapsulation for analyzing porous nanomaterials by atom probe tomography

Analyzing porous (nano)materials by the atom probe tomography has been notoriously difficult. The electrostatic pressure intensifies stress at voids which results in premature failure of the specimen, and the electrostatic field distribution near voids lead to aberrations that are difficult to predict. Here we propose a new encapsulating method for a porous sample using a low-melting-point Bi-In-Sn alloy, known as Fields metal. As a model porous sample, we used single-crystalline wustite following direct hydrogen-reduced into iron. The complete encapsulation is performed using in-situ heating on the stage of the scanning-electron microscope up to approx. 70 Celsius. No visible corrosion nor dissolution of the sample occurred. Subsequently specimens are shaped by focused ion beam milling under cryogenic conditions at -190 Celsius. The proposed approach is versatile, can be applied to provide good quality atom probe datasets from microporous materials