This thesis presents designs of portable medical instruments to diagnose human tinnitus. At the present time, portable medical instruments are used everywhere for almost all kinds of daily health needs. Those high-performance instruments are used in medical facilities, hospitals, and clinics, and on the personal use level, as patients need them. Nowadays the digital means to design those instruments have become very important, and it's our goal to make use of the technology to upgrade and make those designs fast, accurate, easy to use, and inexpensive, so all people with need of those devices will be able to obtain them. At this time, there are many questions regarding tinnitus, but few definitive answers. Since it is still not fully understood, many comprehensive studies and analysis were carried out to present a complete model for the instruments.

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<p>  </p> <p>Persons with a spinal cord injury (SCI) above the sixth thoracic vertebrae commonly experience autonomic dysreflexia (AD), 90 percent of individuals with this level of injury are susceptible to AD which is associated with an increase in sympathetic nerve activity. Left untreated AD causes a paroxysmal rise in blood pressure that may result in seizures, heart attack, or even death. This project investigates how AD affects QT interval, RR interval, P wave height, heart rate, and QRS width both during an event and long term to help identify potential cardiac risks for individuals with SCI who experience chronic AD. Sympathetic tone has been shown to influence QT interval changes that can be indicative of an increased risk of arrhythmia, which can be exacerbated by recurring episodes of AD.</p> <p>A rat spinal cord injury model at the T3 level undergoing colorectal distention (CRD) was used to induce AD. Electrophysiological recordings from an implanted ECG sensor and noninvasive skin nerve activity (SKNA) sensor array during normal baseline and three trials of CRD were collected on days 5, 7, 9, 11, 14, 16, 19, and 21 post-SCI. Custom MATLAB algorithms were used to identify the QRS complex and T-peaks from the implant ECG signal. QT interval measurements were taken for 2 minutes of baseline and for 2 minutes after the initiation of each CRD trial. Corrected QT interval (QTc) was calculated using normalized Bazett’s formula to account for the impact of heart rate on QT interval. </p> <p>It was found that the rats’ susceptibility and reaction to AD events varied between subacute (5-14 days) and chronic phases of SCI. During the chronic phase the incidence of AD events increased during regular occurrences of CRD as indicated by above-threshold (≥15 mmHg) blood pressure spikes. AD events also resulted in increased QT interval short term variability marking an increased risk of arrythmias. Baseline P-wave height and QTc interval were also increased while QRS complex width decreased resulting in potentially detrimental cardiac effects. This rat model showed that humans who experience recurrent AD during the chronic phase of SCI may be at increased risk for arrythmia. </p>

Neurologically related injuries cause a similar number of deaths ascancer, and brain damage is the second commonest cause of death in theworld and probably the leading cause of permanent disability. Thedevastating effects of most cases of brain damage could be avoided if itwere detected and medical treatment initiated in time. The passiveelectrical properties of biological tissue have been investigated for almost acentury and electrical bioimpedance studies in neurology have beenperformed for more than 50 years. Even considering the extensive effortsdedicated to investigating potential applications of electrical bioimpedancefor brain monitoring, especially in the last 20 years, and the specificallyacute need for such non-invasive and efficient diagnosis support tools,Electrical Bioimpedance technology has not made the expectedbreakthrough into clinical application yet. In order to reach this stage inthe age of evidence-based medicine, the first essential step is todemonstrate the biophysical basis of the method under study. The presentresearch work confirms that the cell swelling accompanying thehypoxic/ischemic injury mechanism modifies the electrical properties ofbrain tissue, and shows that by measuring the complex electricalbioimpedance it is possible to detect the changes resulting from braindamage. For the development of a successful monitoring method, after thevital biophysical validation it is critical to have available the properelectrical bioimpedance technology and to implement an efficient protocolof use. Electronic instrumentation is needed for broadband spectroscopymeasurements of complex electrical bioimpedance; the selection of theelectrode setup is crucial to obtain clinically relevant measurements, andthe proper biosignal analysis and processing is the core of the diagnosissupport system. This work has focused on all these aspects since they arefundamental for providing the solid medico-technological backgroundnecessary to enable the clinical usage of Electrical Bioimpedance forcerebral monitoring.

Esta dissertação trata do projeto e avaliação de um canal de medição de bioimpedâncias multifrequencial cujo objetivo é a medida em módulo e fase de impedâncias até 1 k com desempenho reportado nas freqüências 100 kHz, 300 kHz e 1 MHz. Um modelo teórico foi desenvolvido para cada etapa do canal de medição incluindo as não idealidades dos componentes utilizados na implementação prática. A análise da sensibilidade à variação de parâmetros e da propagação de incertezas nas etapas do sistema foi realizada juntamente com a avaliação experimental da exatidão e precisão do protótipo desenvolvido. O circuito proposto apresenta incerteza experimental 0,008% nas medidas de amplitude e 0,05% nas medidas de fase. / This dissertation deals with the project and evaluation of a multifrequency bioimpedance measurement channel whose objective is to obtain the measure in module and phase of load impedances up to 1 k with performance reported in 100 kHz, 300 kHz and 1 MHz. A theoretical model was developed for each stage of the measurement channel having included non-idealities of the components used in the practical implementation. The sensitivity analysis with respect to parameter variation and uncertainty analysis in the stages of the system was carried through together with the experimental evaluation of the accuracy and precision of the developed prototype. The considered circuit presents experimental uncertainty of 0.008% in the measures of amplitude and 0.05% in the measures of phase.

Esta dissertação trata do projeto e avaliação de um canal de medição de bioimpedâncias multifrequencial cujo objetivo é a medida em módulo e fase de impedâncias até 1 k com desempenho reportado nas freqüências 100 kHz, 300 kHz e 1 MHz. Um modelo teórico foi desenvolvido para cada etapa do canal de medição incluindo as não idealidades dos componentes utilizados na implementação prática. A análise da sensibilidade à variação de parâmetros e da propagação de incertezas nas etapas do sistema foi realizada juntamente com a avaliação experimental da exatidão e precisão do protótipo desenvolvido. O circuito proposto apresenta incerteza experimental 0,008% nas medidas de amplitude e 0,05% nas medidas de fase. / This dissertation deals with the project and evaluation of a multifrequency bioimpedance measurement channel whose objective is to obtain the measure in module and phase of load impedances up to 1 k with performance reported in 100 kHz, 300 kHz and 1 MHz. A theoretical model was developed for each stage of the measurement channel having included non-idealities of the components used in the practical implementation. The sensitivity analysis with respect to parameter variation and uncertainty analysis in the stages of the system was carried through together with the experimental evaluation of the accuracy and precision of the developed prototype. The considered circuit presents experimental uncertainty of 0.008% in the measures of amplitude and 0.05% in the measures of phase.

Esta dissertação trata do projeto e avaliação de um canal de medição de bioimpedâncias multifrequencial cujo objetivo é a medida em módulo e fase de impedâncias até 1 k com desempenho reportado nas freqüências 100 kHz, 300 kHz e 1 MHz. Um modelo teórico foi desenvolvido para cada etapa do canal de medição incluindo as não idealidades dos componentes utilizados na implementação prática. A análise da sensibilidade à variação de parâmetros e da propagação de incertezas nas etapas do sistema foi realizada juntamente com a avaliação experimental da exatidão e precisão do protótipo desenvolvido. O circuito proposto apresenta incerteza experimental 0,008% nas medidas de amplitude e 0,05% nas medidas de fase. / This dissertation deals with the project and evaluation of a multifrequency bioimpedance measurement channel whose objective is to obtain the measure in module and phase of load impedances up to 1 k with performance reported in 100 kHz, 300 kHz and 1 MHz. A theoretical model was developed for each stage of the measurement channel having included non-idealities of the components used in the practical implementation. The sensitivity analysis with respect to parameter variation and uncertainty analysis in the stages of the system was carried through together with the experimental evaluation of the accuracy and precision of the developed prototype. The considered circuit presents experimental uncertainty of 0.008% in the measures of amplitude and 0.05% in the measures of phase.

The neurophysiological pathways associated with beat-to-beat regulation of mean arterial pressure are well known. Less known are the control dynamics associated with short term maintained of arterial blood pressure about a homeostatic set point.The baroreflex (BRx), the most rapid and robust of neural reflexes within the autonomic nervous system, is a negative feedback controller that monitors and regulates heart rate and blood pressure. By leveraging the parasympathetic and sympathetic divisions of the autonomic nervous system, the BRx can change blood pressure within a single heart beat. To better understand these controller dynamics, a classic BRx reflexogenic experimental preparation was carried out. This thesis reconfirmed previous observations of an electrically-evoked sexually-dimorphic peak depressor response in the BRx of Sprague-Dawley rats and verified that these functional reflexogenic differences carry over to sustained electrical paradigms. Further, it uncovered interesting recovery dynamics in both blood pressure and heart rate. The rat aortic depressor nerve was used as an experimental target for electrical activation of the parasympathetic-mediated reduction in mean arterial pressure. The duration, frequency, and patterning of stimulation were explored, with emphasis on differences between sexes. By measuring the normalized percent decrease in mean arterial pressure as well as the differences in beats per minute during rest and during stimulation,the null hypothesis was rejected.<br>

<p>Glaucoma is the leading cause of irreversible blindness worldwide effecting more than 2.7 million people in the U.S alone. Treatments exist in the form of both pharmaceutical and surgical options, but often do not provide the desired efficacy. For example, the failure rate of a trabeculectomy procedure is 39% within 5 years. Additionally, none of the current glaucoma treatments allow for closed loop monitoring of pressure, therefore requiring more frequent doctor visits. Glaucoma management can be improved through the use of a closed loop application of electroceutical treatment. The goal is to develop an implantable device that will be inserted into the eye to monitor intraocular pressure (IOP) and provide responsive therapeutic stimulation to the eye. I designed a discrete pressure monitoring system that interacts with a bare die piezoresistive pressure sensor. The system is based on a Wheatstone bridge design which translates the input resistances of the pressure sensor into a voltage output. This system has an average accuracy of 0.53 mmHg and draws 295 µW of power. I then combined this pressure system with data processing code and Howland current pump stimulation circuitry. This simulation system can output up to 1.05 mA of current for electroceutical intraocular stimulation to lower IOP. Future work will involve miniaturizing the circuitries in the form of an ASIC and packaging the entire system into an ocular implant. This implant can wirelessly monitor IOP and provide therapeutic stimulation to lower IOP. A reliable, closed loop method of lowering IOP would greatly benefit the ever-growing population affected by glaucoma.</p>