Bioimpedance measurements are useful for determining a variety of biological conditions. By accounting for small impedance variations due to the arterial pulse, the effect of the blood can be studied more closely. The quasi-circulator system presented enables monitoring of pulsatile impedance changes with input frequencies above 1 MHz. The adjustable Rmatch allows for dynamic tuning of the system to increase sensitivity. By tuning Rmatch to be near the match point, the pulsatile signal in the output magnitude can be amplified, and tuning Rmatch to be at the match point causes the pulsatile signal in the output phase to be amplified. The system is tested on discrete circuit elements as well as human subjects, and results are analyzed. Pulsatile variations in the output voltage signal of up to 7 mV and 2.3° are demonstrated on human subjects. Tuning Rmatch allows for the pulsatile signal to be increased by more than 4 times.

The estimation of body fluids is a useful and common practice in the status assessment of diseasemechanisms and treatments. Electrical bioimpedance spectroscopy (EBIS) methods are non-invasive,inexpensive, and efficient alternatives for the estimation of body fluids. However, these methods areindirect, and their robustness and validity are unclear.Regarding the recording of measurements, a controversy developed regarding a spectrum deviationin the impedance plane, which is caused by capacitive leakage. This deviation is frequentlycompensated for by the extended Cole model, which lacks a theoretical basis; however, there is nomethod published to estimate the parameters. In this thesis, a simplified model to correct thedeviation was proposed and tested. The model consists of an equivalent capacitance in parallel withthe load.Subsequently, two other measurement artefacts were considered. Both artefacts were frequentlydisregarded with regard to total body and segmental EBIS measurements as their influence isinsignificant with suitable skin-electrode contact. However, this case is not always valid, particularlyfrom a textile-enabled measurement system perspective. In the estimation of body fluids, EBIS dataare fitted to a model to obtain resistances at low and high frequencies. These resistances can berelated to body fluid volumes. In order to minimise the influence of all three artefacts on theestimation of body fluids and improve the robustness and suitability of the model fitting the differentdomains of immittance were used and tested. The conductance in a reduced frequency spectrum wasproposed as the most robust domain against the artefacts considered.The robustness and accuracy of the method did not increase, even though resistances at low and highfrequencies can be robustly estimated against measurement artefacts. Thus, there is likely error in therelation between the resistances and volumes. Based on a theoretical analysis, state of the artmethods were reviewed and their limitations were identified. New methods were also proposed. Allmethods were tested using a clinical database of patients involved in growth hormone replacementtherapy. The results indicated EBIS are accurate methods to estimate body fluids, however they haverobustness limits. It is hypothesized that those limits in extra-cellular fluid are primarily due toanisotropy, in total body fluid they are primarily due to the uncertainty ρi, and errors in intra-cellularfluid are primarily due to the addition of errors in extracellular and total body fluid. Currently, theseerrors cannot be prevented or minimised. Thus, the limitations for robustness must be predicted priorto applying EBIS to estimate body fluids. / <p>QC 20130917</p>

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 application of textile electrodes has been widely studied for biopotential recordings,especially for monitoring cardiac activity. Commercially available applications, such as theAdistar T-shirt and the Numetrex Cardioshirt, have shown good performance for heart ratemonitoring and are available worldwide.Textile technology can also be used for electrical bioimpedance (EBI) spectroscopymeasurements in home and personalized health monitoring applications, however solid basicresearch about the measurement performance of the electrodes must be performed prior to thedevelopment of any textile-enabled EBI application.This research work studies the performance of EBI spectroscopy measurements whenperformed with textile electrodes. An analysis using an electrical circuit equivalent model andexperimental data obtained with the Impedimed spectrometer SFB7 was carried out. Theexperimental study focused on EBI spectroscopy measurements obtained with different types oftextile electrodes and in different measurement scenarios. The equivalent model analysis focusedon the influence of the electrode polarization impedance Zep on the EBI spectroscopymeasurements in the frequency range of 3 kHz to 500 kHz.The analysis of the obtained complex EBI spectra shows that the measurements obtainedwith textile electrodes produce constant and reliable EBI spectra. The results also indicate theimportance of the skin-electrode interface in EBI spectroscopy measurement.Textile technology, if successfully integrated, may enable the performance of EBIspectroscopy measurements in new scenarios, which would allow the generation of novel,wearable, or textile-enabled applications for home and personal health monitoring / <p>Thesis Supervisors: Kaj Lindecrantz and Fernando Seoane</p><p><b>Sponsorship</b>:</p><p>Mexican CONACYT</p>

Electrical and Computer Engineering / A high performance, wireless bio-impedance measurement system has been designed for the purpose of monitoring essential electrical properties of the heart during cardiac ablation. The system is broken into three parts: a spring-loaded device to house a tetrapolar surface probe and sensors, a wireless bio-impedance measurement system, and a desktop base station for graphical data display and acquisition. The system is specifically designed for a tetrapolar-electrode configuration where the two outer electrodes served as a current source operating at 20 kHz with an amplitude of 100 µArms and the two inner electrodes served as voltage sensing electrodes. In addition, the system also has a dedicated channel for current sense. The system is designed to be modular and reconfigurable for different measurement needs. Epochs of both discrete voltage and current samples generated by the voltage-controlled current source are processed using a digital signal processing algorithms to generate admittance measurements. In addition to the admittance’s magnitude and phase, pressure, electrocardiogram (EKG), and temperature (two channels) data are also acquired. The measurements are then wirelessly transmitted from the bio-impedance measurement system to a base station where data are processed and viewed graphically. The final system updates the admittance, pressure, EKG, and two temperature channels at 320 Hz, consumes less than 3 W, and has percent of measurement errors of 7 % and 2 % for capacitive and resistive measurements in the range of 100 pF to 10000 pF and 300 Ω to 1600 Ω, respectively. Instrument design, calibration, verification, and modeling are at the heart of this thesis. In the future, the instrument will be deployed for various bio-impedance measurements that require a high degree of linearity, precision, and a wide input range. / text

Electrical bioimpedance was used to detect local volume and aggregation changes in blood. This was done with two separate experimentation processes to improve upon current research methods. Abdominal internal hemorrhaging is bleeding and pooling of blood within the abdominal cavity which can put the welfare of the patient at risk and may cause organ failure. Electrical bioimpedance is the response of biological tissue to applied electrical current. In cooperation with Bioparhom, electrical bioimpedance was used as a detection device for abdominal internal hemorrhaging. It is hypothesized that electrical bioimpedance could be a non-invasive and cost effective avenue for the detection of internal bleeding. In this study we investigate the use of electrical bioimpedance with a custom 8x8 needle electrode array, for detecting and locating the blood pooling due to a drop in resistivity in a rat using a Z-Metrix (function generator by Bioparhom). 5 and 95 kHz signals were inputted into a dead rat experiencing internal bleeding of porcine blood at a rate of 3.33 ml/min to 10 ml. For 8 rats, the 5 kHz frequency was found to be more sensitive to internal blood pooling. Red blood cell aggregation is a physiological process where red blood cells form reversible aggregates. RBC aggregation is an important indicator for physicians for the health of the circulatory system. Utilizing electrical bioimpedance, it is hypothesized that a reactance change as a result of blood aggregation will be detected. As well, a method is developed using impedance spectroscopy to determine s frequency which exhibits the highest reactance change during blood aggregation. This sensitive frequency, found to be 304 kHz, is compared to a frequency used by previous studies (100 kHz) to validate its. Using the Z-Metrix (function generator by Bioparhom) with a custom 4 electrode configuration, 2 ml of porcine blood mixed with 2 mg/ml of EDTA is tested for 2 minutes at a single frequency. The 304 kHz is found to be the most sensitive of the frequencies tested to reactance changes during aggregation. Results found for blood samples give an average AIc of 27.32 ± 11.44, which is within the physiological range for porcine blood of 3-30. It is seen that the 304 kHz has a higher precision than the 100 kHz frequency, but the AIc is within the same magnitude. As a result, 304 kHz is found to be a more favorable frequency than the previously published 100 kHz for the trials performed based on precision of the results and the sensitivity of the reactance change to blood aggregation.

The objective of this work is to offer a new method of evaluation using the corporal and thoracic bioimpedance of pre-term neonate with Respiratory Discomfort Syndrome, submitted or not to the invasive mechanical ventilation. Thirty pre-term neonates with Respiratory Discomfort Syndrome were evaluated. They were admitted interned in the newborn intensive therapy unit of Hospital Universitário Evangélico de Curitiba (HUEC) from August to November of 2004. The percentage average of the gestational age in both groups was 32 weeks and the weight was 1250g. The newborn were divided into two groups, group A (15 newborns), with Respiratory Discomfort Syndrome of medium to moderate clinical repercussion, needing the invasive ventilator support. Group B (15 newborn) with light level of Respiratory Discomfort, without the need of ventilator support. The newborn of both groups were evaluated according to the Silverman-Andersen report. Which average in group A was 7 and in group B was 3. Five time speed measurement of subjects of group A were analyzed in the statistical analyses, and they were compared to an unique observation of group B. On the first measurement made in group A, it was noticed a low resistance both corporal (410) and thoracic (32,53) relative to group B. where the percentage average was 595 in the corporal resistance and 46,13 in the thoracic one. In the capacitive reactance it was noticed in the first analyses an inversely proportional behavior, and an increasing in the capacitive reactance for both corporal and thoracic in group A related to group B. As long as the newborns in group A improved clinically, a tendency in increasing the resistance values both corporal and thoracic was observed, correlating with the ventilator support removal. The opposite occurred in the capacitive reactance, both corporal and thoracic. So, the evaluation through the corporal bioimpedance in this work got statistically significant results, and it can be used as a method of evaluation improving the clinical diagnosis of the patient. / O objetivo deste trabalho é propor um novo método de avaliação através da bioimpedância corporal e torácica em recém-nascidos pré-termo com Síndrome do Desconforto Respiratório, submetidos ou não á ventilação mecânica invasiva. Foram avaliados trinta neonatos pré-termos com Síndrome do Desconforto Respiratório, internados na unidade de Terapia Intensiva Neonatal (UTIN) do Hospital Universitário Evangélico de Curitiba (HUEC), no período de agosto à novembro de 2004. A média da idade gestacional de ambos os grupos foi de 32 semanas e o peso de 1250g. Os recém-nascidos (RN) foram divididos em dois grupos, grupo A (15 neonatos), Síndrome do Desconforto Respiratório de média a moderada repercussão clínica, necessitando de suporte ventilatório invasivo. Grupo B (15 neonatos) Grau leve de Desconforto Respiratório, sem necessidade de suporte ventilatório. Os neonatos dos dois grupos foram avaliados conforme o boletim de Silverman-Andersen, a média percentual no grupo A foi de 77 e no grupo B de 3. Na análise estatística foram analisados cinco momentos do grupo A e comparado esses momentos com uma única observação do grupo B. Nos primeira mensuração realizada no grupo A, observa-se uma resistência tanto corporal (410 Ω) e torácica (32,53 Ω), baixa em relação a obtida no grupo B, onde a média percentual foi de 596 Ω, na resistência corporal e na torácica de 46,13 Ω. Na reatância capacitiva observa-se na primeira análise um comportamento inversamente proporcional, ocorrendo um aumento na reatância capacitiva tanto corporal como torácica no grupo A em relação ao grupo B. A medida que o neonato do grupo A, melhora clinicamente observa-se uma tendência ao aumento de valores de resistência tanto corporal com a torácica, correlacionada com a retirada da prótese ventilatório. Ocorrendo o inverso com a reatância capacitiva tanto corporal como torácica. Portanto, a avaliação através da bioimpedância corporal neste trabalho obteve resultados estatisticamente significativos podendo ser utilizada como um método de avaliação, enriquecendo o diagnóstico clínico do paciente.

Electrical bioimpedance was used to detect local volume and aggregation changes in blood. This was done with two separate experimentation processes to improve upon current research methods. Abdominal internal hemorrhaging is bleeding and pooling of blood within the abdominal cavity which can put the welfare of the patient at risk and may cause organ failure. Electrical bioimpedance is the response of biological tissue to applied electrical current. In cooperation with Bioparhom, electrical bioimpedance was used as a detection device for abdominal internal hemorrhaging. It is hypothesized that electrical bioimpedance could be a non-invasive and cost effective avenue for the detection of internal bleeding. In this study we investigate the use of electrical bioimpedance with a custom 8x8 needle electrode array, for detecting and locating the blood pooling due to a drop in resistivity in a rat using a Z-Metrix (function generator by Bioparhom). 5 and 95 kHz signals were inputted into a dead rat experiencing internal bleeding of porcine blood at a rate of 3.33 ml/min to 10 ml. For 8 rats, the 5 kHz frequency was found to be more sensitive to internal blood pooling. Red blood cell aggregation is a physiological process where red blood cells form reversible aggregates. RBC aggregation is an important indicator for physicians for the health of the circulatory system. Utilizing electrical bioimpedance, it is hypothesized that a reactance change as a result of blood aggregation will be detected. As well, a method is developed using impedance spectroscopy to determine s frequency which exhibits the highest reactance change during blood aggregation. This sensitive frequency, found to be 304 kHz, is compared to a frequency used by previous studies (100 kHz) to validate its. Using the Z-Metrix (function generator by Bioparhom) with a custom 4 electrode configuration, 2 ml of porcine blood mixed with 2 mg/ml of EDTA is tested for 2 minutes at a single frequency. The 304 kHz is found to be the most sensitive of the frequencies tested to reactance changes during aggregation. Results found for blood samples give an average AIc of 27.32 ± 11.44, which is within the physiological range for porcine blood of 3-30. It is seen that the 304 kHz has a higher precision than the 100 kHz frequency, but the AIc is within the same magnitude. As a result, 304 kHz is found to be a more favorable frequency than the previously published 100 kHz for the trials performed based on precision of the results and the sensitivity of the reactance change to blood aggregation.