Bioimpedance

Research shows that cellular and mitochondrial (ΔΨm) membrane potentials are strong indicators of cellular physiology. In this paper we review further research suggesting that microcurrent frequencies can positively influence both these membrane potentials. The goal of this research is to show how microcurrent might stimulate physiological potentials in order to support a healthy function of bioelectric fields of cells and organs. In the second part of the article, a study to examine the effects of microcurrent application on the body's response to electric measurements is presented, in particular to a change in voltage-current lag known as a phase angle. The test involved measuring bioimpedance of a person before and after a 30-minute application with microcurrent stimulation. Fifteen healthy subjects were examined through impedance measurements taken on one arm. The results showed a consistent increase in phase angle directly after the stimulation, confirming a widely accepted indication of health improvement on a cellular level. These results are encouraging and justify further investigations on the effect of microcurrent stimulation on the human body in relation to general cellular health and regenerative functions.

Assessment of volume status in critically ill patients poses a challenge to clinicians. Measuring changes in the inferior vena cava (IVC) diameter using ultrasound is becoming a standard tool to assess volume status. Ultrasound requires physicians with significant training and specialized expensive equipment. It would be of significant value to be able to obtain this measurement continuously without physician presence. We hypothesize that dynamic changes in limb's bio-impedance in response to respiration could be used to predict changes in IVC. Forty-six subjects were tested a hemodialy-sis session. Impedance was measured via electrodes placed on the arm. Simultaneously, the IVC diameter was assessed by ultrasound. Subjects were asked to breathe spontaneously and perform respiratory maneuvers using a respiratory training device. Impedance (dz) was determined and compared with change in IVC diameter (dIVC; r = 0.76, p < 0.0001). There was significant relationship between dz and dIVC (p < 0.0001). Receiver-operator curves for dz at thresholds of dIVC (20% to70%) demonstrated high predictive power with areas under the curves (0.87–0.99, p < 0.0001). This evaluation suggests that real-time dynamic changes in limb impedance are capable of tracking a wide range of dynamic dIVC. This technique might be a suitable surrogate for monitoring real-time changes in dIVC to assess intravascular volume status. Monitoring and assessment of a patient's volume status and fluid responsiveness is an integral part of the management plan of critically ill patients as well as others for whom volume management has significant outcome implications. Rapid and accurate volume determinations are important for preventing under or over resuscitation of critically ill and injured patients that can result in higher rates of secondary injury and mortality. These same considerations also extend to patients with chronic conditions such as heart failure and chronic kidney disease. 1–6 Development of noninvasive and easy to use tools to make these assessments would be a welcome addition to the management of these patients. The dynamic relationship between venous return, the function of the right ventricle, and its interaction with lung mechanics are key determinants of estimating intravascular volume status and more importantly, the patient's functional response to addition or removal of volume. 7,8 The use of real-time ultrasound to view the collapse or distention of the inferior vena cava (IVC) during respiration is a useful tool to estimate volume responsiveness and guide intravenous fluid management. 9–18 Inferior vena cava ultrasound requires physicians with significant training and specialized expensive equipment. Inferior vena cava measurements are difficult to obtain in obese patients and patients with significant amounts of bowel gas. Inferior vena cava measurements require a physician to be present at the bedside for each measurement making frequent measures to follow treatment logistically challenging. It would be of significant value to be able to obtain this measurement on a continuous basis without physician presence for each measurement. Bioimpedance—a measure of a tis-sue's resistance to an induced current or voltage 19,20 —has been used to monitor fluid status, nutritional status, and lung water. When applied to either the whole body or a portion thereof, bioimpedance becomes the cumulative effect of the individual impedances of components under examination. These components in the body consist of muscle tissue, fat, intracellular and extracellular fluid, and blood. Blood, as a good conductor of electricity, has a distinct effect on limb impedance as the respiratory cycles significantly shift blood volume in the limb. That is, the impedance of a limb increases with decreased blood volume in the limb—as occurs during spontaneous inspiration as blood return is increased to the thorax through the mechanism of enhanced intrathoracic negative pressure— and decreases with increased blood volume in the limb—as is the case during spontaneous expiration. These effects are exaggerated with respiratory maneuvers like deep inspiration. Furthermore, because venous compliance is up to 30 times greater than its arterial counterpart, 21,22 volume change occurring within a limb during respiration will largely be a function of venous blood return. Aim We tested a new noninvasive technique to assess volume status. Our approach was to utilize single-frequency

Bioimpedance spectroscopy (BIS) measurement methods have been evolving from the traditional frequency-sweep approach to the multi-frequency simultaneous measurement technique which can drastically reduce measuring time and will be increasingly attractive for time-varying biological applications. Multi-frequency mixed (MFM) signals with sparsely distributed spectra are desirable for broadband BIS measurement. This paper proposes a synthesis method to design a series of tri-level MFM signals which contain only three values (+1, 0, −1), and has majority energy distributed on its (2 n )th primary harmonics. Tri-level MFM signals have both high energy efficiency and a low crest factor. An impedance measurement experiment excited by an 8th-order tri-level MFM signal on a RC three-element equivalent model has been performed, and the results on 8 primary harmonic frequencies ranging from 8 to 1024 kHz show a high accuracy with the mean amplitude relative error of 0.41% and mean phase absolute error of 0.18°, which has validated the feasibility of the tri-level MFM signals for broadband BIS measurement.

W niniejszej pracy przedstawiono postępy oraz założenia projektowe w pracy nad scalonym skanerem bioimpedancji. Wyjaśnione zostały różne zagadnienia programowe oraz sprzętowe, takie jak sposób komunikacji głównego mikroprocesora z peryferiami czy automatyczna kalibracja układu pomiarowego. Głównym założeniem projektu jest to, aby budowana platforma była uniwersalna i posiadała możliwości rozbudowy. Daje to możliwości sprecyzowania wymagań sprzętowych dla urządzeń dedykowanych do konkretnych celów, które będzie można szybko wprowadzić na rynek, na którym będą konkurencyjne pod względem funkcji oraz ceny. Ważne jest, aby ze skonstruowanej płyty ewaluacyjnej mogły bez przeszkód korzystać osoby, które także działają w obszarze pomiarów BIA, lecz nie mające zaplecza elektronicznego lub informatycznego. Wymusza to stworzenie przejrzystego i prostego w obsłudze interfejsu użytkownika.

Electrical Impedance Spectroscopy (EIS) involves the injection of a constant current into tissue at different frequencies and measurement of the resultant voltages. The transfer impedance is then calculated, fitted to an appropriate model and parameters are extracted to describe the electrical properties of the tissue. This technique has been used for characterising oesophageal and cervical tissue. However, electrode/tissue interface impedance and tissue inhomogeneities limit the consistency of the technique. The objective of this research is to optimise the ability of a tetrapolar impedance probe to characterise tissue in terms of electrical impedance spectra.

Este trabalho objetiva apresentar os fundamentos científicos da bioimpedância, bem como suas aplicações nas diversas áreas da engenharia biomédica. Com um amplo espectro de aplicações, esta técnica de análise e diagnose é rápida e não invasiva, reduzindo assim o tempo de diagnóstico e sem efeitos colaterais. Com aplicações desde uma simples estimativa de massa corpórea em amostras de células em suspensão a estimativa de composição corporal ou a caracterização de estados patológicos de tecidos. Como equipamento básico para a técnica, o projeto de medidor de bioimpedâncias proposto neste trabalho opera a quatro eletrodos, ou tetrapolar, em uma frequência de 50kHz, permite a medição da resistência (R), da reatância capacitiva (Xc) que são adequados para aplicações de estimativa da composição corporal e a medição do ângulo de fase (AF), o qual é base para o diagnóstico preditivo de doenças como câncer e tumores.

Bioimpedance spectroscopy (BIS) is becoming a powerful diagnostic tool for a wide variety of medical applications, and the multi-frequency simultaneous (MFS) measurement of BIS can greatly reduce measurement time and record the transient physiological status of a living body compared with traditional frequency-sweep measurement technology. This paper adopts the Van der Ouderaa's multisine, which has 31 equidistant and flat amplitude spectra and a low crest factor of 1.405 as the broadband excitation, and realizes the MFS measurement of BIS by means of spectral analysis using the fast Fourier transform algorithm. The approach to implement the multisine based on a field-programmable gate array and a digital to analog converter is described in detail, and impedance measurement experiments are performed on three resistance-capitance three-element phantoms. Experimental results show a commendable accuracy with a mean relative error of 0.55% for the impedance amplitudes, and a mean absolute error of 0.20° for the impedance phases on the 31 frequencies ranging linearly from 32 to 992 kHz. This paper validates the feasibility of the MFS technology for BIS measurement based on the multisine excitation.

Due to its biological structure and electrical properties, living tissue can be
characterized by the Bioelectrical Impedance (BI). Bioimpedance measurements are used
in medicine for diagnostic purposes, including the so-called Bioelectrical Impedance
Analysis (BIA), which is a noninvasive method of body composition analysis [1-3]. This
method is increasingly popular also in sports medicine, aesthetics medicine and dietetics.
Several manufacturers offer specialized electronic equipment for professional body
composition measurements based on bioimpedance analysis [3]. However, the use of
such popular, cheap systems is rather restricted to the dedicated area, and – as a result –
in more universal studies one has to adapt the equipment to the particular purpose, which
could be difficult, or to purchase much more sophisticated system at much higher price.

The accumulation of fat in the abdominal area (visceral) is a strong risk factor for cardiovascular disease. One of the problems observed in women submitted to mastectomy is an increase in body weight and, consequently, an increase in abdominal fat as these two variables are closely linked, however no references about this correlation were found in the literature. Aim: The aim of this study was to evaluate and measure the incidence of abdominal fat (AF) in women submitted to mastectomy. Method: Forty-five female patients diagnosed with arm lymphedema in 2011 were enrolled. The measurement of abdominal fat (AF) was by bioimpedance (InBody S 10®) the results of which were correlated with the body mass index (BMI). The paired t-test and Fisher exact test were used for statistical analysis with an alpha error of 5% being considered acceptable. Results: An association was identified between body mass index and abdominal fat (p-value < 0.03). Conclusion: The authors suggest that an assessment of intra-abdominal fat should be included in preventive evaluations of patients with lymphedema after breast cancer treatment.

Bioimpedance measurements are used increasingly in health applications because bioelectric parameters have been associated with anatomical and physiological properties, thus enabling to distinguish medical conditions. For bone fracture diagnostics, nevertheless, there is no established non-invasive method. Ex vivo studies and In vivo bioimpedance procedures, both invasive and non-invasive, on mammalians long bones are associated with promising results. In this work, out of a total of 568 papers, we reviewd 59 articles that mention long bone integrity by electric properties, be it Bioimpedance Analysis, Electrical Impedance Spectroscopy or Electrical Impedance Tomography. The papers are described in three sections, &ldquo;Ex vivo measurements&rdquo;, &ldquo;In vivo invasive measurements&rdquo; and &ldquo;In vivo non-invasive measurements&rdquo;. This review allows to establish the basics to planning the development of new technology to detect bone fracture via bioimpedance measurements.

Bioimpedance spectroscopy (BIS) has become an important clinical indicator for monitoring the pathological status of biological tissues, and multifrequency simultaneous measurement of BIS may provide more accurate diagnostic information compared with the traditional frequency-sweep measurement technology. This paper proposes a BIS multifrequency simultaneous measurement method based on multifrequency mixed (MFM) signal excitation and a Nuttall windowed interpolation FFT algorithm. Firstly, the excitation source adopts the nine-frequency MFM signal í µí±“(9, í µí±¡), which has excellent spectral characteristic and is very suitable for BIS measurement. On this basis, a Nuttall window is adopted to truncate sample data, and an interpolation FFT algorithm based on Nuttall window is built to perform spectral analysis, in which the parameter correction formula is provided based on polynomial approximation. A BIS measurement simulation experiment is performed on an RC three-element equivalent circuit, and results on the 9 primary harmonic frequencies ranging from 3.9 kHz to 1 MHz show a high accuracy with the impedance amplitude relative error |í µí°¸í µí± § | < 0.3%, and the phase absolute error |í µí°¸í µí± | < 0.1 ∘. This paper validates the feasibility of BIS multifrequency simultaneous measurement method and establishes an algorithm foundation for the development of practical broadband BIS measurement system.

Background It is important for highly active individuals to accurately assess their hydration level. Bioelectrical impedance (BIA) can potentially meet these needs but its validity in active individuals is not well established. Methods We compared whole-body bioimpedance measurements obtained from multi-frequency bioelectrical impedance spectroscopy (BIS, Xitron 4200) at a 50 kHz frequency with those determined by a phase-sensitive single-frequency device (SF-BIA, BIA-101, RJL/Akern Systems) in two populations: active adults and elite athletes. Results One hundred twenty-six participants, including active males involved in recreational sports (N = 25, 20-39 yr) and elite athletes (females: N = 26, 18-35 yr; males: N = 75, 18-38 yr) participated in this study. Reactance (Xc), Resistance (R), Impedance (Z), and phase angle (PhA) were obtained by BIS and SF-BIA. Small but significant differences (R: −9.91 ± 15.09 Ω; Xc: −0.97 ± 2.56 Ω; Z: −9.96 ± 15.18 Ω; PhA: 0.12 ± 0.2°) were observed between the bioimpedance equipment in all measured variables (p < 0.05) though differences were within the devices' technical error of measurements. Device-specific values were highly (p < 0.0001) correlated [R 2 ranged from 0.881 (Xc) to 0.833 (R)], but slopes and intercepts were different (p < 0.0001) from 1 and 0, respectively. Relatively large limits of agreement were observed for R (−40 to 21 Ω), Xc (−6 to 4 Ω), PhA (−0.4 to 0.5°), and impedance (−40 to 20 Ω). Conclusion: Bioimpedance measurements from the current single-and multi-frequency devices should not be used interchangeably. The of lack of agreement between devices was observed in determining individual values of R, Xc, Z and PhA of highly active populations possibly due to methodological and biological factors.

Multi-frequency-one-time (MFOT) measurement of bioimpedance spectroscopy (BIS) can greatly reduce measurement time and grasp the transient physiological status of a living body compared with the traditional one-frequency-one-time (OFOT) measurement technology, and a wideband excitation source mixed with multiple frequencies is a crucial part of MFOT measurement of BIS. This communication describes a design of a wideband excitation source. Firstly, a multi-frequency mixed (MFM) signal containing seven primary harmonics is synthesized based on Walsh functions, which is a periodical and rectangular signal and whose 68.9% of the energy is homogeneously distributed on its seven 2 n th primary harmonics. Then the MFM signal is generated by a field programmable gate array (FPGA), and a unipolar-to-bipolar convertor (UBC) is designed to convert the unipolar signal into bipolar signal. Finally, the bipolar MFM signal is driven by a voltage-controlled current source (VCCS). A 2R-1C series model is adopted as the load of the VCCS, and the simulated voltage response on the load is obtained based on the theoretical analysis. Experiments show that the practical waveform on the load matches well with the theoretical analysis, which indicates that the VCCS has a good performance on the MFM signal. The design of the wideband excitation source establishes a good foundation for fast measurement of BIS.

Background: Chronic subclinical volume overload happens very frequently in hemodialysis patients and is associated directly with hypertension, increased arterial stiffness, left ventricular hypertrophy, and ultimately higher mortality. Study Design: Randomized controlled parallel-group trial. Setting & Participants: 131 patients from one hemodialysis center, randomly assigned into 2 groups. Intervention: Dry weight prescription using results derived from repeated 3-month bioimpedance measurements to guide ultrafiltration for strict volume control (bioimpedance group; n 5 62) compared with clinical judgment without bioimpedance measures (clinical-methods group; n 5 69) for 2.5 years. Outcomes: The primary outcome was all-cause mortality over 2.5 years (the duration of the intervention). Secondary outcomes were change in relative arterial stiffness, fluid overload, and blood pressure (BP) over 2.5 years. Measurements: Bioimpedance measurements were performed using a Body Composition Monitor device. Pulse wave velocity analysis was performed at baseline, 2.5 years (end of intervention), and 3.5 years (end of study). Relative fluid overload and BP were assessed at 3-month intervals. Results: The unadjusted HR for all-cause death in the bioimpedance group (vs the clinical-methods group) was 0.100 (95% CI, 0.013-0.805; P 5 0.03). After 2.5 years, we found a greater decline in arterial stiffness, relative fluid overload, and systolic BP in the bioimpedance group than the clinical-methods group. Between-group differences in change from baseline to the end of intervention were 22.78 (95% CI, 23.75 to 1.80) m/s for pulse wave velocity (P , 0.001), 22.99% (95% CI, 25.00% to 20.89%) for relative fluid overload (P 5 0.05), and 22.43 (95% CI, 27.70 to 2.84) mm Hg for systolic BP (P 5 0.4). Limitations: Echocardiography was not performed as cardiovascular assessment and the caregivers were not masked to the intervention. Conclusions: Our study showed improvement in both surrogate and hard end points after strict volume control using bioimpedance to guide dry weight adjustment. These findings need to be confirmed in a larger trial. Am J Kidney Dis.-(-):-. ª 2014 by the National Kidney Foundation, Inc.

Multisine signal with a low crest factor (CF) can bring a high signal-to-noise ratio for fast frequency response function (FRF) estimation. Synthesis of a low CF multisine with the given amplitude spectrum depends on optimum selection of the initial phases of its cosinusoidal components. The solutions investigated can be generally divided into two branches: (1) the analytical method based on direct formula calculation; and (2) the numerical method based on iterative computations. The analytical method works well only for an equidistant and flat amplitude spectrum, while the numerical method can generally output better results, even for a sparse or non-flat spectrum, but the number of iterations might be huge. This paper presents an improved CF minimization algorithm to synthesize multisine signals based on the combination of the previous Schroeder analytical method and the Van der Ouderaa (VDO) iteration procedure. The improved algorithm adopts the Schroder phases as the iterative initial phases, and employs a logarithmic clip function of the iterative index i in the VDO iteration procedure. Comprehensive experiments of multisine synthesis on three types of cosinusoidal amplitude spectra are performed, and the resulting CFs remain the lowest level in all cases compared with the earlier methods. The proposed algorithm provides a fast and efficient solution to synthesize multisine with the lowest CF for an arbitrary user-prescribed spectrum.

Bioimpedance measurements are used increasingly in health applications because bioelectric parameters have been associated with anatomical and physiological properties, thus enabling to distinguish medical conditions. For bone fracture diagnostics, nevertheless, there is no established non-invasive method. Ex vivo studies and In vivo bioimpedance procedures, both invasive and non-invasive, on mammalians long bones are associated with promising results. In this work, out of a total of 568 papers, we reviewd 59 articles that mention long bone integrity by electric properties, be it Bioimpedance Analysis, Electrical Impedance Spectroscopy or Electrical Impedance Tomography. The papers are described in three sections, ―Ex vivo measurements‖, ―In vivo invasive measurements‖ and ―In vivo non-invasive measurements‖. This review allows to establish the basics to planning the development of new technology to detect bone fracture via bioimpedance measurements.

La bioeconomía es la ciencia de la gestión de la sustentabilidad. Su finalidad es alcanzar un desarrollo socio-económico sostenible, a través de la utilizacion eficiente de los recursos naturales. Se la puede considerar un nuevo paradigma económico. Un concepto más bien flexible, o mejor dicho adaptable a cada región, para que no sea la región la que se amolde a las necesidades exteriores sino que pueda la región dar al exterior lo más conveniente y propio que su ecosistema le permite ofrecer. De hecho, cada país define qué temas son parte de su bioeconomía, por ejemplo: para Finlandia lo es casi ex-clusivamente el sector forestal, mientras que para Alemanía lo son el biogás y los biocombustibles, pero no lo son las aplicaciones a la salud, las que si forman parte de la bioeconomía argentina. Algunos de los principios fundamentales de la bioeconomía son:-Defender el medio ambiente y asegurar la capacidad de regeneración de la biodiversidad.-Cerrar los ciclos de materia. En la naturaleza no existe el concepto de residuo, los deshechos de unos seres vivos se convierten siempre en el alimento de otros.-Centrar la producción y el consumo en lo local.-Actuar desde lo colectivo. En la evolución de la naturaleza ha sido más importante la cooperación que la competencia. Somos seres interdependientes.-Promover la mejora del bienestar y la equidad social.-Usar recursos renovables y energías limpias para evitar la destrucción y contaminación de los eco-sistemas. Estos principios están en contraposición con lo que plantea el actual sistema productivo global, donde la utilización desmedida de los recursos físicos –llegando a la devastación de algunos-pone en riesgo al mismo sistema. Es por esto que el cambio, aunque inminente, debe ser progresivo, siendo intere-sante un planteo manifestado por algunos científicos, como Alejandro Mentaberry, quien afirma que ante la restricción al acceso de recursos físicos se requiere mayor eficiencia productiva, la cual impli-ca un mayor conocimiento básico y tecnológico (esto es un motor autónomo de los cambios) y que la misma debe implementarse en un contexto de sustentabilidad ambiental, económica y social. Estos " pasos " conducen a un hecho concreto: el final de la sociedad industrial tal como se la conoce. La implementación de este paradigma como solución implica modificar la cultura del consumo. Hoy en día la salud es un bien de consumo (más allá que los derechos humanos establezcan lo contrario) al que uno accede en una farmacia o en una institución hospitalaria: sea un medicamento, una reso-nancia magnética, una cirugía estética, etc. (Mentaberry, 2014). Dentro de los canones precedentemente expuestos y considerando al sistema de salud como parte de la sociedad de consumo a transformar, presentamos como una posible herramienta de transforma-ción, una técnica diagnóstica que posee como características intrínsecas algunos de los objetivos a alcanzar: la bioimpedancia. La bioimpedancia se define como la medición de impedancia sobre un sistema biológico. Siendo la impedancia un parámetro medible de oposición a una corriente en un circuito eléctrico cuando se aplica una tensión; esta relación entre impedancia, corriente y tensión es descripta por medio de la ley de Ohm. Cuando se habla de impedancia, significa que la señal aplicada (tensión o corriente) es alternada en el tiempo, por lo que posee una frecuencia o período de repetición durante el mismo. El objetivo de estas notas es describir someramente algunas aplicaciones de mediciones de bioimpedancia, focalizándonos especialmente en la detección de lesiones óseas por medio de la medición de este parámetro físico, ya que cumple con los requerimientos para aportar soluciones dentro del ámbi-to de la bioeconomía.

The impedance, capacitance and conductance of aqueous sucrose polar solution are measured by employing impedance spectroscopy method and the current passing through the system for different DC voltages are measured implementing I-V method. The variation of electrical parameters with sucrose content in such solution exhibits a quasi-oscillatory nature, which is attributed to the random orientation of water and sucrose dipoles in the solution and their mutual interactions at the molecular level, including water-water, water-sucrose and sucrose-sucrose dipole interactions. To justify the quasi-oscillatory nature from analytical point of view, a theoretical model is developed on the basis of multi-body dipolar interactions of randomly distributed molecular dipoles. The experimental data agrees well with those obtained from the analytical model. The measurement of electrical parameters is performed within a frequency window of 100 Hz to 4 MHz for volume fractions of sucrose with respect to water, ranging from – pF – 266 pF, and 3 µS – 55 µS respectively for the sucrose volume fraction range considered. Current voltage measurements for the same concentration range are performed for a voltage swing between ±5 V and the obtained values vary from +20 µA to-25 µA. The study represents a deterministic approach to analyze the effective nature of a sucrose solution in terms of dielectric polarization of the system which finds application in sucrose quality assessments.

This paper presents a microprocessor system, working with integrated electrical impedance scanner AD5933 (Analog Devices). The device was built as an universal evaluation board, which should aid in development of bioelectrical impedance measurement instruments that can be used in a practical, commercial field. Besides that, an analysis and review of electrical devices used in bioimpledance measurements were made (directed onto tissues, including fluids, tissue to electrode interfaces, human body in general).

Wideband excitation signal with finite prominent harmonic components is desirable for fast bioimpedance spectroscopy (BIS) measurements. This work introduces a simple method to synthesize and realize a type of periodical stair-step multifrequency synchronized (MFS) signal. The Fourier series analysis shows that the p-order MFS signal í µí±“(í µí±, í µí±¡) has constant 81.06% energy distributed equally on its p 2 í µí±› th primary harmonics. The synthesis principle is described firstly and then two examples of the 4-order and 5-order MFS signals, í µí±“(4, í µí±¡) and í µí±“(5, í µí±¡), are synthesized. The method to implement the MFS waveform based on a field-programmable gate array (FPGA) and a digital to analog converter (DAC) is also presented. Both the number and the frequencies of the expected primary harmonics can be adjusted as needed. An impedance measurement experiment on a RC three-element equivalent model is performed, and results show acceptable precision, which validates the feasibility of the MFS excitation.

Bioelectronic interfaces require electrodes that are mechanically flexible and chemically inert. Flexibility allows pristine electrode contact to skin and tissue, and chemical inertness prevents electrodes from reacting with biological fluids and living tissues. Therefore, flexible gold electrodes are ideal for bioimpedance and biopotential measurements such as bioimpedance tomography, electrocardiography (ECG), electroencephalography (EEG), and electromyography (EMG). However, a manufacturing process to fabricate gold electrode arrays on plastic substrates is still elusive. In this work, a fabrication and low-temperature sintering (≈200 °C) technique is demonstrated to fabricate gold electrodes. At low-temperature sintering conditions, lines of different widths demonstrate different sintering speeds. Therefore, the sintering condition is targeted toward the widest feature in the design layout. Manufactured electrodes show minimum feature size of 62 μm and conductivity values of 5 × 10 6 S m−1. Utilizing the versatility of printing and plastic electronic processes, electrode arrays consisting of 31 electrodes with electrode-to-electrode spacing ranging from 2 to 7 mm are fabricated and used for impedance mapping of conformal surfaces at 15 kHz. Overall, the fabrication process of an inkjet-printed gold electrode array that is electrically reproducible, mechanically robust, and promising for bioimpedance and biopotential measurements is demonstrated.

When pressure is applied to a localized area of the body for an extended time, the resulting
loss of blood flow and subsequent reperfusion to the tissue causes cell death and a pressure
ulcer develops. Preventing pressure ulcers is challenging because the combination of pressure
and time that results in tissue damage varies widely between patients, and the underlying
damage is often severe by the time a surface wound becomes visible. Currently, no method
exists to detect early tissue damage and enable intervention. Here we demonstrate a flexible,
electronic device that non-invasively maps pressure-induced tissue damage, even when such
damage cannot be visually observed. Using impedance spectroscopy across flexible electrode
arrays in vivo on a rat model, we find that impedance is robustly correlated with tissue health
across multiple animals and wound types. Our results demonstrate the feasibility of an
automated, non-invasive ‘smart bandage’ for early detection of pressure ulcers.

Electrical Impedance Spectroscopy (EIS) involves the injection of a constant current into tissue at different frequencies and measurement of the resultant voltages. The transfer impedance is then calculated, fitted to an appropriate model and parameters are extracted to describe the electrical properties of the tissue. This technique has been used for characterising oesophageal and cervical tissue. However, electrode/tissue interface impedance and tissue inhomogeneities limit the consistency of the technique. The objective of this research is to optimise the ability of a tetrapolar impedance probe to characterise tissue in terms of electrical impedance spectra. The existing electronics for driving current and measuring voltage were assessed. Measured data showed that the circuits failed to achieve the desired specifications, and that this was due to component tolerances and stray capacitances. However, stray capacitances might be reduced using negative impedance converters. The sensitivity distribution beneath the tetrapolar probe was investigated by using the Geselowitz theorem. Phantom experiments showed a reasonably good agreement between theory I would particularly like to thank my supervisor Prof. B. H. Brown and co-supervisor Prof. R. H. Smallwood for providing me with an opportunity to work on this thesis. I am grateful to my supervisor Prof. B. H. Brown for giving me the guidance and valuable contribution to complete this work. I would also like to thank my co-supervisor Prof. R. H. Smallwood for his support and help. I was greatly benefited by his valuable suggestions and help by providing me support in the completion of my Research Training Program in the first year. I would like to take this opportunity to thank Prof. Adrian Wilson for his constant support and his valuable contribution in the first two years of this thesis. I am also thankful to Dr. Andrew Leathard who was always available to help me with the problems I had regarding computing. I wish to thank Mr. Pete Milnes for his help with the electronics involved in this thesis. I would also like to thank all the staff members of the instrumentation laboratory from the department. I would also like to thank all the volunteers who spared time to participate in the experimental studies carried out for this work. I could not have thought of taking this opportunity of doing my Ph.D. without the strong encouragement, unfailing support and unparalleled help given by my dear wife Elisângela. I would like to thank her for her appreciation and understanding. I would also like to thank my parents for providing me with unfailing support throughout my engineering degree without which, it would have been impossible for me to pursue my higher studies. Finally, I am grateful to the Brazilian Government, through the National Council for Scientific and Technological Development-CNPq, for the financial support to complete my Ph.D.

The aims of this study were to analyze the usefulness of raw bioelectrical impedance (BI) parameters in assessing water compartments and fluid distribution in athletes. A total of 202 men and 71 female athletes were analyzed. Total body water (TBW) and extracellular water (ECW) were determined by dilution techniques, while intracellular water (ICW) was calculated. Fluid distribution was calculated as the ECW/ICW ratio (E:I). Phase angle (PhA), resistance (R) and reactance (Xc) were obtained through BI spectroscopy using frequency 50kHz. Fat (FM) and fat-free mass (FFM) were assessed by dual-energy X-ray absorptiometry. After adjusting for height, FM, FFM, age and sports category we observed that: PhA predicted ICW (females: β = 1.62, p < 0.01; males: β = 2.70, p < 0.01) and E:I (males and females: β = −0.08; p < 0.01); R explained TBW (females: β = −0.03; p < 0.01; males: β = −0.06; p < 0.01) and ECW (females: β =-0.02, p < 0.01; males: β = −0.03, p < 0.01) and ICW (females: β =-0.01, p < 0.053; males: β =-0.03 p < 0.01); and Xc predicted ECW (females: β = −0.06, p < 0.01; males: β = −0.12, p < 0.01). A higher PhA is a good predictor of a larger ICW pool and a lower E:I, regardless of body composition, age, height, and sports category. Lower R is associated with higher water pools whereas ECW expansion is explained by lower Xc. Raw BI parameters are useful predictors of total and extracellular pools, cellular hydration and fluid distribution in athletes.

The biological systems by which an arm is made (bone tissue, striated muscle, adipose in addition to the corresponding body fluids)[1] constitute an anisotropic and heterogeneous medium[2,3]. The works of Gabriel et al.[4] provide experimental information on the electrical properties (conductivity and permittivity) of all tissues that constitute a human limb ex vivo. For his part, Randles[5] proposes an electric model of bioimpedance for different biological systems based on their conductivity and permittivity: a parallel RC circuit (Randles Model). An equivalent electrical circuit is the modeling of a physical system based on its electrical properties or its equivalences[6]. In this modeled circuit all the physical laws can be applied as well as the circuit theorems and methods corresponding to the resolution of this class of electric circuits. Aim: This paper presents the modeling of the electrical properties in a sagittal section of a human arm by means of the equivalent electric circuit in order to reach the equivalent bioimpedance values with a bipolar measurement by applying an alternating current signal through surface electrodes to different frequencies (50Hz, 1kHz, 10kHz, 30kHz and 60kHz).

Cartel presentado por Ricardo Rendón-Rodríguez ante el comité científico en el Congreso Nacional de Nutrición Clínica por la Asociación Mexicana de Nutrición Clínica y Terapia Nutricional A.C.  (AMAEE)y Universidad Anáhuac México. Celebrado del 6 al 9 de Octubre del 2016 en la ciudad de Acapulco, Guerrrero. México.

Representando a: Instituto Nacional de Enfermedades Respiratorias (INER). Centro de Investigación en Enfermedades Infecciosas (CIENI)

Autor: Rendón-Rodríguez R.
Co-autores: Osuna-Padilla IA.  Aguilar-Vargas A. Villazón-De la Rosa A. Reyes-Terán G.

Bioimpedance analysis or bioelectrical impedance provides information related to the degree of hydration and nutrition, which exists in the human body. In recent years it has boomed creating many monitors that provide us with different items, such as, fat mass, fat-free mass, total body water, among others. This article aims to inform the principles of electricity needed to comprise a related Bioimpedance as well teach what this new discipline interface.

The Cole function is widely used in bioimpedance spectroscopy (BIS) applications. Fitting the measured BIS data onto the model and then extracting the Cole parameters (R 0 , R ∞ , α and τ ) is a common practice. Accurate extraction of the Cole parameters from the measured BIS data has great significance for evaluating the physiological or pathological status of biological tissue. The traditional least-squares (LS)-based curve fitting method for Cole parameter extraction is often sensitive to noise or outliers and becomes non-robust. This paper proposes an improved Cole parameter extraction based on the least absolute deviation (LAD) method. Comprehensive simulation experiments are carried out and the performances of the LAD method are compared with those of the LS method under the conditions of outliers, random noises and both disturbances. The proposed LAD method exhibits much better robustness under all circumstances, which demonstrates that the LAD method is deserving as an improved alternative to the LS method for Cole parameter extraction for its robustness to outliers and noises.

The aims of this study were to analyze the usefulness of raw bioelectrical impedance (BI) parameters in assessing water compartments and fluid distribution in athletes. A total of 202 men and 71 female athletes were analyzed. Total body water (TBW) and extracellular water (ECW) were determined by dilution techniques, while intracellular water (ICW) was calculated. Fluid distribution was calculated as the ECW/ICW ratio (E:I). Phase angle (PhA), resistance (R) and reactance (Xc) were obtained through BI spectroscopy using frequency 50kHz. Fat (FM) and fat-free mass (FFM) were assessed by dual-energy X-ray absorptiometry. After adjusting for height, FM, FFM, age and sports category we observed that: PhA predicted ICW (females: β = 1.62, p &lt; 0.01; males: β = 2.70, p &lt; 0.01) and E:I (males and females: β = -0.08; p &lt; 0.01); R explained TBW (females: β = -0.03; p &lt; 0.01; males: β = -0.06; p &lt; 0.01) and ECW (females: β = -0.02, p &lt; 0.01; males: β = -0.03, p &lt; 0.01) and...

When pressure is applied to a localized area of the body for an extended time, the resulting loss of blood flow and subsequent reperfusion to the tissue causes cell death and a pressure ulcer develops. Preventing pressure ulcers is challenging because the combination of pressure and time that results in tissue damage varies widely between patients, and the underlying damage is often severe by the time a surface wound becomes visible. Currently, no method exists to detect early tissue damage and enable intervention. Here we demonstrate a flexible, electronic device that non-invasively maps pressure-induced tissue damage, even when such damage cannot be visually observed. Using impedance spectroscopy across flexible electrode arrays in vivo on a rat model, we find that impedance is robustly correlated with tissue health across multiple animals and wound types. Our results demonstrate the feasibility of an automated, non-invasive 'smart bandage' for early detection of pressure ulcers.

El siguiente trabajo presenta una revisión de las propiedades eléctricas de los tejidos biológicos. Los tópicos incluidos en el trabajo son el estudio, caracterización y técnicas de medición. Se aborda el tema de las propiedades de conductividad (σ) y permitividad (ε) eléctrica de los tejidos y los modelos creados para su estimación y aproximación. Se presentan las características de los elementos de medición, ventajas y desventajas de los diferentes métodos creados y sus aplicaciones. Se mencionan algunos de los tipos de señales más utilizadas en cuanto a corriente y frecuencia de aplicación. Finalmente se presentan algunas recomendaciones a tener en cuenta al momento de realizar mediciones in vivo, para disminuir los errores debido a las múltiples fuentes fisiológicas. Esta revisión permitió obtener los lineamientos y condiciones de un trabajo de medición de impedancia de fémur que se encuentra en desarrollo.

Part of work reproduced by – Sayed Parvez Ahmed I follow these books for by work: 1. Methods of Theoretical Physics, Part I and II , by Philip McCord Morse , Herman Feshbach 2. Mathematical Methods for Physicists, Seventh Edition: A Comprehensive Guide , by by George B. Arfken , Hans J. Weber 3. Mathematical Methods of Physics (2nd Edition) by by Jon Mathews , Robert L. Walker An Application of Electromagnetic Lead Theory to Impedance Plethysmography.-David B. Geselowitz. Example: Consider a sphere of radius R with a central spherical region of radius aR. Let the inner region have a conductivity g 1 and the outer spherical shell a conductivity g 2. Let current I be injected at the North Pole and removed at the South Pole as shown in the figure (Kindly see the figure in the original journal). Laplace's equation 2 0 V . Laplace's equation in spherical coordinates: 2 22 2 2 2 2 2 1 1 1 () (sin) sin sin Let it be V(r, )=R(r) ()   (3 Putting the value of V(r,θ) in 2, 2 () (sin) 0 sin RR r rr

Mechanotransduction is of fundamental importance in cell physiology, facilitating sensing in touch and hearing as well as tissue development and wound healing. This study used an impedance sensor to monitor the effective resistance and permittivity of artificial tissues, alginate hydrogel with encapsulated fibroblasts, which were kept viable through the use of a bespoke microfluidic system. The observed transient impedance responses upon the application of identical compressive normal loads differed between acellular hydrogels and hydrogels in which fibroblasts were encapsulated. These differences resulted from changes in the conductivity and permeability of the hydrogel due to the presence of the encapsulated fibroblasts, and transient changes in ion concentrations due to mechanotransduction effects.

The aims of this study were to analyze the usefulness of raw bioelectrical impedance (BI) parameters in assessing water compartments and fluid distribution in athletes. A total of 202 men and 71 female athletes were analyzed. Total body water (TBW) and extracellular water (ECW) were determined by dilution techniques, while intracellular water (ICW) was calculated. Fluid distribution was calculated as the ECW/ICW ratio (E:I). Phase angle (PhA), resistance (R) and reactance (Xc) were obtained through BI spectroscopy using frequency 50kHz. Fat (FM) and fat-free mass (FFM) were assessed by dual-energy X-ray absorptiometry. After adjusting for height, FM, FFM, age and sports category we observed that: PhA predicted ICW (females: β = 1.62, p < 0.01; males: β = 2.70, p < 0.01) and E:I (males and females: β = −0.08; p < 0.01); R explained TBW (females: β = −0.03; p < 0.01; males: β = −0.06; p < 0.01) and ECW (females: β =-0.02, p < 0.01; males: β = −0.03, p < 0.01) and ICW (females: β =-0.01, p < 0.053; males: β =-0.03 p < 0.01); and Xc predicted ECW (females: β = −0.06, p < 0.01; males: β = −0.12, p < 0.01). A higher PhA is a good predictor of a larger ICW pool and a lower E:I, regardless of body composition, age, height, and sports category. Lower R is associated with higher water pools whereas ECW expansion is explained by lower Xc. Raw BI parameters are useful predictors of total and extracellular pools, cellular hydration and fluid distribution in athletes.

Biological tissues have a complex-impedance, or bio-impedance, profile which changes with respect to frequency. This is caused by dispersion mechanisms which govern how the electromagnetic field interacts with the tissue at the cellular and molecular level. Measuring the bio-impedance spectra of a biological sample can potentially provide insight into the sample's properties and its cellular structure. This has obvious applications in the medical, pharmaceutical and food-based industrial domains. However, measuring the bio-impedance spectra non-destructively and in a way which is practical at an industrial-scale presents substantial challenges. The low-conductivity of the sample requires a highly sensitive instrument, while the demands of industrialscale operation require a fast high-throughput sensor of rugged design. In this paper, we describe a multi-frequency magnetic induction spectroscopy (MIS) system suitable for industrial-scale, non-contact, spectroscopic bioimpedance measurement over a bandwidth of 156 kHz-2.5 MHz. The system sensitivity and performance are investigated using calibration and known reference samples. It is is shown to yield rapid and consistently sensitive results with good long-term stability. The system is then used to obtain conductivity spectra of a number biological test samples, including yeast suspensions of varying concentration and a range of agricultural produce, such as apples, pears, nectarines, kiwis, potatoes, oranges and tomatoes.

ABSTRACT Bioimpedance analysis or bioelectrical impedance provides information related to the degree of hydration and nutrition, which exists in the human body. In recent years it has boomed creating many monitors that provide us with different items, such as, fat mass, fat-free mass, total body water, among others. This article aims to inform the principles of electricity needed to comprise a related Bioimpedance as well teach what this new discipline interface.

Background: A correct perception of the body image, as defined by comparison with actual anthropometric analyses, is crucial to ensure the best possible nutritional status of each individual. Bioimpedance analysis (BIA) represents a leading technique to assess body composition parameters and, in particular, the fat mass. This study examined the self-perception of body image at various levels of adiposity proposing a new index. Methods: We investigated 487 young Italian adults (mean age of males: 21.9 ± 2.4 years; mean age of females: 21.0 ± 2.2 years). Each subject could choose, on the Contour Drawing Rating Scale, the silhouette that he/she considered most resembling his/her perceived body image as well as his/her ideal body image. On each subject, we performed anthropometric measurements and determined the values of Fat mass and %Fat with BIA. A new index, FAI FAT (Feel fat status minus Actual fat status Inconsistency), was developed to evaluate possible fat status perception inconsistencies by BIA. Results: Based on ideal and feel body image comparison, women showed higher dissatisfaction than men and preferred slimmer silhouettes. FAI FAT values indicated that the fat status perception was correct in the majority of the examined individuals and only three subjects showed a serious misperception. Conclusions: Our findings suggest that FAI FAT is an appropriate index for assessing the perceived fat status from the body image when compared with data obtained by BIA. In a population, the use of this index will allow the correct identification of groups at risk for eating disorders.