Bioimpedance Spectroscopy Method Research Articles

Development of Bioimpedance Spectroscopy Technology in Medical Decision Support Systems

The purpose of research – development of bioimpedance spectroscopy methods to develop on their basis objective and realistically accessible criteria for assessing the severity and prognosis of diseases, as well as evaluating the effectiveness of treatment methods, developing criteria for the use of conservative therapy options and surgical interventions in severe patients.Methods. The proposed method involves the use of a recurrent modified Voigt model as a biomaterial segment impedance model. For each model of a biomaterial segment, a Cole plot is plotted in a given frequency range. At the stage of determining the parameters of each of the models, a recurrent procedure is performed, which is the solution of systems of nonlinear equations, starting from one link of the Voight model with a subsequent increase in their number at each iteration step, until the value of the approximation error by the Voight model of the Cole experimental plot reaches allowed value.Results. As a result of the study, fundamentally new results have been obtained that allow creating intelligent decision support systems for diagnosing socially significant diseases. A bioimpedance analysis model based on multifrequency bioimpedance measurement has been created, which makes it possible to decompose the biomaterial impedance into structural elements, on the basis of which to determine descriptors for neural network classifiers of medical risk. In the work, an analysis of classifier errors was carried out in classifying the risk of acute destructive pancreatitis, which showed that the maximum value of the quality indicators of various classifier models was 78%, the minimum was 62%, demonstrating close values to the quality indicators of the ultrasound diagnostic method.Conclusion. The use of multifrequency sensing and modified Voight models in neural network classifiers of medical risk makes it possible to build clinical decision support systems for diagnosing socially significant diseases, as well as the ability to improve classification quality indicators and expand the functionality of intelligent medical decision-making systems.

The role of bioimpedance spectroscopy method in severity and stages of breast cancer-related lymphedema.

The correlation between lymphedema severity and stages determined by standard diagnostic methods and Bioimpedance Spectroscopy (BIS) technique was examined in breast cancer-related lymphedema (BCRL) patients. The bioimpedance analyzer device was connected to the 1.0 cm disc electrodes which were connected to the affected and unaffected (healthy) arm of the patients. We evaluated the performance of the impedance (Z) at multiple frequencies (5-50-100-200 kHz) and phase angle (PA), resistance (R), and reactance (XC) at 50 kHz on the lymphedema severity and stages. Bioimpedance measurements were applied to all volunteers in cooperation with the Physical Therapy and Rehabilitation Department. In this study, the correlation between BCRL severity and stages and bioimpedance values was examined. A total of 31 female patients were recruited to compare the BIS technique with standard diagnostic techniques. The severity of lymphedema was found among the patients as follows; mild 14 (45.2%), moderate 10 (32.3%), and severe 7 (22.6%). The stage distribution of volunteers was; 15 (48.4%) patients in Stage 0, 10 (32.3%) patients in Stage 1, 5 (16.1%) patients in Stage 2, and 1 (3.2%) patient in Stage 3. The ratio of affected and unaffected arm bioimpedance mean values were calculated. Although, this ratio at 50-100-200 kHz Z and 50kHz R were significantly correlated with the lymphedema stages (p <0.05), there was no correlation and significant difference between the ratio of the bioimpedance values and lymphedema severity (p> 0.05). The BIS technique is timesaving and can determine lymphedema stages. We found a significant correlation between BCRL stages and BIS, and it appears that BIS is an appropriate, inexpensive, simple, and noninvasive technique for detecting the stages of BCRL.

Биоимпедансный анализ состояния поверхностных тканей пациента

A new method for analyzing physiological conditions of the patient's superficial tissues in vivo is proposed. Precision measurements of the complex electrical resistance were performed using the bioimpedance spectroscopy method. The design of a diagnostic module for complex non-invasive diagnostics of the physiological condition and processes in the surface tissues of a patient has been developed. An experimental verification of the developed method of bioimpedance spectroscopy was carried out on reference solutions and patient's superficial tissues in-vivo. A biophysical interpretation of the obtained results is proposed.

Ультразвуковая диагностика состояния поверхностных тканей пациента

A new method for analyzing physiological conditions of the patient's superficial tissues in vivo is proposed. Precision measurements of the complex electrical resistance were performed using the bioimpedance spectroscopy method. The design of a diagnostic module for complex non-invasive diagnostics of the physiological condition and processes in the surface tissues of a patient has been developed. An experimental verification of the developed method of bioimpedance spectroscopy was carried out on reference solutions and patient's superficial tissues in-vivo. A biophysical interpretation of the obtained results is proposed.

Bioimpedance analysis of the patient's superficial tissues

A new method for analyzing physiological conditions of the patient's superficial tissues in vivo is proposed. Precision measurements of the complex electrical resistance were performed using the bioimpedance spectroscopy method. The design of a diagnostic module for complex non-invasive diagnostics of the physiological condition and processes in the surface tissues of a patient has been developed. An experimental verification of the developed method of bioimpedance spectroscopy was carried out on reference solutions and patient's superficial tissues in vivo. A biophysical interpretation of the obtained results is proposed. Keywords: bioelectrical impedance analysis, bioimpedance spectroscopy, superficial tissues, diagnostic module, cell membranes, intracellular fluid.

A Discovery of Resonance Frequencies on Twelve Meridians of Human Body by Bioimpedance Spectroscopy Method

Objective: The resonance frequency (Fr) of twelve meridians was observed by means of sweep frequency of weak constant current, and a method of evaluating Fr was explored. Method: Four-electrode bioimpedance spectroscopy was used in the study. Constant current of 1~100Hz was applied from a phase-locked amplifier through the excitation electrode to the twelve meridians of 30 healthy subjects. Data were collected by the test electrode and the Fr of the twelve meridians was obtained by data fitting in Matlab. Result: Among the twelve meridians, the Fr of the small intestine meridian is the lowest, and the gallbladder meridian is the highest, which are 23.18±0.99Hz and 28.27±1.39 Hz, respectively. The mean resonance frequencies of meridians of the same name on hand and foot are 24.80±1.34Hz and 26.22±1.17Hz, respectively. The Fr of the Shao Yin meridian of the hands and feet is basically equal, the other five pairs of foot meridians are all higher than the hand meridian, and the difference of the Yang meridian of the same name is greater than the Yin meridian of the same name, the Fr of hand Shao Yang meridian, hand Tai Yang meridian and hand Yang Ming meridian were lower than those of foot meridians. The mean value of 6 pairs of yin and yang meridians are 25.59 ± 1.97Hz and 25.42 ± 0.70Hz, respectively. Conclusion: The resonance frequencies of the twelve meridians ranged from 23 to 28Hz approximately.

Changes in electrolyte concentrations alter the impedance during ischemia-reperfusion injury in rat brain

Objective: Ischemic stroke is a major cause of death and disability worldwide. Nowadays, electrical impedance spectroscopy is an emerging tool to differentiate between normal and stroke conditions. Approach: In this study, changes in the bio-impedance spectroscopy using a two-electrode method with varying frequencies from 100 to 35 kHz have been assessed in a model of global cerebral ischemia in anesthetized rats during normal, occlusion and reperfusion conditions. Global cerebral ischemia was induced by bilateral common carotid artery occlusion for 40 min following 40 min of reperfusion. The concentration of sodium, potassium, calcium and chloride ions in the whole rat brain was determined by electrolyte analyzer. For the interpretation of in vivo results, changes in electrical impedance with varying concentrations of sodium, potassium and calcium ions in artificial cerebrospinal fluid (aCSF) were also observed using the bio-impedance spectroscopy method. Main results: The in vivo bio-impedance analysis suggests that the impedance is consistently increased during occlusion as compared to the normal condition. The in vitro study revealed that the impedance escalates with an increase in the concentration of potassium and calcium ions and reduces with an increase in the concentration of sodium ions in aCSF. A further electrolyte analysis suggested that the level of sodium and chloride ions is significantly decreased and the level of calcium and potassium is significantly increased during occlusion as compared to the normal condition. Significance: These findings suggest that the increase in impedance during occlusion may be due to changes in the ionic concentration of the rat brain. The above in vivo and in vitro studies successfully demonstrated and interrelated the change in impedance with corresponding changes in ionic concentration.

Is 3-Carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF) a Clinically Relevant Uremic Toxin in Haemodialysis Patients?

3-Carboxy-4-methyl-5-propyl-2-furanpropionate (CMPF) is a metabolite of furan fatty acid and a marker of fish oil intake. CMPF is described as a protein-bound uremic toxin and interacts with free oxygen radicals, which can induce cell damages. However, the clinical consequences of CMPF accumulation in haemodialysis patients remain poorly documented. The aims of this study are to investigate potential association between CMPF levels and (i) biochemical and nutritional parameters; (ii) cardiovascular events and (iii) mortality. Two hundred and fifty-two patients undergoing maintenance haemodialysis were included. Routine clinical biochemistry tests and assay for CMPF by HPLC technique were performed at the inclusion. Body composition parameters were measured using a bioimpedance spectroscopy method. The enrolled patients were prospectively monitored for cardiovascular events and mortality. CMPF level was positively correlated with nutritional parameters and lean mass and is significantly higher in patients without protein-energy wasting. However, the multivariate linear regression analysis indicated that CMPF level was not independently associated with albumin, prealbumin, creatinemia and body mass index. Elevated serum CMPF was not associated with mortality and cardiovascular morbidity. Our results indicate that CMPF is not a relevant uremic toxin in haemodialysis and in contrast could be a marker of healthy diet and omega 3 intakes.

Effect of Strict Volume Control on Renal Progression and Mortality in Non-Dialysis-Dependent Chronic Kidney Disease Patients: A Prospective Interventional Study

Objective: The aim of this study was to examine the effect of volume status on the progressions of renal disease in normovolemic and hypervolemic patients with advanced non-dialysis-dependent chronic kidney disease (CKD) who were apparently normovolemic in conventional physical exam­ination. Materials and Methods: This was a prospective interventional study performed in a group of stage 3–5 CKD patients followed up for 1 year. Three measurements were made for volume and renal status for every patient. The fluid status was assessed by a bioimpedance spectroscopy method. A blood pressure (BP) value > 130/80 mm Hg prompted the initiation or dose increment of diuretic treatment in normovolemic patients. Result: Forty-eight patients (48%) were hypervolemic. At the end of the 1-year follow-up, hypervolemic patients were found to have a significantly lower estimated glomerular filtration rate and higher systolic BP compared to baseline. Hypervolemia was associated with an increased incidence of death. Conclusion: We have shown that maintenance of normovolemia with diuretic therapy in normovolemic patients was able to slow down and even improve the progression of renal disease. Volume overload leads to an increased risk for dialysis initiation and a decrease in renal function in advanced CKD. Volume overload exhibits a stronger association with mortality in CKD patients.

PP.17.25] BLOOD PRESSURE CHANGE DURING THE HEMODIALYSIS IN CHRONIC HEMODIALYSED PATIENTS IN RELATIONSHIP TO THE HYDRATION STATUS MEASURED CLINICALLY AND ALSO BY BIOIMPEDANCE SPECTROSCOPY

Objective: To assess blood pressure (BP) change in relation to hydration status measured clinically and by bioimpedance spectroscopy method (BIS) in chronic hemodialysed patients. Design and method: A 10 months, one centre retrospective analysis was performed on the group of 48 regularly hemodialysed patients (M/W: 15/33) to analyse the BP change in relationship to hydration status measured clinically (weight, dry weight, intradialytic weight gain,) and by BIS: overhydration (OH), extracellular water volume (ECW), total body water volume (TBW) and rates OH/ECW and ECW/TBW before and after the hemodialysis. Patients were divided into different regions based on their BP levels before hemodialysis and hydration status, which was measured by BIS. The relationship between BP and hydration status change was also evaluated. Results: The significant change of systolic BP (p < 0,001; 95%CI 3,7–7,0 - p < 0,004, 95%CI 0,49–3,8) and diastolic BP (p < 0,001; 95%CI 1,0–7,0 - p < 0,0038; 95%CI 0,49–3,8) was identified in the first 3 hours of the hemodialysis, and also in relation to the weight loss measured clinically (p < 0,001; r = 0,17) and to the hydration status assessed by BIS (p < 0,001; r = 0,19). The rate OH/ECW revealed a significant correlation to systolic BP (p < 0,02; r = 0,10) and ECW/TBW to diastolic BP (p < 0,006; r = 0,12) before hemodialysis in comparison to the clinically measured hydration. 6% of patients were found to have both normal level of BP (<140 mmHg) and overhydration (−1-+1l). In 32% of analysed group reached range of BP < 150 mmHg and overhyhydration <2,5l. Volume dependent hypertension (BP >150 mmHg; HS >2,5l) was documented in 27%. The region of severe heart impairment represented 33% of our group (BP <140 mmHg, overhydration >2,5l). 2% represented the population with BP >150 mmHg and mild overhydration 1,1–2,5l. Conclusions: It was identified that the amount of overhydration played an important role in one third of the analysed patient group. In addition, a decrease of blood pressure was observed in relation to the fluid removal. BIS hydration parameters seem to be more suitable predictors of blood pressure level before hemodialysis compared to the clinically measured hydration status.

Determination of Glucose-Dependent Dielectric Properties of Ringer Lactate Using Open-Ended Coaxial Probe Method

The reported work is the basis of exploration of non-invasive-continuous-blood-glucose monitoring technique using electrical bioimpedance spectroscopy method. This requires the determination of variation in dielectric properties of blood as a function of glucose. The present paper attempts to discuss the findings of in-vitro experiment performed in this direction. The experiment was performed to analyze the variations in dielectric properties of equivalent physiological solution as a function of glucose concentration over a frequency range from 100 MHz to 2.5 GHz. The glucose-dependent dielectric constant of ringer lactate samples prepared with different concentrations of d-glucose ranging from 100 to 500 mg/dL has been determined by employing open-ended coaxial probe method. The short-term repeatability of dielectric constant of DI water at a particular temperature found to be good. The real part of the dielectric constant of RL decreases with increase in glucose concentration along with frequency.

Bioimpedance spectroscopy method for investigating changes to intracranial dose during transcranial direct current stimulation.

Tissue resistance changes upon application of DC current. We posit that in a similar fashion, that scalp and skull resistances during trancranial direct current stimulation (tDCS) are variable, resulting in changes to intracranial dose. Transcranial magnetic stimulation (TMS), electoencephelogram (EEG), functional magnetic resonance imaging (fMRI), proton magnetic resonance spectroscopy ((1)H MRS) and functional near infrared spectroscopy (fNIRS) are technologies used to measure individual neural response to tDCS. These technologies are complex and may not be directly correlated to intracranial dose. We therefore present a bioimpedance spectroscopy method of measuring changes to the intracranial dose in vivo. Scalp resistance changes are measured during tDCS. Current flow through the scalp is calculated as the ratio of voltage measured on the scalp and scalp resistance. Variation of intracranial current is indirectly calculated from changes in the current shunted through the scalp. We thus demonstrate a novel methodology of on-line monitoring of scalp resistance and current as an objective feedback of estimated individual tDCS dose.

Fluid overload, pulse wave velocity, and ratio of brachial pre-ejection period to ejection time in diabetic and non-diabetic chronic kidney disease.

Fluid overload is one of the characteristics in chronic kidney disease (CKD). Changes in extracellular fluid volume are associated with progression of diabetic nephropathy. Not only diabetes but also fluid overload is associated with cardiovascular risk factors The aim of the study was to assess the interaction between fluid overload, diabetes, and cardiovascular risk factors, including arterial stiffness and left ventricular function in 480 patients with stages 4–5 CKD. Fluid status was determined by bioimpedance spectroscopy method, Body Composition Monitor. Brachial-ankle pulse wave velocity (baPWV), as a good parameter of arterial stiffness, and brachial pre-ejection period (bPEP)/brachial ejection time (bET), correlated with impaired left ventricular function were measured by ankle-brachial index (ABI)-form device. Of all patients, 207 (43.9%) were diabetic and 240 (50%) had fluid overload. For non-diabetic CKD, fluid overload was associated with being female (β = –2.87, P = 0.003), heart disease (β = 2.69, P = 0.04), high baPWV (β = 0.27, P = 0.04), low hemoglobin (β = –1.10, P<0.001), and low serum albumin (β = –5.21, P<0.001) in multivariate analysis. For diabetic CKD, fluid overload was associated with diuretics use (β = 3.69, P = 0.003), high mean arterial pressure (β = 0.14, P = 0.01), low bPEP/ET (β = –0.19, P = 0.03), low hemoglobin (β = –1.55, P = 0.001), and low serum albumin (β = –9.46, P<0.001). In conclusion, baPWV is associated with fluid overload in non-diabetic CKD and bPEP/bET is associated with fluid overload in diabetic CKD. Early and accurate assessment of these associated cardiovascular risk factors may improve the effects of entire care in late CKD.

Is fluid overload more important than diabetes in renal progression in late chronic kidney disease?

Fluid overload is one of the major presentations in patients with late stage chronic kidney disease (CKD). Diabetes is the leading cause of renal failure, and progression of diabetic nephropathy has been associated with changes in extracellular fluid volume. The aim of the study was to assess the association of fluid overload and diabetes in commencing dialysis and rapid renal function decline (the slope of estimated glomerular filtration rate (eGFR) less than -3 ml/min per 1.73 m2/y) in 472 patients with stages 4-5 CKD. Fluid status was determined by bioimpedance spectroscopy method, Body Composition Monitor. The study population was further classified into four groups according to the median of relative hydration status (△HS =fluid overload/extracellular water) and the presence or absence of diabetes. The median level of relative hydration status was 7%. Among all patients, 207(43.9 %) were diabetic. 71 (15.0%) subjects had commencing dialysis, and 187 (39.6%) subjects presented rapid renal function decline during a median 17.3-month follow-up. Patients with fluid overload had a significantly increased risk for commencing dialysis and renal function decline independent of the presence or absence of diabetes. No significantly increased risk for renal progression was found between diabetes and non-diabetes in late CKD without fluid overload. In conclusion, fluid overload has a higher predictive value of an elevated risk for renal progression than diabetes in late CKD.

Association of Fluid Overload With Kidney Disease Progression in Advanced CKD: A Prospective Cohort Study

Fluid overload is a common phenomenon in patients in a late stage of chronic kidney disease (CKD). However, little is known about whether fluid overload is related to kidney disease progression in patients with CKD. Accordingly, the aim of the study was to assess the association of the severity of fluid status and kidney disease progression in an advanced CKD cohort. Prospective observational cohort study. This cohort study enrolled 472 non-dialysis-dependent patients with CKD stages 4-5 who were in an integrated CKD care program from January 2011 to December 2011 and followed up until December 2012 or initiation of renal replacement therapy (RRT). Tertile of fluid overload, with cutoff values at 0.6 and 1.6 L. RRT, rapid estimated glomerular filtration rate (eGFR) decline (faster than 3 mL/min/1.73 m(2) per year), and change in eGFR. The severity of fluid overload was measured by a bioimpedance spectroscopy method. eGFR was computed using the 4-variable MDRD (Modification of Diet in Renal Disease) Study equation. During a median 17.3-month follow-up, 71 (15.0%) patients initiated RRT and 187 (39.6%) experienced rapid eGFR decline. The severity of fluid overload was associated with increased risk of RRT (tertile 3 vs tertile 1: adjusted HR, 3.16 [95% CI, 1.33-7.50]). Fluid overload value was associated with increased risk of rapid eGFR decline (tertile 3 vs tertile 1: adjusted OR, 4.68 [95% CI, 2.30-9.52]). Furthermore, the linear mixed-effects model showed that the reduction in eGFR over time was faster in tertile 3 than in tertile 1 (P=0.02). The effect of fluid volume variation over time must be considered. Fluid overload is an independent risk factor associated with initiation of RRT and rapid eGFR decline in patients with advanced CKD.

In VivoBlood Characterization From Bioimpedance Spectroscopy of Blood Pooling

Characterization of blood impedance properties is important to estimate clinical diagnostic indexes such as hematocrit, glucose level, and hydration. Current in vivo bioimpedance spectroscopy methods are performed on a body appendage and thus represent a combined measurement of all tissues in the measurement field, rather than the blood individually. This paper describes a novel in vivo measurement technique to calculate bioelectrical properties of blood while excluding the disturbances from surrounding tissues, based on analysis of the impedance changes caused by blood accumulation. The forearm was modeled as a cylinder containing anatomical structures such as skin-fat layer, muscles, and bones. Blood volume was modeled as the inner cylinder. A tetrapolar electrode system was applied to a human forearm, and the impedance curves measured with and without blood pooling were processed to calculate the impedance parameters of arterial blood. The bioelectrical parameters of blood were estimated by fitting the blood curve to a Cole-Cole model using the Levenberg-Marquardt (LM) nonlinear curve-fitting method. The proposed approach was verified using an experimental phantom, an equivalent circuit model, and a preliminary human experiment. Results show that electrical properties of blood and surrounding tissues can successfully be separated. Of Cole-Cole parameters, the characteristic frequency fc is the most reliable parameter to characterize blood bioelectrical properties. This method may allow a simplified measurement of blood characteristic parameters for many biomedical and clinical monitoring applications.

Total body water measurement by a modification of the bioimpedance spectroscopy method

We propose a method for calculating directly total body water (TBW) volumes (V (t)) from whole body resistance extrapolated at infinite frequency (R (infinity)) using a XITRON 4200 impedance meter. Mean TBW resistivities for men and women were determined from measurements of R (infinity) and fat-free mass (FFM(d)) measured by DXA in 58 healthy subjects assuming an average hydration coefficient of 73.2%. Mean differences between V (t) measured by our new method and those deduced from DXA data were +0.11 +/- 1.61 L for women and +0.13 +/- 2.16 L for men. For validation, this method was tested with the same resistivities against a 2nd group of 16 volunteers and the mean difference between V (t) from impedance and DXA was -0.80 +/- 1.43 L. Since the resistance at 50 kHz (R (50)) was found to be equal, in average, to 1.230 R (infinity) for men and 1.223 R (infinity) for women, this method can also be applied at 50 kHz with a similar accuracy by estimating R (infinity) from R (50). When our new method was applied to the monitoring of water loss during 28 dialysis runs performed on 13 patients, it predicted a mean water loss equal to 94% of ultrafiltered volume.

Generalizability of extracellular-to-intracellular fluid ratio using bio-impedance spectroscopy

Generalizability theory was used to investigate the score consistency of observed extracellular fluid/intracellular fluid (ECF/ICF) ratio measurements for both the global and leg-segmental bio-impedance spectroscopy methods. The test instrument used was a Xitron Hydra ECF/ICF Bio-Impedance Analyzer System, model 4200 (Xitron Technologies, San Diego, CA). Fifty able-bodied American men (17 to 72 years) and 50 able-bodied American women (17 to 76 years) volunteered as experimental subjects. Xitron continuous global and leg-segmental ECF/ICF procedures for testing were followed for assessing subjects in both the standing erect and lying supine postures. A two-facet, person-by-trial, completely crossed design was used, and all facets were treated as random. Data were independently analyzed for each method, each body posture and each sex group. The major findings of this study were: (1) the leg-segmental method was superior in producing the higher G-coefficients when compared to the global method regardless of gender or posture; (2) the global method resulted in higher G-coefficients in males compared to females regardless of posture; (3) when the global method was used, the relative and absolute error variances were higher for females while the opposite trend was observed when the segmental method was used and (4) when using the global method, the precision of the ECF/ICF ratio scores in females could be increased by simply using the mean of several trials (e.g., by using the mean of 5, 10 or more test trials).

Évaluation des méthodes d’aide à la détermination du poids sec des patients hémodialysés par bio-impédance

We have measured extracellular ( V E ) and total water ( V T ) volumes in 17 dialysed patients for a total of 46 runs by impedance using a Xitron Hydra 4200 device and the bio-impedance spectroscopy method (BIS). These volumes were used to test two methods of patient dry weight determination by impedance, that of Chamney et al., based on Ve/W ratio and that of Lopot et al. Based on V E /V T ratio where W denotes body weight. We recommend the 2 nd method, but using a new equation that we have proposed for calculating V T, which is more reliable than that of the Xitron.