Relationship of obesity and visceral adiposity with serum concentrations of CRP, TNF-α and IL-6

Research pertaining to conductive polymers has gained significant traction in recent years, and their applications range from optoelectronics to material science. For all intents and purposes, conductive polymers can be described as Nobel Prize-winning materials, given that their discoverers were awarded the Nobel Prize in Chemistry in 2000. In this review, we seek to describe the chemical forms and functionalities of the main types of conductive polymers, as well as their synthesis methods. We also present an in-depth analysis of composite conductive polymers that contain various nanomaterials such as graphene, fullerene, carbon nanotubes, and paramagnetic metal ions. Natural polymers such as collagen, chitosan, fibroin, and hydrogel that are structurally modified for them to be conductive are also briefly touched upon. Finally, we expound on the plethora of biomedical applications that harbor the potential to be revolutionized by conductive polymers, with a particular focus on tissue engineering, regene...

Conductive Polymers: Opportunities and Challenges in Biomedical Applications

Under the alternating electrical excitation, biological tissues produce a complex electrical impedance which depends on tissue composition, structures, health status, and applied signal frequency, and hence the bioelectrical impedance methods can be utilized for noninvasive tissue characterization. As the impedance responses of these tissue parameters vary with frequencies of the applied signal, the impedance analysis conducted over a wide frequency band provides more information about the tissue interiors which help us to better understand the biological tissues anatomy, physiology, and pathology. Over past few decades, a number of impedance based noninvasive tissue characterization techniques such as bioelectrical impedance analysis (BIA), electrical impedance spectroscopy (EIS), electrical impedance plethysmography (IPG), impedance cardiography (ICG), and electrical impedance tomography (EIT) have been proposed and a lot of research works have been conducted on these methods for noninvasive tissue characterization and disease diagnosis. In this paper BIA, EIS, IPG, ICG, and EIT techniques and their applications in different fields have been reviewed and technical perspective of these impedance methods has been presented. The working principles, applications, merits, and demerits of these methods has been discussed in detail along with their other technical issues followed by present status and future trends.

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Bioelectrical Impedance Methods for Noninvasive Health Monitoring: A Review.

Protein energy malnutrition is common among persons with ESRD and contributes substantially to morbidity and mortality. The usual methods of nutritional assessment, such as anthropometry, can be misleading because of altered tissue hydration. Bioelectrical impedance analysis (BIA) has been recommended by some as a practical nutritional assessment tool but has not been validated in patients with ESRD. Thirty-three stable patients on maintenance hemodialysis were evaluated in an ambulatory clinical research center with simultaneous BIA, dual-energy x-ray absorptiometry, and deuterium oxide (D2O) and sodium bromide (NaBr) isotope dilution studies. Standard determinations of total body water (TBW) and body cell mass (BCM) were obtained and compared with values estimated by BIA. Two separate outpatient BIA measurements were also obtained approximately 2 wk before and after the clinical research center evaluation. BCM estimated by BIA was directly correlated (r = 0.92, P < 0.0001) with BCM determined by DEXA and NaBr. TBW estimated by BIA was directly correlated (r = 0.96, P < 0.0001) with TBW determined by deuterium oxide dilution. The reactance to resistance ratio (Xc/R) derived from BIA was inversely correlated (r = -0.73, P < 0.0001) with the extracellular water/TBW ratio determined by NaBr/D2O. Bland-Altman analyses showed that for TBW, BIA was in excellent agreement with D2O dilution. BCM was modestly underestimated by BIA compared with the dual-energy x-ray absorptiometry/NaBr standard and was adjusted by linear regression. The coefficients of variation on repeated BIA measurements were below 4%, demonstrating test-retest reliability. BIA is a valid and reliable method of nutritional assessment in maintenance hemodialysis patients.

Nutritional assessment with bioelectrical impedance analysis in maintenance hemodialysis patients.

A new technique for establishing dry weight in hemodialysis patients via whole body bioimpedance

Multifrequency bioelectrical impedance analysis was used to estimate the ratio of extracellular water (ECW) to total body water in subjects with end-stage renal disease. The body's resistance was measured at frequencies ranging from 1 kHz to 1 MHz. The impedance index (height2/resistance) determined at low frequency (5 kHz) correlated most closely with ECW (r = 0.886) using sodium bromide dilution as the standard of comparison. In contrast, the ratio of height squared to resistance determined at high frequency (500 kHz) correlated most closely with total body water (r = 0.974) using deuterium oxide dilution as the standard of comparison. The ratio of resistance at 500 kHz to resistance at 5 kHz was directly correlated (r = 0.767) with the ratio of ECW to total body water. Multifrequency bioelectrical impedance analysis may assist in the evaluation of body water distribution in endstage renal disease and other clinical disorders of fluid volume and/or distribution.

Multifrequency bioelectrical impedance estimates the distribution of body water

The bioelectrical impedance method was used to determine the haematocrit in patient blood samples. The resistance (R) and reactance (X) of a constant volume of blood were measured at a low (50 kHz) and high (1 MHz) frequency. These dual-frequency impedance measurements were then used to determine the intracellular and extracellular (plasma) fluid volume of the blood and thus the haematocrit in 308 blood samples. The values compared favourably with the microhaematocrit determined on the same samples, giving a correlation coefficient of 0.989 and a standard error estimation of 1.41%. Reactance at 1 MHz was a better parameter for predicting haematocrit than resistances. Factors affecting the resistivity of plasma, such as electrolyte and protein concentrations, were the error sources in the impedance technique. Our technique reduced such errors significantly. In conclusion, this electronic method can be used to measure haematocrit accurately and may be more desirable than conventional methods in certain clinical situations.

https://iopscience.iop.org/article/10.1088/0967-3334/15/2/003/pdf

An electronic method for rapid measurement of haematocrit in blood samples

A new bioelectrical impedance method was developed to determine the erythrocyte sedimentation rate (ESR) by measuring the settling velocity of red blood cells. A sample of blood was collected in a plastic tube with two electrodes, one positioned above the other. Measurements of electrical resistance were made in the upper region of the blood column. As the red blood cells settled towards the bottom of the container, the resistance decreased continuously. The velocity of settling red blood cells was calculated in 45 samples. The values obtained compared favourably with the ESR determined by the standard Westergren method, giving a correlation coefficient of 0.96 and a standard error estimation of 7.0 mm h-1. The authors conclude that bioelectrical impedance can be used to measure ESR accurately and that this method has important advantages over existing methods.

https://iopscience.iop.org/article/10.1088/0967-3334/15/4/011/pdf

A new bioelectrical impedance method for measurement of the erythrocyte sedimentation rate

Multifrequency bioelectrical impedance analysis (MFBIA) was used to determine the intracellular (ICW) and extracellular water (ECW) compartments in rats. Resistance and reactance were measured on various body segments with frequencies ranging from 1 KHz to 1 MHz. After initial measurements, 0.9% NaCl was injected intravenously or intraperitoneally, and changes in ECW and ICW were estimated by MFBIA. Important differences were found between segments. In the leg, estimated ECW increased in proportion to the volume of intravenous fluid infused, whereas estimated ICW changed minimally. However, in the trunk region, both estimated ECW and ICW were increased with intravenous and intraperitoneal injections. Our findings indicate that MFBIA has important limitations for quantifying fluid compartments in the trunk and thus in whole body, especially when applied to ill patients in whom sequestration of fluid in the trunk region frequently occurs.

Kichul Cha

Papers

Multifrequency bioelectrical impedance estimates the distribution of body water

An electronic method for rapid measurement of haematocrit in blood samples

A new bioelectrical impedance method for measurement of the erythrocyte sedimentation rate

Multifrequency bioelectrical impedance fails to quantify sequestration of abdominal fluid