Bio-electrical impedance spectroscopy: alternatives for the conventional hand-to-foot measurements

Assessment of bioimpedance spectroscopy devices: a comparative study and error analysis of gold-plated copper electrodes

Objective. Bioimpedance spectroscopy (BIS) is a non-invasive diagnostic tool to derive fluid volume compartments from frequency dependent voltage drops in alternating currents by extrapolating to the extracellular resistance (R0) and intracellular resistance (Ri). Here we tested whether a novel BIS device with reusable and adhesive single-use electrodes produces results which are (in various body positions) equivalent to an established system employing only single-use adhesive electrodes.Approach. Two BIS devices ('Cella' and the 'Body Composition Monitor' [BCM]) were compared using four dedicated resistance testboxes and by measuring 40 healthy volunteers.Invivocomparisons included supine wrist-to-ankle (WA) reference measurements and wrist-to-wrist (WW) measurements with pre-gelled silver/silver-chloride (Ag/AgCl) electrodes and WW measurements with reusable gold-plated copper electrodes.Main results. Coefficient of variation were <1% for all testbox measurements with both BIS devices. Accuracy was within ±1% of true resistance variability, a threshold which was only exceeded by the Cella device for all resistances in a testbox designed with a lowR0/Riratio.Invivo, WA-BIS differed significantly between BIS devices (p< 0.001). Reusable WW electrodes exhibited larger resistances than WW-BIS with Ag/AgCl electrodes (R0: 738.36 and 628.69 Ω;Ri: 1508.18 and 1390 Ω) and the relative error varied from 7.6% to 31.1% (R0) and -15.6% to 37.3% (Ri).Significance. Both BIS devices produced equivalent resistances measurements but different estimates of body composition bothinsilicoand in WA setupsinvivo, suggesting that the devices should not be used interchangeably. Employing WW reusable electrodes as opposed to WA and WW measurement setups with pre-gelled Ag/AgCl electrodes seems to be associated with measurement variations that are too large for safe clinical use. We recommend further investigations of measurement errors originating from electrode material and current path.

Knee-to-knee Bioimpedance Measurements to Monitor Changes in Extracellular Fluid in Haemodynamic-unstable Patients During Dialysis

The feasibility of bioimpedance spectroscopy (BIS) techniques for monitoring intradialytic changes in body fluids is advancing. The aim of this study was to compare the knee-to-knee (kkBIS) with the traditional whole-body (whBIS) with respect to continuous assessment of fluid volume status in hemodialysis patients. Twenty patients divided into two groups, hemodynamically stable and unstable, were recruited. Bioimpedance data from two different electrodes configurations (hand-to-foot and knee-to-knee) were collected and retrospectively analysed. A good correlation between the two methods with respect to changes in extracellular resistance (R_e) and R_e normalized for ultrafiltration volume (ΔR_e/UFV) with p < 0.001 was observed. The relationship between relative change (%) in ΔR_e and that in patient weight was most notable with kkBIS (4.82 ± 3.31 %/kg) in comparison to whBIS (3.69 ± 2.90 %/kg) in unstable patients. Furthermore, results based on kkBIS showed a reduced ability of the thigh compartments to keep up with the volume changes in the trunk for unstable patients. kkBIS provided a comparable sensitivity to whBIS even in patients at risk of intradialytic hypotension while avoiding the need for the complex implementation imposed by whBIS or other configurations.

Resistivity coefficients for body composition analysis using bioimpedance spectroscopy: effects of body dominance and mixture theory algorithm

Body composition is commonly predicted from bioelectrical impedance spectroscopy using mixture theory algorithms. Mixture theory algorithms require the input of values for the resistivities of intra-and extracellular water of body tissues. Various derivations of these algorithms have been published, individually requiring resistivity values specific for each algorithm. This study determined apparent resistivity values in 85 healthy males and 66 healthy females for each of the four published mixture theory algorithms. The resistivity coefficients determined here are compared to published values and the inter-individual (biological) variation discussed with particular reference to consequential error in prediction of body fluid volumes. In addition, the relationships between the four algorithmic approaches are derived and methods for the inter-conversion of coefficients between algorithms presented.

Bioelectrical Impedance Methods for Noninvasive Health Monitoring: A Review

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.

A novel bioimpedance technique to monitor fluid volume state during hemodialysis treatment

Bioimpedance spectroscopy is a potential candidate for monitoring of body fluids during dialysis. In this article, the suitability of knee-to-knee (KK) as an alternative to wrist-to-ankle (WA) bioimpedance spectroscopy measurements during dialysis is evaluated. Measurements on eight patients (22 dialysis sessions) showed a good correlation between the change in extracellular resistance (Re) in KK and WA measurements. A deeper analysis indicated that the change in Re normalized for ultrafiltrated volume [DeltaRe/UFV (%/L)] depends on the characteristics of the patient: clinically stable patients [with a presumed lower extracellular fluid - total body volume (VB) relationship] show a higher DeltaRe/UFV (%/L) mean +/- standard deviation (WA: 8.90 +/- 1.9 and KK: 8.29 +/- 2.2) than clinically unstable patients with pitting peripheral edema (WA: 2.10 +/- 0.8 and KK: 2.07 +/- 0.2). Simulations based on bioimpedance equations considering Hanai theory confirm the results. The KK method, especially in combination with proper use of the introduced DeltaRe/UFV (%/L) normalization could possibly offer new options for comfortable online monitoring and the evaluation of fluid volume state during dialysis.

Estimativa da composição corporal e análise de concordância entre analisadores de impedância bioelétrica bipolar e tetrapolar

O objetivo deste estudo foi analisar as estimativas da composição corporal e a concordância das medidas produzidas por meio de dois diferentes analisadores de impedância bioelétrica em homens adultos jovens. Vinte e dois sujeitos (23,6 ± 2,9 anos; 73 ± 6,8kg; 177,6 ± 6,0cm; 23,1 ± 1,9kg/m²), aparentemente saudáveis, foram submetidos a medidas de impedância bioelétrica por meio dos analisadores tetrapolar de corpo inteiro (TCI, Biodynamic Body Composition Analyser, modelo 310) e bipolar para membros superiores (BMS, Omron tm, modelo HBF-306BL) após jejum de 12h. Estimativas da gordura corporal relativa (%GC), massa livre de gordura (MLG) e massa gorda (MG) foram estabelecidas a partir das informações fornecidas pelos dois equipamentos. Nenhuma diferença estatisticamente significante foi verificada para %GC (10,9 ± 4,3 vs. 10,0 ± 4,2%; P = 0,09), MG (8,1 ± 3,5 vs. 7,4 ± 3,5kg; P = 0,10) e MLG (64,9 ± 5,2 vs. 65,5 ± 4,9kg; P = 0,09) entre TCI e BMS, respectivamente. Correlações positivas e significantes (P < 0,001) foram encontradas entre os analisadores para MLG (r = 0,948), MG (r = 0,891) e %GC (r = 0,859). Os limites de concordância foram de -0,6 ± 3,2kg para a MLG (r = 0,135; P = 0,551), 0,8 ± 4,5% para a %GC (r = 0,050; P = 0,824) e 0,6 ± 3,2kg para a MG (r = 0,032; P = 0,886). Os resultados sugerem que as estimativas da composição corporal por impedância bioelétrica não parecem ser afetadas pelo uso de diferentes analisadores (BMS vs. TCI) ou pela adiposidade corporal total.

A practical and precise approach to quantification of body composition in cancer patients using computed tomography images acquired during routine care

Human body composition is important in numerous cancer research domains. Our objective was to evaluate clinically accessible methods to achieve practical and precise measures of body composition in cancer patients. Dual-energy X-ray absorptiometry (DXA)-based analysis of fat and fat-free mass was performed in 50 cancer patients and compared with bioelectrical impedance analysis (BIA) and with regional computed tomography (CT) images available in the patients' medical records. BIA overestimated or underestimated fat-free mass substantially compared with DXA as the method of reference (up to 9.3 kg difference). Significant changes in fat-free mass over time detected with DXA in a subset of 21 patients (+2.2 +/- 3.2%/100 days, p = 0.003), was beyond the limits of detection of BIA. Regional analysis of fat and fat-free tissue at the 3rd lumbar vertebra with either DXA or CT strongly predicted whole-body fat and fat-free mass (r = 0.86-0.94; p < 0.001). CT images provided detail on specific muscles, adipose tissues and organs, not provided by DXA or BIA. CT presents great practical significance due to the prevalence of these images in patient diagnosis and follow-up, thus marrying clinical accessibility with high precision to quantify specific tissues and to predict whole-body composition.

Increased body fat percentage and physical inactivity are independent predictors of gestational diabetes mellitus in South Asian women

OBJECTIVE

This study aims to identify lifestyle predictors of gestational diabetes mellitus (GDM) in South Asian women. Pre-gravid body mass index, body composition, rate of weight gain during pregnancy, physical activity (PA) and dietary intake were studied.

DESIGN

Prospective cohort study (n=611) of South Asian women at Aga Khan University Hospital antenatal clinic in Karachi, Pakistan. Weight, height and body fat % were measured and data on PA, diet and socio-economic covariates were collected at baseline. A glucose screen was performed at 29.8+/-2.6 weeks.

RESULTS

Using logistic regression analysis for the full cohort, the risk of GDM increased with older maternal age (odds ratio (OR) 1.13, confidence interval (CI) 1.06-1.21), increased body fat % (OR 1.07, CI 1.03-1.13) and the risk was inversely associated with PA (100 kcal) (OR 0.79-0.99, CI 0.89). Using a nested case (n=49) control (n=98) design to study dietary intake, the risk of GDM decreased with increasing protein (% energy) in the diet (OR 0.75, CI 0.60-0.95).

CONCLUSIONS

Body fat %, physical inactivity and, possibly, diet quality are important modifiable risk factors for GDM. 2006.