Bioimpedance Spectroscopy Device Research Articles

Evaluation of a new bio-impedance spectroscopy device in healthy Japanese.

The use of a new bio-impedance spectroscopy device (Body Composition Monitor, BCM) in the field of dialysis became possible in Japan. However, it is unknown whether the data obtained using this apparatus are indicative for Japanese dialysis patients. To compare individual fluid status in healthy Japanese using the BCM device with the data obtained from healthy Caucasians. A total of 219 volunteers (female vs. male, 150 vs. 69; mean age, 68.8± 8.4 years; mean BMI, 22.6± 2.9 kg/m2) were enrolled. The measurement was performed by the end of the morning before exercise. Mean over-hydration (OH) level was 0.7± 0.8 L. Nearly 80% of subjects had values equivalent to the standard values of healthy Caucasians (-1.1∼1.1 L). Age had a weak positive correlation to OH. The fat tissue index levels were slightly lower in Japanese than in Caucasians. On the other hand, the levels of lean tissue index and ECW/ICW (E/I) ratio did not differ between Japanese and Caucasians. E/I ratio showed a good correlation with OH level. Fluid status of healthy Japanese was equivalent to the standard value of Caucasians. Although validity of using parameters from healthy Caucasians in healthy Japanese population was considered to be confirmed, validity of use in Japanese dialysis patients should be evaluated further using the parameters from healthy Caucasians.

Clinical praxis for assessment of dry weight in Sweden and Denmark: A mixed-methods study.

Overhydration is an independent predictor of mortality in hemodialysis (HD) patients. More than 30% of HD patients are overhydrated, motivating the development of new methods for assessing hydration status. This study surveyed clinical praxis and local guidelines for dry weight (DW) assessment in Swedish and Danish HD units, and examined if differences in routines and utilization of bioimpedance spectroscopy (BIS) and other assistive technology affected frequency of DW adjustments and blood pressure (BP) levels. Cross-sectional information on praxis, guidelines and routines, plus treatment-related data from 99 stratified patients were collected. Qualitative data were analyzed with content analysis and interpreted in convergence with statistical analysis of quantitative data in a mixed-methods design. Local guidelines concerning DW existed in 54% of the units. A BIS device was present in 52%, but only half of those units used it regularly, and no correlations to frequency of DW adjustments or BP were found. HD nurses were authorized to adjust DW in 60% of the units; in these units, the frequency of DW adjustments was 1.6 times higher and systolic BP pre-HD 8 mmHg lower. There is a wide variation in routines for DW determination, and there are indications that authorization of HD nurses to adjust DW may improve DW assessment. BIS is sparsely used; its implementation may have been delayed by uncertainty over how to manage the device and interpret measurements. Hence, better methods and guidelines for assessing DW and using BIS need to be developed.

Effect of Treatment on Body Fluid in Patients with Unilateral Aldosterone Producing Adenoma

Background: There is limited information about the effect of prolonged aldosterone excess and treatment on body fluid. Objective: To investigate the effects of adrenalectomy versus spironolactone treatment on body composition in primary aldosteronism (PA) patients with unilateral aldosterone producing adenoma (APA). Method: We determined body composition changes assessed by a bio-impedance spectroscopy device, the Body Composition Monitor (BCM). We examined pretreatment relative overhydration (%), relative fat (%) and relative lean tissue mass (%) in PA patients with APA and followed-up with patients after adrenalectomy or spironolactone treatment. We also assessed biomarkers related to fluid overload. Results: This prospective, multicenter study included 41 PA patients with APA. Twenty-one patients received adrenalectomy, whereas 20 patients were treated with spironolactone. Patients with APA receiving adrenalectomy, as compared with those treated with spironolactone, had significantly lower relative OH (p = 0.011) and urine albumin excretion (p = 0.003), and significantly higher urine sodium excretion (p < 0.001) and relative fat (p = 0.034) four weeks after treatment. These differences dissipated 12 weeks after the initial treatment. Patients who underwent adrenaelctomy had significantly decreased TNF-α and increased serum potassium level when compared to patients treated with spironolactone 4 and 12 weeks after treatment. Conclusions: In this pilot study, we found that adrenalectomy leads to the normalization of plasma aldosterone concentration followed by an earlier increase in renal sodium excretion and decreases in body fluid content, TNF-α, and urine albumin excretion. Adrenalectomy yields a therapeutic effect more rapidly, which has been shown to ameliorate overhydration in PA patients.

PO-0058 Bioimpedance Analysis In Children Aged 0–14 Years: Is There A Relation Between Phase Angle And Weight And Body Surface Area?

Background and aim Knowledge of fluid compartment changes and nutritional status is crucial when evaluating critically ill children, as well as measuring the effect of treatment. Current reference methods (DXA, dilution-methods etc.) are invasive, expensive, and/or time consuming and are therefore not suitable for routine paediatric examination. Bioimpedance analysis (BIA) offers an alternative to this since it is non-invasive, simple, portable and inexpensive. One BIA approach is to use values of total body fluid (TBF), extra- and intracellular fluid (ECF, ICF) and/or body cell mass (BCM). These are based on predictive equations and only proven in adults. Another approach is to use the phase angle (PA), which is a combination between the electrical resistance (R) of the electrolytic-containing TBF, and the capacitive reactance (X C ) of the cell membrane, both expressed in ohms (Ω). PA is an indicator of fluid compartment changes and cell membrane properties. Aim To investigate the relation between PA and weight (kg) and the body surface area, BSA (m 2 ). Methods Whole-body BIA was performed in 47 healthy children (boys=33, girls=14, 0–14 yr). PA (arctan = X C /R, degrees) was measured at 50-kHz with a bioimpedance spectroscopy device (Xitron 4200). Statistics: Spearman’s rank correlation (r), p Results Data showed high positive correlations between PA and weight and BSA (Table and Figure). Conclusions PA offers promising perspectives for further research areas (e.g. gender influence on PA). Potentially, PA could be a new way of monitoring fluid compartment changes and nutritional status in critically ill children.

Bioimpedance spectroscopy for assessment of fluid overload

Hur et al. report that fluid management guided by bioimpedance spectroscopy devices might improve cardiovascular parameters in patients on haemodialysis. However, caution is advisable when using these devices for extracellular volume assessment as overzealous reduction of target weights based on extracellular to intracellular volume ratios could cause premature loss of residual renal function.

Designing and implementing bioimpedance spectroscopy device by measuring impedance in a mouse tissue

Studies show that any complications including hemorrhage, lack of blood supply, lack of oxygen supply and death of cells in a tissue, will have a clear effect on electrical properties of that tissue. Thus, by measuring impedance of a set of tissues, potential problems of the damaged tissue may be found. Since electrical impedance is closely related to the measuring frequency, obviously, every tissue exhibits its own specific impedance according to its electrical properties at each frequency. This research project investigates design and manufacture method of a device for measuring tissue impedance at different frequencies. To this end, design of a multi frequency sinusoidal current source is required. This current source is built using a single harmonic Generator sample (Direct Digital Synthesizer AD9835) with working frequency (design-point frequency) between 1 Hz and 10 MHz and accuracy of 1 Hz and microcontroller (PIC16F628) capability. For measurement and display of tissue impedance, ARM AT91SAMs256 microcontroller was used. Thus, with this hardware created, it shows that there are significant impedance changes between mouse tissues.

A randomized controlled trial of long term effect of BCM guided fluid management in MHD patients (BOCOMO study): rationales and study design

BackgroundBioimpedance analysis (BIA) has been reported as helpful in identifying hypervolemia. Observation data showed that hypervolemic maintenance hemodialysis (MHD) patients identified using BIA methods have higher mortality risk. However, it is not known if BIA-guided fluid management can improve MHD patients’ survival. The objectives of the BOCOMO study are to evaluate the outcome of BIA guided fluid management compared with standard care.MethodsThis is a multicenter, prospective, randomized, controlled trial. More than 1300 participants from 16 clinical sites will be included in the study. The enrolment period will last 6 months, and minimum length of follow-up will be 36 months. MHD patients aged between 18 years and 80 years who have been on MHD for at least 3 months and meet eligibility criteria will be invited to participate in the study. Participants will be randomized to BIA arm or control arm in a 1:1 ratio. A portable whole body bioimpedance spectroscopy device (BCM—Fresenius Medical Care D GmbH) will be used for BIA measurement at baseline for both arms of the study. In the BIA arm, additional BCM measurements will be performed every 2 months. The primary intent-to-treat analysis will compare outcomes for a composite endpoint of death, acute myocardial infarction, stroke or incident peripheral arterial occlusive disease between groups. Secondary endpoints will include left ventricular wall thickness, blood pressure, medications, and incidence and length of hospitalization.DiscussionsPrevious results regarding the benefit of strict fluid control are conflicting due to small sample sizes and unstable dry weight estimating methods. To our knowledge this is the first large-scale, multicentre, prospective, randomized controlled trial to assess whether BIS-guided volume management improves outcomes of MHD patients. The endpoints of the BOCOMO study are of utmost importance to health care providers. In order to obtain that aim, the study was designed with very careful important considerations related to the endpoints, sample size, inclusion criteria, exclusion criteria and so on. For example, annual mortality of Beijing MHD patients was around 10%. To reach statistical significance, the sample size will be very large. By using composite endpoint, the sample size becomes reasonable and feasible. Limiting inclusion to patients with urine volume less than 800 ml/day the day before dialysis session will limit confounding due to residual renal function effects on the measured parameters. Patients who had received BIS measurement within 3 months prior to enrolment are excluded as data from such measurements might lead to protocol violation. Although not all patients enrolled will be incident patients, we will record the vintage of dialysis in the multivariable analysis.Trial registrationCurrent Controlled Trials NCT01509937

Influence of peritoneal dialysis solution on measurements of fluid status by bioimpedance spectroscopy

The accurate estimation of volume status is a central problem in dialysis patients. Recently, a bioimpedance spectroscopy (BIS) device (BCM Body Composition Monitor FMC, Germany) has attained growing interest in this regard. By processing the raw data for extracellular water (ECW) and intracellular water (ICW) by means of a validated body composition model, this device allows a quantification of the individual fluid overload (FO) compared to a representative healthy population. In this study, we addressed the issue whether the presence of peritoneal dialysate has an impact on measurements of FO by BIS in PD patients. Forty-two BIS measurements using the BCM device were performed both in the absence (D-) and presence (D+) of peritoneal dialysate in 17 stable PD patients. Data for ECW, ICW and FO (D+; D-) were analyzed by paired t test and linear regression. Mean FO was 0.99 ± 1.17 L in D- and 0.94 ± 1.27 in D+ (p = n.s. paired t test). Linear regression demonstrated an excellent degree of conformity between FO (D-) and FO (D+) (r (2) = 0.93). The presence of peritoneal fluid in PD patients has a negligible influence on measurements of FO by BIS. The BIS measurements can be therefore conveniently and reliably done without emptying the peritoneal cavity; this may facilitate the use of BIS in this particular group of patients.

The Study of Spectral Analysis of Heart Rate Variability in Different Blood Pressure Types in Euvolemic Peritoneal Dialysis Patients

Background: Heart rate variability (HRV) is an useful noninvasive tool to assess autonomic nervous system (ANS) function and may provide an insight into the understanding of the role of ANS in the pathogenesis of blood pressure (BP) abnormality in euvolemic continuous ambulatory peritoneal dialysis (CAPD) patients. Methods: In this cross-sectional study, 62 CAPD patients with normal hydration values (assessed by a bioimpedance spectroscopy device) were enrolled from our peritoneal dialysis (PD) unit. Patients were divided into three groups according to their BP: normotension (NT), hypertension (HT), and hypotension (HyT). Spectral analysis of HRV was measured by examination of the average heart rate using standard electrocardiogram in 5 min. Results: The HyT group had the lowest serum urea nitrogen among the three groups (all p < 0.05), and a lower serum potassium and albumin as compared with the NT group (p < 0.05). The HyT group also had the highest total power (TP) and highest frequency power (HF) among the three groups (all p < 0.05), and a lower normalized low frequency power (LF), LF/HF ratio, and a higher normalized HF as compared with the HT group (all p < 0.05). Conclusion: Our study suggested that autonomic insufficiency was present in euvolemic PD patients, and hypotensives had a relatively higher parasympathetic activity and blunted sympathetic activity.

Portable Bioimpedance Spectroscopy device and textile electrodes for mobile monitoring applications

A balanced body composition is necessary for a person's health and performance. Therefore, it is important to control the body composition continuously since complications and diseases due to dehydration often appear gradually. Based on these facts a miniaturized mobile Bioimpedance Spectroscopy device was developed that can be integrated into clothing and allows the continuous monitoring of a person's body water. The implemented system has been tested using different body models. The first measurements showed very precise and stable results. Besides the portable measurement system, textile electrodes are needed for continuous long term monitoring. Therefore, special textile electrodes were developed, tested and evaluated. The electrodes are structured in a specific way leading to a rougher surface. Such a surface improves the interface impedance and therefore optimizes the connection between electronic hardware and body. For comparison, five different structured electrodes were manufactured and tested on a special test setup that allows reproducible interface-impedance measurements using a dummy made of agar-agar to simulate the skin. It could be shown that the surface structure significantly influences the interface impedance in a positive way as compared to standard plane textile electrodes. In the future, a combination of the miniaturized BIS electronic and the structured textile electrodes could allow reproducible long term monitoring of a person's body composition.

Influence of ambient temperature on whole body and segmental bioimpedance spectroscopy measurements

Bioimpedance spectroscopy (BIS) measurements are easy to implement and could be used for continuous monitoring. However, several factors (e.g. environment temperature) influence the measurements limiting the accuracy of the technology. Changes in skin temperature produced by changes in ambient temperature are related with changes in skin blood flow and skin impedance. It is assumed that skin impedance change is responsible for the error observed in whole body and segmental measurements. Measurements including body parts more distant from the torso seem to be more affected. In the present article skin and segment impedance have been performed on healthy subjects under extreme changes in environment temperature (13-39 °C). A commercial BIS device with a range between 5 kHz and 1 MHz has been used for the measurements. The results indicate that not only skin impedance, but also impedance of deeper tissue (e.g. muscle) may be responsible for the influence of environment temperature on BIS measurements. Segmental (knee-to-knee) BIS measurements show a relative change of only 2 %, while forearm and whole body impedance changed 14 % and 8 % respectively.

Total body water changes after an exercise intervention tracked using bioimpedance spectroscopy: A deuterium oxide comparison

Bioimpedance spectroscopy (BIS) for the estimation of total body water (TBW) has advantages over isotope dilution techniques, including cost, portability, and ease of use. The aim of the current study was to determine the validity of a BIS device (Imp SFB7) for tracking changes in overfat and obese individuals. Sixty overfat and obese men and women (27+/-8 yr, 33.41+/-3.81%fat) participated in the study. TBW was estimated using BIS and deuterium oxide (D(2)O) before and after the ten-week intervention. Pre-and post-intervention BIS TBW estimations errors increased as body mass index (BMI), fat mass (FM), and fat-free mass (FFM) increased (p<0.05). Delta values were more accurate than pre- and post-TBW estimations (total error=1.45 L). Age significantly influenced pre- and post-TBW errors (p<0.05). Therefore, a regression equation was developed to correct for the pre- and post-BIS-estimated TBW errors: D(2)O TBW=11.478+0.743(BIS TBW)-2.429(Gender), (Men=1, Women=2). BIS can be considered an accurate tool for tracking changes in TBW regardless of variations in BMI, FM, FFM, or age in both overfat and obese men and women (BMI>24). Employing a BIS TBW equation is suggested over the development of resistivity coefficients based on BMI, FM, FFM or age.

Multifrequency bioelectrical impedance analysis and bioimpedance spectroscopy for monitoring fluid and body cell mass changes after gastric bypass surgery

There is a growing need for clinically applicable body composition assessment tools for extremely obese individuals. The objective of this research was to evaluate several bioimpedance techniques for monitoring changes in fluid, particularly intracellular water (reflecting body cell mass) after bariatric surgery. Fifteen extremely obese women (body mass index: 48.9+/-7.0 kg/m(2); age: 48+/-9 years) were assessed before (baseline; T1), and approximately 6 weeks after gastric bypass surgery (T2) by several multifrequency bioelectrical impedance analysis approaches (MFBIA; QuadScan 4000), a bioimpedance spectroscopy device (BIS; Hydra 4200), and multiple dilution. BIS provided intracellular water estimates that were comparable to criterion, based on mean comparisons, at both time points (T1: criterion: 24.2+/-3.1L, BIS: 24.0+/-3.7 L; T2: criterion: 20.6+/-3.7 L, BIS: 19.7+/-3.2L). MFBIA (with Deurenberg equations) provided comparable measures to criterion only at T2 (criterion: 20.3+/-3.7L, MFBIA: 20.6+/-2.7 L). Both MFBIA (with QuadScan proprietary equations) and BIS produced estimates of intracellular water change that were comparable to dilution. There was substantial variability in individual volume measures. Although MFBIA and BIS hold promise as convenient techniques for assessing fluid changes, individual variability in measurements makes them impractical for assessment of extremely obese patients in the clinical setting.

Towards improved cardiovascular management: the necessity of combining blood pressure and fluid overload

Hypertension and fluid overload (FO) are well-recognized problems in the chronic kidney disease (CKD) population. While the prevalence of hypertension is well documented, little is known about the severity of FO in this population. A new bioimpedance spectroscopy device (BCM-Body Composition Monitor) was selected that allows quantitative determination of the deviation in hydration status from normal ranges (DeltaHS). Pre-dialysis systolic blood pressure (BPsys) and DeltaHS was analysed in 500 haemodialysis patients from eight dialysis centres. A graphical tool (HRP-hydration reference plot) was devised allowing DeltaHS to be combined with measurements of BPsys enabling comparison with a matched healthy population (n = 1244). Nineteen percent of patients (n = 95) were found to have normal BPsys and DeltaHS in the normal range. Approximately one-third of patients (n = 133) exhibited reasonable control of BPsys and fluids (BPsys <150 mmHg and DeltaHS <2.5 L). In only 15% of patients (n = 74) was hypertension observed (BPsys >150 mmHg) with a concomitant DeltaHS >2.5 L (possible volume-dependent hypertension). In contrast, 13% of patients (n = 69) were hypertensive with DeltaHS <1.1 L (possible essential hypertension). In 10% of patients (n = 52), BPsys <140 mmHg was recorded despite DeltaHS exceeding 2.5 L. Our study illustrated the wide variability in BPsys regardless of the degree of DeltaHS. The HRP provides an invaluable tool for classifying patients in terms of BPsys and DeltaHS and the proximity of these parameters to reference ranges. This represents an important step towards more objective choice of strategies for the optimal treatment of hypertension and FO. Further studies are required to assess the prognostic and therapeutic role of the HRP.

Total body water estimations in healthy men and women using bioimpedance spectroscopy: a deuterium oxide comparison

BackgroundTotal body water (TBW) estimations have been used to estimate body composition, particularly fat-free mass, to aid in nutritional interventions, and to monitor hydration status. In the past, bioimpedance spectroscopy (BIS) devices have been used to estimate TBW. Previous investigations have examined the validity of the XiTRON 4000B (XiTRON Technologies) BIS device for estimating TBW. Recently, a new BIS device (Imp™ SFB7) has become available, claiming greater precision when estimating TBW. The Imp™ SFB7 (SFB7) is based on similar BIS principles, while offering increased portability and a greater range of frequencies when compared to older devices, such as the XiTRON 4000B (4000B). The purpose of this study was to examine the validity of the SFB7 for estimating total body water in healthy college-age men and women compared to the 4000B and deuterium oxide (D2O).MethodsTwenty-eight Caucasian men and women (14 men, 14 women; 24 ± 4 yrs; 174.6 ± 8.7 cm; 72.80 ± 17.58 kg) had their TBW estimated by the SFB7, the 4000B, and D2O.ResultsBoth BIS devices produced similar standard error of estimate (SEE) and r values (SFB7, SEE = 2.12L, r = 0.98; 4000B, SEE = 2.99L, r = 0.96) when compared to D2O, though a significant constant error (CE) was detected for the 4000B (2.26L, p ≤ 0.025). The 4000B produced a larger total error (TE) and CE (TE = 3.81L, CE = 2.26L) when compared to the SFB7 (TE = 2.21L, CE = -0.09L). Additionally, the limits of agreement were larger for the 4000B (-3.88 to 8.39L) than the SFB7 (-4.50 to 4.31L). These results were consistent when sex was analyzed separately, though women produced lower SEE and TE values for both devices.ConclusionThe 4000B and SFB7 are valid BIS devices when compared to D2O to estimate TBW in college-age Caucasian men and women. Furthermore, the new SFB7 device displayed greater precision in comparison to the 4000B, which may decrease the error when estimating TBW on an individual basis.

Ability of new octapolar bioimpedance spectroscopy analyzers to predict 4-component–model percentage body fat in Hispanic, black, and white adults

Background:New, vertical, 8-electrode bioimpedance spectroscopy (BIS) analyzers provide detailed body-composition and nutritional information within 2 min. This is the first report on BIS's accuracy in predicting relative fatness [percentage body fat (%BF)] in a heterogeneous sample according to a multicomponent model criterion. Objective:We compared %BF measurements from 2 BIS devices with those from a multicomponent model in a sample of Hispanic, black, and white adults. Design:Equal numbers of apparently healthy men and women (n = 75 of each) from each racial-ethnic group, diverse in body mass index and age, volunteered. Reference %BF (%BF4C) was computed by using a 4-component (4C) model with total bone mineral content obtained from dual-energy X-ray absorptiometry, body density from underwater weighing with measured residual lung volume, and total body water from traditional BIS. Estimations from InBody 720 (%BF720) and InBody 320 (%BF320) BIS analyzers were validated against %BF4C. Results:The %BF720 (r = 0.85, SEE = 5.19%BF) and %BF320 (r = 0.84, SEE = 5.17%BF) correlations were significant (P < 0.05) in the men; main effects were nonsignificant. Correlations for %BF720 (r = 0.88, SEE = 4.85%BF) and %BF320 (r = 0.89, SEE = 4.82%BF) also were significant in the women (P < 0.05); there was a main effect for method but not race-ethnicity. There were no sex-specific overestimations or underestimations at the extremes of the distributions. Conclusions:BIS estimates of %BF4C were well correlated in men and women. There were no significant methodologic differences in the men. The %BF4C was significantly underestimated by %BF720 and %BF320 in the women.

Design and preliminary evaluation of a portable device for the measurement of bioimpedance spectroscopy

Portable bioimpedance spectroscopy (BIS) devices are of great value for monitoring the pathological status of biological tissues in clinical and home environments. The two traditional techniques for measuring complex bioimpedance, the bridge method and quadrature demodulation method, are either time-consuming or often associated with high cost, high power consumption, and large board space, and therefore are not ideally suitable for designing a portable device for BIS measurement. This paper describes a novel design of a portable BIS device based on the magnitude-ratio and phase-difference detection method and its implementation using the newest generation of analog electronic products which greatly decrease the complexity of both hardware and software. In order to improve the accuracy of the device, a three-reference calibration algorithm was applied. Experimental sweep-frequency measurements on RC circuits were carried out to preliminarily evaluate the performances of the device. The results obtained by the device were found to be in good agreement with the results measured by a commercial impedance analyzer HP4194, with an overall mean error of 0.014% in magnitude and 0.136° in phase over a frequency range of 20 kHz to 1 MHz.