Total body water measurement by a modification of the bioimpedance spectroscopy method (original) (raw)
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Medical & Biological Engineering & Computing, 2015
The objective of this study is to evaluate the accuracy of independent hydric data for the quantification of total body water (Vt), extracellular water (Ve) and intracellular water (Vi), obtained by a Z-Metrix multifrequency impedancemeter (ZM), in standing and lying position, with respect to the Xitron reference. In a second step, the aim is also to consider whether it is possible to quantify daily hydration. As part of the clinical study No. A01373-52-2008, 97 healthy subjects underwent ZM impedance with 29 of them also assessing Xitron. Note that the average repeatability error of the ZM impedancemeter is less than 0.5%. For total body water (Vt), we note a low R ² dispersion with an average of respectively 0.9 for men and 0.6 for women. The estimation of the total body water is more accurate for women with a maximum error of 1.8% in standing position against 3.9% for men in the same position. We note a low R ² dispersion respectively of 0.965 for men and of 0.84 for women. The estimation of extracellular water is equivalent with a maximum error of 3.1% in standing position for women against 2.97 % for men in the same position. The estimation of the total body water by direct measurement and by summing the volumes of extracellular and intracellular water obtained by the Z-Metrix ® shows very low dispersions with R ² equal to 0.89, and average error from 1.3 % for healthy women in lying position to 3.9% for healthy women in standing position. Finally, despite the impact of events on the daily impedance measurements, it is viable to track a subject's overall hydration.
Analytic assessment of the various bioimpedance methods used to estimate body water
Journal of applied physiology (Bethesda, Md. : 1985), 1998
Knowledge of patient fluid distribution would be useful clinically. Both single-frequency (SF) and impedance modeling approaches are proposed. The high intercorrelation between body water compartments makes determining the best approach difficult. This study was conducted to evaluate the merits of an SF approach. Mathematical simulation was performed to determine the effect of tissue change on resistance and reactance. Dilution results were reanalyzed, and resistance and parallel reactance were used to predict the intracellular water for two groups. Results indicated that the amount of intracellular and extracellular water conduction at any SF can vary with tissue change, and reactance at any SF is affected by all tissue parameters. Modeling provided a good prediction of dilution intracellular and extracellular water, but an SF method did not. Intracellular, extracellular, and total body water were equally predicted at all frequencies by SF resistance and parallel reactance. Extrace...
Journal of Physics: Conference Series, 2010
Prescription of an appropriate post hemodialysis (HD) dialysis target weight requires accurate evaluation of the degree of hydration. The aim of this study was to investigate whether a state of normal hydration as defined by calf bioimpedance spectroscopy (cBIS) could be characterized in HD and normal subjects (NS). cBIS was performed in 62 NS (33 m/29 f) and 30 HD patients (16 m /14 f) pre-and post-dialysis to measure extracellular resistance. Normalized calf resistivity at 5 kHz (ρ N,5 ) was defined as resistivity divided by body mass index. Measurements were made at baseline (BL) and at a state of normal hydration (NH) established following the progressive reduction of post-HD weight over successive dialysis treatments until the ρ N,5 was in the range of NS. Blood pressures were measured pre-and post-HD treatment. ρ N,5 in males and females differed significantly in NS (20.5±1.99 vs 21.7±2.6 10 -2 Ωm 3 /kg, p<0.05). In patients, ρ N,5 notably increased and reached NH range due to progressive decrease in body weight, and systolic blood pressure (SBP) significantly decreased pre-and post-HD between BL and NBH respectively. This establishes the use of ρ N,5 as a new comparator allowing the clinician to incrementally monitor the effect of removal of extracellular fluid from patients over a course of dialysis treatments.
Renal Replacement Therapy
Background: MLT-550N is a device to measure the body fluid volume based on bioimpedance spectroscopy. When extracellular water (ECW) or total body water (TBW) is measured with MLT-550N before and after hemodialysis, the change in ECW (ΔECW) or TBW (ΔTBW) is markedly larger than the change in body weight (ΔW). Good agreements between ΔECW and ΔTBW calculated by Moissl equations with ΔW were reported. The aim of this study was to develop novel equations to calculate the body fluid volume by modifying Moissl equations. Methods: A total of 466 measurements of 351 hemodialysis patients were used to develop the novel equations. The equations were based on the agreement between ΔECW and ΔW as a guide. The volume of intracellular water was postulated to be constant during hemodialysis. For evaluation of the equations, 5485 measurements of 627 patients were used. Agreements between values of two groups were assessed with Lin's concordance correlation coefficients. The normal edema ratio (ER = ECW/TBW) corrected with the fat ratio (fcER) according to the parameters of normally hydrated lean and adipose tissues was used as the reference for normal hydration. The fluid status at dry weight was considered to be close to normal. The absolute values of the deviated ratio of actual ER (aER) from fcER (dER = (aER−fcER)/fcER) were compared. In this study, 1 L of body water corresponded to 1.02 kg of body fluid according to a previous report. Results: The concordance correlations between ΔW and 1.02•ΔECW or 1.02•ΔTBW with the novel equations were higher than with the MLT method or Moissl equations (0.896, 0.596 vs. 0.411, 0.375 or 0.813, 0.411, respectively). The median value of dER with the novel equations was the lowest (0.062) compared with those of the MLT method and Moissl equations (0.164 and 0.144) (p < 0.001). Conclusions: The agreements between ΔECW or ΔTBW and ΔW were improved by the novel equations compared with the MLT method or Moissl equations. Based on the relation between aER and fcER at dry weight, the fluid volume calculated using the novel equations may be more adequate than those with the MLT method or Moissl equations.
Acta Diabetologica, 2003
Bioelectric impedance analysis (BIA) is commonly used in clinical settings and field studies for estimating total, extracellular, and intracellular water compartments. The objective of the present study was to carry out a meta-analysis of published reports in which total body water (TBW) was estimated using BIA techniques and comparisons were made with reference values. We identified 16 reports conducted among healthy and obese adults and individuals with chronic renal failure. Based on the weighted mean difference, we found that those studies using only multi-frequency BIA did not significantly overestimate the TBW compared with the reference values. Thus, among BIA techniques, multi-frequency BIA seems to be a more accurate method for estimating the TBW compartment for healthy and obese adults and for those with chronic renal failure.
British Journal of Nutrition, 2004
The present study was performed to determine how equilibrated fluctuations in hydration affected the validity of bioelectrical impedance analysis (BIA) for body composition assessment. Total body water (TBW) expansion was induced by a 4 d endurance trial and the subsequent water loss was obtained over the recovery period. Twelve healthy men exercised on a cycle and treadmill alternately for 5 h/d over 4 d at moderate intensity. TBW, fat mass (FM) and fat-free mass (FFM) were assessed 3 d before the trial (control), and on the first and eighth day of recovery (R1 and R8 respectively). TBW was evaluated by 2 H dilution (TBW 2H ) as a reference method and by BIA (TBW BIA ) at 100 kHz at the same time. TBW 2H increased significantly between the control day and R1 by 1·87 (SD 1·11) litres (P¼ 0·005) and TBW BIA by 1·38 (SD 1·56) litres (P¼0·009). Both values returned to the control level on R8. For each period, TBW 2H and TBW BIA did not differ significantly and were correlated (r 2 0·85, P¼0·0004 for the control day; r 2 0·63, P¼ 0·03 for R1; r 2 0·75, P¼0·02 for R8). Plasma Na concentration and osmolality did not differ between the control day, R1 and R8. FFM gain (1208 (SD 1983) g) and FM loss (21168 (SD 906) g) between the control day and R1 were followed by a FFM decrease (2624 (SD 1281) g) and a FM increase (860 (SD 1212) g) between R1 and R8. As expected, these FFM and FM changes were significantly correlated with TBW variations. The present results provide evidence that BIA may be a useful method for estimating TBW when fluid shifts are equilibrated and electrolyte concentrations are unchanged. However, it is not a valid technique for assessing FM and FFM under these conditions.
International journal of obesity and related metabolic disorders : journal of the International Association for the Study of Obesity, 1997
To validate the assessment of total body water (TBW) and extracellular water (ECW) by multi-frequency bioelectrical impedance. Twenty-five overweight but otherwise healthy subjects and 20 lean subjects. Cross-sectional. TBW and ECW were determined by dilution techniques. Prediction equations from the literature were used to calculate TBW and ECW from measured impedance at 100 and 50 kHz or 1 and 5 kHz, respectively. In 18 of the obese subjects, impedance was also measured with the electrodes placed at proximal sites. In lean and obese subjects, significant correlations were observed between the impedance index (H2/Z) at high frequencies with TBW (r = 0.90, P < 0.001 in lean and r = 0.80, P < 0.001 in obese subjects) and at low frequencies with ECW (r = 0.87, P < 0.001 and r = 0.77, P < 0.001 respectively). Proximal placement of electrodes slightly improved the correlation between the impedance index and TBW (from r = 0.83 to r = 0.90 at 50 kHz and from r = 0.85 to r = 0....
Comparison of Whole Body and Segmental Bioimpedance Methodologies for Estimating Total Body Water
Annals of the New York Academy of Sciences, 2006
We compared the whole body (WB) and segmental bioelectrical impedance analysis (BIA) methodologies in a group of healthy adults (n = 25). It has been suggested that the segmental methodology may overcome the difficulty in generating a single algorithm to predict total body water (TBW) in all groups whether healthy or not. We measured TBW, using D 2 O dilution, and WB and segmental BIA parameters. Cole-Cole analysis was used to determine the impedance at the characteristic frequency (Z c). The correlation between TBW (by D 2 O dilution) and segmental BIA measures (multiple regression, r = 0.90, p < 0.001, SEE = 3.1 L) was not significantly higher than the correlation between TBW (D 2 O dilution) and WB BIA measures (simple regression, r = 0.85, p < 0.001, SEE = 3.6 L). Others have observed this "lack of improvement" in a group of healthy subjects. The true value of the segmental BIA methodology may lie in applications involving groups with altered distributions of segmental and compartmental fluid.
Enhancing the accuracy of bio impedance analysis in assessing total body water
Objective: To assess the validity of a bio impedance analysis (BIA) instrument in predicting total body water (TBW), assessing the suitability of existing TBW equations and to develop a population specific impedance-based equation for the prediction of TBW in post pubertal adolescent girls using deuterium dilution as the reference method. Methods: The study population comprised of 15 to 19-year-old, Sri Lankan adolescent girls. Body composition was assessed by Fourier transform infrared spectrometry (FTIR) and bio impedance analysis (BIA). Available TBW equations for adolescents were assessed for validity of use on Sri Lankan adolescent girls. A new equation for TBW was derived and validated by linear regression analysis, against TBW derived by FTIR. Results: TBW obtained directly by the BIA instrument as well as TBW calculated using existing equations significantly (P<0.001) underestimated the actual TBW volume, obtained by the reference method (FTIR). Impedance index (height 2 / resistance; cm 2 /Ω) was a significant determinant of TBW in the new TBW equation derived for adolescent girls (TBW = 3.94 + 0.652* impedance index). Discussion: Direct use of the TBW value obtained by the BIA instrument as well as existing impedancebased equations for the prediction of TBW are unsuitable for this population. The new equation utilizing the impedance index, is appropriate for prediction of TBW in Sri Lankan post-pubertal adolescent girls and those of Asian origin, and can be utilized to assess other body composition parameters in this population.
Journal of Applied Physiology, 2006
Discrepancies in body fluid estimates between segmental bioimpedance spectroscopy (SBIS) and gold-standard methods may be due to the use of a uniform value of tissue resistivity to compute extracellular fluid volume (ECV) and intracellular fluid volume (ICV). Discrepancies may also arise from the exclusion of fluid volumes of hands, feet, neck, and head from measurements due to electrode positions. The aim of this study was to define the specific resistivity of various body segments and to use those values for computation of ECV and ICV along with a correction for unmeasured fluid volumes. Twenty-nine maintenance hemodialysis patients (16 men) underwent body composition analysis including whole body MRI, whole body potassium (40K) content, deuterium, and sodium bromide dilution, and segmental and wrist-to-ankle bioimpedance spectroscopy, all performed on the same day before a hemodialysis. Segment-specific resistivity was determined from segmental fat-free mass (FFM; by MRI), hydrat...