Optimization of RDM-UF for alfalfa wastewater treatment using RSM.

Rotating disk membrane (RDM) module with ultrafiltration (UF) was an effective alternative method to treat alfalfa wastewater and realize protein recovery and agricultural irrigation water production. A scientific investigation has been conducted to comprehend the effect of operation conditions (feed flow rate, shear rate, transmembrane pressure (TMP), and temperature) on alfalfa wastewater treatment with RDM-UF by central composite response surface methodology (CCRSM). First, the filtration behaviors of three types of UF membranes (PES20, UH030P, and PES50) were studied to select the optimized membrane (UH030P). Then, the effects and interactions of four operation conditions were studied and fitting models were established, while data on pollution reduction and protein recovery, membrane fouling behavior, and energy cost evaluation were collected. Furthermore, the optimized operation conditions calculated by CCRSM were Q = 60 L h-1, γ = 220 × 103 s-1, TMP = 5.61 bar, and T = 25 °C. In addition, the concentration test was conducted with these parameters. This work may contribute to the potential application of RDM for membrane wastewater treatment. Graphical abstract Schematic diagram of UF process for alfalfa wastewater treatment and resource recovery.

Indirect prediction of total body water content in healthy adult Beagles by single-frequency bioelectrical impedance analysis.

OBJECTIVE: To develop equations for prediction of total body water (TBW) content in unsedated dogs by combining impedance (resistance and reactance) and morphological variables and to compare the results of those equations with TBW content determined by deuterium dilution (TBW(d)). ANIMALS: 26 healthy adult Beagles. PROCEDURES: TBW content was determined directly by deuterium dilution and indirectly with equations developed from measurements obtained by use of a portable bioelectric impedance device and morphological variables including body length, height, weight, and thoracic and abdominal circumferences. RESULTS: Impedance and morphological data from 16 of the 26 dogs were used to determine coefficients for the following 2 equations: TBW(1) = -0.019 (BL(2)/R) + -0.199 (RC + AC) + 0.996 W + 0.081 H + 12.31; and TBW(2) = 0.048 (BL(2)/R) + -0.144 (RC + AC) + 0.777 W + 0.066 H + 0.031 X + 7.47, where AC is abdominal circumference, H is height, BL is body length, R is resistance, RC is rib cage circumference, W is body weight, and × is reactance. Results for TBW(1) (R(2)(1) = 0.843) and TBW(2) (R(2)(2) = 0.816) were highly correlated with the TBW(d). When the equations were validated with data from the remaining 10 dogs, the respective mean differences between TBW(d) and TBW(1) and TBW(2) were 0.17 and 0.11 L, which equated to a nonsignificant underestimation of TBW content by 2.4% and 1.6%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that impedance and morphological data can be used to accurately estimate TBW content in adult Beagles. This method of estimating TBW content is less expensive and easier to perform than is measurement of TBW(d), making it appealing for daily use in veterinary practice.

Factors influencing accuracy and reproducibility of body resistance measurements by foot-to-foot impedancemeters.

The electronics of a BodySignal V2 (Tefal, France) foot-to-foot impedancemeter (FFI) was modified to display the foot-to-foot resistance instead of body fat. This device was connected to electrodes of different sizes mounted on a podoscope permitting photographs of subjects feet soles and electrodes in order to calculate the contact area between feet and electrodes. The foot-to-foot resistance was found to decrease when the contact area of feet with current and voltage electrodes increased. It was also sensitive to feet displacement and a backward move of 5 cm increased the mean resistance by 37 Ω. The resistance reproducibility was tested by asking the subject to repeat measurements 10-times by stepping up and down from the podoscope. The mean SD of these tests was 0.88% of mean resistance, but it fell to 0.47% when feet position was guided and to 0.29% with transverse voltage electrodes. For good reproducibility, it is important that voltage electrodes be small and that the scale design facilitates a correct position of heels on these electrodes.

Accuracy of plantar electrodes compared with hand and foot electrodes in fat-free-mass measurement.

This paper investigates the measurement of fat-free mass (FFM) by bioimpedance using foot-to-foot impedancemeters (FFI) with plantar electrodes measuring the foot-to-foot resistance R34 and hand-to-foot medical impedancemeters. FFM measurements were compared with corresponding data using Dual X-ray absorptiometry (DXA). Equations giving FFM were established using linear multiple regression on DXA data in a first group of 170 subjects. For validation, these equations were used on a second group of 86 subjects, and FFM were compared with DXA data; no significant difference was observed. The same protocol was repeated, but using electrodes on the right hand and foot in standing position to measure the hand to-foot resistance R13. Mean differences with DXA were higher for R13 than for R34. Effect of electrode size and feet position on resistance was also investigated. R34 decreased when electrode area increased or if feet were moved forward. It decreased if feet were moved backward. A proper configuration of contact electrodes can improve measurement accuracy and reproducibility of FFI.

A comparison of bicarbonate kinetics and acid-base status in high flux hemodialysis and on-line post-dilution hemodiafiltration.

OBJECTIVES: To compare bicarbonate kinetics and acid base status in HD and HDF for the same patient; and to investigate the effect of patient physiologic parameters on these kinetics. METHODS: In order to monitor HCO3- kinetics during dialysis, acid-base parameters, pH, blood gases partial pressures, and HCO3- concentrations were recorded during 3 regular dialysis (HD) and 3 on-line post-dilution HDF sessions performed on 12 patients, using same dialysis fluid with a 38 mmol/l HCO3- concentration. HCO3- mass transfers through the hemodialyzers membranes and into the patients were continuously calculated during the sessions from HCO3- concentrations, together with HCO3-dialysance. The"apparent" HCO3-gain was calculated by integrating over time the instantaneous mass transfer from dialyzer and re-infusion fluid to the patient. A second method consisted in calculating the patient apparent bicarbonate space (ABS) and HCO3- mass (ABS times plasma concentration) at beginning and end of session. RESULTS: No significant differences were observed between acid base parameters at the end of HD and HDF sessions. In contrast to urea clearances, HCO3- dialysances decayed with time during sessions from 110 to 140 ml/min to about 40 ml/min after one hour. The net HCO3- gain was taken as the difference between final and initial HCO3-masses. This net gain was in average 63% of apparent gain in HD and 74% in HDF. CONCLUSIONS: Uremic acidosis was well corrected without risk of alkalosis. An unexpected result was the continuous decay of bicarbonate dialysance both in HD and HDF during runs.

Comparison of body fat-free masses calculated from hand-to-foot and foot-to-foot resistances with DXA measurements.

This article compares the determination of body fat-free-mass (FFM) by impedance, using either hand-to-foot resistance (R13) or foot-to-foot one (R34) from comparison with dual X-ray absorptiometry (DXA) measurements in a normal population. The first goal was to see if the foot-to-foot resistance used in body fat analysers provides less accurate information for body FFM than the hand-to-foot one used by medical impedance-meters. Another goal was to compare the prediction accuracy of six different regression equations of FFM for each sex and for each resistance relatively to DXA. The impedancemeter used in this study was a Tefal prototype with 4 plantar electrodes and 4 additional electrodes for the hands and providing hand-to-foot and foot-to-foot resistances. Coefficients of these correlations were determined by comparison with FFM measured by DXA in a 1st cohort of 170 healthy adults. For an independent validation, these equations were tested in a 2nd cohort of 86 adults who underwent the same impedance and DXA protocols, using Student's paired t-tests. The accuracy of FFM prediction increased generally with the number of physiologic parameters included in the regression, but none of our equations gave FFM predictions significantly different from DXA. FFM calculated from the foot-to-foot resistance were closer to DXA values than those calculated from hand-to-foot resistance, as their average P-value of comparison with DXA was higher at 0.695 against 0.387 for R13.

A two-stage ultrafiltration and nanofiltration process for recycling dairy wastewater.

A two-stage ultrafiltration and nanofiltration (UF/NF) process for the treatment of model dairy wastewater was investigated to recycle nutrients and water from the wastewater. Ultracel PLGC and NF270 membranes were found to be the most suitable for this purpose. In the first stage, protein and lipid were concentrated by the Ultracel PLGC UF membrane and could be used for algae cultivation to produce biodiesel and biofuel, and the permeate from UF was concentrated by the NF270 membrane in the second stage to obtain lactose in retentate and reusable water in permeate, while the NF retentate could be recycled for anaerobic digestion to produce biogas. With this approach, most of dairy wastewater could be recycled to produce reusable water and substrates for bioenergy production. Compared with the single NF process, this two-stage UF/NF process had a higher efficiency and less membrane fouling.

A comparison between two methods for measuring limb resistances with wrist and ankle electrodes.

Segmental measurements of limb resistances permit to evaluate the regional distribution of fat-free-mass (FFM). As shown by Organ et al. (J Appl Physiol 1994;77:98-112) "virtual" limb resistances can be measured with only peripheral electrodes at ankle and wrist, which is faster and does not require undressing. This paper presents a different method for obtaining "virtual" limb resistances from peripheral electrodes and compares it with that of Organ et al. and with segmental measurements using same protocol. It is found that virtual arm resistances of both methods were overestimated as compared to segmental values, by 6.8% in men and 5.8% in women for our method and by 7.4% and 8% for Organ et al. one. Virtual leg resistances were found, for both methods, to be slightly lower than segmental leg resistances measured with proximal waist electrodes, which were a little overestimated. But after correcting this overestimation using Organ et al. data, we evaluated the overestimation of virtual leg resistances to be 2.3% in men and 2.8% in women by our method versus 4.4% and 5.9%, respectively, for Organ et al. one. An important finding was the strong correlation between virtual resistances of both methods and segmental ones, as their ratio had a small standard deviation between 0.019 and 0.024 for arms and legs. Thus, the overestimation of limb resistance is automatically corrected when FFM is determined by an equation calibrated with DXA segmental measurements.

Separation of water from metal working emulsions by ultrafiltration using vibratory membranes.

In this paper, we investigate the application of a vibratory shear-enhanced filtration system (VSEP) to separation of water from oil-in-water emulsions. The VSEP module consists in an annular membrane of 500 cm(2) area which oscillates azimuthally in its own plane with an amplitude depending upon frequency. Polyethersulfone (PES) membranes of 50 and 20 kDa were used. Test fluids consisted of oil-in-water emulsion at an oil concentration of 4% prepared from a concentrated cutting fluid. The critical flux for stable operation was investigated by increasing the permeate flux in steps while monitoring the transmembrane pressure (TMP). With a 50 kDa membrane the flux increased nonlinearly with TMP and reached 250 L h(-1)m(-2) at a TMP of 1500 kPa while permeate turbidity decayed from 1.8 to 0.9 NTU above 600 kPa from an initial emulsion turbidity of 21,900 NTU. With the 20 kDa membrane, the flux increased linearly with TMP until 1600 kPa, but the oil concentration in permeate became negligible (turbidity near zero NTU). Concentration tests showed that the flux decreased linearly with ln(VRR) where VRR is the volume reduction ratio while permeate turbidity increased exponentially to 25NTU above a VRR of 4. This work confirms the high performance of the VSEP for oil separation from water in metal working emulsions.

In vitro tests and modelization of bicarbonate kinetics and mass transfers during online hemodiafiltration.

This paper proposes an in vitro hemodiafiltration (HDF) model in which the patient is represented by a 2 L bag of fresh heparinized bovine blood circulated by a 4008H monitor through a 0.6 m2 hemodialyzer to investigate kinetics of bicarbonate (HCO,) during online post-dilution HDF. Five tests were carried out, with three ultrafiltration rates, zero (HD test), 30 and 50 ml/min. Blood gases, pH, HCO3, hematocrit and electrolytes were measured with an ABL 77 (Radiometer) blood gas analyzer, and HCO3- was simultaneously measured with a biochemistry analyzer. The variation over time of plasma HCO3- concentrations was also calculated using mass conservation and the model of Legallais et al (JMS 168, 2000, 3-15). Agreement between theoretical and measured concentrations was good during the first 25 minutes of each test, corresponding to the time necessary to dialyze the blood. In hemodialysis (HD), there was an HCO3- mass transfer into blood through the membrane due to diffusion which vanished after 40 minutes, while in HDF tests, blood lost HCO3 due to ultrafiltration after 10 minutes. With reinjection, the net HCO3- mass flow rate to the "patient" decayed, from 1.8 mmol/min at t = 0 to zero at the end of the test (t = 60 min), and was higher in HD than in HDF "Patient" dialysance, taking into account reinjection, was positive in all tests, and decayed from about 110 ml/ min to 40 m/min at the end of dialysis. These data confirmed that online HDF automatically corrects acidosis without creating alkalosis when HCO3- dialysate concentration is around 30 mmol/L.

Measurements of body composition in limbs and trunk using a eight contact electrodes impedancemeter.

Regional body composition measurements may be achieved in a single operation with impedancemeters equipped with four plantar and four hand electrodes. By measuring sequentially the resistances of five current lines connecting the hands and feet and solving a system of five linear equations, it is possible to calculate the resistances of each limb and the trunk. The impedancemeter used in this study was a prototype with four plantar electrodes and four additional contact electrodes for the hands. Its electronic hardware was identical to that of a Tefal commercial foot-to-foot impedancemeter (FFI). The Tefal FFI was used for measuring weight, whole body fat-free mass (FFM) and fat tissue mass (FM). Impedance and DXA measurements were taken sequentially on a 1st cohort of 170 healthy adults, aged from 19 to 75 years, to obtain equations relating appendicular FFM measured by DXA to their resistances, subject weight and height. For appendicular FM, correlations of the body FM measured by the FFI, age and BMI were used. Trunk FFM was obtained by subtracting appendicular FFM from FFM of trunk+limbs obtained by the same method as that for appendicular FFM. For an independent validation, these equations were tested on a 2nd cohort of 87 subjects (18-74 years) who underwent the same impedance and DXA protocol. Comparison of FFM and FM by impedance and by DXA in the limbs and the trunk using paired Student's t-tests, showed that they were not significantly different both in the 1st and validation cohorts. Mean FFM differences between impedance and DXA were -0.018+/-0.48 kg for right arms and -0.039+/-0.85kg for right legs of men in validation cohort. This work confirms that eight contact electrodes bioimpedance can measure appendicular and trunk FFM and FM in good agreement with DXA, at least in a healthy population.

Body composition determination by bioimpedance: an update.

PURPOSE OF REVIEW: To review various methods for measuring body composition by bioimpedance and their limitations, as well as available impedance meters, including body fat analyzers for home use. RECENT FINDINGS: Bioimpedance spectroscopy, which requires multifrequency impedance meters, is preferable for fluid volume measurements, especially extracellular fluid, whereas bioimpedance analysis at 50 kHz is more widely used for measuring fat-free mass. A method for using bioimpedance spectroscopy equations with 50 kHz impedance meters has been recently proposed and successfully tested. Low cost foot-to-foot impedance meters (body fat analyzers) with plantar electrodes on a body scale, that are easy and fast to use, have been compared with medical impedance meters and with dual X-ray absorptiometry measurements and found reasonably accurate, except for individuals with very low or high BMI. SUMMARY: Body composition by bioimpedance is gaining acceptance in nutrition, hemodialysis, gerontology and sports medicine. Body fat analyzers that have been validated by comparison with dual x-ray absorptiometry could be useful to general practitioners, nutritionists and cardiologists.

Extracellular volume measurements using bioimpedance spectroscopy-Hanai method and wrist-ankle resistance at 50 kHz.

A method for extrapolating the extracellular water (ECW) resistance from wrist-ankle resistance at 50 kHz (R (50)) is proposed in this paper, in order to enable 50 kHz impedancemeters to use the BIS-Hanai equation for determination of ECW. Values of R (50) and the ECW resistance extrapolated at zero frequency R (e) were measured in a first group of 57 healthy volunteers, using a Xitron 4200 multifrequency impedancemeter and mean values (b) of the ratio R (50)/R (e) in men and women were used to determine individual values of R (e50), the ECW resistance extrapolated from R (50), which were substituted to R (e) in the BIS-Hanai equation. For validation, the method was compared against ECW measured with the Xitron (V (ex)) in a second group of 31 healthy volunteers, using values of b of first group. Values of R (e50) in this second group were found to be not significantly different from corresponding values of R (e) with p-values of Student test of 0.346 for men and 0.300 for women. ECW volumes (V (e50)) calculated from R (e50) were also found not significantly different from those of the Xitron with Student paired test p values of 0.277 in men and 0.393 in women. Our method gave a better agreement with V (ex) than two bioimpedance analysis methods from the literature, especially in women. It was also tested on a 50 kHz single frequency impedancemeter (BodyExplorer, Juwell Medical) on a third group of 21 subjects and gave ECW volumes not significantly from those of the Xitron with p = 0.531 for men and 0.096 for women.

Body fluid volumes measurements by impedance: A review of bioimpedance spectroscopy (BIS) and bioimpedance analysis (BIA) methods.

This paper reviews various bioimpedance methods permitting to measure non-invasively, extracellular, intracellular and total body water (TBW) and compares BIA methods based on empirical equations of the wrist-ankle resistance or impedance at 50 kHz, height and weight with BIS methods which rely on an electrical model of tissues and resistances measured at zero and infinite frequencies. In order to compare these methods, impedance measurements were made with a multifrequency Xitron 4200 impedance meter on 57 healthy subjects which had undergone simultaneously a Dual X-ray absorptiometry examination (DXA), in order to estimate their TBW from their fat-free-mass. Extracellular (ECW) and TBW volumes were calculated for these subjects using the original BIS method and modifications of Matthie[Matthie JR. Second generation mixture theory equation for estimating intracellular water using bioimpedance spectroscopy. J Appl Physiol 2005;99:780-1], Jaffrin et al. [Jaffrin MY, Fenech M, Moreno MV, Kieffer R. Total body water measurement by a modification of the bioimpédance spectroscopy method. Med Bio Eng Comput 2006;44:873-82], Moissl et al. [Moissl UM, Wabel P, Chamney PW, Bosaeus I, Levin NW, et al. Body fluid volume determination via body composition spectroscopy in health and disease. Physiol Meas 2006;27:921-33] and their TBW resistivities were compared and discussed. ECW volumes were calculated by BIA methods of Sergi et al. [Sergi G, Bussolotto M, Perini P, Calliari I, et al. Accuracy of bioelectrical bioimpedance analysis for the assessment of extracellular space in healthy subjects and in fluid retention states. Ann Nutr Metab 1994;38(3):158-65] and Hannan et al. [Hannan WJ, Cowen SJ, Fearon KC, Plester CE, Falconer JS, Richardson RA. Evaluation of multi-frequency bio-impedance analysis for the assessment of extracellular and total body water in surgical patients. Clin Sci 1994;86:479-85] and TBW volumes by BIA methods of Kushner and Schoeller [Kushner RF, Schoeller DA. Estimation of total body water by bioelectrical impedance analysis. Am J Clin Nutr 1986;44(3):417-24], Lukaski et al. [Lukaski HC, Bolonchuk WW. Estimation of body fluid volumes using tetrapolar bioelectrical impedance measurements. Aviat Space Environ Med 1988;59:1163-9], Hannan et al. [Hannan WJ, Cowen SJ, Fearon KC, Plester CE, Falconer JS, Richardson RA. Evaluation of multi-frequency bio-impedance analysis for the assessment of extracellular and total body water in surgical patients. Clinical Science 1994;86:479-85], Deurenberg et al. [Deurenberg P, van der Koy K, Leenen R, Westrate JA, Seidell JC. Sex and age specific prediction formulas for estimating body composition from bioelectric impedance: a cross validation study. Int J Obesity 1991;15:17-25] These volumes were compared against those given by BIS method and, in the case of TBW, with those by DXA. For ECW, a good agreement was found between various BIS methods and that of Sergi while Hannan's values were higher. Both Matthie's and Moissl's methods gave mean TBW resistivities and volumes lower than those of Jaffrin's and DXA methods. Kushner et al. method gave values of TBW not significantly different from those of Jaffrin et al. and DXA, as Hannan's method in men, but Lukaski and Deurenberg methods led to an underestimation.

Measurements of total body water with a foot-to-foot impedancemeter.

The objective was to set-up a method for measuring total body water volumes (TBW) using a Tefal foot-to-foot impedancemeter (FFI) by comparison with a multifrequency medical impedancemeter and to validate this method against deuterium dilution data. The investigation was carried out in 57 Caucasian adult subjects. Impedancemeters were a Tefal Bodymaster Vision (foot-to-foot) featuring a square wave signal and a Xitron Hydra 4200 (5-1000 kHz) using BIS method. TBW was measured by the Xitron using a new method that we have developed which applies the BIS method directly to extra and intracellular fluids combined. Although the high frequency impedance of the FFI (R(hf)) was higher than the Xitron infinite frequency resistance and corresponded to a frequency around 100 kHz, TBW differences between the FFI and Xitron were not significant, 0.17+/-2.17 L for men (P=0.694) and 0.04+/-1.88 L for women (P=0.902). Then, our method was tested on another Caucasian population in which R(hf) had been measured with the same FFI, together with TBW measurements by deuterium dilution. TBW differences between the FFI and dilution were -0.38+/-2.27 L for men (P=0.237) and -0.72+/-2.37 L for women (P=0.06). Our method permits, at least in a Caucasian healthy population, to measure TBW using this FFI with the same accuracy as a whole body multifrequency medical impedancemeter, and the measurement, made in upright position, is much quicker.

Assessment of body composition in adolescent subjects with anorexia nervosa by bioimpedance.

Our main goal was to test various impedance methods for measuring body composition in adolescents with anorexia nervosa (AN) during refeeding therapy. A specific objective was to compare the information provided by a foot-to-foot impedancemeter (FFI) with that supplied by a medical multifrequency impedancemeter and by dual X-ray absorptiometry (DXA). We have monitored 13 young AN subjects and 17 healthy controls of a similar age group using a Xitron 4200 multifrequency impedancemeter measuring extracellular (ECW) and total body water (TBW) volumes and a Tefal Bodymaster FFI measuring weight (W), fat-free-mass (FFM) and body fat mass (FM). This Tefal device has been modified to measure in addition ECW and TBW resistances permitting to calculate ECW and TBW volumes using appropriate algorithms. In addition FFM and FM were measured by DXA on AN subjects. FFM measured by the FFI and the Xitron in AN subjects were found to be respectively 7.8% and 4.5% lower than FFM measured by DXA. TBW measured by FFI was not significantly different from that measured by Xitron in AN subjects and in controls. ECW measured by the FFI was not significantly different from that measured by Xitron in controls, but was in AN subjects. The body cell mass to (height)2 ratio was found to be significantly different between AN subjects and controls. The modified FFI was found to be simpler and quicker to use than the Xitron, while giving similar information.

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.

Evaluation of a foot-to-foot impedance meter measuring extracellular fluid volume in addition to fat-free mass and fat tissue mass.

OBJECTIVES: The first objective was to compare the accuracy of a foot-to-foot impedance meter with a multifrequency bioimpedance for measurements of fat-free mass (FFM) and fat mass (FM) using dual energy X-ray absorptiometry (DXA) as reference. The second objective was to validate measurements of extracellular water resistance and volume by the foot-to-foot impedance meter, using multifrequency bioimpedance as reference. METHODS: This investigation was carried out in 60 volunteers 18 to 71 y of age. Impedance meters were a Tefal Bodymaster Vision (foot-to-foot) that featured a square wave signal and a Xitron Hydra 4200 (5 to 1000 kHz) by using the bioimpedance spectroscopic method. RESULTS: Bland-Altman tests showed that FFM differences between Tefal and DXA data were 1.98 +/- 3.09 kg in men and -0.08+/-2.98 kg in women. Total body water was measured by the Xitron, and FFM as measured with the Xitron was calculated as total body water divided by 0.732. Mean differences between Xitron-measured and DXA-measured FFM were 2.37+/-3.03 kg for men and 2.84+/-2.40 kg for women, indicating a systematic underestimation by the Xitron of intracellular volume. Extracellular water resistances measured by Tefal were in good agreement with those measured by Xitron with electrodes pasted under the subject's feet (mean difference 8.5+/-31 Omega). Extracellular water volumes were calculated from Tefal-measured extracellular water resistances by using a modified bioimpedance spectroscopic method and differed from those measured with Xitron by-0.03+/-0.66 L. CONCLUSION: Limits of agreement with DXA-measured FFM produced by the foot-to-foot impedance meter tested are too large for clinical measurements in individuals, but they are sufficient to assess FFM in groups of subjects and for home use. Our prototype was also capable of estimating extracellular water volume with a similar accuracy as multifrequency bioimpedance in normal subjects.

Extracellular and intracellular volume variations during postural change measured by segmental and wrist-ankle bioimpedance spectroscopy.

Extracellular (ECW) and intracellular (ICW) volumes were measured using both segmental and wrist-ankle (W-A) bioimpedance spectroscopy (5-1000 kHz) in 15 healthy subjects (7 men, 8 women). In the 1st protocol, the subject, after sitting for 30 min, laid supine for at least 30 min. In the second protocol, the subject, who had been supine for 1 hr, sat up in bed for 10 min and returned to supine position for another hour. Segmental ECW and ICW resistances of legs, arms and trunk were measured by placing four voltage electrodes on wrist, shoulder, top of thigh and ankle and using Hanai's conductivity theory. W-A resistances were found to be very close to the sum of segmental resistances. When switching from sitting to supine (protocol 1), the mean ECW leg resistance increased by 18.2%, that of arm and W-A by 12.4%. Trunk resistance also increased but not significantly by 4.8%. Corresponding increases in ICW resistance were smaller for legs (3.7%) and arm (-0.7%) but larger for the trunk (21.4%). Total body ECW volumes from segmental measurements were in good agreement with W-A and Watson anthropomorphic correlation. The decrease in total ECW volume (when supine) calculated from segmental resistances was at 0.79 l less than the W-A one (1.12 l). Total ICW volume reductions were 3.4% (segmental) and 3.8% (W-A). Tests of protocol 2 confirmed that resistance and fluid volume values were not affected by a temporary position change.