Prospective nutritional surveillance using bioelectrical impedance in chronic kidney disease patients

Application of Bioelectrical Impedance Analysis in Nutritional Management of Patients with Chronic Kidney Disease

Body composition measurement plays an important role in the nutritional diagnosis and treatment of diseases. In the past 30 years, the detection of body composition based on bioelectrical impedance analysis (BIA) has been widely used and explored in a variety of diseases. With the development of technology, bioelectrical impedance analysis has gradually developed from single-frequency BIA (SF-BIA) to multi-frequency BIA (multi-frequency BIA, MF-BIA) and over a range of frequencies (bioimpedance spectroscopy, BIS). As the clinical significance of nutrition management in chronic kidney disease has gradually become prominent, body composition measurement by BIA has been favored by nephrologists and nutritionists. In the past 20 years, there have been many studies on the application of BIA in patients with CKD. This review describes and summarizes the latest research results of BIA in nutritional management of patients with CKD including pre-dialysis, hemodialysis, peritoneal dialysis and kidney transplantation, in order to provide reference for the application and research of BIA in nutritional management of chronic kidney disease in the future.

Bioelectrical Impedance Analysis-Derived Phase Angle Predicts Protein-Energy Wasting in Maintenance Hemodialysis Patients

OBJECTIVE(S)

To explore the validity of using bioelectrical impedance analysis (BIA)-derived 50 kHz phase angle (PhA) in predicting protein-energy wasting (PEW) in Chinese maintenance hemodialysis (MHD) patients.

DESIGN AND METHODS

The design was a cross-sectional study. A total of 173 of MHD patients and 173 healthy adults were enrolled in the study. The prevalence of PEW in patients was performed by the International Society of Renal Nutrition and Metabolism criteria. The PhA, body cell mass, fat mass, body fat percentage, fat-free mass, and extracellular water/total body water were measured by InBody S10 body composition analyzer. The biochemical indices and anthropometric measurements were assessed using the way published elsewhere. The PhA, other values of BIA and its relationship with age, visceral protein, anthropometric measurements of the MHD patients were compared with the healthy group. The independent variables for predicting PEW and its cutoff values were explored using logistic regression model and receiver operating characteristic curve analysis, respectively.

RESULTS

The MHD patients' PhA value was significantly lower than the healthy group (4.89°± 1.19 vs. 6.32°± 2.23, P < .01). A total of 34.1% MHD patients with PEW had significantly lower PhA values compared with well-nourished patients (P < .05). The PhA decreased more significantly with age in MHD (r = -0.35, P < .001), compared with controls (r = -0.26, P < .001). The PhA values were positively associated with nutritional indices related to serum albumin, prealbumin, fat-free mass, and mid-arm muscle circumference. PhA values were not associated significantly with fat mass and body fat percentage (P > .05). Multivariate logistic regression analysis showed that PhA and body mass index were independent predictors of PEW, but the PhA was the stronger predictor (odds ratio = 4.48, P < .05). Receiver operating characteristic curve analysis suggested that the optimal PhA cutoff value to predict PEW was 4.6°.

CONCLUSIONS

BIA-derived PhA appears to be a useful bioelectrical marker for predicting PEW in Chinese hemodialysis patients with a cutoff value of 4.6°.

Influence of dietary protein intake on body composition in chronic kidney disease patients in stages 3-5: A cross-sectional study

INTRODUCTION

A controlled protein intake has shown beneficial effects to preserve renal function and nutritional status in chronic kidney disease (CKD) patients. This study aimed to analyze usual dietary protein intake and its potential contribution to body composition in CKD patients in stages 3-5.

METHOD

Cross-sectional study in 134 CKD patients in stages 3-5 (mean e-GFR: 19.4±8.7ml/min/1.73m²; males 68.7% and primary CKD etiology was diabetes mellitus, 35.8%). Demographic, clinical and nutritional parameters were evaluated. Normalized protein nitrogen appearance (nPNA), was used as a surrogate marker of dietary protein intake. The sample was classified into three nPNA groups (G_n): G₁: <0.8g/kg/day; G₂: 0.8-1g/kg/day and, G₃: ≥1g/kg/day. Assessment of nutritional status using the malnutrition-inflammation score (MIS), anthropometric measures and laboratory parameters. Analysis of body composition and hydration status by bioelectrical impedance analysis (BIVA-101-RJL system). Statistical analysis by SPSS v.20.

RESULTS

Overall mean nPNA values were 0.91±0.23g of protein/kg BW/day and only 32.1% had a dietary protein intake <0.8g of protein/kg BW/day. Most of the CKD patients (65.5%) were in stages 4 or 5. Prevalence of protein-energy-wasting (PEW) syndrome measured by MIS was 15%. By analyzing differences between nPNA groups, body weight (BW), BMI and triceps-skinfold (TSF) thickness were significantly higher in the group with nPNA ≥1g/kg BW/day (G₃), whereas a significant inverse relationship was found with the percentages of body cell mass (BCM%), fat-free mass (FFM%), muscle mass (MM%) and phase angle (PA) in the group with the lowest nPNA (G₁). Analysis of gender among subjects showed significant differences with BW, FFM%, TSF and mid-arm muscle circumference (MAMC%). Linear regression analysis showed that resistance, BCM%, MM%, and serum albumin were significant predictors of nPNA as a surrogate marker of daily protein intake (R=0.51; R²=0.29; R² adjusted=0.23; p<0.001).

CONCLUSION

Controlled protein intake is one of the cornerstones of treatment in CKD patients. A low protein intake in patients with CKD stages 3 and 4-5 was associated with loss of muscle mass in the advanced-CKD unit. The loss of muscle mass appears as an early indicator of nutritional comprised. Factors such, elderly age and loss of eGFR, showed lower protein intake and were associated with muscle loss, especially in women. Further longitudinal studies are required to evaluate the contribution of different protein intakes to uremic symptoms, nutritional status, body composition and CKD progression.

Body Composition Analysis by Using Bioelectrical Impedance in a Young Healthy Chinese Population: Methodological Considerations

OBJECTIVE

To develop a new bioelectrical impedance analysis (BIA) model for analyzing body composition by using isotope dilution, magnetic resonance imaging (MRI), and dual-energy X-ray absorptiometry (DEXA) as the reference methods in young healthy Chinese populations.

METHODS

Thirty healthy participants were enrolled. Their body composition was analyzed using BIA and 3 reference methods. We established a model that uniformed data from 3 references methods (isotope, MRI, and DEXA) into 1 formula. This model was further validated with 209 participants.

RESULTS

The following BIA body composition adjustment model was developed: [Formula: see text], where X represents the impedance index; when K = 1, 2, and 3, Y represents total body water, fat mass, and bone mass, respectively. The prediction accuracy of this formula was 93.3%. By incorporating the data matrix, the protein mass was calculated using BIA: [Formula: see text]. In the verification part of this study, the lean body mass measured using DEXA and BIA was 43.02 ± 8.34 kg and 45.85 ± 8.81 kg, respectively. Analysis indicated that the model fit was extremely favorable ( R² = .9997, P < .001).

CONCLUSIONS

The accuracy of BIA measurement on body composition and protein mass is significantly improved by our work.

Preoperative risk factors of malnutrition for cardiac surgery patients

BACKGROUND

Malnutrition (MN) is prevalent in cardiac surgery, but there are no specific preoperative risk factors of MN. The aim of this study is to assess the clinically relevant risk factors of MN for cardiac surgery patients.

MATERIALS AND METHODS

The nutritional state of the patients was evaluated one day prior to surgery using a bioelectrical impedance analysis phase angle (PA). Two groups of patients were generated according to low PA: malnourished and well nourished. Risk factors of MN were divided into three clinically relevant groups: psychosocial and lifestyle factors, laboratory findings and disease-associated factors. Variables in each different group were entered into separate multivariate logistic regression models.

RESULTS

A total of 712 patients were included in the study. The majority of them were 65-year old men after a CABG procedure. Low PA was present in 22.9% (163) of patients. The analysis of disease-related factors of MN revealed the importance of heart functions (NYHA IV class OR: 3.073, CI95%: 1.416-6.668, p = 0.007), valve pathology (OR: 1.825, CI95%: 1.182-2.819, p = 0.007), renal insufficiency (OR: 4.091, CI95%: 1.995-8.389, p < 0.001) and body mass index (OR: 0.928, CI95%: 0.890-0.968, p < 0.001). Laboratory values related to MN were levels of haemoglobin (OR: 0.967, CI95%: 0.951-0.983, p < 0.001) and C-reactive protein (OR: 1.015, CI95%: 1.002-1.028, p = 0.0279). The lifestyle variables that qualified as risk factors concerned the intake of food (OR: 3.030, CI95%: 1.353-6.757, p = 0.007) and mobility (OR: 2.770, CI95%: 1.067-7.194, p = 0.036).

CONCLUSIONS

MN risk factors comprise three different clinical groups: psychosocial and lifestyle factors, laboratory findings and disease-associated factors. The patients who are most likely to be malnourished are those with valve pathology, severe imparted heart function, insufficient renal function and high inflammatory markers. Also these patients have decreased mobility and food intake.

Body Fat Analysis in Predialysis Chronic Kidney Disease: Multifrequency Bioimpedance Assay and Anthropometry Compared With Dual-Energy X-Ray Absorptiometry

OBJECTIVES

Body composition analysis is required for accurate assessment of nutritional status in patients with predialysis chronic kidney disease (CKD). The reference method for assessing body fat is dual-energy X-ray absorptiometry (DXA), but it is relatively expensive and often not available for widespread clinical use. There is only limited data on the utility of less expensive and easily available alternatives such as multifrequency bioimpedance assay (BIA) and skinfold thickness (SFT) measurements for assessing body fat in predialysis CKD. The study intends to assess the utility of BIA and SFT in measuring body fat compared to the reference method DXA in subjects with predialysis CKD.

METHODS

Body composition analysis was done in 50 subjects with predialysis CKD using multifrequency BIA, SFT, and DXA. The agreement between the body fat percentages measured by reference method DXA and BIA/SFT was assessed by paired t-test, intraclass correlation coefficients (ICCs), regression, and Bland-Altman plots.

RESULTS

Percentage of body fat measured by BIA was higher compared to the measurements by DXA, but the difference was not significant (30.44 ± 9.34 vs. 28.62 ± 9.00; P = .071). The ICC between DXA and BIA was 0.822 (confidence interval: 0.688, 0.899; P = .000). The mean values of body fat percentages measured by anthropometry (SFT) was considerably lower when compared to DXA (23.62 ± 8.18 vs. 28.62 ± 9.00; P = .000). The ICC between DXA and SFT was .851 (confidence interval: 0.739, 0.915; P = .000). Bland-Altman plots showed that BIA overestimated body fat by a mean of 1.8% (standard deviation, 6.98), whereas SFT underestimated body fat by 5% (standard deviation, 4.01). Regression plots showed a better agreement between SFT and DXA (R(2) = .79) than BIA (R(2) = .50). Overall, SFT showed better agreement with the DXA. Body mass index (BMI) showed a moderate positive correlation with body fat measured by DXA whereas serum albumin failed to show good correlation.

CONCLUSIONS

SFT showed relatively better agreement with the reference method DXA, compared to BIA. SFT can be used as a tool for assessing nutritional status in predialysis patients with CKD.

Correlation of bioelectrical impedance analysis phase angle with changes in oxidative stress on end-stage renal disease patients, before, during, and after dialysis

Chronic kidney disease is a condition that promotes oxidative stress. There are conflicting evidence about the role of hemodialysis on oxidative stress, that are mostly related with the various types of membrane materials used, the quality and type of dialysate, the method used, etc. The phase angle (PhA), which is determined with bioelectrical impedance analysis (BIA), measures the functionality of cell membranes. In this study, the correlation of the PhA with parameters of oxidative stress is attempted for the first time. We evaluated parameters of oxidative status as total antioxidant capacity (TAC) in erythrocytes (RBCs) and plasma of patients with ESRD undergoing hemodialysis with low flux synthetic polysulfone membranes. Measurements were recorded from 30 patients (16 men and 14 women) aged 64 ± 14 years before, during, and after dialysis, and in 15 healthy volunteers aged 56 ± 12 years The PhA was obtained by BIA. The plasma TAC increased significantly (41%, p < 0.05). Intracellular TAC noted a non-significant increase. Total antioxidant capacity of the patients before and after hemodialysis was significantly lower from the healthy volunteers (p < 0.05) showing that ESRD patients are at the state of increased oxidative stress. The PhA increased in significantly positive correlation with plasma TAC at the end of hemodialysis. The process of hemodialysis with biocompatible synthetic membranes and bicarbonate dialysate improved plasma TAC. The positive correlation of PhA with extracellular TAC could evolve to a method of oxidative stress estimation by BIA but further research is needed.

Depression, quality of life, and body composition in patients with end-stage renal disease: a cohort study

Objective:

To prospectively evaluate depressive symptoms, nutritional status, and quality of life (QoL) and search for possible associations in patients with end-stage renal disease undergoing hemodialysis.

Methods:

A cohort study of 104 adult patients with end-stage renal disease undergoing hemodialysis was conducted. Anthropometric, clinical, and biochemical variables were evaluated after a midweek hemodialysis session. The participants’ body composition was assessed by direct segmental multi-frequency bioimpedance analysis. The WHOQOL-Bref questionnaire was used to evaluate QoL. Participants were separated into two groups - depressive symptoms and no depressive symptoms - at inclusion and evaluated annually for 2 years thereafter using the Beck Depression Inventory. Survival analysis used the Kaplan-Meier method and Cox regression analysis for the goodness of fit of associated factors. All-cause mortality was the outcome of interest.

Results:

Participants’ mean age was 55.3±15.6 years, 60% were male, and the median time on hemodialysis was 17.5 (8.0-36.8) months. Thirty-two patients had depressive symptoms and a significantly lower QoL compared with the 72 patients in the no depressive symptoms group. The fitted outcome model showed that lean body mass had a protective effect against all-cause mortality (hazard ratio [HR] = 0.89; 95%CI 0.80-0.99; p = 0.038).

Conclusion:

Depressive symptoms were highly prevalent in the cohort, and correlated with the physical and psychological components of the QoL life questionnaire, as well as with C-reactive protein and phosphorus levels. Lean body mass was protective for the assessed outcome.

DETERMINATION OF VOLUME OVERLOAD BY BIOELECTRICAL IMPEDANCE ANALYSIS AND NT-PROBNP IN DIABETIC PRE-DIALYSIS PATIENTS

Introduction

Diabetic chronic kidney disease has more fatal clinical progresses and this situation can be related to volume overload, which is seen more commonly in diabetic chronic kidney disease patients than in non-diabetic chronic kidney disease patients. Therefore, we examined the effect of diabetes mellitus on volume overload in newly diagnosed stage 5 chronic kidney disease patients whose volume overloads were not showing signs of improvement from renal replacement therapy.

Method

One hundred and five patients (46 diabetic, 59 non-diabetic) with end-stage chronic kidney disease, who had glomerular filtration rate (GFR) under 15 mL/min for at least three months were enrolled in this prospective study. We determined the body volume overload and configuration using a bioimpedance device. NT-proBNP levels were recorded.

Results

There was a statistically significant difference between diabetic and non-diabetic groups according to overhydration (OH, p=0.003), extracellular water (ECW, p=0.045), intracellular water (ICW, p<0.001) and OH/ECW (p=0.003). In addition, there was a statistically significant difference between groups in terms of N-terminal Pro-brain Natriuretic Peptide (NT-proBNP levels, p=0.008).

Discussion

We compared diabetic and non-diabetic end-stage chronic kidney disease patients who were not in renal replacement therapy yet. We found more volume overload and extracellular fluid volume in the diabetic group.

Impact of 14-day bed rest on serum adipokines and low-grade inflammation in younger and older adults

Ageing and inactivity both contribute to systemic inflammation, but the effects of inactivity on inflammation in healthy elderly individuals have not been elucidated. We hypothesised that 14-day bed rest could affect the pro- and anti-inflammatory markers in young subjects differently than in older adults. A short-term 14-day horizontal bed rest study (BR14) has been used as a model of inactivity in two groups of healthy male volunteers: 7 aged 18-30 years (young) and 16 aged 55-65 years (older adults). The effects of inactivity on inflammation were compared. Key low-grade inflammation mediators, tumour necrosis factor α (TNF-α), interleukin-6 (IL-6), visfatin, resistin, and anti-inflammatory adiponectin were measured in fasting serum samples, collected at baseline (BDC) and post BR14. Young responded to BR14 by increasing serum visfatin and resistin while older adults responded to BR14 by increasing IL-6 and TNF-α. In addition, serum adiponectin increased in all participants. Data from correlation analysis demonstrated positive association between Δ serum visfatin and Δ IL-6 in both groups, while Δ serum adiponectin was negatively associated with Δ TNF-α in young and positively associated with Δ resistin in the older adults. As little as 14 days of complete physical inactivity (BR14) negatively affected markers of low-grade inflammation in both groups, but the inflammation after BR14 was more pronounced in older adults. The effect of BR14 on IL-6 and resistin differed between young and older adults. Inflammatory responses to BR14 in older adults differed from those reported in the literature for obese or subjects in pathological states, suggesting potentially different mechanisms between inactivity- and obesity-induced inflammations.

The first year on haemodialysis: a critical transition

The first year following the start of haemodialysis (HD) is associated with increased mortality, especially during the first 90–120 days after the start of dialysis. Whereas the start of dialysis has important effects on the internal environment of the patient, there are relatively few studies assessing changes in phenotype and underlying mechanisms during the transition period following pre-dialysis to dialysis care, although more insight into these parameters is of importance in unravelling the causes of this increased early mortality. In this review, changes in cardiovascular, nutritional and inflammatory parameters during the first year of HD, as well as changes in physical and functional performance are discussed. Treatment-related factors that might contribute to these changes include vascular access and pre-dialysis care, dialysate prescription and the insufficient correction of the internal environment by current dialysis techniques. Patient-related factors include the ongoing loss of residual renal function and the progression of comorbid disease. Identifying phenotypic changes and targeting risk patterns might improve outcome during the transition period. Given the scarcity of data on this subject, more research is needed.

Evaluation of volume overload by bioelectrical impedance analysis, NT-proBNP and inferior vena cava diameter in patients with stage 3&4 and 5 chronic kidney disease

BACKGROUND

Determination of fluid overload is important in chronic kidney disease. Early diagnosis and treatment of volume overload may decrease morbidity and mortality. We aimed to determine body composition by using bioelectrical impedance analysis, and studying other clinical characteristics, inferior vena cava diameter, and N-terminal pro-B natriuretic peptide associated with hydration status in chronic kidney disease Stages 3&4 and 5 in patients not undergoing dialysis.

METHOD

We examined 62 patients with Stages 3&4 and 68 patients with Stage 5 chronic kidney disease. Plasma NT-proBNP was measured and analyzed after log transformation. Inferior vena cave diameter was measured with echocardiography and indexed for body surface area. Hydration status was assessed using multi-frequency bioelectrical impedance analysis. Overhydration was defined as overhydration/extracellular water >0.15.

RESULTS

Overhydration was more frequent in Stage 5 than in Stages 3&4 patients. Systolic and diastolic blood pressure, inferior vena cava index, and log NT-proBNP were higher in overhydrated compared to non-overhydrated patients. A significant positive correlation existed between overhydration/extracellular water and log NT-proBNP, systolic and diastolic blood pressures, and inferior vena cava index. In multiple linear regression analysis, the variables associated with hydration status were male sex, extracellular water/total body water, and extracellular water/intracellular water (greater overhydration), while serum albumin levels had a negative association with overhydration.

CONCLUSION

Overhydration is more prevalent in Stage 5 chronic kidney disease patients than in Stages 3&4 patients. Bioelectrical impedance analysis, inferior vena cava diameter, and NT-proBNP analysis in chronic kidney disease are useful methods to determine the volume overload.

Body adiposity index assess body fat with high accuracy in nondialyzed chronic kidney disease patients

OBJECTIVE

High body fat (BF) is an alarming condition that also affects nondialyzed chronic kidney disease (CKD) patients. Distinct methods are used to evaluate BF; however, in CKD population it remains unclear which one is more reliable showing high accuracy. Dual-energy X-ray absorptiometry (DXA), used as reference method to estimate adiposity, is expensive and time consuming to be applied in clinical settings. Recently, a new body adiposity index (BAI), that estimates BF from easily accessible measures, was validated in the general population. The aim of this study was to evaluate which simple and practical method, routinely used to estimate BF, shows the highest accuracy compared with DXA, in nondialyzed CKD patients.

DESIGN AND METHODS

In this cross-sectional study BF was estimated by DXA, bioelectrical impedance analysis (BIA), anthropometry (ANTHRO), and BAI. Serum leptin levels were determined.

RESULTS

Studied patients (n = 134) were 55% males, 54% overweight/obese, and 64.9 ± 12.5 years old, with estimated glomerular filtration rate (eGFR) = 29.0 ± 12.7 ml/min. The correlation coefficient was higher between DXA vs. ANTHRO (r = 0.76) and BAI (r = 0.61) than with BIA (r = 0.57), after adjusting for gender, age, and eGFR (P < 0.0001). Therefore, the Lin's concordance correlation coefficient and Bland-Altman plots were performed to measure the accuracy (C_b) between DXA with both ANTHRO and BAI. A higher accuracy (C_b = 0.82) and lower mean difference (-3.4%) was observed for BAI than for ANTHRO (C_b = 0.61; -8.4%). Leptin levels correlated (P < 0.0001) with DXA (r = 0.56) and BAI (r = 0.59).

CONCLUSIONS

These findings suggest that BAI estimates BF with high accuracy in nondialyzed CKD patients and may be helpful in the treatment of this population with increased BF.

Relevância do estado de hidratação na interpretação de parâmetros nutricionais em diálise peritoneal

OBJETIVO: Identificar determinantes do estado de hidratação de pacientes em diálise peritoneal crônica, bem como investigar os efeitos da sobrecarga líquida sobre o estado nutricional. MÉTODOS: Foi feito estudo transversal, realizado em 2006, avaliando 27 pacientes em diálise peritoneal crônica, acompanhados no Hospital das Clínicas da Faculdade de Medicina de Botucatu (SP), quanto a parâmetros clínicos, dialíticos, laboratoriais, antropométricos e de bioimpedância elétrica. Para avaliar a influência de parâmetros sobre o estado de hidratação empregou-se modelo de regressão linear múltipla. A amostra foi estratificada quanto ao estado de hidratação pela relação entre água extracelular e água corporal total (0,47 para homens e 0,52 para mulheres), parâmetros obtidos por meio de bioimpedância elétrica. Comparações foram realizadas por análise de covariância, Mann-Whitney, Qui-quadrado ou teste exato de Fisher. Considerou-se significância estatística quando p≤0,05. RESULTADOS: Pacientes com maior volume urinário e em modalidade dialítica automatizada apresentaram melhor estado de hidratação. Pacientes com maior sobrecarga líquida, comparados àqueles com menor sobrecarga, apresentaram menor ângulo de fase (M=4,2, DP=0,9 vs M=5,7, DP=0,7º; p=0,006), menor albumina (M=3,06, DP=0,46 vs M=3,55, DP=0,52g/dL; p=0,05) e maior % prega cutânea tricipital (M=75,3, DP=36,9 vs M=92,1, DP=56,9%; p=0,058), sem outras evidências antropométricas. CONCLUSÃO: Pode-se sugerir que os níveis reduzidos de albumina e ângulo de fase nos pacientes com maior sobrecarga líquida não estiveram relacionados a pior estado nutricional. Para o diagnóstico nutricional em vigência de sobrecarga líquida, deve-se considerar o conjunto de variáveis obtidas por diversos métodos, buscando relacioná-las e interpretá-las de maneira abrangente, possibilitando um diagnóstico nutricional fidedigno.

Effects of inactivity on human muscle glutathione synthesis by a double-tracer and single-biopsy approach

Oxidative stress is often associated to inactivity-mediated skeletal muscle atrophy. Glutathione is one of the major antioxidant systems stimulated, both at muscular and systemic level, by activation of oxidative processes. We measured changes in glutathione availability, oxidative stress induction and the extent of atrophy mediated by 35 days of experimental bed rest in vastus lateralis muscle of healthy human volunteers. To assess muscle glutathione synthesis, we applied a novel single-biopsy and double-tracer ([(2)H(2)]glycine and [(15)N]glycine) approach based on evaluation of steady-state precursor incorporation in product. The correlations between the traditional (multiple-samples, one-tracer) and new (one-sample, double-tracer infusion) methods were analysed in erythrocytes by Passing-Bablok and Altman-Bland tests. Muscle glutathione absolute synthesis rate increased following bed rest from 5.5 ± 1.1 to 11.0 ± 1.5 mmol (kg wet tissue)(-1) day(-1) (mean ± S.E.M.; n = 9; P = 0.02) while glutathione concentration failed to change significantly. Bed rest induced vastus lateralis muscle atrophy, as assessed by pennation angle changes measured by ultrasonography (from 18.6 ± 1.0 to 15.3 ± 0.9 deg; P = 0.01) and thickness changes (from 2.3 ± 0.2 to 1.9 ± 0.1 cm; P < 0.001). Moreover, bed rest increased protein oxidative stress, as measured by muscle protein carbonylation changes (from 0.6 ± 0.1 to 1.00 ± 0.1 Oxydized-to-total protein ratio; P < 0.04). In conclusion, we developed in erythrocytes a new minimally invasive method to determine peptide synthesis rate in human tissues. Application of the new method to skeletal muscle suggests that disuse atrophy is associated to oxidative stress induction as well as to compensatory activation of the glutathione system.

Reproducibility and validity of bioimpedance spectroscopy for tracking changes in total body water: implications for repeated measurements

Bioimpedance spectroscopy (BIS) has been used to track changes in total body water (TBW). Accurate TBW estimations can be influenced by both methodological and biological factors. One methodological variation that contributes to BIS TBW errors is the electrode placement. The purpose of the present study was to compare the reproducibility and validity of fixed-distance electrode placements (5 cm) with the standard single-site electrode placements. Twenty-nine subjects (fifteen men and fourteen women) participated in the reproducibility study, while sixty-nine subjects (thirty-three men and thirty-six women) participated in the validity study. The reproducibility study included two measurements that were taken 24 h apart, while the validity study consisted of a 12-week exercise intervention with measurements taken at weeks 1 and 12. TBW was estimated using BIS and 2H techniques. Reproducibility results indicated that fixed-distance electrodes reduced the day-to-day standard error of the measurement in men (from 1·13 to 0·81 litres) but not in women (0·47 litres). sem values were lower for women than for men, suggesting that BIS TBW estimates are sex dependent. Validity results produced similar accurate findings (mean difference < 0·21 litres). However, fixed-distance electrodes improved delta TBW errors (mean difference improvements>0·04 litres in men, women, and men and women combined). When tracking changes in TBW, fixed-distance electrodes may reduce reproducibility errors and allow for smaller changes to be detected. However, the reduction of reproducibility errors may be greater for men than for women. Therefore, reproducibility calculations should be based on the sex of the sample population.

Bioelectrical impedance vector analysis to evaluate relative hydration status

The objective was to present our clinical experience with bioelectrical impedance vector analysis (BIVA). Forty-six patients with chronic kidney disease (CKD) without oedema, 21 oedematous nephrotic children and 15 in remission from nephrotic syndrome were studied. The age range was 2-14 years. Data were obtained with the vector bioelectric impedance analysis method (Piccoli's RXc graph with 95% confidence ellipses) and compared with normal paediatric values. The mean vector position differs significantly among the groups of evaluated patients (Hotelling T(2) test, p < 0.05). Mean vector position along the 45 degrees direction (major axis of ellipses) indicates a progressive increase in body fluid volume from patients with CKD stage IV to stages II-III to patients in remission from nephrotic syndrome to oedematous subjects. We observed a progressive vector lengthening in children with severe renal disease (separate 95% confidence ellipse). This pattern indicates relative dehydration. BIVA represents a useful clinical tool that is able to detect changes in hydration.

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

Background

Total 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).

Methods

Twenty-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.

Results

Both 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.

Conclusion

The 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.

Early changes in bioelectrical estimates of body composition in chronic kidney disease

The aim of this study was to detect the potential occurrence of early abnormalities of body composition in patients with chronic kidney disease (CKD) at first referral to an outpatient nephrology clinic. Eighty-four patients with CKD (49 men and 35 women) were compared with 604 healthy control subjects (298 men and 306 women). Anthropometry and bioelectrical impedance analysis (BIA) were performed in all participants, whereas renal function, laboratory tests for nutritional status, and nutrient intake were assessed in the CKD group only. Creatinine clearance was 27.8 +/- 13.8 and 27.4 +/- 13.0 ml/min per 1.73 m(2) in male and female patients with CKD, respectively. No patient showed peripheral edema; frank malnutrition, defined by presence of serum albumin <3.5 g/dl plus body mass index <20 kg/m(2); or protein intake <0.6 g/kg per d. At the BIA, patients with CKD showed lower resistance (R) and abnormal mean impedance vectors for the bivariate normal distribution of R/height and reactance/height. Phase angle also was reduced (-22%), especially in patients with diabetes. When BIA-derived data were considered, total body water was slightly higher (+4.3% in men; +3.5% in women) and body cell mass was lower (-6.7% in men; -7.7% in women) in patients with CKD. No difference in either BIA parameters or nutritional indexes was observed among various CKD stages. Despite the absence of overt malnutrition, patients with CKD exhibit altered BIA variables from the early phases of renal disease. These alterations are related to the renal dysfunction, are more marked in the presence of diabetes, and mainly indicate the presence of overhydration in the absence of edema. Therefore, BIA represents an attractive clinical tool to detect impairment of body composition from the early stages of CKD.