Mean Impedance Vector Research Articles

Bioelectrical Impedance Vectors Analysis of Sarcopenic Older Adults Submitted to a Resistance Training Program.

The objective of the present study is to analyze the changes in bioimpedance vector analysis (BIVA) and phase angle (PhA) in sarcopenic older people submitted to a 12-week resistance training (RT) program according to classic and specific analyses. To this end, 20 sarcopenic older adults of both sexes, invited through media, underwent bioimpedance analysis before and after the RT carried out three times a week, for 12 weeks. The mean impedance vectors of the groups established for the confidence ellipses (95% of the confidence ellipse) are compared using Hotelling's T2 test. The distance D from Mahalanobis is also calculated. Classic and Specific BIVA are presented. The resistance values for the classical analyses (R/H) decreased across all groups (whole group, women and men, p < 0.05), with approximate decreases ranging from 9.4% to 10%, while the classic reactance (Xc/H) decreased (p < 0.05) only for the whole group (5.9%) and men (7.7%). For the specific BIVA, trends are verified for the whole sample, with a decrease in resistance (R.sp) and an increase in reactance (Xc.sp). In conclusion, the RT program in sarcopenic individuals promoted a reduction in resistance values in classical analyses, indicating a possible increase in hydration status and, consequently, musculoskeletal mass.

The positive relationship between NUTRIC score, bioelectric measures and hospital mortality in critically ill patients

PurposeBioelectrical impedance vector analysis (BIVA) and phase angle (PA) have importance in assessing nutritional and prognosis, and this study hypothesized that these measurements can have a relationship with nutritional risk and outcomes. This study aims to analyze the association between Nutrition Risk in the Critically ill (NUTRIC) score and bioelectrical impedance measures with hospital mortality in critically ill patients.Design/methodology/approachA prospective, cohort study was performed with a consecutive sample of patients admitted to an intensive care unit (ICU), between January and June 2017 at a hospital university in Northwest Brazil. The NUTRIC score and the bioelectric measures, such as resistance (R), reactance (Xc), PA and BIVA, were completed within the first 24 h of admission. The Student’s t or Mann–Whitney, Pearson’s or Spearman’s coefficient and Fisher’s exact tests and BIVA were used for statistical analyses.FindingsThe sample consisted of 81, with a mean age of 57 (16.7) years, with 60.5% women. It was detected that PA and Xc were lower (p < 0.001), and age was higher (p < 0.001) in a high nutritional-risk group. It was found an association between low nutritional risk and hospital discharge (p < 0.001), and that individuals who died spent more days in the ICU (p = 0.0375), had significantly lower PA and Xc values (p = 0.043 and p = 0.0172, respectively) and higher NUTRIC scores (<0.0001). There was a displacement of the mean impedance vector in men and women with high nutritional risk (p = 0.0037 and p = 0.004, respectively).Research limitations/implicationsThe height measurement was estimated using predictive formulas, which may affect the accuracy of the values; BIA was performed only upon admission of the patient to the ICU and the study population was heterogeneous, as it is a general ICU.Originality/valueThis paper shows that, in critically ill patients, nutritional screening and the assessment of bioelectrical measures help in clinical-nutritional decisions, and were able to predict outcomes.

Higher Body Fat but Similar Phase Angle Values in Patients with the Classical Form of Congenital Adrenal Hyperplasia in Comparison to a Control Group.

This study aimed to compare phase angle (PhA) and bioelectrical impedance vector analysis (BIVA) values between adult patients with congenital adrenal hyperplasia caused by 21-hydroxylase deficiency (CAH21OHD) and a control group. A total of 22 patients (15 women, 22.9 ± 3.7 years) were compared with 17 controls (11 women, 27.0 ± 2.5 years). Body composition was determined by dual-energy X-ray absorptiometry. Bioelectrical impedance was used to calculate PhA, and BIVA was performed using specific software. Student’s t-test and analysis of covariance were used to compare groups. Hedges’ G and partial n2 were calculated for the effect estimates. Hotelling’s t2 test was used to compare the mean impedance vectors between the groups. The Mahalanobis test was used to determine the distance between confidence ellipses. Patients with CAH21OHD had a higher fat mass percentage than that of the control group (both sexes). There was no significant difference in PhA values between groups (CAH21OHD vs. control) in females (6.9° vs. 6.3°, p = 0.092) and males (8.2° vs. 8.1°, p = 0.849), after adjusting for covariates (age and height). BIVA analysis showed a significant difference in the mean impedance vectors between the female groups (T2 = 15.9, D = 1.58, p = 0.003) owing to the higher reactance/height (Δ = 8.5; p < 0.001) of the patients. The PhA did not significantly differ between the groups. Female patients had significantly higher reactance values. However, further studies are needed to determine the usefulness of bioimpedance parameters in evaluating the hydration status and cellular integrity of patients with CAH21OHD.

Association of electrical bioimpedance vectors with the nutritional classification of vulnerable multiethnic children.

Monitoring growth and body composition in childhood is vital for early detection of health and nutrition problems during child development. The bioelectrical impedance vector analysis (BIVA) revealed its effectiveness as an indicator of nutritional status. This study aimed to measure the bioimpedance vectors of a sample of multiethnic children and evaluate the utility of BIVA for the classification of the nutritional status in a group of children with greater vulnerability, including in the presence of obesity. This is a cross-sectional study that analyzed the bioelectrical impedance of a sample of 321 children from public daycare centers, aged 1-4 years, using the RXc graph method (tetrapolar analysis at 50kHz frequency). The 95%, 75%, and 50% tolerance ellipses were plotted by age group. The Z-scores of bioimpedance parameters (Xc/H-Z and R/H-Z) were calculated regarding age, which were used to build reference tolerance ellipses for a single group, regardless of age. Such ellipses were evaluated for their ability to recognize the pattern and classify the deviations, using individual vectors of obese children. The mean impedance vectors showed progressively higher reactances and lower resistances with age. In the group of obese children, the individual vectors located outside the 95% baseline tolerance ellipse were 12.5%, 18.75%, and 11.1% of the cases for the WHZ, WAZ, and BMIZ criteria, respectively, all above the expected 5%, but much below expectations. This may be a problem with the obesity criteria used, as WHZ, WAZ, and BMIZ do not differentiate fat from lean mass. Bioimpedance vector analysis reflects differences in the bioelectric patterns of children classified as obese. Provided the obesity criteria are constructed based on fat measurements, rather than lean mass, the use of tolerance ellipses in the BIVA chart is promising as a tool for monitoring nutritional status where measuring body composition is difficult, because constant tissue hydration cannot be assumed.

The impact of 2weeks of detraining on phase angle, BIVA patterns, and muscle strength in trained older adults.

An intermission in the training routine, in which older adults refrain from regular structured exercise, may have deleterious effects on muscle performance and bioelectric phase angle (PhA), which is a predictive marker for cellular integrity. To determine the effects of a 2-week detraining period on PhA and muscular strength (MS) in trained older adults. A total of 14 trained older adults (6 females) aged ≥65years (77.2±6.6) were assessed at baseline (i.e. trained condition) and after 2weeks of detraining, where they refrained from their usual participation in structured exercise sessions. Whole-body resistance (R), reactance (Xc), and PhA were assessed using bioelectrical impedance analysis (BIA, single frequency, 50kHz±1%, NutriLab, Akern). MS was assessed on both lower and upper limbs under isometric conditions. Differences between moments were examined using ANOVA for repeated measures, while adjusting for sex. Bioimpedance vector analysis (BIVA) was performed to evaluate changes in cellular function and body fluid content. Detraining resulted in declines in PhA (-4.34%) (p=0.017). There was a significant difference in the mean impedance vectors from baseline to post-detraining (p<0.05), which were driven by decreases in reactance (Xc) relative to height (Xc/H) with little change in resistance (R) relative to height (R/H) for both males and females. No differences were found in MS for both the leg press (p=0.992) and bench press (p=0.166) tests. A detraining period as short as 2-weeks is enough to cause alterations in the bodies bioelectrical properties, resulting in detrimental changes in PhA, due to alterations in cellular integrity, but not in MS. These results highlight the importance of maintaining structured exercise sessions in older adults, and reinforce the potential role of PhA as a sensitive predictor to detect acute changes in muscle cell integrity following alterations in exercise training.

Bioimpedance Vector References Need to Be Period-Specific for Assessing Body Composition and Cellular Health in Elite Soccer Players: A Brief Report.

Purpose: Bioimpedance data through bioimpedance vector analysis (BIVA) is used to evaluate cellular function and body fluid content. This study aimed to (i) identify whether BIVA patters differ according to the competitive period and (ii) provide specific references for assessing bioelectric properties at the start of the season in male elite soccer players. Methods: The study included 131 male soccer players (age: 25.1 ± 4.7 yr, height: 183.4 ± 6.1 cm, weight: 79.3 ± 6.6) registered in the first Italian soccer division (Serie A). Bioimpedance analysis was performed just before the start of the competitive season and BIVA was applied. In order to verify the need for period-specific references, bioelectrical values measured at the start of the season were compared to the reference values for the male elite soccer player population. Results: The results of the two-sample Hotelling T2 tests showed that in the bivariate interpretation of the raw bioimpedance parameters (resistance (R) and reactance (Xc)) the bioelectric properties significantly (T2 = 15.3, F = 7.6, p ≤ 0.001, Mahalanobis D = 0.45) differ between the two phases of the competition analyzed. In particular, the mean impedance vector is more displaced to the left into the R-Xc graph at the beginning of the season than in the first half of the championship. Conclusions: For an accurate evaluation of body composition and cellular health, the tolerance ellipses displayed by BIVA approach into the R-Xc graph must be period-specific. This study provides new specific tolerance ellipses (R/H: 246 ± 32.1, Xc/H: 34.3 ± 5.1, r: 0.7) for performing BIVA at the beginning of the competitive season in male elite soccer players.

Bioelectrical impedance vector values in a Spanish healthy newborn population for nutritional assessment.

Vector bioimpedance analysis (BIVA) can be very useful for the evaluation of body composition, hydration, and nutritional status in infants and newborns. The objective of this study was to determine the impedance vector distribution for a group of healthy newborn Spanish children. This was a cross-sectional, descriptive study conducted with 154 healthy, Spanish newborns (gestational age: 37-41 weeks) aged 24 to 72 hours (79 males, 75 females). Weight, height, and cephalic-circumference were determined. Resistance and reactance were measured with a single-frequency impedance analyzer at 50 kHz (tetrapolar analysis). The newborns' specific 95% confidence intervals of the mean vectors and the 95%, 75%, and 50% tolerance intervals for the individual vector measurements were plotted using R and Xc components standardized by the subjects' lengths. The mean impedance vectors were compared with Hotelling's-T2 test for vector analysis (significance level: P < .05). The newborns exhibited gender-related differences in the mean impedance vector (mean [SD] R/H: 833.6 [97.5] Ohm/m in males vs 918.2 [107.7] Ohm/m in females; mean [SD] Xc/H: 91.3 [34.7] Ohm/m in males vs 95.6 [23.2] Ohm/m in females). No statistically significant differences in the mean impedance vectors were observed according to days of life. Lower values of resistance and slightly higher reactance values were observed in the healthy Spanish newborns compared to Italian newborns. New tolerance ellipses were constructed for healthy Spanish newborns. These data allow detecting alterations in the hydration status and cell mass in term newborns in the first 3 days of life.

Bioelectrical impedance vector analysis (BIVA) as a method to compare body composition differences according to cancer stage and type

Bioelectrical impedance vector analysis (BIVA) is a non-invasive method of measuring human body composition. This offers the potential to evaluate nutritional and hydration states in cancer. Analysis of BIVA data using the z-score method (the number of standard deviations away from the mean value of the reference group) has the potential to facilitate comparisons between different cancer types. The aim of this study was to use the BIVA Reactance (R)/Reactance (Xc) z-score method to evaluate body composition differences in cancer, using data from previously published BIVA studies. Previous studies using BIVA in cancer were identified from the literature. Bioimpedance measurements were analysed using the BIVA RXc z-score graph. The mean impedance vectors from the studied populations were transformed into standard deviates (with respect to the mean and standard deviation of the reference populations). Body composition was classified according to vector placement (i.e. normal, athletic, cachectic, oedematous and dehydrated). Seven male and three cancer female populations were evaluated. Body composition was classified as normal for the majority (n=5), followed by cachexia (n=4) and athletic (n=1) respectively. Variation in body composition for the studied populations appeared to be related to gender, disease type and severity. The BIVA RXc z-score method has potential to evaluate body composition differences between cancer groups. This method can study body composition, according to cancer type, stage, gender and ethnicity. Limitations of the method relate to issues concerning the appropriate use of reference populations and variability between bioimpedance analysers. Better body composition assessment has the potential to personalise therapeutic, nutritional and hydration management. Further work is essential to facilitate in-depth evaluation in these areas, in order to achieve meaningful use of BIVA in clinical practice.

Bioimpedance Vector Analysis of Elite, Subelite, and Low-Level Male Volleyball Players.

To establish a specific player profile on body-composition parameters and to provide a data set of bioelectric impedances values for male volleyball players. The study included 201 athletes (age 26.1 [5.4]y, height 191.9 [9.7]cm, weight 86.8 [10.8]kg) registered in the Italian volleyball divisions. The athletes were divided into 3 groups: The elite group comprised 75 players participating in the 1st (Super Lega) division, the subelite group included 65 athletes performing in the 2nd (Serie A2) division, and the low-level group included 61 players participating in the 3rd (Serie B) division. Bioelectric impedance, body weight, and height of the athletes were measured in the second half of the competitive season. In addition, bioelectrical impedance vector analysis was performed. The elite group showed a greater amount of fat-free mass (FFM) and total body water (TBW) and a lower fat mass (FM) than the subelite group (P < .05). In addition, the elite players were taller and heavier and had a higher FFM, FM, TBW, and body cellular mass than the low-level athletes (P < .05). Finally, the mean impedance vectors of the elite group significantly differed from those measured in the normal population and in the other 2 groups (P < .05). This study provides an original data set of body-composition and bioelectric impedance reference values of elite male volleyball players. The results might be useful for interpretation of individual bioimpedance vectors and for defining target regions for volleyball players.

Bioelectrical impedance vector reference values for assessing body composition in a Spanish child and adolescent population.

Reference values of the bioelectrical impedance vector for the Spanish child and adolescent population are needed for assessing body composition and hydration status in this population. The aim of this study is to provide reference values of the bioelectrical impedance vector in Spanish children and adolescents aged 4-18years from Castilla y León. This was a cross-sectional descriptive study conducted in 4401 Spanish healthy children and adolescents aged 4-18years (2265 boys and 2136 girls). Resistance and reactance were measured with a single-frequency impedance analyzer at 50kHz (tetrapolar analysis). The values of resistance and reactance normalized by height were used to plot the bivariate 50th, 75th, and 95th percentiles of the population by age group. Mean impedance vectors were compared with Hotelling's T2 test for vector analysis (differences being considered significant if p<.05). Tolerance ellipses were drawn for the Spanish child and adolescent population studied. The mean impedance vector showed displacement across all age groups except for (1) girls aged 12-13years, (2) girls aged 15-18years, and (3) boys aged 16-18years. There were sex-related differences in the mean impedance vector in all age ranges, even in prepubertal children. Among adolescents, the patterns of the vector displacement were consistent with the timing of normal growth and development in all groups and are attributable to the maturation process. New tolerance ellipses have been constructed for Spanish children and adolescents by sex and age. These ellipses reflect the timing of normal childhood growth and development.

Specific BIVA recognizes variation of body mass and body composition: Two related but different facets of nutritional status

ObjectiveThe aim of this study was to demonstrate the different information provided by body mass index (BMI) in combination with specific bioelectrical impedance vector analysis (specific BIVA) in the measure of relative body fat. MethodsAnthropometric and bioelectrical values and dual-energy x-ray absorpitometry measurements from a sample of 1590 US adults of both sexes were retrieved from the National Health and Nutrition Examination Survey 2003–2004. The sample distribution of the BMI of each sex was divided into deciles. Quartiles were calculated for percent fat mass (FM%) after stratifying by BMI deciles. Body composition and bioelectrical characteristics of groups below the first and above the third quartile were compared using analysis of variance and the Hotelling's T-square test. ResultsBMI and specific BIVA showed a different accuracy in detecting body composition variations: BMI showed similar values in groups represented by different FM percentages, whereas the bioelectrical differences were statistically significant. The mean impedance vectors corresponding to cases below the first FM% quartiles were shorter and located on the left side of the ellipses (the region of higher fat-free mass), whereas those above the third FM% quartiles were on the right and toward the upper pole (the region of higher FM%). ConclusionsSpecific BIVA is a technique for the evaluation of body composition which can add relevant information regarding BMI.

Effects of resistance training on classic and specific bioelectrical impedance vector analysis in elderly women

Raw bioelectrical impedance analysis (BIA) data [resistance (R); reactance (Xc)] through bioelectrical impedance vector analysis (BIVA) and phase angle (PhA) have been used to evaluate cellular function and hydration status. The purpose of this investigation was to examine the effects of resistance training (RT) on classic and specific BIVA in elderly women. Twenty women (mean±SD; age: 71.9±6.9years; BMI: 24.5±3.0kgm−2) completed a 6-month RT program. Whole-body, single-frequency BIA, body geometry, and leg strength (5RM) measures were completed at baseline (t0), 3months (t3), and 6months (t6). The mean impedance vector displacements were compared using Hotelling's T2 test to evaluate changes in R and Xc relative to height (R/ht; Xc/ht) or body volume (Rsp; Xcsp) estimated from the arms, legs, and trunk. 5RM, PhA, and BIVA variables were compared using ANOVA. PhA improved at t6 (p<0.01), while 5RM improved at t3 and t6 (p<0.01). Using classic BIVA, 6months (T2=31.6; p<0.01), but not 3months of RT (T2=4.5; p=0.20), resulted in significant vector migration. Using specific BIVA, 6months (T2=24.4; p<0.01), but not 3months of RT (T2=5.5; p=0.10), also resulted in significant vector migration. 5RM was correlated to both PhA (r=0.48–56) and Xcsp (r=0.45–53) at all time points. Vector displacements were likely the result of improved cellular integrity (Xcsp) and cellular health (PhA).

Rational management of food intolerance in an elite soccer club

Background Gastric intestinal, skeletal muscle and neurological symptoms are just some of the possible effects of alimentary intolerances that may represent a risk for one’s health and may frustrate the athlete’s practice benefits and thwart the performance. The immunological tolerance recovery and the re-establishment of a normal diet are generally reached by means of strict dietetic schemes (a turnover or elimination diet) requiring a strong effort into changing one’s diet habit. In the elite soccer athlete, an intense competitive schedule including long transfers represents another risk to these dietetic therapies fulfilment that may even worsen the symptomatology once the allergens responsible for the intolerances are again within the diet.The purpose of this study was to objectively estimate an food intolerance in elite soccer players who have foodintolerance symptoms, by arranging a nutritional plan for the immunological tolerance recovery, the symptomatology improvement and to test the effectiveness in terms of nutritional situation by means of the BIVA, assuming a close relation among food intolerances, inflammatory reactions and nutritional status. Methods Eight males 32.5 ± 1.9 years old soccer players and BMI 24.9 ± 1.1 (Average ± DS) with symptoms of possible food intolerance (gastralgia, headache, intestinal meteorism, diarrhoea, constipation, nausea) of an Italian Serie A soccer team were subjected to the ALCAT test (IMGeP, Milan, Italy) before and after eight months of a personalized nutritional treatment. The athletes body composition was basally valued and at the end of the BIVA analysis (50 kHz, BIA 101 RJL, Akern Bioresearch, Florence, Italy). Results The athletes tested, with food intolerance symptoms, were ALCAT test variously positive. The personalized nutritional treatment based on moderation rather than on drastic elimination of reactive foods and complying with the specific nutritional needs of the elite soccer player led to a nearly complete resolution of the first symptoms as the clinical evaluation and the post-treatment ALCAT test results demonstrate. Parallel to these results a significant shift of the mean impedance vector was observed (Hotelling T2 test, p < 0.0001), so indicating a more favourable condition of the soft tissues (hydration and/or mass) with no BMI variation (p<0.05). Conclusions The ALCAT test seems to be able to detect the food intolerance reactions when it is applied to patients with initial specific symptoms. A personalized and flexible nutritional therapy based on moderation and rational elimination of reactive foods seems to be working and be suitable for the elite athlete whose specific logistic necessities ( for example long travels) discourage the classic dietary regime. An efficient handling of the food intolerances seems to lead to a nutritional condition improvement, maybe reducing the concerned inflammatory situation as observed in body composition changing, which may influence the sports performance.

Distribution of bioelectrical impedance vector values in multi-ethnic infants and pre-school children

Ethnicity may influence bioimpedance values. The goal of this study was to measure total body impedance vector in infants and pre-school children in Brazil and compare them with those reported in other countries. We analyzed bioelectrical impedance from a sample of 255 healthy Brazilian children, aged 1-36 months, using the RXc graph method (tetrapolar analysis at 50kHz frequency). The 95%, 75% and 50% tolerance ellipses were plotted by age group. The mean impedance vector showed migration across age groups, with progressive higher reactances and lower resistances as age increased. The mean bioimpedance vectors from the present sample of Brazilian children were different from those of European children of the same age ranges. Our results confirm the importance of defining reference values of total body impedance vector for each country in view of the considerable ethnic diversity among different geographical areas.

Application of bioelectrical impedance vector analysis (BIVA) in dogs: a preliminary study on gender-related differences

In this preliminary study, BIVA has been performed on 17 healthy Italian Hound dogs, 10 males (M) and 7 females (F), in order to verify if gender-related differences can be detected. Only in F higher reactance (Xc) values (F: 46.4 vs M: 37.7, P<0.05) and a significant negative correlation (-0.80, P<0.05) between BCS and resistance (R) values were detected. 50%, 75% and 95% tolerance ellipses were calculated both in M and F using average Xc and R values standardized for withers height. Probably due to the low number of subjects used in the present study, the variability of the individual vector distribution (F: 79.6 vs M: 53.0Ohm/m), as well as the mean impedance vector lengtht (F: 548.2 vs M: 498.9Ohm/m), were similar in F and M. The gender-related difference in phase angle values was not significant (F: 0.168 vs M: 0.157, P=ns). In conclusion, the use of BIVA in dogs indicated differences between males and females which should be confirmed by a larger number of subjects.

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.

Bioelectrical impedance vector distribution in the first year of life

Objective We assessed the bioelectrical impedance vector distribution in a sample of healthy infants in the first year of life, which is not available in literature. Methods The study was conducted as a cross-sectional study in 153 healthy Caucasian infants (90 male and 63 female) younger than 1 y, born at full term, adequate for gestational age, free from chronic diseases or growth problems, and not feverish. Z scores for weight, length, cranial circumference, and body mass index for the study population were within the range of ±1.5 standard deviations according to the Euro-Growth Study references. Concurrent anthropometrics (weight, length, and cranial circumference), body mass index, and bioelectrical impedance (resistance and reactance) measurements were made by the same operator. Whole-body (hand to foot) tetrapolar measurements were performed with a single-frequency (50 kHz), phase-sensitive impedance analyzer. The study population was subdivided into three classes of age for statistical analysis: 0 to 3.99 mo, 4 to 7.99 mo, and 8 to 11.99 mo. Using the bivariate normal distribution of resistance and reactance components standardized by the infant’s length, the bivariate 95% confidence limits for the mean impedance vector separated by sex and age groups were calculated and plotted. Further, the bivariate 95%, 75%, and 50% tolerance intervals for individual vector measurements in the first year of life were plotted. Results Resistance and reactance values often fluctuated during the first year of life, particularly as raw measurements (without normalization by subject’s length). However, 95% confidence ellipses of mean vectors from the three age groups overlapped each other, as did confidence ellipses by sex for each age class, indicating no significant vector migration during the first year of life. Conclusions We obtained an estimate of mean impedance vector in a sample of healthy infants in the first year of life and calculated the bivariate values for an individual vector (95%, 75%, and 50% tolerance ellipses).

Normal values of the bioelectrical impedance vector in childhood and puberty

The purpose of this study was to determine the reference, bivariate, and tolerance intervals of the whole-body impedance vector in Italian children. This was a cross-sectional, multicenter study, and participants were chosen from the general school population. The impedance vector (standard, tetrapolar analysis at 50-kHz frequency) was measured in 3110 subjects, ages 2 to 15 y, and 2044 healthy children (1014 male and 1030 female) with weight and height within the 95th percentile were selected for the analysis (resistance-reactance graph method). The age-specific 95% confidence intervals of mean vectors and the 95%, 75%, and 50% tolerance intervals for individual vector measurements were plotted using resistance and reactance components standardized by the subject’s height. Mean vectors from both sexes with separate 95% confidence ellipses were considered as representative of eight different age groups, from 2 to 13 y. There was a statistically significant sex effect on vector distribution from boys and girls in the age group of 14 to 15 y. The impedance vector distribution of children was also compared with healthy adult subjects (354 male and 372 female, age 15 to 85 y). There was a progressive, statistically significant vector shortening from age 2 to 15 y toward the adults’ vector position. In conclusion, we established the trajectory followed by the mean impedance vector in children over ages 2 to 15 y and also obtained the reference, bivariate, and 95%, 75%, and 50% tolerance intervals of the impedance vector by age for healthy children, with which the vectors from children with altered body composition can be tested.

The RXc graph in evaluating and monitoring fluid balance in patients with liver cirrhosis.

A recent study, using height-standardized resistance (R/H) and reactance (Xc/H) and assuming a bivariate distribution, has proposed the "RXc graph". We applied this new approach for patients with chronic liver disease in differentiating various degrees of fluid unbalance. Our data showed that a 95% confidence ellipse of patients with chronic hepatitis (CH) overlapped that of healthy control subjects (CONTR), while those of patients with liver cirrhosis (CIR), patients with cirrhosis and ascites (ACIR), and patients with cirrhosis, edemas, and ascites (AECIR) were clearly different for both genders. A progressively shorter mean impedance vector proportional to the stage of liver disease and to the degree of fluid unbalance was found. The lower half of the 50% tolerance ellipse for the healthy population proved to be a threshold for cirrhotics, while almost all the subjects with clinically detectable edema fell outside this limit. The RXc graph was shown to be useful in monitoring the treatment of fluid unbalance and for the immediate selection of patients in whom BIA can precisely assess body composition.

Identification of operational clues to dry weight prescription in hemodialysis using bioimpedance vector analysis

Identification of operational clues to dry weight prescription in hemodialysis using bioimpedance vector analysis