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Bioelectrical Impedance Vector Analysis in Healthy Term Infants in the First Three Months of Life in Brazil
Abstract
Objective: Bioelectrical impedance vectorial analysis (BIVA) can be considered a favorable method for evaluation and monitoring of nutritional and hydration status without assumptions regarding body composition or requirement of prediction formulas. The present study aimed to determine bivariate tolerance intervals of the whole-body impedance vector for healthy term infants aged 1 to 3 months.
Methods: This is a descriptive cross-sectional study. Anthropometric and bioelectrical impedance data (800 mA–50 kHz) were obtained. Bivariate vector analysis was conducted with the resistance–reactance (RXc) graph method. BIVA software was used to construct the graphs.
Results: A total of 150 appropriate for gestational age infants (48.7% boys) who were exclusively breastfed and were 56.4 (SD = 23.1) days of age were studied. RXc tolerance ellipses (50, 75, and 95%) were constructed for boys and girls, but a general reference graph was defined for all infants considering the overlapping of ellipses between the genders. All graphs differed from those in national and foreign studies.
Conclusion: New reference tolerance ellipses (95, 75, and 50%) for 1- to 3-month-old infants were constructed, pointing out the need for specific reference values of total body impedance vectors in different regions of Brazil. The RXc tolerance ellipses can be used for clinical practice and provide an easy method to evaluate and monitor body composition and hydration status.
... For this reason, it has been helpful as an indicator of health, prognosis, and mortality in diverse clinical situations [13,20e24]. PhA can be superior to other nutritional, biochemical, or anthropometric parameters [25,26] and are valuable in evaluating the nutritional status of children, especially if interpreted together with BIVA [5,9]. ...
... For this reason, it has been helpful as an indicator of health, prognosis, and mortality in diverse clinical situations [13,20e24]. PhA can be superior to other nutritional, biochemical, or anthropometric parameters [25,26] and are valuable in evaluating the nutritional status of children, especially if interpreted together with BIVA [5,9]. ...
Background & Aims: Bioimpedance parameters are important for assessing children's body composition and health status. However, interpreting these parameters is still challenging, especially without reference data and cut-off points.This study aimed to describe gender-specific reference phase angle (PhA) values and bioelectrical impedance vector analysis (BIVA) plots for healthy Brazilian children. Methods: Children aged 6–9 years were recruited from four public schools in Natal, Brazil. Anthropometric measurements and bioelectrical impedance (BIA) were performed. The values of age, weight (kg), height (cm), resistance (Ω), and reactance (Ω) were measured. Only eutrophic children were included according to body mass index (BMI)-for-age Z-score. BIVA 2002 software was used for the construction of BIVA plots. A P-value
... Likewise, bioelectrical impedance vector analysis (BIVA), a technique which involves plotting bioimpedance parameters against a reference ellipse, but does not allow for the absolute quatification of body composition, is beyond the scope of this paper. We direct the reader to Toffano et al.'s [35] article. ...
There has been increasing interest in understanding body composition in early life and factors that may influence its evolution. While several technologies exist to measure body composition in infancy, the equipment is typically large, and thus not readily portable, is expensive, and requires a qualified operator. Bioelectrical impedance analysis shows promise as an inexpensive, portable, and easy to use tool. Despite the technique being widely used to assess body composition for over 35 years, it has been seldom used in infancy. This may be related to the evolving nature of the fat-free mass compartment during this period. Nonetheless, a number of factors have been identified that may influence bioelectrical impedance measurements, which, when controlled for, may result in more accurate measurements. Despite this, questions remain in infants regarding the optimal size and placement of electrodes, the standardization of normal hydration, and the influence of body position on the distribution of water throughout the body. The technology requires further evaluation before being considered as a suitable tool to assess body composition in infancy.
Background: Bioelectrical Impedance Vector Analysis (BIVA) emerges as a technique that utilizes raw parameters of bioelectrical impedance analysis and assumes the use of a reference population for information analysis. Objective: To summarize studies that have utilized BIVA in children and adolescents without diagnosed diseases. Methods: A systematic search was conducted in nine electronic databases (CINAHL, LILACS, PubMed, SciELO, Scopus, SPORTDiscus, Science Direct, MEDLINE, and Web of Science). Studies with different designs which allowed extracting information regarding reference values of BIVA in children and adolescents without diagnosed diseases, aged 19 years or younger, were included. The systematic review followed PRISMA procedures and was registered in PROSPERO (registration: CRD42023391069). Results: After applying the eligibility criteria, 36 studies were included. Twenty studies (55.6%) analyzed body composition using BIVA, thirteen studies (36.1%) aimed to establish reference values for BIVA, and three studies (8.3%) investigated the association of physical performance with BIVA. There was heterogeneity regarding the reference populations employed by the studies. Fifteen studies used their own sample as a reference (41.6%), four studies used the adult population as a reference (11.1%), and five studies used reference values from athletes (13.9%). Conclusion: Despite the wide applicability of BIVA, studies were found to utilize reference values with characteristics that diverged from the populations of interest.
Background & aims:
The bioimpedence phase angle has been considered as a predictor for morbidity and mortality in different clinical situations, although reference values from a large healthy population are lacking. The aim of this meta-analysis is to estimate mean phase-angle values in healthy individuals.
Methods:
This meta-analysis systematically searched MEDLINE, EMBASE, The Cochrane Controlled Trials Register, SCIELO, LILACS, CINAHL, Web of Science and gray literature for studies estimating mean phase angles. Quality of evidence was assessed for all studies and subgroup (males and females) meta-analysis stratified by age group according to literature (up to 2; 3-5; 6-12; 13-15; 16-18; 19-28; 29-38; 39-48; 49-58; 59-69; 70-80 and >80 years of age) were conducted using random-effects models.
Results:
A total of 46 studies including 249,844 subjects were selected for the present analysis. Males show a pooled estimate of the mean phase angle of 3.6 (95% CI: 3.0-4.1) for infants (0-2 y), increasing progressively to 7.3 (95% CI: 7.0-7.5) at the teenage phase (16-18 y), stabilizing during adult ages (18-38) and decreasing progressively with ongoing years with an estimate of 5.3 (95% CI: 4.5-6.0) for elderly above 80 years old. Similarly, females start from 3.7 (95% CI: 3.2-4.3) for infants (0-2 y), increasing progressively to 6.4 (95% CI: 6.1-6.8) at the teenage phase (16-18 y), stabilizing during adult ages (18-48) and decreasing progressively with ongoing years with an estimate of 5.4 (95% CI: 5.3-5.6) for elderly above 80 years old. Also, males have higher estimates than females for all age groups except for infants (0-2) and subjects older than 80 years old. Heterogeneity was high for all age groups.
Conclusions:
In both sexes, phase-angle values have a similar pattern that start from infants, increase progressively up to the teenage phase, stabilize during adult ages, and then decrease progressively in older subjects and the elderly.
Objective. The aims of this study were to evaluate the periodontal health of pregnant women and to investigate the association of periodontal status with demographic and socioeconomic characteristics, as well as medical and dental history. Materials and Methods. A total of 311 pregnant women were interviewed to obtain sociodemographic data along with medical and dental histories. Clinical examinations were performed to record the presence of visible plaque, gingival bleeding, and caries activity. The periodontal condition was evaluated by Community Periodontal Index of Treatment Needs (CPITN) in one tooth of each sextant (16, 11, 26, 36, 31, and 46). Results. After the adjustment analysis, the presence of visible plaque remained the main determinant of gingival bleeding (OR = 2.91, CI = 1.91–4.48). First-trimester pregnancy status was also a predictor, with a lower prevalence of gingival bleeding observed in the second (OR = 0.87, CI = 0.77–0.99) and third (OR = 0.82, CI = 0.73–0.93) trimesters. Conclusion. In pregnant women, the presence of dental plaque and first-trimester pregnancy status were the main implicated factors predicting gingival bleeding.
The use of bioelectrical impedance analysis (BIA) is widespread both in healthy subjects and patients, but suffers from a lack of standardized method and quality control procedures. BIA allows the determination of the fat-free mass (FFM) and total body water (TBW) in subjects without significant fluid and electrolyte abnormalities, when using appropriate population, age or pathology-specific BIA equations and established procedures. Published BIA equations validated against a reference method in a sufficiently large number of subjects are presented and ranked according to the standard error of the estimate.
The determination of changes in body cell mass (BCM), extra cellular (ECW) and intra cellular water (ICW) requires further research using a valid model that guarantees that ECW changes do not corrupt the ICW. The use of segmental-BIA, multifrequency BIA, or bioelectrical spectroscopy in altered hydration states also requires further research.
Malnutrition constitutes a major public health concern worldwide and serves as an indicator of hospitalized patients' prognosis. Although various methods with which to conduct nutritional assessments exist, large hospitals seldom employ them to diagnose malnutrition. The aim of this study was to understand the prevalence of child malnutrition at the University Hospital of the Ribeirão Preto Medical School, University of São, Brazil. A cross-sectional descriptive study was conducted to compare the nutritional status of 292 hospitalized children with that of a healthy control group (n=234). Information regarding patients' weight, height, and bioelectrical impedance (i.e., bioelectrical impedance vector analysis) was obtained, and the phase angle was calculated. Using the World Health Organization (WHO) criteria, 35.27% of the patients presented with malnutrition; specifically, 16.10% had undernutrition and 19.17% were overweight. Classification according to the bioelectrical impedance results of nutritional status was more sensitive than the WHO criteria: of the 55.45% of patients with malnutrition, 51.25% exhibited undernutrition and 4.20% were overweight. After applying the WHO criteria in the unpaired control group (n=234), we observed that 100.00% of the subjects were eutrophic; however, 23.34% of the controls were malnourished according to impedance analysis. The phase angle was significantly lower in the hospitalized group than in the control group (P<0.05). Therefore, this study suggests that a protocol to obtain patients' weight and height must be followed, and bioimpedance data must be examined upon hospital admission of all children.
This study aims to describe prenatal care provided to pregnant users of the public or private health services in Brazil, using survey data from Birth in Brazil, research conducted from 2011 to 2012. Data was obtained through interviews with postpartum women during hospitalization and information from hand-held prenatal notes. The results show high coverage of prenatal care (98.7%), with 75.8% of women initiating prenatal care before 16 weeks of gestation and 73.1% having six or more number of appointments. Prenatal care was conducted mainly in primary health care units (89.6%), public (74.6%), by the same professional (88.4%), mostly physicians (75.6%), and 96% received their hand-held prenatal notes. A quarter of women were considered at risk of complications. Of the total respondents, only 58% were advised about which maternity care service to give birth, and 16,2% reported searching more than one health service for admission in abour and birth. Challenges remain for improving the quality of prenatal care, with the provision of effective procedures for reducing unfavourable outcomes.
Malnutrition is common in the critically ill patients and known to cause a variety of negative clinical outcomes. However, various conventional methods for nutrition assessment have several limitations. We hypothesized that body composition data, as measured using bioelectrical impedance analysis (BIA), may have a significant role in evaluating nutritional status and predicting clinical outcomes in critically ill patients. We gathered clinical, biochemical, and BIA data from 66 critically ill patients admitted to an intensive care unit. Patients were divided into three nutritional status groups according to their serum albumin level and total lymphocyte counts. The BIA results, conventional indicators of nutrition status, and clinical outcomes were compared and analyzed retrospectively. Results showed that the BIA indices including phase angle (PhA), extracellular water (ECW), and ECW/total body water (TBW) were significantly associated with the severity of nutritional status. Particularly, PhA, an indicator of the health of the cell membrane, was higher in the well-nourished patient group, whereas the edema index (ECW/TBW) was higher in the severely malnourished patient group. PhA was positively associated with albumin and ECW/TBW was negatively associated with serum albumin, hemoglobin, and duration of mechanical ventilation. In non-survivors, PhA was significantly lower and both ECW/TBW and %TBW/fat free mass were higher than in survivors. In conclusion, several BIA indexes including PhA and ECW/TBW may be useful for nutritional assessment and represent significant prognostic factors in the care of critically ill patients.
Background/objectives:
The association of bioimpedance phase angle (PA), as a measure of nutritional status, with muscle function, health-related quality of life (QoL) and subsequent clinical outcomes in maintenance hemodialysis (MHD) patients.
Subjects/methods:
A 2-year prospective observational study on 250 MHD outpatients (36.8% women) with a mean age of 68.7±13.6 years. Prospective all-cause and cardiovascular (CV) hospitalization and mortality, malnutrition-inflammation score (MIS), handgrip strength (HGS), bioimpedance and short form 36 (SF-36) QoL scores were the study's measurements.
Results:
Across the three PA tertile groups, HGS was incrementally higher in the higher PA tertiles (P<0.001), maintaining this order in both male (r=0.38, P<0.001) and female patients (r=0.36, P<0.001). Better self-reported QoL was noted with higher PA values. This trend was prominent in total score (P<0.001), mental health (P=0.005) and physical health (P<0.001) dimensions, and in most of the SF-36 scales. For each 1° increase in baseline PA, the first hospitalization hazard ratio (HR) was 0.79 (95% confidence interval (CI), 0.68-0.91) and first CV event HR was 0.70 (95% CI, 0.52-0.95); all-cause death HR was 0.63 (95% CI, 0.48-0.81) and CV death HR was 0.64 (95% CI, 0.44-0.91). Associations between PA and morbidity risk continued to be significant after adjustments for various confounders, but the association between PA and mortality risk was abolished after adding MIS to the multivariable model.
Conclusions:
For the MHD population, PA emerged as a useful predictor for impaired muscle function, health-related Qol, upcoming hospitalizations and mortality.
Bioelectrical impedance vector analysis (BIVA) is a new method that is used for the routine monitoring of the variation in body fluids and nutritional status with assumptions regarding body composition values. The aim of the present study was to determine bivariate tolerance intervals of the whole-body impedance vector and to describe phase angle (PA) values for healthy term newborns aged 7-28 d. This descriptive cross-sectional study was conducted on healthy term neonates born at a low-risk public maternity. General and anthropometric neonatal data and bioelectrical impedance data (800 μA-50 kHz) were obtained. Bivariate vector analysis was conducted with the resistance-reactance (RXc) graph method. The BIVA software was used to construct the graphs. The study was conducted on 109 neonates (52.3% females) who were born at term, adequate for gestational age, exclusively breast-fed and aged 13 (SD 3.6) d. We constructed one standard, reference, RXc-score graph and RXc-tolerance ellipses (50, 75 and 95%) that can be used with any analyser. Mean PA was 3.14 (SD 0.43)° (3.12 (SD 0.39)° for males and 3.17 (SD 0.48)° for females). Considering the overlapping of ellipses of males and females with the general distribution, a graph for newborns aged 7-28 d with the same reference tolerance ellipse was defined for boys and girls. The results differ from those reported in the literature probably, in part, due to the ethnic differences in body composition. BIVA and PA permit an assessment without the need to know body weight and the prediction error of conventional impedance formulas.
A method which involves the measurement of bioelectrical resistive impedance (R) for the estimation of human body composition is described. This method is based upon the principle that the electrical conductivity of the fat-free tissue mass (FFM) is far greater than that of fat. Determinations of R were made in 37 healthy men aged 28.8 +/- 7.1 yr (mean +/- SD) using an electrical impedance plethysmograph with a four electrode arrangement that introduces a painless signal (800 microA at 50 kHz) into the body. FFM was assessed by hydrodensitometry and ranged from 44.6-98.1 kg. Total body water (TBW) determined by D2O dilution and total body potassium (TBK) from whole body counting were 50.6 +/- 10.3 L and 167.5 +/- 38.1 g, respectively. Test-retest correlation coefficient was 0.99 for a single R measurement and the reliability coefficient for a single R measurement over 5 days was 0.99. Linear relationships were found between R values and FFM (r = -0.86), TBW (r = -0.86), and TBK (r = -0.79). Significant (p less than 0.01) increases in the correlation coefficients were observed when the predictor Ht2/R was regressed against FFM (r = 0.98), TBW (r = 0.95), AND TBK (r = 0.96). These data indicate that the bioelectrical impedance technique is a reliable and valid approach for the estimation of human body composition. This method is safe, noninvasive, provides rapid measurements, requires little operator skill and subject cooperation, and is portable. Further validation of this method is recommended in subjects with abnormal body composition.
Kidney International aims to inform the renal researcher and practicing nephrologists on all aspects of renal research. Clinical and basic renal research, commentaries, The Renal Consult, Nephrology sans Frontieres, minireviews, reviews, Nephrology Images, Journal Club. Published weekly online and twice a month in print.
There is a lack of strong evidence on the effectiveness of the content, frequency, and timing of visits in standard antenatal-care programmes. We undertook a systematic review of randomised trials assessing the effectiveness of different models of antenatal care. The main hypothesis was that a model with a lower number of antenatal visits, with or without goal-oriented components, would be as effective as the standard antenatal-care model in terms of clinical outcomes, perceived satisfaction, and costs.
Phase angle is an indicator based on reactance and resistance obtained from bioelectrical impedance analysis (BIA). Although its biological meaning is still not clear, phase angle appears to have an important prognostic role.
The aim of this study was to estimate population averages and SDs of phase angle that can be used as reference values.
BIA and other methods used to evaluate body composition, including hydrodensitometry and total body water, were completed in 1967 healthy adults aged 18-94 y. Phase angle was calculated directly from body resistance and reactance, and fat mass (FM) was estimated from the combination of weight, hydrodensitometry, and total body water by using the 3-compartment Siri equation. Phase angle values were compared across categories of sex, age, body mass index (BMI), and percentage FM.
Phase angle was significantly (P < 0.001) smaller in women than in men and was lower with greater age (P < 0.001). Phase angle increased with an increase in BMI and was significantly inversely associated with percentage fat in men. Phase angle was significantly predicted from sex, age, BMI, and percentage FM in multiple regression models.
Phase angle differs across categories of sex, age, BMI, and percentage fat. These reference values can serve as a basis for phase angle evaluations in the clinical setting.
Background: Phase angle is an indicator based on reactance and resistance obtained from bioelectrical impedance analysis (BIA). Although its biological meaning is still not clear, phase angle appears to have an important prognostic role.
Objective: The aim of this study was to estimate population averages and SDs of phase angle that can be used as reference values.
Design: BIA and other methods used to evaluate body composition, including hydrodensitometry and total body water, were completed in 1967 healthy adults aged 18–94 y. Phase angle was calculated directly from body resistance and reactance, and fat mass (FM) was estimated from the combination of weight, hydrodensitometry, and total body water by using the 3-compartment Siri equation. Phase angle values were compared across categories of sex, age, body mass index (BMI), and percentage FM.
Results: Phase angle was significantly (P < 0.001) smaller in women than in men and was lower with greater age (P < 0.001). Phase angle increased with an increase in BMI and was significantly inversely associated with percentage fat in men. Phase angle was significantly predicted from sex, age, BMI, and percentage FM in multiple regression models.
Conclusions: Phase angle differs across categories of sex, age, BMI, and percentage fat. These reference values can serve as a basis for phase angle evaluations in the clinical setting.
Purpose:
A high phase angle measured by the Nutriguard(®) bioelectrical impedance analysis device is associated with a reduced mortality risk in older people. This retrospective study aims to analyze whether this association persists with the other devices that have been used in our hospital.
Methods:
This study encompasses all people 65 yrs and older who underwent a phase angle measurement between 1990 and 2011 at the Geneva University Hospitals, with the RJL-101(®) (RJL Systems), Xitron 4000B(®) (Xitron Technologies), Eugedia(®) (Eugédia-Spengler) and Bio-Z(®) (Spengler). Diseases at the time of phase angle measurement were reported in the form of the Cumulative Illness Rating Scale. Date of death was retrieved until December 2012. Phase angle values were categorized into sex- and device-specific quartiles, where quartile 1 represents the lowest quartile and reference value. Cox regressions were performed to evaluate the association between phase angle quartiles and mortality.
Results:
We considered 1878 people (969 women), of whom 1151 had died. In univariate sex-specific Cox regressions, the death risk decreased progressively as the phase angle quartile measured by the Bio-Z(®) or RJL-101(®) increased. The HR (95% CI) in quartile 4 was 0.36 (0.26, 0.50) and 0.38 (0.29, 052) in women and men measured with the Bio-Z(®) (both p < 0.001), and 0.23 (0.14, 0.39) and 0.19 (0.10, 0.36) in women and men measured with the RJL-101(®) (both p < 0.001). The association between phase angle and mortality persisted when adjusted for age, body mass index or co-morbidities. The small number of deaths in people who underwent a measurement by Eugedia(®) (n = 93) or Xitron 4000B(®) (n = 56) did not allow performing multivariate Cox regressions.
Conclusions:
Phase angle quartiles are associated with mortality in people aged ≥65 years when using the RJL-101(®) or Bio-Z device(®).
The aim of this study was to verify the relationship between weight loss, handgrip strength (HGS) and phase angle (PA) before the beginning of chemotherapy with overall survival in cancer patients. Patients diagnosed with gastrointestinal and breast cancer who were over 18 years old and were scheduled to undergo adjuvant treatment at Hospital Borges da Costa/Brazil were evaluated. The exclusion criteria were neoadjuvant treatment, patients with kidney and liver disease and using diuretics. Weight, HGS and PA tests were performed by trained dietitians. The Kaplan-Meier survival method and the log-rank test, cox regression and ROC curve were used and p < 0.05 was considered significant. Two-hundred and twenty-eight patients were evaluated.The median survival time was higher among the patients who showed weight loss of less than 10% of usual body weight (p < 0.05). Regarding HGS, patients with decreased HGS had a 22.0 month survival versus 34.2 months for those with normal values (p < 0.05). 146 patients had normal PA values, and these patients had increased survival time compared to those with inappropriate values (p < 0.05). In the Cox regression, weight loss and PA were predictors of mortality, HGS wasn't significantly associated with mortality. ROC analysis revealed that weight loss was the nutritional status parameter with the most predictive power.
Background: Malnutrition is a frequent complication of cirrhosis and it has been associated to more severe disease and development of complications. Phase angle is a bedside reliable tool for nutritional assessment based on conductivity properties of body tissues. Aim: To evaluate the association between malnutrition assessed through phase angle and mortality in patients with liver cirrhosis. Methods: We performed a prospective cohort study in a tertiary care centre; 249 patients were enrolled with 48 months of follow-up. Clinical, nutritional (malnutrition=phase angle≤4.9°) and biochemical evaluations were performed. Student's t-test and χ2 method were used as appropriate. Kaplan-Meier curves and multivariate Cox regression were used to evaluate mortality. Results: Mean follow-up was 33.5 months. Survival analysis showed higher mortality in the malnourished group compared to the well-nourished group (. p=. 0.076), Kaplan-Meier curves were further stratified according to compensated and decompensated status showing higher mortality in compensated patients according to Child-Pugh (. p=. 0.002) and Model for End-Stage Liver Disease score (. p=. 0.008) when malnutrition was present. Multivariate analysis showed that malnutrition was independently associated with mortality (HR. =. 2.15, 1.18-3.92). Conclusions: In our cohort, malnutrition was independently associated with mortality. This is the first study showing higher mortality in malnourished compensated cirrhotic patients.
Background & aims:
This study determined the association between phase angle (PhA), by bioelectrical impedance analysis (BIA) and nutritional risk by Nutritional Risk Screening (NRS-2002), Subjective Global Assessment (SGA), hospital length of stay (LOS) and 30 day non-survival in patients at hospital admission compared to healthy controls.
Methods:
PhA was determined by BIA in patients (n = 983, 52.7 ± 21.5 yrs, M 520) and compared to healthy age-, sex- and height-matched controls. Low PhA was set at <5.0° (men) and <4.6° (women) as previously determined (Kyle, in press).
Results:
PhA was lower in patients (men 6.0 ± 1.4°, women 5.0 ± 1.3°) than controls (men 7.1 ± 1.2°, women 6.0 ± 1.2°, un-paired t-test p < 0.001). Patients were more likely to have low PhA than controls: NRS-2002: no risk (relative risk (RR) 1.7, 95th confidence interval (CI) 1.2-2.3), moderate risk (RR 4.5, CI 3.4-5.8) and severe risk (RR 7.5, CI 5.9-9.4); similar results were obtained by SGA; LOS ≥21 days (RR 6.9, CI 5.1-9.1) and LOS 5-20 days (RR 5.2, CI 3.9-6.9) and non-survivors (RR 3.1, CI 2.1-3.4) compared to survivors.
Conclusions:
There is a significant association between low PhA and nutritional risk, LOS and non-survival. PhA is helpful to identify patients who are at nutritional risk at hospital admission in order to limit the number of in-depth nutritional assessments.
Background & aims:
The use of phase angle (PhA) and raw parameters of bioelectrical impedance analysis (BIA) has gained attention as alternative to conventional error-prone calculation of body composition in disease. This review investigates the clinical relevance and applicability of PhA and Bioelectrical Impedance Vector Analysis (BIVA) which uses the plot of resistance and reactance normalized per height.
Methods:
A comprehensive literature search was conducted using Medline identifying studies relevant to this review until March 2011. We included studies on the use of PhA or BIVA derived from tetrapolar BIA in out- and in-patient settings or institutionalized elderly.
Results:
Numerous studies have proven the prognostic impact of PhA regarding mortality or postoperative complications in different clinical settings. BIVA has been shown to provide information about hydration and body cell mass and therefore allows assessment of patients in whom calculation of body composition fails due to altered hydration. Reference values exist for PhA and BIVA facilitating interpretation of data.
Conclusion:
PhA, a superior prognostic marker, should be considered as a screening tool for the identification of risk patients with impaired nutritional and functional status, BIVA is recommended for further nutritional assessment and monitoring, in particular when calculation of body composition is not feasible.
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 50 kHz 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.
There is currently no criterion standard to assess nutritional status, and different methods have been used in hospitalized patients. The aim of this study was to investigate the agreement and the association between bioelectrical impedance analysis derived by standardized phase angle (SPA) and other methods used for the nutritional assessment of body composition, metabolic status, and functional status in surgical patients. The hypothesis was that the SPA is effective for evaluating nutritional status in surgical patients; therefore, it could be used when the application of other assessment methods is not possible. The sample consisted of 125 patients (20-94 years of age) before elective gastrointestinal or hernia repair. The participants were from the Surgical Clinic 1 at the University Hospital of the Federal University of Santa Catarina, Florianópolis, SC, Brazil. Nutritional status was evaluated during the preoperative period based on the triceps skinfold thickness, mid-arm circumference, body mass index, percent weight loss, nutritional risk screening 2002 (NRS 2002), subjective global assessment (SGA), and SPA. The agreement between the SPA and the other methods was assessed with the k coefficient. The agreement between the SPA and the methods of nutritional assessment that were investigated for diagnosing malnutrition was moderate for NRS 2002 and SGA, weak for percent weight loss, and poor for triceps skinfold thickness, mid-arm circumference, and body mass index. There was a significant association between SPA and both NRS 2002 and SGA (P < .001). Our results suggest that SPA is able to indicate the risk of nutritional deficiency in the patients assessed. However, good agreement between SPA and the methods investigated was not observed.
Detecting young children with high amount of body fat is important to intervene in the development of obesity. The aim of this study is to gain inside in the bioelectrical impedance vector analysis in healthy infants.
Repeated measurements of whole body reactance and resistance were assessed, using a 50kHz frequency bioelectrical impedance analysis, in 51 boys and 62 girls during infancy. Bivariate vector analysis, which can be used to determine tissue hydration and soft tissue mass, was conducted. The 95% confidence intervals of the mean vectors for different age groups and the 95%, 75% and 50% tolerance intervals were plotted, using resistance and reactance components standardized by the participant's height.
During infancy impedance vectors changed significantly: A vector migration of the Xc/H of 8.50ohm/m and the R/H of -95.68ohm/m between the age of two months and eight to twelve months (p=0.0001) was observed. Bivariate, reference tolerance intervals of the impedance vectors for healthy infants at the age of two months are presented.
Our results show a significant impedance vector migration during the first year of life. New reference tolerance intervals for the second month of life were constructed.
Whole-body bioelectrical impedance analysis (BIA) is widely used by researchers and clinicians as a noninvasive and safe method to estimate body composition and body water volume in children and adults. Development of new approaches, such as segmental and multifrequency analyzers, should greatly expand the utility of this electrical technique. This article reviews the principles, underlying assumptions, clinical applications and future directions of the BIA method.
To develop a current national fetal growth curve that can be used as a common reference point by researchers to facilitate investigations of the predictors and consequences of small and large for gestational age delivery.
Single live births to United States resident mothers in 1991 (n = 3,134,879) were used for the development of this curve, which was compared with four previously published fetal growth curves. Techniques were developed to address cases with implausible birth weight-gestational age combinations and to smooth fetal growth curves across gestational age categories.
In general, the previously published fetal growth curves underestimated the 1991 United States reference curve. This underestimation is most apparent during the latter weeks of gestation, approximately 33-38 weeks.
Our findings indicate that the prevalence of fetal growth restriction (FGR) will vary markedly, depending on the fetal growth curve used. Furthermore, many previously published fetal growth curves no longer provide an up-to-date reference for describing the distribution of birth weight by gestational age and for determining FGR that is consistent with the most recent live birth data for the entire United States.
The 1994 National Institutes of Health Technology Conference on bioelectrical impedance analysis (BIA) did not support the use of BIA under conditions that alter the normal relationship between the extracellular (ECW) and intracellular water (ICW) compartments. To extend applications of BIA to these populations, we investigated the accuracy and precision of seven previously published BIA models for the measurement of change in body water compartmentalization among individuals infused with lactated Ringer solution or administered a diuretic agent. Results were compared with dilution by using deuterium oxide and bromide combined with short-term changes of body weight. BIA, with use of proximal, tetrapolar electrodes, was measured from 5 to 500 kHz, including 50 kHz. Single-frequency, 50-kHz models did not accurately predict change in total body water, but the 50-kHz parallel model did accurately measure changes in ICW. The only model that accurately predicted change in ECW, ICW, and total body water was the 0/infinity-kHz parallel (Cole-Cole) multifrequency model. Use of the Hanai correction for mixing was less accurate. We conclude that the multifrequency Cole-Cole model is superior under conditions in which body water compartmentalization is altered from the normal state.
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.
Bioelectrical impedance analysis (BIA) is a quick and noninvasive method for estimating body composition. Many prediction equations have been reported recently using bioelectrical impedance to calculate fat free mass (FFM) and fat mass (FM). These equations are based on the assumption that the composition and density of FFM are stable. In children, the composition and density of FFM vary according to age and clinical state, so the use of these equations is limited. However, phase angle is directly determined from resistance (Rz) and reactance (Xc) without equations and reflects body cell mass. The authors, therefore, investigated the validity of phase angle for nutritional assessment in children.
Bioelectrical impedance analysis and anthropometric measurements were performed in 81 patients, including 71 well-nourished and 10 malnourished children.
Phase angle correlated with body weight (R = 0.818) and arm muscle circumference (r = 0.901) in well-nourished children. Malnourished patients showed lower phase angle than that of well-nourished children.
Bioelectrical impedance phase angle is a useful parameter for nutritional assessment in children.
Highly active antiretroviral treatment (HAART) reduces the risk of wasting in HIV infection and may alter the prognostic weight of wasting. The phase angle from bioelectrical impedance analysis (BIA) can be interpreted as a surrogate marker for the catabolic reaction to chronic HIV infection and opportunistic disease.
Our objective was to assess the prognostic ability of the phase angle in HIV-infected patients in the era of HAART.
Two cross-sectional observation studies were conducted in 1996 and 1997 at a German university outpatient HIV clinic. In the 1996 and 1997 cohorts, HAART was prescribed to 17 of 212 and 168 of 257 patients at baseline and to 179 of 212 and 234 of 257 patients during observation, respectively. Whole-body BIA was assessed at 50 KHz. Time to clinical progression and survival were calculated by using Cox proportional hazard models with time-dependent covariates. Median observation times were 1000 and 515 d for the 1996 and 1997 cohorts, respectively.
Higher phase angle was associated with a lower relative mortality risk, adjusted for viral load and CD4(+) cell count, of 0.49 (95% CI: 0.30, 0.81) per degree in 1996 and of 0.33 (95% CI: 0.18, 0.61) in 1997. The influence of phase angle on time to clinical progression, adjusted for viral load and CD4(+) cell count, was not significant in 1996 but the relative risk was 0.58 (0.36, 0.83) in 1997.
Despite the favorable effects of HAART on the nutritional status of HIV-infected persons, low phase angle remains an independent adverse prognostic marker of clinical progression and survival.
To generate reference ranges for bioelectrical impedance indices throughout pregnancy and to investigate whether a relationship exists between these indices and the neonatal birth weight.
Pregnant women with a singleton gestation, gestational age lower than 12 weeks, and absence of medical diseases before pregnancy were enrolled. Patients with pregnancy complications, such as hypertensive disorders, diabetes, and antiphospholipides syndrome were excluded. Antrophometric maternal parameters and bioelectrical impedance measurements were performed during the first, second, third trimester of pregnancy, at delivery and 60 days after delivery. Height(2)/resistance (cm(2)/Omega) and height(2)/reactance (cm(2)/Omega) were utilized to estimate the total and extracellular body water amounts, respectively. Spearman rank correlations and cox proportional hazard modelling were used for statistical purposes.
169 patients completed all measurements. Total and extracellular water amounts significantly increase as pregnancy advances and return to the pre-pregnancy values within 60 days after delivery. After adjustment for gestational age at delivery, fetal sex, and smoking habits, height(2)/resistance at 25 weeks (hazard=1.04, 95% confidence interval (CI) 1.02-1.06, P<0.005), height(2)/resistance at 30 weeks (hazard=1.03, 95% CI 1.01-1.05, P<0.005), height(2)/reactance at 20 weeks (hazard=1.03,95% CI 1.01-1.05, P<0.005), and height(2)/reactance at 25 weeks (hazard=1.03, 95% CI 1.01-1.04, P<0.01) were found to be independent predictors of birth weight.
We have provided reference ranges for bioimpedance analysis during pregnancy, an easy, fast and non invasive method to estimate the body water composition during pregnancy. Bioelectrical impedance indices during the second trimester of pregnancy are independently related to the birth weight.
To determine the reference, bivariate, tolerance intervals of the whole-body impedance vector for healthy white neonates, we performed an observational, cross-sectional study in two university hospitals.
The impedance vector (standard, tetrapolar analysis at 50-kHz frequency) was measured in 163 consecutive subjects (87 boys and 76 girls) with postnatal ages of 1 to 7 d. Bivariate vector analysis was conducted with the resistance-reactance (RXc) 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 R and Xc components standardized by the subject's crown-to-heel length (height). Mean vectors from the groups (1, 2, and 3 to 7 d) with overlapping 95% confidence ellipses were considered representative of only one age class of 1 to 7 d. The impedance vector distribution of neonates also was compared with healthy white children (1014 boys and 1030 girls, age 2-15 y) and adult subjects (354 men and 372 women, age 15-85 y) from the same geographic area. There was a definite, progressive, vector shortening from birth, through ages 2 to 15 y, toward the adults' vector position.
We established the reference, bivariate, 95%, 75%, and 50% tolerance intervals of the impedance vector in the first postnatal week for healthy white neonates, with which the vectors from infants with altered body composition can be tested (free software is available from apiccoli@ unipd.it).
The use of bioelectrical impedance analysis (BIA) is widespread both in healthy subjects and patients, but suffers from a lack of standardized method and quality control procedures. BIA allows the determination of the fat-free mass (FFM) and total body water (TBW) in subjects without significant fluid and electrolyte abnormalities, when using appropriate population, age or pathology-specific BIA equations and established procedures. Published BIA equations validated against a reference method in a sufficiently large number of subjects are presented and ranked according to the standard error of the estimate. The determination of changes in body cell mass (BCM), extra cellular (ECW) and intra cellular water (ICW) requires further research using a valid model that guarantees that ECW changes do not corrupt the ICW. The use of segmental-BIA, multifrequency BIA, or bioelectrical spectroscopy in altered hydration states also requires further research. ESPEN guidelines for the clinical use of BIA measurements are described in a paper to appear soon in Clinical Nutrition.
BIA is easy, non-invasive, relatively inexpensive and can be performed in almost any subject because it is portable. Part II of these ESPEN guidelines reports results for fat-free mass (FFM), body fat (BF), body cell mass (BCM), total body water (TBW), extracellular water (ECW) and intracellular water (ICW) from various studies in healthy and ill subjects. The data suggests that BIA works well in healthy subjects and in patients with stable water and electrolytes balance with a validated BIA equation that is appropriate with regard to age, sex and race. Clinical use of BIA in subjects at extremes of BMI ranges or with abnormal hydration cannot be recommended for routine assessment of patients until further validation has proven for BIA algorithm to be accurate in such conditions. Multi-frequency- and segmental-BIA may have advantages over single-frequency BIA in these conditions, but further validation is necessary. Longitudinal follow-up of body composition by BIA is possible in subjects with BMI 16-34 kg/m(2) without abnormal hydration, but must be interpreted with caution. Further validation of BIA is necessary to understand the mechanisms for the changes observed in acute illness, altered fat/lean mass ratios, extreme heights and body shape abnormalities.
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.
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.
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.
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).
We carried out a cross-sectional study of 115 healthy infants, younger than 6 months old, exclusively breast-fed or formula-fed, to investigate correlations between circulating leptin concentrations and body composition measurements. Serum leptin was evaluated with radioimmunoassay, and body composition with bioelectrical impedance analysis. Multiple regression analysis showed a relationship between serum leptin and body mass index in the entire study population (P = 0.042). There was a significant negative relationship between serum leptin and phase angle (P = 0.006) in formula-fed infants. Serum leptin was positively related to subscapular skinfold thickness (P = 0.055) and negatively to reactance (P = 0.057) only in formula-fed infants, although the differences were just below significance. Serum leptin concentration was higher in breast-fed infants (P = 0.002), and was not correlated with body composition parameters. This study indicates that there is a relation between leptin and infant body composition in the first months of life, although the link needs to be explored further.
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