应用生物电阻抗法分析人体组成

目的：通过应用生物电阻抗法测定人体组成,探讨其对营养评价的临床意义。方法：利用生物电阻抗法测定７６例健康志愿者的人体组成。结果：男性体脂占体重的（１４．８１±４．８９）％,女性体脂则占体重的（２２．３３±５．５８）％,女性体脂含量明显大于男性（Ｐ＜０．０５）。随年龄增长,可出现体脂增加而瘦组织群减少的趋势。应用生物电阻抗法测定体脂含量,其肥胖检出率明显低于按理想体重法和体质指数（ＢＭＩ）法的检出率。结论：生物电阻抗法测定人体组成简便、准确,有助于临床客观地评价机体营养状况。     

Body composition analysis in critically ill survivors: a comparison of bioelectrical impedance spectroscopy devices

Background: Body composition is commonly altered in response to critical illness and can be estimated at the bedside with bioelectrical impedance spectroscopy (BIS). Different electrode configurations may be used to mitigate assumptions of the technique, but the reliability of tetra‐polar and octo‐polar arrangements has yet to be established. This study aimed to compare both configurations, in a prospective observational study of 17 critically ill survivors and 12 healthy controls. Methods: Weight, supine body length, and BIS on both tetra‐polar and octo‐polar configured devices were recorded, then repeated 2 days later. Bioelectrical impedance vector analysis was subsequently performed using data from the tetra‐polar device at a frequency of 50 kHz. Results: Test‐retest agreement was acceptable for the tetra‐polar device (intraclass correlation coefficient range, patients: 0.876–0.988 vs controls: 0.983–0.998, P ≤ 0.001). However, lower and wider ranging test‐retest intraclass correlation coefficients were obtained with the octo‐polar instrument in both groups. Furthermore, there was a difference in the mass/volume of body compartments measured on each device in both patients (P ≤ .017) and controls (P ≤ .045). A change in the composition profile of critically ill males was evident between measurement occasions, which was reflected by a reduction in body weight of 1.6 (1.5) kg (P ≤ 0.001) across the sample over the same period. Conclusions: BIS devices should not be used interchangeably in the clinical setting. The reliability of the tetra‐polar instrument was good, but daily fluctuations in body weight may have affected the results.     

Comparing single-frequency bioelectrical impedance analysis against deuterium dilution to assess total body water

Background/Objectives:In this study, we aimed to validate the accuracy of single-frequency bioelectrical impedance analysis (SF-BIA) at 50?kHz to assess total body water (TBW) against the reference technique deuterium dilution (D(2)O) and to explore if the simple clinical parameters extracellular fluid (ECF) composition and body shape explain individual differences between D(2)O and SF-BIA (Diff(BIA-D(2)O)).Subjects/Methods:We assessed TBW with D(2)O and SF-BIA in 26 women and 26 men without known disease or anomalous body shapes. In addition, we measured body shape with anthropometry and ECF composition (osmolality, albumin, glucose, urea, creatinine, sodium and potassium).Results:On group average, SF-BIA to predict TBW agreed well with D(2)O (SF-BIA, 39.8±10.1?l; D(2)O, 40.4±10.2?l; and Diff(BIA-D(2)O) -0.7?l). In four individuals ('outliers'; 15% of the study population), Diff(BIA-D(2)O) was high (-6.8 to +3.8?l). Diff(BIA-D(2)O) was associated with individual variations in body shape rather than ECF composition. Using gender-specific analysis, we found that individual variability of waist circumference in men and arm length in women significantly contributed to Diff(BIA-D(2)O). When removing the four 'outliers', these associations were lost.Conclusions:In the majority of our sample, BIA agreed well with D(2)O. Adjusting for individual variability in body shape by anthropometrical assessment could possibly improve the accuracy of SF-BIA for individuals who deviate from mean values with respect to body shape. However, further studies with higher subject numbers are needed to confirm our findings.     

Body water distribution in severe obesity and its assessment from eight-polar bioelectrical impedance analysis

OBJECTIVE: To measure body water distribution and to evaluate the accuracy of eight-polar bioelectrical impedance analysis (BIA) for the assessment of total body water (TBW) and extracellular water (ECW) in severe obesity. DESIGN: Cross-sectional study. SETTING: Obesity clinic. SUBJECTS: In all, 75 women aged 18-66 y, 25 with body mass index (BMI) between 19.1 and 29.9 kg/m(2) (ie not obese), 25 with BMI between 30.0 and 39.9 kg/m(2) (ie class I and II obese), and 25 with BMI between 40.0 and 48.2 kg/m(2) (ie class III obese). METHODS: TBW and ECW were measured by (2)H(2)O and Br dilution. Body resistance (R) was obtained by summing the resistances of arms, trunk and legs as measured by eight-polar BIA (InBody 3.0, Biospace, Seoul, Korea). The resistance index at a frequency of x kHz (RI(x)) was calculated as height (2)/R(x). RESULTS: ECW : TBW was similar in women with class III (46+/-3%, mean+/-s.d.) and class I-II obesity (45+/-3%) but higher than in nonobese women (39+/-3%, P<0.05). In a random subsample of 37 subjects, RI(500) explained 82% of TBW variance (P<0.0001) and cross-validation of the obtained algorithm in the remaining 38 subjects gave a percent root mean square error (RMSE%) of 5% and a pure error (PE) of 2.1 l. In the same subjects, RI(5) explained 87% of ECW variance (P<0.0001) and cross-validation of the obtained algorithm gave a RMSE% of 8% and a PE of 1.4 l. The contribution of weight and BMI to the prediction of TBW and ECW was nil or negligible on practical grounds. CONCLUSIONS: ECW : TBW is similar in women with class I-II and class III obesity up to BMI values of 48.2 kg/m(2). Eight-polar BIA offers accurate estimates of TBW and ECW in women with a wide range of BMI (19.1-48.2 kg/m(2)) without the need of population-specific formulae.     

Body composition assessment in adults with cystic fibrosis: comparison of dual-energy X-ray absorptiometry with skinfolds and bioelectrical impedance analysis

OBJECTIVE: We compared body composition measurement in adults with cystic fibrosis (CF) by using non-invasive methods (skinfold thicknesses and bioelectrical impedance analysis [BIA]) with dual-energy X-ray absorptiometry (DXA). METHODS: Seventy-six adults with CF (mean age 29.9 +/- 7.9 y, mean body mass index 21.5 +/- 2.5 kg/m(2)) were studied. Body composition was measured to calculate fat-free mass (FFM) using DXA, the sum of four skinfold thicknesses, and BIA (predictive equations of Lukaski and of Segal). RESULTS: Mean FFM values +/- standard deviation measured using DXA were 54.8 +/- 7.3 kg in men and 41.2 +/- 3.9 kg in women. Mean FFM values measured using BIA/Lukaski were 51.5 +/- 7.8 kg in men and 40.4 +/- 4.9 kg in women (P < 0.0005 for men, not significant for women for comparison with DXA). Mean FFM values measured using BIA/Segal were 54.2 +/- 7.5 kg for men and 44.1 +/- 5.9 kg for women (not significant for men, P < 0.0005 for women for comparison with DXA). Mean FFM values measured using skinfolds were significantly higher than those for FFM with DXA (57.2 +/- 7.2 kg in men, 43.3 +/- 4.3 kg in women, P < 0.0005 for comparison with DXA). The 95% limits of agreement with FFM using DXA were, for men and women, respectively, -8.3 to 1.7 kg and -6.4 to 4.8 kg for BIA/Lukaski, -4.8 to 3.6 kg and -3.1 to 8.9 kg for BIA/Segal, and -2.8 to 7.3 kg and -1.5 to 5.7 kg for skinfolds. CONCLUSION: This study suggests that skinfold thickness measurements and BIA will incorrectly estimate FFM in many adults with CF compared with DXA measurements of FFM. These methods have limited application in the assessment of body composition in individual adult patients with CF.     

Body composition in underweight elderly subjects: reliability of bioelectrical impedance analysis

BACKGROUND AND AIMS: In underweight elderly subjects it is important to estimate body composition and particularly fat-free mass (FFM). Bioelectrical impedance analysis (BIA) is a non-invasive method in determining FFM, but its usefulness in these frail subjects should be verified. The aim of this study is to verify in underweight elderly people the reliability of previously published BIA formulas in detecting FFM. METHODS: Fifty-seven hospitalized elderly subjects (27 males and 30 females) with body mass index <20 kg/m(2) were selected. In all subjects, FFM was detected by dual energy X-ray absorptiometry. Moreover, BIA measurements were performed at standard frequency (50 kHz and 800 microA) and FFM was derived using the main previous published BIA equations. Results: In men, Kyle and Rising equations gave acceptable estimates of FFM with a mean error, respectively, of 1+/-1.9 and 1.4+/-1.7 kg. Also RJL formula could be used after adjusting for a correction factor. In women, no equation seemed sufficiently reliable to estimate FFM. CONCLUSIONS: BIA method seems useful to evaluate body composition in underweight elderly men but it seems to have intrinsic limits in women. Nevertheless, the variability in behavior of the different equations suggests to be careful in adopting BIA equations.     

Body composition of Cameroonian lactating women determined by anthropometry, bioelectrical impedance, and deuterium dilution

Objective

This study compared body composition estimates using deuterium dilution, multiple-frequency bioelectrical impedance analysis (BIA), and skinfold thickness techniques in a group of Cameroonian lactating women.

Methods

Body fat, fat-free mass, and total body water in 44 Cameroonian lactating women (2.63 ± 1.31 mo postpartum) were assessed by deuterium dilution, the Siri or black-specific derived Durnin-Womerley equation, and 12 BIA-prediction equations developed in samples of subjects of white, black, black-and-white, or unspecified racial background, respectively.

Results

Compared with deuterium dilution, anthropometry and BIA-based predictive equations overestimated body fat by 2.7 to 11.7 kg; thus, fat-free mass and total body water were underestimated. In all cases, the significant biases resulted in large 95% limits of agreement, yielding unacceptable potential bias at the level of the individual. However, the exclusion of suprailiac skinfold in the calculation, yielding to non-significant (P < 0.05) bias, improved the prediction of body composition in Cameroonian lactating women using the Durnin-Womersley and Siri equations.

Conclusion

It is essential to adjust the Durnin-Womersley equation before using it in the Siri equation for the prediction of body composition in lactating women. Further development and cross-validation of prediction equations from BIA specific to lactating women is needed.     

Total body water measurement using bioelectrical impedance analysis, isotope dilution and total body potassium: a scoring system to facilitate intercomparison

OBJECTIVES: (1) To develop a scale that is useful in evaluating the accuracy of multifrequency bioelectrical impedance analysis (MF-BIA) in the assessment of body water volumes against the accepted gold standard measurements based on isotope-dilution and total body potassium (TBK). (2) To perform a pilot test of the scale. DESIGN: A scale was developed to evaluate the accuracy of MF-BIA in the assessment of body water volumes. Questions were obtained from reading the scientific literature and discussions involving the four authors. Three of these and two additional independent readers pre-tested the scale. A weighting was identified for each question and a pilot test with a sample of 10 articles (different to those used for the questionnaire performance) was conducted. A further validation was carried out with a second set of 20 articles and two additional independent readers. RESULTS: The kappa statistic expressing the level of agreement between pairs of the first three authors using this scale with 10 articles, was 0.3, 0.4 and 0.6 after the first attempt. A second evaluation after specific changes improved the agreement to 0.8, 0.6 and 0.8. The mean score for 10 articles was 252+/-36 points from a total score of 400 (63+/-9%). The evaluation with the second set of 20 articles resulted in a kappa of 0.7 from two pairs of authors. The evaluation with two additional reviewers resulted in a kappa=0.7. CONCLUSION: A tool has been developed to assess the accuracy of the MF-BIA technique and to identify methodological components, plan future studies and critically evaluate data in this area. It is likely that this tool may also be used to assess the accuracy of single frequency studies.     

Estimation of total body water by bioelectrical impedance analysis

Total body water (TBW) measured by bioelectrical impedance analysis (BIA) was directly compared with deuterium-isotope dilution in a total of 58 subjects. First, sex-specific and group equations were developed by multiple regression analysis in (10 each) obese and nonobese men and women. Height/resistive impedance was the most significant variable used to predict deuterium-dilution space (D2O-TBW) and, combined with weight, yielded R = 0.99 and SE of estimate = 1.75 L. Equations predicted D2O-TBW equally well for obese and nonobese subjects. Second, the equations were prospectively tested in a heterogeneous group of 6 males and 12 females. Sex-specific equations predicted D2O-TBW with good correlation coefficients (0.96 and 0.93), total error (2.34 and 2.89 L), and a small difference between mean predicted and measured D2O-TBW (-1.4 +/- 2.05 and -0.48 +/- 2.83 L). BIA predicts D2O-TBW more accurately than weight, height, and/or age. A larger population is required to validate the applicability of our equations.     

生物电阻抗法与双标水稀释法在人体成分测定中的应用比较

目的 用双标水稀释法验证目前在我国广泛应用的体成分测定方法--生物电阻抗法的准确性.方法 从白求恩军医学院某中队150名学员中根据体质指数(BMI)等指标筛选出16名学员作为受试对象,试验期为14 d,试验期间学员集中管理,统一食宿.试验第1天受试者服用双标水,收集服用前及服用后2 h、4 h、6 h、8 h及第2至第14天的尿液,用质谱分析的方法,得到受试者2H、18O的消除曲线,从而获得受试者的体成分数据.与此同时,从试验第1天开始,每天晚餐后3 h用生物电阻抗仪对每位受试者进行体成分的测定.最后,将2种方法获得的体成分数据加以比对.结果 经统计学分析,生物电阻抗法与双标水稀释法获得的体成分参数值差异无统计学意义,而且高度相关,两种方法测得的总体水、瘦体重、体脂及体脂百分比的相关系数分别为0.556,0.556,0.817,0.606,具有统计学意义.结论 应用生物电阻抗法测定中国人体成分具有较高的准确性.     

Total body water and percentage fat mass measurements using bioelectrical impedance analysis and anthropometry in spinal cord-injured patients

BACKGROUND AND AIMS: Spinal cord injured patients may be adversely affected by disturbances of nutritional status, particularly malnutrition and fat mass overload. Malnutrition increases the risk for development of pressure sores, and fat mass excess increases the cardiovascular and respiratory risks of these patients, as well as predisposing to the development of diabetes mellitus, pressures sores and bony fractures. Body impedance analysis and anthopometry are easy bedside methods for body composition assessment. The aims of the study were to validate, in 20 spinal cord injured patients, body impedance analysis as a means to estimate total body water, and to validate a skinfold measurement of percentage fat independent of hydration of fat-free mass in the same population. METHODS: Total body water was measured by (18)O dilution as a reference method. Impedance and anthropometric measurements (four different skinfolds) were obtained. The results of total body water given by impedance analysis and calculated with three formulas were compared to the reference method. The fat mass percentage obtained with each of the skinfolds using the 3-compartment Siri's formula was compared to a reference value using the sum of the skinfolds. RESULTS AND CONCLUSION: The formula using 100 kHz resistance, height, weight and gender overestimated total body water by only 0.76 +/- 1.85 L, with an acceptable concordance with labeled water results. The formula with 50 kHz resistance was less accurate and concordant. Each skinfold may be used for assessing percentage fat mass. Based on these findings, we feel that the triceps skinfold, whose the variability is the lowest compared to the reference values, can be used alone in clinical practice.     

Extracellular water: sodium bromide dilution estimates compared with other markers in patients with acquired immunodeficiency syndrome

Extracellular fluid and closely related extracellular water (ECW) provide information on nutritional status in health and disease. Although various methods exist for ECW determination, little is known about their comparability in patients with wasting diseases such as acquired immunodeficiency syndrome (AIDS). One practical method, the dilution of sodium bromide (NaBr), is used widely in clinical research, although its relationship to other ECW markers has not been well characterized. The present study sought to compare ECW estimates as determined by NaBr and three other methods in 11 male patients with AIDS (mean +/- SD; age, 44+/-12 years; body weight, 64.5+/-8.8 kg; and height, 172+/-4 cm). ECW volumes were determined from NaBr dilution, total body chlorine (TBCl) by delayed gamma-neutron activation analysis, total body water (TBW) by tritium dilution combined with total body potassium (TBK) by whole body 40K counting, and radioactive sulfate dilution (35SO4). All correlations between the NaBr method and other methods were statistically significant (NaBr vs TBCl [r = .91; p < .001]; vs TBW/TBK [r = .76; p < .01]; and vs 35SO4 [r = .89; p < .001]). As expected from previous studies, ECW (L) derived by NaBr provided a group mean (15.1+/-2.2 L) similar to the TBCl method (15.4+/-1.7 L; p = .32), a significantly smaller ECW than by the TBW/TBK method (18.6+/-3.4 L; p = .0004), and a significantly larger ECW than by 35SO4 method (13.3+/-3.0 L; p = .002). Estimating ECW by NaBr dilution was comparable with other research-based ECW methods and, thus, offers a practical alternative for evaluating ECW in patients with AIDS.     

Estimating body composition in children with Duchenne muscular dystrophy: comparison of bioelectrical impedance analysis and skinfold-thickness measurement

BACKGROUND: Duchenne muscular dystrophy (DMD) is often associated with obesity, which worsens the handicap early in the course of the disease. Nutritional assessment, however, can be difficult and often misleading in DMD. OBJECTIVE: Two methods of estimating body composition in DMD, skinfold-thickness (ST) measurement and bioelectrical impedance analysis (BIA), were compared with a reference method, labeled water dilution (WD). DESIGN: Body composition was estimated by using ST measurements and BIA (50 kHz, 800 mAmp), as well as the WD method (1 mL H2(18)O/kg) in 11 DMD patients with a mean (+/-SD) age of 10.0 +/- 2.5 y. RESULTS: When compared with the WD method, ST measurement significantly (P < 0.01) overestimated fat-free mass (FFM) (mean +/- SD ST: 24.5 +/- 5.9 kg; mean +/- SD WD: 18.2 +/- 2.5 kg), which led to an underestimation of the percentage of fat mass (%FM) (ST: 23.3 +/- 10.4%; WD: 40.1 +/- 17.1%; P < 0.05). In contrast, estimates obtained with BIA (FFM: 21.5 +/- 4.5 kg; %FM: 31.3 +/- 13.9%) did not differ from those obtained with WD. The difference from the reference method was less for BIA (mean: 3.3 kg; 95% CI: 0.8, 4.9 kg) than for ST (6.3 kg; 2.2, 8.6 kg). WD and BIA defined 73% and 55%, respectively, of the children as obese (%FM associated with body mass index cutoffs for obesity), whereas ST measurements defined 9% as obese (P < 0.01). CONCLUSIONS: Body-composition estimates by BIA are closer to those by WD than are those by ST measurement. Early detection of fat accumulation and longitudinal monitoring of nutritional care are 2 relevant applications of BIA to prevent obesity and hence lessen the burden of DMD.     

Multifrequency bioelectrical impedance analysis in women with a normal and hypertensive pregnancy

BACKGROUND: An increase in total body water is common in normal pregnancy. It is thought to be an important mechanism of maternal adaptation to pregnancy. OBJECTIVE: The aim of the present study was to assess longitudinal changes in body water compartments in pregnant women and to correlate these measurements with the course of pregnancy. DESIGN: One hundred seventy-three pregnant women with apparently normal, single pregnancies participated in this longitudinal study. Anthropometric measurements and multifrequency bioelectrical impedance were performed during the first, second, and third trimesters of pregnancy. RESULTS: One hundred three of the women completed all of the measurements; 50 of the women had a normal pregnancy and 13 had gestational hypertension. Total body water, extracellular water, and intracellular water values in normal pregnancies showed a significant, progressive increase throughout pregnancy. In women with gestational hypertension, total body water, extracellular water, and intracellular water values showed an opposite trend, suggesting a lack of plasma volume expansion through fluid-retention mechanisms. CONCLUSIONS: Our results show that multifrequency bioelectrical impedance analysis can be used to monitor variations in body water compartments in normal pregnancy and detect gestational hypertension.     

Assessment of body fluid compartment volumes by multifrequency bioelectrical impedance spectroscopy in children with dengue

Dengue haemorrhagic fever (DHF), the most severe form of illness following infection with a dengue virus, is characterized by plasma leakage and a period of increased microvascular permeability. Monitoring of plasma volume and body fluid compartment shifts is an integral part of the clinical management of DHF, and is crucial to the performance of clinical research studies on DHF pathogenesis. Multifrequency bioelectrical impedance spectroscopy (BIS) was assessed as a non-invasive method to monitor body fluid compartment shifts in children participating in a prospective, hospital-based, study of dengue virus infections in Thailand. Over the 48 h surrounding defervescence, the extracellular water/intracellular water ratio (ECW/ICW) rose in children with dengue virus infections and correlated with increasing disease severity [DHF > intermediate dengue fever (DF)/DHF > DF]. Plasma leakage remained within the ECW compartment and was not directly measured by multifrequency BIS. Expansion of the ECW space in DHF appeared to be primarily due to diminished renal water clearance. During the course of dengue illness, multifrequency BIS did not improve on serial haematocrit and bodyweight determinations for monitoring plasma volume contraction and ECW expansion, respectively.     

Underweight patients with anorexia nervosa: comparison of bioelectrical impedance analysis using five equations to dual X-ray absorptiometry

Background & aims

Body weight changes do not reflect the respective changes of body compartments, namely fat-free mass (FFM) and fat mass (FM). Both bioelectrical Impedance Analysis (BIA) and the Dual X-ray absorptiometry (DXA) measure FFM and FM.This study in underweight patients with anorexia nervosa (AN) aims to compare measurements of FM and FFM done by DXA and BIA using 5 different BIA equations already validated in healthy population and to identify the most suitable BIA equation for AN patients.

Methods

Fifty female patients with AN (BMI = 14.3 ± 1.49, age = 19.98 ± 5.68 yrs) were included in the study. Body composition was measured by DXA (Delphi W, Hologic, Bedford, MA) and by 50 kHz BIA (FORANA, Helios) using 5 different BIA equations validated in healthy population (Sun, Geneva, Kushner, Deurenberg and Roubenoff equations). Comparison between the DXA and the 5 BIA equations was done using the sum of the squares of differences and Bland–Altman plots.

Results

The Deurenberg equation gave the best estimates of FFM when compared to the measurements by DXA (FFM_dxa = 35.80 kg versus FFM_deurenberg = 36.36 kg) and very close estimates of FM (FM_dxa = 9.16 kg and FM_deurenberg = 9.57 kg) The Kushner equation showed slightly better estimates for FM (FM_kushner = 9.0 kg) when compared to the DXA, but not for FFM. Sun equation gave the broadest differences for FM and FFM when compared with DXA.

Conclusion

The best available BIA equation to calculate the FFM and the FM in patients with AN is the Deurenberg equation. It takes into account the weight, height and age and is applicable in adults and adolescents AN patients with BMI of 12.8–21.0, and for ages between 13.4 and up to 36.9 years.