Single-frequency Bioimpedance Research Articles

Effect of airplane travel on women treated for breast cancer.

Abstract Abstract #1119 Background: Many patient materials promulgate lifestyle adaptations purported to minimize risk of lymphedema. One factor often mentioned is development or exacerbation of lymphedema due to airplane travel. The aim of this study was to describe prospectively the effect of airplane travel on women treated for breast cancer, traveling to Caloundra, Qld., Australia to attend a dragon boat regatta.
 Methods: Pre and post data were obtained from 63 women traveling from Canada to Australia, and from 12 women traveling within Australia. 54% were treated for breast cancer on their dominant side, 63% underwent mastectomy with or without reconstruction, 77% underwent axillary node dissection, and 21% wore a compression sleeve during flight; 94% trained at a moderate to vigorous intensity for the regatta. Single frequency bioimpedance analysis (BIA; XCA; Impedimed Inc.®) was used to determine the inter-limb difference in upper limb extracellular fluid. BIA is highly reliable and has high sensitivity and specificity for increased extracellular fluid accumulation. Change in ratio >0.05 for women without lymphoedema is of clinical significance. Women were measured within 2 weeks of their flight to Caloundra, immediately on arrival in Caloundra, and for 46 women, within 6 weeks of return to Canada.
 Results: Airplane travel did not have a significant effect on the upper limb BIA ratio, either between the pre and post flight (t75= -0.355; p=0.72) or between the pre and follow-up measures (t44=.241; p=0.811).
 
 Overall, the BIA post ratio increased from the pre measure by ≤0.02 in 48 women; 0.02 to <0.05 in 12 women; 0.05 to <0.10 in 10 women; and >0.10 in 5 women (Fig 1). In Figure 1, symbols in grey-shaded area represents women who did not have lymphedema prior to flight but presented with it post flight and the dashed lines indicate previously established cut-offs for criteria for detection of lymphedema. Dotted line on each graph is the line of agreement. The 6 symbols in the grey shaded area (Fig 1) represent women from the international group; their change in BIA ranged from 0.05 to 0.28. Follow-up measures were available on 5 of these women, and indicated that 4 were below the cut-offs for lymphedema. All 6 women had undergone mastectomy and axillary clearance of their lymph nodes and for 5, surgery was on their dominant side. Only 3 of the women wore a compressive sleeve on the plane.
 Discussion: For the majority of women who undertake moderate to vigorous upper limb exercise, airplane travel did not have a significant impact on extracellular fluid ratio. Acknowledgment: Impedimed for funding and equipment. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1119.

Precision and reliability of strength (Jamar vs. Biodex handgrip) and body composition (dual-energy X-ray absorptiometry vs. bioimpedance analysis) measurements in advanced cancer patients

Important deteriorations in body composition and strength occur and need to be accurately measured in advanced cancer patients (ACPs). The aim of this study was to establish the relationship between a single-frequency bioimpedance analyzer (BIA) and the dual-energy X-ray absorptiometer (DXA), as well as the Jamar handgrip dynometer and the Biodex handgrip attachment, and to determine the precision of each of these instruments in ACPs. Eighty-one ACPs with non-small-cell lung cancer and gastrointestinal cancer were recruited from the McGill University Health Centre (Montreal, Que.). Consecutive paired measurements, with repositioning between measurements, were obtained for total-body DXA, BIA, Biodex handgrip, and BIA plus Jamar handgrip. The total-body percent coefficient of variation (%CV) for the BIA and DXA were 1.34 and 1.56 for fat mass (FM), respectively, and 0.42 and 0.72 for fat free mass (FFM), respectively. The %CV for the Jamar and Biodex handgrips were 6.3 and 16.7, respectively. Bland-Altman plots were used to characterize the limits of agreement between DXA and BIA for FM (4.60 +/- 7.80 (-3.19 to 12.39) kg) and FFM (-1.87 +/- 7.16 (-9.03 to 5.29) kg). Both DXA and BIA demonstrate good short-term precision in ACPs. However, given its poor accuracy, it remains to be determined if BIA can be used to monitor ACPs for changes in total-body tissue composition as a function of time, whether for observation or response to treatment. Furthermore, because of wide limits of agreement, the DXA and BIA cannot be used interchangeably in research or clinical settings. The Jamar handgrip dynamometer shows more consistency than the Biodex handgrip attachment in ACPs, and should therefore be the preferred measure of changes in strength over time.

Single frequency versus bioimpedance spectroscopy for the assessment of lymphedema

The aims were to determine (i) whether single frequency bioimpedance analysis (SFBIA) is as accurate as bioimpedance spectroscopy (BIS) in measurement of extracellular fluid and (ii) whether change in extracellular fluid was specific to only the limb directly affected by surgery. Arms of the control (n = 28) and arm lymphedema group (n = 28) and legs of the leg lymphedema group (n = 16) were assessed with SFBIA. All four limbs in all participants were assessed with BIS. All measurements occurred in a single session. BIS-measured ratios were highly concordant with those obtained with SFBIA (r (c) = 0.99, P < 0.001). Repeated measures ANOVA revealed that the ratio involving the lymphedema limb was different to the ratio of the non-oedematous limbs which was not significantly different to the arm or leg ratios of the control group. SFBIA is a simple accurate alternative to BIS for the clinical assessment of unilateral lymphedema. BIS discriminates those with clinical diagnosis of unilateral lymhoedema from those without the diagnosis.

Frequent Hemodialysis Network (FHN) randomized trials: Study design

Observational studies suggest improvements with frequent hemodialysis (HD), but its true efficacy and safety remain uncertain. The Frequent Hemodialysis Network Trials Group is conducting two multicenter randomized trials of 250 subjects each, comparing conventional three times weekly HD with (1) in-center daily HD and (2) home nocturnal HD. Daily HD will be delivered for 1.5-2.75 h, 6 days/week, with target eK(t)/V(n) > or = 0.9/session, whereas nocturnal HD will be delivered for > or = 6 h, 6 nights/week, with target stdK(t)/V of > or = 4.0/week. Subjects will be followed for 1 year. The composite of mortality with the 12-month change in (i) left ventricular mass index (LVMI) by magnetic resonance imaging, and (ii) SF-36 RAND Physical Health Composite (PHC) are specified as co-primary outcomes. The seven main secondary outcomes are between group comparisons of: change in LVMI, change in PHC, change in Beck Depression Inventory score, change in Trail Making Test B score, change in pre-HD serum albumin, change in pre-HD serum phosphorus, and rates of non-access hospitalization or death. Changes in blood pressure and erythropoiesis will also be assessed. Safety outcomes will focus on vascular access complications and burden of treatment. Data will be obtained on the cost of delivering frequent HD compared to conventional HD. Efforts will be made to reduce bias, including blinding assessment of subjective outcomes. Because no large-scale randomized trials of frequent HD have been previously conducted, the first year has been designated a Vanguard Phase, during which feasibility of randomization, ability to deliver the interventions, and adherence will be evaluated.

Effect of acute changes in hydration on body composition estimates from bioimpedance analysis

Bioimpedance spectroscopy (BIS) has been shown to provide accurate estimates of acute changes in hydration. This study examined the effects of acute hydration changes on estimates of fat-free mass (FFM) and fat mass (FM) measured by BIS and single frequency bioimpedance analysis (SF-BIA) as compared to dual energy x-ray absorptiometry (DXA) in 17 young adults (15 F, 2 M). A 4-day dehydration/rehydration protocol and two SF-BIA instruments were used in this study. Although all bioimpedance methods provided estimates of FFM comparable to DXA estimates at baseline and after dehydration, BIS estimates were the most highly correlated (r2 = 0.950 at both time points) and the least variable (SEE = 1.99 kg and 2.03 kg, respectively). After rehydration, greater variability and lower correlations with DXA were observed for all three bioimpedance estimates with SEE ranging from 3.18 kg to 9.71 kg. Correlations ranged from 0.800 to 0.850 for the SF-BIA instruments; however, the correlation between BIS-FFM and DXA-FFM estimates declined sharply (r2 = 0.472). Estimates of FM were comparable among methods at all time points, and all estimates were highly correlated (r2 = 0.94–0.99) with DXA-FM. BIS appears to perform better than SF-BIA for measuring FFM at baseline and in a dehydrated state in healthy, young, non-obese subjects. Rehydration appears to affect the accuracy of BIS and SF-BIA FFM estimates. In contrast, all methods provided comparable estimates of FM regardless of hydration status. Support: USDA Hatch ARZT-136529-H-23-128.

Bioimpedance, dry weight and blood pressure control: new methods and consequences

Chronic overhydration contributes to the development of left ventricular hypertrophy and a high cardiovascular mortality in end-stage renal disease. Assessment of dry weight is highly dependent on clinical assessment. Bioimpedance technology offers the potential to quantify body fluid compartments and to facilitate dry weight prescription. This review covers recent innovative approaches to dry weight assessment using bioimpedance technology. Three different bioimpedance approaches to determine dry weight have been published. The normovolemic/hypervolemic slope method applies whole body multifrequency bioimpedance to assess predialysis total body extracellular fluid volume and compares the extracellular fluid volume/body weight relation at hypervolemia with the standard value in normovolemic individuals. The resistance-reactance graph method uses whole body single frequency bioimpedance for assessment of hydration state and nutritional status from height-adjusted resistance and reactance. The resulting resistance-reactance vector is set in relation to a distribution range in a normovolemic population. An alternative method uses segmental bioimpedance in the form of continuous intradialytic calf bioimpedance to record changes in calf extracellular volume during dialysis. Dry weight by this method is defined as the weight at which calf extracellular volume is not further reduced despite ongoing ultrafiltration. Although promising, none of these methods has gained much popularity, probably due to the difficulties in understanding bioimpedance and the lack of gold standard methods for dry weight determination. Bioimpedance will improve dry weight assessment, but further refinement of the methods as well as large-scale clinical studies to demonstrate the accuracy and the clinical value of objective dry weight determination are needed.

Equivalence of information from single versus multiple frequency bioimpedance vector analysis in hemodialysis

In suspended cells, low-frequency current only passes through extracellular fluids, while current at higher frequencies passes through extra- and intracellular fluids. Cells in soft tissues are in contact with each other, which causes tissue anisotropy, meaning that impedance changes along different cell directions, with part of low-frequency current also passing through cells. Hence, equivalent information on body impedance change is expected at all frequencies, which we proved in a dynamic condition of fluid removal with hemodialysis. We performed whole-body impedance spectroscopy (496 frequencies from 4 to 1024 kHz, SEAC SFB3 analyzer; Brisbane, Australia) before and during fluid removal (0, 60, 120, 180 min, 2.5 kg) in 67 hemodialysis patients. With increasing current frequency, resistance (R) decreases and reactance (Xc) moves along the Cole's semicircle on the R-Xc plane. The Cole's semicircles progressively enlarged and moved to the right on the R-Xc plane following fluid removal (increase in both R and Xc values at any given frequency). Xc values at 5 kHz (expected values close to 0 Ohm) were 70% of the maximun Xc, indicating an intracellular current flows at low frequencies. The correlation coefficient between R at 50 kHz (standard frequency) and R at other frequencies ranged from 0.96 to 0.99, and the correlation coefficient between Xc at 50 kHz and Xc at other frequencies at any time point ranged from 0.65 to 0.99. From high Xc values at low frequency, tissue anisotropy is inferred. Intra- and extracellular current flow causes equivalence of information based on functions of R and Xc measurements made at 50 kHz versus other frequencies.

The prediction of basal metabolic rate in young adult, severely obese patients using single-frequency bioimpedance analysis.

To evaluate whether bioimpedance analysis (BIA) is a useful tool for predicting basal metabolic rate (BMR), sex, age, height, weight, BMI, and single-frequency BIA variables (resistance index and phase angle) were assessed in 61 young adult non-diabetic obese patients (BMI >35 kg/m(2)). BMR was measured by indirect calorimetry. In both sexes BMR significantly correlated with weight, BMI, and resistance index. Using multiple regression analysis, the following prediction equations were derived: (1). considering individual characteristics: BMR (kcal/day)=780+11.4xweight (+221 for men); (2). including also BIA variables: BMR=- 96+8.4xresistance index+8.3xweight+82.5xphase angle. Thus, in young adult, severely obese individuals, BIA variables are significant predictors of BMR.

Body composition analysis in chronic dialysis patients: a longitudinal study

Objective Nutritional status is an important determinant of morbidity and mortality in dialysis patients. Body composition analysis bioelectrical impedance techniques are becoming commonplace in the clinical setting. Our objective is to report our clinical experience using bioelectrical impedance analysis for the prospective nutritional surveillance of dialysis patients. Methods A total of 204 patients, 157 on hemodialysis and 47 on peritoneal dialysis were followed for a median of 21 months. Values from the first trimester were averaged and compared to those obtained in the last trimester. Bioelectrical impedance values were obtained using a single frequency (50 kHz) bioimpedance analyzer. Results Baseline values for body weight, height, body mass index and body surface area were similar in both treatment modalities. Hemodialysis patients lost a discreet amount of body weight (1.5%, p=0.0334). Body weight did not change in peritoneal dialysis patients. Significant decreases in resistance (p=0.l0023) and phase angle (p=0.0481) were noted in hemodialysis but not peritoneal dialysis patients. A small but significant decrease in fat free (1.8%; p=0.0028) and body cell free (3.3%; p=0.0036) mass was noted in hemodialysis but not peritoneal dialysis patients. Conclusions 1. Bioelectrical impedance analysis may detect losses in fat free mass and body cell mass that are not apparent by body weight monitoring. 2. Bioelectrical impedance analysis is a practical clinical tool for evaluating body composition in dialysis patients.

Use of single-frequency bioimpedance at 50 kHz to estimate total body water in patients with multiple organ failure and fluid overload.

To investigate the relationship between single-frequency bioimpedance at 50 kHz (both total body impedance and segmental impedance) and total body water, measured using tritiated water in the presence of the severe fluid retention seen in multiple organ failure. Prospective, controlled study. General intensive care unit. Twenty patients with multiple organ failure and 30 normal volunteers, of whom a subgroup of ten had total body water measured. None. Total body water and total and segmental bioimpedance values at 50 kHz were measured using tritiated water and a Holtain body composition analyzer in 20 patients with multiple organ failure and in ten normal volunteers. An additional 20 normal volunteers also had segmental and total body impedance measured. There was no difference in the linear regression lines constructed for the patients and the volunteers, but the SEM in the patients (7.6 L) was four times that seen in the normal subjects (1.9 L). In a further seven patients, the impedance technique overestimated the change in total body water, deduced from acute changes in weight, by between 0% and 46% (median, 12%). In the patients, who were supine, the knee-ankle segment contributed significantly more to total body impedance than it did in the normal volunteers (42.5% vs. 34.4%; p < .001), who were upright and mobile immediately before the measurement. Although single-frequency bioimpedance does give an indication of total body water and change in total body water, it is neither precise nor accurate enough to be the sole guide to fluid therapy. The proportion of total impedance contributed by the knee-ankle segment, which contains relatively little water, was significantly greater in the patients than in the controls, probably reflecting better drainage of fluid from the lower limb in the supine position.

Upper extremity skeletal muscle mass: Potential of measurement with single frequency bioimpedance analysis

This study examined the potential of single frequency (50 kHz) BIA for estimation of upper extremity skeletal muscle (SM) mass. Subjects ( n = 50) were weight stable adults varying in age ( X ± SD, 51.6 ± 17 yr) and body mass index (27.2 ± 5.9 kg/m 2). Determinants of arm to arm impedance index (length L; L 2/ Z) were examined using multiple regression analysis. A good correlation was observed between L 2/ Z and arm SM estimated by dual-energy X-ray absorptiometry ( r = 0.88, p < 0.001). Additional significant model covariates were arm fat mass ( p < 0.05), bone mass ( p < 0.01), and age ( p < 0.001). These findings suggest that upper extremity SM may be rapidly and easily quantified using a simple and inexpensive BIA system combined with appropriate age-adjusted impedance prediction equations.

Bioimpedance analysis: evaluation of leg-to-leg system based on pressure contact foot-pad electrodes

Conventional single frequency bioimpedance analysis (BIA) systems require technician placement of arm and leg gel electrodes, a suitable location for recumbent measurements, and a separate measurement of body weight. The aim of this study was to evaluate a new single frequency 50 KHz leg-to-leg bioimpedance analysis (BIA) system combined with a digital scale that employs stainless steel pressure-contact foot pad electrodes for standing impedance and body weight measurements. Healthy adults were evaluated for 1) electrode validity and 2) potential for body component estimation. Pressure-contact foot-pad electrode measured impedance was highly correlated with (N = 9, r = 0.99, P < 0.001) impedance measured using conventional gel electrodes applied to the plantar surface of both lower extremities; mean (+/-SD) impedance was systematically higher by about 15 ohms for pressure contact electrodes (526 +/- 56 ohms vs 511 +/- 59 ohms; P < 0.001). Second, the relationship between stature-adjusted leg-to-leg impedance (H2/Z) measured by the new system and two body composition components (total body water by 3H2O dilution (N = 144); and fat-free body mass, by underwater weighing and dual x-ray absorptiometry (N = 231)) was modeled using multiple regression analysis. Correlation coefficients for H2/Z alone versus body composition components were lower for leg-to-leg BIA than for arm-to-leg BIA; correlation coefficients and SEEs became similar for the leg-to-leg and arm-to-leg BIA systems with addition of three covariates (age, gender, and waist/hip circumference ratio) to regression models. The leg-to-leg pressure contact electrode BIA system has overall performance characteristics for impedance measurement and body composition analysis similar to conventional arm-to-leg gel electrode BIA and offers the advantage of increased speed and ease of measurement.

Monitoring hemodialysis changes with bioimpedance. What do we really measure?

Changes in electrical resistance (delta R), water (delta H2O), and blood variables (Na+, K+, Cl-, protein [Pr], osmolality [Osmo], hemoglobin [Hb], and hematocrit [Hct]) were monitored during hemodialysis in 20 subjects. Average delta H2O was 1.69 +/- 0.91 liters. Blood, R, and circumferences (C) were measured for the upper limb (UL), lower limb (LL), and total body (TB) before, midway, and at the end of dialysis. Segmental volumes (V) and specific resistivity (rho) were computed. delta Hct and delta Pr were stronger predictors of delta H2O than delta R. Forward stepwise regression analysis using delta R at 5, 50, and 548 kHz, delta Pr, and delta Hct showed that delta Hct and delta Pr alone accounted for 77% of the variance in delta TBW. Adding delta R increased this at most to 81%. Both the UL and LL had significant increases in rho. The volumetric change of the UL was nonsignificant, whereas that of the LL accounted for over one half of the delta H2O. Single frequency bioimpedance cannot be used to monitor dialytic delta H2O unless one accounts for fluid composition changes. Monitoring bioimpedance changes over only a single body segment is also questioned.