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

Abstract

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.

Evaluation of foot-to-foot bioelectrical impedance analysis for the prediction of total body water in oncology outpatients receiving radiotherapy

“…The regression coefficient of 0.56 is close to 0.6 and compares to other studies which found the value to be 0.66 (Nunez et al, 1997;Bell et al, 1998). The intercept of 5.9 is larger than anticipated.…”

“…The intercept of 5.9 is larger than anticipated. The intercepts in other studies have been 0.65 (Bell et al, 1998) and 1.93 (Nunez et al, 1997). Another study in children with Prader Willi syndrome did find a similar regression coefficient (Davies, 1992).…”

“…As can be seen from Figure 2 there is a lot of scatter around the line of best fit contributing to a high standard error of estimate Statement, 1994;Houtkooper et al, 1996) than have been observed in foot-to-foot BIA studies which may be of concern. A reason suggested by Nunez (1997) for the large SEE associated with body composition regression models in their studies was because of the diverse nature of the subject pool. This was also the case in the present study, with patients ranging from severely malnourished to obese and some receiving chemotherapy and on a variety of medications.…”

“…There are no published studies investigating this technique in patients with cancer or in chronic diseases other than obesity. Studies in other populations showed that foot-to-foot BIA was acceptable (Nunez et al, 1997;Jebb et al, 2000), but others found significant error in TBW estimation, particularly as the volume of TBW increased (Bell et al, 1998;Abbott & Davies, 2001;Tyrrell et al, 2001). The aim of this study was to investigate the validity of foot-to-foot BIA by comparing the TBW predicted by foot-to-foot BIA with that measured using a deuterium oxide dilution technique in oncology outpatients receiving radiotherapy to the head and neck area.…”

“…Population-relevant equations are recommended to minimise the possible sources of error such as extracellular water volume, hydration status, geometric body shape and adipose volume (Baumgartner et al, 1989;NIH Technology Assessment Conference Statement, 1994). Foot-to-foot BIA has been investigated in several studies, principally in children, healthy adults or in overweight or obese subjects (Hainer et al, 1995;Nunez et al, 1997;Bell et al, 1998;Xie et al, 1999;Jartti et al, 2000;Jebb et al, 2000;Abbott & Davies, 2001;Cable et al, 2001;Powell et al, 2001;Tyrrell et al, 2001;Utter et al, 2001;Batterham et al, 2002). There are no published studies investigating this technique in patients with cancer or in chronic diseases other than obesity.…”