title: Bioimpedance analysis: evaluation of leg-to-leg system based on pressure contact footpad 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.
authors.affiliation: Department of Medicine, St. Luke's-Roosevelt Hospital, Columbia University, College of Physicians and Surgeons, New York, NY 10025, USA.
authors.forename: C
authors.initials: C
authors.lastname: Nuñez
authors.forename: D
authors.initials: D
authors.lastname: Gallagher
authors.forename: M
authors.initials: M
authors.lastname: Visser
authors.forename: F X
authors.initials: FX
authors.lastname: Pi-Sunyer
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: S B
authors.initials: SB
authors.lastname: Heymsfield
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D000368:Aged; D001823:Body Composition; D015992:Body Mass Index; D001834:Body Water; D017097:Electric Impedance; D004566:Electrodes; D005260:Female; D006801:Humans; D007866:Leg; D008297:Male; D008875:Middle Aged