Evolution of bioimpedance: a circuitous journey from estimation of physiological function to assessment of body composition and a return to clinical research

Abstract

BACKGROUND/OBJECTIVES:Bioimpedance is the collective term that describes safe, non-invasive methods to measure the electrical responses to the introduction of a low-level, alternating current into a living organism, and the biophysical models to estimate body composition from bioelectrical measurements. Although bioimpedance techniques have been used for more than 100 years to monitor assorted biological components, the desire to translate bioelectrical measurements into physiological variables advanced the creation of empirical prediction models that produced inconsistent results. SUBJECTS/METHODS: This paper succinctly reviews the origin, and critically evaluates the conceptual models and the implementation of bioimpedance in clinical research, including indirect assessment of assorted physiological functions and body composition (fluid volumes and fat-free mass), classification of hydration, regional fluid accumulation, prognosis in disease and wound healing. RESULTS: Despite widespread and mounting interest in the use of bioimpedance to characterise body structure and function, most experimental findings reveal the limitations of existing physical models and reliance on multiple regression models for use in assessments of an individual. CONCLUSIONS: Contemporary applications of bioimpedance emphasise the value of bioimpedance variables per se in some novel biomedical applications with the objective of identifying opportunities for future outcome-based research.European Journal of Clinical Nutrition (2013) 67, S2-S9; doi:10.1038/ejcn.2012.149Keywords: resistance; reactance; impedance; phase angle; hydration; prognosis INTRODUCTIONThe history of the use of electrical current to explore tissues and reveal information about its composition and function recognises various contributions that are the basis for contemporary bioimpedance analysis.1 The chronology of bioimpedance research highlights an interesting sequence of events that range from the development of biophysical models to address applications in the estimation of pulsatile blood flow 2-4 to assessment of body composition.

Bioimpedance as a Non-Invasive Method to Evaluate Eggs and Poultry

“…Body bioimpedance is a non-invasive, safe, easy-touse, portable, and low-cost technique to estimate body composition (Lukaski 2013;Collins et al, 2013;Dittmar et al, 2015;Harrison et al, 2015), and seems to be a promising method in poultry production for the evaluation of egg and body composition.…”

Impedance sensing device enables early detection of pressure ulcers in vivo

“…A body of literature exists that has both measured and modelled the electrical changes in cells and tissue both in vivo and in vitro, as well as provided correlations between electrical properties and cell types; this work has been summarized previously [6][7][8][9][10][11] . From an electrical perspective, a cell can be represented as an ion-rich conductive centre (cytoplasm) embedded in an ion-rich conductive medium (extracellular fluid), separated by a relatively non-conductive barrier (cell membrane).…”

Different displacement of bioimpedance vector due to Ag/AgCl electrode effect

“…4 These approaches, however, have several limitations due to the technical and biological errors related to the assumptions of the constancy of the chemical composition of the fat-free body, as well as to the need to use appropriated crossvalidated predictive equations developed in populations with similar biological and clinical characteristics to guarantee both the accuracy and the precision of the estimates when applying these equations in other populations (that is, their external validity). 1,40 Current approaches emphasize the use of raw whole-body bioimpedance measurements such as the BIVA method, 15 rather than derived variables to assess physiological, functional and nutritional status of individuals. 33,36,41 The main advantage of this method is the avoidance of any assumption about constant soft tissue hydration and its independence from reliance on body weight as a predictor in regression prediction equations.…”

“…1 These noninvasive methods use modern electronic devices to introduce a safe alternating current into the body at single or multiple frequencies and to measure passive bioelectrical properties that are related to physiological parameters or body composition. A key component of bioimpedance methods is the use of contact surface electrodes, although its use is not universal.…”