RELIABILITY OF MULTIPLE FREQUENCY BIOELECTRICAL-IMPEDANCE ANALYSIS - AN INTERMACHINE COMPARISON

The technical reliability (i.e., interinstrument and interoperator rel iability) of three SEAC-swept frequency bioimpedance monitors was asse ssed for both errors of measurement and associated analyses. In additi on, intraoperator and intrainstrument variability was evaluated for re peat measures over a 4-hour period. The measured impedance values from a range of resistance-capacitance circuits were accurate to within 3% of theoretical values over a range of 50-800 ohms. Similarly, phase w as measured over the range 1 degrees-19 degrees with a maximum deviati on of 1.3 degrees from the theoretical value. The extrapolated impedan ce at zero frequency was equally well determined (+/-3%). However, the accuracy of the extrapolated value at infinite frequency was decrease d, particularly at impedances below 50 ohms (approaching the lower lim it of the measurement range of the instrument). The interinstrument/op erator variation for whole body measurements were recorded on human vo lunteers with biases of less than +/-1% for measured impedance values and less than 3% for phase. The variation in the extrapolated values o f impedance at zero and infinite frequencies included variations due t o operator choice of the analysis parameters but was still less than /-0.5%. (C) 1997 Wiley-Liss, Inc.