Abstract

The purpose of this study was to test the validity of a multiple frequency bioimpedance spectroscopy (BIS) technique that estimates extracellular fluid volume (ECV), intracellular fluid volume (ICV), and total body water (TBW). Thirteen healthy males (mean+/-SD: age, 23+/-3 yr; body mass, 80.6+/-14.7 kg) had their TBW and ECV measured by ingesting dilution tracers (7.27 g deuterium oxide, 1.70 g sodium bromide; blood samples at 0 and 4 h). ICV was calculated as TBW minus ECV. Impedance was measured (50-500 kHz) at rest, on a nonconducting surface, with a BIS analyzer. Electrode placement, posture, exercise, food/fluid intake, and ambient temperature were controlled. Dilution measures (TBW, 51.00+/-9.30; ECV, 19.88+/-3.14; ICV, 31.12+/-6.80 L) and BIS volumes (TBW, 50.03+/-7.67; ECV, 20.95+/-3.33; ICV, 29.04+/-4.51 L) were significantly different for ECV (P<0.01) and ICV (P<0.05); some individual differences were large. The correlation coefficients of dilution versus BIS volumes (r=0.93 to 0.96) were significant at P<0.0001; SEEs were: TBW, 223 L; ECV, 1.26 L; and ICV, 1.71 L. We concluded that BIS is valid for between-subject comparisons of body fluid compartments, is appropriate in clinical settings where change in ECV/ICV ratio is important, and should be used by comparing the required level of accuracy to the inherent technique error variance. Verf.-Referat