Measurement of body fluid volume change using multisite impedance measurements

Previous electrical impedance studies that predict body fluid volume and body fat used a single measurement site between the wrist and ankle. Calculations based on an electrical model of the thorax suggest that with a single wrist-to-ankle measurement only the electrical characteristics of the legs and arms will contribute significantly to a prediction of the total body fluid volume. In this study, the impedance of the arms, legs and trunk were measured separately at 100 kHz and the values were correlated with weight change that occurred on 11 patients undergoing haemodialysis. Using multiple linear regression analysis combining data from the arms, legs and trunk gave a correlation coefficient of 0. 87, whereas the correlation coefficient for measurements between the wrist and the ankle was 0. 64. These results suggest that multisite impedance measurements will allow more reliable body fluid and body fat determinations to be made.