Multifrequency Bioelectrical Impedance as a Measure of Differences in Body Water Distribution

Abstract

In 38 females, aged 21.3 ± 1.8 years (mean ± SD) and 22 males, aged 21.6 ± 2.0 years, total body water (TBW) was assessed by bioelectrical impedance at a frequency of 100 kHz (Z₁₀₀), and extracellular water (ECW) was assessed at a frequency of 1 (Z₁) or 5 kHz (Z₅). Impedance ratios of low frequencies (Z₁ or Z₅) to high frequency (Z₁₀₀) were calculated as indicators of body water distribution. Furthermore, changes in body water distribution during the menstrual cycle were assessed in 16 females, aged 22.1 ± 1.7 years, divided into subjects using or not using oral contraceptives. In general, the ratio ECW to TBW was lower in males compared to females, which was reflected in the ratios Z₁/Z₁₀₀ and Z₅/Z₁₀₀·However, the ratio Z₅/Z₁₀₀ reflected this difference less clear, probably because at 5 kHz the current partly passes the cell membranes. Weight changes during the menstrual cycle are generally accepted to be due to a retention of ECW. The ratio Z₅/Z₁₀₀ and the ratios Z₁/Z₁₀₀and Z₅/Z₁₀₀ for those subjects not using oral contraceptives differed significantly between day with minimal and day with maximal weight. A negative correlation was found between weight change, still considering day with minimal and day with maximal weight, and change in impedance at 5 and 50 kHz for subjects not using oral contraceptives. It is concluded that differences in body water distribution are reflected by low-to-high impedance ratios.

Proton and sodium MRI assessment of fluid level in calf tissue

“…As one changes from standing to the supine position, part of the 700-mL venous blood is expected to redistribute back to the upper body. A postural change from upright to supine is expected to induce less fluid shift than the head-down tilt position used in simulation of microgravity environments (11,12,16). Assuming that half of the 700-mL body fluid was involved in the response to the postural change employed in this study, the present results appear to be consistent with the changes of fluid levels corresponding to the postural fluid shift and the saline infusion involved in this study.…”

“…Isotope dilution methods have been established to measure whole-body extra-(ECW) and intracellular (ICW) water levels (9,10). Bioelectric impedance analysis (BIA) is a technique under development that is sensitive to muscle mass change and, when used in multifrequency mode, changes in ECW:ICW distribution (11,12). However, it has limited anatomical resolution and accuracy, and relies heavily on the validity of the available equivalent circuit models (13).…”

Change in body water distribution index in infants who become stunted between 4 and 18 months of age

“…ECW and TBW could be predicted independently at 5 and 100 kHz, respectively (Deurenberg et al, 1995). Differences in body water distribution over the intra-and extracellular spaces are reflected by impedance ratios of 5-100 kHz frequencies (Lusseveld et al, 1993). In our subjects, the length 2 /R 5 is assumed to reflect the ECW volume, and length 2 /R 100 the TBW volume.…”

Comparing the Whole Body Impedance of the Young and the Elderly using BIMS

“…On the other hand, multifrequency analysis is used to measure BI at each frequency by applying a chirp waveform in combination with multiple frequencies ranging from low-frequency (LF) to high-frequency (HF). The advantage of single-frequency analysis is that BI can be measured in over a short period of time, but the disadvantage is that BI cannot be analyzed in different frequency bandwidths [7].…”