Bioelectrical impedance analysis estimation of water compartments in elderly diseased patients: the source study

This study validates, in geriatric patients, bioelectrical impedance analysis (BIA) equations that had been derived to estimate total body water (TBW) and extracellular water (ECW) in healthy elderly subjects.

We performed a multicentric trial in six geriatric wards. We studied 169 patients with varying degrees of hydration: dehydrated, euvolemic, and overhydrated. BIA estimates of TBW and of ECW were compared with the measurement of TBW with (18)O dilution and of ECW with bromide (Br) dilution.

BIA estimated TBW with a difference of 0.48 +/- 2.3 l (mean +/- SD) (50 kHz; p = .01) and 0.69 +/- 2.2 l (100 kHz; p < 0.001) compared with (18)O dilution. The difference was not affected by the hydration status. Estimates of ECW with BIA were systematically biased compared with Br dilution: 4.6 +/- 3.1 l (equation from Segal and colleagues; p < .001) and 3.4 +/- 2.9 l (equation from Visser and colleagues; p < .001). We propose a new, cross-validated equation. Conclusions. Body water spaces can be estimated accurately in geriatric patients with BIA.