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Bioelectrical Impedance Analysis Estimation of Water Compartments in Elderly Diseased Patients

The Source Study

^a Centre Hospitalier Universitaire, Angers, France

Patrick Ritz, for the Source Study, Service de Médecine B, Centre Hospitalier Universitaire, F-49033 ANGERS CEDEX 01, France E-mail: patrick.ritz{at}wanadoo.fr.

Decision Editor: John E. Morley, MB, BCh

Background. 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.

Methods. 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 ¹⁸O dilution and of ECW with bromide (Br) dilution.

Results. 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 ¹⁸O 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.