Influence of ionic shifts during dialysis on volume estimations with multifrequency impedance analysis

During dialysis the ion concentrations in many body fluids change significantly. The influence of these changes on the accuracy of volume measurements with bioimpedance spectroscopy is investigated by the following procedure: Plasma ion concentrations and impedance spectra (5-500 kHz) are measured d...

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Bibliographic Details
Published in:	Medical & biological engineering & computing Vol. 35; no. 2; pp. 96 - 102
Main Authors:	SCHARFETTER, H, WIMSBERGER, G. H, HOLZER, H, HUTTEN, H
Format:	Journal Article
Language:	English
Published:	Heidelberg Springer 01-03-1997 Springer Nature B.V
Subjects:	Biological and medical sciences Biothermics. Biomagnetism. Bioelectricity Body Fluids Electric Impedance Female Fundamental and applied biological sciences. Psychology Hemodialysis Humans Male Models, Biological Osmolar Concentration Renal Dialysis Spectrum Analysis Tissues, organs and organisms biophysics Plasma Body fluid Fluid dynamics Electrical properties Hemodialysis Ion composition Concentration measurement Compartmental model Accuracy Spectrometry Volume measurement Equivalent circuit Electric resistivity Multifrequency observation Error correction
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Summary:	During dialysis the ion concentrations in many body fluids change significantly. The influence of these changes on the accuracy of volume measurements with bioimpedance spectroscopy is investigated by the following procedure: Plasma ion concentrations and impedance spectra (5-500 kHz) are measured during six standard haemodialyses. Intracellular ion concentrations are estimated using a multi-compartment model. Intra- (ICV) and extracellular (ECV) volumes are calculated using a fluid distribution model (FDM) based on Hanai's mixture theory. The input variables of the FDM are intra- and extracellular resistance data that have been fitted from impedance spectra with a Cole-Cole model. Resistivity changes (RCs) due to concentration changes of Na+, K+, Cl-, HCO3- and unspecified intracellular ions are estimated. The FDM is corrected for the RCs. Corrected ICVs and ECVs are calculated and compared with uncorrected values. The range of relative RCs between the start and end of the dialyses is -3.2% to 1.4% in the ECV and -3.7% to 1.7% in the ICV. From the RCs, volume estimation errors of -1.0% to 1.9% (ECV) and -1.2% to 2.1% (ICV) relative to the initial values have been calculated. At the end of dialysis, the percentage of the error with respect to the volume change is < 15% for the ECV but > 20% for the ICV. Consequently, a correction of the FDM for RCs is necessary to obtain more reliable ICV data.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0140-0118 1741-0444
DOI:	10.1007/BF02534137