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Body impedance measurements during dialysis
A de Lorenzo1, P F Barra, G F Sasso
1Department of Human Physiology, University Tor Vergata, Rome, Italy.
European Journal of Clinical Nutrition
|June 1, 1991
Summary
Dialysis patients show significant changes in body impedance correlating with weight loss. Standard bio-electrical impedance formulas may overestimate body composition in edematous individuals due to excess extracellular water.
Area of Science:
- Nephrology
- Physiology
- Biomedical Engineering
Background:
- Body impedance analysis is used to estimate body composition.
- Patients undergoing dialysis often experience fluid shifts and edema.
- Accurate body composition assessment is crucial for managing fluid balance in dialysis patients.
Purpose of the Study:
- To investigate the relationship between body weight changes and body impedance in dialysis patients.
- To evaluate the accuracy of standard bio-electrical impedance analysis (BIA) prediction formulas in edematous individuals.
Main Methods:
- Studied 10 patients (6 male, 4 female) before and during dialysis.
- Measured body weight and total body impedance.
- Calculated fat-free mass (FFM) using skinfolds and total body water (TBW) using BIA.
Main Results:
- A strong negative correlation (r = -0.91) was found between weight loss (primarily water) and increase in body impedance.
- Observed impedance changes were significantly larger than predicted by standard BIA formulas.
- Pre-dialysis impedance values were lower than expected, attributed to excess extracellular water.
Conclusions:
- Standard BIA prediction formulas overestimate body composition (TBW, FFM) in edematous dialysis patients.
- Excess extracellular water in pre-dialysis patients lowers specific resistivity, affecting impedance measurements.
- Body impedance changes during dialysis are significant but require adjusted interpretation in edematous states.