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Abstract: FR-PO754

Determination of Calf Normalized Resistivity at 50 kHz in the General Population

Session Information

Category: Dialysis

  • 701 Dialysis: Hemodialysis and Frequent Dialysis

Authors

  • Zhu, Fansan, Renal Research Institute, New York, New York, United States
  • Abbas, Samer R., Renal Research Institute, New York, New York, United States
  • Rosales, Laura, Renal Research Institute, New York, New York, United States
  • Levin, Nathan W., Renal Research Institute, New York, New York, United States
  • Kotanko, Peter, Renal Research Institute, New York, New York, United States
Background

We have developed 5 kHz calf normalized resistivity (CNR5) method to identify degrees of fluid status in dialysis patients. However, the 50 kHz BIA method have been used in clinical studies for many years. The aim of this study was to evaluate whether 50 kHz CNR (CNR50) could be used to determine fluid status by comparing CNR5 and CNR50 chosen randomly from a general population.

Methods

Subjects from a general population were studied once. Calf multi-frequency bioimpedance spectroscopy measurements (Hydra 4200) was performed in the supine position. Further measurements included body height, weight and calf circumference. Resistances at 5 kHz (R5) and at 50 kHz (R50) respectively were extracted from the raw data. Calf resistivities (Rho5 and Rho50) were calculated based on resistances and average cross-sectional areas over a calf length measurement of 10 cm. CNR5 and CNR50 were obtained by normalizing calf resistivities with body mass index (BMI).

Results

Ninety-one subjects (sex: 49 f, age: 57±10 year, BMI: 27.9± 4.7 kg/m2) were evaluated. Although calf R50 (R2=0.89, p<0.0001), Rho50 (R2=0.9, p<0.0001) and CNR50 (R2=0.91, p<0.0001) highly correlated with CNR5, Rho5 and CNR5 respectively, the values of R50 (36.6±6.0, Ohm), Rho50 (352.9±60.6, Ohm*cm) and CNR50 (13.0±2.5, 10-2 *Ohm*m3/kg) were significantly lower than in R5 (48.1±7.2, Ohm), Rho5 (464.9±79, Ohm*cm) and CNR5 (17.1±3, 10-2 *Ohm*m3/kg) respectively (Fig.1 and Fig.2). Bland-Altman analysis showed that the differences between CNR5 and CNR50 was 4.08±0.95 10-2 *Ohm*m3/kg (Fig.3). The difference between CNR5 and CNR50 was weakly (R2=0.13) but significantly (p<0.001) associated with subject age (Fig.4).

Conclusion

Values of 50 kHz data R50, Rho50 and CNR50 were lower than that of 5 kHz data with BIA respectively, presumably because a 50 kHz current passes into part of the intracellular space, while this does not occur measurably with 5 kHz current. This difference offers the practicability of using the CNR50 range in healthy subjects, as a criterion of normal fluid status.

Figures