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P L Cox-Reijven

Publications and source records attributed to P L Cox-Reijven.

4 recordsLinked to original sources
PubMed2001

Role of bioimpedance spectroscopy in assessment of body water compartments in hemodialysis patients.

Bioimpedance spectroscopy (BIS) has been advocated as a tool to assess fluid status in hemodialysis (HD) patients. However, uncertainty remains about the reliability of BIS in patients with abnormalities in fluid status. Aims of the study are to assess the agreement between total-body water (TBW) and extracellular volume (ECW) measured by BIS and tracer dilution (deuterium oxide [D(2)O] and sodium bromide [NaBr]), the influence of the relative magnitude of water compartments (expressed as TBW(D(2)O) and ECW(NaBr):body weight) on the agreement between BIS and tracer dilution, and the ability of BIS to predict acute changes in fluid status. BIS and tracer dilution techniques were performed in 17 HD patients before a dialysis session. Moreover, the relation between BIS and gravimetric weight changes was assessed during both isolated ultrafiltration and HD. Correlation coefficients between TBW and ECW measured by BIS and tracer dilution were r = 0.71 and r = 0.71, respectively. Mean differences (tracer-BIS) were 6.9 L (limits of agreement, -1.5 to 21.6 L) for TBW and 2.3 L (limits of agreement, -1.7 to 9.7 L) for ECW. There was a significant relationship between the relative magnitude of TBW and ECW compartments and disagreement between BIS and tracer dilution (r = 0.65 and r = 0.77; P < 0.05). During both isolated ultrafiltration and HD, there was a significant relation between gravimetric changes and change in ECW(BIS) (r = 0.83 and r = 0.76; P < 0.05), but not with change in TBW(BIS). In conclusion, agreement between BIS and tracer dilution techniques in the assessment of TBW and ECW in HD patients is unsatisfactory. The discrepancy between BIS and dilution techniques is related to the relative magnitude of body water compartments. Nevertheless, BIS adequately predicted acute changes in ECW during isolated ultrafiltration and HD, in contrast to changes in TBW.

Adult↗
PubMed2000

Validation of bio-impedance spectroscopy: effects of degree of obesity and ways of calculating volumes from measured resistance values.

BACKGROUND: Bioelectrical-impedance spectroscopy (BIS) is a very attractive method for body composition measurements in a clinical setting. However, validation studies often yield different results. This can partly be explained by the different approaches used to transform measured resistance values into body compartments. OBJECTIVE: The aim of this study was to compare the linear regression (LR) method with the Hanai Mixture theory (HM). Secondly, the effect of degree of overweight on the accuracy of BIS was analysed. DESIGN: In 90 people (10 M, 80 F; body mass index (BMI) 23-62 kg/m2) total body water (TBW) and extracellular water (ECW) were measured by deuterium and NaBr dilution methods, respectively, and by BIS. Resistance values of ECW (R(ECW)) and TBW (R(TBW)) were used for volume calculations. Data of half the group were used for LR based on L2/R (L = length, R = resistance) to predict TBW and ECW and to calculate the constants used in the HM (kECW), k(p)). Prediction equations and constants were cross-validated in Group 2. RESULTS: Bland and Altman analysis showed that the LR method underestimated TBW by 1.1 l (P < 0.005) and ECW by 1.1 l (P < 0.005). The HM approach underestimated ECW by 0.8 l (P < 0.005). The correlations with the dilution methods and the SEEs for TBW and ECW were comparable for the two approaches. The prediction error of BIS for TBW and ECW correlated with BMI. The constant kECW, and the specific resistivities of the ECW and intracellular water (ICW) pECW and pICW were also correlated with BMI. CONCLUSIONS: The mixture approach is slightly more accurate than linear regression, but not sensitive enough for clinical use. The constants used in the HM model are not constants in a population with a wide variation in degree of overweight. The physical causes of the correlation between BMI and constants used in the model should be studied further in order to optimize the mixture model.

Adult↗