Different impedance indexes in segmental and whole-body measurements in peritoneal dialysis patients

Abstract

Hyper-hydration, malnutrition, and arterial hypertension are the most common risk factors associated with mortality in peritoneal dialysis PD patients. Segmental bioimpedance measured placing electrodes at the ends of the superior and inferior limbs, and in the trunk can be used to monitor changes in regional fluid status. In this work three impedance based estimators were analyzed: impedance Z, impedance divided by the height of the patient Z/H, and impedance multiplied by the body mass index ZBMI. We measured 6 configurations of segmental impedance measurements, at 50 kHz, in 23 male patients undergoing PD, classified as normo-hydrated or hyper-hydrated. Wilcoxon test was used to analyze the bioimpedance change produced by a PD session. Mann-Whitney U test was used to analyze the separation between groups obtained by means of clinical parameters. Spearman correlation was used to study the correlation between segmental impedance and clinical assessment. Statistical significance was set at P < 0.05. The ZBMI index gives information about the specific resistivity of tissues and not to fluid and fat mass changes.