Comparison of Body Hydration State in Hemodialysis Patients With the Hydra 4200 and ZOE (100 and 5 kHZ) Bioimpedance Devices

Estimation of hydration state in dialysis patients is a major challenge in clinical practice. Although many methods have been studied, none have been established yet for clinical routine practice. The investigators have developed a method, using segmental and calf bioimpedance spectroscopy (cBIS) techniques to measure body hydration. The device we used based on the FDA-approved Hydra 4200 (Xitron Technologies, San Diego, CA). The Hydra 4200 was initially developed to measure whole body and segmental body fluid volumes but Hydra is approved only for measuring healthy subjects. The cBIS monitors hydration state by continuously measuring change in resistance and resistivity in the calf during hemodialysis (HD) or it can be used for simple measurement before, during and after dialysis. Preliminary results in clinical studies have shown that optimal hydration state of HD patients may be determined by the calf method. This study aims to compare the Hydra 4200 to two other devices: the FDA approved ZOE (100 kHz) Fluid Status Monitor (Noninvasive Medical Technologies, Inc, Las Vegas) and a modified version ZOE 5 kHz. The modified ZOE monitor (ZOE (5 kHz)) delivers frequency of 5 kHz and 0.8 mA current instead of 100 kHz and 2 mA. The subjects of this study include a group of hemodialysis patients and a group of healthy controls. The healthy controls are used to identify a normal range within the healthy population for each method. Each hemodialysis patient will be studied twice in different hydration state. The study will not change the procedure of the patient's dialysis treatment. Since all devices are based on noninvasive bioimpedance technique, this study has minimal risk.