The study has two objectives based on the intended-use measurements and populations described above. The first objective is to show that relative changes in impedance as measured by the test device (ΔSFI) are strongly correlated with the amount of fluid removed during dialysis (ΔF) for subjects with ESRD and possibly Heart Failure.

The second objective is to demonstrate correlation between ΔSFI and relative changes in impedance (ΔZ) as measured by the reference device.

The investigators propose a study for validating the test device's measurement of a parameter called 'sternal fluid index' (SFI) in patients with diagnosed medical conditions related to fluid management, e.g. end-stage renal disease (ESRD), that are undergoing dialysis. The reference device for the study measures the averaged amplitude of a thoracic bio-impedance signal (Z) and a parameter called 'thoracic fluid content' (TFC), which is equal to 1000/Z. The test device measures SFI from a localized region near the sternum, whereas the reference device measures Z and TFC from the entire thoracic cavity. This means Z (or TFC) and SFI, if measured at approximately the same time, will likely correlate but have different absolute values. Thus, the statistical analysis will investigate the ability of SFI to track fluids, as well as the agreement between fluid-dependent trends displayed by SFI and Z (or TFC), as described below.

During the study the investigators will collect multiple samples, each containing a value of SFI from the test device, and values of TFC and Z from the reference device. The investigators will enroll approximately 20-50 subjects, with the goal of at least 20 subjects completing the study. The statistical analysis will include data from all subjects that complete the study. All subjects will undergo dialysis in a clinic. Approximately half to a third will have both ESRD and Heart Failure (HF). The investigators will measure a sample from each subject every 15 minutes during a standard dialysis session, which typically lasts about 3 to 4 hours. Levels of extracted fluids, determined by the dialysis machine, will be recorded at the time each sample is measured.

The statistical model compares time-dependent changes in SFI and Z values collected during dialysis. It is designed is to demonstrate: 1) that the test device is effective in characterizing fluid levels when used as intended; and 2) that the test and reference devices' measurements of trends in fluids are substantially equivalent, since they sense different physiological regions which are expected to yield different values of impedance.

Inclusion Criteria:

• Subject is between 21 (twenty-one) and 90 (ninety) years of age at screening.
• Subject will have one or more of the following clinical diagnoses related to fluid-management issues: ESRD, Heart Failure.
• Subject and/or legally authorized person/representative is willing to undergo the Informed Consent process prior to enrollment in the study.
• Subject is a candidate for this study based on the PI's opinion and knowledge of the subject's condition.

Exclusion Criteria:

• Subject is participating in another clinical study that may affect the results of either study.
• Subject is unable or not willing to wear electrode patches as required.
• Subject has skin sensitivity to adhesive or hydrogel materials used in electrode patches.
• Subject has a pacemaker, implanted cardioverter-defibrillator, or ventricular assist device.
• Subject is considered by the PI to be medically unsuitable for study participation

Subjects will be volunteers, solicited using accepted recruitment methods, such as through clinicians associated with dialysis centers. Subjects will have a clinical diagnosis of Kidney Failure and will be currently undergoing Hemodialysis with possible related co-morbidity of Heart Failure.