Dialysis at home – DIALYDOM

WP1 will establish the requirements for the clinic and home-based dialysis monitoring scenarios and systems. The key dialysis co-morbidity factors must be studied to identify suitable ways of assessing these additional factors, especially for the home-based scenario. A clear, simple protocol must be established to assist patients and ensure compliance and proper operation of the system in the physical absence of medical staff.
WP2 will investigate, largely from a purely scientific point of view, the optimal design, area, shape, orientation, number and arrangement of electrodes to best target the desired tissues where patient hydration variation is electrically visible and thus enable accurate, repeatable localised measurement of hydration, or body on dialysis patients. The necessary current densities, applied frequencies (range and number), equivalent circuits or models, impedimetic parameters to be extracted, etc will be established
An important intermediate step in the development and testing of a home-based is the development of a device for clinical use (WP3). This device will be an upgrade of the BioparHom dialysis monitoring system based on existing interface software (using a personal computer). It will be used with a new impedimetric electrode system, a disposable version of that developed in WP 2 enabling more localized convenient measurement. The electrode array will be applied by clinical staff
WP5 involves the final clinical validation of the two devices developed in WP3 and 4
The final clinical validation of the devices will involve their comparison against the “gold standard” method of body water assessment, isotope dilution with oxygen-18 and with deuterium
WP0 will address the issues related to the management of the project. It will also address the aspects involved in the development of a “Medical Device” – relevant standards, risk analysis, ethical approval, organisation and running of clinical trials

Commercial devices found to be sensitive to electrode-skin contact impedance in our localized measurements, causing gross distortion of recorded impedance data and thus adversely affecting the accuracy of the calculations – need better electrodes and/or improved circuitry
We assessed commercial electrodes, and assembled prototype electrodes of our own and tested against these supplied by BIA suppliers. Result: our prototype electrodes out-performed those supplied with/for the BIA equipment, thus minimizing the distortion problems.
- Investigation of the effects of electrode placement on the sensitivity of the monitoring of the patient’s hydrational status. Discussion with the clinicians concerning the tissues to be targeted by the applied electrical field influenced the design of our measurement setup in order to concentrate on these tissues. Anisotropic nature of muscle was considered – which can assist in the targeting of tissues by channeling the electrical current or lead to failure of the field to penetrate the relevant tissues. Several novel electrode configurations assessed. The work involved numerical simulations of the calves (FE software Comsol Multiphysics™) with geometries deduced from MRI data segmentation; the building and testing of a range of custom built phantom models of the leg and carrying out some invivo measurements on the calves of healthy subjects. Result: electrode layout significantly influences the areas of tissue targeted and hence the sensitivity of the technique in monitoring the hydrational status of the subject. Identification of more promising arrangements than the “traditional” Zhu configuration

By systematically assessing all aspects of the technology, we have improved the electrode performances, the electrode positioning and hence improved the accuracy of the BIA system measurements. This has already led to the publication of several conference papers and, possibly, journal papers and patents are envisaged, based on the ongoing research and novel discoveries.
The improvement of the electrodes, software and hardware will not only benefit the targeted home-based localised BIA device, but should additionally improve the accuracy of the existing “whole-body” systems used in clinics
The three most promising electrode arrangements will be clinically assessed shortly on dialysis patients using a standard BIA system and groups of standard hydrogel electrodes grouped together to form composite electrodes of the desired size and shape. Based on the outcome of these preliminary tests, a final electrode harness will be designed and manufactured for the formal clinical trials of localised BIA assessment of hydration in dialysis patents

Invited Conference Presentation :
1 - “Bio-impedance spectroscopy: Problems to avoid” E. McAdams, Special Session on Special Sessions on Bio-electronic Interfaces, 9th Conference on Design and Technology of Integrated Systems in Nanoscale Era (DTIS), Santorini, Greece. 6-8 May 2014.
2 - “The Biomedical Electrode-Tissue Interface: A Simple Explanation of a Complex Subject” E. McAdams. Seminar on Biomedical and Sensor Interface Circuits, ISSCC 2014 San Francisco, USA 9-13 Feb. 2014
International Conference Publications
1 - “Effect of electrode contact impedance mismatch on 4-electrode measurements of small body segments using commercial BIA devices” P. Bogónez-Franco, P. Pham, C. Gehin, B. Massot, G. Delhomme, R. Guillemaud, E. McAdams., 20th IMEKO TC4 International Symposium and 18th International Workshop on ADC Modelling and Testing Research on Electric and Electronic Measurement for the Economic Upturn, Benevento, Italy. September 15-17, 2014.
2 - “Problems encountered during inappropriate use of commercial bioimpedance devices in novel applications” P. Bogónez -Franco, P. Pham, C. Gehin, B. Massot, G. Delhomme, R. Guillemaud, E.McAdams. 7th International Workshop on Impedance Spectroscopy. Chemnitz, Germany. September 24-26 2014.
3 - “Design Of Bioimpedance Sensors: Unique Study Tool Composed Of Saline Phantoms, Numerical Modeling And Impedance Spectroscopy” Pascale Pham, Paco Bogonez-Franco, Eric McAdams. 7th International Workshop on Impedance Spectroscopy. Chemnitz, Germany. September 24-26 2014.

The project’s goal is the development and eventual commercialisation of a valid, robust, integrated and convenient-to-use, wearable, wire-less, hydration-monitoring system based on localised impedimetric measurements on the leg for self-application and use by dialysis patients, especially for those undergoing dialysis at home.
Chronic Renal Failure (CRF) is one of the leading causes of death in the world. Approximately 1 in 10 citizens suffer from some form of renal disease (the number is increasing) and, given the high cost of treatment, in the form of dialysis or renal transplant, CRF is a top priority in modern health care.
The home-based self-monitoring of dialysis patients has been identified as being a key requirement in addressing the challenges (in the form of quality and cost of treatment) which presently face national health care providers, as clearly articulated, for example, in France’s Regional Health Organisation Scheme (4th version). In order to achieve this goal however, there is an identified need of a convenient and robust non-invasive technique capable of remotely assessing the hydrational status of home-based patients with renal insufficiency to detect and/or avoid life-threatening complications linked to both under- and over-hydration.
Over the past few decades, Bioelectrical Impedance Analysis (BIA) has shown promise as an objective, non invasive method of detecting and evaluating changes in the hydration and nutritional status of patients with renal disease and it is now accepted in the clinical setting. Efforts are being presently made to modify this technique, which requires cumbersome leads attached to the limbs. Unfortunately the electrodes used have simply been standard ECG electrodes manually placed on the patient. Not only is this less than user-friendly for a dialysis patient, it has been found that even very slight differences in electrode placement or electrode properties can have a significant adverse effect on the measurement.
The present consortium therefore brings together leading specialists in the use of BIA, in the treatment and monitoring of Dialysis patients, in the study and modelling of the electrical properties of tissues and electrode interfaces, in microfabrication of sensors and associated circuitry and in the design and development of electrode arrays, in particular those for electrical impedance measurements on the human body. The partners include leading research laboratories in INSA and CEA-Leti, an SME producing a BIA system specifically for Dialysis monitoring (one of only two in the world) and a specialist Clinic dealing with the monitoring of dialysis patients.
The consortium will improve the design of the electrodes, the measurement technique design, and the streamlined electrode harness to ensure accurate positioning of the electrodes. The associated electronics will be miniaturised and integrated into the body of the electrode harness to avoid the presence and danger of cumbersome dangling leads. The electronics will include an accelerometer to monitor the position and stability of the leg during the measurement, and a BlueTooth link for the interface with an external device for the user interface (basically a smart-phone).
The Dialydom project is perfectly aligned with the first theme of the TECSAN call: development of technologies for Health