No invasive measurement of urea in blood based in optical sensing for Hemodialysis treatments

The present work shows the development of a low-cost system to measure on-line blood urea concentration during dialysis procedures using optical sensor in the visible range. The objective in this project is obtaining the quantification of urea on-line during practices of the hemodialysis treatments. For which it has been considered to be a hypothesis that the dependence in the volume change of the red globules with the urea concentration in the blood is due to the changes to the osmotic pressure and to the mechanisms of regulation of the cellular volume. A bigger concentration of urea would imply a reduction of the volume of the cells and, therefore, a decrease of the optical absorbance. To validate this hypothesis, we used a simplified cellular model based on a yeast cell suspension. Measurements at urea concentrations using a custom single wavelength absorbance meter, and electrical impedance measurements system as contrast technique. Finally to validate this system have carried out thirty mensurations among diverse patient subject a Hemodialysis treatment in the Military Hospital Centre in Mexico, City.