On-Line Measurement of Blood Urea Based in Optical Sensing by Employ in Hemodialysis Treatment

The present paper shows the design and development the On-line measure system of the blood urea concentration during dialysis procedures, using non-invasive technical by employ the optical sensing in the visible range. Previous results obtained in Military Hospital Centre in Mexico displayed experimental evidence of a clear correlation between blood urea contents and optical absorbance in the red region obtained through the arterial line in hemodialysis machine. Our hypothesis considers that the cause of this dependence is the volume change of the red cells with the urea concentration due to the osmotic pressure and to the mechanisms of regulation of the cellular volume. The reduction of the volume of the cells would lead to a decrease of the optical absorbance. Measurements were first performed during experimental dialysis procedures, clinical measurements were carried out on a group of patients during hemodialysis procedures in Mexico City. The most relevant interfering parameter was the water extraction along the dialysis treatment, given that changes in the blood fluid and arterial pressure (Hypotention or Hypertention), thus affecting the measurement principle.