Noninvasive Measurement of Hematocrit by Electrical Admittance Plethysmography Technique

A new method for the noninvaive measurement of hematocrit by means of electrical admittance plethysmography was developed. The pninciple of this method is based on the evidence that the elecical admittance variation in a finger segment inmersed in an electrolyte solution disappears when the resistivity of the solution is equal to that of the blood flowing into the segment. Thus, the blood resistivity and, therefore, the hematocrit can be noninvasively determined from the electrolyte resistivity. The hematocrit values determined by this method (HctY) were compared with those by the capillary method (Hctc) in 16 subjects: the linear regression equation was HctY = 1.02Hctc-0.35 with a correlation coefficient r = 0.981.