Improvement of electrical blood hematocrit measurements under various plasma conditions using a novel hematocrit estimation parameter.

This paper presents an electrical method for measurement of Hematocrit (HCT) using a novel HCT estimation parameter. Particularly in the case of electrical HCT measurements, the measurement error generally increases with changes in the electrical conditions of the plasma such as conductivity and osmolality. This is because the electrical properties of blood are a function not only of HCT, but also of the electrical conditions in the plasma. In an attempt to reduce the measurement errors, we herein propose a novel HCT estimation parameter reflecting the characteristics of both the changes in volume of red blood cells (RBCs) and electrical conditions of plasma, simultaneously. In order to characterize the proposed methods under various electrical conditions of plasma, we prepared twelve blood samples such as four kinds of plasma conditions (hypotonic, isotonic, two kinds of hypertonic conditions) at three different HCT levels. Using linear regression analysis, we confirmed that the proposed parameter was highly correlated with reference HCT (HCT(ref.)) values measured by microcentrifugation. Thus, the HCT measurement error was less than 4%, despite considerable variations in the conductivity and osmolality of the plasma at conditions of the HCT(ref.) of 20%. Multiple linear regression analysis showed that the proposed HCT estimation parameter also yielded a lower measurement error (1%) than the other parameter previously used for the same purpose. Thus, these preliminary results suggest that proposed method could be used for accurate, fast, easy, and reproducible HCT measurements in medical procedures.