Specific impedance of canine blood.

The specific impedance of canine erythrocytes suspended in plasma was measured in the frequency range from 5 kHz to 1 MHz in samples from three animals in the hematocrit range from zero to packed cells at a temperature of 39 degrees C; measurements were made with a conductivity cell using four electrodes and a current density of 21 microA/cm2. With the use of impedance spectroscopy, data were fitted to an equivalent circuit model; model parameters in turn were fitted as functions of hematocrit. The resultant model can be used to predict specific impedance (real and reactive components) as a function of hematocrit and frequency over a frequency range from 5 kHz to 1 MHz and a hematocrit range from 0 to 80. Over a normal range of hematocrits and at frequencies less than 100 kHz, the current is almost exclusively confined to the plasma, and the specific impedance is nearly equal to the real component; however, at higher frequencies, the complex nature of specific impedance becomes important.