New applications of electrical impedance of human blood

Abstract

The electrical impedance parameters of human blood, that is, plasma resistance R_p, cell interior resistance R_i; and cell membrane capacitance C_m, were determined by measuring impedance amplitudes at three different frequencies, 0 1, 0.8 and 1.2 MHz. Several new findings have been obtained. The fibrinogen in normal blood raised R_p, and C_m, by about 4 % and 20%, respectively, and serum proteins contributed to the capacitance by about 14 %. The results imply that the electrical impedance of blood may reject certain diseases that involve abnormal compositions of certain plasma proteins. Measurement on 62 samples with various erythrocyte sedimentation rates (ESR) demonstrated that both R_p, and C_m, were proportional to ESR, implying that the impedance measurement might be an alternative method for quick estimation of ESR. During in vitro storage of blood at 4°C, both R_p, and C_m, decreased with time, about −20% for C_m, after four weeks J storage. The results imply that the impedance change might be a useful index for evaluating the quality of stored blood.