TABLE 1.

Comparison of technological differences between bioimpedance and bioreactance.

	Bioreactance	Bioimpedance
Assumptions regarding blood flow	Related to change in body’s resistance, capacitance, and inductance	Related to the change in body’s resistance only
Anatomical assumption regarding thorax	Thorax is an electrical circuit with resistor and capacitor	Fluid-filled cylinder or truncated cone
SV estimation	Calculated from phase shift, determined from resistance and capacitance [amplitude magnitude of impedance and phase direction of impedance (Z0)]	Calculated from estimated changes in resistance/impedance (Z0) – electrical current flow over time due to aortic blood flow changes
SV calculation	Peak rate of change of the phase shift (dφ/dtmax) is proportional to the peak aortic flow from which SV is calculated (eq. 2)	Instantaneous rate of change in Z0 is related to aortic blood flow and SV is proportional to the maximal rate of change of Z0 (dZ0/dtmax) and the ventricular ejection time (VET)
Electrode placement	Applied at the base of the neck (thoracic inlet) and costal margins (thoracic outlet) on both sides. Measurements are sensitive to electrode placement	2 pairs of dual-electrode sensors – placed on the left thorax and right neck Measurements stated not to be sensitive to placement
VET determination	VET is determined by BR (first and second zero crossing of the dφ/dt signal) and electrocardiographic signals (peak of the QRS complex)	VET is determined by the distance between QRS complexes

Modified from Jakovljevic et al., (17) dZ0/dt, impedance change over time; VET, ventricular ejection time; Z0, impedance; dφ/dt_max, peak rate of change od change of phase shift.