Examining the potential of using thorax impedance measured by automated external defibrillators for quantification of circulation

It has been suggested to acquire circulatory information from patients undergoing resuscitation from cardiac arrest by analyzing their thoracic electrical impedance using modified automated external defibrillators (AEDs). To investigate the potential of this idea, we studied the correlation between two impedance-derived parameters related to circulation, the negative peak of the impedance fluctuation (Z_peak) and its first time derivative (dZ_peak), and arterial blood pressure measurements in 26 patients undergoing resuscitation and 32 hemodynamically stable patients. The highest correlation coefficient, rho=0.4338 was found between the systolic blood pressure and the magnitude of the negative peak of the first time derivative of the impedance. The poor correlation indicates that the impedance-derived parameters are not suitable for quantification of circulation, but can be used to indicate circulation