959-104 The Potential Use of Impedance Cardiography as a Hemodynamic Sensor for Automated External Defibrillators

Automated external defibrillators use ECG analysis algorithms to identify ventricular fibrillation (VF) and ventricular tachycardia (VT). VT can be associated with a wide range of blood pressures and automated defibrillators determine the need for DC shock based on the heart rate alone. The incorporation of a hemodynamic sensor may improve the accuracy of an automated defibrillator. The impedance cardiogram (ICG) has been used to non-invasively measure cardiac output and its peak value, dz/dt(max), correlates well with aortic blood flow. We have developed a system whereby the ICG can be recorded at cardiac arrests through the same two ECG/defibrillator pads, placed in an antero-apical position, that are used to monitor or shock the patient. At 103 cardiac arrest calls and in 20 healthy volunteers (C) the ICG was recorded for a period of at least 10s without CPR artefact: 9 records were rejected because of poor quality. The rhythms were divided into VF, asystole (As), agonal rhythm (Ag), electromechanical dissociation (EMD), VT requiring DC shock (VTs) and VT not requiring DC shock (VTns). The ICG tracings were ensemble averaged to remove any electrical noise and dz/dt(max) was measured.dz/dt(max)CVTnsVTsEMDAgVFAsMean Ω.s-l0.6220.413*0.191*0.178*0.ll8*0.112*0.098*±SEM Ω.s-l0.0580.0410.0320.0220.0110.0100.004Number2020722201419*p<0.01 compared with C (Kruskal-Wallis)C was significantly greater than all other rhythms. VTns was significantly greater than the pulseless rhythms EMD, Ag, VF and As. There was no significant difference between VTs and the pulseless rhythms. Thus the ICG is a potential hemodynamic sensor for automated external defibrillators