Abstract 16068: Evaluation of Current-Based Impedance Compensation Defibrillation in Pre-Hospital Sudden Cardiac Arrest with Different Transthoracic Impedances
Introduction: Modern external defibrillators use impedance compensation techniques because the transthoracic impedance (TTI) is a major factor which influences the intracardiac current flow during electric shock and defibrillation success [1, 2]. Our previous study demonstrated that current-based compensation outperformed duration-based compensation technique in a pig model of cardiac arrest . In this study, we evaluated the performance of current-based impedance compensation technique in pre-hospital cardiac arrest patients and related the shock success to the TTI measurement.
Methods: ECG recordings, along with TTI measurements between two shocking pads, were collected from multiple emergency medical services (EMS) in the USA through a regular field case submission program sponsored by ZOLL Medical Corporation. All the EMSs in this study use ZOLL AED which employs current-based impedance compensation technique. The electronic data do not contain patient identifiable information. The ECG tracings were annotated by one independent doctor and verified by another independent doctor in order to enhance the data accuracy. Shock success was defined as an organized rhythm that was present for a minimum of 30 seconds, started within 60 seconds after the shock, and had a rate of 40 beats per minute or greater.
Results: 632 shocks from a total of 300 patients were analyzed in this study. The shock success rate remained unchanged over the whole spectrum of TTI from 50 ohms to 250 ohms (average success rate is 22.5%, 23.0% for low impedance and 21.8% for high impedance shocks, p=0.77). No significant difference in odds of shock success over TTI was observed (OR=0.998, p=0.23, 95% Conf. Interval=0.994 to 1.0001).
Conclusion: The defibrillators with current-based impedance compensation technique performed equally well in the whole range of TTI in the pre-hospital cardiac arrest.
- © 2010 by American Heart Association, Inc.