Abstract 118: Distribution of Transthoracic Impedance Measured in Pre-Hospital Sudden Cardiac Arrest
Introduction: Successful defibrillation is dependent upon the delivery of adequate electrical current to the myocardium. The transthoracic impedance (TTI) is a major factor which influences the intracardiac current flow and therefore defibrillation success . Earlier studies suggested that repetitive shocks resulted in a decline in TTI . TTI measurements in pre-hospital SCA are scarce and the change in TTI during repetitive biphasic shocks is still controversial [3–5]. In this retrospective study, we collected and characterized TTI data from pre-hospital SCA recorded in automated external defibrillators (AEDs).
Methods: Data were collected from adults patients undergoing out-of-hospital cardiopulmonary resuscitation received sequential escalating transthoracic shocks (120J, 150J and 200J) from AEDs with current compensated rectilinear biphasic waveform (AEDPLUS and AEDPRO, ZOLL Medical Corporations). TTI was calculated and recorded through AEDs electrically. The effects of sequential shocks on TTI were then analyzed.
Results: 1513 shocks from a total of 749 patients were analyzed. The distribution of TTI among the patients was shown in figure 1.The mean TTI for the first shock was 133 ohms (range from 50 to 300 ohms). A significant decrease in TTI was observed for the 2nd shock (126±34 vs. 133±45, p<0.001). TTI did not change after the 2nd shock (125±35 for the 3rd shock, 127±36 for the 4th and 123±36 for the 5th).
Conclusions: The mean TTI was significantly higher in pre-hospital SCA as compared with the mean value of 100 ohms previously reported . The TTI was decreased during the 2nd repetitive shock and remained unchanged for the rest of repetitive shocks in this study.
- © 2010 by American Heart Association, Inc.