Abstract 1811: Pauses for Defibrillation Not Necessary During Mechanical Chest Compressions during Pre-hospital Cardiac Arrest
Use of mechanical chest compression (CC) devices may improve resuscitation outcomes following pre-hospital cardiac arrest by reducing pauses in CCs. Currently manual CCs are interrupted for defibrillation. We tested two hypotheses:
the defibrillation threshold (DFT) varies with shock timing with respect to compression phase, and
randomly timed shocks delivered during ongoing CCs do not have a higher DFT than shocks during a 3–5 s pause in CCs.
Methods: Defibrillation patches were placed on the left and right anterior chest walls of six anesthetized swine. A LUCAS mechanical CC device was positioned. Ventricular fibrillation (VF) was induced and allowed to continue for 75 s; CPR was performed for the last 30s before defibrillation. DFTs, using the McDaniel-Dixon up-down technique, were measured randomly for 6 shock timings:
at the beginning of compression,
at the end of compression,
at the beginning of decompression,
at the end of decompression, (5- Random) randomly during CC, and (6- Pause) following a 2–3 s pause in CCs.
Failed shocks were quickly followed by a larger shock known to succeed. CCs were continued until spontaneous circulation returned. Ten minutes elapsed between VF episodes.
Results: The DFT was significantly higher for timing 1 compared to the other 5 shock timings (ANOVA, p<0.05). There was no significant difference in DFT between shocks delivered randomly during CCs and shocks delivered during a CC pause.
Conclusions: DFTs can vary depending on the phase of CC when the shock is delivered. Shocks can be delivered during ongoing mechanical CCs without compromising efficacy, removing the need for potentially detrimental pauses in CCs.