Abstract 152: Impact of Shock Timing During Mechanical CPR on Defibrillation Efficacy
Background: Mechanical CPR (mCPR) devices enable defibrillation shock delivery during ongoing chest compressions, without the pause required during manual CPR. It is unknown whether shock delivery during ongoing mCPR, vs. during a pause, affects VF termination efficacy. Animal studies suggest that during ongoing mCPR, timing a shock to a specific phase of the compression cycle may significantly affect shock efficacy.
Methods: We retrospectively analyzed electronic defibrillator recordings from the Amsterdam Resuscitation Study (ARREST), a prospective out-of-hospital cardiac arrest registry. We identified cases with LUCAS mCPR and at least one shock delivered after mCPR initiation. Shocks were sorted by energy level, and the most prevalent (360 J) was selected for the present analysis. Continuous ECG and impedance signals were analyzed to determine VF termination (defined as absence of VF at 5 sec after shock) for each shock after mCPR initiation, and whether the shock was delivered during a pause or during mCPR. For shocks delivered during a pause we measured pre-shock pause duration; for shocks delivered without pausing we measured the exact timing of the shock during the compression cycle.
Results: In 153 cases meeting analysis criteria, 509 360J shocks occurred after mCPR initiation; VF termination outcome could be determined for 460. VF termination for first eligible shock during mCPR in each case was 84/97 (87%) during a pause, and 79/93 (85%; p=0.74) during ongoing mCPR; for all eligible shocks, VF termination was 203/242 (83.9%) and 155/196 (79.1%; p=0.20) respectively. For shocks during mCPR, there were no statistically significant differences in VF termination rate for shocks during four equal length phases beginning with LUCAS piston upstroke: 39/44 (89%), 39/49 (80%), 35/51 (69%), 40/50 (80%) (p = 0.12). For shocks during a pause, VF termination rate did not differ for pre-shock pauses ≤5 sec (75/91, 82.4%) vs. >5 sec (128/151, 84.8%; p=0.63).
Conclusions: Our results indicate that shocks can be delivered during ongoing mCPR without reducing defibrillation efficacy. The exact shock timing during the mCPR compression cycle did not significantly alter shock efficacy. VF termination rate was not affected by pre-shock pause duration during mCPR.
Author Disclosures: R.G. Walker: Employment; Significant; Physio-Control. A. Esibov: Employment; Significant; Physio-Control. F.W. Chapman: Employment; Significant; Physio-Control.
- © 2014 by American Heart Association, Inc.