Beyond the pre-shock pause: the effect of prehospital defibrillation mode on CPR interruptions and return of spontaneous circulation.

AIMS: The pattern of interruptions to chest compressions in pre-hospital cardiac arrests in Wellington, New Zealand, was examined prospectively to determine whether the mode of defibrillation chosen by paramedics influenced interruptions, shock success and the return of spontaneous circulation (ROSC).

METHODS: A prospective observational cohort study of 44 adult cardiac arrests in which 203 shocks were administered by Wellington Free Ambulance (WFA) paramedics was undertaken to compare Code-stat electronic records from Medtronic Lifepak 12 and Lifepak 15 defibrillators used in semi-automated (AED) or manual mode. Interruptions during the 30s prior to shock delivery as well as pre-shock and post-shock pauses were calculated. Shock success and ROSC were the outcome measures.

RESULTS: Pre-shock pauses were shorter in manual mode (median 3s, IQR 2-5) versus AED mode (median 4s, IQR 3-6; p=0.003). Interruptions of CPR in the 30s prior to shock delivery were also shorter in manual mode (median 7s, IQR 4-11) versus AED mode (median 14s, IQR 12-16; p=<0.001). Shock success rates and post-shock pauses were not statistically different between modes. ROSC was significantly higher in manual mode (18.49%) versus AED mode (8.33%, p=0.042).

CONCLUSION: When paramedics used the defibrillator in manual mode as compared to AED mode, interruptions to CPR during the 30s prior to shock delivery were significantly reduced and pre-shock pauses were also shorter. This was associated with increased ROSC. Manual defibrillation should be the preferred option for appropriately trained paramedics. Training in this locality has been changed accordingly.