Time matters; what is the time in your defibrillator? An observational study in 30 emergency medical service systems

Measuring different intervals during cardiopulmonary resuscitation is a key element of resuscitation performance. For accurate time measurements, the internal clocks of automated external defibrillator (AEDs) need to be synchronized with the dispatch centre time.

To determine the present practice of using and synchronizing the AED clocks in five regions in Finland.

During a single morning, the time of all AED clocks in the emergency medical service (EMS) systems of five large hospital districts were checked and compared with the dispatch centre time. A questionnaire about synchronisation policy and documentation of the first defibrillatory shock was also e-mailed to the local EMS medical supervisors.

Eighty-eight AEDs were checked in 30 EMS systems. The mean deviation from dispatch centre time was 412 (+/-1001) s. There was no difference between EMS systems with (N = 7) or without (N = 23) written guidelines regarding synchronisation. Many EMSs reported that they document the time of the first shock without synchronisation of clocks.

Synchronisation of AED clocks is not widespread in Finland. Instructions to synchronize have been issued in a minority of EMS systems. Despite this, time deviations are large, and erroneous times are recorded.