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

Background: 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.

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

Methods: 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.

Results: 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.

Conclusions: 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.