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Providing a shock using a defibrillator to people with out-of-hospital cardiac arrest before the arrival of emergency medical services increases their chance of survival.

The UK survival rate is around 8%, which is lower than in other developed countries. This review found that bystander assistance through cardiopulmonary resuscitation and attaching a defibrillator increased it to 32%, compared to 12% for police or firefighters. Survival rates were even higher for people who had a rhythm that could be treated by a shock from the defibrillator, at 53% following intervention by bystanders. The higher survival rate seen following bystander assistance was probably due to the shorter time response time, although time to intervention was not reported by the researchers.

Whether it was the speed of first response or cause of cardiac arrest that accounted for these differences, it is clear that members of the public have an important role to play. Although this review did not examine training, pilot studies are investigating the potential of medical dispatch alerts for public first aiders.

Overall, the review findings support the current installation of publicly available defibrillators so members of the public can assist those with cardiac arrest until emergency medical services arrive.

Why was this study needed?

Cardiac arrest happens when a person’s heart stops pumping blood. Defibrillators can be used to shock the heart to restore a heart rhythm, but only about 20% of all out-of-hospital cardiac arrest cases are treatable by defibrillation by the time emergency services arrive.

Around 60,000 out-of-hospital cardiac arrests occur in the UK every year, and emergency services attempt resuscitation in about half of them. On average, only eight out of 100 people for whom resuscitation is attempted by emergency services in England survive to leave the hospital, and each minute without intervention reduces the chance of survival.

Prompt 999 calls and immediate resuscitation by bystanders increases the chances of the out-of-hospital cardiac arrest being treatable by defibrillation. Automated defibrillators are now becoming more widely available in public places in the UK. They can be used by untrained members of the public as they give recorded instructions, including whether the patient has a shockable rhythm.

This review is the first to assess the impact of automated defibrillator use by non-medical personnel on out-of-hospital cardiac arrest survival.

What did this study do?

This systematic review of 41 observational studies compared out-of-hospital cardiac arrest survival of 11,410 people according to the use of a defibrillator by:

  • bystanders using a public defibrillator, in 18 studies, or
  • non-medical professional first responders sent by an emergency dispatch centre carrying a defibrillator (police or firefighters) in 20 studies.

Three studies reported results for both.

The authors did not find any studies of dispatched lay first responders, such as members of the public alerted by text message to attend an out-of-hospital cardiac arrest.

The studies came from 11 high-income countries – one from the UK and most from the US. Four studies used data from defibrillator use on aeroplanes.

The primary outcome was survival to hospital discharge or 30-day survival following cardiac arrest.

The main limitations were high variability in study type, number of cases and range of survival across these case series. There was also no adjustment for the cause of out-of-hospital cardiac arrest and missing data. Also, the studies did not use a clear, single definition of first responder.

What did it find?

If a defibrillator had been attached to the patient:

  • The median survival rate was 22% (range 4% to 78% across 22 studies) if attended to by any non-medical first responder.
  • Median survival rate was higher following defibrillator attachment by bystanders at 32% (range 14% to 78% across 13 studies) than for dispatched firefighters or police at 12% (range 4% to 21% across nine studies).

If the defibrillator had been attached to the patient and they had a shockable rhythm:

  • The median survival rate was 40% (range 9% to 76% across 36 studies) if the defibrillator was attached by any non-medical first responder.
  • Median survival rate was higher if the defibrillator was attached by bystanders at 53% (range 26% to 72% across 15 studies) compared with dispatched firefighters or police at 29% (range 9% to 76% across 21 studies).

What does current guidance say on this issue?

The 2015 Resuscitation Council (UK) guidelines recommend that a solo first responder arriving at a cardiac arrest scene should prioritise attaching a defibrillator and perform defibrillation if indicated over cardiopulmonary resuscitation. For more than one responder, both should be initiated in addition to calling for assistance. They also highlight the importance of community first responders and recommend establishing public access defibrillation programs wherever possible.

The British Heart Foundation and Resuscitation Council (UK) are setting up a database of the locations of public access defibrillators across the UK.

What are the implications?

Defibrillation by bystanders showed the highest survival, which could be due to faster on-scene arrival and start of intervention, although this was not assessed in this study. Deployment of police and firefighters may have been due to the nature of the out-of-hospital cardiac arrest cases, such as from trauma, which could have affected the likelihood of successful resuscitation.

However, the general public have wide and faster access to residential areas than police and firefighters, so it is encouraging to see that they could improve out-of-hospital cardiac arrest survival rates.


Citation and Funding

Bækgaard J, Viereck S, Møller T, et al. The effects of public access defibrillation on survival after out-of-hospital cardiac arrest: a systematic review of observational studies. Circulation. 2017. [Epub ahead of print].

This project was funded by the Danish foundation TrygFonden.



NHS England. Ambulance quality indicators: clinical outcomes. London: NHS England; 2017.

Perkins GD, Brace-McDonnell SJ. The UK Out of Hospital Cardiac Arrest Outcome (OHCAO) project. BMJ Open. 2015;5(10):e008736.

Resuscitation Council (UK). Prehospital resuscitation. London: Resuscitation Council (UK); 2015.

Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre


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Shockable rhythms: Ventricular fibrillation (VF) is the most common rhythm abnormality found in people with cardiac arrest. The person is unresponsive and will die without immediate treatment. VF is completely erratic electrical activity, where the heart quivers ineffectively and no blood is pumped out of the heart. Other fast heart rhythms (tachycardias) can occur around the time of cardiac arrest and may precede VF. Ventricular tachycardia is a pulse of more than 100 beats per minute caused by abnormal electrical signals coming from the lower heart chambers (ventricles). This is characterised by broad complexes on electrocardiogram. Supraventricular tachycardias, like atrial fibrillation or atrial flutter, are where the abnormal electrical activity is coming from above the ventricles (e.g. the atria).Non-shockable rhythms: Asystole is total cessation of electrical activity from the heart, commonly known as flat-lining due to appearance on electrocardiogram. As there is no activity coming from the heart, using a defibrillator will have no effect.  Pulseless electrical activity is where there is a heart rhythm that should produce a pulse, but does not. 
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