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Rapid defibrillation is the best method for resuscitating victims after sudden cardiac arrest. Experimental and clinical studies have shown that electrical shocks applied within 30 s of ventricular fibrillation (VF) can produce a 98% rate of resuscitation. However, when the shock is delivered after 7 min of VF, the resuscitation rate falls to 27%. This has given rise to the ‘goal’ of early defibrillation in out-of-hospital cardiac arrest (OHCA).
Over the past 30 years or so, advances in technology have provided innovative opportunities in the area of automated external defibrillator (AED) technology. Defibrillation within 5 min is the only effective means of returning a heart in VF to its normal rhythm. The use of AEDs can help to achieve the objective of reducing mortality in OHCA.
In most cases it is all but impossible to predict who will have a sudden cardiac arrest, or where and when it will happen. What we do know is that each day more than 1000 Europeans suffer from sudden cardiac arrest, usually away from the hospital, and that the ambulance arrives too late. Of course, for some patients the chance of survival is down to luck. A patient is nine times more likely to survive if he/she is observed having the arrest. But even if witnessed, the chance of surviving mainly depends on immediate access to a defibrillator.
For almost two decades, Rochester and Seattle in the USA have reported consistent survival rates of 30–40% for witnessed VF—about three times the US and European average—utilising an organised two tiered system of early defibrillation and public access defibrillation (PAD).1 Comparatively, the survival rates from performing basic cardiopulmonary resuscitation (CPR) alone are reported at between 0–6%, a rate that has not improved since the 1950s.2 Although much money and effort have been spent by scientific communities in training people to perform CPR, about three out of four bystanders who have a chance to perform it choose not to do so on a stranger, due to fear of infection or an aversion. Theoretically, at least 30% of lives could be saved if targeted members of the general public could obtain early access to and have training in the use of AEDs (table 1). In addition, it has not been demonstrated that CPR performed before defibrillation increases survival,3 especially when an AED is available.4
Survival rate from ventricular fibrillation in different places. The time to shock is the major determinant of survival if the AED is readily and quickly available
AEDs are intended to be operated by all individuals, regardless of whether they have received proper training or none at all, due to their ease of use. The value of the AED technology is that an AED will not energise unless an appropriate shockable cardiac rhythm is detected. As is the case in most clinical developments, the science supporting its efficacy in controlled settings usually precedes evidence of effectiveness when implemented on a large scale in real world settings. Unfortunately, PAD programmes are not very widespread in Europe and still represent an exceptional way to approach sudden cardiac arrest.
Do PAD programmes improve survival?
The core concept of the PAD strategy is to bring the defibrillator into the incident sooner than a fully equipped emergency medical services (EMS) unit can reach the location.5 The ease of use of AEDs by the trained (and untrained) lay public has led to the increasing development of PAD programmes. The decreased cost of acquisition and upkeep of AEDs now makes it possible to increase further the availability and access to these lifesaving devices.
Many studies, including a large randomised trial, have shown that a PAD programme can improve the rate of survival among patients who have had an OHCA.6–13 The Resuscitation Outcomes Consortium (ROC) established a population based registry for OHCA and resuscitation called the ROC Epistry Cardiac Arrest registry,14 to test the hypothesis that despite possible delays or errors associated with AED application, cardiac arrest patients who have an AED applied before EMS arrival experience better survival than those who do not have an AED applied. The findings of this investigation support the significant and important beneficial impact of PAD programmes in community based settings. On average, early AED defibrillation before EMS arrival seems to nearly double a victim's odds of survival after OHCA. These results strongly support strategic expansion of PAD programmes, particularly in public locations.
Another recent community based study, the Public Access Defibrillation Trial,8 trained volunteers at both control and AED sites and showed a doubling of the number of survivors (30 vs 15; p<0.03) at sites with AEDs compared with sites without AEDs. Automated defibrillators were placed in approximately 1000 public locations in 24 cities, including shopping centres, sports facilities, office buildings, community centres, factories, entertainment venues, apartment buildings, and schools. Volunteers who worked in these locations were trained to perform CPR or trained to perform CPR and use the automated defibrillator. After 2 years and 292 resuscitation attempts, the overall survival rate for the study was still very low (15%), but the use of automated defibrillators saved almost twice as many lives as CPR alone. This shows automated defibrillators can save lives when used by lay people trained to operate AEDs.
The results of the recent Nationwide Public-Access Defibrillation study in Japan,11 the largest public access defibrillation programme organised to date, showed an increase in survival with minimal neurologic impairment due to the increased number of public access AEDs. During the 3 year study period, the number of AEDs increased from 9906 to 88 265. This large, population based, observational study clearly confirmed the positive effect of the dissemination of public access AEDs on improving survival after out-of-hospital VF arrests witnessed by bystanders. According to the authors, if the number of public access AEDs increased from one per square kilometre (ie, a unit placed every 1000 linear metres) to more than four per square kilometre (ie, a unit placed every 500 linear metres), the rate of survival with minimal neurologic impairment in the area could increase by about four times, saving thousands of lives. This finding reinforces the importance of PAD for increasing survival after OHCA.
What could increase the implementation of PAD in the community?
Today's AEDs are relatively inexpensive and can be used by individuals with limited training. The advantage of well structured PAD programmes is that they increase the potential to reduce response times and notably increase the probability of survival and full recovery. At the same time, implementation of a PAD programme requires members of the community to be trained quickly to recognise a possible cardiac arrest, and that a mechanism for immediate communication of the event and activation of an EMS response is in place to ensure that fully trained EMS personnel can arrive swiftly at the scene after prompt defibrillation by lay responders.
We agree that a PAD programme does not mean merely installing AEDs as an isolated measure in an attempt to prevent sudden death. Such an approach does not increase survival. Indeed, in an effort to improve survival from cardiac arrest, PAD programmes have to promote the chain-of-survival concept with sequential steps in the pre-hospital phase that result in improved survival. These interventions include rapid access to the EMS by calling a single emergency number that can co-ordinate the first responders and the members of the ambulance team. Survival depends directly on the time to defibrillation, and early defibrillation has emerged as the most important intervention, with survival decreasing by 10% with each minute of delay in defibrillation. Public education and mass media support must therefore form the basis of a PAD programme.
Unfortunately, only about 10–15% of cardiac arrests occur in a public place and even fewer are witnessed. This is the reason why a PAD programme should be introduced into the current despatch system, which should also involve policemen, fire fighters and volunteer laypersons whose primary job does not include the responsibility of providing medical assistance in emergencies. Coordination of first responder intervention with EMS must be included as an important element for the success of the PAD programme.15 However, studies on fire fighters and policemen using AEDs have shown conflicting results.16–18 Most studies showed a reduction in time to first shock, but did not show a statistically significant improvement in survival rate. Many limiting factors such as low rate of bystander CPR, delays in collapse/recognise-to-call receipt time interval, or the Hawthorne effect in the EMS after implementation of first responder AED programmes, may explain these conflicting results.19
Other studies, however, have shown encouraging results for people using AEDs in their immediate working environment. A 40% survival rate for patients in VF has been achieved by flight attendants.7 Valenzuela et al7 reported that the use of AEDs in 105 patients in casinos by security officers resulted in a survival rate of 53% for patients in VF, with a mean collapse/recognise-to-first defibrillatory shock time interval of 4.40±2.90 min. The mean time for a paramedic to arrive at the scene in this study was 9.80±4.30 min. A total of 86% of the collapses were witnessed. If the patients in VF were divided into those who were defibrillated within 3 min and those for whom the time to defibrillation was longer, the survival to hospital discharge rates were 74% and 49%, respectively, emphasising the importance of a short collapse/recognise-to-first defibrillatory shock time interval.
In our experience from the Piacenza Progetto Vita project, in which the first responder volunteers were trained to use the AED only without CPR, survival rates from VF tripled from 14% to 39.8% after 2 years of the project.10 These preliminary results have been confirmed after 10 years by increasing the number of AEDs and the number of lay volunteers, and even better results were achieved when policemen were involved in AED application (63% survival rate).20
Where should PAD programmes be implemented for maximum cost effectiveness?
It is becoming increasingly common for AEDs to be placed in locations with significant public traffic or density, such as stadiums and other event venues and airports. Becker et al3 divided public locations of cardiac arrest into high and low incidence sites. High incidence refers to an annual incidence of cardiac arrest of 0.03 or more per site (one arrest per 30 sites in 1 year), and low incidence is 0.01 or less per site (one arrest per 100 sites in 1 year). Some of the higher incidence sites identified by Becker et al were airports, prisons, shopping malls, and sports venues. It is reasonable that areas with a population density of fewer than 100 persons per square mile received little benefit from AEDs. Local assessments may help in achieving efficient public AED location.
AEDs in schools
Another recent recommendation is that AEDs should be placed in all schools with a reasonable probability of a cardiac arrest over the next 5 years, those with any student at high risk for cardiac arrest, or those with an emergency call to shock time >5 min. These recommendations were made with consideration of the available data on locations of cardiac arrest, and recognition that schools have a lower frequency of cardiac arrest than many other public locations.21 In Washington the estimated probability of AED use to treat sudden cardiac arrest was one in 154 schools per year. Over half of Washington State high schools have an AED on school grounds. AED use occurred in <1% of schools annually and was effective in the treatment of sudden cardiac arrest.22
What about home defibrillation?
Eighty five per cent of cases of sudden cardiac arrest occur in the home. A 2008 study in the USA by the National Heart, Lung, and Blood Institute and the National Institutes of Health found that AEDs in the home are safe and effective. However, the benefits of home-use AEDs are still debated. In the HAT study the access to home AED did not significantly improve overall survival compared with reliance on conventional resuscitation methods, in the particular setting of post-myocardial infarction patients.9 The very low event rate and the high proportion of unwitnessed events appear to explain these unexpected results. Even so, the overall survival of 12.0% (18.3% for witnessed events) was significantly better than the 2% survival rate previously reported in the general population at home. The odds of surviving cardiac arrest may depend on where the individual lives and whether anyone in the neighbourhood can come to the rescue by attempting to perform CPR and apply an AED. A new study has revealed a strategy for reversing stagnant survival rates.23
AED training for PAD
Initial training and certification, skills maintenance, and recertification should be simplified for lay responders in the community. One may be concerned about the training of lay persons, and members of the disciplined services (police and fire) are thought to be more easily trained. Studies have shown, however, that lay persons, including sixth grade children, can be trained to use an AED.24 The America Heart Association (AHA) and the International Liaison Committee on Resuscitation (ILCOR) state that the initial training for a first responder in a PAD programme should be approximately 4 h. Numerous studies of alternative AED training courses have shown equivalent or better outcomes as compared to standardised instructor led and directed courses.25–27 In some studies, instructor led courses used non-standardised teaching methods and techniques such as computer based training and retraining, with good results. A study was conducted comparing the standard AHA AED course lasting 3–4 h, involving AED skills practice, versus a 30 min ‘watch-while-you-practice’ video based CPR course providing only a verbal discussion of the AED without a skills practice. The investigators found that the shorter training course resulted in better performance of AED skills at the immediate post-instructional and 6 month testing episodes than did the standard length AHA course. Also, children can learn to use an AED after a brief viewing of a video, and their performance in applying it demonstrates the simplicity and safety of the AED operation.28
An analysis of the traditionally taught, instructor led North American PAD trial proposed that modification of the teaching method used for the lay providers might have improved their participation and performance in dealing with sudden cardiac arrests had the training been made more congruent with their social, employment, ethnic, and personal backgrounds. The comment was made that training that was more content and skills driven, rather than being formally didactic and technical, would transfer the educational content into actual practice better had the training been more individualised.29 Surprisingly good results have been reported by Caffrey et al on the experience at Chicago airports, where the public use of AEDs by untrained passengers resulted in very high survival rates for patients who experienced a cardiac arrest where an AED was placed at 80 m walking distance, and video projections showed how to use them.6
In summary, for lay and healthcare basic life support providers requiring AED training, the simpler the training the better, both for initial performance and skills retention. Because of the cognitive nature of AED training and the guidance provided by the device itself, the only significant effect of instructor intervention was in the placement of the pads and the encouragement given to the providers to actually use the device. In table 2 we summarise how training may be simplified in lay volunteers and in schools.
AED training should be as simple as possible: a summarised scheme of training according to the category of volunteers and students' age
Conclusion
As the most common cause of death in Europe, sudden cardiac death accounts for nearly 400 000 fatalities every year. More than 20 000 deaths could be prevented each year if AEDs became more widely available to first line responders such as police officers and fire department personnel. A substantial body of robust clinical data, including multiple prospective randomised trials and a meta-analysis, support incorporation of the AED into PAD programmes.
Automated defibrillators in public places could one day become commonplace. In future, AEDs may even be found in homes and other places such as schools, just like fire extinguishers, since they could save a substantial number of lives. Where EMS response times are very prolonged, as in many communities, PAD programmes may hold promise for survival after OHCA.
Public access defibrillation: key points
Sudden cardiac arrest is one of the leading causes of death among adults in the western world. Each year, it claims the lives of an estimated 250 000 in the USA and 400 000 in Europe.
Once every 1–2 min a person succumbs suddenly, without warning, to sudden cardiac arrest. It can strike anyone, anywhere, any time. Chances of survival are strictly related to the presence of a defibrillator on site.
In cardiac intensive care units, when sudden cardiac arrest victims in ventricular fibrillation (VF) receive defibrillation therapy within the first minute or two after collapse, more than 90% survive. In more typical community settings, victims of sudden cardiac arrest rarely survive.
Most victims do not have immediate access to prompt, definitive treatment. Too much time elapses before the defibrillator arrives—if it arrives at all.
In New York City, the average emergency response time is relatively long, about 12 min; only 5% of witnessed VF victims—1–2% of all cardiac arrest victims—survive.
Seattle, on the other hand, has achieved an average response time of 7 min and a VF survival rate of 30%. In Rochester, Minnesota, response times average 6 min and 45% of VF victims survive.
The same results have been observed in Piacenza, Italy, a small city where an early defibrillation project was started 12 years ago.
A new development in early defibrillation is the widespread use of automated external defibrillators (AEDs), and the simplification of training and the extensive use of these devices in public places. Just like fire extinguishers have become commonplace, an AED should be placed everywhere a sudden cardiac arrest may occur.
The first step in defibrillation may no longer be left solely in the hands of the emergency medical services, due to their delay in arrival. The future of early defibrillation may lie with the witnesses of sudden cardiac arrest, provided a defibrillator is readily available.
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References
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- A milestone study demonstrating that the use of an AED is intuitive and even people without training may save lives using such a device.
- An important study demonstrating that CPR plus AED is better than CPR alone in resuscitating patients in ventricular fibrillation in public places.
- The use of an AED without any CPR instruction may increase survival rates compared to traditional emergency measures.
- In this study, the survival rate from ventricular fibrillation increased fourfold when an AED was used by lay responders in the community using a publicly placed AED.
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- ↵International guidelines that may help the implementation of public access defibrillation in the community.
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- ↵In this study children used an AED without any previous training, suggesting that widespread use of AEDs requires only modest training.
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Footnotes
Competing interests In compliance with EBAC/EACCME guidelines, all authors participating in Education in Heart have disclosed potential conflicts of interest that might cause a bias in the article. Alessandro Capucci has undertaken consultancy work for Sanofi-Aventis, Meda Pharma, Merck, and St Jude Medical.
Provenance and peer review Commissioned; internally peer reviewed.