Sudden out-of-hospital cardiac arrest (OOH-CA) results in the death of 400,000 to 460,000 Americans each year in the United States (1). Although the majority of these events occur in the home, up to 20% occur in public places (2). The majority of sudden, unexpected OOH-CA cases are caused by either ventricular fibrillation (VF) or ventricular tachycardia (VT) that degenerates rapidly to VF (3). Prompt defibrillation is a highly effective treatment if it can be delivered when the myocardium has not yet depleted its high-energy phosphate reserves. This early phase of cardiac arrest, which typically lasts only 3 to 4 minutes after cardiac arrest onset, is termed the “electrical phase” (4). Beyond this point, defibrillation may abolish the VF, but the heart is often unable to function adequately as a pump, resulting in either asystole or a pulseless electrical rhythm following defibrillation. This phase of resuscitation is termed the “circulatory phase” because a brief period of high-quality cardiopulmonary resuscitation (CPR) prior to attempting defibrillation may boost the heart’s high-energy phosphates sufficiently to result in effective cardiac pumping activity postdefibrillation. Rescuers may be able to restore spontaneous circulation (ROSC) when there has been a very long delay (e.g., >8 minutes from onset of VF) until initiation of resuscitation, but the patient may suffer severe neurological impairment. This phase of resuscitation is termed the “metabolic phase,” indicating that physical and/or pharmacological manipulation of cellular metabolism may be needed to mitigate long-term cellular impairment.

The purpose of this chapter is to review the current community approach to resuscitating OOH-CA patients using early defibrillation in the United States, with special focus on the use of automated external defibrillators (AEDs) by nonmedical personnel in public settings (i.e., “public access defibrillation” or “PAD”).

The best outcomes from cardiac arrest because of VF in adults occur regularly in the electrophysiology laboratory, where prompt defibrillation (within 20 to 30 seconds) results in >99% survival (5). The next best reported outcomes are in cardiac rehabilitation programs, where defibrillation occurs typically in 1 to 2 minutes, and survival is approximately 85% to 90% (5). At Chicago’s O’Hare and Midway airports, almost 70% of cardiac arrest patients whose initial rhythm is VF survive to hospital discharge (6). Survival from VF in Las Vegas casinos with victims treated by security officers equipped with AEDs varies from 75% when a shock is given in 3 minutes to 50% when a shock is given in 5 minutes (7). Outcomes in typical emergency medical service (EMS) systems that provide defibrillation in 8 to 8.5 minutes after patient collapse typically yield survival rates of about 16% (5). Thus, survival from cardiac arrest because of VF is highly dependent on the time interval from collapse to defibrillation. The chances for survival diminish by approximately 7% to 10% for every minute delay from the patient’s collapse to defibrillation (5).

The traditional community approach to optimizing survival from OOH-CA has been to train the public to recognize cardiac arrest, call 911, and perform CPR, while public safety personnel (fire or police first responders, emergency medical technicians (EMTs), and/or paramedics) rush to the scene to provide defibrillation and other advanced cardiac life support (ACLS) treatments. The American Heart Association (AHA) terms this sequence of events—early access, early CPR, early defibrillation, early ACLS—the “Chain of Survival” (5).

Early access to EMS is promoted by a 911 system currently available to more than 95% of the U.S. population. Enhanced 911 systems provide the caller’s location to the dispatcher, which permits rapid dispatch of prehospital personnel to locations, even if the caller is not capable of verbalizing or the dispatcher cannot understand the location of the emergency. Such centers typically have intense quality-assurance programs to ensure that emergency medical dispatchers follow protocols and procedures correctly and consistently. This is particularly true for the prearrival instructions that are given to cardiac arrest bystanders to instruct them on how to perform CPR while awaiting arrival of emergency personnel (phone CPR).

Even though CPR performed by layperson bystanders improves the odds of neurologically intact survival from OOH-CA, only about 25% of bystanders in most U.S. cities are willing
to perform CPR (a notable exception is Seattle, Washington, where 50% of layperson bystanders perform CPR) (8,9,10,11,12). Unwillingness of laypersons to perform mouth-to-mouth ventilation on strangers is a major part of the problem (13,14). Fortunately, increasing evidence suggests that chest compressions are much more important than artificial ventilation during the first 5 minutes after onset of OOH-CA in adults (12,15,16,17,18). Chest compressions alone cause changes in intrathoracic pressure that ventilate the victim adequately for the first 5 to 8 minutes after cardiac arrest. Chest compression-only CPR is being adopted for prearrival resuscitation instruction in many EMS systems.

To minimize time to treatment, most communities allow volunteer and/or paid firefighters and other first-aid providers to function as first responders, providing CPR and early defibrillation using AEDs until EMTs and paramedics arrive. Fire department personnel functioning as first responders are the backbone of the public safety primary response for most U.S. communities. Most of these personnel are trained either as first responders or basic EMTs.

Another approach has been to supplement the fire and EMS response with police officers who are trained and equipped to use AEDs. Such personnel can further enhance survival from out-of-hospital cardiac arrest compared to survival that can be achieved by conventional EMS services (7). White et al studied the outcome of all consecutive adult patients with nontraumatic cardiac arrest treated in Rochester, Minnesota, from November 1990 through July 1995. In that city, a centralized 911 center dispatched police and an ALS ambulance simultaneously for suspected cardiac arrest cases. The personnel who arrived first delivered the initial shock. Of 84 patients, 31 (37%) were shocked initially by police. Thirteen of the 31 demonstrated ROSC without need for ALS treatment. All 13 survived to discharge. The other 18 patients required ALS; 5 (27.7%) survived. Among the 53 patients first shocked by paramedics, 15 had ROSC after shocks only, and 14 survived. The other 38 needed ALS treatment; 9 survived. This study showed that a high discharge-to-home survival rate could be obtained when early defibrillation was provided by both police and paramedics. It is the rapidity of defibrillation that determines outcome, irrespective of who delivers the shock. When initial defibrillation attempts resulted in ROSC, the overwhelming majority of patients survived (96%). Even brief (e.g., 1 minute) decreases in the call-to-shock time interval increased the likelihood of ROSC from shocks only, with a consequent decrease in the need for further ALS intervention. Similar results have also been noted with the use of law enforcement early defibrillation in Miami-Dade County, Florida (19).

Most cities and larger suburban areas provide EMS ambulance services with providers from the fire department, a private ambulance company, and/or volunteers. The most common deployment pattern is a tiered system in which some of the ambulances are staffed and equipped at the basic EMT level (which includes first aid and early defibrillation with AEDs), and other units (either transporting or nontransporting) are staffed by paramedics or other intermediate-level EMTs (who can, in addition to basic care, start intravenous drips, intubate, and administer medications). In some systems, the advanced providers can also perform 12-lead ECGs, provide external pacing for symptomatic bradycardia, and perform other advanced techniques.

The concept of public access defibrillation emerged in 1990 from the AHA’s Future of CPR Task Force led by Dr. Leonard Cobb of Seattle, Washington. This group recognized that the majority of out-of-hospital cardiac arrests occur in the home. However, for those events occurring in a public place, they reasoned that the use of AEDs by laypersons could shave precious minutes off the time interval from collapse to defibrillation. Based on the Task Force’s report, the AHA established an AED Task Force, led by Dr. Myron Weisfeldt.

The 1992 AHA Guidelines on Cardiopulmonary Resuscitation and Emergency Cardiac Care was the first to include the following statement regarding the PAD concept: