These tasks include the following:
- Recognition of cardiac arrest;
- Call for assistance, likely by dialing 911;
- Performing some form of cardiopulmonary resuscitation (CPR); and
- Summoning and applying an Automated External Defibrillator (AED) to the victim’s bare chest.
These interventions, and several others, can be termed “pre-arrival care.” Multiple scientific studies have demonstrated the very positive impact of these pre-arrival interventions on outcome of cardiac arrest, long before arrival of EMS personnel. In addition to calling for assistance, the two “medical” interventions performed by lay rescuer include CPR and AED application. To provide the most optimal opportunity for meaningful survival from OHCA, both interventions should be performed as soon as possible. In this instance, seconds quite literally can make the difference between life and death.
Automated external defibrillators (AEDs) are portable devices that automatically analyze the cardiac rhythms of patients with cardiac arrest and deliver electrical (“defibrillatory”) shocks if either ventricular fibrillation or ventricular tachycardia are detected; these rhythms are referred to as “shockable rhythms.” Among persons with OHCA, shockable initial rhythms are noted in up to a third of patients with out-of-hospital cardiac arrest. The other common rhythm scenarios encountered in cardiac arrest are asystole and pulseless electrical activity. These rhythms do not require an electrical shock from an AED. Thus, the majority of victims of OHCA do not have shockable rhythms; the AED will not deliver a defibrillatory shock and will instruct the lay rescuer to perform CPR.
The potential lifesaving advantages of AEDs in public locations have been investigated extensively. In a large number of scientific studies considering the use of the automatic external defibrillator, survival increased by approximately 25% in those persons who are managed by a lay rescuer with an AED, compared with those victims shocked by emergency medical services personnel after their arrival at the scene. Unfortunately, AEDs are less often used by lay rescuers; in fact, studies demonstrate that bystanders applied an AED in only approximately 15% of victims.
AEDs are especially useful when placed in public places where there is a reasonable probability of a witnessed cardiac arrest. The American Heart Association recommends that AEDs are best placed in locations such as airports, rail terminals, casinos, sports arenas, and buildings in which larger number of persons at risk for cardiac arrest frequent. In addition, they recommend AED placement in locations in which there is at least one cardiac arrest event every five years. These AEDs are termed public-access AEDs in that they are placed in an area accessible to the public during some or all of the 24 hour-day. AED placement in commercial aircraft is also required by many nations, including the United States.
AEDs are safe and relatively easy to operate, even by untrained lay rescuers. Operation of the AED by lay rescuers is guided by audible prompts from the AED itself as well as graphical directions on the device. Although AED design differs somewhat by manufacturer, the basic elements of operation are the same. The basic approach to AED application and use in a victim of cardiac arrest includes the following:
The user is instructed to turn the device on and to bare the patient’s chest.
The defibrillator pads must be opened and their protective backing removed; they are then positioned on the patient’s chest according to the graphics shown on the AED.
The AED then analyzes the patient’s cardiac rhythm, and if a shockable rhythm is detected, the user is instructed to press a button that delivers the defibrillatory shock.
Although AEDs offer many benefits, there are challenges to their use by lay providers. As noted above, AEDs are less often used by lay rescuers, being applied in only 15% of victims. Studies suggest that even in regions in which active efforts have been made to position public-access AEDs widely, less than 10% of out-of-hospital cardiac arrests occur within 100 m of an AED. Furthermore, many AEDs that are installed in the community are located inside buildings such as schools, business offices, and sports facilities that are not accessible to the public during certain periods of the day. In addition, when the ability of untrained laypersons to operate AEDs was evaluated, substantial variation in ability was observed. Lastly and importantly, lay rescuers must perform appropriate CPR while operating the AED. Although AED use is potentially lifesaving, operating an AED may cause the bystander to be distracted from performing CPR.
Note: This section is based on an article in the New England Journal of Medicine by William J. Brady, MD, Amal Mattu, MD, and Corey M. Slovis, MD. For more information, see Lay Responder Care for the Adult Victim of Out-of-Hospital Cardiac Arrest. New Engl J Med 2019;381:2242-51; DOI: 10.1056/NEJMra1802529) and attachment. Figure 3 in the article was provided by Sudden Cardiac Arrest Foundation.
Author: William J. Brady, MD