An automated external defibrillator (AED) is a specialized medical device designed to examine the heart's rhythm and administer an electrical shock to individuals experiencing ventricular fibrillation in order to restore the heart rhythm back to normal. Ventricular fibrillation is a condition that disrupts the heart's natural rhythm and is a common cause of sudden cardiac arrest. When ventricular fibrillation occurs or when the heart ceases to beat altogether, sudden cardiac arrest occurs. Without prompt medical intervention, the individual typically collapses, loses consciousness, becomes unresponsive, and dies. Often, victims have no prior history of heart issues and are stricken without warning. The likelihood of surviving sudden cardiac arrest decreases by 7 to 10 percent each minute without immediate CPR or defibrillation. Beyond 10 minutes, attempts at resuscitation are rarely successful.
Indication
AEDs are used to revive individuals facing sudden cardiac arrest, often triggered by disruptions in the heart's electrical activity, leading to either dangerously rapid heartbeat (ventricular tachycardia) or irregular, accelerated heartbeat (ventricular fibrillation). These erratic heart rhythms hinder effective pumping and can eventually stop the heart altogether.
Such instances deprive the brain and other crucial organs of necessary oxygen and blood, necessitating swift intervention within minutes to avert fatality. The speedier the restoration of the heart's rhythm, the higher the likelihood of preventing permanent damage to vital organs, including the brain.
When an individual experiences ventricular fibrillation or ventricular tachycardia and an AED is in proximity, a bystander in a public space or a family member can utilize it to shock the heart back into a regular rhythm. Employing an AED in these critical moments holds the potential to save a life.
While cardiopulmonary resuscitation (CPR) can temporarily maintain blood flow to the heart and brain post-cardiac arrest, often, only defibrillation can reinstate the heart's rhythm. The combined use of these treatments significantly enhances the prospects of survival.
AEDs are not designed to shock asystole (flatline) as this will not have a positive clinical outcome. To give an asystolic patient a chance to survive, a combination of CPR and cardiac stimulant drugs is required to establish one of the shockable rhythms, which is why it is imperative for CPR to be carried out before the arrival of the device.
Placement and availability
There devices are commonly available in various public places, such as shopping malls, office complexes, sports stadiums, fitness centers, and even airplanes. Law enforcement officers and emergency medical teams are also equipped with AEDs. Nevertheless, a considerable number of cardiac arrests take place within homes. Thus, owning an AED for home use can significantly reduce the time needed to revive an individual experiencing ventricular fibrillation or ventricular tachycardia.
Advocates of home AEDs emphasize that placing them where they're most needed can save many lives. Conversely, critics contest this perspective, citing a lack of dependable evidence supporting the notion that home defibrillators effectively increase survival rates.
Public access AEDs are often designed to be highly visible, sporting vibrant colors and housed in protective cases positioned near building entrances. Opening these cases or removing the defibrillator can trigger a buzzer alerting nearby staff, though this alert doesn't automatically summon emergency services. Trained AED operators are aware of the necessity to call for an ambulance while using or requesting an AED. In September 2008, the International Liaison Committee on Resuscitation introduced a 'universal AED sign' for global adoption, denoting the presence of an AED.
A rising trend involves individuals purchasing AEDs for home use, particularly those with pre-existing heart conditions. As prices have become more affordable, the number of these devices in communities has surged. However, medical professionals have voiced concerns about the lack of proper training among home users. Many advocate for broader reliance on community responders who undergo suitable training and oversight.
An AED kit typically includes a face shield to create a barrier between the rescuer and patient during rescue breathing, a pair of nitrile rubber gloves, trauma shears for cutting through clothing to expose the chest, a small towel for chest moisture, and a razor for shaving excessively hairy chests.
Precautions
Automated external defibrillator, like all defibrillators, is a device that can send an electrical shock through the body making it a shock hazard. There are precautions that must be followed to not only maximize the likelihood of saving someone’s life, but to make sure that no one is harmed by use of an AED.
- Water: Water is a conductor of electricity, an automated external defibrillator shouldn't be use in a wet environment or where water is present. Before applying the electrical pads, the moisture on the victim's chest should be thoroughly dried, as any shock would travel through the water and not the heart. Oftentimes, automated external defibrillators include a towel to dry the skin.
- Metal: Depending on the metal, some are great conductors of electricity. It is strongly recommended that the metal underwire in a bra or metal piercings be removed to prevent conduction of the electrical shock which can lead to arcing or a fire.
- No Touching: The human body also conducts electricity. No one should touch the body when the automated external defibrillator is about to deliver a shock. Direct others to stand clear of the victim before applying electrical shocks.
- Flammable Environments: Never use an AED in a room where there is a buildup of combustible vapors. Sparks generated may ignite them and pose a risk of explosion and fire.
- Medication Patches: These patches may be a burn hazard or interfere with the shock being delivered to the heart. They should be remove using gloves prior to placing AED pads. Some models include gloves.
- Hairy Chest: Excessive chest hair may interfere with the adhesion of the pads and can diminish or block the flow of electricity, preventing the defibrillator from delivering the shock to the heart. Some defibrillators include a razor for use on especially hirsute chests.
- Pacemakers and Implanted Defibrillators: For victims with pacemakers or implanted defibrillators, the AED pads should be stick at least one inch away from these devices. Implanted devices are usually located on the upper left side of the chest, near the heart. Such a device may not be working properly, so the presence of one should not be a reason to prevent the use of the AED to save someone’s life.
- Following the Prompts: Most automated external defibrillators offer prompts or automatically check to see if defibrillation is necessary. Prompts should be followed to make sure the AED is used for the purpose it was intended.
Procedure
AED is administered during CPR, visit CPR Procedure for more info.
1. Check the scene and make sure it is safe. Among the dangers include a wet environment, a flammable environment, and metallic surfaces or items where electricity can arc. (See Precautions above)
2. Ensure that the person needs help, ask a bystander to look for an AED, and call 911 for help. Apply CPR.
3. As soon as an AED is available, open the case, and turn on the device. Note: Because AED models function differently, follow the manufacturer's instruction for that AED.
4. Open the victim's shirt or cut it open using the scissors included with the AED.
5. Wipe the chest dry if wet with an included towel. Remove any medication patches using the gloves that come with the defibrillator. Remove metallic objects from the victim as well.
6. Attach pads correctly.
For infants up to 1 year old, use pediatric pads if available. If pediatric pads aren't available—or the AED doesn't have a pediatric setting—it's safe to use adult AED pads or adult levels of energy. Always use an anterior/posterior pad placement. To do this, apply one pad to the center of the infant's chest—on the sternum—and one pad to the infant's back between the scapulae.
For children 8 or younger or weighing 55 pounds (25kg) or less, use pediatric pads and pediatric setting if available. If not, use adult AED pads or adult levels of energy. Use an anterior/lateral placement, according to the manufacturer instructions. Place one pad to the right of the sternum and below the right clavicle. Place the other on the left side of the chest on the mid-axillary line, a few inches below the left armpit. Alternatively, use an anterior/posterior pad placement if the AED pads risk touching each other on the child's chest or the manufacturer recommends.
For children older than 8 years or weighing more than 55 pounds (25kg) and adults, use adult AED pads. Use an anterior/lateral or anterior/posterior placement, according to manufacturer instructions.
Note: Never use pediatric AED pads or a pediatric electrical setting on a child older than 8 years or weighing more than 55 pounds (25kg). That's because the shock delivered will not be sufficient.
Some AEDs comes with pediatric AED pads. These are smaller and designed specifically to deliver a lower level of energy. Also, some AEDs use a switch or key on the device itself instead of changing pads.
7. Ensure that the wires are attached to the AED box.
8. Push the analyze button on the automated external defibrillator (some AEDs may do this automatically) and let it analyze the heart's rhythm. Instruct everyone to stand clear by loudly saying "CLEAR" while the AED analyzes. No one, including you, should be touching the victim.
As the AED analyzes, switch positions if you are working with a team. The provider giving compressions should hover their hands above the victim's chest.
9. If directed to deliver a shock, instruct everyone to stand clear (by loudly saying "CLEAR"). The compressor continues to hover their hands over the victim's chest in preparation for CPR. Once everyone is clear, push the button to deliver the shock.
Note: if the AED message reads "Check Electrodes", ensure that the electrodes make good contact. If the AED message reads "Shock", then press and hold the flashing shock button until the shock is delivered. This may vary depending on the AED that is use. Some AED give voice prompts, make sure to follow the instructions.
10. After the AED delivers the shock, or if no shock is needed, immediately begin CPR. There is no need to wait for the AED prompt. Continue for about 2 minutes until the AED prompts that it is reanalyzing, or if the victim shows signs of return of spontaneous circulation, or the team leader or other trained providers instruct you to stop.
If you are working with a team, rotate roles during the analysis to prevent fatigue as needed.
11. Repeat the steps as necessary.
Liability
Automated external defibrillators have become so simple that most states across the United States now include the "good faith" use of an AED within their Good Samaritan laws. This "good faith" protection implies that a volunteer responder (acting outside of their professional capacity) cannot be held civilly responsible for any harm or fatality caused to a victim due to providing inadequate or improper care, as long as the harm wasn't intentional and the responder acted within their training and in good faith. Good Samaritan laws in the U.S. extend some level of protection for both trained and untrained responders using automated external defibrillators. Proper use of automated external defibrillators carries minimal liability if done correctly; many CPR courses, NREMT-B, and various state Emergency Medical Technician (EMT) training programs now integrate or provide education on AED usage as part of their curriculum.
Videos
CPR with AED use
AED Video (British Red Cross)