An Automated External Defibrillator (AED) is a portable medical device designed to treat sudden cardiac arrest (SCA), a condition where the heart’s electrical system malfunctions, causing an irregular rhythm. This malfunction, often ventricular fibrillation, prevents the heart from effectively pumping blood, leading to collapse and loss of consciousness. The AED works by analyzing the heart’s electrical activity and delivering a controlled electrical shock, known as defibrillation, to reset the rhythm. Since the probability of survival decreases by approximately 7 to 10% for every minute defibrillation is delayed, the quick and accurate placement of the pads is directly linked to a successful outcome.
Initial Setup and Preparation
Before attempting to place the pads, the immediate scene and the victim require preparation to ensure the defibrillation is effective and safe. The first step involves confirming that the victim is unresponsive and not breathing normally, which signals the need for emergency intervention. Simultaneously, someone must be directed to call emergency medical services and retrieve the AED, which should be turned on immediately upon arrival. The device will begin issuing voice prompts that guide the user.
The victim’s chest must be completely exposed to allow the pads to adhere firmly to the skin. Clothing should be removed or cut away quickly to achieve this bare-skin contact. If the victim is heavily saturated with sweat, the area where the pads will be placed must be quickly wiped dry. Moisture can conduct the electrical current away from the heart, which would reduce the shock’s effectiveness.
Standard Pad Placement for Adults
For victims aged eight or older, or those weighing more than 55 pounds, the standard technique for pad placement is the anterior-lateral method. This positioning ensures the electrical current passes directly through the heart muscle to maximize the chance of restoring a normal rhythm. The pads themselves often feature diagrams illustrating the correct anatomical placement.
The first electrode pad should be applied to the upper right side of the chest, situated just below the collarbone and to the side of the breastbone. The second pad is placed on the lower left side of the chest, positioned a few inches below the armpit along the bottom edge of the rib cage. Once the pads are positioned, they must be pressed down with firm pressure to eliminate any air pockets and guarantee complete contact with the skin.
Addressing Placement Challenges
Certain victim characteristics require modifications to the standard preparation or pad placement to maintain defibrillation efficacy.
Pediatric Patients
For a child under eight years old or weighing less than 55 pounds, specialized pediatric pads should be used if available, as they deliver a reduced energy dose. These smaller pads are typically placed in an anterior-posterior configuration, with one pad on the center of the chest and the other on the back, between the shoulder blades. This front-and-back positioning prevents the pads from touching, which is a concern on a small torso.
Hairy Chests
A victim with a significantly hairy chest presents a challenge because hair can prevent the pads from adhering securely to the skin, which may diminish the energy delivered to the heart. If the AED kit contains a razor, the hair should be quickly shaved from the intended placement sites before pad application. If no razor is available, apply the first set of pads firmly and then swiftly rip them off, using them like a wax strip to remove enough hair for the second set of pads to stick properly.
Medical Devices and Patches
The presence of implanted medical devices or transdermal medication patches necessitates altered placement. Pacemakers or implanted cardioverter-defibrillators are often visible as a small lump beneath the skin, typically in the upper chest. Pads must be placed at least one inch away from these devices to prevent damage to the implant or interference with the shock delivery. Medication patches, such as those containing nitroglycerin, must be removed and the skin wiped clean prior to pad placement to avoid the risk of thermal burns.
Completing the Defibrillation Process
Once the electrode pads are securely attached and connected to the AED, the device automatically begins analyzing the victim’s heart rhythm. During this analysis phase, it is important that no one touches the victim, as contact can interfere with the machine’s ability to detect a shockable rhythm. The AED will then communicate its finding through a voice prompt, advising a shock or indicating that no shock is necessary.
If a shock is advised, the rescuer must loudly command “Clear!” to ensure all bystanders move away from the victim and connected equipment. The rescuer then presses the flashing shock button to deliver the electrical energy. Immediately following the shock, or if the device advises against a shock, the rescuer must promptly resume Cardiopulmonary Resuscitation (CPR), beginning with chest compressions. The AED will continue to provide prompts, guiding the rescuer to perform two minutes of CPR before it pauses to re-analyze the heart rhythm. This cycle of CPR and AED analysis should continue until emergency medical services personnel arrive to take over care.