An Automated External Defibrillator (AED) is a sophisticated, yet user-friendly, medical device designed to treat sudden cardiac arrest (SCA) by delivering an electrical shock to the heart. This shock interrupts chaotic, abnormal electrical rhythms, such as ventricular fibrillation, allowing the heart’s natural pacemaker to reset to a normal rhythm. Since the chance of survival decreases significantly every minute without defibrillation, immediate action with an AED is paramount. The device provides simple, clear instructions, enabling bystanders with minimal training to administer this life-saving intervention.
Ensuring Patient Readiness and Activating the Device
The absolute first step upon the AED’s arrival is to power the device on. This action is the most important initial step because it activates the AED’s internal guidance system, which uses voice prompts and visual cues to guide the rescuer through every subsequent stage. Turning it on immediately ensures the machine is ready for use, preventing time wasted before the pads are attached.
Once the AED is on and issuing prompts, the next priority is preparing the patient’s chest for proper electrical conduction. This involves quickly removing all clothing so the electrode pads can be placed directly onto the bare skin. The bare chest must also be dry and clear of excess moisture, such as sweat or water, which can interfere with the electrical shock’s effectiveness. If the patient has significant chest hair, it should be quickly shaved or wiped away using materials provided in the AED kit to ensure firm pad adhesion.
The transition from Cardiopulmonary Resuscitation (CPR), which may be ongoing, to using the AED should be seamless, with minimal interruption to chest compressions. The entire process of preparing the chest and applying the device should ideally take only seconds. The goal is to maximize the time the patient receives blood flow from compressions while preparing for definitive treatment.
Precise Placement of AED Pads
After the chest is bare and dry, the precise placement of the electrode pads is the next critical action, as it determines the path the electrical current will travel through the heart. For adults, the standard placement is the anterior-lateral position, which creates the most effective pathway for the current to cross the myocardium. One pad is placed on the patient’s upper right chest, just below the collarbone and to the right of the breastbone.
The second pad is positioned on the lower left side of the chest, slightly below the armpit and beneath the level of the pectoral muscle or breast tissue. This specific arrangement ensures that the electrical energy passes directly across the heart muscle. The pads often feature a graphic illustrating this placement to guide the user accurately.
Pediatric pads or a pediatric setting should be used for children under eight years old or weighing less than 55 pounds, as they deliver a reduced energy level. For smaller patients, an alternative anterior-posterior placement—one pad on the chest and the other on the back—is often used to prevent the pads from touching or overlapping. Regardless of the patient’s size, the pads must be pressed firmly onto the skin to achieve full adhesion, which minimizes transthoracic impedance and the risk of skin burns during the shock. The final action is connecting the electrode cable into the AED unit, allowing the device to begin monitoring the heart’s electrical activity.
Analyzing the Rhythm and Delivering the Shock
Once the pads are securely attached and plugged into the AED, the device automatically begins the rhythm analysis phase. The machine will issue a voice command, such as, “Analyzing Heart Rhythm. Do not touch the patient,” requiring everyone to stand clear immediately to avoid interfering with the electrical reading. An accurate analysis is essential for the AED to determine if the heart is in a shockable rhythm, specifically pulseless ventricular tachycardia or ventricular fibrillation.
The analysis concludes with one of two outcomes: “Shock Advised” or “No Shock Advised.” If the AED recommends a shock, the rescuer must loudly announce, “I’m clear, you’re clear, everybody’s clear” to confirm no one is in contact with the patient. For a semi-automatic AED, the rescuer presses the flashing shock button to deliver the controlled electrical impulse.
If the AED is a fully automatic model, it will count down and deliver the shock without the rescuer needing to press the button. Immediately following the shock, or if the AED advises “No Shock Advised,” the rescuer must restart high-quality Cardiopulmonary Resuscitation (CPR) without delay, beginning with two minutes of chest compressions. The AED is programmed to re-analyze the heart rhythm after this two-minute cycle, ensuring continuous evaluation and intervention until emergency medical services arrive.