An Automated External Defibrillator (AED) is a portable device designed to treat sudden cardiac arrest (SCA), a condition where the heart’s electrical activity becomes chaotic and ineffective. The chance of survival decreases significantly with every minute that passes without intervention. The AED plays a direct role in the Chain of Survival by delivering a controlled electrical shock, known as defibrillation, which can reset the heart’s rhythm. Knowing the correct sequence of actions upon the device’s arrival is crucial for a successful outcome.
Powering On and Initiating the Sequence
The most immediate action a rescuer must take once the AED arrives is to turn the machine on. This step initiates the entire life-saving sequence. On many modern devices, opening the lid or carrying case automatically powers the unit on, while others have a clearly marked power button.
Activating the AED without delay allows the device to begin its internal self-checks and start providing clear, step-by-step voice prompts. These audio instructions guide the rescuer, minimizing confusion and downtime, even if Cardiopulmonary Resuscitation (CPR) is currently in progress. Following the device’s verbal commands ensures the process moves quickly and efficiently toward analyzing the heart’s rhythm.
Preparing the Chest and Attaching the Pads
Once the AED is powered on, the focus shifts to preparing the person’s chest for the electrode pads. The pads must make direct, firm contact with the skin, requiring the removal of all clothing covering the chest, often using trauma shears found in the AED kit. The chest area must also be dry, as water or excessive moisture can conduct electricity away from the heart and interfere with analysis or shock delivery.
If the person has excessive chest hair, the pads may not adhere properly, resulting in a poor connection or a “check pads” error message. A disposable razor, typically included in the AED kit, should be used to quickly shave the areas where the pads will be placed. Medication patches on the chest must also be removed and the skin wiped clean before pad application, as they can block electrical conduction or cause skin burns.
Pad Placement
For an adult, the standard placement involves affixing one electrode pad to the upper right side of the chest, just below the collarbone. The second pad is placed on the lower left side of the rib cage, a few inches below the armpit. This diagonal positioning is designed to bracket the heart, ensuring the electrical current travels through the cardiac muscle. After securing the pads firmly to the bare skin, plug the pad cable connector into the AED unit to allow the machine to begin monitoring.
Analyzing the Rhythm and Delivering the Intervention
With the pads connected, the AED automatically transitions into the analysis phase to determine if the heart rhythm is “shockable.” During this time, the rescuer must ensure no one touches the person, as movement interferes with the rhythm analysis. The rescuer should loudly announce “Clear” or “Hands-off the patient” to confirm this safety measure before the assessment proceeds.
The AED will announce one of two possible outcomes: “Shock Advised” or “No Shock Advised.” If a shock is advised, the device charges itself, and the rescuer must confirm the “Clear” warning once more before pressing the flashing shock button on a semi-automatic model. The electrical discharge is a brief, high-energy pulse intended to interrupt the chaotic electrical activity, potentially allowing the heart’s natural pacemaker to regain control.
If the AED announces “No Shock Advised,” or immediately after a shock has been delivered, the rescuer must instantly resume high-quality CPR. Chest compressions are necessary to circulate oxygenated blood until the heart can sustain an effective rhythm on its own. The rescuer should continue CPR for approximately two minutes, or until the AED prompts them to stop for another rhythm analysis, following the device’s guidance until emergency medical services arrive.