Automated External Defibrillator (AED) pads are the interface between the device and a person experiencing sudden cardiac arrest. These self-adhesive pads serve as electrode patches that allow the AED to analyze the patient’s heart rhythm. Their primary purpose is to determine if a shockable rhythm is present and, if necessary, to deliver a controlled electrical impulse across the chest to restore a normal heartbeat. The pads are single-use and disposable.
The Dual Role of AED Pads
The pads function with two distinct roles. First, they act as sophisticated sensors, monitoring the electrical activity of the heart to perform an electrocardiogram (ECG) analysis. The AED uses this information to detect a life-threatening, irregular rhythm like ventricular fibrillation.
Second, if a shockable rhythm is identified, the pads become the conduit for the therapeutic electrical energy. A layer of conductive, adhesive gel covers the underside of each pad, engineered to minimize electrical resistance (transthoracic impedance) between the pad and the skin. This low-resistance path ensures the maximum amount of energy reaches the heart muscle, preventing the current from arcing or causing surface burns.
Selecting the Correct Pad Size
Choosing the appropriate pad type is a matter of electrical safety, as it determines the energy level delivered. Adult pads are designed for individuals aged eight or older, or those weighing more than 55 pounds (25 kilograms), and deliver a full-energy shock, typically between 150 and 200 Joules. Using these pads on a child risks delivering an unsafe and potentially damaging level of energy.
Pediatric pads are designed for children under eight years old or under 55 pounds. These pads incorporate an attenuation circuit, a built-in resistor that reduces the energy output to a safer, lower dose, often around 50 Joules or less. This attenuated energy is appropriate for a child’s smaller body mass and cardiac tissue.
Using a pediatric pad on an adult is dangerous because the reduced energy will be insufficient to stop a chaotic adult heart rhythm. The difference in energy dosage, achieved through the attenuation circuit, requires responders to quickly identify and apply the correct pad type based on the patient’s size. Incorrect pad selection renders the defibrillation attempt ineffective or causes harm.
Proper Placement for Effective Use
Correct placement of the pads ensures the electrical current passes directly through the heart muscle. The standard position for adults and larger children is the anterior-lateral placement. One pad is placed on the upper right side of the chest, just below the collarbone, and the other is positioned on the lower left side of the rib cage, near the armpit.
For small children and infants, placement shifts to an anterior-posterior configuration. One pad is centered on the front of the chest, and the second pad is placed on the back, between the shoulder blades. This front-to-back positioning ensures the pads do not touch on the small torso and creates an effective pathway for the current to cross the heart.
Before application, the chest must be prepared to maximize contact and conductivity. Excessive chest hair should be quickly shaved, and the skin must be completely dry to prevent the current from arcing. Additionally, any medication patches on the chest must be removed and the area wiped clean before placing the pads.
Ensuring Pad Readiness and Lifespan
AED pads have a limited lifespan due to the delicate nature of their conductive materials. The primary reason for expiration, which typically ranges from 18 to 30 months, is the gradual drying out of the conductive adhesive gel. Once the gel dries, the pads lose their ability to properly adhere to the skin and effectively conduct the electrical shock.
Using an expired pad results in poor contact, which reduces the efficacy of the shock and can lead to a failed rescue attempt. Every pad package has a clearly marked expiration date that must be checked regularly during routine AED maintenance. The pads must remain sealed in their original foil pouch until use to maintain the integrity of the gel.