The Automated External Defibrillator (AED) is a medical device used during Sudden Cardiac Arrest (SCA). SCA occurs when the heart’s electrical activity becomes chaotic, preventing effective blood pumping. The AED delivers a controlled electrical shock to the chest to temporarily halt this disorganized rhythm, allowing the heart’s natural pacemaker to potentially reset to a normal beat. Effective use requires both speed of application and precise placement of the electrode pads.
Standard Placement for Adults and Older Children
The most common and recommended configuration for individuals over approximately eight years of age or weighing more than 55 pounds is the anterior-lateral placement. This positioning ensures the electrical current passes directly through the heart muscle to maximize the chance of successful defibrillation. Proper contact is achieved by placing the adhesive pads directly onto the bare, dry skin of the chest.
The first pad should be positioned on the upper right side of the chest, specifically below the collarbone and to the right of the breastbone. The second pad is then placed on the lower left side of the rib cage, below the armpit. This configuration directs the shock across the heart’s mass from the top right to the lower left.
The pads must not touch each other, as this can cause the electrical current to short-circuit, bypassing the heart and rendering the shock ineffective. The pads must adhere entirely to the skin for the AED to accurately analyze the heart rhythm and deliver the appropriate electrical energy. Following the visual guides printed on the pads themselves can help confirm correct placement.
Special Placement for Infants and Small Children
For patients who are small children, typically defined as under eight years old or weighing less than 55 pounds, a different pad configuration is necessary. Pediatric pads must be used on the AED, as they deliver a lower, attenuated dose of electrical energy appropriate for a smaller body. The reduced energy level helps prevent damage to the developing heart muscle.
The physical size of a small child’s chest often makes the standard adult placement impossible without the pads touching, requiring the use of the anterior-posterior configuration. This involves placing one pad on the center of the chest, over the breastbone (the anterior position). The second pad is then placed on the center of the back, between the shoulder blades (the posterior position).
This placement ensures the pads are sufficiently separated so the electrical current travels directly through the heart from front to back. If pediatric-specific pads are unavailable, standard adult pads can be used in this same anterior-posterior configuration. This alternative is only acceptable if the pads can be placed without overlapping or touching, as delivering an unattenuated shock is preferable to delivering no shock at all.
Preparation and Safety Considerations
Before applying the AED pads, check the patient for potential obstructions. If the patient is lying on a wet surface or their chest is covered in water or excessive sweat, they must be moved to a dry area, and the chest must be wiped completely dry. Water conducts electricity, which can divert the shock away from the heart or potentially harm bystanders.
Any transdermal medication patches must be removed from where the pads will be placed. Delivering a shock directly over these patches can block the electrical current from reaching the heart and may cause a skin burn due to the patch’s metallic backing or medication residue. It is advisable to wipe the area clean after removing the patch and to wear gloves to prevent medication absorption.
The presence of implanted medical devices, like pacemakers or implantable cardioverter-defibrillators, requires a slight modification in pad placement. These devices often create a visible lump or bulge under the skin, usually on the upper chest. The AED pads must be placed at least one inch away from this visible device to avoid damaging the implant or blocking the delivery of the electrical current.
If the patient has excessive chest hair, it can prevent the electrode pads from making full contact with the skin. If the pads fail to adhere, the area where the pad is to be placed should be shaved using the razor often included in the AED kit. If a razor is not available, a set of pads can be pressed down and then ripped off to remove some of the hair, with a second set of pads then applied for the shock.