Defibrillation is a life-saving intervention that delivers a controlled electrical shock to the heart muscle to halt chaotic electrical activity and allow a normal rhythm to resume. This procedure, often performed using an Automated External Defibrillator (AED), is reserved for specific, life-threatening heart rhythms like ventricular fibrillation and pulseless ventricular tachycardia. For the electrical current to effectively “reset” the heart, the adhesive pads must be applied correctly to create an unobstructed pathway through the heart muscle. Improper placement reduces the shock’s effectiveness and lowers the chance of survival during sudden cardiac arrest.
Essential Preparation Before Pad Application
The success of a defibrillation shock depends on proper preparation of the patient’s chest. Before placing the adhesive pads, the skin must be bare, clean, and dry to ensure efficient electrical current transfer. Any moisture, such as sweat, increases resistance (transthoracic impedance), which diminishes the shock’s power and can cause skin burns.
Removing clothing is mandatory. If the patient has excessive chest hair, it should be quickly shaved or torn away to ensure full pad-to-skin contact. Poor adhesion due to hair or moisture leads to a less effective shock delivery and increases the risk of arcing or skin burns.
Any metallic objects, such as necklaces or body piercings, near the pad placement area should be removed or moved aside, as metal conducts electricity and can divert the current. Transdermal medication patches must be removed with a gloved hand, and the skin wiped clean. Placing a pad over a patch blocks energy transfer and may cause a skin burn or reduce the medication’s effect.
Implanted Devices
For patients with an implanted pacemaker or cardioverter-defibrillator (ICD), the defibrillator pad must be placed at least one inch (2.5 to 3 centimeters) away from the device site. This distance prevents potential damage to the implant.
Standard Defibrillator Pad Placement for Adults
The standard and most common method for adult defibrillator pad placement is the anterior-lateral position, which creates the most direct electrical path through the heart. This involves placing one pad on the upper right side of the chest and the second pad on the lower left side, ensuring the heart is situated between the two electrodes.
The first pad should be placed on the patient’s upper right chest, just below the collarbone (clavicle) and to the right of the breastbone (sternum). This placement avoids placing the pad directly over bone.
The second pad is positioned on the lower left side of the chest, typically below the left nipple or breast, along the mid-axillary line. This line runs vertically down the side of the chest from the center of the armpit, and the pad should be placed over the lower rib cage.
If the patient has large breast tissue, the lower pad must be placed to the side of or underneath the breast to ensure full contact with the chest wall. This anterior-lateral arrangement directs the electrical current across the heart muscle, which is required to interrupt the chaotic rhythm.
Placement Variations for Children and Special Cases
For children under eight years of age or those weighing less than 55 pounds (25 kilograms), the standard adult placement is generally modified to prevent the pads from touching or overlapping on their smaller chest area. The recommended pediatric placement is the anterior-posterior (A/P) configuration, where one pad is placed on the front of the chest, and the other is placed on the back. This method ensures the pads are separated while still allowing the electrical current to pass through the heart.
In the A/P method, the first pad is placed in the center of the child’s chest, and the second pad is placed on the child’s back, positioned between the shoulder blades. Pediatric pads should be used if available, as they deliver an attenuated, or reduced, energy dose appropriate for a child’s smaller body. If only adult pads are available, they should still be used, maintaining the A/P placement to prevent contact between the pads and maximize the distance the current travels.
The anterior-posterior configuration is also an alternative for adults in special cases, such as when the patient is small-statured, or if the standard anterior-lateral placement cannot be safely achieved without pad overlap. For pregnant patients experiencing cardiac arrest, the standard anterior-lateral adult placement is used without modification, as defibrillation is considered safe and necessary to save both the mother and the fetus. The overarching principle in all variations is to ensure a clear electrical path through the heart while maintaining full contact between the pads and the bare skin.