Defibrillation uses a controlled electrical shock to interrupt an abnormal, life-threatening heart rhythm, allowing the heart’s natural pacemaker to reset. The success of this time-sensitive procedure depends on the electrical current passing effectively through the heart muscle. Correct placement of the defibrillator pads, which serve as the entry and exit points for the current, is critical for restoring a normal rhythm. Understanding the precise locations and preparatory steps ensures maximum electrical energy reaches the target tissue safely.
Preparing the Patient for Pad Application
Before placing the self-adhesive defibrillator pads, the chest must be prepared to minimize resistance to the electrical current, known as transthoracic impedance. The area where the pads will be placed must be fully exposed, requiring the removal of all clothing and undergarments. Moisture, such as perspiration or water, significantly increases the risk of electrical arcing or burns, so the skin must be wiped completely dry before application.
Metal jewelry or objects near the intended pad sites must be removed, as metal can conduct electricity and divert the current away from the heart. Transdermal medication patches, such as those containing nitroglycerin, must also be removed and the skin wiped clean. These patches can block the current path and potentially cause skin burns. If significant chest hair prevents the pads from sticking firmly, the hair should be quickly shaved or removed to guarantee full skin contact.
Standard Adult Pad Placement
The most common method for placing defibrillator pads on an adult is the Anterior-Lateral configuration, positioning the pads on the front and side of the chest. This placement creates a direct electrical path spanning the heart muscle. One pad, often called the Sternal or Clavicular pad, is placed on the upper right side of the chest, just below the collarbone and next to the breastbone.
The second pad, known as the Apical or Apex pad, is situated on the lower left side of the chest, typically in the mid-axillary line (in line with the armpit). This pad should be placed below the left nipple or below the fold of the left breast for optimal contact. The goal is for the heart to lie directly between the two electrodes, maximizing the electrical current density. Proper placement avoids bony structures and ensures effective energy delivery.
Special Considerations for Pad Placement
Situations involving specific patient conditions or smaller body sizes require adjustments to the standard pad location to ensure safety and effectiveness.
Pediatric Patients
For pediatric patients (generally under 8 years old or weighing less than 55 pounds), specialized pediatric pads or attenuated energy settings must be used to reduce the shock dose. The recommended placement is often the Anterior-Posterior method. One pad is placed on the center of the chest and the other is placed on the back between the shoulder blades. This front-and-back positioning prevents the pads from touching on a small chest while directing the current across the heart.
Implanted Devices
If an implanted medical device, such as a pacemaker or ICD, is visible or palpable, the pads must be placed at least one inch (2.5 cm) away from the device site. Placing a pad directly over an implant can damage the device or divert the electrical energy.
Large Breasts
For patients with large breasts, the Apical pad must be placed laterally or lifted and positioned underneath the breast tissue. Ensure the pad’s entire surface adheres to the skin without folding. The Anterior-Posterior arrangement can also be used as an alternative when standard Anterior-Lateral positioning is not feasible due to physical obstructions.
Post-Placement Safety and Operation
Once the pads are correctly and firmly adhered to the bare skin, they must be connected immediately to the AED or manual defibrillator unit. The device will then analyze the patient’s heart rhythm using the electrical signals received through the pads. During this analysis phase, no one should touch the patient, as movement or contact interferes with the device’s ability to accurately read the heart activity.
The device provides clear voice prompts, instructing the rescuer whether a shock is advised. If a shock is indicated, the rescuer must loudly announce “Clear!” to ensure all personnel remove contact before the shock button is pressed. Immediately after the shock is delivered, or if no shock is needed, chest compressions should be restarted without delay.