CPR and the Automated External Defibrillator (AED) are the two most important immediate interventions for sudden cardiac arrest. Cardiac arrest occurs when the heart’s electrical system malfunctions, stopping the effective pumping of blood. CPR mechanically circulates blood and oxygen, but the AED is the only device that can deliver the electrical shock needed to reset the heart’s rhythm. Using both techniques in a coordinated and timely manner significantly increases the chances of survival.
CPR Before AED Arrival
When a person is unresponsive and not breathing normally, immediately activate the emergency medical system by calling 911. If two rescuers are present, one should call for help and locate an AED, while the other immediately begins chest compressions. This simultaneous action ensures professional help is on the way and life-sustaining blood flow starts without delay.
High-quality chest compressions are the foundation of initial CPR and must be started immediately on a firm, flat surface. For an adult, compressions should be delivered at 100 to 120 beats per minute, pushing down at least two inches (five centimeters) on the center of the chest. Allow the chest to fully recoil after each compression to ensure the heart refills with blood. If trained, perform two rescue breaths after every 30 compressions, maintaining this cycle until the AED arrives or emergency services take over.
Integrating the AED and Pad Placement
The AED should be incorporated the instant it is brought to the patient’s side. Turn the device on immediately, as it provides voice and visual prompts that guide the rescuer. While one rescuer continues chest compressions, the other should prepare the patient’s chest by removing clothing and quickly drying the skin if it is wet. Minimize interruptions to compressions during this preparation.
Once the chest is exposed, firmly attach the electrode pads to the bare skin in the standard adult position. This placement ensures the electrical current passes directly through the heart. Place one pad on the upper right side of the chest, just below the collarbone, and the other on the lower left side of the rib cage, slightly below the armpit. Strong adhesion is necessary for the AED to properly analyze the heart’s electrical activity and deliver an effective charge.
AED Analysis, Shock, and Cycle Continuation
After the pads are connected, the AED will advise rescuers to stand clear while it analyzes the heart’s rhythm. This analysis determines if the rhythm is shockable, such as a chaotic electrical pattern like ventricular fibrillation. If a shockable rhythm is detected, the AED will charge and advise a shock. The rescuer must loudly announce “Clear” and ensure no one is touching the patient before pressing the shock button.
The effectiveness of the electrical shock decreases significantly with every second that passes between compressions and shock delivery. Therefore, the pause for analysis and shock must be kept to a minimum, ideally under ten seconds. Immediately following the shock, or if the AED advises “No Shock Advised,” instantly resume high-quality CPR, starting with chest compressions.
This cycle of two minutes of CPR followed by a rhythm analysis is the standard operating rhythm for the AED. The AED will prompt the rescuer to stop compressions for re-analysis after approximately two minutes. The process repeats until emergency medical personnel arrive and take over care. The AED dictates the continuous decision-making process, ensuring the heart is either shocked or supported by compressions.
Special Situations for AED Use
Certain patient conditions require minor adjustments to the standard AED procedure. If the patient is lying in water or snow, move them to a dry area and quickly dry the chest before applying the pads. Excessive moisture can divert the electrical current away from the heart. For patients with implanted cardiac devices, such as pacemakers, place the pads several inches away from the visible device bulge to avoid damage or blocking the electrical pathway.
For pediatric patients, typically children under eight years old or weighing less than 55 pounds, use a pediatric attenuator key or specialized pads if available, as these deliver a reduced energy shock. If only adult pads are available, ensure the pads do not touch each other on the child’s smaller chest. In such cases, an anterior-posterior (front-to-back) pad placement may be necessary, with one pad on the center of the chest and the other on the back between the shoulder blades.