Cardiac arrest is a sudden medical emergency where the heart unexpectedly stops beating effectively, causing blood flow to cease. Immediate action is necessary to maintain circulation and give the person the best chance of survival. Cardiopulmonary Resuscitation, or CPR, is a technique involving chest compressions that artificially pump blood to the brain and other vital organs. An Automated External Defibrillator (AED) is a portable device that works alongside CPR by delivering an electrical shock to reset the heart’s chaotic electrical activity back to a normal rhythm.
The Priority Sequence: CPR and AED Deployment
The decision of when to use an AED is one of coordination and timing, prioritizing the maintenance of blood flow. The first step upon recognizing a person has collapsed and is unresponsive is to activate the emergency response system by calling for help. Immediately after the call, high-quality chest compressions must begin to circulate oxygenated blood. Every minute that passes without defibrillation for a shockable rhythm decreases the chance of survival significantly.
The AED should be retrieved and deployed as soon as it becomes available, even if CPR is already in progress. The priority is to minimize the interruption of chest compressions. If a second rescuer is present, they should prepare the AED while the first rescuer continues compressions. The pause in compressions should only occur for pad application and rhythm analysis.
Practical Steps for Using the AED
Using the AED begins the moment the device is brought to the patient, and the first step is to turn it on immediately. The AED provides clear, spoken instructions. Preparing the patient involves exposing the chest completely, and the skin must be as dry as possible, as moisture can interfere with the electrical current. If the chest is excessively wet or covered in thick hair, it should be quickly dried or shaved before proceeding.
The standard placement for adult pads is the anterolateral position, which ensures the electrical current passes directly through the heart muscle. One adhesive pad is placed on the upper right side of the chest, just below the collarbone. The second pad is positioned on the lower left side of the rib cage, slightly below the pectoral muscle. Once the pads are firmly attached to the bare skin, the pads’ cable must be plugged into the AED unit.
The device automatically begins to analyze the patient’s heart rhythm once plugged in. It is imperative that no one touches the patient during this analysis phase to ensure the AED reads the electrical activity accurately. The analysis determines if a shockable rhythm is present, and the device will communicate the next action clearly.
Responding to AED Prompts
The AED’s analysis will result in one of two distinct prompts, each requiring a specific action from the rescuer. If the device detects ventricular fibrillation or pulseless ventricular tachycardia—the two rhythms that respond to defibrillation—it will announce “Shock Advised.” Before pressing the shock button, the rescuer must loudly and clearly warn everyone to stand clear and visually confirm no one is touching the patient.
After the shock is delivered, the rescuer must immediately resume chest compressions, without checking for a pulse. Conversely, if the AED determines the rhythm is not shockable, such as in the case of asystole (a flatline), it will prompt “No Shock Advised.” In this scenario, the rescuer must immediately restart CPR, beginning with compressions. The AED operates on a cycle where it instructs the rescuer to perform two minutes of high-quality CPR before it automatically re-analyzes the heart rhythm. The pads are left attached throughout this process, allowing the device to monitor for any change in the heart’s electrical state.
Key Differences in Pediatric Use
When using an AED on a child, generally defined as under eight years old or weighing less than 55 pounds (25 kilograms), certain modifications are necessary. If available, pediatric pads or a pediatric key must be used to ensure the electrical dose is attenuated, or reduced, to a safer level for a smaller body.
The placement of the pads also changes for children to prevent the pads from touching each other, which would short-circuit the electrical pathway. Instead of the adult anterolateral placement, the pads are typically applied in an anterior-posterior configuration. One pad is placed on the center of the chest, and the second pad is placed on the child’s back, between the shoulder blades. If only adult pads are available and the child is small, this front and back placement is still recommended to ensure the pads do not overlap.