Sudden cardiac arrest is a life-threatening event where the heart abruptly stops beating effectively, causing blood flow to cease. Immediate action is necessary, and bystander intervention using Cardiopulmonary Resuscitation (CPR) and an Automated External Defibrillator (AED) significantly improves survival. While both techniques are utilized, they serve fundamentally different purposes and must be applied in a specific sequence.
The Fundamental Difference in Function
CPR is a manual technique designed to artificially maintain minimal circulation and oxygen delivery to the brain and vital organs. Chest compressions, performed at a rate of 100 to 120 times per minute, physically squeeze the heart between the sternum and the spine. This rhythmic pressure forces oxygenated blood through the circulatory system, temporarily delaying tissue death. While trained rescuers may deliver rescue breaths, the primary focus is on high-quality compressions.
The AED, in contrast, is an electrical device that addresses the chaotic heart rhythm often responsible for cardiac arrest. The device analyzes the heart’s electrical activity once pads are placed on the chest. If it detects a life-threatening rhythm, such as ventricular fibrillation, the AED delivers a controlled electrical shock. This shock momentarily stops all electrical activity, allowing the heart’s natural pacemaker a chance to reset to a normal, effective rhythm. CPR sustains life, but the AED corrects the electrical malfunction.
Recognizing the Need for Intervention
Intervention begins with a rapid assessment to confirm a cardiac emergency. First, check for responsiveness by firmly tapping the person’s shoulder and asking, “Are you okay?” If the person does not respond, immediately call for emergency medical services (EMS). If possible, send a second person to retrieve an AED. Delaying the call or the start of CPR decreases the likelihood of a positive outcome.
A person is in cardiac arrest if they are unresponsive and not breathing normally. Rescuers must recognize agonal breathing, which may sound like infrequent gasping or snorting. These are not effective breaths but a reflex due to oxygen deprivation. Mistaking agonal breathing for normal respiration can lead to a harmful delay in starting resuscitation. If the person is unresponsive and not breathing normally, the intervention sequence must begin without delay.
The Step-by-Step Emergency Protocol
The application of CPR and the AED follows a precise sequence focused on maximizing survival. Once unresponsiveness and abnormal breathing are confirmed, the immediate priority is to initiate chest compressions while emergency services are dispatched. High-quality, hands-only CPR involves pushing hard and fast in the center of the chest. This manual circulation must be established quickly, as brain cells begin to suffer damage within minutes of the heart stopping.
As soon as the AED arrives, the rescuer must power it on and follow the clear, voice-guided instructions. The two adhesive electrode pads are applied directly to the bare chest: one below the right collarbone and the other on the lower left rib cage. Once connected, the AED automatically analyzes the patient’s heart rhythm. No one should touch the person during this analysis phase, as movement or contact interferes with the rhythm assessment.
If the AED determines a shockable rhythm is present, it will prompt the rescuer to press the shock button after ensuring everyone is clear. Following the shock, or if the AED advises no shock is needed, the rescuer must immediately resume CPR, starting with chest compressions.
This cycle of two minutes of CPR followed by rhythm analysis continues until EMS personnel arrive or the person shows clear signs of recovery. The combined, uninterrupted use of CPR and the AED is the most effective way to manage cardiac arrest outside a hospital setting.