When an Automated External Defibrillator (AED) is applied during sudden cardiac arrest, it analyzes the heart’s electrical activity. The device recognizes two shockable rhythms: ventricular fibrillation (VF) and pulseless ventricular tachycardia (VT). When the AED announces “No Shock Advised,” it means the heart rhythm cannot be corrected by an electrical shock. This indicates a non-shockable rhythm, such as asystole (complete absence of electrical activity) or pulseless electrical activity (PEA), where the heart has electrical activity but is not pumping blood effectively. In these scenarios, the intervention is not defibrillation but immediate, high-quality chest compressions to manually circulate blood and oxygen.
The Immediate Next Step: Continuing CPR
When the AED gives the “No Shock Advised” prompt, the rescuer must immediately resume cardiopulmonary resuscitation (CPR). Minimizing the pause between analysis and the start of compressions is a major factor in improving survival chances. The AED pads must remain securely attached to the victim’s chest, allowing the device to continue monitoring the heart rhythm.
High-quality chest compressions are performed on an adult by pressing hard and fast in the center of the chest. The recommended rate is between 100 and 120 compressions per minute. Compressions should reach a depth of at least 2 inches (5 centimeters) but not exceed 2.4 inches (6 centimeters) to maximize circulation.
For a trained rescuer, the sequence involves a ratio of 30 compressions followed by two rescue breaths. Allowing the chest to fully recoil after each compression permits the heart to refill with blood between pumps. This manual effort aims to keep oxygenated blood flowing to the brain and other vital organs until the heart’s natural rhythm can be restored.
The Automated Reassessment Cycle
Rescuers must continue this cycle of high-quality CPR for approximately two minutes, which typically equates to five cycles of 30 compressions and two breaths. The AED is programmed to automatically re-analyze the heart rhythm after this two-minute interval. The device will issue a verbal command, typically “Stop CPR, Analyzing Rhythm,” requiring the rescuer to immediately pause compressions and stand clear of the victim.
This brief pause is necessary for the AED to accurately detect the heart’s electrical state without interference from compressions. Following the analysis, the AED will deliver one of two prompts: “Shock Advised,” indicating a shockable rhythm, or “No Shock Advised.” If a shock is advised and delivered, the rescuer must immediately restart CPR; if no shock is advised, the rescuer resumes CPR for another two-minute cycle.
Post-Resuscitation Care for the Responsive Victim
If the victim begins to show signs of life during the resuscitation effort, such as purposeful movement or breathing normally, the rescuer should stop chest compressions. This return of spontaneous circulation (ROSC) is a sign that the heart has restarted. The AED pads must be left attached, as the heart rhythm could change, and the AED will continue to monitor the patient.
The next step is to place the victim into the recovery position, provided there is no suspicion of spinal or neck injury. This position, on their side with the mouth pointed slightly downward, helps maintain an open airway and prevents aspiration of fluids. The rescuer should continuously monitor the victim’s breathing and consciousness until emergency medical services (EMS) personnel arrive to take over care.
When to Stop Using the AED
The general rule is to continue the resuscitation process, following the AED’s prompts and performing CPR, until one of three conditions is met. The first reason to cease intervention is when trained professional help, such as Emergency Medical Services (EMS) personnel, arrives on the scene and takes over care. Even after they arrive, the AED pads should remain on the victim until the medical team explicitly directs their removal.
Another reason to stop is if the rescuer becomes physically exhausted and can no longer deliver high-quality compressions. Effective CPR requires significant physical effort, and a fatigued rescuer cannot provide the necessary depth and rate. The final condition that justifies stopping is if the scene becomes unsafe, presenting a direct threat to the rescuer’s life, such as fire or an electrical hazard.