The Automated External Defibrillator (AED) is designed to analyze a person’s heart rhythm and determine if an electrical shock is needed. The device looks for ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT), which are shockable rhythms. When the AED announces “No Shock Advised,” it indicates the person’s heart rhythm cannot be corrected by defibrillation. This message does not mean the person is safe or has recovered; it directs the responder to adjust the immediate care strategy.
Immediate Action: Resuming Chest Compressions
The “No Shock Advised” message often means the heart is either completely still (asystole) or exhibiting organized electrical activity without a pulse (pulseless electrical activity, or PEA). Since neither of these rhythms respond to an electrical shock, delivering energy would be ineffective and delay life-sustaining measures. The priority shifts entirely to circulating oxygenated blood manually through high-quality chest compressions.
The immediate action after the AED delivers the “No Shock Advised” message is the rapid resumption of chest compressions. Responders should aim for a compression rate between 100 and 120 compressions per minute to maximize blood flow to the brain and other vital organs. Each compression needs to be delivered forcefully, pressing down on the center of the chest to a depth of at least two inches (about five centimeters) in an adult.
Minimizing the time between the AED’s analysis ending and compressions beginning is a defining factor in patient survival. Brief pauses in compressions can cause a significant drop in coronary perfusion pressure. The goal is to keep the “hands-off” time to less than ten seconds during the resuscitation attempt.
Assessing for Pulse and Breathing
High-quality chest compressions are maintained for a two-minute cycle before the AED automatically signals for re-analysis. Following this two-minute period, the responder should quickly perform a manual assessment for signs of life. This assessment involves checking for a pulse and observing if the person is breathing normally.
The pulse check is performed on the carotid artery, located in the neck. The responder should feel gently for a pulse for no more than ten seconds to avoid interruption of compressions. Simultaneously, the responder needs to look for signs of normal breathing, distinguishing it from gasping or ineffective breaths.
Three distinct outcomes are possible following this rapid assessment, each dictating a different course of action. If a pulse and normal breathing return, the person should be placed into a recovery position while waiting for emergency services. If the pulse returns but the person is not breathing normally, the responder should begin providing rescue breaths while monitoring the pulse closely. If there is still no pulse and no normal breathing, the responder must immediately transition back to the continuous resuscitation cycle.
Maintaining the Resuscitation Cycle
If the assessment confirms the person still lacks a pulse and normal breathing, the responder must immediately continue with chest compressions. The AED is programmed to automatically prompt the responder to stand clear for re-analysis every two minutes to re-evaluate the heart’s electrical rhythm. Responders must follow these voice prompts, as the rhythm may have converted to a shockable state during the two minutes of manual circulation.
Even if the device repeatedly advises “No Shock Advised” on subsequent analyses, the continuous cycle of two minutes of compressions must be maintained. The mechanical actions of cardiopulmonary resuscitation provide a temporary and necessary bridge, keeping oxygen flowing until the underlying cause of the arrest can be addressed by advanced medical providers. The electrode pads applied to the chest must remain firmly attached to ensure the AED can accurately monitor the heart’s electrical activity and deliver a shock if the rhythm changes.
The responder must continue this structured, two-minute cycle of compressions and AED analysis until one of three conditions is met. These conditions are: the person shows clear signs of recovery, Emergency Medical Services (EMS) personnel arrive and take over, or the responder becomes too exhausted to continue.