An automated external defibrillator, or AED, is a portable device that can help a person in sudden cardiac arrest. Cardiac arrest means the heart has stopped pumping blood effectively, so the brain and body are not getting oxygen. Fast action matters because survival chances can drop by about 7% to 10% for every minute without CPR and defibrillation.
AEDs are designed so trained students, teachers, coaches, and bystanders can use them safely in an emergency.
Understanding Safety & Emergency Preparedness: How to Use an AED
A cardiac arrest can happen when the heart's electrical system becomes disorganized. Instead of producing one strong, coordinated squeeze, the lower chambers may quiver rapidly. This rhythm is called ventricular fibrillation.
Blood then stops moving properly to the brain, lungs, and other organs. An AED does not simply force every stopped heart to restart. Its sensors read the electrical pattern through the sticky pads.
The machine uses a computer program to decide whether a shock could help. A shock briefly stops the chaotic electrical activity. This can give the heart's natural pacing system a chance to regain an organized rhythm.
The pads do more than deliver energy. They create a path across the chest so the AED can measure the heart and, when appropriate, send energy through it. Good skin contact matters.
A wet chest should be dried quickly, since water can affect pad contact. Thick chest hair can prevent a pad from sticking well. Many AED kits include a razor for this reason.
Medication patches should be removed before a pad is placed over that area, then the skin should be wiped. The device pictures show placement clearly, so follow them if the person's body size makes the usual positions difficult.
In a real emergency, the AED gives calm, step by step voice instructions. Students may see these devices in schools, sports centres, airports, shopping areas, or train stations. They are often kept in a marked wall cabinet.
The machine may tell rescuers to continue chest compressions, pause for analysis, or prepare for a shock. These pauses need to be as short as possible because compressions keep some blood moving while the heart is not pumping effectively.
After a shock, the usual action is to return to CPR when the device instructs it. The AED keeps checking the rhythm at intervals and may decide that no shock is needed.
Safety depends on paying attention to the scene and the device prompts. Make sure nobody is touching the person during rhythm analysis. Before a shock, look around the whole person and clearly state that everyone must stay clear.
Do not use an AED in standing water or where flammable fumes may be present. For infants and children, use child pads or a child setting when available, following the AED instructions. If only adult pads are available in a life threatening emergency, the device instructions and local training guidance matter.
Practice sessions are valuable because they teach simple habits, including finding the nearest AED, opening the case, exposing the chest, and listening rather than guessing. Emergency responders can later use the AED's stored timing and rhythm data to understand what happened.
Key Facts
- Call emergency services first, then get the AED and start CPR if the person is unresponsive and not breathing normally.
- AED = automated external defibrillator, a device that checks heart rhythm and gives a shock only if needed.
- CPR rate = 100 to 120 compressions per minute for high quality chest compressions.
- Survival chance can decrease by about 7% to 10% per minute without CPR and defibrillation.
- Pad placement: one pad on the upper right chest and one pad on the lower left side below the armpit.
- Safety rule: no one touches the person while the AED analyzes or shocks, because touching can interfere with the device and may be unsafe.
Vocabulary
- AED
- An AED is a portable device that analyzes a person's heart rhythm and can deliver an electric shock to help restore a usable rhythm.
- Cardiac arrest
- Cardiac arrest is when the heart suddenly stops pumping blood effectively to the body.
- Defibrillation
- Defibrillation is the delivery of a controlled electric shock to stop a dangerous heart rhythm so the heart can restart a normal rhythm.
- CPR
- CPR is cardiopulmonary resuscitation, a method of chest compressions and sometimes rescue breaths used to move blood and oxygen during cardiac arrest.
- Heart rhythm
- Heart rhythm is the pattern of electrical activity that controls how the heart beats.
Common Mistakes to Avoid
- Waiting to use the AED until a professional arrives is wrong because every minute without defibrillation lowers the chance of survival.
- Touching the person while the AED is analyzing or shocking is wrong because it can affect the rhythm reading and may put the rescuer at risk.
- Placing pads over clothing is wrong because the pads need direct contact with bare, dry skin to read the rhythm and deliver energy properly.
- Stopping CPR for a long time to set up the AED is wrong because chest compressions should be interrupted as little as possible.
Practice Questions
- 1 A person collapses at 2:00 p.m., and an AED shock is delivered at 2:06 p.m. If survival chance drops by about 8% per minute without defibrillation, estimate the total percentage drop in survival chance.
- 2 During CPR, you give 110 compressions per minute. How many compressions would you give in 2 minutes if you kept the same rate?
- 3 A student brings an AED while another student is doing CPR. Explain the correct order of actions from turning on the AED to resuming CPR after a shock or a no-shock message.