Defibrillation
- hellonotarealdr
- Jun 9
- 3 min read
Updated: Jun 25
Defibrillation involves delivering an electric shock to the heart to restore a normal rhythm. As it can often take some time to get a defibrillator, you should start with CPR* first and then use a defibrillator when it is available. Most AEDs (Automated External Defibrillators) will advise you when to continue with CPR after a shock has been delivered.
Stretch!
AEDs analyse the heart's rhythm and only shock if the rhythm is shockable. This means it is present, but irregular. In cases like asystole (flatline), AEDs will not shock—only CPR can help until medical support arrives.
Most public places will have a defibrillator available — schools, airports etc are required by law to have them, and most high streets have one close by. If there are bystanders around you, ask them to fetch the defibrillator while you begin CPR.
When the defibrillator arrives, you do not need to remove jewellery. Doing so delays the shock and can lead to treatment not being given in time. However, bras should be removed because the pads of the defibrillator need to be in full contact with skin. You can, however, lay the bra back over the casualty* after the pads have been placed to preserve dignity.
To use a defibrillator/AED:
Turn on the defibrillator and follow the voice prompts for instructions.
Apply the pads as instructed: place one on the upper right chest below the collarbone and the other on the lower left side below the armpit. Use the provided diagrams/instructions for guidance.
Let the AED carry out the analysis — ensure that no one is touching the casualty while this is happening.
Deliver the shock if advised (on a semi-automatic defib) or (on a fully automatic defib) let the shock be carried out itself.
Resume CPR — perform compressions immediately, until the AED reassesses or until the ambulance arrives.
Stretch!
The heart isn’t “restarted” like in movies—instead, the shock stops chaotic electrical activity, allowing the heart’s natural pacemaker to regain control.
CPR and defibrillation are not mutually exclusive. In fact, they work together as part of the “Chain of Survival”, which aims to maximise survival changes. This sequence includes:
Early recognition and calling for help.
Immediately starting CPR.
Defibrillation as soon as possible to reset the heart’s rhythm.
Further care by emergency responders.
CPR keeps oxygenated blood flowing around the body, to the brain especially, while the AED assesses and delivers a shock to restart the heart’s rhythm. The sooner these are performed, the more likely the casualty is to survive and the lower the chances of complications.
Summary:
Defibrillation delivers an electric shock to restart the heart’s normal rhythm during cardiac arrest. Start CPR immediately and use an AED as soon as it is available—most devices give clear voice instructions. Pads are placed on the upper right chest and lower left side. Make sure no one touches the casualty during the shock, then resume CPR. Defibrillation and CPR work together as part of the Chain of Survival to maximise survival chances.
Glossary:
CPR: stands for cardiopulmonary resuscitation, it is the treatment you give when someone's heart has stopped. It's made up of chest compressions and rescue breaths - we have a lesson on it if you're interested!
Casualty: the person that's hurt in a first aid scenario.
For Older Learners:
Use these questions to challenge yourself!
If an AED does not advise a shock, but the person is still unresponsive and not breathing, what should you do next—and why might the AED have made that decision?
Imagine you need to use an AED on a casualty wearing a bra. Explain how you would balance the need for effective defibrillation with respecting the casualty’s dignity. Why is this balance important?
Many people hesitate to use a defibrillator because they are afraid of doing it wrong and getting sued. Research what protections are available for bystanders that perform first aid. Do you think these protections are fair? Why or why not?
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