Defibrillators (AEDs)

A defibrillator is a life-saving device used when someone experiences a Sudden Cardiac Arrest (SCA). During an SCA, the heart stops pumping blood effectively due to a sudden electrical disturbance. The casualty becomes unresponsive and is not breathing normally. Without immediate treatment, around 95% of SCAs are fatal.

Defibrillators, together with effective CPR, are the only treatment that can help restore a normal heart rhythm. The device analyses the casualty’s heart and identifies whether a shock is needed. If a shockable rhythm is detected, the defibrillator will either:

• Deliver the shock automatically if it is a fully automatic AED
• Instruct the responder to press a button if it is a semi-automatic AED

More than one shock may be required. The defibrillator will continue to guide the responder through each step of the response.

It is important to understand that a heart attack is not the same as a Sudden Cardiac Arrest. Although symptoms may appear similar, a defibrillator should only be used if the person has collapsed, is unresponsive, and is not breathing normally. These are the key signs of SCA. A heart attack can sometimes lead to SCA. In that case, using a defibrillator without delay is vital.

Sudden Cardiac Arrest (SCA) is caused by an electrical failure in the heart. A heart attack is a circulatory issue caused by a blockage that restricts blood flow to the heart muscle. These are two different medical emergencies and require different responses. Heart attacks usually involve chest pains, shortness of breath, feeling weak, or generally unwell. The casualty remains conscious and breathing.

SCAs causes immediate collapse, unresponsiveness, and abnormal or absent breathing. It happens without warning and requires urgent action.

pIt’s important to recognise the difference and respond fast in these emergencies. A person suffering a heart attack requires urgent medical attention, while a person in SCA requires prompt defibrillation and CPR. Using an AED within the first 3-5 minutes of SCA increases a casualty’s chances of survival from 6% to 74%. 

Automated External Defibrillators (AEDs) are designed to analyse a casualty’s heart rhythm and only deliver a shock if one is required. You cannot harm a casualty by using a defibrillator, as the device will not allow a shock to be given unless the rhythm is shockable.

There are instances where a shock may not be advised by the AED:

• If the casualty is having a heart attack but remains conscious and responsive. In this case, the defibrillator will analyse the rhythm and determine that no shock is needed.
• If an unresponsive casualty regains consciousness before pad application or during analysis, the AED will not deliver a shock.

Some situations require extra care during pad placement:

• Pacemakers or medical patches - Electrode pads should be placed on the upper right chest and the lower left side of the chest. As pacemakers are typically located on the upper left chest, they do not usually interfere with pad placement. However, avoid placing pads directly over any visible lump or medical device.
• Wet environments - If the casualty is wet or lying in water, move them to a dry surface and dry the chest thoroughly before applying pads to ensure proper adhesion and analysis.

Defibrillator costs vary depending on the brand, type, and any features such as advanced monitoring, paediatric modes or WiFi capability. To help reduce costs, we offer short-term hire and long-term rental options, as well as our range of defibrillator packages, helping you purchase everything needed for your emergency set-up in one package.

Yes. There are three main types of defibrillators, each designed for different uses:

• Automated External Defibrillators (AEDs)
• Implantable Cardioverter Defibrillators (ICDs)
• Wearable Cardioverter Defibrillators (WCDs)

AEDs are portable devices found in public spaces, schools, and workplaces. They are designed for use by anyone in an emergency, guiding responders with clear voice and visual instructions to deliver treatment during a Sudden Cardiac Arrest (SCA).

ICDs are small, battery-powered devices implanted in the chest. They monitor heart rhythms continuously and deliver a shock if a life-threatening arrhythmia is detected. These are fitted by medical professionals and used in individuals with known cardiac conditions.

WCDs are external, vest-like devices worn on the chest. Like ICDs, they monitor the heart and deliver a shock when needed. WCDs are often used as a temporary measure while a decision is made about long-term treatment.

Unlike AEDs, which are designed for public access and immediate response, ICDs and WCDs are prescribed and managed by healthcare professionals.

Public Access Defibrillators (PADs) are commonly found in locations with high footfall, including schools, community centres, train stations, places of worship, leisure facilities, shopping centres, and hospitality venues. Devices are often stored in wall-mounted cabinets with 24-hour access and marked with clear signage to support fast retrieval.

When a casualty collapses and is not breathing normally, call 999. The emergency call handler provides the nearest defibrillator location and, if required, the access code for the cabinet.

This information is sourced through The Circuit, the national defibrillator network. The Circuit connects AEDs to NHS ambulance services across the UK, ensuring responders are directed to the nearest available device.

If your defibrillator is in a fixed location, registering it on The Circuit is strongly recommended. This helps ensure emergency services can direct responders to the device when it is needed most.

In a suspected Sudden Cardiac Arrest (SCA), call 999 immediately and begin CPR. If someone is with you, send them to retrieve the nearest Automated External Defibrillator (AED). Do not stop CPR to fetch a defibrillator if you are alone.

The 999 operator will guide you through the steps and confirm the location of the closest registered device.

Once the defibrillator arrives: 

1. Turn on the AED by pressing the power button. The device provides clear audio and visual instructions.
2. Locate the electrode pads (either inside the casing or in a dedicated storage compartment).
3. Remove the pads from the packaging and apply them to the casualty’s chest as shown in the images (or as instructed by the AED).
4. Wait for the defibrillator to analyse the heart rhythm, ensuring you are not touching the casualty at this time.
5. If using a semi-automatic AED, press the shock button if instructed to do so by the device. A fully automatic AED delivers the shock automatically after a 3-2-1 countdown, with no action required by the responder.
6. Resume CPR when instructed by the AED, aiming for 100-120 chest compressions per minute, following the audible beat from the unit. 

Defibrillators are designed to be used by anyone, with or without formal training. Understanding how to respond in an emergency improves confidence and readiness.

At defibshop, we offer a range of accredited training courses through our partner, Imperative Training. These include first aid, AED awareness, mental health, and specialist lifeguard training to help individuals and teams respond effectively.

Defibrillators are built to provide a long operational life when maintained correctly. This includes replacing the battery and electrode pads in line with the manufacturer’s guidelines. At defibshop, we offer a 10-year warranty* on our defibrillators, providing long-term reassurance against manufacturing defects. We also offer defibrillator servicing and maintenance plans to help ensure your device is well-looked after and prepared for every emergency, including our free battery and pad reminder service.