How to use a Defibrillator

The defibrillator is an invention that saves lives literally every day. It is entirely possible (even likely) that, by the time you have read this feature, someone, somewhere will have had their heart reset by one of these life saving beauties. It should come as no surprise, then, that the global de fib market is expected to become a $14Bn a year industry in the next few years.

So here is our ultimate guide to the defibrillator. You never know, you might discover a SHOCKING fact or two!

What is a Defibrillator?

Simply put, a defibrillator is a device that administers a high-energy electrical shock directly to the heart of the person who is experiencing cardiac arrest. This shock is known as defibrillation, hence the name of the device. An automated external defibrillator, or AED, is a portable version of the same instrument.

Automatic defibrillators work by monitoring the patient’s heart rhythm (or lack thereof) and automatically administering a life saving shock if need be. A semi-automatic defibrillator, on the other hand, requires the person using the device to push a button in order to deliver the electric shock. 

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An automatic defibrillators have a ‘manual override’ function that allows the user to push the button and administer the electric shock without first scanning the patient’s heart. These units are usually reserved for highly trained personnel such as paramedics and other emergency responders.

A specially adapted defibrillator may be used on children from the ages of one onwards, while the standard type may be used on adults of any age.

What Does a Defibrillator Actually Do?

You might well have encountered any number of scenes in TV shows, movies, books or video games where in a person is announced to be “flat-lining” (meaning that their heart is in a state of asystole – not generating any electrical impulses). The person is then miraculously saved through the use of an automatic defibrillator. Unfortunately, this is a myth. A defibrillator can do nothing to help a heart that has completely stopped.

In fact, a defibrillator actually works by stopping a still-beating heart.

A sudden cardiac arrest, or SCA, occurs when the heart is still fluctuating, just not as it should be. In cases like these, a defibrillator is the best tool we have to save the patient’s life. However, if the heart has totally ceased to beat, a defibrillator is not the answer.

On any given day, the heart uses electrical impulses to contract its muscles and pump oxygenated blood around the body.

The heart does this by polarizing its pacemaker (this is also known as the sinus node, a clustering of cells situated in the upper part of the right atrium). The pacemaker is one of the most important parts of what is called the cardiac conduction system, which ultimately controls the heart rate.

Depolarization of the pacemaker forces the heart to contract, which in turn produces an electrical waveform (known as PQRST) that is recognisable to the electrocardiogram (ECG) device housed within the defibrillator.

In effect, the defibrillator can quickly and easily detect whether the patient’s heart is beating and even at what rate it is beating.

If the rhythm of the heart is irregular, such as if the electrical pulses are too short and frequent for blood to pass through the ventricles, the defibrillator will depolarize the entire system. This act quite literally re-starts the heart, allowing for normal electrical activity to resume.

If the shock is not strong enough to affect complete re-polarization, the device will sense this, as before. In this case, a second shock is needed to properly re-polarize the system. 

A defibrillator simply re-sets the heart back to a healthy rhythm, hopefully saving the life of the patient in the process. Without immediate treatment, 90-95% of cardiac arrests will cause death, but if a defibrillator is used, with 3-5 minutes, they chances of survival increases up to 74%.

A Brief History of the Defibrillator

Luigi Galvani had been using electricity to stimulate inert animal muscle as far back as the mid 1700s. Giovanni Aldini, Galvani’s nephew, built upon his uncle’s work in significant fashion, specifically by making dead animals move via jolts of electricity.

In London, 1803, Aldini was given the corpse of an executed murderer named George Foster to work on. During a public demonstration of his methods, Aldini was able to open one of the dead man’s eyes, move his facial muscles, raise one arm and even clench his fist.

As we can see, the idea that a well-placed electrical current might ‘jump start’ a human heart had been floating around in the popular imagination since at least the early 19th century. Indeed, the creature in Mary Shelley’s ‘Frankenstein’, (a story partly inspired by Aldini’s work) was brought to life by a bolt of lightning.

It wasn’t until the end of the century, however, that a breakthrough would offer defibrillation an avenue through which it could migrate from the realm of fantasy to that of reality.

Working at the University of Geneva, Jean-Louis Prevost and Frédéric Batelli formally invented the process of defibrillation in 1899. The process was used to successfully induce fibrillation in dogs. Sadly, the pair used very high voltages in their experiments, which invariably incapacitated the test animals’ hearts, killing them almost immediately. This led the procedure to be disregarded as far too dangerous for human trials.

By the dawn of the 20th century, however, cardiac arrest had taken over infection to become a leading cause of death. People were now surviving previously fatal illnesses in record numbers and subsequently living to an age where heart disease was becoming a problem for them.

As is so often the case, necessity proved the mother of invention

Perhaps the earliest known ancestor of the modern defibrillator was featured in a 1933 issue of ‘Popular Mechanics’ magazine. Designed by Albert S. Hyman, the ‘Hyman Otor’ device was proudly proclaimed as a “self starter for dead man’s heart”. Although it was never successfully used, the device was an ingenious design, which used a long needle inserted between the ribs in order to fibrillate the heart without opening the chest.

Finally, in 1947, renowned heart surgeon Claude Beck, who also pioneered CPR as well as many forms of heart surgery, successfully performed the first defibrillation. His patient was a 14-year-old boy whose heart began fluctuating after surgery. Beck used a defibrillator that had been designed and developed by inventor James Rand, a friend of his. The device featured two silver ‘paddles’ (read: spoons) that were held against the heart itself, sending 60Hz directly into the organ. The boy survived and the world was amazed.

7 years later, William Kouwenhoven and William Milnor had performed the world’s first closed-chest defibrillation (on a dog). 2 years after that, Paul Zoll had performed the first closed-chest defibrillation of a human being.

In 1966, the first patients were defibrillated while en-route to hospitals in Belfast. Finally (for our round-up, at least), former United States President Lyndon B. Johnson had his life saved by a portable defibrillator in 1972. This legitimised the device in the eyes of many people, as ‘LBJ’ was a very high profile patient.

Since then, the devices have been getting easier to use, more efficient and much more ubiquitous in our lives. Today you can see them not just in hospitals and ambulances, but also in schools, entertainment venues, airports, casinos and even private homes.

How to Use a Defibrillator

When a person experiences sudden cardiac arrest, they will have about 10 minutes to be revived, with their odds of survival declining about 10% with each minute that passes without resuscitation.

This sounds pretty scary – and it is, but the good news is that advice and help is easily obtainable, both from the emergency services and from the unit themselves!

Automated external defibrillators are designed to be easy to use. Their basic operation, then, is fairly simple. The following method is taken from the St. John’s Ambulance website.

The first thing to do, in all cases, is perform a primary survey on the person. Always use the ‘Dr. ABC’ (Danger, Response, Airway, Breathing and Circulation) method before administering any first aid to an unconscious or seriously injured person.

If the person is unconscious or not breathing normally, call 999 (use the speakerphone option) and begin to start CPR as soon as you are able to do so. Don’t worry if you don’t know how, guidance will be given over the phone.

If possible, you should have somebody else make the call while you begin the resuscitation attempt.

Do not leave the patient unattended in order to look for a defibrillator. Either ask somebody else to look for one, or continue to administer CPR until the nhs ambulance services arrive (it will have one as a matter of course).

Ask another person to switch the defibrillator on and remove the pads while you continue CPR.

In order to use the defibrillator, the other person must remove or cut through any clothing that is in the way of the patient’s bare chest. Use a handkerchief, tissue or clothing to wipe away any sweat. The defibrillator will give you further instructions, as will the person on the phone.

Next, remove the paper from the pads and attach them to the person. The first pad goes on the upper right, below the collarbone, while the second pad goes on the left side, just below the armpit.

The defibrillator will then detect the patient’s heartbeat (using the method described above). Stop CPR and ensure that no one else touches the person during this time.

Today’s defibrillators are so clever that they will advise you on what to do next. If a shock is required, it will ask you to press the button or else the device will administer one automatically. 

You may then be asked to continue CPR for a further two minutes before the machine re-analyses the person.

If a shock is not needed, you must continue CPR for another two minutes, at which point the defibrillator will re-analyse the person.

If this does not work, place the person into the recovery position, leaving the defibrillator attached. Monitor the person closely, being prepared to continue CPR if it becomes necessary. 

With any luck, the ambulance will arrive soon, and highly trained staff will take over. If you have followed this advice, you may have saved the patient’s life. Even if they do not survive, you can take at least some comfort from knowing that you acted properly and took all the available action you could.

If you are the person tasked with finding the nearest defibrillator, look for this symbol:File:Automated External Defibrillator (symbol).svg - Wikimedia Commons

How to use a defibrillator

Defibrillators only work in cases of cardiac arrest. In many other cases, CPR is enough to bring the person around.

Once attached, the device will scan the patient’s heartbeat and issue instructions on what to do next. If the defibrillator does not administer a shock or ask the user to do so, no shock will be forthcoming.

In the case of patients with a lot of chest hair, you should try to cut or shave the hair before applying the pads to the patient’s skin, as hair can prevent electricity conduction (believe it or not). If this is not an option, apply extra pressure to the pads in order to ensure conduction.

There are conditions that can cause problems for even the best defibrillators. You should avoid using a defibrillator if:

  • The person is lying in water, is covered in water or their chest is soaked with sweat.
  •   The pad needs to be placed over a medical patch or dressing. In this case, remove the dressing and clean the area before applying the pads.
  •   The person is younger than 12 months old (this requires special training).
  •   The person is younger than 8 years old and you are using an adult defibrillator.
  •   The person is experiencing a heart attack. A heart attack and a cardiac arrest are two distinctly different things. If the person is still breathing and responsive throughout the event, they are experiencing a heart attack, not a cardiac arrest. In this case, a defibrillator can make things considerably worse. Instead, stay calm, call 999 and take it from there.
  •     The person is wearing a ‘DNR’ or ‘do not resuscitate’ band. You can still opt to help them, but if it is not their wishes, then they may not thank you for doing so.
  •     The defibrillator appears to be broken, faulty or is not working properly. Explain these concerns to the emergency services for further advice.

Finally, we come to the issue of electronic pacemakers. An electronic pacemaker is a small device that is placed within the chest of a person with abnormal heart rhythms (arrhythmia). It works by administering low-level electrical charges that help to control the heart during these incidents.

The pacemaker does not relate to heart attacks or most forms of cardiac arrest, it is simply installed to prevent the heart’s rhythms from becoming too fast or too slow. While a slow heart rate can be a cause for cardiac arrest, this is quite uncommon.

A pacemaker is fairly easy to spot because you will be able to see and feel a small, hard lump in the patient’s chest, usually just below the left collarbone. It should be about half the size of a deck of cards. It is important that you DO NOT place either of the defibrillator pads directly over the device. Instead, ensure that the pad is at least one inch away from the pacemaker, although further is better.

If the pacemaker delivers a small shock while the person is in cardiac arrest, you will have to wait 30 – 60 seconds for the device to complete its cycle, whereupon you may attempt defibrillation again.

NOTE: Although pacemakers are designed to withstand defibrillation, you should always check with emergency service personnel before administering defibrillation to a person with a pacemaker.

How much is a defibrillator?

Typically, the lowest prices are reserved for the ‘affordable’ models, which retail at around £500 – £1000. Mid-range models can cost around £1000 – £3000. The premium models, however, can cost between £3000 and £14,000 (with prices for specialist models venturing higher even than that).

When purchasing a defibrillator, consider the people most likely to need it (children, for example, require specific models). You also need to consider storage (the device needs to be in a secure, safe place that is also easily accessible in case of emergency) as well as the cost of upkeep. 

Registration, Maintenance & Servicing Information

Legally speaking, you are under no obligation to register your defibrillator with anyone at all. However, registering your unit with ‘The Circuit’ (the national defibrillator network) really could help to save lives.

At present, there are tens of thousands of public access defibrillator units in the country that are completely unknown to the emergency services. This means that a person could literally be dying in the same building as the device that could have saved his/her life. If you don’t let the proper authorities know about your defibrillator, then they will be unable to direct people to it, even if you are the one who needs it.

Knowing the location and means that it is much more likely to be used. The Circuit is also committed to maintaining the upkeep of the nation’s defibrillators. To this end, they will remind you to check yours regularly and make sure that the pads are in date. Again, this is the sort of attention to detail that saves lives.

Whether you register or not, you will still have to maintain your defibrillator. Some retailers will provide all-inclusive servicing and maintenance packaging as part of the purchase, others will require you to service/maintain your device entirely at your own discretion.

To fully check your AED, you must change the pads and batteries every two years. You should also check the screen readout and basic functionality of the device at regular intervals. Most are self-checking and will display a green or red light depending on the outcome of these tests. Replacement parts, sadly, can be very expensive (some costing as much as £800). However, if the red light shows, these parts must be replaced, otherwise the device may not function properly at a crucial time.

UK map of defibrillators

It is also recommended that you have the device properly examined by a professional around once a year, although this can also be added to the terms of the initial sale and organised via the retailer. Be aware also of product recalls and warranty terms.

Most should last you between 5 and 7 years. In some cases, it is possible to pay a small regular fee and have your device automatically updated and replaced with a new model whenever it is required, but this is not standard practice for every retailer.

The Reviews

iPAd SP1

Don’t let the name fool you. Apple haven’t developed a defibrillation app that can be downloaded onto their best-selling tablet so you can save someone’s life while simultaneously beating your high score on ‘Angry Birds’.

The iPAD SP1 is, in fact, a nominated device of the British Heart Foundation. It is used by the ambulance service, as well as by various community initiatives aimed at saving lives. The SP1 is also the on-hand device used by various British supermarket chains, including ASDA, Co-Op and Sainsbury’s.

This unit self-tests, ensuring that it is always ready to be used by anyone. The pre-connected ‘smart’ pads are stored in a clear compartment below the device. No setup process is required beyond switching the unit on. Once this has been achieved, a calm, clear voice guides the user through the process – only administering a shock if necessary.

The automatic option will analyse the patient’s heart rhythm and administer the shock automatically. The semi-automatic option yields to the user (in this case a person with the requisite experience and training) and requests that they push the button and administer the shock themselves. 

In automatic mode, the voice commands are joined by simple, illuminated diagrams, which are displayed on the device’s screen (in case the user is confused, unable to speak English or is hard of hearing).

The SP1 also features a variety of other features that increase usability. For example, it has an ambient noise detector, which automatically measures the levels of ambient sound around it and adjusts the volume of the automated voice accordingly.

The iPAD SP1 features a visual indicator that displays battery life (as well as alerting the user to any functionality issues the unit may be encountering) and has the ability to easily switch between ‘adult’ and ‘child’ modes without needing to change pads. The safety cover even prevents an accidental switch between the ‘adult’ and ‘child’ modes.

The SP1 has the capacity to record data from up to 5 usages (up to 15 hours worth), which can be easily transferred to an SD card should the data need to be examined for any reason.

Additionally, the unit also has a drop tolerance of 1.22 metres.

This unit has a pretty good shelf life. It will be guaranteed for 7 years at the point of purchase, or 10 if registered with the manufacturer. The battery is guaranteed for 4 years. The electrode pads, however, will need replacing after 3 years.

Weight: 2.4kg

Dust/Water Resistance Rating: IP55 (Basic water resistance, cannot be soaked or submerged).

Drop tolerance: 1.22m drop to any edge, corner or surface

Batteries: Lithium battery (lasts up to 4 years, can be re-charged as well as replaced).

Suitable For: Novice users.


 ✅ Many handy features, including ambient noise detector and audio/visual prompts.

 ✅ Comes with pre-connected adult/child pads, as well as pad life indicator showing the user how long the pads have left.

 ✅ Used by the British Heart Foundation, as well as a number of high profile businesses.


 ❌ Only features ‘fully automatic’ and ‘semi automatic’ modes, which might not make it ideal for experienced professionals.

Zoll AED Plus

“Son of Joe-El, kneel before Zoll!” – and well you might, because the Zoll AED Plus is the heaviest unit on this list.

Aside from its weight (which, in fairness includes both battery and pads), this unit is notable for actually offering the user CPR instructions.

Not every patient will require defibrillation, but most, if not all, will need CPR. The task of administering this relatively simple, yet often lifesaving treatment can be very daunting indeed to those without the necessary experience.

As we all know, CPR can potentially place a victim who cannot be shocked into a ‘shockable’ state, thus saving their life. Even if it doesn’t, CPR can keep the blood circulating long enough for paramedics to arrive and revive the patient. This, then, is an important feature.

With the Zoll delivering clear, easy-to-follow instructions, the CPR process is easier than ever. It will even tell you whether you need to “push harder” or if you’re making “good compressions” (real examples), which is a very handy feature indeed. These audio instructions are accompanied by helpful images. All in all, this model’s patented ‘CPR Help’ technology is a real boon.

The unit is also pretty durable, with a drop tolerance of 1.5 metres. The removable lid can even be placed beneath the patient’s shoulders in order to keep their airway open.

Pads need to be applied separately, however this is a relatively simple process, designed for use by non-professionals facing difficult circumstances. The child pads are sold separately. The pads have a shelf life of around 5 years and will not need to be replaced unless they have been used.

This unit comes with a 5-year guarantee, which can be extended to 7 years upon registration of the device.

Weight: 3.1kg

Dust/Water Resistance Rating: IP55 (Basic water resistance, cannot be soaked or submerged).

Drop tolerance: Withstand a drop of up to 1.5 metres

Batteries: Lithium battery (lasts up to 4 years, can be re-charged as well as replaced).

Suitable For: Novice & Professional users.


 ✅ High quality, long lasting batteries.

 ✅ CPR Help function is extremely useful and works well.

 ✅ The unit offers real-time feedback regarding the user’s CPR technique.

 ✅ Removable lid helps to keep airways open.


 ❌ Child electrodes are sold separately.

 ❌ The manufacturer’s guarantee is, frankly, not all it could be.

 ❌ This defibrillator is overly heavy. 

Cardiac Science Powerheart G5

Poswerheart g5

Cardiac Science are a global leader in AED design and manufacturing. The company’s designs always focus on easy operation and quick, efficient usage. The Powerheart G5 is no exception to this rule.

The Powerheart G3, a precursor to the G5, was exceptionally highly regarded, being selected by both the British Heart Foundation and others to be the unit of choice for a major defibrillator program across the UK.

So, how does the G5 stand up to its illustrious predecessor?

This compact, fully automatic unit offers even the most inexperienced users ample opportunity to save lives. Clear, concise audio instructions are given to the user. If the device identifies the need to induce a shock, it will do so entirely automatically.

 Additionally, the Powerheart G5 is the first AED to combine variable escalating energy with fast shock times. It can deliver a post-CPR shock in as little as 10 seconds.

The unit is rescue-ready at all times, self-checking its internal components as well as its batteries, software and pads on a daily, weekly and monthly basis. An audio warning will sound if the system encounters any problem or malfunction. The G5 is also approved for military use and has a drop tolerance of 1.2 metres.

The battery has a shelf life of about 5 years in standby mode, but replacement will be offered after 4 years as part of the guarantee, which covers the device for 8 years.

All things considered, the Powerheart G5 would seem to be a worthy successor to the G3, even surpassing it in certain key areas. As a fully automatic AED, the G5 does all the hard work for the rescuer, allowing them to simply follow the instructions issued by the device and, hopefully, save a life in the process.

Weight: 2.6kg

Dust/Water Resistance Rating: IP55 (Basic water resistance, cannot be soaked or submerged)

Drop tolerance: Withstand a drop of 1.22m and has been tested to military standards

Batteries: Lithium battery (lasts up to 4 years, can be re-charged as well as replaced).

Suitable For: Novice level.


 ✅ Fast shock times (as short at 10 seconds).

 ✅ Combines these rapid shock times with variable escalating energy, the first AED to do so.

 ✅ Respected designer with experience creating highly regarded AEDs.

 ✅ Excellent guarantee.


 ❌ Infant/child pads sold separately.

HeartSine Samaritan PAD

A smart, lightweight unit, the HeartSine Samaritan PAD is precision engineered to be one of the best AEDs on the market right now.

This fully automated AED can be operated by almost anyone, regardless of their level of first responder training.

The unit will assess the patient and deliver a shock automatically, as and when one is required. All that is required of the rescuer is to listen to the calm instructions given by the unit and follow them. If the verbal instructions are unclear (for example, if the rescuer is hard of hearing or does not possess English as their first language), the device also offers simple, easy-to-follow diagrams.

Adding to the device’s functionality, the buttons are large, clearly labelled and highly responsive.

For a unit as light as this one, you might be surprised to learn that it is quite durable.

With a water/dust ingress rating of IP56, the Samaritan PAD can survive challenging weather conditions if used outside. It only has a drop tolerance of 1metre, however. So, use it in the rain, but don’t drop it, essentially.

This model also includes HeartSine’s innovative ‘Pad-Pak’ (seriously you guys, that branding is so on-point) setup. Pad-Pak incorporates the battery and electrodes into one easily replaceable single-use cartridge, meaning that there is only one expiration date to monitor.

The HeartSine Samaritan PAD also boasts 90 minutes of available memory to record patient ECG readings and incident recording. This unit comes with an 8-year guarantee as well. 

HeartSine even make a version of this unit specifically for children younger than 8 or lighter than 25kg. Cannily titled the ‘Paediatric-Pak’ (again, that branding!), this version features a number of design innovations aimed at saving children’s lives – always a good thing.

Weight: 1.1kg

Dust/Water Resistance Rating: IP56 (Protected against powerful jets of water as well as basically water resistant, cannot be submerged)

Drop tolerance: 1m

Batteries: Pad-Pak Integrated lithium battery.

Suitable For: Novice level.


 ✅ Lightweight and well protected against water or dust ingress.

 ✅ Fully integrated battery and electrode pads, meaning that there is only one expiration date to monitor.

 ✅ Excellent guarantee.


 ❌ Fully automatic, which is good for amateurs, but not so good for professionals.

Mindray Beneheart C1A

The Mindray BeneHeart C1A Fully Automatic Defibrillator is an easy to use defibrillator that is suitable for home, office, and community settings.

It features ResQNavi technology which evaluates the proficiency level of rescuers and provides intelligent rescue navigation tailored to the user.

With pre-connected adult/child pads and a simple switch for changing between adult and child modes, the device will automatically adjust the CPR guidance.

The device also features 360J BTE (Biphasic Truncated Exponential) technology with auto-compensation for patient impedance.

This ensures defibrillation therapy is delivered according to AHA/ERC guidelines – 200J initially, then 300J for the second shock and 360J for the third.

The Mindray BeneHeart C1A also includes a language button that allows users to select from English and Mandarin, along with automatic daily self-test to ensure that the device is always ready for use.

The battery and pads are also rated to have a shelf life of up to 5 years, and the device is built to be extremely robust, with a 1.5m drop test certification and IP55 water/dust proofing.

Overall, the Mindray BeneHeart C1A Fully Automatic Defibrillator is an ideal choice for anyone looking for a simple but reliable defibrillator suitable for a variety of environments.

It is easy to use, with tailored rescue instructions based on users’ competence and quick shock delivery in less than 8 seconds, allowing responders to confidently treat Sudden Cardiac Arrest.

With its reliable performance and long-lasting battery life, the Mindray BeneHeart C1A is perfect for anyone looking for an effective and reliable defibrillator.

Weight: 2.3kg

Dust/Water Resistance Rating: IP55 water/dust proof

Drop tolerance: 1.5m drop tested

Batteries: Battery and pads have life cycle up to 5 years

Suitable For: Novice & Professional levels.


 ✅ Biphasic Truncated Exponential technology.

 ✅ battery and pads are also rated to have a shelf life of up to 5 years

 ✅ Language choice between English and Mandarin


 ❌ Has pre-connected Pad, not sure if you can disconnect them to change.

 ❌ One of the heavier of Defibrillators