What is an AED? Our Guide to Defibrillators

We need to start somewhere, so we'll begin with a definition of what an AED, or Automated External Defibrillator is.

Defibrillator Definition

"a machine that uses an electric current to stop any irregular and dangerous activity of the heart's muscles"

In practice an Automated External Defibrillator, or AED is a portable medical device that can deliver a controlled electric shock to a patient who has gone into cardiac arrest. It can be either semi automatic, whereby the user has to push a button to activate the shock. Or it can be fully automatic, where the machine generates the shock automatically.

An AED consists of two main elements. The first is a 'control box', which in simple terms contains a microprocessor, electrical circuitry and a long-life battery. The second is a pair of defibrillator pads (or electrodes), which attach to the patient. They collect heart rhythm information from the patient and pass it to the control box. Then if required, the control box delivers a shock to the patient's heart.

Defibrillators are the magic boxes that deliver a controlled electric shock that helps to get a heart that has gone into an irregular lethal rhythm back into a normal one.

So how do they work? To understand that, you first need to know a little about the human heart:

The Human Heart – The Basics:

The heart is a 4-chambered pump with its own electrical system which fires off electrical impulses from the primary pacemaker. 

To put that in context, in the UK, fewer than 2% of patients are treated with a defibrillator before the ambulance service arrives.

How AEDs Work and how to use them

Once the AED has arrived,  the defibrillator pads need to be placed correctly by the operator / bystander. Correct pad placement is important; there is a diagram on each pad showing where to put them.

The first goes on the right side of the chest (with the casualty on their back), just below the collar bone.

The second goes on the left side of the chest, just below the breast area or below. Once the pads are placed correctly and it's switched on, the defib first analyses readings from the patient's heart.

As we said, they're really, really easy to use. All portable defibs include a speaker which tells the user at every stage exactly what it's doing, and instructs them when they need to intervene, and what they should do. Many models also include a video or text screen which also give the same instructions.

In both cases, the defib will then immediately instruct the bystander to commence (or continue) CPR, and will subsequently analyse and shock again, if required.

This CPR and AED process is continued either until skilled help arrives or until the patient wakes up and is breathing and moving normally.

Should you get a defib for your workplace?

Well, if in doubt the answer is probably 'yes'. And I'm not necessarily talking from a legal point of view, as most organisations are not, at the time of writing, legally required to have one.

But it's worth considering that sudden cardiac arrest is a leading cause of death and that you do have a responsibility for ensuring safety to your staff, visitors and customers. You may consider that the risk of needing one is so low that buying one is unnecessary. But that would be missing the point. After all, you invest in fire extinguishers and in business, car and home insurance and hope you will never need to use any of those either!

Of course there's no point in having a workplace defib if your staff can't access it, or don't know where it is. We've seen cases of them being locked away in cupboards, with keys held by part-time staff. Or more commonly, locked in the office of someone who works office hours, and so not available to warehouse staff who work shifts.

What about all those staff who don't even know you have one? Or those who've heard a rumour that you have one, but don't know where it is?

As part of our first aid courses, we ask staff to bring out their defib. Sometimes, there are blank looks, with some minutes of hunting around, followed by a sheepish looking staff member bringing out their defib, still in its original box and covered in dust!

By this time, in a real emergency, it would already be too late to use it!

Out-of-hospital defibrillators are specifically designed to be used by untrained staff as well as trained first aiders. They provide help to the user, including clear imagery (both on the device and the pads), verbal instructions and semi or automatic operation.

They also won't shock unless a shock is required, so you can't cause an injury by using one.

So in theory, you don't need to be trained before you use a defribrillator. And if you find yourself needing to use one to help save someone's life, you should do so, rather than holding back from lack of training.

But if you are unsure about having untrained staff using a defib, you'll be happy that almost all first aid courses include instruction in defibs.

All of our practical first aid courses, from the most basic to the most advanced, include instruction, demonstration and hands-on practise in the use of defibs. So at the end of any of those courses, everyone should be confident to use one.

If you're looking for formal workplace first aiders, you should be looking at the Emergency First Aid or First Aid at Work courses. During both courses you'll be assessed in your use of an AED, as well as being taught a whole range of other first aid skills

If you already have enough workplace first aiders, a basic first aid or AED course may be suitable for you. This teaches fewer skills, but can be used to inform those who don't want to be first aiders, but would still benefit from learning these key skills.

In either case, your staff will learn to use a defib in context of a simulated medical emergency, designed to help them to react swiftly and correctly in the event of a real emergency situation.

You'll be pleased to hear that defibrillators are designed to be very low maintenance devices. However, there are a few regular checks you should carry out. Your first port of call for this information is the manual which came with your defib, so please READ THAT FIRST!

Please note that each make of defibrillator is slightly difference, so all of the below information is generalised.

There are a few consumables which need replacing periodically:

Replacing Batteries

Like any other device, defib batteries have a limited useful life. This is usually between 3 and 5 years. Check in the manual, and make sure you record when the battery is due for replacement.

SCHEDULE the purchase of the replacement, well in advance of its expiry date. It's no good recording that it needs replacing, if no-one gets a reminder when it's due.

If the defib is used, the batteries may need replacing earlier.

Replacing Pads

Defib pads also need changing, usually every 2 to 3 years, even if they've not been used. They're also single use, so if they have been used, replace them immediately. Better still, always keep a spare set (but bear in mind they'll go out of date too).

Depending on the model of your AED, you may require junior pads as well as adult ones. If so, keep a spare set of those too, if you're likely to need to care for children.

Other Maintenance

Many devices have in-built self-test modes which will activate when the defib is switched on. If yours is one of those, it's worth scheduling regular 'switch-ons' so that the machine can check battery levels and other operations.

They may also have battery condition lights, which will indicate how much charge remains in your unit. Replace your battery on if your unit shows low condition or if the battery is out of date (whichever is the earlier). 

Servicing Companies

There are companies who charge to service AEDS. They can either be related to the manufacturer, the vendor or be completely independent of either. It's up to you whether you purchase this 'insurance service' or not. Again, we'd suggest taking advice from your owner's manual.

Over the last few years we've been delighted to see the number of Public Access Defibrillators (PADs)  on the increase. They are appearing outside many more shops, libraries and community centres as well as in schools.

Often, but not exclusively, recognised by the bright yellow cabinets they are housed in, they are a welcome sight. How many people though are aware that they are for the use of the general public and that anyone can access them?

The cabinets are typically locked (to combat vandalism), and have instructions on the front telling the user which number to call to unlock the cabinet and access the defib. They're then used in the same way as the machine in your workplace.

As we know, rapid access to defibrillation dramatically increases the chances of surviving a cardiac arrest. So it's really important that public access devices are registered with the local ambulance service to enable emergency call handlers to direct rescuers to the nearest AED.

You also have the option to register your office device too, and by doing so, you'll be contributing to the ever-expanding pool of defibs available for the public to use.

There are plenty of options if you're buying a defibrillator for your workplace. Apart from minor differences, each model has the same function. It's often best to find out which model your local ambulance service is currently recommending, but you can base your decision on price or add-in functions, or on cost of consumables.

Please note that none of these are a specific recommendation, and we neither sell nor take commission from any AED suppliers or manufacturers.

The main brands, along with links to the manufacturers are:

In addition to AEDs, there are also several similar medical devices which you may have heard about, which have similar functions, but are distinctly different from the AEDs that we use as first aiders. To help you understand the differences, here are some quick details on those other machines.

Manual defibrillator

Manual defibrillators are typically the larger, more advanced devices used by professional medical responders. They often include screens and printers which provide heart traces, and have full paddles rather than pads.

Implantable cardioverter defibrillator

An ICD is a medical device that's planted in the chest, under the skin, to monitor your heart rhythm. It can deliver electric shocks directly to the heart if it detects the appropriate conditions.

Pacemaker

A pacemaker is a device similar to an ICD. However a pacemaker sends out a regular electrical signal if it detects a fast or irregular heartbeat, and therefore does more of a heart regulation than heart shocking function.