How Does A Defibrillator Work?

You may have often wondered to yourself, "How does a defibrillator work?" Of course, you probably know the basics. It has, after all, been played out in movies more times than most of us care to remember.

“There’s no pulse,” someone cries. A shirt is ripped open; two paddles press down upon a patient’s chest and a machine whirs into action.

A call goes out, “Clear!”

The prone figure jerks as a jolt of electricity passes through their heart.

So, How Does A Defibrillator Work?

Still, having asked the question "How does, a defibrillator work?" you might expect a complicated answer. In reality, there’s not that much to it. Put simply; a defibrillator works by sending an electric shock of around 200- 300 volts through a patient’s heart to shock it back into working order.

Studies suggest that immediate defibrillation, even when used by an untrained bystander, increases survival rates from 31 to 45 percent.

How Easy Are They To Use?

The defibrillators you find in hospitals and ambulances require a trained medical practitioner to operate them. That means that any unit you are likely to come across is going to be an AED, and the good news is that these particular units require no training to operate.

That’s because AEDs speak to their operator, literally talking them through the procedure. Diagrams and in some cases LED panels also help to make the process as user-friendly as possible.

The critical thing to remember is that a defibrillator’s job is to shock a heart back into working order. For that reason, an AED finds use only in those cases where a patient’s heart has stopped beating. In medical terms, the person is said to have gone into cardiac arrest.

What Exactly Is Cardiac Arrest?

In pathology, fibrillation refers to irregular or uncoordinated contraction of the heart muscle. Called arrhythmia, this stems from a problem with the heart’s electrical signals. As the heart spasms, it ceases to pump blood around the body. The patient goes into cardiac arrest and falls unconscious

It is for this reason that the short sharp shock of a defibrillator is effective. It provides just enough electrical energy to jump-start a heart back into its normal rhythm. Without immediate medical attention, death is near-certain.

Heart Attack

A heart attack is not the same thing as a cardiac arrest, although the one may lead to the other. A heart attack occurs when blood flow to part of the heart is blocked. If left untreated, the affected area begins to die

Heart attacks increase the likeliness of a sudden cardiac arrest and indeed when sudden cardiac arrest occurs, a heart attack is generally to blame. Still, other conditions that lead to cardiac arrest include electrical shock, heart disease, heart failure, ventricular fibrillation, and conduction disorders.

Who Can Use A Defibrillator?

Again, any defibrillator you have close to hand during a medical emergency is most likely an AED, so the short answer is that anyone can use one. There are training units available for purchase, allowing you to practice the procedure, but these are NOT life-saving devices and are designed solely for educational purposes.

Who Should I Use It On?

A person should be both unresponsive AND not breathing before anyone uses a defibrillator on them. You can confirm that he or she is unresponsive by shouting at them or giving them a shake.

Remember, a cardiac arrest in an electrical problem. The person WILL be unconscious. In most cases, they won’t be breathing or at best, not breathing normally. You will be unable to rouse them.

A heart attack, on the other hand, is a circulation problem. A patient undergoing a heart attack is probably going to be in distress, but conscious.

Pediatric Care

If the patient is under eight years of age or weighs less than 55lbs, use pediatric pads instead of the adult ones; they are designed to deliver less energy to the heart. Clear labeling distinguishes them from the main set.

Do not, however, delay treatment to ascertain exact age or weight.

A Real-World Lifesaver

women holding a floater

Image Source : flickr

The modern-day defibrillator bears little resemblance to the clunky, car battery-powered prototype Belfast-born Frank Pantridge invented back in 1965. Medical professionals recognized the life-saving potential of the device immediately. They improved the design.

Portable defibrillators became a mainstay of paramedic care almost from the get-go. Today, Automated External Defribulators (AEDs) find use in offices, homes, and public spaces up and down the country. Indeed, bystanders using a defibrillator save an estimated 1,700 lives in the U.S every year.

Training Manual

But bystanders are not doctors and nor for that matter are we. An article entitled “How does a defibrillator work?” can only do so much. You should always seek proper training and certification from appropriate providers before using any equipment. This is especially true of manual defibrillators, like the kind found in hospitals.

The AED however, is an exception to this rule. Designed for use by the untrained, in a life or death situation, they are as close to fool-proof as technology can get.

The Five Steps Of Using An AED

The complete answer to the question “How does, a defibrillator work?” distills down into five, easy-to-follow steps -- if you're discussing an AED.

Remember, instructions come via audible form, meaning that the unit is literally going to talk you through the procedure. Diagrams or as is increasingly commonplace an LED panel also helps to guide you through the process.

Step 1: Assess, 911, CPR


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If you suspect that someone has gone into cardiac arrest, the absolute first thing you need to do is call 911.

The second thing you need to do is begin CPR.


If you don’t know how to perform CPR, it might be a good idea to learn how. There are a wealth of blogs, self-help books, and courses available for those interested in learning more.

CPR is an essential aspect of the “How does, a defibrillator work?” question. The one-sentence answer on how to perform it is as follows:

“Give thirty chest compressions then give two rescue breaths if you are trained - if not, just carry on giving chest compressions”.

CPR stands for cardiopulmonary resuscitation and is, in fact, a combination of techniques. CPR aims to pump the heart so that blood can circulate and deliver oxygen to the brain. But CPR is unlikely to restart the heart. It is only a stop-gap measure until a definitive way of getting the heart started again becomes available.

In many cases, that means continuing CPR until 911 responders arrive, but if you have access to a defibrillator, then you can move on to step two.

Step 2: Prep


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As you might expect of an item designed for use in emergency medical situations, an AED requires little in the way of set up. First, lift the cover. Next, remove clothing from the patient’s chest area.

If the patient’s chest is wet, dry it before proceeding. Take the pads out of the case and tear off any packaging before placing them on the chest.

Step 3: Place Pads

pads and band aids

Image Source : Flickr

Since the goal here is to send the shock through the person’s heart, the correct placement of the pads is of vital importance.

Place one pad sticky-side down on the patient’s bare chest just above the right nipple. Place the second one on the left side of the chest below the left breast area. In some cases, the pads might be color coded to avoid confusion, but at any rate, the AED is going to offer pointers by way of audible commands and diagrams.

In the case of a child patient, remember to use the pediatric pads, affixing one on the back chest wall and the other on the left side of the front chest wall.

Step 4: Analysis

Often, diagnosis is the scary side of the “How does, a defibrillator work?” question. Fear of injuring a patient often causes people to hesitate at a moment where time is at a premium.

In practice, however, as soon as the pads are attached, the AED unit is going to take over.

It automatically analyzes the patient’s rhythm to assess their condition. It will inform you that this is what it is doing and ask you to step back. This is because the machine is sensitive, so it’s important not to touch the patient during this part of the procedure. The unit is then going to arrive at one of two conclusions.

If it detects a shockable rhythm, it will tell you so, charge the pads, and ask you to stand clear.

If the rhythm changes to a non-shockable rhythm, the AED will override the charge, advise you of the reason and prompt you to perform CPR.

Otherwise, a button on the AED will begin to flash. Pushing it delivers the shock. You will then be asked to administer CPR once again.

Step 5: CPR

dummy cpr

Image Source : Pixabay

Thirty compressions followed by two breaths. At the end of one set of CPR, the AED voice prompt might ask you to repeat steps four and five if required.

Manual Override

Most AED’s have a manual overdrive switch which allows a trained operator to perform a shock even if the analysis protocol concludes that the detected rhythm is non-shockable.

Switching to manual override mode means that the rescuer is taking full responsibility for the patient’s life. As such, use of the manual override is not advised for anyone other than qualified medical practitioners.

Commercially Available Defibrillators


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Again, the only defibrillator that is safe to use by people lacking specialist training is an AED.

As a consequence, such units are the only type of defibrillator you are likely to find in public places. If you intend to install one of these life-saving devices in your home or office, then an AED is the way to go.

While Amazon stocks all manner of AED accessories such as cabinets, and face shields for the actual AED, you are best going to a specialist retailer.

Market-leader AED provides an all-in-one solution for most of your defibrillator needs. They offer packages for schools, businesses, and manual defibrillators for first responders. They also stock a variety of accessories, replacement parts, as well as a plethora of training solutions.

Shock Tactics

And that as they say, is that. The AED does most of the work for you.

The steps remain relatively straight forward. Even a misdiagnosis is unlikely. After all, the AED scans the patient searching for signs of ventricular fibrillation, and if it does not find what it’s looking for, it automatically cancels the shock.

As long as you steer clear of any manual override, the chances of harming a patient are effectively zero. And the possibility that you might save someone’s life?

Pretty darn good, all things considered.

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