Each year, 40 people are victims of cardiac arrest in France, with a survival rate in the absence of rapid treatment of only 000%. In places equipped with automatic external defibrillators (AEDs), this figure can be multiplied by 8 or 4. Since 5, everyone can and should use an AED, and more and more public places have it.

What is cardiac arrest?

A victim of cardiac arrest is unconscious, unresponsive, and no longer breathing (or breathing abnormally). In 45% of cases, cardiac arrest is due to ventricular fibrillation which manifests itself in rapid and anarchic beats. The heart can then no longer perform its pump function to send blood to organs, especially the brain. In 92% of cases, cardiac arrest is fatal if it is not taken care of very quickly.

The defibrillator, by delivering an electric shock to the fibrillating heart muscle, can resynchronize the heart cells so that the heart starts beating at a normal rate.

Composition of an automatic external defibrillator (AED)

An AED is a generator of electric current that operates independently. It contains :

• an electric block making it possible to deliver an electric current of calibrated duration, shape and intensity;
• two electrodes of wide and flat shape to deliver the electric shock to the victim;
• a first aid kit containing scissors, a razor, compresses.

Automatic external defibrillators are:

• or semi-automatic (DSA): they analyze cardiac activity and advise the user on what to do (administration of an electric shock or not);
• or fully automatic (DEA): they analyze the activity of the heart and deliver the electric shock themselves if necessary.

The function of an AED is to analyze the electrical activity of the heart muscle and decide whether or not it is necessary to administer an electric shock. The purpose of this electric shock is to restore normal activity in the heart muscle.

Cardiac defibrillation, or cardioversion

The defibrillator detects the cardiac arrhythmia and analyzes it: if it is a ventricular fibrillation, it will authorize an electric shock which will be calibrated in intensity and duration according to various parameters, in particular the average body resistance to the current. of the victim (its impedance).

The delivered electric shock is brief and of high intensity. Its purpose is to restore harmonious electrical activity in the heart. Defibrillation is also called cardioversion.

Public concerned or at risk

The defibrillator should only be used if the victim is unconscious and is not breathing (or very badly).

• If the victim is unconscious but is breathing normally, it is not a cardiac arrest: he must then be placed in the lateral safety position (PLS) and call for help;
• If the victim is conscious and complains of pain in the chest, whether or not radiating to the arms or head, with shortness of breath, sweating, excessive pallor, feeling nausea or vomiting, this is probably a heart attack. You have to reassure her and call for help.

The reactivity of witnesses to a cardiac arrest increases the chances of survival of victims. Every minute counts: one minute lost = 10% less chance of survival. It is therefore crucial toact quickly and do not panic.

When to use the defibrillator

Using a defibrillator is not the very first thing to do when you witness a cardiac arrest. Cardiac resuscitation must follow certain steps to be successful:

1. Call the emergency services on 15, 18 or 112;
2. Check whether the victim is breathing or not;
3. If she is not breathing, place her on a flat, hard surface and start cardiac massage: alternate 30 compressions and 2 breaths, at a rate of 100 to 120 compressions per minute;
4. At the same time, turn on the defibrillator and follow the instructions given by voice guidance, while continuing the cardiac massage;
5. Wait for help.

How to use a defibrillator?

The use of an automatic defibrillator is accessible to everyone since the instructions are given orally during the intervention. Simply let yourself be guided.

The first thing to do is to turn on the device, by pressing the on / off button or simply opening the cover. Then a voice guidance steers the user step by step.

For adults

1. Check that the victim is not lying down in contact with water or a conductive metal;
2. Strip his torso (cut off his clothes if necessary with the scissors from the first aid kit). The skin must not be damp or too hairy for the electrodes to adhere well (if necessary, use the razor from the first aid kit);
3. Take out the electrodes and connect them to the electrical block if not already done;
4. Place the electrodes as indicated on either side of the heart: one electrode under the right clavicle and the second under the left armpit (the electric current can thus pass through the heart muscle);
5. The defibrillator begins to analyze the victim’s heart rate. It is important not to touch the victim during the analysis so as not to distort the results. This analysis will be repeated every two minutes thereafter;
6. If the results of the analysis recommend it, an electric shock will be administered: either it is the user who triggers the shock (in the case of AEDs), or it is the defibrillator which administers it automatically (in the case of AEDs). In all cases, care must be taken to ensure that there is no one in contact with the victim at the time of the shock;
7. Do not unplug the defibrillator and wait for help;
8. If the victim has started to breathe regularly but is still unconscious, put her in PLS.

For children and infants

The procedure is the same as for adults. Some defibrillators have pads for children. Otherwise, use the adult electrodes by positioning them in an antero-posterior position: one in front in the middle of the chest, the other behind between the shoulder blades.

Criteria to consider when choosing an AED

• Favor a brand known in the first aid industry, CE certified (EU regulation 2017/745) and guaranteed by the manufacturer;
• Heartbeat detection threshold of 150 microvolts minimum;
• Presence of assistance for cardiac massage;
• Power of the shocks adapted to the impedance of the person: the first shock of 150 joules, the following shocks of higher intensity;
• Good quality power supply (battery, batteries);
• Automatic update according to ERC and AHA (American Heart Association) guidelines;
• Possibility of language selection (important in tourist areas).
• Protection index against dust and rain: IP 54 minimum.
• Cost of purchase and maintenance.

Where to install a defibrillator?

The automatic external defibrillator has been a class III medical device since 2020. It must be easily accessible in less than 5 minutes and be made visible by clear signage. Its existence and location must be known to all persons working in the establishment concerned.

Since 2020, all establishments receiving more than 300 people must be equipped with an AED, and by 2022, many other establishments will also be affected.