A defibrillator is designed to restore the natural heart rhythm when someone has life-threatening arrhythmias. To do this, the device delivers surges via electrodes on the affected person's chest. In First Aid, so-called automated external defibrillators (AED) are used. They are designed so that they can also serve a layman. Find out when and how a defibrillator should be used and what to consider when defibrillating.

Article overview defibrillator

  • Quick Overview
  • How does a defibrillator work?
  • When do I use a defibrillator?
  • Risks when using a defibrillator

Quick Overview

  • What is a defibrillator? A device that delivers surges via electrodes to bring a disturbed heart rhythm (such as ventricular fibrillation) back into natural rhythm.
  • Using the defibrillator: Stick electrodes according to the instructions, then follow the (language) instructions of the device.
  • In which cases? As an emergency measure for life-threatening cardiac arrhythmias (such as ventricular flutter).
  • risks: Danger for first responders and those affected by current flow in combination with (much) water. Scorching of the chest hair, if this is very dense.


  • During defibrillation, follow the voice instructions or written / graphical instructions of the device (AED). Then, as a layman, you can not go wrong in principle.
  • If there is a second first responder on site next to you, one will pick up the defibrillator and the other one will start manual resuscitation (resuscitation). If you are alone, you must start the cardiac pressure massage immediately. If someone else comes along, ask them to look for a defibrillator.
  • Do not use the defibrillator in water or in a puddle.
  • Do not attach defibrillator pads directly above a pacemaker (often recognizable by a scar or the like in the chest area) or another medical implant. The electrical pulse can be affected at such locations.
  • Do not touch the patient while the device is analyzing the patient's heart rhythm or delivering surges. The device will prompt you accordingly.

Legally, nothing can happen to a layperson using a publicly available first aid defibrillator. According to §34 of the Penal Code, this act falls within the scope of the "justifying emergency" and occurs within the scope of the suspected consent of the person concerned.

To the table of contents

How does a defibrillator work?

You can see them in companies, public buildings and subway stations: small defibrillator cases on the wall. They are characterized by a green shield with a heart on which a green flash twitches. These automated external defibrillators (AEDs) are a little reminiscent of a first-aid kit with two cables, each with an electrode pad the size of a postcard. These electrodes are stuck to the chest when the heart gets threateningly out of rhythm. Over the electrodes, the device then sets off small surges to bring the heart back to its natural beat rhythm.

Fully and semi-automatic defibrillators

There are fully and semi-automatic defibrillators. The former release the current impulse automatically. The semi-automatic devices on the other hand require the first responder to trigger the impulse manually by pressing a button. In Germany, mostly semi-automatic defibrillators are in use.

Use defibrillator: That's how it works!

An AED ("lay defibrillator") is designed so that it can be safely and accurately used by lay people: on the electrode pads show pictures how and where the pads are to be attached. By voice function, the device announces the next steps and their order. Depending on the model, there is also an image-based guidance via screen or drawings.

Specifically, follow the defibrillation procedure as follows:

  1. Release the upper body of the patient: A defibrillator can only be applied to the naked skin. The skin should be dry and hair-free. This is necessary so that the defibrillator can work efficiently and the patient does not suffer from burns due to a spark. Therefore, if necessary, dry off the skin on the upper part of the body and shave with strong chest hair. For this purpose, the emergency kit usually comes with a razor. But hurry up with the shaving!
  2. Attach the electrode pads: Follow the instructions - one is placed under the left armpit, the other on the right below the clavicle.
  3. Do not touch the patient during the analysis: The defibrillator analyzes the patient's heart rhythm to determine if it is defibrillatable or not (see below). No one should touch the patient during the analysis.
  4. Then follow the instructions given by the deviceIf it is a semi-automatic AED, it will prompt you in the case of VF / Chamber Flutter to press the so-called shock button. This triggers a surge. You will recognize the button by the lightning symbol. Caution: During the surge, neither you nor anyone else may touch the patient!
  5. Continue to follow the defibrillator instructionsFor example, he may ask you to resume the cardiac pressure massage that was performed before defibrillation.

Defibrillator: Special features when used on children

For children younger than eight years or weighing less than 25 kilograms, not all defibrillators are suitable - the surge would be too violent. Some devices have a device (such as sliders, child keys) to reduce energy delivery. Other defibrillators even detect if they are a child, for example if the enclosed, smaller pads are placed on top. They then automatically regulate the defibrillation energy down.

In an emergency, however, it is better to use the Adult Defibrillator than to give the chance to save the child's life.

To the table of contents

When do I use a defibrillator?

An Automated External Defibrillator (AED) is used when an unconscious person needs to be resuscitated because his heart is beating rhythmically or not at all. The defibrillator independently analyzes whether a current surge is necessary or sensible at all. There are two types of heart rhythms:

  • defibrillatable rhythm: The electrical signals in the heart muscle are not properly forwarded. This can be manifested in cardiac arrhythmia (ventricular fibrillation, ventricular flutter, pulseless ventricular tachycardia / pVT). This out of rhythm rhythm can be corrected by defibrillation. In this case, the device would trigger a shock (fully automatic defibrillator) or prompt the first responder to press the corresponding button (semi-automatic defibrillator).
  • non-shockable rhythm: This is the case in two cases: Either the electrical (and mechanical) cardiac reaction has been suspended (cardiac arrest) or electrical cardiac activity is present, but it is not converted into mechanical reactions (ie contractions) (pulseless electrical activity / PEA). In both cases, a defibrillator can not do anything. He recognizes this during the analysis and will then ask the first responder to continue the chest compressions.

Defibrillation as part of resuscitation

The use of a defibrillator is one of the basic measures of resuscitation (basic life support, bls). So a revival should proceed as follows:

  1. The first thing you should do is Call the emergency doctor or ask a bystander for it.
  2. Begin with the cardiac pressure massage right away, preferably in combination with mouth-to-mouth resuscitation (if you or someone in the know trusts them). The frequency is the 30: 2 rule, ie 30 times cardiac massage and 2 breaths alternately.
  3. If another first responder is present, he should now get a defibrillator (if one is available). Apply the device as described above.

All of these measures are designed to ensure that the patient continues to draw blood to the brain and heart until the rescue service arrives.

Start resuscitation as soon as possible - just a few minutes without oxygen can cause irreparable brain damage or death!

Defibrillator for the home - useful or unnecessary?

According to the German Heart Foundation, it is completely unclear whether a defibrillator makes sense at home. For example, if an in-house defibrillator is available, someone may delay the emergency call or delay manual resuscitation (heart pressure massage and breath). The Heart Foundation therefore does not recommend the purchase of a defibrillator for home. But she advises anyone who still wants to buy one, before consulting the purchase of a heart specialist (cardiologist) to get advice.

To the table of contents

Risks when using a defibrillator

Sticking the pads directly to a pacemaker or other implanted device (often seen on a scar or the like in the chest area) may affect the current pulses.

If you use the defibrillator on an unconscious person lying in the water, you may be electrocuted! The same applies if you stand in a puddle when using the device. In contrast, it is no problem to use a defibrillator in the rain or at the pool edge.

You also get an electric shock when you touch the patient while the device is giving off a current pulse. The danger is especially with fully automatic defibrillators, which trigger the energy pulses independently. Therefore follow exactly the instructions of the device!

The electrodes must lie flat on the naked breast of the unconscious. If the pads wrinkle, the current can not flow. The function of the defibrillator is then limited.

Hurry up shaving in patients with heavy chest hair. If too much time passes before the defibrillator is used, it may be too late for the patient!