Unresponsive person: check response, check breathing, get an AED

In cardiac arrest the heart stops pumping effectively. Sometimes it only quivers in an uncoordinated way instead of contracting strongly. The blood stands still, and the brain and organs no longer receive oxygen. The person collapses, does not respond and no longer breathes normally.

Chest compressions take over part of the heart's work. When you press on the centre of the chest, blood is squeezed out of the heart and the large vessels; when you release, new blood flows in. This creates an emergency circulation that supplies the brain with some oxygen until the ambulance arrives. It does not replace the heart, but it buys valuable time.

The AED can do something your hands cannot. Through adhesive pads it measures the heart rhythm and recognises certain rhythm disturbances that can be ended with an electric shock. Only then does it call for a shock – the device decides this itself, not you. Chest compressions and the AED work best together, and the earlier, the better.

The hardest moment is often recognising the problem. Many people believe a person is still breathing because they make occasional gasping or rattling sounds. This gasping can occur in the first minutes of cardiac arrest – it is not normal breathing. Normal breathing is calm and regular, and the chest rises and falls. When in doubt, act as if the person is not breathing and tell the dispatcher so.

Do not take too long to check breathing – no more than about ten seconds. Searching for a pulse for a long time only wastes valuable time. Before checking breathing, gently tilt the head back and lift the chin. This matters because in an unconscious person the tongue can fall back and block the airway.

Then comes the emergency call, on speaker, and someone fetches the AED. If you are alone, call first. The dispatcher tells you what to do and stays on the line. If you have learned rescue breaths on a course and are willing, combine them with compressions as practised there. If you cannot or do not want to, simply follow the dispatcher's instructions.

Many people do not dare to use a defibrillator because they think it is a device for doctors. Public AEDs, however, are built precisely for lay people. Once switched on, they announce step by step what to do and usually show pictures, for example where the adhesive pads go.

While the device is analysing the heart rhythm and while a shock is being delivered, nobody may touch the person. The device announces this, and you make sure everyone stands back. You only interrupt chest compressions when the AED tells you to, and you resume them as the device instructs.

Resuscitation only ends when the ambulance crew takes over, the person clearly breathes normally again or you are physically exhausted. If several helpers are present, swap regularly, because compressions are very tiring. If the person breathes normally again but does not respond, they go into the recovery position – and you keep checking their breathing.

Before you go to the person, check that you can do so safely – traffic, electricity, gas or fire come first. For children and infants the procedure differs in detail. Here especially: call the emergency number and follow the dispatcher's instructions exactly. Paediatric first-aid courses practise these differences.

This text deliberately gives no figures for compression depth, speed or the ratio of compressions to breaths. You learn these details on a course with a practice manikin, and over the phone the dispatcher gives them to you. Guidelines are revised regularly; the current version, as taught on courses, always applies.

Resuscitation is a great physical and emotional burden, whatever the outcome. Many helpers remain shaken for a long time afterwards. That is a normal reaction to an extraordinary experience. Talk to people you trust, to course instructors or to professionals – you do not have to carry it alone.

Resuscitation is a practical skill like riding a bike: you only really understand it once you have done it yourself. On a first-aid course you press on a practice manikin, get feedback from the instructor and practise with a training device that talks like an AED but delivers no electricity.

Refresh your knowledge regularly – practical skills fade faster than you think. Also remember where an AED is located in your daily life: at work, at the sports club, at the station. If you are unsure where the nearest one is, ask the dispatcher in an emergency.

The most important thought for a real emergency: without help, a person in cardiac arrest has hardly any chance. Not starting at all for fear of mistakes is the biggest mistake. Everyone who calls the emergency number and helps as instructed gives them a chance.