Peter Weissberg: Defibrillators - A cheap and easy way of keeping people alive

The main reason for wanting defibrillators in public places is because, when someone has a heart attack, within the first seconds there is a risk they can go into cardiac arrest - their heart stops.

For each minute that passes when someone is in cardiac arrest, their chance of survival drops by 14 per cent. But if someone is able to resuscitate them with a defibrillator, and they then go to hospital, their outlook is no worse than someone who did not have a cardiac arrest. If nobody is about who knows what to do and there is no defibrillator, then they die. So it is a relatively cheap and easy way of keeping people alive.

The equipment is very easy to use after a small amount of training, but ideally you also need people with emergency life-support skills to help when someone does go into cardiac arrest.

However, there is no point in having a defibrillator if someone locks it away in a cupboard and nobody is trained how to use it.

The most obvious places to put the equipment are where you have high "foot fall" - places where lots of people go and also the kind of people most likely to have a heart attack, such as the middle-aged and elderly people. This means railway stations, shopping centres and some sports centres.

These machines have helped save lives and we have helped put thousands in public places for this reason. There are people alive today who would not be here had a defibrillator not been available when they needed it.

• Professor Peter Weisberg is medical director of the British Heart Foundation.