It's common sense that the faster an ambulance arrives at an emergency the better the patient's chance of survival

Belinda Linden, British Heart Foundation

The current target set for the ambulance service in the UK is to respond to 90% of calls within 14 minutes.

Half of all emergency calls have to be attended within seven minutes.

But a spokesman for the Scottish Ambulance Service said many more ambulances would be needed to meet the five minute target.

Survival rates

Using models, the researchers looked at how swifter response times would affect survival rates.

They found if the target time was cut from 14 to eight minutes, as recommended in the National Service Framework on cardiac care for England and Wales, survival rates could be increased to 8%.

Defibrillators - 'wider access could save more lives'

But they found that if ambulances responded to 90% calls within five minutes, about 11% of cardiac arrest victims would survive.

In the paper, published in the British Medical Journal, the researchers led by Professor Stuart Cobbe of the University of Glasgow, wrote: "Reducing response times would inevitably require additional resources."

But they say equipping all "first responders" with defibrillators would mean response times would be speeded up and the additional costs cut.

They added: "Our figures for improvement in survival from reduced response times should be considered as minimum estimates.

"A general improvement in response times would result in more people with chest pain being reached by a first responder with a defibrillator before the onset of cardiac arrest. Our data show that survival in such cases is 33%."

Professor Cobbe told BBC News Online: "The first thing you need if you have had a heart attack is somebody with a defibrillator, but that does not necessarily need to be a paramedic."

They point out survival of heart attacks which happen outside hospital are three times lower in the UK than in other countries.

Prioritising

A spokesman for the Scottish Ambulance Service told BBC News Online: "There's no doubt that to achieve a response in Scotland of five minutes, particularly in urban areas, you would need an ambulance on every street corner."

On the proposal to equip other emergency services with defibrillation equipment, he said: "People who have cardiac arrests are the very people that need paramedics, with their knowledge and experience, to attend quickly."

He said proposals had been submitted to the Scottish Executive to prioritise calls, as happens in the rest of the UK.

Where calls are prioritised, the most serious cases, such as heart attacks would be seen more quickly, though those which are less serious may have to wait for longer than they do under the current system.

Currently, the Scottish service responds as quickly as possible to all calls. Last year the average response time was nine minutes.

Of the 500,000 calls the Scottish Ambulance Service receives each year, around 2,000 are for cardiac arrests.

Belinda Linden, head of medical information at the British Heart Foundation, which funded the research, said: "It's common sense that the faster an ambulance arrives at an emergency the better the patient's chance of survival.

"Often the problem is not a lack of ambulances but traffic conditions on the day."

She added that the BHF provided defibrillators to other first responders such as the police and local GPs as a way of increasing the chance of early defibrillation.