Paramedics faced with a patient having a heart attack would normally reach for a defibrillator, a machine which can shock the heart into beating again.

Hundreds of Sussex victims have been successfully resuscitated and lives saved using defibrillation.

But from Monday, paramedics and technicians working in Brighton and Mid Sussex will instead start the resuscitation procedure using chest compression.

They will be the first in the UK to do so and every other ambulance trust in the country will be watching the pilot scheme closely.

Two cities in the USA and Norway switched procedures some years ago and recorded startling increases in survival rates.

The change is based on what happens when a cardiac arrest strikes.

The heart's left ventricle - the pumping chamber - quickly shrinks and empties of blood, while the right chamber fills and swells with blood.

Employing hand compression to the chest first can squeeze blood from the right chamber to the pumping chamber.

When this is followed with defibrillation, blood is successfully pumped round the body. The patient stands a much higher chance of survival.

Seattle, USA, was the first city to employ the new technique.

It already enjoyed one of the best resuscitation records in the world - defibrillators are housed at strategic points, many members of the public are trained to use them and paramedics hope to reach heart attack victims within two minutes, far quicker than anywhere else in the world.

But in 1998, Seattle switched procedures and used chest compression first.

Health chiefs were surprised by the vastly improved survival rates.

They reached 27 per cent compared with 17 per cent the previous year.

Colleagues in the Norwegian capital, Oslo, followed suit and their stunning results were reported last year.

They saw their survival rate leap from four per cent to 22 per cent.

One of the driving forces behind the change in Sussex is Brighton-based Professor Douglas Chamberlain, an internationally recognised expert in pre-hospital emergency care.

He said: "There has always been the concept of quick defibrillation because after four to five minutes following collapse the chances of success are reduced.

"That has been the dogma for years so when Seattle decided to opt for chest compression first, the world thought it a little strange and was taken aback when the improved survival rates were published in 1998.

"The concept is now being taken far more seriously and some parts of the USA have gone over to the new procedure.

"We decided to try it first in Brighton and Mid Sussex and we will report back to other ambulance trusts."

Dr David Janes, medical director for Sussex Ambulance Service, said: "Sussex has long been recognised as a national pioneer in resuscitation.

"I am delighted Sussex Ambulance Service is involved in such an exciting project that has potential benefits for many patients.

"We are extremely fortunate to have the support and expertise of Prof Chamberlain, who has helped put this study together."

The pilot project also has the support of the Sussex Ambulance Trust's patient and public involvement forum.

Ultimately, it may become a major national trial.