It shows people who collapsed suddenly with cardiac arrest had a 50% higher chance of surviving with heart massage alone rather than alternating with breathing into their lungs.

There were several reasons why chest compressions might work better than traditional cardiopulmonary resuscitation (CPR), said the study leader, Ken Nagao.

Interrupting chest compression to perform mouthto-mouth ventilation might do more harm than good if blood flow to the heart was not properly re-established, he said. As well, many people were too squeamish to lock lips with a stranger, whereas more might be prepared to attempt hands-only resuscitation.

"This reluctance is partly caused by fear of transmission of infectious diseases, " Dr Nagao wrote in The Lancet.

"Another barrier to bystanders attempting CPR is the complexity of the technique as presently taught."

Dr Nagao and colleagues studied the medical histories of 4,068 people who collapsed with a heart attack while someone else was present.

Nearly three-quarters received no resuscitation at all, but of the others, those who were given heart compressions alone were 50% more likely to be alive without brain damage a month later.

Nevertheless, only a small proportion survived - 6% in the heart-only group versus 4% of those who also received the kiss of life. The results apply only to cardiac arrest and not to drowning, the other main use of mouth-tomouth resuscitation.