Portable defibrillators can double the survival rate for people who have collapsed from cardiac arrest, according to a massive North American study reported by Reuters.

If the ten-pound defibrillators became widely available in health clubs, shopping malls and other public places, "approximately 2,000 to 4,000 additional lives would be saved each year in the United States," said the research team, led by Alfred Hallstrom of the University of Washington in Seattle.

The newest devices use spoken commands and are simple enough for a sixth grader to use with minimal training.