Washington ? You can be walking around normally when your heart suddenly stops beating. It takes a mere five seconds to lose consciousness. In 20 seconds, your brain shows it’s losing oxygen your eyes roll back and your arms and legs twitch. In 10 minutes, you’ll be dead.

This is sudden cardiac arrest, and there’s only one save: a defibrillator, a device that shocks the heart into beating again. Every minute spent waiting for one lowers the chance of survival by 10 percent.

Portable defibrillators in airplanes, shopping malls and casinos have saved lives. Now some doctors, survivors and defibrillator makers say it’s time for the easy-to-use machines to move into many homes, alongside such common safety devices as smoke alarms and fire extinguishers.

Other doctors argue that putting defibrillators in so many untrained hands could be risky. They envision a distraught spouse spending precious minutes hunting for the defibrillator instead of dialing 911 only to discover the machine’s battery is dead.

Dr. Arthur Kellerman of Emory University worries that owning a defibrillator might cause people to ignore less glamorous but proven heart protection: “Why give up my cheeseburgers? I’ve got old sparky under the couch.”

The American Heart Assn. says there’s no scientific evidence to tell whether at-home defibrillators are helpful or not the topic hasn’t been studied.

Yet already dozens of people who can afford the $3,500 price tag have gotten doctors to write them prescriptions for the devices.

“I have one in my home and my car, as a personal safety thing,” says Dr. Gust Bardy of the University of Washington. Hoping to widen the market, manufacturer Philips Medical Systems plans to seek Food and Drug Administration approval this spring of a defibrillator specifically designed for at-home use. The device, slightly smaller than those available now, would sell for about $2,300.

Manufacturers are even asking what the FDA would require to sell defibrillators in drugstores without a doctor’s prescription.

Every year, about 220,000 Americans collapse and die of cardiac arrest. This is not a heart attack, it’s worse: Without warning, the electrical signals that pump the heart go haywire and heartbeat stops. CPR buys crucial time by getting oxygen to the victim’s brain while help is summoned. But only a defibrillator can restart the heart.

It requires no special medical expertise, and step-by-step instructions are provided. The machine isn’t supposed to shock if it detects a heartbeat.

Paramedics have long carried defibrillators. Backed by studies, such as one that found defibrillators on board American Airlines saved six of 15 cardiac-arrest victims, they’re increasingly found in police cars, office buildings, airports, casinos and shopping malls.

The home is the next frontier. Proponents say that’s where most cardiac arrests happen.

Studies of laymen’s use of defibrillators in public buildings are mixed on whether they increase survival rates significantly more than performing CPR until paramedics arrive.

The National Institutes of Health has begun a major study in 1,000 apartment buildings, health clubs, skyscrapers and other buildings. It doesn’t address at-home use specifically study participants are unlikely to be treated by a loved one but it should shed some light on ways to ensure defibrillators are used effectively.