If someone collapsed and stopped breathing, would you know what to do, beyond calling for help?

Researchers and designers at the University of Pennsylvania worry not enough people know of a simple, effective technique or where to find a defibrillator in a public place.

"It's a lifesaving device which can shock the heart and restart it when the heart stops," says Dr. Raina Merchant, while demonstrating how to use an automated external defibrillator, or AED, inside Philadelphia's 30th Street Station.

The device comes in a small zipper pouch. An automated voice offers step-by-step instructions for what to do.

Merchant, an emergency physician at Penn who's been mapping where AEDs are located around the city, says using one, along with CPR, can increase a person's chance of survival from less than two percent to more than 50 percent.

Problem is, AED's are often hidden in plain sight.

"I haven't noticed any in here," said Steve Pennington, a construction worker sitting at a table around the corner from Merchant.

And even if he did?

"I wouldn't use it," he said, adding that he would call for help and start CPR in an emergency. "I wouldn't feel comfortable without being trained."

Pennington's not alone.

AED's are used less than five percent of the time, according to Merchant.

"That's a huge missed opportunity," she said, pointing out they're simple enough for bystanders without any training to use.

"As soon as you open the device, it starts talking to you and walks you through exactly what to do [including how to do CPR]," she said.

Dr. Merchant and others at the University of Pennsylvania recently issued a call-out to designers, to develop flashy AED stations, such as one now on display at 30th Street. They want them to be accessible, approachable and easy to spot.

That way, if someone were to collapse, say right here, bystanders would know what to do, and not waste any precious seconds before starting to help — seconds that could mean the difference between life and death.

Cardiac arrest claims some 350,000 lives annually in the U.S.