SEATTLE, Washington (CNN) -- A wiry, slightly hunched man presses in a few numbers, the electronic lock gives way with a beep and the group presses into the crowded laboratory, plastered with ominous warnings about toxins and biohazards.

Guiding the visitors at the Fred Hutchinson Cancer Research Center is Mark Roth, a 50-year-old biologist with a tall forehead, thinning red hair and a perpetual wry smile. He asks his assistant, Jennifer Blackwood, if the rat is ready. It is. She turns a dial, and the sealed enclosure starts to fill with poison gas -- hydrogen sulfide. An ounce could kill dozens of people.

The rat sniffs the air a few times, and within a minute, his naturally twitchy movements are almost still. On a monitor that shows his rate of breathing, the lines look like a steep mountain slope, going down.

At first glance, that looks bad. We need oxygen to live. If you don't get it for several minutes -- for example, if you suffer cardiac arrest or a bad gunshot wound -- you die. But something else is going on inside this rat. He isn't dead, isn't dying. The reason why, some people think, is the future of emergency medicine.

You see, Roth thinks he's figured out the puzzle. "While it's true we need oxygen to live, it's also a toxin," he explains. Scientists are starting to understand that death isn't caused by oxygen deprivation itself, but by a chain of damaging chemical reactions that are triggered by sharply dropping oxygen levels.

The thing is, those reactions require the presence of some oxygen. Hydrogen sulfide takes the place of oxygen, preventing those reactions from taking place. No chain reaction, no cell death. The patient lives.

Roth's work was inspired in part by personal tragedy. In 1995, his world was turned upside down when his new daughter, Hannah, died after a year of painful medical problems. After that, he decided to go for broke -- to try to tackle something big. "It focuses the mind, when certain things happen to people, and it certainly focused mine." Read more about ways to cheat death

After that, and after his conceptual breakthrough, Roth was ready to experiment. First up: developing fish embryos. He found a way to drain the oxygen from their cells, and they wouldn't die -- they'd just stop growing. When he put the oxygen back, they'd pick up where they left off. If he suspended them for a day, they took a day longer to develop. No more, no less. Nothing else was different.

Next up were fruit flies. This time, he gassed them. They seemed to die; they stopped moving. Then he returned them to fresh air, and the flies came back to life. New CPR beat back death for a young mom

The air we breathe is 21 percent oxygen. At 5 percent, those fish and flies -- like us -- would be dead in a few minutes. At 0.1 percent, it was another story. "You get a state of suspended animation and the creatures do not pass away, and that's the basis of what we see as an alternative way to think about critical care medicine," Roth says. "What you want to do is to have the patient's time slowed down, while everyone around them [like doctors] move at what we would call real time."

If the patient's time -- the process of your death -- were slowed down, doctors would have more time to fix you. In medicine, time is key. An analogy is the history of open heart surgery. For years, surgeons had the technical tools to make simple repairs on the heart, but they couldn't help patients until the development of the heart-lung machine made it possible to preserve the body for more than a few minutes without a heartbeat.

http://www.cnn.com/2009/HEALTH/10/09/cheat...tion/index.html