National Geographic : 2016 Apr
the crossing 37 near-hibernation levels. His goal is to make human patients who are having heart attacks “a little bit immortal” until they can get past the medical crisis that brought them to the brink of death. In Baltimore and Pittsburgh trauma teams led by surgeon Sam Tisherman are conducting clinical trials in which gunshot and stabbing victims have their body temperature lowered in order to slow bleeding long enough for surgeons to close up their wounds. The medical teams are using supercooling to do what Roth wants to do with chemicals—kill their patients, temporarily, in order to save their lives. In Arizona cryonics experts maintain more than 130 dead clients in a frozen state that’s another kind of limbo. Their hope is that some- time in the distant future, maybe centuries from now, these clients will be thawed and revived, technology having advanced to the point where they can be cured of whatever killed them. In India neuroscientist Richard Davidson studies Buddhist monks in a state called thuk- dam, in which biological signs of life have ceased yet the body appears fresh and intact for a week or more. Davidson’s goal is to see if he can de- tect any brain activity in these monks, hoping to learn what, if anything, happens to the mind after circulation stops. And in New York, Parnia spreads the gospel of sustained resuscitation. He says CPR works better than people realize and that under prop- er conditions—when the body temperature is lowered, chest compression is regulated for depth and tempo, and oxygen is reintroduced slowly to avoid injuring tissue—some patients can be brought back from the dead after hours without a heartbeat, often with no long-term consequences. Now he’s investigating one of the most mysterious aspects of crossing over: why so many people in cardiac arrest report out-of- body or near-death experiences, and what those sensations might reveal about the nature of this limbo zone and about death itself. Oxygen plays a paradoxical role along the life-death border, according to Roth, of Seattle’s Fred Hutchinson Cancer Research Center. Ever since oxygen was discovered in the early 1770s, “scientists have recognized it as essential to life,” he says. What the 18th-century scientists didn’t know is that oxygen is essential to life in a surprisingly nonbinary way. “Yes, if you take away oxygen, you can kill the animal,” Roth says. “But if you further reduce the oxygen, the animal is alive again, but it’s suspended.” He has shown that this works in soil nem- atodes, which are alive in air with as little as 0.5 percent oxygen and are dead if you reduce the oxygen to 0.1 percent. But if you then pro- ceed quickly to a much lower level of oxygen— 0.001 percent or even less—the worms enter a state of suspension where they need signifi- cantly less oxygen to survive. It’s their way of preserving themselves during extreme depri- vation, a bit like animals hibernating in winter. These oxygen-starved, suspended organisms appear to be dead but not permanently so, like a gas cooktop with only the pilot light on. Roth is trying to get to this pilot-light state by infusing experimental animals with an “ele- mental reducing agent,” such as iodide, that greatly decreases their oxygen needs. Soon he’ll try it in humans too. The goal is to minimize the damage that can occur from treatments after heart attacks. If iodide slows oxygen me- tabolism, the thinking is, it might help avoid the blowout injury that sometimes comes with treatments like balloon angioplasty. At this low- er setting the damaged heart can just sip the oxygen coming in through the repaired vessel, rather than get flooded by it. Life and death are all about motion, ac- cording to Roth: In biology the less something moves, the longer it tends to live. Seeds and spores can have life spans of hundreds of thou- sands of years—in other words, they’re practi- cally immortal. Roth imagines a day when using Tune in Sunday, April 3, to National Geographic Channel’s Explorer series episode Faces of Death.