For three days and two nights, illusionist David Blaine will enjoy an unusual view of New York City's Central Park -- one that can only be enjoyed from six stories in the air, while hanging upside down.
The magician's latest stunt, called the "Dive of Death," began 8:30 this morning as he was hoisted into position. The effort will reportedly culminate in Blaine dropping to the ground at 11 p.m. Wednesday.
Dr. Ronald Ruden, Blaine's physician, told ABCNews.com that when he first heard the name of the stunt, "It scared the crap out of me."
Considering the various health hazards Blaine may face as he hangs in the position for about 60 hours, Ruden's concern is warranted. He said the stunt will be all endurance -- no smoke and mirrors.
"How he does this I'm not 100 percent sure," Ruden said. "He seems to have the ability to use his mind to control his body to not experience pain and discomfort, as well as take away his basic drives to eat and sleep and defy his fear."
"We don't even know what the physiology of this is," he said with a laugh. "I hate that."
Blaine told "Good Morning America" today right before he was hoisted into the air that he always found images of Harry Houdini hanging upside down "compelling to look at."
Houdini dangled upside down wearing a straightjacket and tried to escape as quickly as possible, but Blaine's niche is testing his endurance.
"I always liked that idea of being upside down," Blaine said. "So I started experimenting on how long could somebody actually be put upside down. And there was no documentation of it. Nobody really had research on it. I invited doctors to kind of look and watch me as I was doing experiments. And although the dangers are high, I think there's a way to override that. "
Blaine said he has prepared for the challenges of the 2½-day hang by losing some weight, performing special exercises and practicing dangling upside down.
But there are certain health considerations that simple conditioning cannot address. During his ordeal, Blaine will not eat or sleep. He will urinate through a catheter. And doctors not involved with the stunt say there are definite risks involved with his attempt.
"He's practiced a lot, but I'm not sure how long he has done it," Ruden said. "I'm pretty certain that the longest he has done it so far is around six hours."
Blood Pressure a Major Concern for Blaine
In particular, Ruden and other physicians agreed that Blaine will face multitude of risks associated with the unusual increase in blood pressure that Blaine will experience.
"The heart is centered pretty close to the head, so it does not have to pump blood very high," Ruden said. "When you flip it around, though, the toes are four and a half feet from the heart. So the heart has to pump blood to a higher altitude than what it is used to."
This, in turn, means a higher blood pressure. With this risk come a number of possible problems -- not the least of which are stroke and possible blindness as the blood pressure in his eyes increases.
Blaine said doctors will be on hand during the stunt, checking for brain hemorrhaging and stroke and making sure his vision stays clear.
"Certainly, [the stunt] could potentially be very dangerous because the brain relies on gravity to allow blood to flow out of the skull," said Dr. Wendy Wright, assistant professor of neurology and neurosurgery at Emory University Hospital in Atlanta.
"Hanging upside down could cause blood to pool in the skull and pressure could build up inside the brain and eyes," Wright said. "This may result in congestion in the blood vessels causing stokes, or even rupturing of blood vessels causing bleeding. Seizures or death may also result."
The lower extremities have no such problem, of course; as long as we're up and about, our leg muscles do yeoman's work in squeezing the blood back to the heart.
"The lower extremities of man are endowed with constrictor mechanisms that protect the small arteries and capillaries from damage when we stand up," said Dr. Jay Cohn, professor of medicine at the University of Minnesota Medical School in Minneapolis.
"The brain does not have such constrictor mechanisms," he added. "Therefore, prolonged position with the head down may increase pressure in the small arteries and capillaries and lead to blood vessel rupture or blood leakage."
So as Blaine quite literally turns millions of years of evolution on its head, he will also be tempting injury and death. And any pre-existing health conditions could make the stunt even more risky.
"This could be worse if he has high blood pressure to start with," said Dr. Richard Smalling, director of interventional cardiovascular medicine at the Memorial Hermann Heart and Vascular Institute at the University of Texas Health Science Center in Houston.
"If he had any previously undiagnosed vascular abnormalities in his brain the risk would be magnified substantially. Hopefully these issues have already been investigated and he has been cleared medically."
Cardiovascular issues are only part of the picture. Wright said Blaine will also have to contend with a restricted ability to breathe, because his diaphragm will be upside down, with the weight of his intestines pushing upon it. And a lack of proper blood flow to his legs, if profound, may cause muscle tissue to die off as it is starved of oxygen.
Don't Try This at Home
And then there is the risk of plummeting to certain death.
"If you fall, there's nobody there to catch you," Ruden said. "You become street pizza."
Should Blaine survive the stunt, it will be the latest entry in an increasingly bizarre and death-defying resume.
"In the earlier part of his career he was buried alive, entombed in ice, he stood on top of a pole. All of this had the kind of flavor of death and resurrection."
"Some people think it's a death wish. I think it's the exact opposite -- a desire to live life at its fullest," Ruden said.
And Blaine is certainly not the first to try hanging upside down for extended periods of time. Indeed, an entire industry has been built around a practice called inversion therapy, in which people hang upside down for short periods of time, supposedly to remedy back pain and other ailments.
But while mostly harmless, this unconventional approach to health is not for everyone.
"[Inversion therapy] has its own side effects and adverse health risks, including headaches and bleeding into the retina," Wright said. "People with hypertension, glaucoma, heart disease or women who are pregnant should not try this. All others should check with their doctor before trying inversion therapy."
Still, Blaine is a man who has been buried alive and has spent days encased in a block of ice. In short, it is likely that he will have a few tricks up his sleeve -- or down it, as the case may be -- to avoid harming himself.
"As far as 'tricks,' I suppose this is the 'magic' part that he keeps closely guarded," Wright said. "Presumably, he would have practiced spending long periods of time in this position prior to doing it in public and is sure that his body can handle the changes."
But physicians emphasized that potential copycats should shy away from this stunt. And for Dr. Kenneth Mack, medical director of the Mayo Clinic Pediatric Center, in Rochester, Minn., the idea that even Blaine would attempt such a stunt was baffling.
"I guess with the economy being so bad, people are really turning their lives upside down looking for employment," he said.