by Dan Childs, ABC News Medical Unit
Thousands of feet up the frozen side of Oregon's Mount Hood, within a makeshift snow shelter so small it took rescue teams days to locate it, Kelly James spent the final hours of his life in darkness and silence.
James' body was removed by helicopter from the 11,239-foot summit Monday after his body was found over the weekend.
Officials said he had an "obvious" arm injury.
Though autopsy results still have to be released, experts say the mountain's subfreezing temperatures and 80 mph winds brought about hypothermia that likely took the mountain climber's life.
Experts say the end probably came painlessly for the Dallas native, despite the harsh and unforgiving environment.
"The victim will get into sort of a dreamlike state, drifting in and out of consciousness, and they may have visions of random things," said John Sohl, director of search and rescue for Weber County, Utah.
"So the descriptions of people who have been near death and describe their life passing before their eyes is possibly not entirely without basis. ... It's kind of a state of bliss," Sohl said.
"The people I've talked to who have survived, the thing they remember most is their awareness of their coldness," said Dr. Don Trunkey, professor of surgery at the Oregon Health and Sciences University in Portland.
"But it's not painful. Obviously, dying is not pleasant, because I'm sure some people think about their life and what has gone by. But they are just gradually falling into a coma," Trunkey said.
Fighting a Losing Battle against the Cold
Hypothermia occurs when the body is unable to maintain normal temperatures because of exposure to cold.
Death from hypothermia can occur very quickly in certain situations; men falling overboard into chilly ocean waters may succumb to hypothermia in a matter of minutes.
In James' case, however, the time between the onset of hypothermia and his death lasted several days.
"The earliest stages, called mild hypothermia, are characterized by such things as a loss of coordination and changes in personality," said Dr. James Wilkerson, editor of the book "Hypothermia, Frostbite and Other Cold Injuries."
"As it gets a little colder, they would start to shiver uncontrollably. This happens when the core body temperature drops below 93 degrees Fahrenheit. That's a sign of significant hypothermia," Wilkerson said.
At this point, however, James had at least the presence of mind and coordination to make what would be his final phone call to his family.
On Dec. 10, he talked to his loved ones for four minutes using his cell phone.
"He may well have still been suffering hypothermia at this point," Trunkey said. "The fact that he made that call probably meant that he would like to be rescued, and he would like to talk to his family if he had the perception that he was in the dying process."
With time, James' body temperature lowered to between 90 degrees and 93 degrees Fahrenheit.
At this point, experts say, he probably experienced sluggish thinking and amnesia, as well as difficulty speaking.
Victims also begin to have irrational thoughts that could impact their chances of survival. Sohl says he is intimately acquainted with this phase of hypothermia, as he experienced it himself once.
"It's funny how your brain shuts down the rational process," he said.
When he was surrounded by the cold, Sohl says that his natural inclination was to forgo his warm clothing and sustenance, despite the fact that doing so was causing him to freeze to death.
"I had to keep thinking to myself, 'No, this is bad,'" he said. "I finally had enough rational thought to tell myself, 'Put your sweater on! Eat some granola bars!' In an hour or two, I was doing much better."
But Sohl says that during his hypothermic episode, he was not in any real pain or distress -- even though his life was in danger.
"I was feeling unhappy, but I wasn't feeling dread. I actually started to feel quite calm, and that was what scared me," he said.
"Based on this experience, the experience of others, and what I have read, it is not a terrifying process. From the outside point of view it is scary, but without that fear, the drive to take care of yourself is lost," Sohl said.
"Of all the ways to go, this would not be the worst."
Slowly Entering Sleep
Once James' body temperature dipped below 90 degrees, it is likely that his shivering stopped. At this point, experts say, confusion and increasingly irrational behavior begin.
"After the victim is beyond the shivering phase, he or she becomes a risk to himself or herself, specifically with listlessness and drowsiness," said Dr. Richard O'Brien, spokesman for the American College of Emergency Physicians. "After this has set in, irrational thinking and behavior begins -- a preterminal condition."
But like most of the conditions associated with hypothermia, confusion and irrational behavior would have set in gradually.
The discovery of a sleeping bag and other potentially useful gear in an abandoned snow cave a few days before rescuers found James' body suggests that even in the earlier stages of hypothermia, the party may have already been behaving in ways that put their lives at greater risk.
"People in moderate hypothermia do strange things. They may not zip up their clothes. They might not put on their hat and gloves," Wilkerson said. "The fact that they left the snow cave makes me wonder if they were not at least partially incapacitated at that time."
"As you are getting cold -- very, very cold -- different parts of your body start to shut down, and they send messages to your brain telling it that these areas are just fine," Sohl said. "When the brain begins to receive these messages, at that point people start to lose the desire to keep track of their equipment."
"If you see your partner drop a hat or a glove and not care, that's an immediate indication that this person is in deep trouble. Either their brain doesn't care anymore, or the brain simply doesn't know that it's cold."
This apparent lack of concern with survival becomes magnified in severe hypothermia, as Sohl says he found out when he rescued one woman who had progressed into severe hypothermia by the time she was found.
"In her case, she was really quite serene," Sohl said. "She was not frightened, and she was not even really all that alarmed."
"People in this state know they are in trouble, but they have consigned themselves to it. They're pretty calm."
James' Death Likely Peaceful, Painless
Unconsciousness likely came for James once his core body temperature slipped below 85 degrees.
"As the brain cools down, they experience a gradual decrease in their level of consciousness until they slip into a coma," Trunkey said. "After that, all of their metabolic processes start to slow down."
After James' body temperature dropped into the 70s, his heart stopped beating.
"At 75 degrees or so, you begin to have difficulties with heart irregularities," Wilkerson said.
But James' moment of death was likely silent and relatively painless as he slept in his cocoon of snow.
"I think that obviously this won't relieve the grief of the family, but nevertheless, probably none of these people suffer from a physical standpoint, other than having a cold feeling," Trunkey said.
Perhaps James' family can take comfort that his death was likely not violent; he just fell asleep.
"People who are in deep hypothermia, they are not stressed out," Sohl said. "I think you sort of drift away."