Despite the almost unbelievable news yesterday of an 84-year-old woman being pulled out of the rubble 10 days after a 7.0-magnitude temblor rocked Haiti, we're now pushing "the outside limit" of human survival.

Earlier yesterday, the Associated Press reported, the 84-year-old woman pulled from her home's wreckage was being given oxygen and intravenous fluids by doctors at the General Hospital, but her condition was such that they doubted she would live. Later yesterday, though, an Israeli search team pulled a 21-year-old student and tailor from a crevasse in a two-story home's rubble, and doctors expected him to make a full recovery, the AP said.

Over the weekend, rescues remain possible, albeit unlikely. At two weeks, survival -- even for an uninjured person -- would be all but impossible without access to water. So concludes University of Pittsburgh professor Donald M. Yealy, chairman of emergency medicine.

At this stage, with each tick of the clock, chances of survival dwindle. "I would not be completely surprised if there is a story or two about finding people who are still alive, but I don't expect that to happen," Dr. Yealy said. "Survival is exceptionally rare after 10 days."

Any rescues at this stage likely would involve younger people, perhaps teenagers or people hale and hearty before the quake. They also would have had to survive structures crumbling around them without serious injuries.

"Survival after 10 to 14 days is rare," Dr. Yealy said. "Surviving two weeks is unheard of, absent water and eventually food."

The deadline may be passing for anyone younger than 2 or older than 65. "The very young [under 2] are the least likely to survive, because they are prone to dehydration, and they need calories," Dr. Yealy said. The same applies for the elderly with less than ideal health and fitness.

A CNN story this week quotes Eric Weinstein, an emergency physician in Summersville, S.C., who is on the Disaster Preparedness and Response Committee of the American College of Emergency Physicians, saying survival at this stage "underscores the body's resilience in the face of adversity."

"You can go 10, 12, 13 days without really having a problem," he said, noting that such a person would have to be healthy to begin with.

More than 120 people have been pulled alive from the rubble, the United Nations had said by midweek.

So survival this long would hinge on age, health and lack of bleeding injuries, which would accelerate dehydration and reduce nutrition to the body.

But the real key to survival is water. Dr. Yealy said generally healthy people can last weeks without food. But water stands second only to oxygen in importance. Without water, dehydration leads to organ failure.

Most people who die while awaiting rescue succumb to multiple organ failure, usually starting with the kidneys, followed by the liver and eventually the heart, he said.

People last longest at 70-degree temperatures, warm enough for comfort without causing perspiration. Anyone trapped in Haitian sunlight or tropical heat would face ever-diminishing chances of survival.

Dr. Yealy offered this strategy to extend survival time: Stay calm. Preserve valuable energy and body fluids. Too much activity causes perspiration that accelerates dehydration. It's also wise to produce rhythmic tapping with the barest possible motion for rescuers to detect and track your location, he said.

Looking for more from the Post-Gazette? Join PG+, our members-only web site. You'll get exclusive sports content, opinion, financial information, discounts from retailers and restaurants, and more. Our introduction to PG+ gives you all the details.