How doctors will determine shape of boys after 16 days trapped in a dark cave

The four youth soccer players, who were rescued from a cave in Thailand where their coach and eight teammates remain trapped for at least another day, are being evaluated at a hospital for everything from infections to oxygen deprivation and dysentery, medical experts said.

The medical exams for the four boys began before they even left the Tham Luang Nang Non cave in northern Thailand. Doctors and nurses at a triage camp set up just inside the mouth of the cave gave the boys quick physicals before they were sent to a hospital in Chiang Rai.

"In medicine, we always want to get an assessment of their current situation, hope for the best and prepare for the worst," said Dr. Jennifer Ashton, chief medical correspondent for ABC News.

The four rescued boys, who were trapped for 16 days deep in the cave, were safely retrieved from their underground tomb after a treacherous journey in which elite divers escorted them through narrow passages and flooded areas that required the use SCUBA gear to get through, before trudging through mud and waist-high water on foot.

Once evaluated by a medical team, the boys were put into ambulances and driven to waiting helicopters that flew them to an old airbase near Chiang Rai where they were shuttled into ambulances again and driven to the hospital.

Doctors were waiting in the emergency bay at the hospital in Chiang Rai with IVs to give the boys nutrition and much-needed hydration after their arduous trek to safety.

The boys were then taken to the eighth floor of the 14-story hospital, which was reserved for the rescued soccer players and their still-stranded teammates and coach.

While there was no immediate word on their condition, Dr. Ashton said doctors will likely conduct a battery of tests on the boys to evaluate not only their physical condition but their mental condition as well.

"When they're deprived of light and their comfort issues from home there can be psychological sequelae that have to be addressed, and we've seen that before with people who have been held hostage or in kind of difficult environmental situations," Ashton said, referring to the medical term for the after effects of a traumatic incident.

When the lost group was located on July 2, rescue medics who reached them evaluated all the boys and their coach and divided them into three categories: red for critical condition, yellow for serious condition and green for stable condition.

"With our informal assessment, we found that most of the boys are in green condition," Chiang Rai provincial Gov. Narongsak Osatanakorn told reporters. "Maybe some of the boys have injuries or light injuries and would be categorized as yellow condition. But no one is in red condition."

Dr. Ashton said the boys are possibly weak from lack of solid foods and from being sedentary on a small beach inside the cave where most remain marooned.

"This is a catabolic state for these kids and this coach, meaning they are breaking down muscle because their physiologic state of stress is so high," she said.

Dr. Paul Auerbach, a professor of emergency medicine at Stanford University School of Medicine, told ABC News that another big concern is oxygen deprivation.

"My understanding of the oxygen situation in the cave is that the ambient oxygen in the air had been measured at about 15 percent now," Auerbach said. "Normal oxygen content in the air is about 21 percent. So what this means is that more oxygen is being consumed than is being replaced. Air has to be brought into that cave."

Officials in Thailand said that after the first four boys were removed from the cavern, rescue crews began replenishing oxygen in the cave by pumping oxygen from the outside and replacing air tanks used in Sunday's rescues.

"At a 15 percent [oxygen] level, you start to see decreases in performance, physical performance and mental sharpness," Auerbach said. "As the oxygen content would progressively lower, you would expect both of those to worsen until it got to the point where they would be incapable of performing."

On Friday, a volunteer diver died in the cave from oxygen depletion. The incident prompted authorities to pull nonessential rescuers from the cave to conserve oxygen levels.

Since the group was located, rescuers have been supplying them with fresh water and food high in protein.

"But to be without food and a lot of water for nine days makes you pretty weak," Auerbach said.

He said it could take several days for doctors to replenish the nutrients the boys lost during their cave ordeal.

"In terms of re-feeding and the regaining of strength, there's only a certain amount of energy that you can re-accumulate, and it doesn't happen in just a couple of days," Auerbach said. "So to get them back to their baseline -- which would require food, water, vitamins, all the nutrients that we normally have, plus reasonable exercise of muscle tone -- would take a matter of weeks."

If all the boys and their coach are able to be rescued, they'll likely be showered with affection by their families and well-wishers.

"They'll get a tremendous amount of attention," Auerbach said. "They'll be heroes."

"That's intimidating as well as somewhat uplifting, but it won't be addressing the fears and the difficult emotions that the boys have gone through."

He said he expects some of them will suffer from post-traumatic stress disorder.

"They'll be hyper-vigilant, they may have nightmares, they may be fearful, they may regress a bit in their behavior. Some of them may actually get a little bit depressed," he said. "They'll avoid certain circumstances. They probably won't like enclosed spaces. They'll need support through that."

"Hopefully," he added, "in the long term, they'll also come away with new strengths that they never had before."

"You can expect that some or all of these boys will be much better in a crisis. They'll be resilient. They'll have a new outlook on life that will be remarkable and hopefully very positive."