(CNN) -- Thirty-three miners trapped 2,300 feet (701 meters) below ground in Chile are depending on food, medicine and supplies being dropped to them through a 4-inch-wide tube.
What comes out of that tube will have to sustain the men both physically and mentally for a long time -- perhaps four months, experts say -- while a shaft wide enough to pull a man through is drilled.
The miners already have been trapped for 18 days, since a rockslide inside the San Esteban gold and copper mine cut off their exit route.
A probe retrieved a note from the miners Sunday saying all were alive and well in a cramped, 530-square-foot (50-square-meter) shelter. They survived by sharing tiny portions of canned fish stored in the shelter room.
"Medics now are beginning to put down glucose water through a tube, first starting off with liquids and rehydrating salts, then in the coming days will put more solid food down," CNN's Karl Penhaul reported Tuesday morning from the scene near the town of Copiapo in northern Chile.
"But psychologists say really it is the mental health that's the real thing," Penhaul added. Forced confinement for months in a small, dark, hot space with many other people will pose intense psychological and emotional challenges. The men will have to help one another, Penhaul said.
"They have to make sure on a day when somebody is feeling down, depressed, that the others keep him there to cheer him up," he said.
Davitt McAteer, former director of the U.S. Mine Safety and Health Administration, said the situation is challenging on a number of levels, but the Chilean government seems to be doing everything right.
"It's difficult. It's the size of a studio apartment, and it's dark. Well, now there will be some lights put in, but the conditions were very, very difficult," he said Tuesday morning.
"You have to deal with bodily functions, and you've got to deal with that kind of question. Then you've got to deal with the psychological impact.
"Now, I think the fact that they've made it these 18 days is very, very positive. But the euphoria of making contact with the surface is going to last a couple days, and then it's going to be a long slog."
McAteer noted that with current technology, there's no reason the trapped miners have to be isolated from their families and society during their confinement.
"These miners are resilient people, but I think also it's a new era," he said.
"And I see no reason why you couldn't pass cell phones down to them, or computers, tethered down to them. So, we're in a new day. And something will need to be done to divert their attention. ... How do you come up with things for them to do and arrange things so that they can get their attention diverted from just sitting there waiting?"
Added Penhaul: "The families on the surface will also play a role as well, establishing communication with their family members to tell them to keep strong, but above all, to stay patient. They could be down there until Christmas."
CNN's Karl Penhaul, Jim Kavanagh and the CNN Wire contributed to this report.