Outside the cave, in an area filled with butterflies and snakewood trees known as the oxygen bar because of the quality of its air, Sun Luyao, 21, watched over her grandmother, 72, who was suffering from lung cancer. Nearby, dozens of seniors threw their arms into the air, soaking in the light.

Ms. Sun, from the northeastern city of Harbin, said she worried the cave had been overrun by tourists and was beginning to lose its healing effects. “If too many people come, the good oxygen will be sucked out,” she said.

For those who do not improve, the experience of moving to Bama can be draining and disappointing.

Mr. Wu, a former supervisor at a plant that produced baijiu, a clear Chinese liquor, had a devastating stroke four years ago. He ambles down the streets of Bama with a wooden cane, feeling dizzy and struggling to understand people.

Every morning, Mr. Wu takes part in what are called life revival exercises. On the banks of the Panyang River, he throws his arms into the air, twists his waist and slaps his thighs, repeating lines of encouragement along the way (“Surprise yourself! Try harder!”).

But Mr. Wu still struggles to walk long distances, cook and hold a conversation. His wife has grown tired of living in an area with so many sick people, she said.

Mr. Wu said he had given up on Bama and would return to his hometown in the northwestern province of Gansu next month.

“As long as I can manage my own life and not bother other people, I’ll be fine,” he said. “I just want to be healthy.”