A spokesman for the University of Chicago Medicine Comer Children's Hospital says Tuesday that Nathan Woessner's (WAYZ'-ners) condition remains unchanged.
Doctors say he's expected to recover and should be released in about two weeks.
The Mount Baldy area at the Indiana Dunes National Lakeshore will remain closed indefinitely following the accident.
Authorities believe Woessner may have fallen into a hole that was created by a long-buried tree that had decomposed, leaving a void in the sand.
The Sterling, Ill., boy was buried under 11 feet of sand on Mount Baldy at the Indiana Dunes National Lakeshore near Michigan City, Ind., on Friday. It took hours for rescue workers to dig him out. He was limp and cold, but began breathing on his way to the hospital.
Nathan was taken to Comer Children's Hospital in Chicago. He is responsive, and can move his arms and legs, but doctors say he is sedated and on a ventilator Monday morning to help in his recovery.
"Because of his lung injury, we are trying to keep him sedated with medication. And intermittently we have also had to give him medication to paralyze him. So, we actually don't want him awake and following commands and so forth," Dr. Tracy Koogler, University of Chicago Medicine, said. "If he continues recover at the rate he is, we expect him to be off the ventilator by the end of the week."
They are focusing on his lungs, trying to remove as much sand as possible from the boy through bronchoscopies, a procedure in which saline solution is used to flush it out from his lungs. Doctors say it could be awhile until they find out if Nathan had an allergic reaction to the sand.
All indications are that the boy's brain functions are "normal," Dr. Koogler said, but cautioned that signs of any damage could show up much later on. She said if Nathan continues to make such fast progress in his recovery, he could be out of the hospital in 10 to 14 days. Rehab would follow.
The boy's grandfather, Pastor Don Reul, also spoke Monday morning. He said that he and his wife were on a trip when their daughter, Nathan's mother, called them. He rode his motorcycle 15 hours to be at Nathan's side.
"We cast our hearts in that direction, that he's going to be OK," Pastor Reul said. "Nathan is a 6-year-old boy who loved being outside. . .When summer comes, he shoes come off. . . We're looking forward to those times again."
"He was clearly an active boy and the family wants him to return to that and so do we," Koogler said.
Nathan and his 8-year-old friend were following their fathers when they started to climb Mt. Baldy, a 12-story high dune that's closed to the public.
Rescuers say an air pocket possibly created by the same decaying tree stump that caused the sinkhole saved the boy's life.
"We believe that God spared him for a reason so we're very confident that God will give us back Nathan whole," Reul said.
The Associated Press contributed to this report.