The Houston Chronicle reported Sunday the Tejano singer arrived at Memorial Hermann-Texas Medical Center in a coma and with brain damage suffered when he crashed his tour bus last week and now is part of a pivotal study of the use of cold temperatures to heal the brain.

Neurosurgeon Dr. Guy Clifton said patients such as Navaira are vital to the study since their potential recovery could indicate whether the revolutionary medical theory holds true.

"This is the pivotal trial," Clifton said

"These patient outcomes will determine whether the therapy is buried or becomes the indicated procedure."

Navaira's surgeon, Dr. Alex Valadka, said the "She Gives" singer's condition was improving last week after undergoing the procedure. However, Valadka told the Chronicle the 45-year-old singer was still in critical condition as of Saturday.