By Shirley Li
May 01, 2015 at 06:15 PM EDT
Desiree Navarro/WireImage

In an interview with Today set to air Monday, Joan Rivers’ daughter Melissa tells Matt Lauer that her mother’s death “was 100 percent preventable.”

“How about paying attention to the vital signs?” she says of Manhattan’s Yorkville Endoscopy Clinic, where Joan underwent surgery before her death. “How about having a properly equipped crash cart?”

Rivers also spoke of seeing her mother in the hospital before her death at age 81.

“I just couldn’t believe what I was seeing,” she tells Lauer. “It becomes very surreal. I’d gotten emails on the plane that she was already in a medically induced coma and they were dropping her body temperature, which I knew was bad because that’s the protocol for catastrophic brain injury.”

Melissa Rivers has filed a malpractice lawsuit against the clinic. In it, the younger Rivers alleges the clinic performed an unauthorized exam of the late comedian’s vocal cords and windpipe that deprived her brain of oxygen.

Watch a clip from the full interview with Melissa Rivers below.