Melissa Rivers claims Joan Rivers' death was ''100 percent preventable.''

The 81-year-old star died following complications from an endoscopic procedure almost eight months ago and her daughter, who has since filed a malpractice lawsuit against the New York City clinic where she was undergoing the surgery, believes her medical team should have paid ''attention to the vital signs.''

The producer said: ''In my opinion, it was 100 percent preventable. How about paying attention to the vital signs? How about having a properly equipped crash cart?''

Melissa also told the 'TODAY' show - in an upcoming interview that will air on Monday (04.05.15) - that she found out via email that Joan was in a medically induced coma while flying to be by her bedside.

She said: ''I just couldn't believe what I was seeing ... it becomes very surreal.''

Melissa previously admitted she believes the late 'Fashion Police' co-host knew she was with her when she died.

She said: ''I was grateful to have had those few days to be able to let go a little bit. I tried to make the transition as peaceful and beautiful as she would want it to be.''

The star is suing the clinic because she alleges doctors performed additional procedures on Joan without her consent while she was sedated and continued to operate on her mother while her blood pressure and heart rate dropped.

She previously said: ''Not only did my mother deserve better, every patient deserves better. It is my goal to make sure that this kind of horrific medical treatment never happens to anyone again.''