Thoughts of his daughter are always on Dr. Ismael Nuño's mind. As a cardiac surgeon, he knows the heart inside and out, but he felt helpless the day his daughter's stopped.
"It was the hardest decision that I've ever had to make in my life -- to stop CPR on my daughter," said Nuño.
In 1995, the strain of anorexia took its toll on 18-year-old Catharine. She died in her father's arms after a four-year battle with the eating disorder. But Nuño recalls subtle signs started to show long before the family sought treatment.
"She told us at dinner time that she and a group of her female students at school were going on a diet. I go, 'Why?' She was a gymnast," said Nuño.
In his book, "The Spirit of the Heart," Nuño describes the heartbreak of his daughter's struggle. He hopes her story will help other families win the battle against eating disorders.
But Catharine's passing also inspired him to write about the life and death experiences he's witnessed as a heart surgeon, from the heroic saves to devastating losses.
"To have the reader feel the silence of death -- not bad, not good, but a beautiful, different silence," said Nuño.
He also wrote the different chapters to help support those undergoing major surgery, illness and those who have lost a loved one like himself.
"It tells you, you know through some laughter it's OK, it's OK because on the other side you're going to come out OK, you're going to be just fine, so that's what I want to get across with the book," said Nuño.
Dr. Nuño is the former chief of cardiac surgery at L.A. County USC Medical Center. Besides working on his book, he is the medical advisor for the Alfred Mann Institute for Biomedical Engineering at USC.