Dr. Jennifer Ashton talked about the case Friday on The Early Show.
"Entertainment Tonight" had obtained an exclusive photograph of paramedics working on Michael Jackson. Asked what this picture tells her about the circumstances surrounding his death, Ashton said, "What that tells you is there's something covering his mouth, and that indicates the paramedics did try aggressive resuscitation at his home. They placed a breathing tube into his wind pipe so they could pump with a bag there, which you can see, the paramedics moving to work to oxygenate his blood."
What happens to the heart when it goes into cardiac arrest?
"Basically, the electric signals become uncoordinated, and that impairs the pumping function of the heart. The blood pools in the bottom of the heart, if you will. Can't be circulated to the heart, the brain, the rest of the body. Within about four to six minutes, brain death will occur," Ashton explained.
"So four to six minutes, is that how much time you have for resuscitation?" Maggie Rodriguez asked.
"Yes. Early CPR or early use of a defibrillator is really the best hope for survival. Only five percent of people, so 95 percent of people who suffer an out of hospital cardiac arrest will die before making it to the hospital," Ashton said.
A lot of people hear cardiac arrest and assume heart attack, but there can be many causes of cardiac arrest. "It can be anything from an electrolyte abnormality to a blood clot to aneurysm bursting. There are a number of things they're going to look at when doing the autopsy," Ashton explained.
Asked if drugs could play a role, Ashton said, "There could be a drug overdose accidentally. There could be a drug interaction that causes a respiratory arrest. We heard his bad breathing stopped. After you don't breathe, the oxygen impairs the ability for your heart to function, and you will suffer a cardiac arrest."