Dr. Mike Hansen goes into the anatomy and physiology of asphyxia, and how it applies to the death of George Floyd:
So there you have it…that’s how he was able to say “I can’t breathe”, right before he passed out and died. He had another officer on his back, compressing his diaphragm. He was able to breathe out, enough to speak a few words, but he couldn’t breathe in. He was kept from breathing in by cops on his back and neck.
And that’s what killed him.