That must have been terrifying and traumatizing to watch, so sorry!
I have heard of non-constricting colubrids eating prey alive before. Just slither up and gulp it down. I assume that means that they can handle it?
For what it's worth, the rat probably passed out and then died on the way down after the first claustrophobic struggle. Being inside an esophagus, it would not be able to get any more air than it had before its head was engulfed, and it was already weakened and lacking oxygen.
Hopefully that doesn't happen again! Sorry you had to witness that.
Sent from my iPhone using Tapatalk