Choking/throwing up baby, how do you deal with it?

We went to the ER today - baby was choking after throwing up, couldn't t breath, got blue, etc, until we were able to get him to cry. Thankfully I was not on my own but I am now panicking it might happen again. Now one person tells me pick him up, turn him face down and pat his back until he's ok, another tells me to just leave him laying on his side, but how do I just do that when he cannot breathe?! I am so scared to stay on my own now when the dad goes back work.. Have you had such a scare happen? How do you react?..