So I'm writing this short creepy pasta and I'm not going to copy and paste the whole thing into this post but I really can't decide which of the two terms would have a better effect. 

Vomit surged up from his stomach and flowed out of his mouth, pooling around his  convulsing/ now lifeless  body.

The guy's gonna die but if I write convulsing then I have to drag it out a bit. Glad to hear any feedback.