Does his gasp sound a little like a snort? We had a thread about that recently and I think it was called 'reversed sneezing.' I know all of the dogs that I have ever had have done it at one time or another but I don't know the cause. I never had it appear at the same time as vomiting, though, so it is very wise to check with your vet. Please keep us updated and I hope Kai will be fine.