That happened to Peek a Boo one morning. The yellow bile he tried to vomit was so thick it got stuck in his throat and blocked his airway. This is a concern anytime a dog vomits though. Since then I have added an infant aspirator (blue rubber bulb squeezy thing to clear infant noses) to my first aid kit, along with a copy of the CPR instructions from the YT Library:
http://www.yorkietalk.com/forums/eme...uture-use.html
Depending on whether or not the airway is completely blocked or only partially blocked, there may not be time to make it to the vet in time to save the dog. Clear the airway first, perform CPR if needed, then go to the vet. If the dog's tongue is pink, he's getting oxygen, if it's turning purple, he is not getting enough oxygen and is an emergency.