This is one reason I prefer prong collars to choke chains.

A Study on Prong Collars was done in Germany:
100 dogs were in the study. 50 used choke and 50 used prong.
The dogs were studied for their entire lives. As dogs died, autopsies were performed.
Of the 50 which had chokes, 48 had injuries to the neck, trachea, or back. 2 of those were determined to be genetic. The other 46 were caused by trauma.
Of the 50 which had prongs, 2 had injuries in the neck area, 1 was determined to be genetic. 1 was caused by trauma.
http://www.cobankopegi.com/prong.html

I also once read somewhere, that a choke chain used incorrectly can cut off the blood supply to the head, killing a dog. Prong collars are much easier to use correctly. You just have to make sure that it is not too tight (because if it is, the prongs will pinch the dog), and that it is high up on the neck. My dad wore a prong collar around his neck once for Halloween, and my stepmom dragged him around. He said that it didn't hurt all all when she pulled, it was just uncomfortable. He said it was no wonder the prong collar wasn't even effective on Leather -- she had fur, he only had bare skin, and it was only uncomfortable for him lol.