Wow, that was enlightening

[Griselda]

My CPR instructor out here says that if you do it correctly, there will be some nasty crunching and stuff at first as the cartilage breaks away from the ribs, but that after that you can pretty much feel where the "bottom" of your compression should be. He claims that the person will be bruised and uncomfortable, but probably won't have their ribs broken, just a lot of torn cartilage.

He says that we should break the ribs of people who are choking, though.