I've seen a lot of discussion about Booker's nosebleeds and all of that is pretty much clear to me.
I still don't understand though why the soldiers you meet right after going through the tear in Chen Lin's cell are having nosebleeds. You kill them in one reality then you go to another. They should be either alive or dead, not struggling to cope with multiple sets of memories (as I understand, the reason for nosebleeds), as they did not have any contact with other realities.
I thought it could have been because Elizabeth actually merged parts of two realities (like when she summons things to help you in battle), or even that the proximity with the tear would cause the nosebleeds... But then all the prisoners you meet along the way should be having seizures and bleeding as well.