Thats because it doesnt have the same function as the Bypass machine, the machine in the mod is used for when you remove a lung from a human so they dont die, the bypass machine will keep people alive even if there heart stops beating, this is some help Also to get bypass machine go to the gear icon and scroll until you find it.

When your connecting the human upper torso to the machine, make sure that you start from the machine. I just found that out and I was having the same issue before

i cant do lungs