My husband suffers from kidney stones.
Several years ago he had one so bad that he was vomiting from the pain - so we went to the ER.
They decided that he would make a good patient for a training EMT to try out inserting an IV line on.
The supervising nurse told him, "You really need to hold still, he hasn't done this before and the faster he gets this line started, the faster you can get some pain medication."
I promptly told her to go let him experiment on a patient in less pain and get someone in there who knew how to start an IV, that vomiting was not really a voluntary action!