I am quite squeamish, but I did a first aider course a few years ago and was ok. If you have any particular issues/things that make you upset, it's a good idea to tell the person running the course at the start - they are usually helpful. After all, people needing first aid can't choose who they become injured in front of and a squeamish person with basic training is surely better than a non-squeamish person with no training.
Mine has lapsed and I need to redo it when I have time. But I had to stop to help a couple of months ago to help someone who was injured and had difficulty breathing. Didn't do much apart from recovery position, but I was the only one who stopped for quite a while & I'm sure my memory of the course helped even if it was a while ago. Always worth doing as you never know when you might need it.
