I had to use it 7 years ago during pool league on one of the counter girls. She just suddenly dropped and was moaning and then she lost conscious and stopped breathing so me and another guy who knew first aid and CPR teamed up to get her heart started again and mouth to mouth until paramedics arrived. They got her to the hospital and it seemed like she was stabalizing but then she passed away, aneurysm.
I was pretty out of it with shock for awhile after that. I took my course through St. Johns Ambulance.