Going through EFR course is great, but like others have mentioned you don't know how you will react in a true emergency until you are faced with one. It's MUCH easier to stay calm and thoughtful when you KNOW it's a scenario and someone is not really in trouble. I have not been through the rescue diver class, oxygen provider or even their EFR course. My career lies in EMS as an EMT and next month I take my national exams to be a Paramedic. I work full time in a very busy city EMS system. Having been faced with the unique situations of a "rescue," I can say that none of them are like any scenario that you went over in class. The class scenarios tend to give you a clearly defined picture of a certain situation. Real patients do not present "like the book."
Remember to stay calm, if you panic that you're not doing anyone any good and could end up a victim yourself. For the vast majority of patients, oxygen will not hurt them. I have heard people mention the use of demand valves. In EMS the demand valve has fallen out of favor to the non-rebreather face mask since there's less chance of filling someone's stomach with gas and having them vomit and aspirate.
Never stop learning and practicing your skills, and remember to call for help as early as possible. Good luck.
Shane
