The most surprising things I was taught when taking classes in Germany (which went beyond the mandatory classes you have to take to get a driver's license) are the following. Well, not really surprising once you think about it...
- Mouth-to-nose is usually better than mouth-to-mouth, at least when there is no obstructions (like bleeding, broken nose, snot, etc).
- If you're doing chest compressions, expect a high probability of breaking a few ribs. Don't stop, as it is highly unlikely the ribs will break "inwards" and puncture a lung, and a broken rib is still better than being dead.
- Remove all clothing from the chest area you're working during CPR. Yes, that includes bras, specifically. The reason being that any clothes will hurt your hands/rip your gloves (if you have some)/shave the skin off your hand especially when you have to do CPR for 15mins. Bras in particular often have wires etc in them that will hurt your hands even worse. As one of the EMTs training us put it: "Don't be shy, no time for false modesty, it may cost a life."
- Don't forget to breath when giving mouth-to-*. Also, don't forget to actually lift your head when you breath. Else you will just breath in the spent air again that you and the person you're helping just exhaled. Given that CPR is very physically taxing, according to the EMTs it is quite common for people giving the CPR to faint themselves if they breath incorrectly.
- It is more important to call for help than to do CPR. Always call first, if you're alone. And stay on the phone until you're being told you can get off the line. Apparently a lot of people either do not call, or call, scream some stuff into the phone, then hang up to administer help, often forgetting to tell crucial details like their location because it is such a high stress situation.
- Defibrillators do not actually restart hearts that stopped beating. They essentially stop the heart in order to reboot it in hopes it will restart with a proper pace/rhythm.