I finally did it! And I'm so glad I did. I did not know that the aim of CPR was to keep oxygen in the blood and then through compressions keep that blood moving through the body supplying oxygen to the brain and other vital organs. I thought (probably from seeing it too many times on TV) that you were trying to restart the heart. Not so young grasshopper. You are just life support until medical aid arrives.
If you haven't got your Senior First Aid yet I encourage you to do it, you'll feel so much better... more prepared.