In our CPR class three months ago we did compressions + breaths, but this was for health care workers. We were told that if we're by ourselves or don't have a barrier for breathing, we should feel free to do compressions-only CPR.

We were basically told that CPR is used to keep oxygen flowing to the brain until someone can get there with a defibrillator. CPR by itself has very slim odds of restoring a viable heartbeat.