If you're not certain how or when to perform the artificial breaths of CPR, just skip them. New recommendations out today from the American Heart Association suggest immediate chest compressions are far more valuable, and breaths are best left to trained responders.
Image via Hawaii Air National Guard.
The old mnemonic for learning CPR was "A-B-C": Check the airways for blockages, give an artificial breath, and then start chest compressions. But now experts recommend a "C-A-B" approach — start pressing on the chest before anything else. A CNN write-up of the new guidelines provides both some background and telling anecdotes of why it works:
The AHA guidelines also uphold a 2008 recommendation that untrained responders call 911 but then forget rescue breathing completely, and simply press on the victim's chest until help arrives.
... All the changes apply only to adult victims who collapse of cardiac arrest; artificial respiration is still recommended for children and for adults in a few cases, including near-drowning and drug overdose.
So if you're trained in CPR and fully know what you're doing, by all means, provide breaths when you can (every 30 compressions is generally recommended). Otherwise, learn how to keep CPR time using "Stayin' Alive" and read up on the American Heart Association's official CPR guidelines, linked here (but having some server troubles at the moment).