If you are faced with a victim in cardiac arrest and you do not feel comfortable providing rescue breaths “Compression Only CPR” is an available option to provide care without the risks of expose associated with mouth to mouth breathing. Compression Only CPR is as it sounds. Rescuers perform the steps of CPR without giving breaths to the victim. Compression Only CPR works by circulating the oxygen inside the victim before they collapsed. The oxygen inside the victim will vary based upon the situation but may afford the person a greater chance of survival over doing nothing. In many situations, compression only CPR will be adequate until trained responders arrive. There is little difference in survivability, at least initially, for an out of hospital witnessed cardiac arrest with compression only CPR vs. CPR with rescue breaths.
For more information: How to perform CPR