You maybe able to save someone's life.

A simple means for preserving life if someone near you collapses and is not responsive.

http://medicine.arizona.edu/spotlight/learn-sarver-heart-centers-continuous-chest-compression-cpr

A very important Post Nightjar, one well worth watching...

Hi Guys.
Yes there is some good information there.
I do want to draw your attention to the need for rescue breaths after a period of time.
It is a well known fact that the American Heart Association has done its research on the time delay for paramedics to arrive and that time avarages 8-10 minutes.
During that 8-10 minute period compressions only CPR is a practical proceedure.
It is reccomended by the Australian rescusitation council to breathe for the unconscious and non breathing person after that time to prevent the build of of carbotic acid within the body.

world wide the CPR protocol is now 30:2 or 100 compressions per minute but please keep time from collapse in mind as you will always be wanting to do your best should the event arise.