As a former Emergency Medical Technician, I can tell you this is covered during training so that the ambulance/rescue personnel will know what it takes to properly compress the heart and circulate the blood. I’d recommend you seek out a local source of your acquaintance like a fire/rescue crewman or EMT. They know...
Your right, ribs break if you compress in the wrong area of the body. In the hospital, we never had broken ribs because of CPR Too many people don’t know what they are talking about, they just think they know....