Okay, I have to add my two cents.
In order to prove negligence, there are four universally recognized points that must be addressed.
1. duty to act
2. failure in that duty to act
3. harm
4. proximate cause
If a person is in cardiac arrest, nothing worse can happen to them. They are dead at that point. You can crack ribs (and yes it DOES happen from time to time, especially with incorrect hand placement), lacerate a liver or spleen, puncture a lung or whatever. The patient is pulseless and apneic, they are clinically dead. Therefore, even if you have never been trained in CPR, you can do no harm to that patient, so you are not succeptible to liability. This the way that 911 call centers can give CPR instructions ove the phone to an untrained layperson without fear of the legal ramifications.
********The above only applies to the pulseless and apneic patient!!! Patients who ARE NOT pulseless and apneic can have further harm done to them!*****
The Federal Good Samaritian law DOES NOT superscede state law, as spelled out in the Federal good samaritan law. The Federal Good Samaritan law only applies to AED usage, so State law is more protective anyway.
The following is an excerpt from the National Conference of STate Legislatures
http://www.ncsl.org/programs/health/aed.htm
Capnography is the wave of the future. A person in cardiopulmonary arrest with proper CPR and capnography will show changes in the capnography readings. All of my medics are now using capnography not only in codes, but in breathing difficulty calls as well.
Final point. Someone mentioned that it takes 10-15 seconds for CPR compressions to become effective. This is in fact true. If has been found that fifteen compressions is not enough time for the backpressure to build to a suitable level. In fact, over the phone lay person instructions for CPR are now completely omitting the breathing component.
Follow the local guidelines until they change.