How do you feel about not performing any additional lifesaving method on someone who doesn't respond to a second head tilt/chin lift? In other words - in emergencies we may not be able to perform CPR.

By the time you should have already called 911 so hopefully they should be close enough to be able to take over. (you should still be on he phone with the 911 operator so you should continue doing what you are doing unless they say otherwise) IF NOT THOUGH then you should still continue performing CPR (or have someone else take over) until medical help arrives.

Explanation:

a1 = unhealthy

a2= healthy

a3= healthy

answer(b) keep oxygenated and deoxygenated blood separate;