The correct sequence of chest compressions and inflations for CPR is 30 compressions followed by 2 inflations. This method, known as the "30:2 ratio," is the recommended approach for performing CPR on adults by organizations like the American Heart Association. The objective of CPR is to maintain blood flow and oxygenation to vital organs until professional help arrives, and the 30:2 ratio has been established as effective in achieving this goal.
In practice, performing 30 compressions at a depth of at least 2 inches at a rate of 100 to 120 compressions per minute is critical, followed promptly by giving 2 rescue breaths. This cycle effectively circulates blood and provides oxygen to the lungs, which is essential for increasing the chance of survival for a victim in cardiac arrest.
The other options do not align with current CPR guidelines. The sequences of 20-2, 15-2, or 10-1 are not established CPR protocols and may not provide the adequate blood flow and oxygenation needed in a life-threatening situation. Therefore, the standard of 30 compressions and 2 inflations maximizes the chances of survival in an emergency scenario.