Experience with situations requiring basic life support (BLS) has demonstrated
that a significant number of casualties suffering cardiac arrest can be successfully
resuscitated if CPR is provided promptly and followed by more advanced cardiac life
support. Prompt response is critical.
a. Early CPR and defibrillation within the first 3 to 5 minutes after collapse, plus
early advanced care can result in high (greater than 50 percent) long-term survival rates
for witnessed ventricular fibrillation.
b. The value of early CPR by bystanders is that it can "buy time" by maintaining
some blood flow to the heart and brain during cardiac arrest. Early bystander CPR is
less helpful if EMS personnel equipped with a defibrillator arrive later than 8 to 12
minutes after the collapse.