If a person with ventricular fibrillation is treated right away, treatment is 90% successful (it works in 9 out of 10 people). But treatment gets 10% less successful after every minute (so if treatment starts after one minute, it will work in only 8 out of 10 people. After 5 minutes, it will work in only 4 out of 10 people.) So getting treatment as soon as possible is very important. If a person cannot be treated with medicine or a defibrillator right away, CPR will help keep blood and oxygen flowing through the person's body until treatment arrives.