New York State Emergency Medical Technician (EMT) Practice Exam

How long can the brain survive without oxygen before brain damage is likely?

1. 2 minutes

2. 4 minutes

3. 5 minutes

4. 6 minutes

The correct answer is: 6 minutes

The brain is extremely sensitive to oxygen deprivation, and its cells can start to become damaged quickly when deprived of oxygen. Although brain cells can survive without oxygen for a short period, significant damage typically begins to occur around the six-minute mark. After about four to six minutes without oxygen, brain cells start to die, and irreversible brain damage is likely. This is important in emergency medical situations because it emphasizes the critical need for immediate resuscitation efforts, such as high-quality CPR or the use of an automated external defibrillator (AED), to restore oxygen supply to the brain as quickly as possible. The choices listed reflect varying degrees of understanding about the timeline of brain tolerance to hypoxia, but six minutes is widely accepted in medical literature as the threshold where damage becomes likely. This context underscores the importance of prompt intervention in cases of cardiac arrest or other situations leading to hypoxia.