As a medical professional with expertise in emergency medicine, I can provide you with information on the critical nature of oxygen to human survival. The human brain is particularly sensitive to oxygen deprivation. Unconsciousness can occur within seconds if oxygen levels drop significantly. **The brain can survive for up to about six minutes** after the heart stops. This is the primary reason why learning cardiopulmonary resuscitation (CPR) is crucial. If CPR is started within six minutes of cardiac arrest, there's a chance that the brain may survive the lack of oxygen. However, after about six minutes without CPR, irreversible brain damage begins, and the brain starts to die. read more >>

The brain can survive for up to about six minutes after the heart stops. The reason to learn cardiopulmonary resuscitation (CPR) is that if CPR is started within six minutes of cardiac arrest, the brain may survive the lack of oxygen. After about six minutes without CPR, however, the brain begins to die.read more >>