Considering that the brain and other vital organs can only exist for a few minutes after cardiac arrest, the patient needs to undergo resuscitation measures (artificial ventilation with simultaneous compression of the sternum) and provide emergency medical care. Pressing on the sternum ensures blood circulation in the absence of heart contractions. Mechanical ventilation and chest compressions force the heart and lungs to function at least partially. Resuscitation increases a victim's chances of survival by providing oxygen to the brain until qualified medical help arrives. Without such resuscitation procedures, brain death begins to occur within four to six minutes (Figure 5-3). Resuscitation measures ensure the minimum required blood flow to the brain and heart (25-35 percent of normal). Even with the use of resuscitation measures, the chance of saving the life of an injured or sick person is very small, unless he is quickly provided with qualified medical care.