Final answer:
Without oxygen, significant brain damage may occur after 4-6 minutes due to lack of ATP production, with potential for brain death. Immediate CPR can increase the chance of recovery, especially in cases of drowning in cold water.
Step-by-step explanation:
After 4-6 minutes of no oxygen to the brain, significant damage can occur. Brain cells start to die, potentially leading to brain damage and eventual brain death, especially if CPR is not administered promptly. In the case of drowning, especially in cold water, there have been instances where children have survived longer periods due to a reflex that protects the brain when submerged in cold water. Nevertheless, the risk of permanent damage increases with time.
When brain cells are deprived of oxygen, they cannot produce ATP, which is critical for cellular function. The body is composed of approximately 20 percent oxygen, and the brain requires constant supply to maintain its high metabolic demands. If the brain's oxygen supply is cut off, brain damage is likely within five minutes, and death may occur within ten minutes. However, immediate medical attention such as CPR can extend the window for recovery, and emergent care should always be sought.