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How Long Can The Brain Go Without Oxygen


It is incredible how an organ weighing only three pounds (our brain) is responsible for the functionality of the whole human body. While the body’s functions rely on the brain, it depends on oxygen to function properly.

The human brain needs 20% oxygen to work and keep the other body’s functions healthy. If a person’s brain does not receive oxygen, they are declared brain-dead, called Cerebral Anoxia/Hypoxia.

What is Cerebral Hypoxia?

When your brain does not receive enough blood, it is called Cerebral Hypoxia. In such a condition, blood and oxygen supply are usually not compromised throughout the body, but it does not reach the brain. Cerebral Hypoxia may be a result of disturbed blood supply due to drowning or cardiac arrest.

Unlike Hypoxia, the blood supply including RBCs and WBCs, to the brain diminishes completely in Cerebral Anoxia. It is the condition when no blood reaches the brain and the death of brain cells begin. The blood and oxygen flow to the brain may stop due to drowning, strangling, cardiac arrest, or others.

When presented with a brain injury resulting from a lack of oxygen supply, doctors usually called it a hypoxic-anoxic brain injury.

What are the Reasons for Cerebral Hypoxic-Anoxic Injury?

Hypoxic-Anoxic Brain Injury may be caused as a result of

High altitude

Traveling or trekking above a height of 8,000 ft. results in decreased oxygen supply to the body.

Asthma attack


Some medical conditions like asthma and COPD make it difficult to breathe, causing a diminished oxygen supply to the brain.


Drinking or eating too quickly can cause choking and obstruct the windpipe.


Being in an enclosed space or while someone is being strangled, they experience a restriction of the oxygen supply, resulting in Hypoxia.


A stroke usually occurs due to a clot that stops the blood flow, reducing the oxygen supply to the brain.


Sometimes, the body struggles to find oxygen and breathe in deep water, causing Hypoxia and eventually Anoxia.

Symptoms of Cerebral Hypoxia

Cerebral Hypoxia is caused by one or other underlying reasons and presents itself in varying forms, including

  • Rapid breathing and heartbeat
  • Decreased blood circulation in feet and hands
  • Stuttering
  • The lips and skin get a bluish tint
  • Dilated pupils
  • Seizures or convulsions
  • Fainting

If a person experiences Hypoxia or Anoxia due to stroke, the patient also exhibits signs of unresponsiveness.

How Long Can The Brain Go Without Oxygen

When your brain experiences Hypoxia, it is reversible by providing timely treatment such as treating the stroke or offering oxygen to improve the oxygen supply to the brain. When the brain does not receive any oxygen (Cerebral Anoxia), brain death occurs within 10 – 15 minutes.


Here’s how the process progresses:

  • 30 sec – 3 mins: Lack of conscious
  • 1 minute: Gradual brain damage
  • 3 minutes: Serious brain damage begins
  • 5 minutes: Possibly the last chance of reversing brain damage
  • 10 minutes: Irreversible brain damage occurs
  • 15 minutes: If the brain cells are alive at this moment, the patient eventually slips into a coma
  • 20 minutes: Impossible to reverse brain damage


What else can cause Anoxia?

Cerebral Anoxia may be caused by other reasons like carbon monoxide poisoning or breathing in smoke. Carbon monoxide poisoning can sometimes be asymptomatic but causes death.

How is Hypoxia treated?

There is no definite treatment for Hypoxia; however, the underlying cause must be treated as soon as possible to avoid irreversible brain damage.

How does a Cardiac arrest cause Hypoxia?

The heart stops beating within 20 seconds of the cardiac arrest, and the lack of blood supply to the brain causes Hypoxia that may lead to Cerebral Anoxia.

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