How Long Can the Brain Go Without Oxygen? What Happens?

When most people think about brain injuries, they think of some form of blunt force trauma — but impact trauma is not the only potential cause of a severe brain injury. Another significant cause of brain injury is a lack of oxygen to the brain. Known as anoxic brain injuries or hypoxic brain injuries, these afflictions result from oxygen deprivation that lasts more than a few minutes.

In honor of Brain Injury Awareness Month, we’ve put together some information to help if someone you love has suffered an anoxic brain injury or cerebral hypoxia. Here are some things you should know about when the brain suffers from a lack of oxygen:

What Causes a Lack of Oxygen to the Brain?

Red blood cells are responsible for carrying oxygenated blood from the lungs through the body’s cardiovascular system and venous systems to the brain and the rest of the body. When something blocks or causes a stoppage or lack of blood flow, such as a blood clot or a prolifically bleeding wound, it prevents this critical supply of oxygen from reaching the brain.

The brain uses about 20% of the body’s oxygen supply, which allows it to perform conscious and autonomic processes.

How Long Can the Brain Go Without Oxygen? A Timeline

How long can the brain survive without oxygen? There is no one-size-fits-all answer to this question. For example, if the brain is receiving a limited supply of oxygen, it can survive longer than a brain receiving no oxygen. According to MedlinePlus, a resource of the U.S. National Library of Medicine:

“Brain cells are very sensitive to a lack of oxygen. Some brain cells start dying less than 5 minutes after their oxygen supply disappears. As a result, brain hypoxia can rapidly cause severe brain damage or death.”

When a brain goes an extended period with a lack of oxygen, neural cells begin to die through a process called apoptosis. Although some brain cell death usually occurs throughout a person’s life, large numbers of brain cells dying simultaneously can result in diminished brain function or brain death.

However, the amount of time the brain can survive without oxygen before brain damage occurs will vary from person to person. According to the University of California, Santa Barbara’s UCSB ScienceLine website, the brain can withstand three to six minutes without oxygen before brain damage occurs.

Regular training can help increase the body’s efficiency concerning oxygen consumption, allowing the brain to last for more extended periods without a fresh oxygen supply. For example, a professional freediver from Spain holds the Guinness World Record of holding his breath for 24 minutes and 3.45 seconds.

Oxygen Deprivation and Near-Death Experiences

There have been a variety of reported side effects or symptoms of a lack of oxygen to the brain. Some of these include hallucinations, delusions, and “near-death experiences.” These experiences are due to oxygen deprivation and elevated levels of carbon dioxide — a gas that is toxic in high concentrations — in the blood.

Hypoxic Brain Injuries vs. Anoxic Brain Injuries

Cerebral Hypoxia, Cerebral Anoxia, Oxygen Deprivation Infographic

Both cerebral hypoxia and anoxia are conditions that result from a lack of oxygen reaching or being absorbed by the brain. However, the difference between the two has to do with the amount of oxygen in the equation. A hypoxic brain injury occurs when there is a reduced amount of oxygen reaching or being absorbed by the brain. Anoxia, which is derived from the Greek term an, meaning ”not, without,” plus the first two letters of the word “oxygen,” followed by “ic.” This means that an anoxic brain injury occurs when the brain suffers from a complete lack of oxygen, or oxygen deprivation.

According to the Shepherd Center, different types of anoxia include:

  • Anemic Anoxia: This occurs when the red blood cells are unable to carry a sufficient amount of oxygen to the brain, or when the body lacks the blood supply to carry enough to meet the needs of the brain.
  • Anoxic Anoxia: This condition is caused by a lack of oxygen in the air for a person to consume and leads to suffocation.
  • Toxic Anoxia: This condition occurs when poisons or chemicals impede the brain from receiving necessary oxygen from the body’s red blood cells.

Causes of Cerebral Anoxia and Cerebral Hypoxia

There is a multitude of causes of anoxic and hypoxic brain injuries. According to, some of the potential causes of cerebral anoxia include:

  • A blockage of blood flow due to a blood clot or stroke
  • A severe asthma attack
  • Cardiac or respiratory arrest
  • Choking
  • Carbon monoxide or smoke inhalation
  • Drug overdose or poisoning
  • Electric shock
  • Low blood pressure resulting from disrupted cardiac function or blood loss
  • Strangulation or suffocation

According to MedlinePlus, causes of hypoxic brain injuries include:

  • A blockage of blood flow due to a blood clot or stroke
  • Carbon monoxide poisoning
  • Choking
  • Diseases and physical conditions that prevent movement (paralysis) of the breathing muscles, such as some cervical spinal cord injuries or amyotrophic lateral sclerosis (ALS)
  • High altitudes
  • Pressure or compression of the trachea
  • Smoke inhalation
  • Strangulation or blockage of the airway

What Factors Affect Brain Oxygen Deprivation Symptoms?

Medical researchers are continually seeking new and more effective ways to slow the progress of hypoxia in patients and treat various forms of brain damage. One such method is the use of cold therapy, or what is known as hypothermia treatment. This form of treatment has been used to treat brain injuries that result from trauma or a lack of oxygen for many years. The idea is that chilling the brain helps to slow metabolic processes, which reduces the amount of oxygen the brain needs to maintain body function. However, studies show a mix of positive and negative results.

Methods of treatment for hypoxic brain injuries include speech therapy, occupational and physical therapy, counseling and support groups, exercise, and nutritional counseling.

To learn more about brain injuries and traumatic brain injuries, be sure to check out our complimentary guide by clicking on the link below.


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