According to the article I provided, brain damage is possible, it is called anoxia.
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This type of brain injury (encephalopathy) is caused by partial (hypoxia) or total (anoxia) deprivation of the brain's oxygen supply for longer than the compensatory mechanisms designed to prevent neuronal death can cope.
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TOXIC Anoxia caused by toxins or substances that interfere with the use of oxygen.
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The clinical spectrum of this disease is highly variable, ranging from isolated cognitive disorders to symptoms compatible with brain death. This disease, especially when compared with other aetiologies, generally leads to a high rate of disability and dependence among survivors."
Irenea is a highly specialised centre in rehabilitation of people with acquired brain injury or other neurological disabilities
neurorhb.com