<s>[INST] Hi. I hope you can me. I have a brother with lung problems. he is having problems menitally. The hospital has sent him home. They say he is not having trouble with his heart. He is on a breathing machine but menitally not doing well. How long without the right amount of oxygen will there be brain damage? [/INST] Hello. I am Chat Doctor. I have read your message. I need to know exactly what is the mental problem. To answer your question- it depends on the severity of lack of oxygen. After 1 minute, the brain cells start to die. After 3 minutes, the damage is usually serious. After 5 minutes, the damage is usually major. After 10 minutes, the damage is usually irreversible. After 15 minutes, recovery is usually not possible. Best of luck. Feel free to contact us for more information on the related issue. </s>