New York University states that the effects of a lack of oxygen to the brain depend on severity but include difficulty paying attention, poor judgement, poor coordination, intense emotions and drowsiness. In more severe cases, the effects include seizures, loss of consciousness and difficulty breathing. If the brain goes without oxygen for more than four minutes, brain cells begin to die, and a further lack of oxygen can lead to death.
According to New York University, many conditions can lead to a lack of oxygen to the brain. Any failure of the respiratory system, whether due to injury, toxins (such as carbon monoxide), drowning or smoke inhalation can reduce the amount of oxygen entering the blood and thus reaching the brain. Disruptions to blood flow, including the blockage or rupture of blood vessels or cardiac arrest can also keep oxygen from reaching to the brain.
New York University states that diagnosis of a lack of oxygen to the brain involves a number of different tests, but the most important factor is medical history. Tests include physical exams and blood analysis. If necessary, imaging scans of the cardiac or respiratory systems also occur. Monitoring of the activity of the heart or brain via electrocardiogram and electroencaphalogram can also be helpful. Treatments must focus on both the immediate lack of oxygen and the underlying conditions.