The main physiologic causes of<unk>  are related to hyperventilation.<unk>  is sometimes induced in the treatment of medical emergencies such as intracranial hypertension and hyperkalemia. Self-induced<unk>  through hyperventilation is the basis for the dangerous schoolyard fainting game. Deliberate hyperventilation has been used by underwater breath-hold divers for the purpose of extending dive time as it effectively reduces respiratory drive due to low levels. This allows one to break their standard limit of breath holding, at an increased risk of shallow water blackout (which is a significant cause of drownings). This risk is caused to due to air hunger being reduced (due to low blood carbon dioxide levels) but oxygen levels not being increased. In fact<unk>  reduces the oxygen levels available to the brain due to the elevated affinity of oxygen to hemoglobin (Bohr effect) hence highly increasing the chances of blackout.
Hypocapnia
Hypercapnia
Acidosis
Hypoventilation
Alkalosis
Hypoxemia
Hypothermia
Metabolic alkalosis