The use of carefully controlled but exaggerated ventilation to lower carbon dioxide levels in the blood and reduce cerebral blood flow; used to treat cerebral edema (e.g., after head injury). Its use remains controversial despite decades of research. Typically, the partial pressure of carbon dioxide (C02) is lowered to about 28 to 32 mm Hg. Lower levels of C02 produce reductions in cerebral blood flow that may damage the brain.