Because hyperventilation is often associated with a rapid fall in intracranial pressure, it has been assumed to be effective in the treatment of severe head injury. Hyperventilation reduces raised intracranial pressure by causing cerebral vasoconstriction and a reduction in cerebral blood flow. Whether reduced cerebral blood flow improves neurological outcome however, is unclear.
Roberts, I., & Schierhout, G. (1997). Hyperventilation therapy for acute traumatic brain injury. Cochrane Database of Systematic Reviews. https://doi.org/10.1002/14651858.cd000566