Controlled hyperventilation in fractional encephalography

Artificial hyperventilation was used during fractional encephalography. In 9 patients who underwent conventional fractional encephalography, the hyperventilation was started at the end of the investigation. In the remaining cases, in which fractional encephalography by the conventional technique gave unsatisfactory results, the examination was repeated 5 days later after mechanical hyperventilation for 30 min under intermittent positive pressure. In 3 patients with expanding processes of the posterior cranial fossa, hyperventilation encephalography confirmed the failure of passage of air into the ventricular system, and in 12 patients either visualisation or improved filling of the ventricular system and subarachnoid spaces was obtained. The great incidence of good filling of both the ventricular system and the subarachnoid spaces reduces the number of patients requiring ventriculography. Fractional encephalography following hyperventilation was well tolerated in all the patients.