Arterial Oxygen Saturation and Alveolar Carbon Dioxide During Electroencephalography

An investigation of the usefulness of induced hypoxia as an activation technique in electroencephalography will be reported in this and in following communications. Arterial oxygen saturation and, in most instances, alveolar carbon dioxide content (CO2) have been recorded concurrently with the EEG in 108 human subjects during induction of hypoxia by means of the inhalation of gas mixtures low in oxygen. Observations in normal subjects will be reported in this paper. Subsequent papers will present observations in subjects suffering from various types of epilepsy21and cerebrovascular disease.22 A comparison of the EEG effects of hypoxia and other commonly used activation techniques was undertaken in this group of subjects for a number of reasons. Cerebral hypoxia induced by breath holding has been reported to be a useful activation technique by several investigators,2,11,17,27but many patients are unable to hold their breath sufficiently long to induce EEG changes.