Acute changes in carbon dioxide levels alter the electroencephalogram without affecting cognitive function

The partial pressure of carbon dioxide in the arterial blood (PaCO2) is usu ally tightly regulated, yet it varies among healthy people at rest (range s imilar to 32-44 mmHg) as well as within an individual during many natural l ife situations. The present study examined whether modest changes in end-dd al PCO2 (PETCO2; a noninvasive measure of PaCO2) affect electroencephalogra phic (EEG) activity, cognitive function, and vigilance. Nine adults were ve ntilated mechanically using a mouthpiece; respiratory rate and breath size were held constant while PETCO2 was set to levels that produced minimal dis comfort. Despite discrete changes in EEG, neither acute PETCO2 increases (m ean = 47 mmHg) nor decreases (mean = 30 mmHg) from resting levels (mean = 3 8 mmHg) affected performance on cognitive tasks, latency or amplitude of th e N1, P2, or P3 event-related potential, or alertness. Modest changes in PE TCO2 may cause significant alterations in the EEG without disturbing cognit ive function.