Blood Sugar Level and Influence of Hyperventilation on Slow Activity in Electroencephalogram

Abstract

Interest has recently been focused on the relationship which seems to exist between slow potential changes appearing in the electroencephalogram (EEG) on hyperveiltilation and alterations in blood sugar level.'* If a direct relationship between the two does exist, it will be necessary systematically to control the blood sugar level in all hyperventilation studies. it is not easy to maintain such a control, and before the electroencephalographer becomes burdened with this precaution, it seemed desirable to investigate the possible relationship further.Methods. One physically healthy, schizophrenic patient was observed on 10 different occasions* over a period of 10 weeks.Three glucose and 7 insulin (3. 5, 10 U ) tolerance tests were given.Preceding the collection of each blood sample an EEG was obtained in the following iiianner: j meters of control record were followed by a 2-minute hyperventilation (at a regular rate of 30 deep respirations per minute), and the record allowed to return to its initial level. In this n a -, inany hyperventilation records at various blood sugar levels were obtained.Slow activity in the EEG was considered to include all waves with a frequency below 8 per second, and was qualified as total slow activity in the 7-meter period, which included the hyperventilation and recovery portions of the record. Fig. 1 A shows a definite inverse relationship between bIood sugar and sIow activity. Fig. 1 B, however, is typical of the remainder of our data. Here slow activity is inversely related to blood sugar only at 30 and at 90 minutes. In addition, it may be noted that the minimum amount of slow activity does not correspond with the maximum blood sugar value.When all the blood sugar values obtained were plotted against the corresponding amounts of slow activity, an apparent relation-Resalts.

Electroencephalographic Activity During Voluntarily Controlled Alveolar Hyperventilation

“…The blood sugar measurements were made because it is widely held that the level of circulating blood sugar is an important factor in determining the appearance of delta rhythm. It is considered that a high blood sugar level allows the brain tissue to function normally in the presence of hypoxia and hypocapnia (Davis and Wallace, 1941;Rubin and Turner, 1942;Brazier, Finesinger and Schwab, 1944). Davis (1941) showed that hypoglycaemia without hyperventilation could itself produce delta rhythm.…”

Neurophysiological Mechanisms Underlying the Action of Hypo- and Hyperglycemia in some Clinical Conditions

“…It must, however, be taken into consideration that the increased respiration may lead to an acapnia great enough to cause a marked reduction in brain circulation [16]. The finding that even mild degress of hypoglycemia intensify the production of slow potentials in the EEG induced by hyperventilation [28] greatly strengthen this interpretation. It is believed that these mechanisms account for the occurrence of episodes of hyperventilation in cases of clinical hypoglyce mia and that the combination of hypoglycemia and cerebral anoxia evokes strong ergotropic discharges (ergotropic tuning) leading to anxiety and related states.…”