[Interrelations of hypocapnia, hypoxia, cerebral blood flow and electrical activity of the brain under voluntary hyperventilation in humans].
Changes of different physiological parameters in human caused by hyperventilation of 3-min and longer duration were investigated and correlated. It was found that during 3-min hyperventilation, resulting in 4.5-5 fold increase of the respiration velocity, similar phasing changes of the central and cerebral haemodynamics occurred. The blood flow velocity according to the rheographic data during the hyperventilation first increases, reaching maximum at 1st - 2nd min of the test, and then decreases, reaching minimum at 2nd - 3rd min after it's end, and then slowly increases. Cerebral blood flow velocity during all the 3 min of the hyperventilation in most of the subjects keeps being increased, and after the test - decreased. At the same time transcutaneous pressure of carbon dioxide changes differently - decreases to minimum (approximately 25 mmHg) at the end of the test and then increases, reaching approximately 90% of the background level, at 5th min after the end of the test. Oxygen saturation of the blood during the test is found to be 98-100% and decreases to 90% at 5th min after it's end, which in overall with cerebral blood flow decrease appears to be the factor of the brain's hypoxia. In different subjects "mirror" changes of the EEG spectral power of different EEG ranges in relation to transcutaneous pressure of carbon dioxide dynamics were revealed by the hyperventilation. Taking into account the factors of duration or recurrence of the hyperventilation is important for the understanding the interrelations of cerebral haemodynamics, hypocapnia, hypoxia and electrical activity of the brain. It was found that after the recurrent hyperventilation of increasing amount (several times in hour by 3 min) cerebral blood flow might decrease markedly against the background of relatively small changes of electrical activity of the brain. The discussing of the data presented in the paper is carried out from the point of view of important role of tissue oxygen utilization mechanisms of the brain in adaptation to hypoxia and hypocapnia.
Burykh
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EA
D000328:Adult; D000513:Alpha Rhythm; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D002531:Cerebellum / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004594:Electrophysiology; D005260:Female; D006801:Humans; D006985:Hyperventilation; D016857:Hypocapnia / Q000503:physiopathology*; D002534:Hypoxia, Brain / Q000503:physiopathology*; D008297:Male; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption / Q000502:physiology
D010100:Oxygen