title: Middle cerebral artery blood velocity and cerebral blood flow and O2 uptake during dynamic exercise.
abstract: Results obtained by the 133Xe clearance method with external detectors and by transcranial Doppler sonography (TCD) suggest that dynamic exercise causes an increase of global average cerebral blood flow (CBF). These data are contradicted by earlier data obtained during less-well-defined conditions. To investigate this controversy, we applied the Kety-Schmidt technique to measure the global average levels of CBF and cerebral metabolic rate of oxygen (CMRO2) during rest and dynamic exercise. Simultaneously with the determination of CBF and CMRO2, we used TCD to determine mean maximal flow velocity in the middle cerebral artery (MCA Vmean). For values of CBF and MCA Vmean a correction for an observed small drop in arterial PCO2 was carried out. Baseline values for global CBF and CMRO2 were 50.7 and 3.63 ml.100 g-1.min-1, respectively. The same values were found during dynamic exercise, whereas a 22% (P < 0.0001) increase in MCA Vmean was observed. Hence, the exercise-induced increase in MCA Vmean is not a reflection of a proportional increase in CBF.
authors.affiliation: Department of Clinical Physiology and Nuclear Medicine, Bispebjerg Hospital, Copenhagen NV, Denmark.
authors.forename: P L
authors.initials: PL
authors.lastname: Madsen
authors.forename: B K
authors.initials: BK
authors.lastname: Sperling
authors.forename: T
authors.initials: T
authors.lastname: Warming
authors.forename: J F
authors.initials: JF
authors.lastname: Schmidt
authors.forename: N H
authors.initials: NH
authors.lastname: Secher
authors.forename: G
authors.initials: G
authors.lastname: Wildschiødtz
authors.forename: S
authors.initials: S
authors.lastname: Holm
authors.forename: N A
authors.initials: NA
authors.lastname: Lassen
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D001831:Body Temperature / Q000502:physiology; D001923:Brain Chemistry / Q000502:physiology; D002536:Cerebral Arteries / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004453:Echoencephalography; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D012146:Rest / Q000502:physiology; D014980:Xenon Radioisotopes
chemical_list: D014980:Xenon Radioisotopes