title: Rapid magnetic resonance measurement of global cerebral metabolic rate of oxygen consumption in humans during rest and hypercapnia.
abstract: The effect of hypercapnia on cerebral metabolic rate of oxygen consumption (CMRO(2)) has been a subject of intensive investigation and debate. Most applications of hypercapnia are based on the assumption that a mild increase in partial pressure of carbon dioxide has negligible effect on cerebral metabolism. In this study, we sought to further investigate the vascular and metabolic effects of hypercapnia by simultaneously measuring global venous oxygen saturation (S(v)O(2)) and total cerebral blood flow (tCBF), with a temporal resolution of 30 seconds using magnetic resonance susceptometry and phase-contrast techniques in 10 healthy awake adults. While significant increases in S(v)O(2) and tCBF were observed during hypercapnia (P<0.005), no change in CMRO(2) was noted (P>0.05). Additionally, fractional changes in tCBF and end-tidal carbon dioxide (R(2)=0.72, P<0.005), as well as baseline S(v)O(2) and tCBF (R(2)=0.72, P<0.005), were found to be correlated. The data also suggested a correlation between cerebral vascular reactivity (CVR) and baseline tCBF (R(2)=0.44, P=0.052). A CVR value of 6.1%±1.6%/mm Hg was determined using a linear-fit model. Additionally, an average undershoot of 6.7%±4% and 17.1%±7% was observed in S(v)O(2) and tCBF upon recovery from hypercapnia in six subjects.
authors.affiliation: Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Varsha
authors.initials: V
authors.lastname: Jain
authors.forename: Michael C
authors.initials: MC
authors.lastname: Langham
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Floyd
authors.forename: Gaurav
authors.initials: G
authors.lastname: Jain
authors.forename: Jeremy F
authors.initials: JF
authors.lastname: Magland
authors.forename: Felix W
authors.initials: FW
authors.lastname: Wehrli
mesh_terms: D000328:Adult; D001481:Basal Metabolism; D001921:Brain / Q000098:blood supply / Q000378:metabolism / Q000473:pathology; D002245:Carbon Dioxide / Q000097:blood / Q000378:metabolism; D002560:Cerebrovascular Circulation; D006801:Humans; D006935:Hypercapnia / Q000097:blood / Q000378:metabolism*; D008279:Magnetic Resonance Imaging / Q000191:economics / Q000379:methods*; D008297:Male; D010100:Oxygen / Q000097:blood* / Q000378:metabolism; D010101:Oxygen Consumption; D012146:Rest / Q000502:physiology*; D013997:Time Factors; D055815:Young Adult
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen