Rapid magnetic resonance measurement of global cerebral metabolic rate of oxygen consumption in humans during rest and hypercapnia

Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism (Impact Factor: 5.41). 04/2011; 31(7):1504-12. DOI: 10.1038/jcbfm.2011.34
Source: PubMed


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.

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Available from: Felix W Wehrli, Jan 09, 2015
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    • "Some of this inconsistency in results between human and animal studies can be attributed to the different physiological conditions under which the experiments were performed. However, the data in Jain et al (2011), Chen and Pike (2010) and Xu et al (2011) were obtained in normal awake humans, and one can only speculate that differences should be attributed to differences in experimental techniques. Substantial progress has been made in developing in vivo methods to study brain metabolism and hemodynamics since the initial publication (Kety and Schmidt, 1948), and the paper by Jain et al contributes significantly to this development. "
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    ABSTRACT: Journal of Cerebral Blood Flow & Metabolism stands at the interface between basic and clinical neurovascular research, and features research on experimental, theoretical, and clinical aspects of brain circulation, metabolism and imaging. The journal is relevant to any physician or scientist with an interest in brain function, cerebrovascular disease, cerebral vascular regulation and brain metabolism, including neurologists, neurochemists, physiologists, pharmacologists, anesthesiologists, neuroradiologists, neurosurgeons, neuropathologists and neuroscientists.
    Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 03/2011; 31(7):1502-3. DOI:10.1038/jcbfm.2011.32 · 5.41 Impact Factor
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    ABSTRACT: In functional magnetic resonance imaging (fMRI), the blood oxygenation level dependent (BOLD) signal is often interpreted as a measure of neural activity. However, because the BOLD signal reflects the complex interplay of neural, vascular, and metabolic processes, such an interpretation is not always valid. There is growing evidence that changes in the baseline neurovascular state can result in significant modulations of the BOLD signal that are independent of changes in neural activity. This paper introduces some of the normalization and calibration methods that have been proposed for making the BOLD signal a more accurate reflection of underlying brain activity for human fMRI studies.
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    ABSTRACT: Noninvasive magnetic resonance (MR) methods have been explored to provide quantitative measurements of cerebral blood flow (CBF), oxygen extraction fraction (OEF), and oxygen metabolic index (OMI = CBF × OEF). In this study, we sought to evaluate whether MR measured OEF, CBF, and OMI can consistently detect the expected physiological changes in humans under normal and hyperoxic hypercapnic conditions. Nine healthy human subjects were scanned while breathing through a mask, alternating inhaled gas in a sequential order as room air, carbogen (3% CO2 mixed with 97% O2), room air, carbogen, and room air. OEF, CBF, and OMI were obtained from the whole brain, gray matter (GM), and white matter (WM) at each gas inhalation state. Similar to previous positron emission tomography findings, our study consistently demonstrated a 10–12% decrease in OEF with a 10% increase of CBF and a stable OMI during carbogen inhalation. Moreover, GM/WM ratio in CBF and OMI remained constant during air and carbogen breathing. In addition, OEF, CBF, and OMI were highly reproducible if the same inhaled gas was used. In summary, our results demonstrate that noninvasive MR measurements can provide reproducible measurements of OEF, CBF, and OMI in normal subjects under normal and altered physiological conditions.
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