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Citation
Tags
HERO ID
5421604
Reference Type
Journal Article
Title
The effect of isocapnic hyperoxia on neurophysiology as measured with MRI and MEG
Author(s)
Croal, PL; Hall, EL; Driver, ID; Brookes, MJ; Gowland, PA; Francis, ST
Year
2015
Is Peer Reviewed?
1
Journal
NeuroImage
ISSN:
1053-8119
EISSN:
1095-9572
Volume
105
Page Numbers
323-331
Language
English
PMID
25462687
DOI
10.1016/j.neuroimage.2014.10.036
Web of Science Id
WOS:000346050300031
Abstract
The physiological effect of hyperoxia has been poorly characterize d, with studies reporting conflicting results on the role of hyperoxia as a vasoconstrictor. It is not clear whether hyperoxia is the primary contributor to vasoconstriction or whether induced changes in CO2 that commonly accompany hyperoxia are a factor. As calibrated BOLD fMRI based on hyperoxia becomes more widely used, it is essential to understand the effects of oxygen on resting cerebral physiology. This study used a RespirAct™ system to deliver a repeatable isocapnic hyperoxia stimulus to investigate the independent effect of O2 on cerebral physiology, removing any potential confounds related to altered CO2. T1-independent Phase Contrast MRI was used to demonstrate that isocapnic hyperoxia has no significant effect on carotid blood flow (normoxia 201 ± 11 ml/min, -0.3% ± 0.8% change during hyperoxia, p = 0.8), while Look Locker ASL was used to demonstrate that there is no significant change in arterial cerebral blood volume (normoxia 1.3% ± 0.4%, -0.5 ± 5% change during hyperoxia). These are in contrast to significant changes in carotid blood flow observed for hypercapnia (6.8% ± 1.5%/mm Hg CO2). In addition, magnetoencephalography provided a method to monitor the effect of isocapnic hyperoxia on neuronal oscillatory power. In response to hyperoxia, a significant focal decrease in oscillatory power was observed across the alpha, beta and low gamma bands in the occipital lobe, compared to a more global significant decrease on hypercapnia. This work suggests that isocapnic hyperoxia provides a more reliable stimulus than hypercapnia for calibrated BOLD, and that previous reports of vasoconstriction during hyperoxia probably reflect the effects of hyperoxia-induced changes in CO2. However, hyperoxia does induce changes in oscillatory power consistent with an increase in vigilance, but these changes are smaller than those observed under hypercapnia. The effect of this change in neural activity on calibrated BOLD using hyperoxia or combined hyperoxia and hypercapnia needs further investigation.
Keywords
Hyperoxia; Magnetoencephalography; BOLD; fMRI; Cerebral blood flow; Cerebral blood volume; Neural oscillations
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