title: The effects of altered intrathoracic pressure on resting cerebral blood flow and its response to visual stimulation.
abstract: Investigating how intrathoracic pressure changes affect cerebral blood flow (CBF) is important for a clear interpretation of neuroimaging data in patients with abnormal respiratory physiology, intensive care patients receiving mechanical ventilation and in research paradigms that manipulate intrathoracic pressure. Here, we investigated the effect of experimentally increased and decreased intrathoracic pressures upon CBF and the stimulus-evoked CBF response to visual stimulation. Twenty healthy volunteers received intermittent inspiratory and expiratory loads (plus or minus 9cmH2O for 270s) and viewed an intermittent 2Hz flashing checkerboard, while maintaining stable end-tidal CO2. CBF was recorded with transcranial Doppler sonography (TCD) and whole-brain pseudo-continuous arterial spin labeling magnetic resonance imaging (PCASL MRI). Application of inspiratory loading (negative intrathoracic pressure) showed an increase in TCD-measured CBF of 4% and a PCASL-measured increase in grey matter CBF of 5%, but did not alter mean arterial pressure (MAP). Expiratory loading (positive intrathoracic pressure) did not alter CBF, while MAP increased by 3%. Neither loading condition altered the perfusion response to visual stimulation in the primary visual cortex. In both loading conditions localized CBF increases were observed in the somatosensory and motor cortices, and in the cerebellum. Altered intrathoracic pressures, whether induced experimentally, therapeutically or through a disease process, have possible significant effects on CBF and should be considered as a potential systematic confound in the interpretation of perfusion-based neuroimaging data.
authors.affiliation: Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK. Electronic address: anja.hayen@ndcn.ox.ac.uk.
authors.forename: Anja
authors.initials: A
authors.lastname: Hayen
authors.affiliation: Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK. Electronic address: mari.herigstad@ndcn.ox.ac.uk.
authors.forename: Mari
authors.initials: M
authors.lastname: Herigstad
authors.affiliation: Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK. Electronic address: mkelly@fmrib.ox.ac.uk.
authors.forename: Michael
authors.initials: M
authors.lastname: Kelly
authors.affiliation: Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK. Electronic address: tokell@fmrib.ox.ac.uk.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Okell
authors.affiliation: Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Park Place, CF10 3AT, Cardiff, UK. Electronic address: murphyk2@cardiff.ac.uk.
authors.forename: Kevin
authors.initials: K
authors.lastname: Murphy
authors.affiliation: Cardiff University Brain Research Imaging Centre (CUBRIC), School of Psychology, Cardiff University, Park Place, CF10 3AT, Cardiff, UK. Electronic address: WiseRG@cardiff.ac.uk.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Wise
authors.affiliation: Nuffield Division of Anaesthetics and Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB), Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK. Electronic address: kyle.pattinson@ndcn.ox.ac.uk.
authors.forename: Kyle T S
authors.initials: KT
authors.lastname: Pattinson
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010775:Photic Stimulation; D011312:Pressure; D012143:Respiratory Physiological Phenomena; D013113:Spin Labels; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D013113:Spin Labels
keywords: Arterial spin labeling; Cerebral blood flow; Dyspnea; Functional magnetic resonance imaging; Respiratory loading; Transcranial Doppler sonography