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Changes in cerebral oxygen saturation and cerebral blood flow velocity under mild +Gz hypergravity

We previously reported that cerebral blood flow (CBF) was reduced by even mild +Gz hypergravity. Regional cerebral oxygen saturation as measured by near-infrared spectroscopy (C-rSO(2)) has been widely used to detect cerebral ischemia in clinical practice. For example, decreases in C-rSO(2) reflect...

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Autores principales: Konishi, Toru, Kurazumi, Takuya, Kato, Tomokazu, Takko, Chiharu, Ogawa, Yojiro, Iwasaki, Ken-ichi
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Physiological Society 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6692742/
https://www.ncbi.nlm.nih.gov/pubmed/31169473
http://dx.doi.org/10.1152/japplphysiol.00119.2019
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author Konishi, Toru
Kurazumi, Takuya
Kato, Tomokazu
Takko, Chiharu
Ogawa, Yojiro
Iwasaki, Ken-ichi
author_facet Konishi, Toru
Kurazumi, Takuya
Kato, Tomokazu
Takko, Chiharu
Ogawa, Yojiro
Iwasaki, Ken-ichi
author_sort Konishi, Toru
collection PubMed
description We previously reported that cerebral blood flow (CBF) was reduced by even mild +Gz hypergravity. Regional cerebral oxygen saturation as measured by near-infrared spectroscopy (C-rSO(2)) has been widely used to detect cerebral ischemia in clinical practice. For example, decreases in C-rSO(2) reflect reduced CBF or arterial oxygen saturation. Thus it was hypothesized that C-rSO(2) would decrease in association with reduced CBF during mild hypergravity. To test this hypothesis, we measured CBF velocity by transcranial Doppler ultrasonography and C-rSO(2) during mild +Gz hypergravity while participants were in a sitting position. Among 17 male participants, 15 completed 21 min of exposure to +1.5 Gz generated by short-arm centrifuge. C-rSO(2) and mean CBF velocity in the middle cerebral artery (MCBFV(MCA)) during centrifugation were averaged every 5 min and compared with pre-hypergravity (+1.0 Gz). C-rSO(2) did not change significantly throughout centrifugation, although MCBFV(MCA) gradually decreased from the beginning (−1.2% at 0–5 min), and significantly decreased at 5–10 min (−4.8%), 10–15 min (−6.7%), and 15–20 min (−7.4%). Contrary to our hypothesis, decreases in C-rSO(2) were not detected, despite reductions in CBF velocity during hypergravity. Since some assumptions, such as unaltered arteriovenous volume ratio, hemoglobin concentration, extracranial blood flow, and brain activity, need to be satisfied to monitor cerebral ischemia by C-rSO(2), the present results suggest that these necessary assumptions for near-infrared spectroscopy are not always applicable, and that cerebral oxygenation may not precisely reflect decreases in CBF under mild +Gz hypergravity. NEW & NOTEWORTHY To our knowledge, this is the first study to evaluate simultaneously cerebral oxygenation monitored by near-infrared spectroscopy and cerebral blood flow (CBF) monitored by transcranial Doppler under +1.5 Gz hypergravity. Contrary to our hypothesis, there was no significant correlation between CBF velocity and regional cerebral oxygen saturation (C-rSO(2)). However, an incomplete case nearly involving syncope suggests the possibility that C-rSO(2) can detect a remarkable decrease in CBF with development of presyncope during +Gz hypergravity.
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spelling pubmed-66927422019-08-15 Changes in cerebral oxygen saturation and cerebral blood flow velocity under mild +Gz hypergravity Konishi, Toru Kurazumi, Takuya Kato, Tomokazu Takko, Chiharu Ogawa, Yojiro Iwasaki, Ken-ichi J Appl Physiol (1985) Research Article We previously reported that cerebral blood flow (CBF) was reduced by even mild +Gz hypergravity. Regional cerebral oxygen saturation as measured by near-infrared spectroscopy (C-rSO(2)) has been widely used to detect cerebral ischemia in clinical practice. For example, decreases in C-rSO(2) reflect reduced CBF or arterial oxygen saturation. Thus it was hypothesized that C-rSO(2) would decrease in association with reduced CBF during mild hypergravity. To test this hypothesis, we measured CBF velocity by transcranial Doppler ultrasonography and C-rSO(2) during mild +Gz hypergravity while participants were in a sitting position. Among 17 male participants, 15 completed 21 min of exposure to +1.5 Gz generated by short-arm centrifuge. C-rSO(2) and mean CBF velocity in the middle cerebral artery (MCBFV(MCA)) during centrifugation were averaged every 5 min and compared with pre-hypergravity (+1.0 Gz). C-rSO(2) did not change significantly throughout centrifugation, although MCBFV(MCA) gradually decreased from the beginning (−1.2% at 0–5 min), and significantly decreased at 5–10 min (−4.8%), 10–15 min (−6.7%), and 15–20 min (−7.4%). Contrary to our hypothesis, decreases in C-rSO(2) were not detected, despite reductions in CBF velocity during hypergravity. Since some assumptions, such as unaltered arteriovenous volume ratio, hemoglobin concentration, extracranial blood flow, and brain activity, need to be satisfied to monitor cerebral ischemia by C-rSO(2), the present results suggest that these necessary assumptions for near-infrared spectroscopy are not always applicable, and that cerebral oxygenation may not precisely reflect decreases in CBF under mild +Gz hypergravity. NEW & NOTEWORTHY To our knowledge, this is the first study to evaluate simultaneously cerebral oxygenation monitored by near-infrared spectroscopy and cerebral blood flow (CBF) monitored by transcranial Doppler under +1.5 Gz hypergravity. Contrary to our hypothesis, there was no significant correlation between CBF velocity and regional cerebral oxygen saturation (C-rSO(2)). However, an incomplete case nearly involving syncope suggests the possibility that C-rSO(2) can detect a remarkable decrease in CBF with development of presyncope during +Gz hypergravity. American Physiological Society 2019-07-01 2019-06-06 /pmc/articles/PMC6692742/ /pubmed/31169473 http://dx.doi.org/10.1152/japplphysiol.00119.2019 Text en Copyright © 2019 the American Physiological Society http://creativecommons.org/licenses/by/4.0/deed.en_US Licensed under Creative Commons Attribution CC-BY 4.0 (http://creativecommons.org/licenses/by/4.0/deed.en_US) : © the American Physiological Society.
spellingShingle Research Article
Konishi, Toru
Kurazumi, Takuya
Kato, Tomokazu
Takko, Chiharu
Ogawa, Yojiro
Iwasaki, Ken-ichi
Changes in cerebral oxygen saturation and cerebral blood flow velocity under mild +Gz hypergravity
title Changes in cerebral oxygen saturation and cerebral blood flow velocity under mild +Gz hypergravity
title_full Changes in cerebral oxygen saturation and cerebral blood flow velocity under mild +Gz hypergravity
title_fullStr Changes in cerebral oxygen saturation and cerebral blood flow velocity under mild +Gz hypergravity
title_full_unstemmed Changes in cerebral oxygen saturation and cerebral blood flow velocity under mild +Gz hypergravity
title_short Changes in cerebral oxygen saturation and cerebral blood flow velocity under mild +Gz hypergravity
title_sort changes in cerebral oxygen saturation and cerebral blood flow velocity under mild +gz hypergravity
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6692742/
https://www.ncbi.nlm.nih.gov/pubmed/31169473
http://dx.doi.org/10.1152/japplphysiol.00119.2019
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