The relationship between widespread changes in gravity and cerebral blood flow

Ogawa, Yutaka; Yanagida, Ryo; Ueda, Kaname; Aoki, Ken; Iwasaki, Kazuo

doi:10.1007/s12199-016-0513-7

Cited by 14 publications

(11 citation statements)

References 23 publications

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“…Although intermittent and repeated exposure to artificial hypergravity via a human centrifuge has been proposed as a countermeasure against spaceflight-induced physiological deconditioning (7, 10), in the present study, MCBFV MCA was significantly decreased under even mild +Gz hypergravity, which was consistent with our previous reports (15, 20, 24). Hence, the decreases in CBF were thought to be one of the adverse effects during even mild centrifugation, suggesting that careful monitoring of CBF is needed during the exposure.…”

Section: Discussionsupporting

confidence: 93%

“…In contrast to previous studies (15, 20, 24), we selected laymen who had no experience in a centrifuge as participants in the present study to detect physiological changes under mild hypergravity more clearly. As expected, many more data segments and indexes showed statistically significant differences in post hoc tests in the present study compared with previous studies.…”

Section: Discussionmentioning

confidence: 99%

“…Understanding the physiological changes experienced by humans during exposure to mild +Gz hypergravity is therefore important for understanding various situations, as well as for the future implementation of human centrifuges (10). We previously reported that cerebral blood flow (CBF) as measured by transcranial Doppler ultrasonography (TCD) was significantly reduced under even mild +Gz hypergravity, and did not lead to any changes in arterial blood pressure (ABP) at heart level (15, 20, 24).…”

Section: Introductionmentioning

confidence: 99%

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

Konishi

Kurazumi

Kato

et al. 2019

Journal of Applied Physiology

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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-rSO2) has been widely used to detect cerebral ischemia in clinical practice. For example, decreases in C-rSO2 reflect reduced CBF or arterial oxygen saturation. Thus it was hypothesized that C-rSO2 would decrease in association with reduced CBF during mild hypergravity. To test this hypothesis, we measured CBF velocity by transcranial Doppler ultrasonography and C-rSO2 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-rSO2 and mean CBF velocity in the middle cerebral artery (MCBFVMCA) during centrifugation were averaged every 5 min and compared with pre-hypergravity (+1.0 Gz). C-rSO2 did not change significantly throughout centrifugation, although MCBFVMCA 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-rSO2 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-rSO2, 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-rSO2). However, an incomplete case nearly involving syncope suggests the possibility that C-rSO2 can detect a remarkable decrease in CBF with development of presyncope during +Gz hypergravity.

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Konishi

Kurazumi

Kato

et al. 2019

Journal of Applied Physiology

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“…For example, body fluids might be pulled towards the legs during deceleration, since most race-car seats recline deeply. This gravitational loading would augment venous pooling in the lower body and reduce central blood volume and stroke volume, resulting in a reflex increase in HR similar to gravitational loading by centrifugation [16,17].…”

Section: Gravitational Loadingmentioning

confidence: 99%

Speed ratio but cabin temperature positively correlated with increased heart rates among professional drivers during car races

Yanagida

Takahashi²,

Miura

et al. 2016

Environ Health Prev Med

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The cardiovascular system of drivers is considerably stressed at extremely high HR. This high average HR positively correlated with mean speed ratio, suggesting that faster driving speed would induce greater cardiovascular stress to professional drivers during actual races. However, contrary to our hypothesis, cabin temperature was not significantly correlated with average HR. It is speculated that direct body cooling systems used in this professional race category work well against increases in HR by thermal stress under the temperature range found herein.

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“…The study of the adaptation of the organism to external factors, including gravitational overloads, is an actual medical and biological problem. Overloads cause hemodynamic changes and respiratory disturbances as well as lead to a complex of physiological reactions known as "general adaptation syndrome" [1,2]. Like any impact, hypergravity has a certain dose-dependent effect.…”

Section: Introductionmentioning

confidence: 99%

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2018

Russ Open Med J

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Aim of this study was to assess morphofunctional transformations in the adrenal glands of juvenile rats systematically exposed to +Gx acceleration. Material and Methods -Rats in the experimental group were exposed to transversely-directed gravitational overloads (9 G) produced by experimental centrifuge C-2/500 (three times, each time 3 minutes exposure with 30 seconds break between sets). Microscopical, histomorphometric (thickness of cortical zones; cortex-medulla ratio; absolute and relative area of zona glomerulosa, zona fasciculate, zona reticularis, and medulla; number and density of cells in each zone; area of nuclei, cytoplasm and liposomes in endocrinocytes), ultrastructural and statistical methods were used. Results -Structural transformations found in adrenal glands are adaptive responses to stress and hemodynamic changes caused by systematic influence of gravitational overloads. The expressed hemodynamic changes combined with stress-induced morphofunctional transformations, manifested as signs of functional stress of cortical and medullar endocrinocytes on the background of dystrophic and destructive ultrastructural changes were revealed. Increase of number of exposures to 45 leads to further stabilization of morphofunctional condition of adrenal glands. Conclusion -Structural transformations and features of the functional tension of the cortical and medullary endocrinocytes are limited as "systemic structural trace".

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The relationship between widespread changes in gravity and cerebral blood flow

Cited by 14 publications

References 23 publications

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

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

Speed ratio but cabin temperature positively correlated with increased heart rates among professional drivers during car races

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