Changes in the loco-regional cerebral blood flow (r.C.B.F.) during a simulation of weightlessness

Güell, A; Dupui, Philippe; Barrère, Michel; Fanjaud, G; A, Bes; Kotowskaia, A

doi:10.1016/0094-5765(82)90049-2

Cited by 6 publications

(6 citation statements)

References 3 publications

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“…Few studies have measured regional (r) CBF in humans after exposure to simulated microgravity. Guell et al (1982) found in healthy volunteers who underwent −4° HDBR for 7 days, an increase in regional cerebral blood flow (rCBF; measured by 133 Xe inhalation method) after 6 h, but returned to the baseline state at 72 h (Guell et al, 1982). No study has so far measured rCBF both during spaceflight and microgravity analogs such as DI.…”

Section: Introductionmentioning

confidence: 99%

Reduced Regional Cerebral Blood Flow Measured by 99mTc-Hexamethyl Propylene Amine Oxime Single-Photon Emission Computed Tomography in Microgravity Simulated by 5-Day Dry Immersion

et al. 2021

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Microgravity induces a cephalad fluid shift that is responsible for cephalic venous stasis that may increase intracranial pressure (ICP) in astronauts. However, the effects of microgravity on regional cerebral blood flow (rCBF) are not known. We therefore investigated changes in rCBF in a 5-day dry immersion (DI) model. Moreover, we tested thigh cuffs as a countermeasure to prevent potential microgravity-induced modifications in rCBF. Around 18 healthy male participants underwent 5-day DI with or without a thigh cuffs countermeasure. They were randomly allocated to a control (n=9) or cuffs (n=9) group. rCBF was measured 4days before DI and at the end of the fifth day of DI (DI5), using single-photon emission computed tomography (SPECT) with radiopharmaceutical 99mTc-hexamethyl propylene amine oxime (99mTc-HMPAO). SPECT images were processed using statistical parametric mapping (SPM12) software. At DI5, we observed a significant decrease in rCBF in 32 cortical and subcortical regions, with greater hypoperfusion in basal ganglia (right putamen peak level: z=4.71, puncorr<0.001), bilateral occipital regions (left superior occipital peak level: z=4.51, puncorr<0.001), bilateral insula (right insula peak level: 4.10, puncorr<0.001), and bilateral inferior temporal (right inferior temporal peak level: 4.07, puncorr<0.001). No significant difference was found between the control and cuffs groups on change in rCBF after 5days of DI. After a 5-day DI, we found a decrease in rCBF in cortical and subcortical regions. However, thigh cuffs countermeasure failed to prevent hypoperfusion. To date, this is the first study measuring rCBF in DI. Further investigations are needed in order to better understand the underlying mechanisms in cerebral blood flow (CBF) changes after exposure to microgravity.

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Section: Introductionmentioning

confidence: 99%

Reduced Regional Cerebral Blood Flow Measured by 99mTc-Hexamethyl Propylene Amine Oxime Single-Photon Emission Computed Tomography in Microgravity Simulated by 5-Day Dry Immersion

et al. 2021

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“…No previous study had previously measured rCBF in humans after microgravity simulation by DI. A study in HDBR measuring rCBF with the 133 Xe inhalation method found an initial increase at 6 hours, but no difference at 72 hours [10]. Some studies measuring rCBF have been performed in animals.…”

Section: Discussionmentioning

confidence: 99%

“…Few studies have measured regional (r) CBF in humans after exposure to simulated microgravity. In a study in head-down bed rest (HDBR), rCBF measured by 133 Xe inhalation method had increased at 6 hours, but returned to the baseline state at 72 hours [10]. No study has so far measured rCBF during both space ight and microgravity analogues such as dry immersion (DI).…”

Section: Introductionmentioning

confidence: 99%

Reduced regional cerebral blood flow measured by 99mTc-HMPAO SPECT in microgravity simulated by 5-day dry immersion

Guillon¹,

Kermorgant²,

Charvolin³

et al. 2021

Preprint

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Purpose Neuro-ophthalmological changes defined as spaceflight-associated neuro-ocular syndrome have been reported after long duration space flights. The pathophysiology of this syndrome remains unclear, with the possible involvement of elevated intracranial pressure. Changes in blood flow in the brain, evaluated indirectly by Doppler, have been reported in flight. However, the effects of microgravity on regional cerebral blood flow (rCBF) are not known. We therefore investigated changes in rCBF in a 5-day dry immersion (DI) model. Moreover, we tested thigh cuffs as a countermeasure to prevent potential microgravity-induced modifications in rCBF.Methods 18 healthy male participants underwent 5-day DI with or without a thigh cuffs countermeasure. They were randomly allocated to a control (n = 9) or cuffs (n = 9) group. rCBF was measured 4 days before DI (Pre-DI) and at the end of the fifth day of DI (Post-DI), using single-photon emission computed tomography (SPECT) with radiopharmaceutical 99mTc-hexamethyl propylene amine oxime (HMPAO). SPECT images were processed using statistical parametric mapping (SPM12) software.Results At DI5, we observed a significant decrease in rCBF in 32 cortical and subcortical patterns, with greater hypoperfusion in the occipital region (occipital peak level: z = 4.51, puncorr < 0.001) and basal ganglia (putamen peak level: z = 4.71, puncorr < 0.001; caudate nuclei peak level: z = 3.80, puncorr < 0.001). No significant difference was found between the control and cuffs groups on variations in rCBF at DI5.Conclusion 5-day DI induces a relative decrease in rCBF in cortical and subcortical regions. Nevertheless, the consequences of this decrease for brain function and mechanisms need further investigation.

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“…Guell et al (1979) observed in four healthy subjects who underwent 4° HDT for 7 days, a rapid decrease in loco -regional CBF after 2 h followed by an increase after 48 h. In a similar study, these same authors only found in six healthy subjects an elevation in loco -regional CBF ( Guell et al, 1982 ). These differences may be explained by the techniques used to measure loco-regional CBF which were different between these studies (respectively measured by transcranial Doppler and Xenon-133 techniques).…”

Section: Impacts Of Spaceflight Analogs On Cerebral Autoregulationmentioning

confidence: 90%

Impacts of Microgravity Analogs to Spaceflight on Cerebral Autoregulation

et al. 2020

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It is well known that exposure to microgravity in astronauts leads to a plethora physiological responses such as headward fluid shift, body unloading, and cardiovascular deconditioning. When astronauts return to Earth, some encounter problems related to orthostatic intolerance. An impaired cerebral autoregulation (CA), which could be compromised by the effects of microgravity, has been proposed as one of the mechanisms responsible for orthostatic intolerance. CA is a homeostatic mechanism that maintains cerebral blood flow for any variations in cerebral perfusion pressure by adapting the vascular tone and cerebral vessel diameter. The groundbased models of microgravity are useful tools for determining the gravitational impact of spaceflight on human body. The head-down tilt bed rest (HDTBR), where the subject remains in supine position at −6 degrees for periods ranging from few days to several weeks is the most commonly used ground-based model of microgravity for cardiovascular deconditioning. head-down bed rest (HDBR) is able to replicate cephalic fluid shift, immobilization, confinement, and inactivity. Dry immersion (DI) model is another approach where the subject remains immersed in thermoneutral water covered with an elastic waterproof fabric separating the subject from the water. Regarding DI, this analog imitates absence of any supporting structure for the body, centralization of body fluids, immobilization and hypokinesia observed during spaceflight. However, little is known about the impact of microgravity on CA. Here, we review the fundamental principles and the different mechanisms involved in CA. We also consider the different approaches in order to assess CA. Finally, we focus on the effects of short-and long-term spaceflight on CA and compare these findings with two specific analogs to microgravity: HDBR and DI.

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Changes in the loco-regional cerebral blood flow (r.C.B.F.) during a simulation of weightlessness

Cited by 6 publications

References 3 publications

Reduced Regional Cerebral Blood Flow Measured by 99mTc-Hexamethyl Propylene Amine Oxime Single-Photon Emission Computed Tomography in Microgravity Simulated by 5-Day Dry Immersion

Reduced Regional Cerebral Blood Flow Measured by 99mTc-Hexamethyl Propylene Amine Oxime Single-Photon Emission Computed Tomography in Microgravity Simulated by 5-Day Dry Immersion

Reduced regional cerebral blood flow measured by 99mTc-HMPAO SPECT in microgravity simulated by 5-day dry immersion

Impacts of Microgravity Analogs to Spaceflight on Cerebral Autoregulation

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