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Sagirov AF, Sergeev TV, Shabrov AV, Yurov AY, Guseva NL, Agapova EA. Postural influence on intracranial fluid dynamics: an overview. J Physiol Anthropol 2023; 42:5. [PMID: 37055862 PMCID: PMC10100470 DOI: 10.1186/s40101-023-00323-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Accepted: 04/01/2023] [Indexed: 04/15/2023] Open
Abstract
This review focuses on the effects of different body positions on intracranial fluid dynamics, including cerebral arterial and venous flow, cerebrospinal fluid (CSF) hydrodynamics, and intracranial pressure (ICP). It also discusses research methods used to quantify these effects. Specifically, the implications of three types of body positions (orthostatic, supine, and antiorthostatic) on cerebral blood flow, venous outflow, and CSF circulation are explored, with a particular emphasis on cerebrovascular autoregulation during microgravity and head-down tilt (HDT), as well as posture-dependent changes in cerebral venous and CSF flow, ICP, and intracranial compliance (ICC). The review aims to provide a comprehensive analysis of intracranial fluid dynamics during different body positions, with the potential to enhance our understanding of intracranial and craniospinal physiology.
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Affiliation(s)
- Arlan Faritovich Sagirov
- Department of Ecological Physiology, Federal State Budgetary Scientific Institution "Institute of Experimental Medicine", 12 Academic Pavlov St, Saint-Petersburg, 197022, Russia.
| | - Timofey Vladimirovich Sergeev
- Department of Ecological Physiology, Federal State Budgetary Scientific Institution "Institute of Experimental Medicine", 12 Academic Pavlov St, Saint-Petersburg, 197022, Russia
| | - Aleksandr Vladimirovich Shabrov
- Department of Ecological Physiology, Federal State Budgetary Scientific Institution "Institute of Experimental Medicine", 12 Academic Pavlov St, Saint-Petersburg, 197022, Russia
| | - Andrey Yur'evich Yurov
- Department of Ecological Physiology, Federal State Budgetary Scientific Institution "Institute of Experimental Medicine", 12 Academic Pavlov St, Saint-Petersburg, 197022, Russia
| | - Nadezhda Leonidovna Guseva
- Department of Ecological Physiology, Federal State Budgetary Scientific Institution "Institute of Experimental Medicine", 12 Academic Pavlov St, Saint-Petersburg, 197022, Russia
| | - Elizaveta Aleksandrovna Agapova
- Department of Ecological Physiology, Federal State Budgetary Scientific Institution "Institute of Experimental Medicine", 12 Academic Pavlov St, Saint-Petersburg, 197022, Russia
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Ikidag MA, Firat YE. Comparison of carotid and vertebral artery doppler measurements in supine and sitting positions. Niger J Clin Pract 2022; 25:1883-1888. [DOI: 10.4103/njcp.njcp_326_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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3
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Xing C, Gao Y, Wang X, Xing W, Liu Y, Lei Y, Zhang X, Zhang S, Yuan L, Gao F. Cuff-Method Thigh Arterial Occlusion Counteracts Cerebral Hypoperfusion Against the Push-Pull Effect in Humans. Front Physiol 2021; 12:672351. [PMID: 34220534 PMCID: PMC8243772 DOI: 10.3389/fphys.2021.672351] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 04/29/2021] [Indexed: 11/24/2022] Open
Abstract
Exposure to acute transition from negative (−Gz) to positive (+ Gz) gravity significantly impairs cerebral perfusion in pilots of high-performance aircraft during push—pull maneuver. This push—pull effect may raise the risk for loss of vision or consciousness. The aim of the present study was to explore effective countermeasures against cerebral hypoperfusion induced by the push—pull effect. Twenty healthy young volunteers (male, 21 ± 1 year old) were tested during the simulated push–pull maneuver by tilting. A thigh cuff (TC) pressure of 200 mmHg was applied before and during simulated push—pull maneuver (−0.87 to + 1.00 Gz). Beat-to-beat cerebral and systemic hemodynamics were measured continuously. During rapid −Gz to + Gz transition, mean cerebral blood flow velocity (CBFV) was decreased, but to a lesser extent, in the TC bout compared with the control bout (−3.1 ± 4.9 vs. −7.8 ± 4.4 cm/s, P < 0.001). Similarly, brain-level mean blood pressure showed smaller reduction in the TC bout than in the control bout (−46 ± 12 vs. −61 ± 13 mmHg, P < 0.001). The systolic CBFV was lower but diastolic CBFV was higher in the TC bout. The systemic blood pressure response was blunted in the TC bout, along with similar heart rate increase, smaller decrease, and earlier recovery of total peripheral resistance index than control during the gravitational transition. These data demonstrated that restricting thigh blood flow can effectively mitigate the transient cerebral hypoperfusion induced by rapid shift from −Gz to + Gz, characterized by remarkable improvement of cerebral diastolic flow.
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Affiliation(s)
- Changyang Xing
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, China.,Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Yuan Gao
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, China
| | - Xinpei Wang
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, China
| | - Wenjuan Xing
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, China
| | - Yunnan Liu
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Yujia Lei
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Xing Zhang
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, China
| | - Shu Zhang
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, China
| | - Lijun Yuan
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, China
| | - Feng Gao
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, China
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Kermorgant M, Nasr N, Czosnyka M, Arvanitis DN, Hélissen O, Senard JM, Pavy-Le Traon A. Impacts of Microgravity Analogs to Spaceflight on Cerebral Autoregulation. Front Physiol 2020; 11:778. [PMID: 32719617 PMCID: PMC7350784 DOI: 10.3389/fphys.2020.00778] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 06/15/2020] [Indexed: 12/16/2022] Open
Abstract
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 ground-based 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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Affiliation(s)
- Marc Kermorgant
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
| | - Nathalie Nasr
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
- Department of Neurology, Institute for Neurosciences, Toulouse University Hospital, Toulouse, France
| | - Marek Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge University Hospital, Cambridge, United Kingdom
- Institute of Electronic Systems, Warsaw University of Technology, Warsaw, Poland
| | - Dina N. Arvanitis
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
| | - Ophélie Hélissen
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
| | - Jean-Michel Senard
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
- Department of Clinical Pharmacology, Toulouse University Hospital, Toulouse, France
| | - Anne Pavy-Le Traon
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
- Department of Neurology, Institute for Neurosciences, Toulouse University Hospital, Toulouse, France
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Xing C, Wang X, Gao Y, Zhang J, Liu Y, Guo Y, Wang C, Feng Y, Lei Y, Zhang X, Li J, Hu W, Zhang S, Yuan L, Gao F. Lower body negative pressure protects brain perfusion in aviation gravitational stress induced by push-pull manoeuvre. J Physiol 2020; 598:3173-3186. [PMID: 32415785 DOI: 10.1113/jp279876] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 05/12/2020] [Indexed: 01/12/2023] Open
Abstract
KEY POINTS Rapid alterations of gravitational stress during high-performance aircraft push-pull manoeuvres induce dramatic shifts in volume and pressure within the circulation system, which may result in loss of consciousness due to the rapid and significant reduction in cerebral perfusion. There are still no specific and effective countermeasures so far. We found that lower body negative pressure (LBNP), applied prior to and during -Gz and released at the subsequent transition to +Gz, could effectively counteract gravitational haemodynamic stress induced by a simulated push-pull manoeuvre and improve cerebral diastolic perfusion in human subjects. We developed a LBNP strategy that effectively protects cerebral perfusion at rapid -Gz to +Gz transitions via improving cerebral blood flow and blood pressure during push-pull manoeuvres and highlight the importance of the timing of the intervention. Our findings provide a systemic link of integrated responses between the peripheral and cerebral haemodynamic changes during push-pull manoeuvres. ABSTRACT The acute negative (-Gz) to positive (+Gz) gravity stress during high-performance aircraft push-pull manoeuvres dramatically reduces transient cerebral perfusion, which may lead to loss of vision or even consciousness. The aim of this study was to explore a specific and effective counteractive strategy. Twenty-three healthy young male volunteers (age 21 ± 1 year) were subjected to tilting-simulated push-pull manoeuvres. Lower body negative pressure (LBNP) of -40 mmHg was applied prior to and during -Gz stress (-0.50 or -0.87 Gz) and released at the subsequent transition to +1.00 Gz stress. Beat-to-beat cerebral and systemic haemodynamics were continuously recorded during the simulated push-pull manoeuvre in LBNP bouts and corresponding control bouts. During the rapid gravitational transition from -Gz to +Gz, the mean cerebral blood flow velocity decreased significantly in control bouts, while it increased in LBNP bouts (control vs. LBNP bouts, -6.6 ± 4.6 vs. 5.1 ± 6.8 cm s-1 for -0.50 Gz, and -7.4 ± 4.8 vs. 3.4 ± 4.6 cm s-1 for -0.87 Gz, P < 0.01), which was attributed mainly to the elevation of diastolic flow. The LBNP bouts showed much smaller reduction of mean arterial blood pressure at the brain level than control bouts (control bouts vs. LBNP bouts, -38 ± 12 vs. -23 ± 10 mmHg for -0.50 to +1.00 Gz, and -62 ± 16 vs. -43 ± 11 mmHg for -0.87 to +1.00 Gz, P < 0.01). LBNP applied at -Gz and released at subsequent +Gz had biphasic counteractive effects against the gravitational responses to the push-pull manoeuvre. These data demonstrate that this LBNP strategy could effectively protect cerebral perfusion with dominant improvement of diastolic flow during push-pull manoeuvres.
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Affiliation(s)
- Changyang Xing
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, 710032, China.,Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, 710038, China
| | - Xinpei Wang
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Yuan Gao
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Jiaxin Zhang
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Yunnan Liu
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, 710038, China
| | - Yitong Guo
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, 710038, China
| | - Chen Wang
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, 710038, China
| | - Yang Feng
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, 710038, China
| | - Yujia Lei
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, 710038, China
| | - Xing Zhang
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Jia Li
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Wendong Hu
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Shu Zhang
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, 710032, China
| | - Lijun Yuan
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi'an, 710038, China
| | - Feng Gao
- School of Aerospace Medicine, Fourth Military Medical University, Xi'an, 710032, China
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van Campen CLMC, Verheugt FWA, Visser FC. Cerebral blood flow changes during tilt table testing in healthy volunteers, as assessed by Doppler imaging of the carotid and vertebral arteries. Clin Neurophysiol Pract 2018; 3:91-95. [PMID: 30215015 PMCID: PMC6133915 DOI: 10.1016/j.cnp.2018.02.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 02/17/2018] [Accepted: 02/20/2018] [Indexed: 01/13/2023] Open
Abstract
Extracranial cerebral artery Doppler imaging show CBF changes during tilt testing. Total CBF during tilt testing decreases 6% in healthy volunteers. Flow decrease of internal carotid and vertebral arteries during tilting is similar.
Objectives Using different techniques, reduction of cerebral blood flow (CBF) during orthostatic stress were demonstrated. One study reported flow reduction of the right internal carotid (ICA) and vertebral (VA) artery during orthostatic stress by Doppler imaging, with different effects on the 2 vessels. Global CBF changes, using this technique, have not been reported. Therefore, flow of the ICA, VA and global CBF were measured during head-up tilt testing. Methods 33 healthy volunteers underwent tilt testing. At three time points (supine, half way and at the end of the test) Doppler imaging of the ICA and VA was performed, as well as PetCO2 measurements. Results Global CBF was significantly reduced by 4.5 ± 2.8% halfway the test and by 6.0 ± 3.4% at the end. All 4 artery flows were significantly reduced during the tilt, without differences between them. Despite small changes in PetCO2 there was a significant relation between de CBF decrease and PetCO2 decrease (p < 0.05). Conclusions Orthostatic stress in HV results in a small but significant reduction of CBF by a homogenous reduction in the four cerebral vessels and is modulated by PetCO2 changes. Significance CBF changes can be measured during tilt testing using Doppler VA and ICA imaging.
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Affiliation(s)
| | - Freek W A Verheugt
- Radboud UMC, Geert Grooteplein Zuid 10, 6525 GA Nijmegen, The Netherlands
| | - Frans C Visser
- Stichting CardioZorg, Planetenweg 5, 2132 HN Hoofddorp, The Netherlands
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Viski S, Orosz M, Czuriga-Kovacs KR, Magyar MT, Csiba L, Olah L. The acute effects of alcohol on cerebral hemodynamic changes induced by the head-up tilt test in healthy subjects. J Neurol Sci 2016; 368:113-20. [PMID: 27538612 DOI: 10.1016/j.jns.2016.06.060] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 06/07/2016] [Accepted: 06/27/2016] [Indexed: 10/21/2022]
Abstract
BACKGROUND Alcohol is a known triggering factor for orthostatic dysfunction, increasing the risk of neurally-mediated syncope. Since orthostatic tolerance may be affected by both systemic and cerebral hemodynamic changes, our aim was to investigate the acute effects of alcohol on cerebral vasoreactivity measured during the head-up tilt (HUT) test in 20 healthy subjects. METHODS Mean arterial blood pressure (mBP), heart rate, and flow parameters in both middle cerebral arteries (MCAs) were continuously recorded in the supine and during a 10-minute HUT positions before and after alcohol intake. RESULTS The HUT test resulted in a more prominent decline of adjusted mBP at the level of MCAs (mBPMCA) and a significantly larger decrease of MCA mean flow velocities (MFVMCA) in the post-alcohol period than before alcohol intake. During the HUT phase, the relative decrease in MFVMCA was significantly smaller than the reduction in mBPMCA before drinking alcohol, while these changes were similar after alcohol ingestion. The cerebrovascular resistance index (CVRi) decreased during the HUT phase in the control period, however, it increased after alcohol intake. CONCLUSION The similar decrease in mBPMCA and MFVMCA during orthostatic stress after alcohol ingestion together with the increased CVRi indicated the impairment of the compensatory vasodilation of cerebral resistance vessels, i.e. impaired cerebral autoregulation. These findings suggest that alcohol may contribute to impaired orthostatic tolerance not only by a hypotensive response but also by the alteration of cerebral blood flow regulation.
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Affiliation(s)
- Sandor Viski
- Department of Neurology, University of Debrecen, Moricz Zs. krt. 22, H-4032 Debrecen, Hungary
| | - Miklos Orosz
- Bethesda Children's Hospital of Reformed Church in Hungary, Bethesda u. 3., H-1146 Budapest, Hungary
| | | | - Maria Tunde Magyar
- Department of Neurology, University of Debrecen, Moricz Zs. krt. 22, H-4032 Debrecen, Hungary
| | - Laszlo Csiba
- Department of Neurology, University of Debrecen, Moricz Zs. krt. 22, H-4032 Debrecen, Hungary
| | - Laszlo Olah
- Department of Neurology, University of Debrecen, Moricz Zs. krt. 22, H-4032 Debrecen, Hungary.
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Marshall-Goebel K, Ambarki K, Eklund A, Malm J, Mulder E, Gerlach D, Bershad E, Rittweger J. Effects of short-term exposure to head-down tilt on cerebral hemodynamics: a prospective evaluation of a spaceflight analog using phase-contrast MRI. J Appl Physiol (1985) 2016; 120:1466-73. [PMID: 27013606 PMCID: PMC4909835 DOI: 10.1152/japplphysiol.00841.2015] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 03/21/2016] [Indexed: 11/22/2022] Open
Abstract
Alterations in cerebral hemodynamics in microgravity are hypothesized to occur during spaceflight and could be linked to the Visual Impairment and Intracranial Pressure syndrome. Head-down tilt (HDT) is frequently used as a ground-based analog to simulate cephalad fluid shifts in microgravity; however, its effects on cerebral hemodynamics have not been well studied with MRI techniques. Here, we evaluate the effects of 1) various HDT angles on cerebral arterial and venous hemodynamics; and 2) exposure to 1% CO2 during an intermediate HDT angle (-12°) as an additional space-related environmental factor. Blood flow, cross-sectional area (CSA), and blood flow velocity were measured with phase-contrast MRI in the internal jugular veins, as well as the vertebral and internal carotid arteries. Nine healthy male subjects were measured at baseline (supine, 0°) and after 4.5 h of HDT at -6°, -12° (with and without 1% CO2), and -18°. We found a decrease in total arterial blood flow from baseline during all angles of HDT. On the venous side, CSA increased with HDT, and outflow decreased during -12° HDT (P = 0.039). Moreover, the addition of 1% CO2 to -12° HDT caused an increase in total arterial blood flow (P = 0.016) and jugular venous outflow (P < 0.001) compared with -12° HDT with ambient atmosphere. Overall, the results indicate decreased cerebral blood flow during HDT, which may have implications for microgravity-induced cerebral hemodynamic changes.
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Affiliation(s)
- Karina Marshall-Goebel
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany; Faculty of Medicine, University of Cologne, Cologne, Germany;
| | - Khalid Ambarki
- Department of Radiation Sciences, Umeå University, Umeå, Sweden
| | - Anders Eklund
- Department of Radiation Sciences, Umeå University, Umeå, Sweden; Centre of Biomedical Engineering and Physics, Umeå University, Umeå, Sweden
| | - Jan Malm
- Department of Pharmacology and Clinical Neuroscience, Umeå University, Umeå, Sweden
| | - Edwin Mulder
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Darius Gerlach
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Eric Bershad
- Department of Neurology, Baylor College of Medicine, Houston, Texas; and
| | - Jörn Rittweger
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany; Department of Pediatric and Adolescent Medicine, University of Cologne, Cologne, Germany
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Ogoh S, Hirasawa A, Raven PB, Rebuffat T, Denise P, Lericollais R, Sugawara J, Normand H. Effect of an acute increase in central blood volume on cerebral hemodynamics. Am J Physiol Regul Integr Comp Physiol 2015; 309:R902-11. [DOI: 10.1152/ajpregu.00137.2015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 08/19/2015] [Indexed: 11/22/2022]
Abstract
Systemic blood distribution is an important factor involved in regulating cerebral blood flow (CBF). However, the effect of an acute change in central blood volume (CBV) on CBF regulation remains unclear. To address our question, we sought to examine the CBF and systemic hemodynamic responses to microgravity during parabolic flight. Twelve healthy subjects were seated upright and exposed to microgravity during parabolic flight. During the brief periods of microgravity, mean arterial pressure was decreased (−26 ± 1%, P < 0.001), despite an increase in cardiac output (+21 ± 6%, P < 0.001). During microgravity, central arterial pulse pressure and estimated carotid sinus pressure increased rapidly. In addition, this increase in central arterial pulse pressure was associated with an arterial baroreflex-mediated decrease in heart rate ( r = −0.888, P < 0.0001) and an increase in total vascular conductance ( r = 0.711, P < 0.001). The middle cerebral artery mean blood velocity (MCA Vmean) remained unchanged throughout parabolic flight ( P = 0.30). During microgravity the contribution of cardiac output to MCA Vmean was gradually reduced ( P < 0.05), and its contribution was negatively correlated with an increase in total vascular conductance ( r = −0.683, P < 0.0001). These findings suggest that the acute loading of the arterial and cardiopulmonary baroreceptors by increases in CBV during microgravity results in acute and marked systemic vasodilation. Furthermore, we conclude that this marked systemic vasodilation decreases the contribution of cardiac output to CBF. These findings suggest that the arterial and cardiopulmonary baroreflex-mediated peripheral vasodilation along with dynamic cerebral autoregulation counteracts a cerebral overperfusion, which otherwise would occur during acute increases in CBV.
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Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | - Ai Hirasawa
- Department of Biomedical Engineering, Toyo University, Kawagoe-Shi, Saitama, Japan
| | - Peter B. Raven
- Department of Integrative Physiology, University of North Texas Health Science Center, Fort Worth, Texas
| | - Thomas Rebuffat
- Physiology Department, Faculty of Medicine, Normandie University, France and Institut National de la Santé et de la Recherche Mèdical, Paris, France; Centre Hospitalier Universitaire, Caen, France; and
| | - Pierre Denise
- Physiology Department, Faculty of Medicine, Normandie University, France and Institut National de la Santé et de la Recherche Mèdical, Paris, France; Centre Hospitalier Universitaire, Caen, France; and
| | - Romain Lericollais
- Physiology Department, Faculty of Medicine, Normandie University, France and Institut National de la Santé et de la Recherche Mèdical, Paris, France; Centre Hospitalier Universitaire, Caen, France; and
| | - Jun Sugawara
- Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan
| | - Hervé Normand
- Physiology Department, Faculty of Medicine, Normandie University, France and Institut National de la Santé et de la Recherche Mèdical, Paris, France; Centre Hospitalier Universitaire, Caen, France; and
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