Cerebral Blood Flow Distribution During Parabolic Flight-induced Microgravity (GraCer)
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|ClinicalTrials.gov Identifier: NCT03986788|
Recruitment Status : Enrolling by invitation
First Posted : June 14, 2019
Last Update Posted : February 25, 2020
When astronauts return from space flight, they manifest a set of symptoms, the most striking of which is orthostatic intolerance, that is, the inability to stay upright. This orthostatic intolerance is related to cardiovascular adaptation and disappears in a few days, but the prospect of long-term space travel makes this maladaptation a major concern of space agencies, at a time when there is serious consideration to make " land "a ship on Mars.
Previous studies suggest that brain vessel adaptation may contribute to spatial post-flight orthostatic intolerance. The question remains controversial because not all studies are consistent. These studies are all based on the measurement of blood flow in a single artery of the brain (the average cerebral, see cerebral circulation diagram) easily accessible with a Doppler ultrasound machine. Our team has good reason to believe that the adaptation of the cerebral vessels is not carried out in the same way in all the arteries of the brain and that in particular the arteries that irrigate the posterior and inferior parts of the brain are a major determinant. from cerebrovascular adaptation to orthostatism and that orthostatic intolerance is more specifically related to a decrease in blood flow in these arteries. On the other hand our team has shown that the external carotid artery plays, under certain conditions, a buffer role of the sudden variations of perfusion pressure of the brain.
During the weightless phase of parabolic flight, part of the blood from the legs and abdomen "rises" to the thorax and this transfer of fluid induces changes in blood pressure and cardiac output that affect the cerebral circulation. From a cardiovascular point of view, it is the same thing for a seated subject to lie down, but the parabolic flight offers the unique possibility of achieving this transfer in a fraction of a second and thus allowing to study the immediate response of the cerebral circulation. .
Investigators goal is therefore to quantify the changes in blood flow in the posterior and anterior territories of the brain (transcranial ultrasound) as well as in the internal carotid and vertebral (Doppler ultrasound) during changes in blood pressure and cardiac output induced by transfers. liquid resources associated with the transition to weightlessness.
The oxidative stress generated by weightlessness has been identified as a determining factor in cerebrovascular deconditioning associated with orthostatic intolerance. In order to quantify the biochemical markers of this stress, a venous sample will be taken before and just after the parabolic flight.
|Condition or disease||Intervention/treatment||Phase|
|Weightlessness Cerebral Blood Flow||Other: Weightlessness||Not Applicable|
|Study Type :||Interventional (Clinical Trial)|
|Estimated Enrollment :||18 participants|
|Intervention Model:||Single Group Assignment|
|Intervention Model Description:||Comparison of cerebral blood flow in 1G, 1.8 G and 0G conditions|
|Masking:||None (Open Label)|
|Primary Purpose:||Basic Science|
|Official Title:||Effet de l'Impesanteur Sur la Distribution du débit Sanguin cérébral.|
|Actual Study Start Date :||October 1, 2018|
|Estimated Primary Completion Date :||September 30, 2021|
|Estimated Study Completion Date :||September 30, 2021|
Weightlessness measurements during flight
Volunteers will be studied during parabolic flight. Cerebral blood flow will be measured in different part of the brain during weightlessness ans compared to 1g and hypergravity measurements.
- Cervical blood flow [ Time Frame: baseline ]
Measurement of the cervical blood flow in external (ECA), internal (ICA) and vertebral arteries (VA).
ICA, VA and ECA blood flow velocities will be measured with a color-coded ultrasound system (Vivid-e; GE Healthcare, Tokyo, Japan) equipped with a 10 MHz linear transducer. ICA blood flow measurements will be performed 1.0-1.5 cm distal to the carotid bifurcation while the subject's chin will be slightly elevated. VA blood flow will be measured between the transverse processes of C3 and the subclavian artery. The systolic and diastolic diameters will be measured in detail, and then the mean diameter (in centimetres) will be calculated in relationship to the blood pressure curve, as follows: mean diameter = (systolic diameter×1/3) +(diastolic diameter × 2/3).
- Transcranial blood flow [ Time Frame: baseline ]Measurement of the transcranial blood flow in anterior (ACA), middle (MCA) and posterior (PCA) cerebral arteries. Blood flow velocities in PCA, MCA and ACA will be measured with an echo-doppler device (Philips CX50, Philips, the Netherlands) using vascular probes adapted to transcranial Doppler. Flows in the different branches of the circle of Willis (ACA-1, MCA-1, PCA-1, ACoA, PCoA) will be used to assess the cerebral hemodynamic indices.
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Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT03986788
|Mérignac, France, 33700|
|Study Director:||Christophe Kassel, Hospital Manager||University Hospital, Caen|