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HUMAN SPACEFLIGHT COUNTERMEASURES: CEREBRAL HEMODYNAMICS DURING SHORT-ARM HUMAN CENTRIFUGATION AND THE ROLE OF PERIPHERAL FLUID SHIFTS AND JUGULAR VENOUS CONGESTION

Laing, Charles (2017) HUMAN SPACEFLIGHT COUNTERMEASURES: CEREBRAL HEMODYNAMICS DURING SHORT-ARM HUMAN CENTRIFUGATION AND THE ROLE OF PERIPHERAL FLUID SHIFTS AND JUGULAR VENOUS CONGESTION. Dissertation, King's College London.

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Abstract

Spaceflight induces physiological deconditioning, despite extensive exercise countermeasures. Furthermore, post-flight orthostatic intolerance (OI) and visual impairment and intracranial pressure (VIIP) syndrome; possibly related to venous congestion (VC) suggest more holistic countermeasures, such as artificial gravity (AG) short-arm human centrifugation (SAHC) are warranted. SAHC may reduce OI and VIIP incidence through headward fluid shift/pressure reversal; and thus beneficial effects on cerebral hemodynamics. Therefore, this thesis examined how peripheral fluid shifts, induced by various orthostatic challenges, affect central, peripheral, and cerebral hemodynamics, including indices of VC, in healthy participants. Study one induced 5 min bilateral lower-limb venous cuff occlusion (VCO) up to 120mmHg in nine participants. VCO produced significant increments in leg volume (41-158mL;p<0.05); however, HR and cerebral tissue oxygenation (cTSI) were unchanged, suggesting an inadequate orthostatic challenge. Study two involved twenty participants experiencing 10 min SAHC to 2.4+Gz footlevel with increased g-gradients; specifically, moving rotational axis Position (RAP), independent of g-level, towards the body. Increasing SAHC g-gradients reduced the HR response and increased g-tolerance (χ2(1, n=20)=8.57;p=0.003), similar to decreasing g-level. Heart-level-RAP did not improve cTSI as hypothesised, possibly due to VC. Thus, study three used 5 min head-down tilt (HDT) to -24° and -40mmHg lower body negative pressure (LBNP) on sixteen participants to evaluate VC during headward fluid shifts HDT induced significant VC below -12° p<0.05), abolished with -40mmHg LBNP (107±11 vs. 1±5mm2;p<0.05), and increased cerebral blood flow when LBNP-peripheral and HDT-headward fluid shifts balanced (-0.71±0.56 vs. 4.12±1.36cm.s-1;p=0.013). This thesis suggests that VCO is a poor model of ravitational fluid shifting but large g-gradient SAHC, via heart-level-RAP, is effective; and crucially, more tolerable at higher g-levels. VC may play an important role in crogravity fluid shift related OI and VIIP, which -6° bed rest studies fail to induce. Thus, AG with optimal RAP and VC amelioration, may be a tolerable and effective spaceflight countermeasure.

Item URL in elib:https://elib.dlr.de/128906/
Document Type:Thesis (Dissertation)
Title:HUMAN SPACEFLIGHT COUNTERMEASURES: CEREBRAL HEMODYNAMICS DURING SHORT-ARM HUMAN CENTRIFUGATION AND THE ROLE OF PERIPHERAL FLUID SHIFTS AND JUGULAR VENOUS CONGESTION
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Laing, CharlesKing’s College LondonUNSPECIFIED
Date:2017
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Number of Pages:272
Status:Published
Keywords:countermeasure; centrifugation; fluid shift; cerebral hemodynamics;
Institution:King's College London
Department:Centre of Human & Aerospace Physiological Sciences (CHAPS)
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Research under Space Conditions
DLR - Research area:Raumfahrt
DLR - Program:R FR - Forschung unter Weltraumbedingungen
DLR - Research theme (Project):R - Vorhaben Systemphysiologie
Location: Köln-Porz
Institutes and Institutions:Institute of Aerospace Medicine > Muscle and Bone Metabolism
Deposited By: Becker, Christine
Deposited On:05 Sep 2019 15:06
Last Modified:05 Sep 2019 15:06

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