Differences between left and right ventricular cardiac output during (simulated) hyper- to micro-gravity transitions
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1
German Sport University Cologne, Institute of Physiology and Anatomy, Germany
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2
Center for Space Medicine and Extreme Environments, Institute of Physiology, Germany
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3
Deutsches Zentrum für Luft- und Raumfahrt, Helmholtz-Gemeinschaft Deutscher Forschungszentren (HZ), Germany
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4
Abteilung für Kardiologie, Kölner Herzzentrum, Universitätsklinikum Köln, Germany
Purpose: Alterations in gravity or body position impact direction and magnitude of hydrostatic pressure gradients acting inside the human body. Thus, pulmonary and systemic circulation are influenced which may lead to temporary asymmetries between left (Q’LV) and right ventricular cardiac output (Q’RV).
Methodology: Eight healthy male subjects (32 ± 3 yr, 182 ± 7 cm, 82 ± 6 kg) were tested during parabolic flight (PF) and also in an analog experiment in a long arm human centrifuge (laHC) and on a tilt seat (TS). Exposure to posGz in laHC and tilting angles on TS were chronologically matched to the PF protocol with amplitudes ranging from 1.2 posGz to 2.1 posGz and -6° to 90° respectively. During the (simulated) μ-G phases subjects performed one of four maneuvers in randomized order: inactivity, intermittent exerted exhalation (IEE), muscle contraction (MC) or intermittent exerted exhalation and muscle contraction combined (IEE-MC). Q’LV was measured beat-to-beat using a finger cuff and applying the Modelflow® algorithm. Pulmonary oxygen uptake was recorded breath-by-breath which allowed Q’RV calculation via the Fick principle assuming a temporary constant arteriovenous oxygen concentration difference.
Results: The mean accumulated differences in Q’RV and Q’LV (ΣΔQ’RV-LV) during the initial 22 s of μ-G phase for all subjects represent the blood volume shift between systemic and pulmonary circulation. For the inactivity maneuver, ΣΔQ’RV-LV increases up to 0.42 L during PF and up to 1.45 L on TS. MC amplifies ΣΔQ’RV-LV with 0.64 L during PF and 1.72 L on TS. Whereas IEE switches the blood volume shift in opposite direction with ΣΔQ’RV-LV of -0.93 L during PF and -0.42 L on TS. IEE-MC shows almost equivalent effects like IEE. The consequences for ΣΔQ’RV-LV in laHC condition are negligible.
Conclusions: Reduction in gravity during PF as well as tilting the gravity angle from caudal to cranial direction on TS raises ΣΔQ’RV-LV. This is due to increased venous return to the right ventricle resulting in asymmetrical filling pressure compared to the left ventricle. Hence, a pooling of blood volume in pulmonary vessels can be assumed. MC enhances this effect inducing an even pronounced ΣΔQ’RV-LV. Contrary observations have been made regarding the IEE and IEE-MC maneuver. Intrathoracic pressure overcomes above mentioned effects and forces blood out of the pulmonary circulation into the left ventricle and reduces venous return. These responses should be considered in hemodynamic experiments comprising variations in gravity or body position.
Acknowledgements
This research was supported by funding of the German Aerospace Center (DLR e.V.; FKZ: 50WB1426)
Keywords:
hyper-gravity,
micro-gravity,
parabolic flight,
tilt table,
Human centrifuge,
blood volume shift,
Pulmonary Circulation,
Systemic circulation,
Cardiac Output,
Hydrostatic Pressure,
Venous return,
Filling pressure,
Hemodynamics,
Blood pooling
Conference:
39th ISGP Meeting & ESA Life Sciences Meeting, Noordwijk, Netherlands, 18 Jun - 22 Jun, 2018.
Presentation Type:
Extended abstract
Topic:
Cardiovascular, Fluid Shift and Respiration
Citation:
Thieschäfer
L,
Koschate
J,
Drescher
U,
Werner
A,
Dumitrescu
D and
Hoffmann
U
(2019). Differences between left and right ventricular cardiac output during (simulated) hyper- to micro-gravity transitions.
Front. Physiol.
Conference Abstract:
39th ISGP Meeting & ESA Life Sciences Meeting.
doi: 10.3389/conf.fphys.2018.26.00041
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Received:
02 Dec 2018;
Published Online:
16 Jan 2019.
*
Correspondence:
Mr. Lutz Thieschäfer, German Sport University Cologne, Institute of Physiology and Anatomy, Cologne, North Rhine-Westphalia, 50933, Germany, lutz.thieschaefer@uni-oldenburg.de