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Effects of prolonged head-down bed rest on sympathetic baroreflex control and orthostatic tolerance

Barbic, F. and Heusser, K. and Shiffer, D. and Minonzio, M. and Cairo, B. and Tank, J. and Jordan, J. and Diedrich, A. and Porta, A. and Robertson, D. and Furlan, R. (2018) Effects of prolonged head-down bed rest on sympathetic baroreflex control and orthostatic tolerance. 10th ESGCO 2018 - Biological Oscillations and Health, 17.-19. September 2018, Wien, Österreich. (Unpublished)

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Official URL: http://esgco2018.com/program/

Abstract

Orthostatic intolerance has been described after prolonged bed confinement in several clinical settings. This may impact patients’ quality of life and increase risk of falls. Standing is associated with unloading of baroreceptor activity controlling heart rate (HR) and sympathetic vasomotor discharge assessed by muscle sympathetic nerve activity (MSNA). In the present study we evaluated the changes in baroreceptor response and in orthostatic tolerance induced by controlled long lasting bed rest in healthy volunteers. As part of the European Space Agency Medium-term Bed Rest protocol, eight volunteers (33 ±1yrs) were studied before and after 21-days of -6º head down bed rest (HDBR). Subjects underwent ECG, beat-by-beat blood pressure, respiratory activity and MSNA recordings during 15-minutes of 80 head-up tilt (HUT) followed by a 3-minute –10mmHg stepwise increase of lower body negative pressure, up to pre-syncope. The α index obtained in the low frequency band (0.1 Hz) by cross-spectrum analysis of RR and systolic arterial pressure (SAP) variability quantified the cardiac baroreflex sensitivity. The percentage of MSNA burst occurrence for different diastolic pressure values (grouped in bins of 1 mmHg) was assessed. The slope of the regression line between MSNA Bursts % and diastolic pressure was assumed to represent the gain of sympathetic baroreflex control (sBRS). the subjects orthostatic tolerance was decreased after HDBR(12±0.6min) compared to baseline (21±0.6min). In the supine position HR, SAP and α index were unchanged before and after HDBR. During HUT, HR and SAP were unmodified, α index was lower after (3.4±0.7) compared to before HDBR (6.4±1.0). While supine, sBRS was lower after (-2.9±1.5 %mmHg) compared to before HDBR (-6.0±1.1 %/mmHg). Similarly, during HUT sBRS was lower after HDBR (-2.2±0.6 %/mmHg) compared to before (-4.4±0.4%mmHg). These data suggest that prolonged bed confinement decreased the overall baroreceptor sensitivity.These alterations may be involved in the reduction of orthostatic tolerance.

Item URL in elib:https://elib.dlr.de/126095/
Document Type:Conference or Workshop Item (Other)
Title:Effects of prolonged head-down bed rest on sympathetic baroreflex control and orthostatic tolerance
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Barbic, F.Department of Internal Medicine, Humanitas Clinical and Research Center, Rozzano (MI), Humanitas University, Rozzano, ItalyUNSPECIFIED
Heusser, K.Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany.UNSPECIFIED
Shiffer, D.Department of Internal Medicine, Humanitas Clinical and Research Center, Rozzano (MI), Humanitas University, Rozzano, ItalyUNSPECIFIED
Minonzio, M.Department of Internal Medicine, Humanitas Clinical and Research Center, Rozzano (MI), Humanitas University, Rozzano, ItalyUNSPECIFIED
Cairo, B.Department of Biomedical Sciences for Health, University of Milan, ItalyUNSPECIFIED
Tank, J.Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany.UNSPECIFIED
Jordan, J.Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany.UNSPECIFIED
Diedrich, A.Division of Clinical Pharmacology, Department of Medicine, Autonomic Dysfunction Service, Vanderbilt University, Nashville, TNUNSPECIFIED
Porta, A.Department of Biomedical Sciences for Health, University of Milan, Italy;Department of Cardiothoracic, Vascular Anesthesia and Intensive Care, IRCCS Policlinico di San Donato, San Donato Milanese, ItalyUNSPECIFIED
Robertson, D.Division of Clinical Pharmacology, Vanderbilt University,UNSPECIFIED
Furlan, R.Department of Internal Medicine, Humanitas Clinical and Research Center, Rozzano (MI), Humanitas University, Rozzano, ItalyUNSPECIFIED
Date:2018
Refereed publication:No
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Unpublished
Keywords:head-down bed rest; sympathetic baroreflex control; orthostatic tolerance
Event Title:10th ESGCO 2018 - Biological Oscillations and Health
Event Location:Wien, Österreich
Event Type:international Conference
Event Dates:17.-19. September 2018
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 > Cardiovascular Medicine in Aerospace
Deposited By: Schrage, Larissa
Deposited On:24 Jan 2019 10:46
Last Modified:31 Jul 2019 20:24

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