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Autonomic cardiac control following 30 days strict head down tilt bedrest

Möstl, S. and Hönemann, J. and Hoffmann, F. and Diedrich, A. and Heusser, K. and Jordan, J. and Tank, J. (2023) Autonomic cardiac control following 30 days strict head down tilt bedrest. 34TH INTERNATIONAL SYMPOSIUM ON THE AUTONOMIC NERVOUS SYSTEM, 2023-11-15 - 2023-11-18, Puerto Rico.

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Background: Autonomic cardiovascular regulation is impaired both after bedrest and after space flight. Impaired autonomic control likely limits cardiovascular adaptation to physiological stresses such as standing. We hypothesized that 6 h daily lower body negative pressure (LBNP) helps maintain heart rate (HR), heart rate variability (HRV) and baroreflex sensitivity (BRS) following strict head-down tilt bedrest, an established terrestrial space-analogue. Methods: We included 23 healthy persons (12 women, 34.5 ± 9 years, 23.9 ± 2.8 kg/m²) in the 30 days SANS_CM strict head down tilt bedrest study. Subjects were randomly assigned to 6 h daily LBNP training with moderate intensity (LBNP, - 25 mmHg) or 6 h daily sitting (seated, positive control). We measured HR and finger blood pressure before bedrest and at the end of bedrest during head-up tilt testing. We assessed HRV in the time and frequency domains, systolic blood pressure variability in the low frequency range (LF-SBP), and baroreflex sensitivity using cross spectral analysis (BRS-LF). We analyzed stationary time series during the last 5 min supine and during minutes 2–6 at 80 degrees head-up tilt. Results: Supine HR increased during bedrest (LBNP group: 67 ± 9 vs. 74 ± 11; seated: 66 ± 10 vs. 71 ± 12 bpm; p \0.001) and the orthostatic HR response was enhanced (HR upright: 90 ± 10 vs. 112 ± 13 bpm; 86 ± 12 vs. 109 ± 13 bpm; p\ 0.0001). HRV in the time domain was reduced after bedrest while supine (rmssd: 37 ± 24 vs. 27 ± 14 ms; 50 ± 44 vs. 30 ± 20 ms; p\ 0.017) and upright (15 ± 5 vs. 8 ± 4 ms and 28 ± 21 vs. 14 ± 10 ms; p \0.001). HRV in the frequency domain (total power, LF- and HF power) tended to decrease while supine and standing but the bedrest effect did not reach significance. Supine and upright LF/HF ratios did not differ after bedrest. The tilt induced increase of LF-SBP tended to be enhanced after bedrest (p = 0.0547). Baroreflex mediated vagal HR control was reduced after bedrest at rest (p = 0.011) and during tilt (p \0.0001). No interactions between groups and conditions were detected. Conclusions: Six hours of daily moderate intensity LBNP training or seating do not completely preserve autonomic cardiovascular autonomic control during 30 days strict head-down tilt bedrest. Additional countermeasures, such as physical exercise, may be required.

Item URL in elib:https://elib.dlr.de/199952/
Document Type:Conference or Workshop Item (Poster)
Title:Autonomic cardiac control following 30 days strict head down tilt bedrest
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Hönemann, J.Klinik für Kardiologie, Angiologie, Pneumologie und Internistische Intensivmedizin, Herzzentrum der Universität zu Köln, KölnUNSPECIFIEDUNSPECIFIED
Hoffmann, F.Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany.;Department of Cardiology, Pneumology, and Angiology, Heart Center of the University of Cologne, GermanyUNSPECIFIEDUNSPECIFIED
Heusser, K.UNSPECIFIEDhttps://orcid.org/0000-0002-2571-5585UNSPECIFIED
Jordan, J.UNSPECIFIEDhttps://orcid.org/0000-0003-4518-0706UNSPECIFIED
Tank, J.UNSPECIFIEDhttps://orcid.org/0000-0002-5672-1187UNSPECIFIED
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Keywords:cardiac control; head down tilt; bedrest; study
Event Location:Puerto Rico
Event Type:international Conference
Event Start Date:15 November 2023
Event End Date:18 November 2023
Organizer:American Autonomic Society
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 - Research under Space Conditions
DLR - Research theme (Project):R - CardioBrain
Location: Köln-Porz
Institutes and Institutions:Institute of Aerospace Medicine
Institute of Aerospace Medicine > Cardiovascular Medicine in Aerospace
Institute of Aerospace Medicine > Leitungsbereich ME
Deposited By: Schrage, Larissa
Deposited On:05 Dec 2023 17:26
Last Modified:24 Apr 2024 21:00

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