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<p>Ground-based models of microgravity, head-down bed rest (HDBR) and dry immersion (DI), may differ in their effects on cardiovascular control, but this has not been directly tested yet during similarly long exposure. This study aimed at comparison of head-up tilt (HUT) induced changes in cardiac baroreflex functioning during 3-week long HDBR and DI. HUT test (60°) was performed in two groups of healthy young men before and then on 7th, 14th and 19th days of HDBR or DI. Fifteen-min recordings of systolic arterial pressure (SAP) and RR-interval (RRI) were used to calculate their spectral powers, cardiac baroreflex sensitivity (cBRS, α index) and phase synchronization index (PSI) in low frequency (LF) band (0.05–0.13 Hz). In supine position, both HDBR and DI did not change LF<sub>SAP</sub> and LF<sub>PSI</sub>, while similarly decreased LF<sub>RRI</sub> and cBRS. The decrease in stroke volume was larger during DI. Both models potentiated the rise in LF<sub>SAP</sub>&#xa0;during HUT. However, the reductions in LF<sub>RRI</sub> and cBRS during HUT were substantially more pronounced in DI compared to HDBR (starting from day 14 DI almost completely suppressed LF<sub>RRI</sub> and cBRS during HUT). LF<sub>PSI</sub> was increased by HUT before exposure to simulated microgravity and during HDBR, but DI abolished this response. Thus,&#xa0;cBRS is more affected in DI compared to HDBR, probably because of higher central hypovolemia and/or arterial wall stiffening. Diverse effects of HDBR on cBRS and PSI indicate that the amplitude and phase relationships of LF SAP and RRI waves characterize different aspects of cardiac baroreflex control.</p>

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Three-week dry immersion results in a more severe impairment of cardiac baroreflex than head-down bed rest of the same duration

  • 期刊论文

  • 发表日期：

    2025年10月29日

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  • Anatoly S. Borovik,
  • Roman Yu. Zhedyaev,
  • Elena S. Tomilovskaya,
  • Alexey V. Shpakov,
  • Oleg I. Orlov,
  • Olga L. Vinogradova,
  • Olga S. Tarasova

摘要

Ground-based models of microgravity, head-down bed rest (HDBR) and dry immersion (DI), may differ in their effects on cardiovascular control, but this has not been directly tested yet during similarly long exposure. This study aimed at comparison of head-up tilt (HUT) induced changes in cardiac baroreflex functioning during 3-week long HDBR and DI. HUT test (60°) was performed in two groups of healthy young men before and then on 7th, 14th and 19th days of HDBR or DI. Fifteen-min recordings of systolic arterial pressure (SAP) and RR-interval (RRI) were used to calculate their spectral powers, cardiac baroreflex sensitivity (cBRS, α index) and phase synchronization index (PSI) in low frequency (LF) band (0.05–0.13 Hz). In supine position, both HDBR and DI did not change LFSAP and LFPSI, while similarly decreased LFRRI and cBRS. The decrease in stroke volume was larger during DI. Both models potentiated the rise in LFSAP during HUT. However, the reductions in LFRRI and cBRS during HUT were substantially more pronounced in DI compared to HDBR (starting from day 14 DI almost completely suppressed LFRRI and cBRS during HUT). LFPSI was increased by HUT before exposure to simulated microgravity and during HDBR, but DI abolished this response. Thus, cBRS is more affected in DI compared to HDBR, probably because of higher central hypovolemia and/or arterial wall stiffening. Diverse effects of HDBR on cBRS and PSI indicate that the amplitude and phase relationships of LF SAP and RRI waves characterize different aspects of cardiac baroreflex control.