Autonomic cardiovascular changes during and after 14 days of head-down bed rest

Hirayanagi, Kaname; Kamiya, Atsunori; Iwase, Satoshi; Mano, Tadaaki; Sasaki, Tsuyoshi; Oinuma, Miyuki; Yajima, Kazuyoshi

doi:10.1016/j.autneu.2004.01.001

Cited by 15 publications

(8 citation statements)

References 22 publications

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“…This suggests that long-term HDBR results in a reduction in vagal cardiac control and a rise in sympathetic activity. Moreover, in agreement with previous studies showing that the spontaneous baroreflex slope decreased during and/or after HDBR [ 12 , 16 – 18 , 35 ], we observed a gradual reduced BRS slope during HDBR, suggesting that the cardiac baroreflex mechanism is disturbed after a prolonged period of bed rest. In addition, we also found a transient decrease in the number of baroreflex estimates at the beginning of HDBR.…”

Section: Discussionsupporting

confidence: 93%

Orthostatic Intolerance Is Independent of the Degree of Autonomic Cardiovascular Adaptation after 60 Days of Head-Down Bed Rest

Liu

Verheyden

et al. 2015

BioMed Research International

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Spaceflight and head-down bed rest (HDBR) can induce the orthostatic intolerance (OI); the mechanisms remain to be clarified. The aim of this study was to determine whether or not OI after HDBR relates to the degree of autonomic cardiovascular adaptation. Fourteen volunteers were enrolled for 60 days of HDBR. A head-up tilt test (HUTT) was performed before and after HDBR. Our data revealed that, in all nonfainters, there was a progressive increase in heart rate over the course of HDBR, which remained higher until 12 days of recovery. The mean arterial pressure gradually increased until day 56 of HDBR and returned to baseline after 12 days of recovery. Respiratory sinus arrhythmia and baroreflex sensitivity decreased during HDBR and remained suppressed until 12 days of recovery. Low-frequency power of systolic arterial pressure increased during HDBR and remained elevated during recovery. Three subjects fainted during the HUTT after HDBR, in which systemic vascular resistance did not increase and remained lower until syncope. None of the circulatory patterns significantly differed between the fainters and the nonfainters at any time point. In conclusion, our data indicate that the impaired orthostatic tolerance after HDBR could not be distinguished by estimation of normal hemodynamic and/or neurocardiac data.

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Section: Discussionsupporting

confidence: 93%

Orthostatic Intolerance Is Independent of the Degree of Autonomic Cardiovascular Adaptation after 60 Days of Head-Down Bed Rest

Liu

Verheyden

et al. 2015

BioMed Research International

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“…In line with previous reports (Pannier et al 1991; Hirayanagi et al 2004), 24 h of bed rest had minimal impact on heart rate variability in baseline conditions. In contrast, the diuretic treatment reduced both RMSSD and HF indicators of HRV, providing time‐domain and spectrally based evidence of reduced heart rate variability.…”

Section: Discussionsupporting

confidence: 92%

Altered cortical activation patterns associated with baroreflex unloading following 24 h of physical deconditioning

Shoemaker

Usselman²,

Rothwell³

et al. 2012

Experimental Physiology

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Cardiovascular arousal is associated with patterned cortical activity changes. Head-down-tilt bed rest (HDBR) dimishes the baroreflex-mediated cardiac control. The present study tested the hypothesis that HDBR deconditioning would modify the forebrain organization for heart rate (HR) control during baroreflex unloading. Heart rate variability (HRV), blood pressure and plasma hormones were analysed at rest, whereas HR and cortical autonomic activation patterns (functional magnetic resonance imaging) were measured during graded and randomly assigned lower body negative pressure treatments (LBNP, −15 and −35 mmHg) both before (Pre) and after (Post) a 24 h HDBR protocol (study 1; n = 8). An additional group was tested before and following diuretic-induced hypovolaemia (study 2; n = 9; spironolactone, 100 mg day −−1 for 3 days) that mimicked the plasma volume lost during HDBR (−15% in both studies; P < 0.05). Head-down bed rest with hypovolaemia did not affect baseline HR, mean arterial pressure, HRV or plasma catecholamines. Head-down bed rest augmented the LBNP-induced HR response (P < 0.05), and this was associated with bed-rest-induced development of the following changes: (i) enhanced activation within the genual anterior cingulate cortex and the right anterior insular cortex; and (ii) deactivation patterns within the subgenual regions of the anterior cingulate cortex. Diuretic treatment (without HDBR) did not affect baseline HR and mean arterial pressure, but did reduce resting HRV and elevated circulating noradrenaline and plasma renin activity (P < 0.05). The greater HR response to LBNP following diuretic (P < 0.05) was associated with diminished activation of the right anterior insula. Our findings indicate that 24 h of HDBR minimized the impact of diuretic treatment on baseline autonomic and cardiovascular variables. The findings also indicate that despite the similar augmentation of HR responses to LBNP and despite similar pre-intervention cortical activation patterns, HDBR and diuretic treatment produced different effects on the cortical responses, with HDBR affecting anterior cingulate cortex and right insula regions, whereas diuretic treatment affected primarily the right insula alone, but in a direction that was opposite to HDBR. The data indicate that physical deconditioning can induce rapid functional changes within the cortical circuitry associated with baroreflex unloading, changes that are distinct from diuretic-induced hypovolaemia. The results suggest that physical activity patterns exert a rapid and notable impact on the cortical circuitry associated with cardiovascular control.

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“…Johansen et al (16) studied PV during HDBR and showed that there was a 6% reduction by day 2 alone. The present overall reduction of 15% on day 5 is larger than that observed by Stenger et al (25) on day 21 and by Johansen et al (16) on day 42 (both Ϫ10%) but lower than that observed by Hirayanagi et al (12) after 3 days of HDBR (Ϫ19%). Furthermore, the present PV reduction is lower than that observed in six astronauts during their first day in flight [Ϫ17%, Alfrey et al (1)].…”

Section: Discussioncontrasting

confidence: 74%

“…In contrast to PV, there were no HDBR-induced changes in RBCV and Hb tot , and as a result there was a hemoconcentration as reflected by increases of Hb and Hct. This is likely to reflect a faster downregulation of PV than of RBC volume, since more prolonged exposures to HDBR or actual microgravity [Zwart et al 2009 (30) and Alfrey et al (1)] do not display the relatively large increase of Hct observed in the present study and in other studies reporting data from the first 2 to 5 days of HDBR (12,16).…”

Section: Discussioncontrasting

confidence: 49%

Effects of an artificial gravity countermeasure on orthostatic tolerance, blood volumes and aerobic power after short-term bed rest (BR-AG1)

Linnarsson

Hughson

Fraser

et al. 2015

Journal of Applied Physiology

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Exposure to artificial gravity (AG) in a short-arm centrifuge has potential benefits for maintaining human performance during long-term space missions. Eleven subjects were investigated during three campaigns of 5 days head-down bed rest: 1) bed rest without countermeasures (control), 2) bed rest and 30 min of AG (AG1) daily, and 3) bed rest and six periods of 5 min AG (AG2) daily. During centrifugation, the supine subjects were exposed to AG in the head-to-feet direction with 1 G at the center of mass. Subjects participated in the three campaigns in random order. The cardiovascular effects of bed rest and countermeasures were determined from changes in tolerance to a head-up tilt test with superimposed lower body negative pressure (HUT), from changes in plasma volume (PV) and from changes in maximum aerobic power (V̇o2 peak) during upright work on a cycle ergometer. Complete data sets were obtained in eight subjects. After bed rest, HUT tolerance times were 36, 64, and 78% of pre-bed rest baseline during control, AG1 and AG2, respectively, with a significant difference between AG2 and control. PV and V̇o2 peak decreased to 85 and 95% of pre-bed rest baseline, respectively, with no differences between the treatments. It was concluded that the AG2 countermeasure should be further investigated during future long-term bed rest studies, especially as it was better tolerated than AG1. The superior effect of AG2 on orthostatic tolerance could not be related to concomitant changes in PV or aerobic power.

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Autonomic cardiovascular changes during and after 14 days of head-down bed rest

Cited by 15 publications

References 22 publications

Orthostatic Intolerance Is Independent of the Degree of Autonomic Cardiovascular Adaptation after 60 Days of Head-Down Bed Rest

Orthostatic Intolerance Is Independent of the Degree of Autonomic Cardiovascular Adaptation after 60 Days of Head-Down Bed Rest

Altered cortical activation patterns associated with baroreflex unloading following 24 h of physical deconditioning

Effects of an artificial gravity countermeasure on orthostatic tolerance, blood volumes and aerobic power after short-term bed rest (BR-AG1)

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