Cardiovascular Adaptations to Long-Duration Head-Down Bed Rest

Platts, Steven H.; Martin, David S.; Stenger, Michael B.; Perez, Sondra A.; Ribeiro, L. Christine; Summers, Richard L.; Meck, Janice V.

doi:10.3357/asem.br03.2009

Cited by 77 publications

(72 citation statements)

References 28 publications

(43 reference statements)

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“…However, it has been shown that merely supplanting the loss of plasma volume does not counteract orthostatic tolerance. Thus, plasma volume is not a direct indicator of orthostatic intolerance, though it might serve as a triggering mechanism for further dysfunction (Platts et al 2009). Plasma volume seems to be maintained with an exercising countermeasure; AG alone was not effective at counteracting its loss.…”

Section: Cardiovascular Resultsmentioning

confidence: 99%

A critical benefit analysis of artificial gravity as a microgravity countermeasure

2010

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Human physiological systems, especially the cardiovascular and musculo-skeletal systems, are well-known to decondition during spaceflight. Several countermeasures that are in use today have been rigorously developed over the decades to combat this deconditioning. However, these countermeasures are system specific and have proven to be only partially effective. Artificial gravity has been persistently discussed as a countermeasure that potentially has salutary effects on all physiological systems, though few ground-based studies have been performed in comparison to other countermeasures. The current analysis attempts to elucidate the effectiveness of artificial gravity by directly comparing results of previously published and unpublished deconditioning studies with those of more traditional, ground-based countermeasures (i.e. resistive exercise, aerobic exercise, lower body negative pressure, or some variation of these). Animal studies were also evaluated to supplement the knowledge base and to fill gaps in the human countermeasure literature. Designs of published studies, such as study duration, deconditioning paradigm, subject selection criteria, measurements taken, etc., were confounding variables; however, studies that had some measure of consistency between these variables were compared, although notable differences were cited in the analysis and discussion. Results indicate that for prolonged spaceflight an artificial gravity-based countermeasure may provide benefits equivalent to traditional countermeasures for the cardiovascular system. Too few comparable, human studies have been performed to draw any conclusions for the musculoskeletal system, although animal studies show some positive results. Gaps in the current knowledge of artificial gravity are identified and guidance for future deconditioning studies is offered. Based on the results of this study, a comprehensive artificial gravity protocol is proposed and future research topics using this countermeasure are

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Section: Cardiovascular Resultsmentioning

confidence: 99%

A critical benefit analysis of artificial gravity as a microgravity countermeasure

2010

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“…Acute alterations in NO effects on blood vessels have been noted under conditions that simulate spaceflight in animals (31,36,41,44) and humans (5,7,30,34,35). These results suggest that alterations in hemodynamic responses with exposure to real or simulated microgravity may be due to changes in NO-mediated mechanisms.…”

mentioning

confidence: 87%

“…blood pressure; cerebral blood flow; Doppler ultrasound; nitroglycerin; hemodynamics; head-down bed rest; Women's International Simulation for Space Exploration-2005 Study THE VASODILATORY ACTIONS of nitric oxide (NO) work in conjunction with sympathetic vasoconstrictor activity and other vasoactive hormones in the regulation of blood pressure and blood flow (13,24). Acute alterations in NO effects on blood vessels have been noted under conditions that simulate spaceflight in animals (31, 36, 41, 44) and humans (5,7,30,34,35). These results suggest that alterations in hemodynamic responses with exposure to real or simulated microgravity may be due to changes in NO-mediated mechanisms.…”

mentioning

confidence: 99%

WISE 2005: responses of women to sublingual nitroglycerin before and after 56 days of 6° head-down bed rest

Zuj

Edgell

Shoemaker

et al. 2012

Journal of Applied Physiology

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2012.-This study tested the hypothesis that cardiovascular effects of sublingual nitroglycerin (NG) would be exaggerated after 56 days of 6°head-down bed rest (HDBR) in women, and that an aerobic and resistive exercise countermeasure (EX, n ϭ 8) would reduce the effect compared with HDBR without exercise (CON, n ϭ 7). Middle cerebral artery maximal blood flow velocity (CBFV), cardiac stroke volume (SV), and superficial femoral artery blood flow (Doppler ultrasound) were recorded at baseline rest and for 5 min following 0.3 mg sublingual NG. Post-HDBR, NG caused greater increases in heart rate (HR) in CON compared with EX (ϩ24.9 Ϯ 7.7 and ϩ18.8 Ϯ 6.6 beats/min, respectively, P Ͻ 0.0001). The increase in HR combined with reductions in SV to maintain cardiac output. Systolic, mean, and pulse pressures were reduced 5-10 mmHg by NG, but total peripheral resistance was only slightly reduced at 3 min after NG. Reductions in CBFV of Ϫ12.5 Ϯ 3.8 cm/s were seen after NG, but a reduction in the Doppler resistance index suggested dilation of the middle cerebral artery with no differences after HDBR. The femoral artery dilated with NG and blood flow was reduced ϳ50% with the appearance of large negative waves suggesting a marked increase in downstream resistance, but there were no effects of HDBR. In general, responses of women to NG were not altered by HDBR; the greater increase in HR in CON but not EX was probably a consequence of cardiovascular deconditioning. These results contrast with the hypothesis and a previous investigation of men after HDBR by revealing no change in cardiovascular responses to exogenous nitric oxide. blood pressure; cerebral blood flow; Doppler ultrasound; nitroglycerin; hemodynamics; head-down bed rest; Women's International Simulation for Space Exploration-2005 Study THE VASODILATORY ACTIONS of nitric oxide (NO) work in conjunction with sympathetic vasoconstrictor activity and other vasoactive hormones in the regulation of blood pressure and blood flow (13,24). Acute alterations in NO effects on blood vessels have been noted under conditions that simulate spaceflight in animals (31, 36, 41, 44) and humans (5,7,30,34,35). These results suggest that alterations in hemodynamic responses with exposure to real or simulated microgravity may be due to changes in NO-mediated mechanisms.Animal models of simulated microgravity have shown elevated nitric oxide synthase (NOS) activity increasing NO production that could dilate peripheral vessels and reduce vascular responsiveness to norepinephrine (36,41). In contrast, cerebral arteries of hindlimb-suspended rats show reduced endothelial NOS (eNOS) protein (44) and reduced middle cerebral artery endothelium-dependent dilation (31). These results from animal studies point toward potential regional differences in hemodynamic responses to NO after simulated microgravity, a topic that has not been studied in humans.Focusing on isolated regions, studies involving humans suggest changes in the NO system after simulated microgravity. Expression of NOS isoforms in ...

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“…The Spearman rank correlation was used to assess the association between physiologic data (fluid balance, plasma volume, blood volume, and cortisol levels provided by other investigators 5,6 ) and MR imaging measures. No significant correlation was found (Table 1).…”

Section: Physiologic Datamentioning

confidence: 99%

Structural Brain Changes following Long-Term 6° Head-Down Tilt Bed Rest as an Analog for Spaceflight

Roberts

Zhu

Tabesh³

et al. 2015

AJNR Am J Neuroradiol

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Cardiovascular Adaptations to Long-Duration Head-Down Bed Rest

Abstract: Our data suggest that bed rest altered cardiovascular structure and function in a pattern similar to short-duration spaceflight. Additionally, the vascular alterations were primarily seen in the lower body, while vessels of the upper body were unaffected.

Cited by 77 publications

References 28 publications

A critical benefit analysis of artificial gravity as a microgravity countermeasure

A critical benefit analysis of artificial gravity as a microgravity countermeasure

WISE 2005: responses of women to sublingual nitroglycerin before and after 56 days of 6° head-down bed rest

Structural Brain Changes following Long-Term 6° Head-Down Tilt Bed Rest as an Analog for Spaceflight

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