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Rabineau J, Issertine M, Hoffmann F, Gerlach D, Caiani EG, Haut B, van de Borne P, Tank J, Migeotte PF. Cardiovascular deconditioning and impact of artificial gravity during 60-day head-down bed rest—Insights from 4D flow cardiac MRI. Front Physiol 2022; 13:944587. [PMID: 36277205 PMCID: PMC9586290 DOI: 10.3389/fphys.2022.944587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 09/13/2022] [Indexed: 12/03/2022] Open
Abstract
Microgravity has deleterious effects on the cardiovascular system. We evaluated some parameters of blood flow and vascular stiffness during 60 days of simulated microgravity in head-down tilt (HDT) bed rest. We also tested the hypothesis that daily exposure to 30 min of artificial gravity (1 g) would mitigate these adaptations. 24 healthy subjects (8 women) were evenly distributed in three groups: continuous artificial gravity, intermittent artificial gravity, or control. 4D flow cardiac MRI was acquired in horizontal position before (−9 days), during (5, 21, and 56 days), and after (+4 days) the HDT period. The false discovery rate was set at 0.05. The results are presented as median (first quartile; third quartile). No group or group × time differences were observed so the groups were combined. At the end of the HDT phase, we reported a decrease in the stroke volume allocated to the lower body (−30% [−35%; −22%]) and the upper body (−20% [−30%; +11%]), but in different proportions, reflected by an increased share of blood flow towards the upper body. The aortic pulse wave velocity increased (+16% [+9%; +25%]), and so did other markers of arterial stiffness (CAVI; CAVI0). In males, the time-averaged wall shear stress decreased (−13% [−17%; −5%]) and the relative residence time increased (+14% [+5%; +21%]), while these changes were not observed among females. Most of these parameters tended to or returned to baseline after 4 days of recovery. The effects of the artificial gravity countermeasure were not visible. We recommend increasing the load factor, the time of exposure, or combining it with physical exercise. The changes in blood flow confirmed the different adaptations occurring in the upper and lower body, with a larger share of blood volume dedicated to the upper body during (simulated) microgravity. The aorta appeared stiffer during the HDT phase, however all the changes remained subclinical and probably the sole consequence of reversible functional changes caused by reduced blood flow. Interestingly, some wall shear stress markers were more stable in females than in males. No permanent cardiovascular adaptations following 60 days of HDT bed rest were observed.
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Affiliation(s)
- Jeremy Rabineau
- LPHYS, Département de Cardiologie, Université Libre de Bruxelles, Brussels, Belgium
- TIPs, École Polytechnique de Bruxelles, Université Libre de Bruxelles, Brussels, Belgium
- *Correspondence: Jeremy Rabineau,
| | - Margot Issertine
- LPHYS, Département de Cardiologie, Université Libre de Bruxelles, Brussels, Belgium
| | - Fabian Hoffmann
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Darius Gerlach
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Enrico G. Caiani
- Electronic, Information and Biomedical Engineering Department, Politecnico di Milano, Milan, Italy
| | - Benoit Haut
- TIPs, École Polytechnique de Bruxelles, Université Libre de Bruxelles, Brussels, Belgium
| | | | - Jens Tank
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
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Hedge ET, Patterson CA, Mastrandrea CJ, Sonjak V, Hajj-Boutros G, Faust A, Morais JA, Hughson RL. Implementation of exercise countermeasures during spaceflight and microgravity analogue studies: Developing countermeasure protocols for bedrest in older adults (BROA). Front Physiol 2022; 13:928313. [PMID: 36017336 PMCID: PMC9395735 DOI: 10.3389/fphys.2022.928313] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 06/27/2022] [Indexed: 12/18/2022] Open
Abstract
Significant progress has been made in the development of countermeasures to attenuate the negative consequences of prolonged exposure to microgravity on astronauts’ bodies. Deconditioning of several organ systems during flight includes losses to cardiorespiratory fitness, muscle mass, bone density and strength. Similar deconditioning also occurs during prolonged bedrest; any protracted time immobile or inactive, especially for unwell older adults (e.g., confined to hospital beds), can lead to similar detrimental health consequences. Due to limitations in physiological research in space, the six-degree head-down tilt bedrest protocol was developed as ground-based analogue to spaceflight. A variety of exercise countermeasures have been tested as interventions to limit detrimental changes and physiological deconditioning of the musculoskeletal and cardiovascular systems. The Canadian Institutes of Health Research and the Canadian Space Agency recently provided funding for research focused on Understanding the Health Impact of Inactivity to study the efficacy of exercise countermeasures in a 14-day randomized clinical trial of six-degree head-down tilt bedrest study in older adults aged 55–65 years old (BROA). Here we will describe the development of a multi-modality countermeasure protocol for the BROA campaign that includes upper- and lower-body resistance exercise and head-down tilt cycle ergometry (high-intensity interval and continuous aerobic exercise training). We provide reasoning for the choice of these modalities following review of the latest available information on exercise as a countermeasure for inactivity and spaceflight-related deconditioning. In summary, this paper sets out to review up-to-date exercise countermeasure research from spaceflight and head-down bedrest studies, whilst providing support for the proposed research countermeasure protocols developed for the bedrest study in older adults.
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Affiliation(s)
- Eric T. Hedge
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON, Canada
- Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | | | | | - Vita Sonjak
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Guy Hajj-Boutros
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Andréa Faust
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - José A. Morais
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
- Division of Geriatric Medicine, McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Richard L. Hughson
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON, Canada
- *Correspondence: Richard L. Hughson,
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3
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Computational modeling of orthostatic intolerance for travel to Mars. NPJ Microgravity 2022; 8:34. [PMID: 35945233 PMCID: PMC9363491 DOI: 10.1038/s41526-022-00219-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 07/15/2022] [Indexed: 11/12/2022] Open
Abstract
Astronauts in a microgravity environment will experience significant changes in their cardiopulmonary system. Up until now, there has always been the reassurance that they have real-time contact with experts on Earth. Mars crew however will have gaps in their communication of 20 min or more. In silico experiments are therefore needed to assess fitness to fly for those on future space flights to Mars. In this study, we present an open-source controlled lumped mathematical model of the cardiopulmonary system that is able simulate the short-term adaptations of key hemodynamic parameters to an active stand test after being exposed to microgravity. The presented model is capable of adequately simulating key cardiovascular hemodynamic changes—over a short time frame—during a stand test after prolonged spaceflight under different gravitational conditions and fluid loading conditions. This model can form the basis for further exploration of the ability of the human cardiovascular system to withstand long-duration space flight and life on Mars.
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Saehle T. Cerebral Hemodynamics During Exposure to Hypergravity (+G z) or Microgravity (0 G). Aerosp Med Hum Perform 2022; 93:581-592. [DOI: 10.3357/amhp.6008.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND: Optimal human performance and health is dependent on steady blood supply to the brain. Hypergravity (+Gz) may impair cerebral blood flow (CBF), and several investigators have also reported that microgravity (0 G) may influence cerebral hemodynamics. This
has led to concerns for safe performance during acceleration maneuvers in aviation or the impact long-duration spaceflights may have on astronaut health.METHODS: A systematic PEO (Population, Exposure, Outcome) search was done in PubMed and Web of Science, addressing studies on
how elevated +Gz forces or absence of such may impact cerebral hemodynamics. All primary research containing anatomical or physiological data on relevant intracranial parameters were included. Quality of the evidence was analyzed using the GRADE tool.RESULTS: The search
revealed 92 eligible articles. It is evident that impaired CBF during +Gz acceleration remains an important challenge in aviation, but there are significant variations in individual tolerance. The reports on cerebral hemodynamics during weightlessness are inconsistent, but published
data indicate that adaptation to sustained microgravity is also characterized by significant variations among individuals.DISCUSSION: Despite a high number of publications, the quality of evidence is limited due to observational study design, too few included subjects, and methodological
challenges. Clinical consequences of high +Gz exposure are well described, but there are significant gaps in knowledge regarding the intracranial pathophysiology and individual hemodynamic tolerance to both hypergravity and microgravity environments.Saehle T. Cerebral
hemodynamics during exposure to hypergravity (+Gz) or microgravity (0 G). Aerosp Med Hum Perform. 2022; 93(7):581–592.
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Abstract
The direct (eg, radiation, microgravity) and indirect (eg, lifestyle perturbations) effects of spaceflight extend across multiple systems resulting in whole-organism cardiovascular deconditioning. For over 50 years, National Aeronautics and Space Administration has continually enhanced a countermeasures program designed to characterize and offset the adverse cardiovascular consequences of spaceflight. In this review, we provide a historical overview of research evaluating the effects of spaceflight on cardiovascular health in astronauts and outline mechanisms underpinning spaceflight-related cardiovascular alterations. We also discuss how spaceflight could be leveraged for aging, industry, and model systems such as human induced pluripotent stem cell-derived cardiomyocytes, organoid, and organ-on-a-chip technologies. Finally, we outline the increasing opportunities for scientists and clinicians to engage in cardiovascular research in space and on Earth.
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Affiliation(s)
- Jessica M Scott
- Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY (J.M.S.).,Weill Cornell Medical College, New York, NY (J.M.S.)
| | | | - Lianne Dolan
- Toronto Rehabilitation Institute, University Health Network, Toronto, ON, Canada (L.D.)
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Diaz-Canestro C, Montero D. Blood volume primarily determines orthostatic tolerance in women. J Intern Med 2022; 291:371-373. [PMID: 34605081 DOI: 10.1111/joim.13397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Candela Diaz-Canestro
- Libin Cardiovascular Institute of Alberta, University of Calgary, Canada, Alberta, Canada
| | - David Montero
- Libin Cardiovascular Institute of Alberta, University of Calgary, Canada, Alberta, Canada.,Department of Cardiac Sciences, Cumming School of Medicine, Calgary, Alberta, Canada.,Faculty of Kinesiology, University of Calgary, Alberta, Canada
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Goldstein DS. Stress and the "extended" autonomic system. Auton Neurosci 2021; 236:102889. [PMID: 34656967 PMCID: PMC10699409 DOI: 10.1016/j.autneu.2021.102889] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2021] [Revised: 09/06/2021] [Accepted: 09/28/2021] [Indexed: 12/22/2022]
Abstract
This review updates three key concepts of autonomic neuroscience-stress, the autonomic nervous system (ANS), and homeostasis. Hans Selye popularized stress as a scientific idea. He defined stress variously as a stereotyped response pattern, a state that evokes this pattern, or a stimulus that evokes the state. According to the "homeostat" theory stress is a condition where a comparator senses a discrepancy between sensed afferent input and a response algorithm, the integrated error signal eliciting specific patterns of altered effector outflows. Scientific advances since Langley's definition of the ANS have incited the proposal here of the "extended autonomic system," or EAS, for three reasons. (1) Several neuroendocrine systems are bound inextricably to Langley's ANS. The first to be described, by Cannon in the early 1900s, involves the hormone adrenaline, the main effector chemical of the sympathetic adrenergic system. Other neuroendocrine systems are the hypothalamic-pituitary-adrenocortical system, the arginine vasopressin system, and the renin-angiotensin-aldosterone system. (2) An evolving body of research links the ANS complexly with inflammatory/immune systems, including vagal anti-inflammatory and catecholamine-related inflammasomal components. (3) A hierarchical network of brain centers (the central autonomic network, CAN) regulates ANS outflows. Embedded within the CAN is the central stress system conceptualized by Chrousos and Gold. According to the allostasis concept, homeostatic input-output curves can be altered in an anticipatory, feed-forward manner; and prolonged or inappropriate allostatic adjustments increase wear-and-tear (allostatic load), resulting in chronic, stress-related, multi-system disorders. This review concludes with sections on clinical and therapeutic implications of the updated concepts offered here.
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Affiliation(s)
- David S Goldstein
- Autonomic Medicine Section, Clinical Neurosciences Program, Division of Intramural Research, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA; Autonomic Medicine Section, CNP/DIR/NINDS/NIH, 9000 Rockville Pike MSC-1620, Building 10 Room 8N260, Bethesda, MD 20892-1620, USA..
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8
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Sides MB, Johnston SL, Sirek A, Lee PH, Blue RS, Antonsen EL, Basner M, Douglas GL, Epstein A, Flynn-Evans EE, Gallagher MB, Hayes J, Lee SMC, Lockley SW, Monseur B, Nelson NG, Sargsyan A, Smith SM, Stenger MB, Stepanek J, Zwart SR. Bellagio II Report: Terrestrial Applications of Space Medicine Research. Aerosp Med Hum Perform 2021; 92:650-669. [PMID: 34503618 DOI: 10.3357/amhp.5843.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
AbstractINTRODUCTION: For over 50 yr, investigators have studied the physiological adaptations of the human system during short- and long-duration spaceflight exposures. Much of the knowledge gained in developing health countermeasures for astronauts onboard the International Space Station demonstrate terrestrial applications. To date, a systematic process for translating these space applications to terrestrial human health has yet to be defined.METHODS: In the summer of 2017, a team of 38 international scientists launched the Bellagio ll Summit Initiative. The goals of the Summit were: 1) To identify space medicine findings and countermeasures with highest probability for future terrestrial applications; and 2) To develop a roadmap for translation of these countermeasures to future terrestrial application. The team reviewed public domain literature, NASA databases, and evidence books within the framework of the five-stage National Institutes of Health (NIH) translation science model, and the NASA two-stage translation model. Teams then analyzed and discussed interdisciplinary findings to determine the most significant evidence-based countermeasures sufficiently developed for terrestrial application.RESULTS: Teams identified published human spaceflight research and applied translational science models to define mature products for terrestrial clinical practice.CONCLUSIONS: The Bellagio ll Summit identified a snapshot of space medicine research and mature science with the highest probability of translation and developed a Roadmap of terrestrial application from space medicine-derived countermeasures. These evidence-based findings can provide guidance regarding the terrestrial applications of best practices, countermeasures, and clinical protocols currently used in spaceflight.Sides MB, Johnston SL III, Sirek A, Lee PH, Blue RS, Antonsen EL, Basner M, Douglas GL, Epstein A, Flynn-Evans EE, Gallagher MB, Hayes J, Lee SMC, Lockley SW, Monseur B, Nelson NG, Sargsyan A, Smith SM, Stenger MB, Stepanek J, Zwart SR; Bellagio II Team. Bellagio II report: terrestrial applications of space medicine research. Aerosp Med Hum Perform. 2021; 92(8):650669.
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9
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Roberts DR, Collins HR, Lee JK, Taylor JA, Turner M, Zaharchuk G, Wintermark M, Antonucci MU, Mulder ER, Gerlach DA, Asemani D, McGregor HR, Seidler RD. Altered cerebral perfusion in response to chronic mild hypercapnia and head-down tilt Bed rest as an analog for Spaceflight. Neuroradiology 2021; 63:1271-1281. [PMID: 33587162 DOI: 10.1007/s00234-021-02660-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 01/26/2021] [Indexed: 01/01/2023]
Abstract
PURPOSE Following prolonged stays on the International Space Station (ISS), some astronauts exhibit visual acuity changes, ophthalmological findings, and mildly elevated intracranial pressures as part of a novel process called spaceflight-associated neuro-ocular syndrome (SANS). To determine the pathophysiology of SANS, NASA conducted a multi-investigator study in which 11 healthy participants underwent head-down tilt bed rest, mimicking microgravity-induced cephalad fluid shifts, combined with elevated ambient CO2 levels similar to those on the ISS (HDT+CO2). As part of that study, we examined the effects of HDT+CO2 on cerebral perfusion. METHODS Using arterial spin labeling, we compared cerebral perfusion before, during, and after HDT+CO2 in participants who developed SANS (n = 5) with those who did not (n = 6). RESULTS All participants demonstrated a decrease in perfusion during HDT+CO2 (mean decrease of 25.1% at HDT7 and 16.2% at HDT29); however, the timing and degree of change varied between the groups. At day 7 of HDT+CO2, the SANS group experienced a greater reduction in perfusion than the non-SANS group (p =.05, 95% CI:-0.19 to 16.11, d=.94, large effect). Conversely, by day 29 of HDT+CO2, the SANS group had significantly higher perfusion (approaching their baseline) than the non-SANS group (p = .04, 95% CI:0.33 to 13.07, d=1.01, large effect). CONCLUSION Compared with baseline and recovery, HDT+CO2 resulted in reduced cerebral perfusion which varied based on SANS status. Further studies are needed to unravel the relative role of HDT vs hypercapnia, to determine if these perfusion changes are clinically relevant, and whether perfusion changes contribute to the development of SANS during spaceflight.
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Affiliation(s)
- Donna R Roberts
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA. .,Department of Neuroscience, Medical University of South Carolina, Charleston, SC, USA.
| | - Heather R Collins
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA
| | - Jessica K Lee
- German Aerospace Center (DLR, Institute of Aerospace Medicine), Cologne, Germany.,Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, USA
| | - James A Taylor
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA
| | - Matthew Turner
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA
| | - Greg Zaharchuk
- Department of Radiology, Division of Neuroradiology, Stanford University, Stanford, CA, USA
| | - Max Wintermark
- Department of Radiology, Division of Neuroradiology, Stanford University, Stanford, CA, USA
| | - Michael U Antonucci
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA
| | - Edwin R Mulder
- German Aerospace Center (DLR, Institute of Aerospace Medicine), Cologne, Germany
| | - Darius A Gerlach
- German Aerospace Center (DLR, Institute of Aerospace Medicine), Cologne, Germany
| | - Davud Asemani
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA
| | - Heather R McGregor
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, USA
| | - Rachael D Seidler
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, USA.,Norman Fixel Institute for Neurological Diseases, College of Health and Human Performance, University of Florida, Gainesville, FL, USA
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10
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Lee SMC, Ribeiro LC, Laurie SS, Feiveson AH, Kitov VV, Kofman IS, Macias BR, Rosenberg M, Rukavishnikov IV, Tomilovskaya ES, Bloomberg JJ, Kozlovskaya IB, Reschke MF, Stenger MB. Efficacy of Gradient Compression Garments in the Hours After Long-Duration Spaceflight. Front Physiol 2020; 11:784. [PMID: 32765292 PMCID: PMC7379894 DOI: 10.3389/fphys.2020.00784] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 06/15/2020] [Indexed: 11/20/2022] Open
Abstract
The incidence of presyncopal events is high soon after a long-duration spaceflight;>60% of returning astronauts could not complete a 10-min 80° head-up tilt test on landing day (R+0) after ~6 months of spaceflight. The objective of this study was to demonstrate the ability of a lower body gradient compression garment (GCG) to protect against an excessive increase in heart rate and a decrease in blood pressure during standing after long-duration spaceflight. Methods: Eleven astronauts (9 M, 2 F) volunteered to participate. The stand test protocol consisted of 2 min of prone rest followed by 3.5 min of standing. Subjects completed one familiarization session, two preflight data collection sessions in standard clothing, and three tests on landing day while wearing GCG. Postflight tests were conducted 1–4 h (R+0A), ~12 h (R+0B), and ~28 h after landing (R+0C). Results: All astronauts completed the stand test preflight. Three astronauts were unable to attempt the stand test at R+0A, and one of these was unable to start the test at R+0B. One astronaut was unable to complete 3.5 min of standing at R+0B (test ended at 3.3 min). Review of the individual’s blood pressure data revealed no hypotension but the astronaut reported significant motion sickness. Of the astronauts who participated in testing on landing day, the heart rate and mean arterial pressure responses to standing (stand-prone) were not different than preflight at any of the postflight sessions. Conclusion: Wearing the GCG after spaceflight prevented the tachycardia that normally occurs while standing after spaceflight without compression garments and protected against a decrease in blood pressure during a short stand test.
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Affiliation(s)
| | | | | | - Alan H Feiveson
- Lyndon B. Johnson Space Center, National Aeronautics and Space Administration, Houston, TX, United States
| | - Vladimir V Kitov
- Department of Sensory-Motor Physiology and Countermeasures, Institute of Biomedical Problems of the Russian Academy of Sciences, Moscow, Russia
| | | | | | | | - Ilya V Rukavishnikov
- Department of Sensory-Motor Physiology and Countermeasures, Institute of Biomedical Problems of the Russian Academy of Sciences, Moscow, Russia
| | - Elena S Tomilovskaya
- Department of Sensory-Motor Physiology and Countermeasures, Institute of Biomedical Problems of the Russian Academy of Sciences, Moscow, Russia
| | - Jacob J Bloomberg
- Lyndon B. Johnson Space Center, National Aeronautics and Space Administration, Houston, TX, United States
| | - Inessa B Kozlovskaya
- Department of Sensory-Motor Physiology and Countermeasures, Institute of Biomedical Problems of the Russian Academy of Sciences, Moscow, Russia
| | - Millard F Reschke
- Lyndon B. Johnson Space Center, National Aeronautics and Space Administration, Houston, TX, United States
| | - Michael B Stenger
- Lyndon B. Johnson Space Center, National Aeronautics and Space Administration, Houston, TX, United States
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11
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Kermorgant M, Nasr N, Czosnyka M, Arvanitis DN, Hélissen O, Senard JM, Pavy-Le Traon A. Impacts of Microgravity Analogs to Spaceflight on Cerebral Autoregulation. Front Physiol 2020; 11:778. [PMID: 32719617 PMCID: PMC7350784 DOI: 10.3389/fphys.2020.00778] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Accepted: 06/15/2020] [Indexed: 12/16/2022] Open
Abstract
It is well known that exposure to microgravity in astronauts leads to a plethora physiological responses such as headward fluid shift, body unloading, and cardiovascular deconditioning. When astronauts return to Earth, some encounter problems related to orthostatic intolerance. An impaired cerebral autoregulation (CA), which could be compromised by the effects of microgravity, has been proposed as one of the mechanisms responsible for orthostatic intolerance. CA is a homeostatic mechanism that maintains cerebral blood flow for any variations in cerebral perfusion pressure by adapting the vascular tone and cerebral vessel diameter. The ground-based models of microgravity are useful tools for determining the gravitational impact of spaceflight on human body. The head-down tilt bed rest (HDTBR), where the subject remains in supine position at −6 degrees for periods ranging from few days to several weeks is the most commonly used ground-based model of microgravity for cardiovascular deconditioning. head-down bed rest (HDBR) is able to replicate cephalic fluid shift, immobilization, confinement, and inactivity. Dry immersion (DI) model is another approach where the subject remains immersed in thermoneutral water covered with an elastic waterproof fabric separating the subject from the water. Regarding DI, this analog imitates absence of any supporting structure for the body, centralization of body fluids, immobilization and hypokinesia observed during spaceflight. However, little is known about the impact of microgravity on CA. Here, we review the fundamental principles and the different mechanisms involved in CA. We also consider the different approaches in order to assess CA. Finally, we focus on the effects of short- and long-term spaceflight on CA and compare these findings with two specific analogs to microgravity: HDBR and DI.
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Affiliation(s)
- Marc Kermorgant
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
| | - Nathalie Nasr
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France.,Department of Neurology, Institute for Neurosciences, Toulouse University Hospital, Toulouse, France
| | - Marek Czosnyka
- Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Cambridge University Hospital, Cambridge, United Kingdom.,Institute of Electronic Systems, Warsaw University of Technology, Warsaw, Poland
| | - Dina N Arvanitis
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
| | - Ophélie Hélissen
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France
| | - Jean-Michel Senard
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France.,Department of Clinical Pharmacology, Toulouse University Hospital, Toulouse, France
| | - Anne Pavy-Le Traon
- INSERM UMR 1048, Institute of Cardiovascular and Metabolic Diseases (I2MC), Toulouse, France.,Department of Neurology, Institute for Neurosciences, Toulouse University Hospital, Toulouse, France
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12
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Palacios S, Caiani EG, Landreani F, Martínez JP, Pueyo E. Long-Term Microgravity Exposure Increases ECG Repolarization Instability Manifested by Low-Frequency Oscillations of T-Wave Vector. Front Physiol 2019; 10:1510. [PMID: 31920714 PMCID: PMC6928004 DOI: 10.3389/fphys.2019.01510] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 11/29/2019] [Indexed: 11/13/2022] Open
Abstract
Ventricular arrhythmias and sudden cardiac death during long-term space missions are a major concern for space agencies. Long-duration spaceflight and its ground-based analog head-down bed rest (HDBR) have been reported to markedly alter autonomic and cardiac functioning, particularly affecting ventricular repolarization of the electrocardiogram (ECG). In this study, novel methods are developed, departing from previously published methodologies, to quantify the index of Periodic Repolarization Dynamics (PRD), an arrhythmic risk marker that characterizes sympathetically-mediated low-frequency oscillations in the T-wave vector. PRD is evaluated in ECGs from 42 volunteers at rest and during an orthostatic tilt table test recorded before and after 60-day –6° HDBR. Our results indicate that tilt test, on top of enhancing sympathetic regulation of heart rate, notably increases PRD, both before and after HDBR, thus supporting previous evidence on PRD being an indicator of sympathetic modulation of ventricular repolarization. Importantly, long-term microgravity exposure is shown to lead to significant increases in PRD, both when evaluated at rest and, even more notably, in response to tilt test. The extent of microgravity-induced changes in PRD has been associated with arrhythmic risk in prior studies. An exercise-based, but not a nutrition-based, countermeasure is able to partially reverse microgravity-induced effects on PRD. In conclusion, long-term exposure to microgravity conditions leads to elevated low-frequency oscillations of ventricular repolarization, which are potentiated following sympathetic stimulation and are related to increased risk for repolarization instabilities and arrhythmias. Tested countermeasures are only partially effective in counteracting microgravity effects.
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Affiliation(s)
- Saúl Palacios
- BSICoS Group, Aragón Institute of Engineering Research, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain
| | - Enrico G Caiani
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Federica Landreani
- Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy
| | - Juan Pablo Martínez
- BSICoS Group, Aragón Institute of Engineering Research, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain.,CIBER en Bioingeniería, Biomateriales y Nanomedicina, Madrid, Spain
| | - Esther Pueyo
- BSICoS Group, Aragón Institute of Engineering Research, IIS Aragón, Universidad de Zaragoza, Zaragoza, Spain.,CIBER en Bioingeniería, Biomateriales y Nanomedicina, Madrid, Spain
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Wood KN, Murray KR, Greaves DK, Hughson RL. Inflight leg cuff test does not identify the risk for orthostatic hypotension after long-duration spaceflight. NPJ Microgravity 2019; 5:22. [PMID: 31633009 PMCID: PMC6789148 DOI: 10.1038/s41526-019-0082-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 09/18/2019] [Indexed: 11/09/2022] Open
Abstract
Landing day symptoms from orthostatic hypotension after prolonged spaceflight can be debilitating, but severity of these symptoms can be unpredictable and highly individual. We tested the hypothesis that an impaired baroreflex response to an inflight leg cuff test could predict orthostatic intolerance on return to Earth. Eight male astronauts (44 ± 7 years of age (mean ± SD); mean mission length: 167 ± 12 days) participated in a standardized supine-to-sit-to-stand test (5 min-30s-3 min) pre- and postflight, and a 3 min thigh cuff occlusion test pre- and inflight with continuous monitoring of heart rate and arterial blood pressure. The arterial baroreflex was not changed inflight as shown by similar reductions in mean arterial pressure (MAP) response to leg cuff deflation (preflight -19 ± 2 mmHg vs. inflight -18 ± 5 mmHg). With the sit/stand test, the nadir of MAP was lower postflight (-17 ± 9 mmHg) than preflight (-11 ± 6 mmHg, p < 0.05). A greater increase in heart rate (25 ± 7; 16 ± 3 bpm) and decrease in stroke volume (-24 ± 11; -6 ± 4 mL) occurred with sit/stand postflight than leg cuffs inflight (p < 0.001). Inflight testing was influenced by elevated cardiac output resulting in a smaller drop in total peripheral resistance. Two of eight subjects exhibited orthostatic hypotension during the postflight stand test; their responses were not predicted by the inflight leg cuff deflation test. These results suggest that the baroreflex response examined by inflight leg cuff deflation was not a reliable indicator of postflight stand responses.
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Affiliation(s)
- Katelyn N Wood
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON Canada
| | - Kevin R Murray
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON Canada
| | - Danielle K Greaves
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON Canada
| | - Richard L Hughson
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON Canada
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14
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Fu Q, Shibata S, Hastings JL, Platts SH, Hamilton DM, Bungo MW, Stenger MB, Ribeiro C, Adams-Huet B, Levine BD. Impact of Prolonged Spaceflight on Orthostatic Tolerance During Ambulation and Blood Pressure Profiles in Astronauts. Circulation 2019; 140:729-738. [DOI: 10.1161/circulationaha.119.041050] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Background:
Astronauts returning to earth usually demonstrate reduced orthostatic tolerance when assessed on a tilt table or quiet standing, but no studies have evaluated postflight orthostatic tolerance during activities of daily living, when it is most clinically relevant. Ambulatory blood pressure (BP) variability also is associated with orthostatic intolerance in certain patient populations and can capture clinically significant orthostatic hypotension during activities of daily living, especially when measured on a beat-to-beat basis. We evaluated the impact of prolonged spaceflight on orthostatic tolerance and BP profiles in astronauts.
Methods:
Ambulatory beat-to-beat BP was recorded using a portable device for multiple 24-hour time periods before, during, and after 6 months of spaceflight in 12 astronauts (4 women; age 48±5 [mean±SD] years). BP variability in the time domain was calculated as the SD. Systolic BP distribution during activities of daily living was characterized by skewness and kurtosis.
Results:
In contrast with results from previous studies that used tilt tables or stand tests, no astronaut experienced orthostatic intolerance/hypotension during activities of daily living before or after spaceflight. Also, 24-hour systolic BP decreased in space (120±10 mm Hg before spaceflight versus 106±9 mm Hg during spaceflight;
P
<0.01), but it returned to normal upon landing (122±13 mm Hg). Diastolic BP was unchanged during and after spaceflight. Systolic and diastolic BP variability remained the same before, during, and after spaceflight (both
P
>0.05). The skewness of systolic BP increased in space (0.74±0.51 versus 1.43±1.00;
P
=0.001), indicating that signal fluctuations became asymmetrical; however, it returned to preflight levels after landing (0.51±0.42). The kurtosis increased in space (5.01±7.67 versus 11.10±11.79;
P
=0.010), suggesting that fluctuations concentrated around the mean with a narrow distribution; however, it also returned to preflight levels (2.21±2.56) after return to earth.
Conclusions:
Given current countermeasures including in-flight exercise training and volume resuscitation on return, no astronauts experienced orthostatic hypotension or intolerance during routine (for landing day) activities in the initial 24 hours after landing following 6 months in space. Prolonged exposure to spaceflight had little impact on systolic BP variability and its distribution, although the latter showed a transient change in space (accompanied by mild relative hypotension), all of which returned to preflight values after return to earth.
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Affiliation(s)
- Qi Fu
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas (Q.F., S.S., B.D.L.)
- The University of Texas Southwestern Medical Center, Dallas (Q.F., S.S., J.L.H., B.A.-H., B.D.L.)
| | - Shigeki Shibata
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas (Q.F., S.S., B.D.L.)
- The University of Texas Southwestern Medical Center, Dallas (Q.F., S.S., J.L.H., B.A.-H., B.D.L.)
| | - Jeffrey L. Hastings
- The University of Texas Southwestern Medical Center, Dallas (Q.F., S.S., J.L.H., B.A.-H., B.D.L.)
| | - Steven H. Platts
- NASA Johnson Space Center, Houston, TX (S.H.P., D.M.H., M.B.S., C.R.)
| | - Douglas M. Hamilton
- NASA Johnson Space Center, Houston, TX (S.H.P., D.M.H., M.B.S., C.R.)
- The University of Calgary, Alberta, Canada (D.M.H.)
| | - Michael W. Bungo
- The University of Texas McGovern Medical School, Houston (M.W.B.)
| | | | - Christine Ribeiro
- NASA Johnson Space Center, Houston, TX (S.H.P., D.M.H., M.B.S., C.R.)
| | - Beverley Adams-Huet
- The University of Texas Southwestern Medical Center, Dallas (Q.F., S.S., J.L.H., B.A.-H., B.D.L.)
| | - Benjamin D. Levine
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas (Q.F., S.S., B.D.L.)
- The University of Texas Southwestern Medical Center, Dallas (Q.F., S.S., J.L.H., B.A.-H., B.D.L.)
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15
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Sachse C, Trozic I, Brix B, Roessler A, Goswami N. Sex differences in cardiovascular responses to orthostatic challenge in healthy older persons: A pilot study. Physiol Int 2019; 106:236-249. [DOI: 10.1556/2060.106.2019.16] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Background
Premenopausal women show a higher incidence of orthostatic hypotension than age-matched men, but there are limited data available on sex differences in cardiovascular responses to orthostatic challenge in healthy older persons. We investigated sex differences in hemodynamic and autonomic responses to orthostatic challenge in healthy older males and females.
Materials and methods
Fourteen older healthy women and 10 age-matched men performed a sit-to-stand test (5 min of sitting followed by 5 min of standing). A Task Force® Monitor continuously measured the following beat-to-beat hemodynamic parameters: heart rate, systolic blood pressure, diastolic blood pressure, mean blood pressure, stroke index, cardiac index, and total peripheral resistance index. Cardiac autonomic activity, low-frequency (LF: 0.04–0.15 Hz) normalized (LFnuRRI) and high-frequency (HF: 0.15–0.4 Hz) normalized (HFnuRRI) components, and the ratio between LF and HF power (LF/HF) were calculated using power spectral analysis of heart rate variability.
Results
Across all hemodynamic parameters, there were no significant differences between the sexes at baseline and during standing. LFnuRRI (median: 70.2 vs. 52.3, p < 0.05) and LF/HF ratio (median: 2.4 vs. 1.1, p < 0.05) were significantly higher, whereas HFnuRRI (median: 29.8 vs. 47.7, p < 0.05) was lower among women at baseline. All other heart rate variability measures did not differ between the sexes.
Conclusions
The data indicate that older women showed higher sympathetic and lower parasympathetic activity at rest compared to age-matched men. These results are contradictory to the observations from previous studies, which showed a reduced sympathetic and enhanced parasympathetic activity in women in all ages. Further studies are required to determine the underlying mechanisms contributing to higher incidence of orthostatic hypotension in older females.
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Affiliation(s)
- C Sachse
- 1 Gravitational Physiology and Medicine Research Unit, Physiology Division, Otto Loewi Center of Research in Vascular Biology, Immunity and Inflammation, Medical University of Graz, Graz, Austria
| | - I Trozic
- 1 Gravitational Physiology and Medicine Research Unit, Physiology Division, Otto Loewi Center of Research in Vascular Biology, Immunity and Inflammation, Medical University of Graz, Graz, Austria
| | - B Brix
- 1 Gravitational Physiology and Medicine Research Unit, Physiology Division, Otto Loewi Center of Research in Vascular Biology, Immunity and Inflammation, Medical University of Graz, Graz, Austria
| | - A Roessler
- 1 Gravitational Physiology and Medicine Research Unit, Physiology Division, Otto Loewi Center of Research in Vascular Biology, Immunity and Inflammation, Medical University of Graz, Graz, Austria
| | - N Goswami
- 1 Gravitational Physiology and Medicine Research Unit, Physiology Division, Otto Loewi Center of Research in Vascular Biology, Immunity and Inflammation, Medical University of Graz, Graz, Austria
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16
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Bryarly M, Phillips LT, Fu Q, Vernino S, Levine BD. Postural Orthostatic Tachycardia Syndrome. J Am Coll Cardiol 2019; 73:1207-1228. [DOI: 10.1016/j.jacc.2018.11.059] [Citation(s) in RCA: 93] [Impact Index Per Article: 18.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 11/01/2018] [Accepted: 11/05/2018] [Indexed: 12/26/2022]
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17
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Goswami N, Blaber AP, Hinghofer-Szalkay H, Convertino VA. Lower Body Negative Pressure: Physiological Effects, Applications, and Implementation. Physiol Rev 2019; 99:807-851. [PMID: 30540225 DOI: 10.1152/physrev.00006.2018] [Citation(s) in RCA: 109] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
This review presents lower body negative pressure (LBNP) as a unique tool to investigate the physiology of integrated systemic compensatory responses to altered hemodynamic patterns during conditions of central hypovolemia in humans. An early review published in Physiological Reviews over 40 yr ago (Wolthuis et al. Physiol Rev 54: 566-595, 1974) focused on the use of LBNP as a tool to study effects of central hypovolemia, while more than a decade ago a review appeared that focused on LBNP as a model of hemorrhagic shock (Cooke et al. J Appl Physiol (1985) 96: 1249-1261, 2004). Since then there has been a great deal of new research that has applied LBNP to investigate complex physiological responses to a variety of challenges including orthostasis, hemorrhage, and other important stressors seen in humans such as microgravity encountered during spaceflight. The LBNP stimulus has provided novel insights into the physiology underlying areas such as intolerance to reduced central blood volume, sex differences concerning blood pressure regulation, autonomic dysfunctions, adaptations to exercise training, and effects of space flight. Furthermore, approaching cardiovascular assessment using prediction models for orthostatic capacity in healthy populations, derived from LBNP tolerance protocols, has provided important insights into the mechanisms of orthostatic hypotension and central hypovolemia, especially in some patient populations as well as in healthy subjects. This review also presents a concise discussion of mathematical modeling regarding compensatory responses induced by LBNP. Given the diverse applications of LBNP, it is to be expected that new and innovative applications of LBNP will be developed to explore the complex physiological mechanisms that underline health and disease.
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Affiliation(s)
- Nandu Goswami
- Physiology Section, Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz , Graz , Austria ; Department of Biomedical Physiology and Kinesiology, Simon Fraser University , Burnaby, British Columbia , Canada ; Battlefield Health & Trauma Center for Human Integrative Physiology, Combat Casualty Care Research Program, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
| | - Andrew Philip Blaber
- Physiology Section, Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz , Graz , Austria ; Department of Biomedical Physiology and Kinesiology, Simon Fraser University , Burnaby, British Columbia , Canada ; Battlefield Health & Trauma Center for Human Integrative Physiology, Combat Casualty Care Research Program, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
| | - Helmut Hinghofer-Szalkay
- Physiology Section, Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz , Graz , Austria ; Department of Biomedical Physiology and Kinesiology, Simon Fraser University , Burnaby, British Columbia , Canada ; Battlefield Health & Trauma Center for Human Integrative Physiology, Combat Casualty Care Research Program, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
| | - Victor A Convertino
- Physiology Section, Otto Loewi Research Center for Vascular Biology, Immunology and Inflammation, Medical University of Graz , Graz , Austria ; Department of Biomedical Physiology and Kinesiology, Simon Fraser University , Burnaby, British Columbia , Canada ; Battlefield Health & Trauma Center for Human Integrative Physiology, Combat Casualty Care Research Program, US Army Institute of Surgical Research, JBSA Fort Sam Houston, Texas
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18
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Edgell H, Grinberg A, Beavers KR, Gagné N, Hughson RL. Efficacy of fluid loading as a countermeasure to the hemodynamic and hormonal changes of 28-h head-down bed rest. Physiol Rep 2018; 6:e13874. [PMID: 30298552 PMCID: PMC6175712 DOI: 10.14814/phy2.13874] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Accepted: 08/26/2018] [Indexed: 11/24/2022] Open
Abstract
After exposure to microgravity, or head-down bed rest (HDBR), fluid loading is often used with the intent of increasing plasma volume and maintaining mean arterial pressure during orthostatic stress. Nine men (aged 18-32 years) underwent three randomized trials with lower body negative pressure (LBNP) before and after: (1) 4-h of sitting with fluid loading (1 g sodium chloride/125 mL of water starting 2.5-h before LBNP), (2) 28-h of 6-degree HDBR without fluid loading, and (3) 28-h of 6-degree HDBR with fluid loading. LBNP was progressive from 0 to -40 mmHg. After 28-h HDBR, fluid loading did not protect against the loss of plasma volume (-280 ± 64 mL without fluid loading, -207 ± 86 with fluid loading, P = 0.472) nor did it protect against a drop of mean arterial pressure (P = 0.017) during LBNP (Post-28 h HDBR response from 0 to -40 mmHg LBNP: 88 ± 4 to 85 ± 4 mmHg without fluid loading and 93 ± 4 to 88 ± 5 mmHg with fluid loading, P = 0.557 between trials). However, fluid loading did protect against the loss of stroke volume index and central venous pressure observed after 28-h HDBR. Fluid loading also attenuated the increase of angiotensin II seen after 28-h HDBR and throughout the LBNP protocol (Post-28 h HDBR response from 0 to -40 mmHg LBNP: 16.6 ± 3.4 to 23.7 ± 5.0 pg/mL without fluid loading and 6.1 ± 0.8 to 12.2 ± 2.3 pg/mL with fluid loading, P < 0.001 between trials). Our results indicate that fluid loading did not protect against plasma volume loss due to HDBR or change blood pressure responses to LBNP. However, changes in central venous pressure, stroke volume and fluid regulatory hormones could potentially influence longer duration studies and those with more severe orthostatic stress.
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Affiliation(s)
- Heather Edgell
- Faculty of Applied Health SciencesUniversity of WaterlooWaterlooOntarioCanada
- School of Kinesiology and Health SciencesYork UniversityTorontoOntarioCanada
| | - Anna Grinberg
- Faculty of Applied Health SciencesUniversity of WaterlooWaterlooOntarioCanada
| | - Keith R. Beavers
- Faculty of Applied Health SciencesUniversity of WaterlooWaterlooOntarioCanada
| | - Nathalie Gagné
- Faculty of Applied Health SciencesUniversity of WaterlooWaterlooOntarioCanada
| | - Richard L. Hughson
- Faculty of Applied Health SciencesUniversity of WaterlooWaterlooOntarioCanada
- Schlegel‐University of Waterloo Research Institute for AgingWaterlooOntarioCanada
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19
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Klassen SA, De Abreu S, Greaves DK, Kimmerly DS, Arbeille P, Denise P, Hughson RL, Normand H, Shoemaker JK. Long-duration bed rest modifies sympathetic neural recruitment strategies in male and female participants. J Appl Physiol (1985) 2018; 124:769-779. [PMID: 29212669 PMCID: PMC5899270 DOI: 10.1152/japplphysiol.00640.2017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 11/09/2017] [Accepted: 12/04/2017] [Indexed: 01/07/2023] Open
Abstract
To understand the impact of physical deconditioning with head-down tilt bed rest (HDBR) on the malleability of sympathetic discharge patterns, we studied 1) baseline integrated muscle sympathetic nerve activity (MSNA; microneurography) from 13 female participants in the WISE-2005 60-day HDBR study (retrospective analysis), 2) integrated MSNA and multiunit action potential (AP) analysis in 13 male participants performed on data collected at baseline and during physiological stress imposed by end-inspiratory apnea in a new 60-day HDBR study, and 3) a repeatability study (control; n = 6, retrospective analysis, 4 wk between tests). Neither baseline integrated burst frequency nor incidence were altered with HDBR (both P > 0.35). However, baseline integrated burst latency increased in both HDBR studies (male: 1.35 ± 0.02 to 1.39 ± 0.02 s, P < 0.01; female: 1.23 ± 0.02 to 1.29 ± 0.02 s, P < 0.01), whereas controls exhibited no change across two visits (1.25 ± 0.02 to 1.25 ± 0.02 s, group-by-time interaction, P = 0.02). With the exception of increased AP latency ( P = 0.03), male baseline AP data did not change with HDBR (all P > 0.19). The change in AP frequency on going from baseline to apnea (∆94 ± 25 to ∆317 ± 55 AP/min, P < 0.01) and the number of active sympathetic clusters per burst (∆0 ± 0.2 to ∆1 ± 0.2 clusters/burst, P = 0.02) were greater post- compared with pre-HDBR. The change in total clusters with apnea was ∆0 ± 0.5 clusters pre- and ∆2 ± 0.7 clusters post-HDBR ( P = 0.07). These data indicate that 60-day HDBR modified discharge characteristics in baseline burst latency and sympathetic neural recruitment during apneic stress. NEW & NOTEWORTHY Long-duration bed rest did not modify baseline sympathetic burst frequency in male and female participants, but examination of additional features of the multiunit signal provided novel evidence to suggest augmented synaptic delays or processing times at baseline for all sympathetic action potentials. Furthermore, long-duration bed rest increased reflex-sympathetic arousal to apneic stress in male participants primarily by mechanisms involving an augmented firing rate of action potential clusters active at baseline.
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Affiliation(s)
- Stephen A Klassen
- Neurovascular Research Laboratory, School of Kinesiology, University of Western Ontario , London, Ontario , Canada
| | | | - Danielle K Greaves
- Schlegel-University of Waterloo Research Institute for Aging , Waterloo, Ontario , Canada
| | - Derek S Kimmerly
- Division of Kinesiology, School of Health and Human Performance, Dalhousie University , Halifax, Nova Scotia , Canada
| | - Philippe Arbeille
- UMPS-CERCOM, School of Medicine, University of Tours , Tours , France
| | - Pierre Denise
- Normandie Université, Unicaen, INSERM, Caen , France
| | - Richard L Hughson
- Schlegel-University of Waterloo Research Institute for Aging , Waterloo, Ontario , Canada
| | - Hervé Normand
- Normandie Université, Unicaen, INSERM, Caen , France
| | - J Kevin Shoemaker
- Neurovascular Research Laboratory, School of Kinesiology, University of Western Ontario , London, Ontario , Canada
- Department of Physiology and Pharmacology, University of Western Ontario , London, Ontario , Canada
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20
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Strassheim V, Ballantine R, Hackett KL, Frith J, Newton JL. Understanding severely affected chronic fatigue syndrome (CFS): the gravity of the situation. PHYSICAL THERAPY REVIEWS 2017. [DOI: 10.1080/10833196.2017.1327131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Victoria Strassheim
- CRESTA Fatigue Clinic, Newcastle upon Tyne Hospitals, NHS Foundation Trust, Newcastle upon Tyne, UK
- Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - Robert Ballantine
- Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - Katie L. Hackett
- CRESTA Fatigue Clinic, Newcastle upon Tyne Hospitals, NHS Foundation Trust, Newcastle upon Tyne, UK
- Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - James Frith
- Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, UK
| | - Julia L. Newton
- CRESTA Fatigue Clinic, Newcastle upon Tyne Hospitals, NHS Foundation Trust, Newcastle upon Tyne, UK
- Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, UK
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21
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Tanaka K, Nishimura N, Kawai Y. Adaptation to microgravity, deconditioning, and countermeasures. J Physiol Sci 2017; 67:271-281. [PMID: 28000175 PMCID: PMC10717636 DOI: 10.1007/s12576-016-0514-8] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 12/07/2016] [Indexed: 02/01/2023]
Abstract
Humans are generally in standing or sitting positions on Earth during the day. The musculoskeletal system supports these positions and also allows motion. Gravity acting in the longitudinal direction of the body generates a hydrostatic pressure difference and induces footward fluid shift. The vestibular system senses the gravity of the body and reflexively controls the organs. During spaceflight or exposure to microgravity, the load on the musculoskeletal system and hydrostatic pressure difference is diminished. Thus, the skeletal muscle, particularly in the lower limbs, is atrophied, and bone minerals are lost via urinary excretion. In addition, the heart is atrophied, and the plasma volume is decreased, which may induce orthostatic intolerance. Vestibular-related control also declines; in particular, the otolith organs are more susceptible to exposure to microgravity than the semicircular canals. Using an advanced resistive exercise device with administration of bisphosphonate is an effective countermeasure against bone deconditioning. However, atrophy of skeletal muscle and the heart has not been completely prevented. Further ingenuity is needed in designing countermeasures for muscular, cardiovascular, and vestibular dysfunctions.
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Affiliation(s)
- Kunihiko Tanaka
- Graduate School of Health and Medicine, Gifu University of Medical Science, 795-1 Nagamine Ichihiraga, Seki, Gifu, 501-3892, Japan.
| | - Naoki Nishimura
- Department of Physiology, Faculty of Medicine, Aichi Medical School, 1-1 Yazakokarimata, Nagakute, Aichi, 480-1103, Japan
| | - Yasuaki Kawai
- Division of Adaptation Physiology, Faculty of Medicine, Tottori University, 86 Nishi-machi, Yonago, Tottori, 683-8503, Japan
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22
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Fu Q, Levine BD. Syncope prevention in blood donors: when to do what? Transfusion 2016; 56:2399-2402. [DOI: 10.1111/trf.13775] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 07/18/2016] [Indexed: 11/30/2022]
Affiliation(s)
- Qi Fu
- Institute for Exercise and Environmental Medicine; Texas Health Presbyterian Hospital Dallas; Dallas TX
| | - Benjamin D. Levine
- Institute for Exercise and Environmental Medicine; Texas Health Presbyterian Hospital Dallas; Dallas TX
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23
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Long-term exposure to microgravity impairs vestibulo-cardiovascular reflex. Sci Rep 2016; 6:33405. [PMID: 27634181 PMCID: PMC5025735 DOI: 10.1038/srep33405] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 08/26/2016] [Indexed: 01/30/2023] Open
Abstract
The vestibular system is known to have an important role in controlling blood pressure upon posture transition (vestibulo-cardiovascular reflex, VCR). However, under a different gravitational environment, the sensitivity of the vestibular system may be altered. Thus, the VCR may become less sensitive after spaceflight because of orthostatic intolerance potentially induced by long-term exposure to microgravity. To test this hypothesis in humans, we investigated the ability of the VCR to maintain blood pressure upon head-up tilt before and after a 4–6 months stay on the International Space Station. To detect the functional state of the VCR, galvanic vestibular stimulation (GVS) was applied. As GVS transiently interrupts the vestibular-mediated pressor response, impaired VCR is detected when the head-up tilt-induced blood pressure response does not depend on GVS. During the first 20 s of head-up tilt, a transient blood pressure increase (11.9 ± 1.6 mmHg) was observed at pre-spaceflight but not at 1–4 days after return from spaceflight. The magnitude of VCR recovered to the pre-spaceflight levels within 2 months after return. These results indicate that long-term exposure to microgravity induces VCR impairment, which may be involved in a mechanism of spaceflight-induced orthostatic intolerance.
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24
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Patel K, Rössler A, Lackner HK, Trozic I, Laing C, Lorr D, Green DA, Hinghofer-Szalkay H, Goswami N. Effect of postural changes on cardiovascular parameters across gender. Medicine (Baltimore) 2016; 95:e4149. [PMID: 27428203 PMCID: PMC4956797 DOI: 10.1097/md.0000000000004149] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
INTRODUCTION We investigated the effect of postural changes on various cardiovascular parameters across gender. Twenty-eight healthy subjects (16 male, 12 female) were observed at rest (supine) and subjected to 3 interventions; head-down tilt (HDT), HDT with lower body negative pressure (HDT+ LBNP at -30 mm Hg), and head-up tilt (HUT), each for 10 minutes separated by a 10 minutes recovery period. METHODS Measurements were recorded for heart rate (HR), standard deviation of the normal-to-normal intervals, root mean square of successive differences between the normal-to-normal intervals, heart rate variability-low frequency (LFRRI), heart rate variability-high frequency (HFRRI), low frequency/high frequency ratio (LFRRI/HFRRI), systolic blood pressure (SBP), mean arterial pressure (MAP), diastolic blood pressure (DBP), total peripheral resistance index (TPRI), stroke index (SI), cardiac index (CI), index of contractility (IC), left ventricular work index, and left ventricular ejection time. RESULTS Across all cardiovascular parameters, there was a significant main effect of the intervention applied but there was no significant main effect of gender across all parameters. CONCLUSIONS The results suggest that there are no specific gender differences in regards to the measured variables under the conditions of this study. Furthermore, these results suggest that in healthy subjects, there appears to be evidence that LBNP partially elicits similar cardiovascular responses to HUT, which supports the use of LBNP as an intervention to counteract the effects of central hypovolemia.
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Affiliation(s)
- Kieran Patel
- Gravitational Physiology and Medicine Research Unit, Institute of Physiology, Medical University of Graz, Graz, Austria
- Kings College, London, UK
| | - Andreas Rössler
- Gravitational Physiology and Medicine Research Unit, Institute of Physiology, Medical University of Graz, Graz, Austria
| | - Helmut Karl Lackner
- Gravitational Physiology and Medicine Research Unit, Institute of Physiology, Medical University of Graz, Graz, Austria
| | - Irhad Trozic
- Gravitational Physiology and Medicine Research Unit, Institute of Physiology, Medical University of Graz, Graz, Austria
| | - Charles Laing
- Kings College, London, UK
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - David Lorr
- Department of Neurophsiology, University of Linkoping, Sweden
| | - David A Green
- Gravitational Physiology and Medicine Research Unit, Institute of Physiology, Medical University of Graz, Graz, Austria
| | - Helmut Hinghofer-Szalkay
- Gravitational Physiology and Medicine Research Unit, Institute of Physiology, Medical University of Graz, Graz, Austria
| | - Nandu Goswami
- Gravitational Physiology and Medicine Research Unit, Institute of Physiology, Medical University of Graz, Graz, Austria
- Correspondence: Nandu Goswami Gravitational Physiology and Medicine Research Unit, Institute of Physiology, Medical University of Graz, Harrachgasse 21/ V, 8010 Graz, Austria (e-mail: )
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Hallgren E, Kornilova L, Fransen E, Glukhikh D, Moore ST, Clément G, Van Ombergen A, MacDougall H, Naumov I, Wuyts FL. Decreased otolith-mediated vestibular response in 25 astronauts induced by long-duration spaceflight. J Neurophysiol 2016; 115:3045-51. [PMID: 27009158 PMCID: PMC4922620 DOI: 10.1152/jn.00065.2016] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 03/17/2016] [Indexed: 11/22/2022] Open
Abstract
The information coming from the vestibular otolith organs is important for the brain when reflexively making appropriate visual and spinal corrections to maintain balance. Symptoms related to failed balance control and navigation are commonly observed in astronauts returning from space. To investigate the effect of microgravity exposure on the otoliths, we studied the otolith-mediated responses elicited by centrifugation in a group of 25 astronauts before and after 6 mo of spaceflight. Ocular counterrolling (OCR) is an otolith-driven reflex that is sensitive to head tilt with regard to gravity and tilts of the gravito-inertial acceleration vector during centrifugation. When comparing pre- and postflight OCR, we found a statistically significant decrease of the OCR response upon return. Nine days after return, the OCR was back at preflight level, indicating a full recovery. Our large study sample allows for more general physiological conclusions about the effect of prolonged microgravity on the otolith system. A deconditioned otolith system is thought to be the cause of several of the negative effects seen in returning astronauts, such as spatial disorientation and orthostatic intolerance. This knowledge should be taken into account for future long-term space missions.
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Affiliation(s)
- Emma Hallgren
- AUREA, (Antwerp University Research center for Equilibrium and Aerospace), Biomedical Physics, University of Antwerp, Antwerp, Belgium
| | | | - Erik Fransen
- StatUa Center for Statistics, University of Antwerp, Antwerp, Belgium
| | | | - Steven T Moore
- Mount Sinai School of Medicine Human Aerospace Laboratory, New York, New York
| | - Gilles Clément
- Lyon Neuroscience Research Center, University of Lyon, Lyon, France; and
| | - Angelique Van Ombergen
- AUREA, (Antwerp University Research center for Equilibrium and Aerospace), Biomedical Physics, University of Antwerp, Antwerp, Belgium
| | - Hamish MacDougall
- University of Sydney School of Psychology, Sydney, New South Wales, Australia
| | - Ivan Naumov
- Institute of Biomedical Problems, Moscow, Russia
| | - Floris L Wuyts
- AUREA, (Antwerp University Research center for Equilibrium and Aerospace), Biomedical Physics, University of Antwerp, Antwerp, Belgium;
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Hallgren E, Migeotte PF, Kornilova L, Delière Q, Fransen E, Glukhikh D, Moore ST, Clément G, Diedrich A, MacDougall H, Wuyts FL. Dysfunctional vestibular system causes a blood pressure drop in astronauts returning from space. Sci Rep 2015; 5:17627. [PMID: 26671177 PMCID: PMC4680856 DOI: 10.1038/srep17627] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 11/03/2015] [Indexed: 02/08/2023] Open
Abstract
It is a challenge for the human body to maintain stable blood pressure while standing. The body’s failure to do so can lead to dizziness or even fainting. For decades it has been postulated that the vestibular organ can prevent a drop in pressure during a position change – supposedly mediated by reflexes to the cardiovascular system. We show – for the first time – a significant correlation between decreased functionality of the vestibular otolith system and a decrease in the mean arterial pressure when a person stands up. Until now, no experiments on Earth could selectively suppress both otolith systems; astronauts returning from space are a unique group of subjects in this regard. Their otolith systems are being temporarily disturbed and at the same time they often suffer from blood pressure instability. In our study, we observed the functioning of both the otolith and the cardiovascular system of the astronauts before and after spaceflight. Our finding indicates that an intact otolith system plays an important role in preventing blood pressure instability during orthostatic challenges. Our finding not only has important implications for human space exploration; they may also improve the treatment of unstable blood pressure here on Earth.
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Affiliation(s)
- Emma Hallgren
- Antwerp University Research center for Equilibrium and Aerospace, Dept. of Biomedical Physics, University of Antwerp, Belgium
| | - Pierre-François Migeotte
- Université libre de Bruxelles &Erasmus Hospital, Department of Cardiology, Laboratory of Physics and Physiology, Brussels, Belgium
| | - Ludmila Kornilova
- Laboratory of Vestibular Physiology, Institute of Biomedical Problems of the Russian academy of sciences, Moscow, Russia
| | - Quentin Delière
- Université libre de Bruxelles &Erasmus Hospital, Department of Cardiology, Laboratory of Physics and Physiology, Brussels, Belgium
| | - Erik Fransen
- StatUa center for statistics, University of Antwerp, Antwerp, Belgium
| | - Dmitrii Glukhikh
- Laboratory of Vestibular Physiology, Institute of Biomedical Problems of the Russian academy of sciences, Moscow, Russia
| | - Steven T Moore
- Human Aerospace Laboratory, Icahn School of Medicine at Mount Sinai, New York City, USA
| | - Gilles Clément
- Lyon Neuroscience Research Center, IMPACT Team, University of Lyon, France
| | - André Diedrich
- Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Nashville, USA
| | - Hamish MacDougall
- Sydney Human Factors Research, School of Psychology, University of Sydney, Australia
| | - Floris L Wuyts
- Antwerp University Research center for Equilibrium and Aerospace, Dept. of Biomedical Physics, University of Antwerp, Belgium
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Hoffmann U, Moore AD, Koschate J, Drescher U. V̇O2 and HR kinetics before and after International Space Station missions. Eur J Appl Physiol 2015; 116:503-11. [PMID: 26662601 DOI: 10.1007/s00421-015-3298-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Accepted: 11/11/2015] [Indexed: 11/30/2022]
Abstract
PURPOSE Heart rate (HR), pulmonary and muscle oxygen uptake ([Formula: see text]O2pulm, [Formula: see text]O2musc) kinetics after changes of work rate (WR) indicate regulatory characteristics related to aerobic metabolism. We analysed whether the kinetics of HR, [Formula: see text]O2pulm and [Formula: see text]O2musc are slowed after missions to the International Space Station (ISS). The changes of the kinetics were correlated with [Formula: see text]O2peak data. METHODS 10 astronauts [4 females, 6 males, age: 48.0 ± 3.8 years, height: 176 ± 7 cm, mass: 74.5 ± 15.9 kg (mean ± SD)] performed an incremental test to determine [Formula: see text]O2peak (before missions on L-110 days, after return on R+1/+10/+36 days), and a cardio-respiratory kinetics test (CRKT) with randomized 30-80 W WR changes to determine HR, [Formula: see text]O2pulm and [Formula: see text]O2musc kinetics by time-series analysis (L-236/-73, R+6/+21). Kinetics were summarized by maximum and related lag of cross-correlation function (CCFmax, CCFlag) of WR with the analysed parameter. RESULTS Statistically, significant changes were also found for CCFmax([Formula: see text]O2musc) between L-236 and R+6 (P = 0.010), L-236 and R+21 (P = 0.030), L-72 and R+6 (P = 0.043). Between pre-to-post mission change in [Formula: see text]O2peak and CCFmax(HR), a correlation was shown (r SP = 0.67, P = 0.017). CONCLUSION The [Formula: see text]O2musc kinetics changes indicate aerobic detraining effects which are present up to 21 days following space flight. The correlations between changes in [Formula: see text]O2peak and HR kinetics illustrate the key role of cardiovascular regulation in [Formula: see text]O2peak. The addition of CRKT to ISS flight is recommended to obtain information regarding the potential muscular and cardiovascular deconditioning. This allows a reduction in the frequency of higher intensity testing during flight.
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Affiliation(s)
- U Hoffmann
- Institute of Physiology and Anatomy, German Sport University, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany.
| | - A D Moore
- Lamar University, Beaumont, TX, 77710, USA
| | - J Koschate
- Institute of Physiology and Anatomy, German Sport University, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany
| | - U Drescher
- Institute of Physiology and Anatomy, German Sport University, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany
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Habazettl H, Stahn A, Nitsche A, Nordine M, Pries AR, Gunga HC, Opatz O. Microvascular responses to (hyper-)gravitational stress by short-arm human centrifuge: arteriolar vasoconstriction and venous pooling. Eur J Appl Physiol 2015; 116:57-65. [PMID: 26280651 DOI: 10.1007/s00421-015-3241-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Accepted: 08/08/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE We hypothesized that lower body microvessels are particularly challenged during exposure to gravity and hypergravity leading to failure of resistance vessels to withstand excessive transmural pressure during hypergravitation and gravitation-dependent microvascular blood pooling. METHODS Using a short-arm human centrifuge (SAHC), 12 subjects were exposed to +1Gz, +2Gz and +1Gz, all at foot level, for 4 min each. Laser Doppler imaging and near-infrared spectroscopy were used to measure skin perfusion and tissue haemoglobin concentrations, respectively. RESULTS Pretibial skin perfusion decreased by 19% during +1Gz and remained at this level during +2Gz. In the dilated area, skin perfusion increased by 24 and 35% during +1Gz and +2Gz, respectively. In the upper arm, oxygenated haemoglobin (Hb) decreased, while deoxy Hb increased with little change in total Hb. In the calf muscle, O2Hb and deoxy Hb increased, resulting in total Hb increase by 7.5 ± 1.4 and 26.6 ± 2.6 µmol/L at +1Gz and +2Gz, respectively. The dynamics of Hb increase suggests a fast and a slow component. CONCLUSION Despite transmural pressures well beyond the upper myogenic control limit, intact lower body resistance vessels withstand these pressures up to +2Gz, suggesting that myogenic control may contribute only little to increased vascular resistance. The fast component of increasing total Hb indicates microvascular blood pooling contributing to soft tissue capacitance. Future research will have to address possible alterations of these acute adaptations to gravity after deconditioning by exposure to micro-g.
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Affiliation(s)
- H Habazettl
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany. .,German Heart Institute Berlin, Berlin, Germany. .,Center for Space Medicine Berlin, Berlin, Germany.
| | - Alexander Stahn
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany.,Center for Space Medicine Berlin, Berlin, Germany
| | - Andrea Nitsche
- Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany
| | - Michael Nordine
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany.,Center for Space Medicine Berlin, Berlin, Germany
| | - A R Pries
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany.,Center for Cardiovascular Research, Charité-University Medicine Berlin, Berlin, Germany
| | - H-C Gunga
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany.,Center for Space Medicine Berlin, Berlin, Germany
| | - O Opatz
- Institute of Physiology, Charité-University Medicine Berlin, Charitéplatz 1, 10117, Berlin, Germany.,Center for Space Medicine Berlin, Berlin, Germany
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Goswami N, Evans J, Schneider S, von der Wiesche M, Mulder E, Rössler A, Hinghofer-Szalkay H, Blaber AP. Effects of individualized centrifugation training on orthostatic tolerance in men and women. PLoS One 2015; 10:e0125780. [PMID: 26020542 PMCID: PMC4447337 DOI: 10.1371/journal.pone.0125780] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 03/26/2015] [Indexed: 12/03/2022] Open
Abstract
Aims Exposure to artificial gravity (AG) at different G loads and durations on human centrifuges has been shown to improve orthostatic tolerance in men. However, the effects on women and of an individual-specific AG training protocol on tolerance are not known. Methods We examined the effects of 90 minutes of AG vs. 90 minutes of supine rest on the orthostatic tolerance limit (OTL), using head up tilt and lower body negative pressure until presyncope of 7 men and 5 women. Subjects were placed in the centrifuge nacelle while instrumented and after one-hour they underwent either: 1) AG exposure (90 minutes) in supine position [protocol 1, artificial gravity exposure], or 2) lay supine on the centrifuge for 90 minutes in supine position without AG exposure [protocol 2, control]. The AG training protocol was individualized, by first determining each subject’s maximum tolerable G load, and then exposing them to 45 minutes of ramp training at sub-presyncopal levels. Results Both sexes had improved OTL (14 minutes vs 11 minutes, p < 0.0019) following AG exposure. When cardiovascular (CV) variables at presyncope in the control test were compared with the CV variables at the same tilt-test time (isotime) during post-centrifuge, higher blood pressure, stroke volume and cardiac output and similar heart rates and peripheral resistance were found post-centrifuge. Conclusions These data suggest a better-maintained central circulating blood volume post-centrifugation across gender and provide an integrated insight into mechanisms of blood pressure regulation and the possible implementation of in-flight AG countermeasure profiles during spaceflights.
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Affiliation(s)
- Nandu Goswami
- Medical University of Graz, Institute for Physiology, Graz, Austria
- * E-mail:
| | - Joyce Evans
- University of Kentucky, Lexington, United States of America
| | - Stefan Schneider
- German Sports University, Cologne, Germany
- Faculty of Science, Health Education and Engineering, University of Sunshine Coast, Marrochydore, Queensland, Australia
| | | | - Edwin Mulder
- Institute of Aerospace Medicine, German Aerospace Center (DLR), Cologne, Germany
| | - Andreas Rössler
- Medical University of Graz, Institute for Physiology, Graz, Austria
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Mandsager KT, Robertson D, Diedrich A. The function of the autonomic nervous system during spaceflight. Clin Auton Res 2015; 25:141-51. [PMID: 25820827 DOI: 10.1007/s10286-015-0285-y] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Accepted: 01/08/2015] [Indexed: 11/24/2022]
Abstract
INTRODUCTION Despite decades of study, a clear understanding of autonomic nervous system activity in space remains elusive. Differential interpretation of fundamental data has driven divergent theories of sympathetic activation and vasorelaxation. METHODS This paper will review the available in-flight autonomic and hemodynamic data in an effort to resolve these discrepancies. The NASA NEUROLAB mission, the most comprehensive assessment of autonomic function in microgravity to date, will be highlighted. The mechanisms responsible for altered autonomic activity during spaceflight, which include the effects of hypovolemia, cardiovascular deconditioning, and altered central processing, will be presented. RESULTS The NEUROLAB experiments demonstrated increased sympathetic activity and impairment of vagal baroreflex function during short-duration spaceflight. Subsequent non-invasive studies of autonomic function during spaceflight have largely reinforced these findings, and provide strong evidence that sympathetic activity is increased in space relative to the supine position on Earth. Others have suggested that microgravity induces a state of relative vasorelaxation and increased vagal activity when compared to upright posture on Earth. These ostensibly disparate theories are not mutually exclusive, but rather directly reflect different pre-flight postural controls. CONCLUSION When these results are taken together, they demonstrate that the effectual autonomic challenge of spaceflight is small, and represents an orthostatic stress less than that of upright posture on Earth. In-flight countermeasures, including aerobic and resistance exercise, as well short-arm centrifugation, have been successfully deployed to counteract these mechanisms. Despite subtle changes in autonomic activity during spaceflight, underlying neurohumoral mechanisms of the autonomic nervous system remain intact and cardiovascular function remains stable during long-duration flight.
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Affiliation(s)
- Kyle Timothy Mandsager
- Division of Clinical Pharmacology, Department of Medicine, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, 1161 21st Avenue South, Suite AA3228 MCN, Nashville, TN, 37232-2195, USA
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31
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Liu J, Li Y, Verheyden B, Chen S, Chen Z, Gai Y, Liu J, Gao J, Xie Q, Yuan M, Li Q, Li L, Aubert AE. Is autonomic modulation different between European and Chinese astronauts? PLoS One 2015; 10:e0120920. [PMID: 25799561 PMCID: PMC4370477 DOI: 10.1371/journal.pone.0120920] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2014] [Accepted: 02/09/2015] [Indexed: 11/29/2022] Open
Abstract
Purpose The objective was to investigate autonomic control in groups of European and Chinese astronauts and to identify similarities and differences. Methods Beat-to-beat heart rate and finger blood pressure, brachial blood pressure, and respiratory frequency were measured from 10 astronauts (five European taking part in three different space missions and five Chinese astronauts taking part in two different space missions). Data recording was performed in the supine and standing positions at least 10 days before launch, and 1, 3, and 10 days after return. Cross-correlation analysis of heart rate and systolic pressure was used to assess cardiac baroreflex modulation. A fixed breathing protocol was performed to measure respiratory sinus arrhythmia and low-frequency power of systolic blood pressure variability. Results Although baseline cardiovascular parameters before spaceflight were similar in all astronauts in the supine position, a significant increase in sympathetic activity and a decrease in vagal modulation occurred in the European astronauts when standing; spaceflight resulted in a remarkable vagal decrease in European astronauts only. Similar baseline supine and standing values for heart rate, mean arterial pressure, and respiratory frequency were shown in both groups. Standing autonomic control was based on a balance of higher vagal and sympathetic modulation in European astronauts. Conclusion Post-spaceflight orthostatic tachycardia was observed in all European astronauts, whereas post-spaceflight orthostatic tachycardia was significantly reduced in Chinese astronauts. The basis for orthostatic intolerance is not apparent; however, many possibilities can be considered and need to be further investigated, such as genetic diversities between races, astronaut selection, training, and nutrition, etc.
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Affiliation(s)
- Jiexin Liu
- Department of Cardiology, Beijing Friendship Hospital, China Capital Medical University, Beijing, China
- Department of Cardiology, University Hospital Gasthuisberg, K. U. Leuven, Leuven, Belgium
- * E-mail: (JL); (MY)
| | | | - Bart Verheyden
- Department of Cardiology, University Hospital Gasthuisberg, K. U. Leuven, Leuven, Belgium
| | | | | | | | | | | | - Qiong Xie
- China Astronaut Center, Beijing, China
| | - Ming Yuan
- China Astronaut Center, Beijing, China
- * E-mail: (JL); (MY)
| | - Qin Li
- Department of Cardiology, Beijing Friendship Hospital, China Capital Medical University, Beijing, China
| | - Li Li
- Department of Cardiology, Beijing Friendship Hospital, China Capital Medical University, Beijing, China
| | - André E. Aubert
- Department of Cardiology, University Hospital Gasthuisberg, K. U. Leuven, Leuven, Belgium
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32
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Hughson RL, Shoemaker JK. Autonomic responses to exercise: Deconditioning/inactivity. Auton Neurosci 2015; 188:32-5. [DOI: 10.1016/j.autneu.2014.10.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 10/13/2014] [Indexed: 12/29/2022]
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Kang H, Sun L, Huang Y, Wang Z, Zhao P, Fan Y, Deng X. Regional specific adaptation of the endothelial glycocalyx dimension in tail-suspended rats. Pflugers Arch 2014; 467:1291-301. [DOI: 10.1007/s00424-014-1568-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 06/10/2014] [Accepted: 06/26/2014] [Indexed: 10/25/2022]
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Kang H, Fan Y, Sun A, Jia X, Deng X. Simulated microgravity exposure modulates the phenotype of cultured vascular smooth muscle cells. Cell Biochem Biophys 2013; 66:121-30. [PMID: 23097024 DOI: 10.1007/s12013-012-9460-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Evidence from ground-based animal studies using tail-suspended hindlimb unloaded rats model has clearly demonstrated that simulated microgravity-induced smooth muscle cell phenotype conversion, a characteristic vascular structural and functional remodeling, may be one of the key contributors to postspaceflight orthostatic intolerance. However, the rats model involves multiple collective effects of microgravity including cephalic fluid shift and postural muscle unloading on smooth muscle cells (SMCs). It cannot isolate a single factor from the collective ones and therefore is not ideal to study the effects of gravitational vector alteration alone on SMCs. To test the hypothesis that gravitational vector alteration per se might affect smooth muscle cell phenotype, a roller culture apparatus was employed to expose cultured rat aortic smooth muscle cells (RASMCs) to simulated microgravity. Cell proliferation, cell cycle distribution, apoptosis, migration, and nitric oxide production rates were measured and compared between the control and the simulated microgravity groups. Cell cytoskeleton reorganization induced by simulated microgravity was observed by confocal microscopy. Specific contractile and synthetic Gene expression at the mRNA level was quantified by reverse transcriptional polymerase chain reaction. It was observed that simulated microgravity suppressed RASMC proliferation and migration, enhanced cell apoptosis, stimulated NO release, and destroyed the original well-organized cytoskeleton. Moreover, at the mRNA level, long-time exposure (≥ 72 h) to simulated microgravity induced a contractile phenotype tendency by up-regulating smMHC expression. All these findings suggest that the phenotype modulation of vascular smooth muscle cells may be gravity dependent.
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Affiliation(s)
- Hongyan Kang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, 100191, China
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Stenger MB, Lee SMC, Ribeiro LC, Phillips TR, Ploutz-Snyder RJ, Willig MC, Westby CM, Platts SH. Gradient compression garments protect against orthostatic intolerance during recovery from bed rest. Eur J Appl Physiol 2013; 114:597-608. [PMID: 24337701 DOI: 10.1007/s00421-013-2787-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 11/29/2013] [Indexed: 11/28/2022]
Abstract
INTRODUCTION Abdomen-high, lower body graded compression garments (GCGs) may represent the next-generation of orthostatic intolerance protection with applications for exploration missions and commercial space flight. PURPOSE To evaluate the efficacy of the GCG to prevent orthostatic intolerance after a 14-day 6° head-down tilt bed rest (BR) and to determine whether wearing thigh-high compression garments impairs recovery from BR. METHODS Sixteen (12 M, 4 F) subjects participated in a 15-min 80° head-up tilt test 5 day before BR (BR-5), on the last morning of BR (BR+0), and on day 1 (BR+1) and 3 after BR (BR+3). No subjects wore the GCG on BR-5, and all subjects wore the GCG during testing on BR+0. Control subjects (n = 8) wore the GCG only through testing on BR+0. Treatment subjects (n = 8) wore the GCG on BR+0 and thigh-high garments on BR+1 and BR+2. RESULTS No subjects were presyncopal during tilt on BR+0 while wearing the GCG. Despite lower plasma volume index (BR-5: 1.52 ± 0.06, BR+0: 1.32 ± 0.05 l/m(2)), the tilt-induced increase in heart rate (ΔHR, 17 ± 2 bpm) and decrease in stroke volume (ΔSV, -28 ± 3 ml) on BR+0 were less than on BR-5 (24 ± 2 bpm, -43 ± 4 ml). On BR+1 ΔHR in the control group (33 ± 4 bpm) was higher than in the treatment group (23 ± 2 bpm) but there were no group differences on BR+3. CONCLUSIONS Wearing the GCG prevented the orthostatic intolerance that is normally present after BR. Thigh-high garments provided protection after BR, and wearing these garments did not impair recovery.
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Affiliation(s)
- Michael B Stenger
- Wyle Science, Technology and Engineering Group, 1290 Hercules Ave, Houston, TX, 77058, USA,
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36
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Arterial pressure oscillation and muscle sympathetic nerve activity after 20days of head-down bed rest. Auton Neurosci 2013; 177:266-70. [DOI: 10.1016/j.autneu.2013.02.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 01/24/2013] [Accepted: 02/28/2013] [Indexed: 11/27/2022]
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37
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Goswami N, Gorur P, Pilsl U, Anyaehie B, Green DA, Bondarenko AI, Roessler A, Hinghofer-Szalkay HG. Effect of orthostasis on endothelial function: a gender comparative study. PLoS One 2013; 8:e71655. [PMID: 24147147 PMCID: PMC3798144 DOI: 10.1371/journal.pone.0071655] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Accepted: 07/01/2013] [Indexed: 01/22/2023] Open
Abstract
As the vascular endothelium has multiple functions, including regulation of vascular tone, it may play a role in the pathophysiology of orthostatic intolerance. We investigated the effect of orthostasis on endothelial function using EndoPAT®, a non-invasive and user-independent method, and across gender. As sex steroid hormones are known to affect endothelial function, this study examined the potential effect of these hormones on the endothelial response to orthostasis by including females at different phases of the menstrual cycle (follicular and luteal—where the hormone balance differs), and females taking an oral contraceptive. A total of 31 subjects took part in this study (11 males, 11 females having normal menstrual cycles and 9 females taking oral contraceptive). Each subject made two visits for testing; in the case of females having normal menstrual cycles the first session was conducted either 1–7 (follicular) or 14–21 days (luteal) after the start of menstruation, and the second session two weeks later, i.e., during the other phase, respectively. Endothelial function was assessed at baseline and following a 20-min orthostatic challenge (active standing). The EndoPAT® index increased from 1.71 ± 0.09 (mean ± SEM) at baseline to 2.07 ± 0.09 following orthostasis in females (p<0.001). In males, the index increased from 1.60 ± 0.08 to 1.94 ± 0.13 following orthostasis (p<0.001). There were no significant differences, however, in the endothelial response to orthostasis between females and males, menstrual cycle phases and the usage of oral contraceptive. Our results suggest an increased vasodilatatory endothelial response following orthostasis in both females and males. The effect of gender and sex hormones on the endothelial response to orthostasis appears limited. Further studies are needed to determine the potential role of this post orthostasis endothelial response in the pathophysiology of orthostatic intolerance.
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Affiliation(s)
- Nandu Goswami
- Institute of Physiology, Center of Physiological Medicine, Medical University of Graz, Graz, Austria
- * E-mail:
| | - Paavan Gorur
- Centre of Human and Aerospace Physiological Sciences, King’s College London, London, United Kingdom
| | - Ulrike Pilsl
- Department of Anatomy, Medical University of Graz, Graz, Austria
| | - Bond Anyaehie
- Department of Physiology, College of Medicine, University of Nigeria, Enugu Campus, Enugu, Nigeria
| | - David A. Green
- Centre of Human and Aerospace Physiological Sciences, King’s College London, London, United Kingdom
| | | | - Andreas Roessler
- Institute of Physiology, Center of Physiological Medicine, Medical University of Graz, Graz, Austria
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Keith Sharp M, Batzel JJ, Montani JP. Space physiology IV: mathematical modeling of the cardiovascular system in space exploration. Eur J Appl Physiol 2013; 113:1919-37. [PMID: 23539439 DOI: 10.1007/s00421-013-2623-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2012] [Accepted: 03/03/2013] [Indexed: 01/03/2023]
Abstract
Mathematical modeling represents an important tool for analyzing cardiovascular function during spaceflight. This review describes how modeling of the cardiovascular system can contribute to space life science research and illustrates this process via modeling efforts to study postflight orthostatic intolerance (POI), a key issue for spaceflight. Examining this application also provides a context for considering broader applications of modeling techniques to the challenges of bioastronautics. POI, which affects a large fraction of astronauts in stand tests upon return to Earth, presents as dizziness, fainting and other symptoms, which can diminish crew performance and cause safety hazards. POI on the Moon or Mars could be more critical. In the field of bioastronautics, POI has been the dominant application of cardiovascular modeling for more than a decade, and a number of mechanisms for POI have been investigated. Modeling approaches include computational models with a range of incorporated factors and hemodynamic sophistication, and also physical models tested in parabolic and orbital flight. Mathematical methods such as parameter sensitivity analysis can help identify key system mechanisms. In the case of POI, this could lead to more effective countermeasures. Validation is a persistent issue in modeling efforts, and key considerations and needs for experimental data to synergistically improve understanding of cardiovascular responses are outlined. Future directions in cardiovascular modeling include subject-specific assessment of system status, as well as research on integrated physiological responses, leading, for instance, to assessment of subject-specific susceptibility to POI or effects of cardiovascular alterations on muscular, vision and cognitive function.
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Affiliation(s)
- M Keith Sharp
- Biofluid Mechanics Laboratory, Department of Mechanical Engineering, University of Louisville, Louisville, KY, USA
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Goswami N, Batzel JJ, Clément G, Stein TP, Hargens AR, Sharp MK, Blaber AP, Roma PG, Hinghofer-Szalkay HG. Maximizing information from space data resources: a case for expanding integration across research disciplines. Eur J Appl Physiol 2012; 113:1645-54. [PMID: 23073848 DOI: 10.1007/s00421-012-2507-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2012] [Accepted: 09/20/2012] [Indexed: 11/30/2022]
Abstract
Regulatory systems are affected in space by exposure to weightlessness, high-energy radiation or other spaceflight-induced changes. The impact of spaceflight occurs across multiple scales and systems. Exploring such interactions and interdependencies via an integrative approach provides new opportunities for elucidating these complex responses. This paper argues the case for increased emphasis on integration, systematically archiving, and the coordination of past, present and future space and ground-based analogue experiments. We also discuss possible mechanisms for such integration across disciplines and missions. This article then introduces several discipline-specific reviews that show how such integration can be implemented. Areas explored include: adaptation of the central nervous system to space; cerebral autoregulation and weightlessness; modelling of the cardiovascular system in space exploration; human metabolic response to spaceflight; and exercise, artificial gravity, and physiologic countermeasures for spaceflight. In summary, spaceflight physiology research needs a conceptual framework that extends problem solving beyond disciplinary barriers. Administrative commitment and a high degree of cooperation among investigators are needed to further such a process. Well-designed interdisciplinary research can expand opportunities for broad interpretation of results across multiple physiological systems, which may have applications on Earth.
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Affiliation(s)
- Nandu Goswami
- Institute of Physiology, Medical University of Graz, Harrachgasse 21, Graz 8010, Austria.
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Bai Y, Tsunematsu T, Jiao Q, Ohnuki Y, Mototani Y, Shiozawa K, Jin M, Cai W, Jin HL, Fujita T, Ichikawa Y, Suita K, Kurotani R, Yokoyama U, Sato M, Iwatsubo K, Ishikawa Y, Okumura S. Pharmacological stimulation of type 5 adenylyl cyclase stabilizes heart rate under both microgravity and hypergravity induced by parabolic flight. J Pharmacol Sci 2012; 119:381-9. [PMID: 22850613 DOI: 10.1254/jphs.12102fp] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
We previously demonstrated that type 5 adenylyl cyclase (AC5) functions in autonomic regulation in the heart. Based on that work, we hypothesized that pharmacological modulation of AC5 activity could regulate the autonomic control of the heart rate under micro- and hypergravity. To test this hypothesis, we selected the approach of activating AC5 activity in mice with a selective AC5 activator (NKH477) or inhibitor (vidarabine) and examining heart rate variability during parabolic flight. The standard deviation of normal R-R intervals, a marker of total autonomic variability, was significantly greater under micro- and hypergravity in the vidarabine group, while there were no significant changes in the NKH477 group, suggesting that autonomic regulation was unstable in the vidarabine group. The ratio of low frequency and high frequency (HF) in heart rate variability analysis, a marker of sympathetic activity, became significantly decreased under micro- and hypergravity in the NKH477 group, while there was no such decrease in the vidarabine group. Normalized HF, a marker of parasympathetic activity, became significantly greater under micro- and hypergravity in the NKH477 group. In contrast, there was no such increase in the vidarabine group. This study is the first to indicate that pharmacological modulation of AC5 activity under micro- and hypergravity could be useful to regulate the autonomic control of the heart rate.
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Affiliation(s)
- Yunzhe Bai
- Cardiovascular Research Institute, Yokohama City University Graduate School of Medicine, Japan
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Autonomic mechanisms associated with heart rate and vasoconstrictor reserves. Clin Auton Res 2011; 22:123-30. [DOI: 10.1007/s10286-011-0151-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 10/10/2011] [Indexed: 01/03/2023]
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Jeong SM, Shibata S, Levine BD, Zhang R. Exercise plus volume loading prevents orthostatic intolerance but not reduction in cerebral blood flow velocity after bed rest. Am J Physiol Heart Circ Physiol 2011; 302:H489-97. [PMID: 22081705 DOI: 10.1152/ajpheart.00427.2011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study tested the hypothesis that reduction in cerebral blood flow (CBF) during orthostatic stress after bed rest can be ameliorated with volume loading, exercise, or both. Transcranial Doppler was used to measure changes in CBF velocity during lower body negative pressure (LBNP) before and after an 18-day bed rest in 33 healthy subjects. Subjects were assigned into four groups with similar age and sex: 1) supine cycling during bed rest (Exercise group; n = 7), 2) volume loading with Dextran infusion after bed rest to restore reduced left ventricular filling pressure (Dextran group; n = 7), 3) exercise combined with volume loading to prevent orthostatic intolerance (Ex-Dex group; n = 7), and 4) a control group (n = 12). LBNP tolerance was measured using a cumulative stress index (CSI). After bed rest, CBF velocity was reduced at a lower level of LBNP in the Control group, and the magnitude of reduction was greater in the Ex-Dex group. However, reduction in orthostatic tolerance was prevented in the Ex-Dex group. Notably, volume loading alone prevented greater reductions in CBF velocity after bed rest, but CSI was reduced still by 25%. Finally, decreases in CBF velocity during LBNP were correlated with reduction in cardiac output under all conditions (r(2) = 0.86; P = < 0.001). Taken together, these findings demonstrate that volume loading alone can ameliorate reductions in CBF during LBNP. However, the lack of associations between changes in CBF velocity and orthostatic tolerance suggests that reductions in CBF during LBNP under steady-state conditions by itself are unlikely to be a primary factor leading to orthostatic intolerance.
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Affiliation(s)
- Sung-Moon Jeong
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, and University of Texas Southwestern Medical Center at Dallas, TX 75231, USA
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Spironelli C, Angrilli A. Influence of body position on cortical pain-related somatosensory processing: an ERP study. PLoS One 2011; 6:e24932. [PMID: 21949794 PMCID: PMC3174221 DOI: 10.1371/journal.pone.0024932] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2011] [Accepted: 08/24/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Despite the consistent information available on the physiological changes induced by head down bed rest, a condition which simulates space microgravity, our knowledge on the possible perceptual-cortical alterations is still poor. The present study investigated the effects of 2-h head-down bed rest on subjective and cortical responses elicited by electrical, pain-related somatosensory stimulation. METHODOLOGY/PRINCIPAL FINDINGS Twenty male subjects were randomly assigned to two groups, head-down bed rest (BR) or sitting control condition. Starting from individual electrical thresholds, Somatosensory Evoked Potentials were elicited by electrical stimuli administered randomly to the left wrist and divided into four conditions: control painless condition, electrical pain threshold, 30% above pain threshold, 30% below pain threshold. Subjective pain ratings collected during the EEG session showed significantly reduced pain perception in BR compared to Control group. Statistical analysis on four electrode clusters and sLORETA source analysis revealed, in sitting controls, a P1 component (40-50 ms) in the right somatosensory cortex, whereas it was bilateral and differently located in BR group. Controls' N1 (80-90 ms) had widespread right hemisphere activation, involving also anterior cingulate, whereas BR group showed primary somatosensory cortex activation. The P2 (190-220 ms) was larger in left-central locations of Controls compared with BR group. CONCLUSIONS/SIGNIFICANCE Head-down bed rest was associated to an overall decrease of pain sensitivity and an altered pain network also outside the primary somatosensory cortex. Results have implications not only for astronauts' health and spaceflight risks, but also for the clinical aspects of pain detection in bedridden patients at risk of fatal undetected complications.
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Affiliation(s)
- Chiara Spironelli
- Department of General Psychology, University of Padova, Padova, Italy
| | - Alessandro Angrilli
- Department of General Psychology, University of Padova, Padova, Italy
- CNR Institute of Neuroscience, Padova, Italy
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Aoki K, Ogawa Y, Iwasaki KI, Mukai C. [Approach to elucidating the influences and factors affecting circulation system in humans in space environment]. Nihon Eiseigaku Zasshi 2011; 66:568-72. [PMID: 21701089 DOI: 10.1265/jjh.66.568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many physiological changes associated with spaceflight, including decreases in orthostatic tolerance, exercise capacity, and blood volume have been reported. Orthostatic intolerance is a problem affecting many astronauts immediately postspaceflight. In particular, the relationship between orthostatic intolerance and cerebral autoregulation has been the focus of study in our research group. Although impairment of cerebral autoregulation was speculated to be one of the factors resulting in reduced post flight orthostatic tolerance, a 2-wk spaceflight study revealed that human cerebral autoregulation is preserved or even improved during and immediately after spaceflight in nonsymptomatic astronauts. To investigate the influences of the different kinds of reduction in central blood volume, we performed two ground-based studies. It is suggested that the mild intravascular dehydration partly explains the improved dynamic cerebral autoregulation observed during and immediately after a short-term spaceflight. Moreover, we also studied the relationship between orthostatic intolerance and cerebral autoregulation under hyperthermic conditions, because hyperthermia leads to orthostatic intolerance. Furthermore, we planned to conduct a study at the International Space Station (ISS) and ground-based studies to elucidate the influences and factors affecting the circulation system in humans in a space environment.
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Affiliation(s)
- Ken Aoki
- Division of Hygiene, Department of Social Medicine, Nihon University School of Medicine, Itabashi-ku, Tokyo, Japan
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Artificial gravity training reduces bed rest-induced cardiovascular deconditioning. Eur J Appl Physiol 2011; 112:605-16. [PMID: 21626041 DOI: 10.1007/s00421-011-2005-1] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Accepted: 05/10/2011] [Indexed: 10/18/2022]
Abstract
We studied 15 men (8 treatment, 7 control) before and after 21 days of 6º head-down tilt to determine whether daily, 1-h exposures to 1.0 G(z) (at the heart) artificial gravity (AG) would prevent bed rest-induced cardiovascular deconditioning. Testing included echocardiographic analysis of cardiac function, plasma volume (PV), aerobic power (VO(2)pk) and cardiovascular and neuroendocrine responses to 80º head-up tilt (HUT). Data collected during HUT were ECG, stroke volume (SV), blood pressure (BP) and blood for catecholamines and vasoactive hormones. Heart rate (HR), cardiac output (CO), total peripheral resistance, and spectral power of BP and HR were calculated. Bed rest decreased PV, supine and HUT SV, and indices of cardiac function in both groups. Although PV was decreased in control and AG after bed rest, AG attenuated the decrease in orthostatic tolerance [pre- to post-bed rest change; control: -11.8 ± 2.0, AG: -6.0 ± 2.8 min (p = 0.012)] and VO(2)pk [pre- to post-bed rest change; control: -0.39 ± 0.11, AG: -0.17 ± 0.06 L/min (p = 0.041)]. AG prevented increases in pre-tilt levels of plasma renin activity [pre- to post-bed rest change; control: 1.53 ± 0.23, AG: -0.07 ± 0.34 ng/mL/h (p = 0.001)] and angiotensin II [pre- to post-bed rest change; control: 3.00 ± 1.04, AG: -0.63 ± 0.81 pg/mL (p = 0.009)] and increased HUT aldosterone [post-bed rest; control: 107 ± 30 pg/mL, AG: 229 ± 68 pg/mL (p = 0.045)] and norepinephrine [post-bed rest; control: 453 ± 107, AG: 732 ± 131 pg/mL (p = 0.003)]. We conclude that AG can mitigate some aspects of bed rest-induced cardiovascular deconditioning, including orthostatic intolerance and aerobic power. Mechanisms of improvement were not cardiac-mediated, but likely through improved sympathetic responsiveness to orthostatic stress.
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Blaber AP, Goswami N, Bondar RL, Kassam MS. Impairment of cerebral blood flow regulation in astronauts with orthostatic intolerance after flight. Stroke 2011; 42:1844-50. [PMID: 21617145 DOI: 10.1161/strokeaha.110.610576] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE We investigated cerebral blood flow regulation in astronauts before and after flights. We hypothesized that autoregulation would be different before flight and after flight between nonfinishers and the finishers of a stand test. METHODS Twenty-seven astronauts from shuttle missions lasting 8 to 16 days underwent a 10-minute stand test: 10 days before flight, 1 to 2 hours and 3 days after landing. Mean blood flow velocity of the middle cerebral artery (MCA) was measured using transcranial Doppler; Mean arterial pressure was measured using a Finapres (Ohmeda, Englewood, CO) and was adjusted to the level of the MCA (BP(MCA)). Cross-spectral power, gain, phase, and coherence were determined for the relation between BP(MCA) and the cerebrovascular resistance index mean blood flow velocity/BP(MCA). RESULTS BP(MCA) was reduced with stand (P<0.001). Differences between finishers and nonfinishers (P=0.011) and over test days (P=0.004) were observed. Cerebrovascular conductance was affected by stand (P<0.001), by group (P<0.001) with a group by stand, and test day interaction (P<0.01). Preflight data suggest that the nonfinishers were operating at a higher cerebral vasodilation than finishers for a given BP(MCA), and on landing day the nonfinishers had a greater decrease in mean blood flow velocity as a function of BP(MCA) with standing compared to finishers and preflight. There was a significant interaction effect of gender over the test days and from supine to stand (P=0.035). CONCLUSIONS Our results indicate that the cause of presyncope in astronauts may be related to a mismatch of cerebral blood flow with blood pressure. Astronaut gender may also play a role in susceptibility to orthostatic intolerance after flight.
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Affiliation(s)
- Andrew P Blaber
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6.
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Deegan BM, Sorond FA, Galica A, Lipsitz LA, O'Laighin G, Serrador JM. Elderly women regulate brain blood flow better than men do. Stroke 2011; 42:1988-93. [PMID: 21566238 DOI: 10.1161/strokeaha.110.605618] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Orthostatic intolerance and falls differ between sexes and change with age. However, it remains unclear what role cerebral autoregulation may play in this response. This study was designed to determine whether cerebral autoregulation, assessed using transcranial Doppler ultrasound, is more effective in elderly females than in males. METHODS We used transcranial Doppler ultrasound to evaluate cerebral autoregulation in 544 (236 male) subjects older than age 70 years recruited as part of the MOBILIZE Boston study. The MOBILIZE Boston study is a prospective cohort study of a unique set of risk factors for falls in seniors in the Boston area. We assessed CO2 reactivity and transfer function gain, phase, and coherence during 5 minutes of quiet sitting and autoregulatory index during sit-to-stand tests. RESULTS Male subjects had significantly lower CO2 reactivity (males, 1.10 ± 0.03; females, 1.32 ± 0.43 (cm/s)/%CO2; P<0.001) and autoregulatory indices (males, 4.41 ± 2.44; female, 5.32 ± 2.47; P<0.001), higher transfer function gain (males, 1.34 ± 0.49; females, 1.19 ± 0.43; P=0.002), and lower phase (males, 42.7 ± 23.6; females, 49.4 ± 24.9; P=0.002) in the autoregulatory band, implying less effective cerebral autoregulation. However, reduced autoregulation in males was not below the normal range, indicating autoregulation was intact but less effective. CONCLUSIONS Female subjects were better able to maintain cerebral flow velocities during postural changes and demonstrated better cerebral autoregulation. The mechanisms of sex-based differences in autoregulation remain unclear but may partially explain the higher rates of orthostatic hypotension-related hospitalizations in elderly men.
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Affiliation(s)
- Brian M Deegan
- Electrical & Electronic Engineering, School of Engineering & Informatics, NUI Galway, University Road, Galway, Ireland
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Fujii Y, Ishizaki Y, Kino M, Taniuchi S, Kobayashi Y, Kaneko K. Two types of orthostatic dysregulation assessed by diameter of inferior vena cava. Pediatr Int 2011; 53:162-7. [PMID: 20723105 DOI: 10.1111/j.1442-200x.2010.03228.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIMS Orthostatic dysregulation (OD) is common in adolescents. This study was conducted to evaluate the usefulness of the measurement of the diameter of the inferior vena cava (IVC) for objective assessment of patients with OD. METHODS Twenty children with OD (median 14 years, range 9-15 years) and 23 age-matched healthy children (median 12 years, range 10-15 years) were enrolled. A diameter of IVC was measured by an abdominal echogram before and after a head-up tilt table testing (HUT). Changes in IVC was assessed by an arbitrary parameter, collapse index (CI) as the following equation: [(maximal IVC diameter in the supine position - maximal IVC diameter in the standing position)/(maximal IVC diameter in the supine position)]× 100. CI was evaluated 4 weeks after treatment with an adrenergic agent. RESULTS Children with OD demonstrated either higher CI or lower CI compared to that in control children: CI was more than 50 (range 50-71) in 12 patients with OD while that was equal to or less than 0 (range -225 to 0) in eight out of 20 patients. In contrast, CI was between 0 and 50 (range 1-26) in 23 healthy children. Pharmacological treatment induced the normalization in the CI in both higher and lower CI group. CONCLUSION OD can be classified into two subtypes: by HUT, one is characterized by an increase of IVC diameter while another is characterized by its decrease. Measurement of IVC diameter by HUT is useful to understand the pathophysiology and to assess the efficacy of treatment.
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Affiliation(s)
- Yuri Fujii
- Department of Pediatrics, Kansai Medical University Nakano Children's Hospital Osaka University of Comprehensive Children Education, Osaka, Japan
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Dyckman DJ, Sauder CL, Ray CA. Glycerol-induced fluid shifts attenuate the vestibulosympathetic reflex in humans. Am J Physiol Regul Integr Comp Physiol 2010; 300:R630-4. [PMID: 21178123 DOI: 10.1152/ajpregu.00767.2010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The glycerol dehydration test (GDT) has been used to test for the presence of Ménière's disease and elicits acute alterations in vestibular reflexes in both normal and pathological states. Activation of the vestibulosympathetic reflex (VSR) increases muscle sympathetic nerve activity (MSNA) and peripheral vascular resistance. We hypothesized that the GDT would attenuate the VSR through fluid shifts of the inner ear. Sixteen male subjects (26 ± 1 yr) were randomly assigned to be administered either glycerol mixed with cranberry juice (97 ± 3 ml glycerol + equal portion of cranberry juice; n = 9) or a placebo control [water + cranberry juice (100 ml each); n = 7]. Subjects in both groups performed head-down rotation (HDR), which engages the VSR, before and after administration of either the glycerol or placebo. MSNA (microneurography), arterial blood pressure, and leg blood flow (venous occlusion plethysmography) were measured during HDR. Before glycerol administration, HDR significantly increased MSNA burst frequency (Δ8 ± 1 bursts/min; P < 0.01) and total activity (Δ77 ± 18%; P < 0.01) and decreased calf vascular conductance (-Δ20 ± 3%; P < 0.01). However, HDR performed postadministration of glycerol resulted in an attenuated MSNA increase (Δ3 ± 1 bursts/min, Δ22 ± 3% total activity) and decrease in calf vascular conductance (-Δ7 ± 4%). HDR significantly increased MSNA burst frequency (Δ5 ± 1 and Δ5 ± 2 bursts/min) and total activity (Δ58 ± 13% and Δ52 ± 18%) in the placebo group before and after placebo, respectively (P < 0.01). Likewise, decreases in calf vascular conductance during HDR before and after placebo were not different (-Δ13 ± 4% and -Δ14 ± 2%, respectively; P < 0.01). These results suggest that fluid shifts of the inner ear via glycerol dehydration attenuate the VSR. These data provide support that inner ear fluid dynamics can have a significant impact on blood pressure regulation via the VSR in humans.
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Affiliation(s)
- Damian J Dyckman
- Penn State Heart and Vascular Institute, Department of Cellular and Molecular Physiology, General Clinical Research Center, Pennsylvania State University College of Medicine, Hershey, USA
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Fu Q, Vangundy TB, Galbreath MM, Shibata S, Jain M, Hastings JL, Bhella PS, Levine BD. Cardiac origins of the postural orthostatic tachycardia syndrome. J Am Coll Cardiol 2010; 55:2858-68. [PMID: 20579544 DOI: 10.1016/j.jacc.2010.02.043] [Citation(s) in RCA: 201] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Revised: 01/06/2010] [Accepted: 02/01/2010] [Indexed: 11/29/2022]
Abstract
OBJECTIVES The purpose of this study was to test the hypothesis that a small heart coupled with reduced blood volume contributes to the postural orthostatic tachycardia syndrome (POTS) and that exercise training improves this syndrome. BACKGROUND Patients with POTS have marked increases in heart rate during orthostasis. However, the underlying mechanisms are unknown and the effective therapy is uncertain. METHODS Twenty-seven POTS patients underwent autonomic function tests, cardiac magnetic resonance imaging, and blood volume measurements. Twenty-five of them participated in a 3-month specially designed exercise training program with 19 completing the program; these patients were re-evaluated after training. Results were compared with those of 16 healthy controls. RESULTS Upright heart rate and total peripheral resistance were greater, whereas stroke volume and cardiac output were smaller in patients than in controls. Baroreflex function was similar between groups. Left ventricular mass (median [25th, 75th percentiles], 1.26 g/kg [1.12, 1.37 g/kg] vs. 1.45 g/kg [1.34, 1.57 g/kg]; p < 0.01) and blood volume (60 ml/kg [54, 64 ml/kg] vs. 71 ml/kg [65, 78 ml/kg]; p < 0.01) were smaller in patients than in controls. Exercise training increased left ventricular mass and blood volume by approximately 12% and approximately 7% and decreased upright heart rate by 9 beats/min [1, 17 beats/min]. Ten of 19 patients no longer met POTS criteria after training, whereas patient quality of life assessed by the 36-item Short-Form Health Survey was improved in all patients after training. CONCLUSIONS Autonomic function was intact in POTS patients. The marked tachycardia during orthostasis was attributable to a small heart coupled with reduced blood volume. Exercise training improved or even cured this syndrome in most patients. It seems reasonable to offer POTS a new name based on its underlying pathophysiology, the "Grinch syndrome," because in this famous children's book by Dr. Seuss, the main character had a heart that was "two sizes too small."
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Affiliation(s)
- Qi Fu
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, Texas 75231, USA
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