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Hall EA, Whittle RS, Diaz-Artiles A. Ocular perfusion pressure is not reduced in response to lower body negative pressure. NPJ Microgravity 2024; 10:67. [PMID: 38851800 PMCID: PMC11162494 DOI: 10.1038/s41526-024-00404-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Accepted: 05/16/2024] [Indexed: 06/10/2024] Open
Abstract
Lower body negative pressure (LBNP) has been proposed as a countermeasure to mitigate the cephalad fluid shift occurring during spaceflight, which may be associated with the development of Spaceflight Associated Neuro-ocular Syndrome (SANS). This study quantifies the effect of LBNP on intraocular pressure (IOP), mean arterial pressure at eye level (MAPeye), and ocular perfusion pressure (OPP). Twenty-four subjects (12 male, 12 female) were subjected to graded LBNP in 0° supine and 15° head-down tilt (HDT) postures from 0 mmHg to -50 mmHg in 10 mmHg increments. IOP decreased significantly with LBNP pressure in 0° supine (by 0.7 ± 0.09 mmHg per 10 mmHg LBNP pressure, p < 0.001) and in 15° HDT (by 1.0 ± 0.095 mmHg per 10 mmHg of LBNP pressure, p < 0.001). MAPeye significantly decreased by 0.9 ± 0.4 mmHg per 10 mmHg of LBNP pressure in 0° supine (p = 0.016) but did not significantly change with LBNP in 15° HDT (p = 0.895). OPP did not significantly change with LBNP in 0° supine (p = 0.539) but it significantly increased in 15° HDT at 1.0 ± 0.3 mmHg per 10 mmHg of LBNP pressure (p = 0.010). Sex did not have a significant effect on OPP, MAPeye, or IOP in any condition. In 15° HDT, the reduction in IOP during increasing negative pressure, combined with the relatively constant MAPeye, led to the increase in OPP. Furthermore, results suggest that LBNP, while effective in reducing IOP, is not effective in reducing OPP across all postures investigated.
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Affiliation(s)
- Eric A Hall
- Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA
- School of Engineering Medicine (EnMed), Texas A&M University, Houston, TX, USA
| | - Richard S Whittle
- Department of Mechanical and Aerospace Engineering, University of California Davis, Davis, CA, USA
- Department of Aerospace Engineering, Texas A&M University, College Station, TX, USA
| | - Ana Diaz-Artiles
- Department of Aerospace Engineering, Texas A&M University, College Station, TX, USA.
- Department of Kinesiology and Sport Management, Texas A&M University, College Station, TX, USA.
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2
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Munster DW, Lewandowski BE, Nelson ES, Prabhu RK, Myers JG. Modeling the impact of thoracic pressure on intracranial pressure. NPJ Microgravity 2024; 10:46. [PMID: 38600142 PMCID: PMC11006658 DOI: 10.1038/s41526-024-00385-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 03/13/2024] [Indexed: 04/12/2024] Open
Abstract
A potential contribution to the progression of Spaceflight Associated Neuro-ocular Syndrome is the thoracic-to-spinal dural sac transmural pressure relationship. In this study, we utilize a lumped-parameter computational model of human cerebrospinal fluid (CSF) systems to investigate mechanisms of CSF redistribution. We present two analyses to illustrate potential mechanisms for CSF pressure alterations similar to those observed in microgravity conditions. Our numerical evidence suggests that the compliant relationship between thoracic and CSF compartments is insufficient to solely explain the observed decrease in CSF pressure with respect to the supine position. Our analyses suggest that the interaction between thoracic pressure and the cardiovascular system, particularly the central veins, has greater influence on CSF pressure. These results indicate that future studies should focus on the holistic system, with the impact of cardiovascular changes to the CSF pressure emphasized over the sequestration of fluid in the spine.
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Affiliation(s)
- Drayton W Munster
- NASA Glenn Research Center, 21000 Brookpark Road, Cleveland, OH, 44135, USA.
| | - Beth E Lewandowski
- NASA Glenn Research Center, 21000 Brookpark Road, Cleveland, OH, 44135, USA
| | - Emily S Nelson
- NASA Glenn Research Center, 21000 Brookpark Road, Cleveland, OH, 44135, USA
| | - R K Prabhu
- Universities Space Research Association, 21000 Brookpark Road, Cleveland, OH, 44135, USA
| | - Jerry G Myers
- NASA Glenn Research Center, 21000 Brookpark Road, Cleveland, OH, 44135, USA
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3
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Richmond SB, Seidler RD, Iliff JJ, Schwartz DL, Luther M, Silbert LC, Wood SJ, Bloomberg JJ, Mulder E, Lee JK, De Luca A, Piantino J. Dynamic changes in perivascular space morphology predict signs of spaceflight-associated neuro-ocular syndrome in bed rest. NPJ Microgravity 2024; 10:24. [PMID: 38429289 PMCID: PMC10907584 DOI: 10.1038/s41526-024-00368-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 02/15/2024] [Indexed: 03/03/2024] Open
Abstract
During long-duration spaceflight, astronauts experience headward fluid shifts and expansion of the cerebral perivascular spaces (PVS). A major limitation to our understanding of the changes in brain structure and physiology induced by spaceflight stems from the logistical difficulties of studying astronauts. The current study aimed to determine whether PVS changes also occur on Earth with the spaceflight analog head-down tilt bed rest (HDBR). We examined how the number and morphology of magnetic resonance imaging-visible PVS (MV-PVS) are affected by HDBR with and without elevated carbon dioxide (CO2). These environments mimic the headward fluid shifts, body unloading, and elevated CO2 observed aboard the International Space Station. Additionally, we sought to understand how changes in MV-PVS are associated with signs of Spaceflight Associated Neuro-ocular Syndrome (SANS), ocular structural alterations that can occur with spaceflight. Participants were separated into two bed rest campaigns: HDBR (60 days) and HDBR + CO2 (30 days with elevated ambient CO2). Both groups completed multiple magnetic resonance image acquisitions before, during, and post-bed rest. We found that at the group level, neither spaceflight analog affected MV-PVS quantity or morphology. However, when taking into account SANS status, persons exhibiting signs of SANS showed little or no MV-PVS changes, whereas their No-SANS counterparts showed MV-PVS morphological changes during the HDBR + CO2 campaign. These findings highlight spaceflight analogs as models for inducing changes in MV-PVS and implicate MV-PVS dynamic compliance as a mechanism underlying SANS. These findings may lead to countermeasures to mitigate health risks associated with human spaceflight.
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Affiliation(s)
- Sutton B Richmond
- Department of Applied Physiology and Kinesiology, University of Florida, 1864, Stadium Rd., Gainesville, FL, USA
| | - Rachael D Seidler
- Department of Applied Physiology and Kinesiology, University of Florida, 1864, Stadium Rd., Gainesville, FL, USA
- Norman Fixel Institute for Neurological Diseases, University of Florida, Gainesville, FL, USA
| | - Jeffrey J Iliff
- Department of Psychiatry and Behavioral Sciences, University of Washington School of Medicine, Seattle, WA, USA
- Department of Neurology, University of Washington School of Medicine, Seattle, WA, USA
- VISN 20 Mental Illness Research, Education and Clinical Center (MIRECC), VA Puget Sound Health Care System, Seattle, WA, USA
| | - Daniel L Schwartz
- Layton-NIA Oregon Aging and Alzheimer's Disease Research Center, Department of Neurology, Oregon Health & Science University, Portland, OR, USA
- Advanced Imaging Research Center, Oregon Health & Science University, Portland, OR, USA
| | - Madison Luther
- Department of Pediatrics, Division of Child Neurology, Doernbecher Children's Hospital, Oregon Health and Science University, Portland, OR, USA
| | - Lisa C Silbert
- Layton-NIA Oregon Aging and Alzheimer's Disease Research Center, Department of Neurology, Oregon Health & Science University, Portland, OR, USA
- Veteran's Affairs Portland Health Care System, Neurology, Portland, OR, USA
| | | | | | | | - Jessica K Lee
- Department of Applied Physiology and Kinesiology, University of Florida, 1864, Stadium Rd., Gainesville, FL, USA
- German Aerospace Center (DLR), Cologne, Germany
| | - Alberto De Luca
- Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands
| | - Juan Piantino
- Department of Pediatrics, Division of Child Neurology, Doernbecher Children's Hospital, Oregon Health and Science University, Portland, OR, USA.
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4
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Fois M, Diaz-Artiles A, Zaman SY, Ridolfi L, Scarsoglio S. Linking cerebral hemodynamics and ocular microgravity-induced alterations through an in silico-in vivo head-down tilt framework. NPJ Microgravity 2024; 10:22. [PMID: 38413627 PMCID: PMC10899661 DOI: 10.1038/s41526-024-00366-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Accepted: 02/15/2024] [Indexed: 02/29/2024] Open
Abstract
Head-down tilt (HDT) has been widely proposed as a terrestrial analog of microgravity and used also to investigate the occurrence of spaceflight-associated neuro-ocular syndrome (SANS), which is currently considered one of the major health risks for human spaceflight. We propose here an in vivo validated numerical framework to simulate the acute ocular-cerebrovascular response to 6° HDT, to explore the etiology and pathophysiology of SANS. The model links cerebral and ocular posture-induced hemodynamics, simulating the response of the main cerebrovascular mechanisms, as well as the relationship between intracranial and intraocular pressure to HDT. Our results from short-term (10 min) 6° HDT show increased hemodynamic pulsatility in the proximal-to-distal/capillary-venous cerebral direction, a marked decrease (-43%) in ocular translaminar pressure, and an increase (+31%) in ocular perfusion pressure, suggesting a plausible explanation of the underlying mechanisms at the onset of ocular globe deformation and edema formation over longer time scales.
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Affiliation(s)
- Matteo Fois
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, Turin, 10129, Italy.
| | - Ana Diaz-Artiles
- Department of Aerospace Engineering, Texas A&M University, 3141 TAMU, College Station, TX, 77843-3141, USA
- Department of Kinesiology and Sport Management, Texas A&M University, 2929 Research Pkwy, College Station, TX, 77845, USA
| | - Syeda Yasmin Zaman
- Department of Aerospace Engineering, Texas A&M University, 3141 TAMU, College Station, TX, 77843-3141, USA
| | - Luca Ridolfi
- Department of Environmental, Land and Infrastructure Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, Turin, 10129, Italy
- PolitoBioMed Lab, Politecnico di Torino, Corso Duca degli Abruzzi 24, Turin, 10129, Italy
| | - Stefania Scarsoglio
- Department of Mechanical and Aerospace Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, Turin, 10129, Italy
- PolitoBioMed Lab, Politecnico di Torino, Corso Duca degli Abruzzi 24, Turin, 10129, Italy
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5
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Milner DC, Subramanian PS. Insights into spaceflight-associated neuro-ocular syndrome with review of intraocular and orbital findings. Curr Opin Ophthalmol 2023; 34:493-499. [PMID: 37729662 DOI: 10.1097/icu.0000000000001000] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
PURPOSE OF REVIEW Spaceflight-associated neuro-ocular syndrome (SANS) remains a phenomenological term, and advances in ophthalmic imaging as well as new insights from ground-based experiments have given support to new theories of how SANS develops and what may be done to counter it. RECENT FINDINGS SANS has been postulated to arise from elevated intracranial pressure (ICP) during long-duration spaceflight (LDSF). However, recent work has shown that acute microgravity exposure does not increase ICP, and the effect of cephalad fluid shifts on ICP in microgravity remain unknown. In addition, structural imaging of the retina and optic nerve show changes after LDSF that are distinct from findings in terrestrial patients with elevated ICP. Since astronauts have not reported symptoms that would be expected with chronic ICP elevation, new theories that orbital and/or intracranial venous pressure may be the primary contributors to the development of SANS. SUMMARY Research has been filling knowledge gaps that exist regarding the cause(s) of SANS, and these advances are crucial steps in the effort to design countermeasures that will be required before human deep space exploration missions can be undertaken.
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Affiliation(s)
- Dallin C Milner
- Sue Anschutz-Rodgers University of Colorado Eye Center and Department of Ophthalmology
| | - Prem S Subramanian
- Sue Anschutz-Rodgers University of Colorado Eye Center and Department of Ophthalmology
- Department of Neurology
- Department of Neurosurgery, University of Colorado School of Medicine, Aurora, Colorado
- Department of Surgery (Division of Ophthalmology), Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
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6
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Ong J, Waisberg E, Masalkhi M, Kamran SA, Lowry K, Sarker P, Zaman N, Paladugu P, Tavakkoli A, Lee AG. Artificial Intelligence Frameworks to Detect and Investigate the Pathophysiology of Spaceflight Associated Neuro-Ocular Syndrome (SANS). Brain Sci 2023; 13:1148. [PMID: 37626504 PMCID: PMC10452366 DOI: 10.3390/brainsci13081148] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 07/24/2023] [Accepted: 07/28/2023] [Indexed: 08/27/2023] Open
Abstract
Spaceflight associated neuro-ocular syndrome (SANS) is a unique phenomenon that has been observed in astronauts who have undergone long-duration spaceflight (LDSF). The syndrome is characterized by distinct imaging and clinical findings including optic disc edema, hyperopic refractive shift, posterior globe flattening, and choroidal folds. SANS serves a large barrier to planetary spaceflight such as a mission to Mars and has been noted by the National Aeronautics and Space Administration (NASA) as a high risk based on its likelihood to occur and its severity to human health and mission performance. While it is a large barrier to future spaceflight, the underlying etiology of SANS is not well understood. Current ophthalmic imaging onboard the International Space Station (ISS) has provided further insights into SANS. However, the spaceflight environment presents with unique challenges and limitations to further understand this microgravity-induced phenomenon. The advent of artificial intelligence (AI) has revolutionized the field of imaging in ophthalmology, particularly in detection and monitoring. In this manuscript, we describe the current hypothesized pathophysiology of SANS and the medical diagnostic limitations during spaceflight to further understand its pathogenesis. We then introduce and describe various AI frameworks that can be applied to ophthalmic imaging onboard the ISS to further understand SANS including supervised/unsupervised learning, generative adversarial networks, and transfer learning. We conclude by describing current research in this area to further understand SANS with the goal of enabling deeper insights into SANS and safer spaceflight for future missions.
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Affiliation(s)
- Joshua Ong
- Department of Ophthalmology and Visual Sciences, University of Michigan Kellogg Eye Center, Ann Arbor, MI 48105, USA
| | | | - Mouayad Masalkhi
- University College Dublin School of Medicine, Belfield, Dublin 4, Ireland
| | - Sharif Amit Kamran
- Human-Machine Perception Laboratory, Department of Computer Science and Engineering, University of Nevada, Reno, NV 89512, USA
| | | | - Prithul Sarker
- Human-Machine Perception Laboratory, Department of Computer Science and Engineering, University of Nevada, Reno, NV 89512, USA
| | - Nasif Zaman
- Human-Machine Perception Laboratory, Department of Computer Science and Engineering, University of Nevada, Reno, NV 89512, USA
| | - Phani Paladugu
- Brigham and Women’s Hospital, Harvard Medical School, Boston, MA 02115, USA
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Alireza Tavakkoli
- Human-Machine Perception Laboratory, Department of Computer Science and Engineering, University of Nevada, Reno, NV 89512, USA
| | - Andrew G. Lee
- Center for Space Medicine, Baylor College of Medicine, Houston, TX 77030, USA
- Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX 77030, USA
- The Houston Methodist Research Institute, Houston Methodist Hospital, Houston, TX 77030, USA
- Departments of Ophthalmology, Neurology, and Neurosurgery, Weill Cornell Medicine, New York, NY 10065, USA
- Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX 77555, USA
- University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- Texas A&M College of Medicine, Bryan, TX 77030, USA
- Department of Ophthalmology, The University of Iowa Hospitals and Clinics, Iowa City, IA 50010, USA
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7
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Homo sapiens—A Species Not Designed for Space Flight: Health Risks in Low Earth Orbit and Beyond, Including Potential Risks When Traveling beyond the Geomagnetic Field of Earth. Life (Basel) 2023; 13:life13030757. [PMID: 36983912 PMCID: PMC10051707 DOI: 10.3390/life13030757] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Revised: 03/03/2023] [Accepted: 03/08/2023] [Indexed: 03/18/2023] Open
Abstract
Homo sapiens and their predecessors evolved in the context of the boundary conditions of Earth, including a 1 g gravity and a geomagnetic field (GMF). These variables, plus others, led to complex organisms that evolved under a defined set of conditions and define how humans will respond to space flight, a circumstance that could not have been anticipated by evolution. Over the past ~60 years, space flight and living in low Earth orbit (LEO) have revealed that astronauts are impacted to varying degrees by such new environments. In addition, it has been noted that astronauts are quite heterogeneous in their response patterns, indicating that such variation is either silent if one remained on Earth, or the heterogeneity unknowingly contributes to disease development during aging or in response to insults. With the planned mission to deep space, humans will now be exposed to further risks from radiation when traveling beyond the influence of the GMF, as well as other potential risks that are associated with the actual loss of the GMF on the astronauts, their microbiomes, and growing food sources. Experimental studies with model systems have revealed that hypogravity conditions can influence a variety biological and physiological systems, and thus the loss of the GMF may have unanticipated consequences to astronauts’ systems, such as those that are electrical in nature (i.e., the cardiovascular system and central neural systems). As astronauts have been shown to be heterogeneous in their responses to LEO, they may require personalized countermeasures, while others may not be good candidates for deep-space missions if effective countermeasures cannot be developed for long-duration missions. This review will discuss several of the physiological and neural systems that are affected and how the emerging variables may influence astronaut health and functioning.
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8
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Harris KM, Arya R, Elias A, Weber T, Green DA, Greaves DK, Petersen LG, Roberts L, Kamine TH, Mazzolai L, Bergauer A, Kim DS, Olde Engberink RH, zu Eulenberg P, Grassi B, Zuccarelli L, Baldassarre G, Tabury K, Baatout S, Jordan J, Blaber AP, Choukér A, Russomano T, Goswami N. Pathophysiology, risk, diagnosis, and management of venous thrombosis in space: where are we now? NPJ Microgravity 2023; 9:17. [PMID: 36797288 PMCID: PMC9935502 DOI: 10.1038/s41526-023-00260-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Accepted: 01/20/2023] [Indexed: 02/18/2023] Open
Abstract
The recent incidental discovery of an asymptomatic venous thrombosis (VT) in the internal jugular vein of an astronaut on the International Space Station prompted a necessary, immediate response from the space medicine community. The European Space Agency formed a topical team to review the pathophysiology, risk and clinical presentation of venous thrombosis and the evaluation of its prevention, diagnosis, mitigation, and management strategies in spaceflight. In this article, we discuss the findings of the ESA VT Topical Team over its 2-year term, report the key gaps as we see them in the above areas which are hindering understanding VT in space. We provide research recommendations in a stepwise manner that build upon existing resources, and highlight the initial steps required to enable further evaluation of this newly identified pertinent medical risk.
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Affiliation(s)
- Katie M. Harris
- grid.25055.370000 0000 9130 6822Faculty of Medicine, Memorial University of Newfoundland, St. John’s, Canada
| | - Roopen Arya
- grid.429705.d0000 0004 0489 4320Kings College Hospital, NHS Foundation Trust, London, UK
| | - Antoine Elias
- Vascular Medicine, Toulon Hospital Centre, Toulon, France
| | - Tobias Weber
- Space Medicine Team, European Astronaut Centre, European Space Agency, Cologne, Germany. .,KBR, Cologne, Germany.
| | - David A. Green
- grid.461733.40000 0001 2375 6474Space Medicine Team, European Astronaut Centre, European Space Agency, Cologne, Germany ,KBR, Cologne, Germany ,grid.13097.3c0000 0001 2322 6764Centre for Human and Applied Physiological Sciences, King’s College London, London, UK
| | - Danielle K. Greaves
- grid.46078.3d0000 0000 8644 1405Faculty of Health, University of Waterloo, Waterloo, Canada
| | - Lonnie G. Petersen
- grid.5254.60000 0001 0674 042XDepartment of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark ,grid.116068.80000 0001 2341 2786Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, Cambridge, USA
| | - Lara Roberts
- grid.429705.d0000 0004 0489 4320Kings College Hospital, NHS Foundation Trust, London, UK
| | - Tovy Haber Kamine
- grid.281162.e0000 0004 0433 813XDivision of Trauma, Acute Care Surgery, and Surgical Critical Care, Baystate Medical Center, Springfield, MA USA
| | - Lucia Mazzolai
- grid.9851.50000 0001 2165 4204Department of Angiology, Lausanne University, Lausanne, Switzerland
| | | | - David S. Kim
- grid.461733.40000 0001 2375 6474Space Medicine Team, European Astronaut Centre, European Space Agency, Cologne, Germany ,grid.17091.3e0000 0001 2288 9830Department Emergency Medicine, University British Columbia, Vancouver, Canada
| | - Rik H. Olde Engberink
- grid.509540.d0000 0004 6880 3010Amsterdam UMC location University of Amsterdam, Department of Internal Medicine, Section of Nephrology, Amsterdam, The Netherlands ,Amsterdam Cardiovascular Sciences, Microcirculation, Amsterdam, The Netherlands
| | - Peter zu Eulenberg
- grid.5252.00000 0004 1936 973XInstitute for Neuroradiology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Bruno Grassi
- grid.5390.f0000 0001 2113 062XDepartment of Medicine, University of Udine, Udine, Italy
| | - Lucrezia Zuccarelli
- grid.5390.f0000 0001 2113 062XDepartment of Medicine, University of Udine, Udine, Italy
| | - Giovanni Baldassarre
- grid.5390.f0000 0001 2113 062XDepartment of Medicine, University of Udine, Udine, Italy
| | - Kevin Tabury
- grid.8953.70000 0000 9332 3503Radiobiology Unit, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium
| | - Sarah Baatout
- grid.8953.70000 0000 9332 3503Radiobiology Unit, Belgian Nuclear Research Centre, SCK CEN, Mol, Belgium
| | - Jens Jordan
- grid.7551.60000 0000 8983 7915Institute of Aerospace Medicine, German Aerospace Center and University of Cologne, Köln, Germany
| | - Andrew P. Blaber
- grid.61971.380000 0004 1936 7494Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC Canada
| | - Alexander Choukér
- grid.411095.80000 0004 0477 2585Translational Research Stress & Immunity, Klinik für Anästhesiologie/Forschungslabors, LMU Klinikum, München, Germany
| | - Thais Russomano
- grid.411095.80000 0004 0477 2585Translational Research Stress & Immunity, Klinik für Anästhesiologie/Forschungslabors, LMU Klinikum, München, Germany ,InnovaSpace UK, London, UK
| | - Nandu Goswami
- grid.11598.340000 0000 8988 2476Division of Physiology, Otto Löwi Research Center for Vascular Biology, Immunity and Inflammation, Medical University of Graz, Graz, Austria ,Mohammed Bin Rashid University of Medicine and Applied Health Sciences, Dubai, United Arab Emirates
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9
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Pardon LP, Greenwald SH, Ferguson CR, Patel NB, Young M, Laurie SS, Macias BR. Identification of Factors Associated With the Development of Optic Disc Edema During Spaceflight. JAMA Ophthalmol 2022; 140:1193-1200. [PMID: 36301519 PMCID: PMC9614681 DOI: 10.1001/jamaophthalmol.2022.4396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 09/01/2022] [Indexed: 01/12/2023]
Abstract
Importance Approximately 70% of crew members who complete long-duration missions to the International Space Station develop signs of optic disc edema, a hallmark finding of spaceflight-associated neuro-ocular syndrome. The onset and magnitude of edema differ across individuals, and the reason for this variability remains unknown. Identifying risk factors for spaceflight-induced disc edema is important because this condition may become more severe during extended-duration missions to the moon and Mars and could be associated with irreversible vision loss. Objective To assess whether preflight indicators of crowded optic nerve head morphology, other ocular measures (such as choroid thickness and axial length), body weight, body mass index, sex, age, and previous flight experience are associated with optic disc edema development. Design, Setting, and Participants This cohort study analyzed ocular, body weight, and demographic data collected from 31 US and international crew members before, during, and after spaceflight at the NASA Johnson Space Center and International Space Station. Ocular factors assessed included preflight and in-flight peripapillary total retinal thickness, minimum rim width, optic cup volume, mean cup depth, mean cup width, cup-disc ratio, Bruch membrane opening area, retinal nerve fiber layer thickness, choroid thickness, axial length, and refractive error. In addition, body weight, body mass index, sex, age, and previous spaceflight experience were assessed for associations with optic disc edema development. The data were analyzed from August 2021 to June 2022. Exposure Approximately 6 to 12 months of spaceflight. Main Outcomes and Measures In-flight increases in peripapillary total retinal thickness. Linear mixed models were used to assess for associations between a wide range of risk factors and in-flight increases in peripapillary total retinal thickness, which is a sensitive objective measure for detecting optic disc edema. Results This study included 31 International Space Station crew members with a mean (SD) age of 46.9 (6.0) years (25 men [80.6%]). During spaceflight, mean (SE) peripapillary total retinal thickness increased from 392.0 (5.8) μm to 430.2 (9.6) μm (P < .001), and greater individual changes were associated with smaller preflight cup volume (slope [SE], -62.8 [18.9]; P = .002), shallower preflight cup depth (slope [SE], -0.11 [0.03]; P < .001), and narrower preflight cup width (slope [SE], -0.03 [0.01]; P = .03). No associations were observed between changes in peripapillary total retinal thickness and any other variable evaluated. Conclusions and Relevance Findings of this cohort study suggest that smaller optic cup morphology may be associated with optic disc edema development during spaceflight. Crew members with this cup profile may benefit from enhanced ophthalmic monitoring during spaceflight and use of countermeasures against spaceflight-associated neuro-ocular syndrome.
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Affiliation(s)
| | | | | | | | - Millennia Young
- National Aeronautics and Space Administration Johnson Space Center, Houston, Texas
| | | | - Brandon R. Macias
- National Aeronautics and Space Administration Johnson Space Center, Houston, Texas
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10
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Van Akin MP, Lantz OM, Fellows AM, Toutain-Kidd C, Zegans M, Buckey JC, Anderson AP. Acute effects of postural changes and lower body positive and negative pressure on the eye. Front Physiol 2022; 13:933450. [PMID: 36117718 PMCID: PMC9470749 DOI: 10.3389/fphys.2022.933450] [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: 04/30/2022] [Accepted: 07/25/2022] [Indexed: 12/02/2022] Open
Abstract
Introduction: Entry into weightlessness results in a fluid shift and a loss of hydrostatic gradients. These factors are believed to affect the eye and contribute to the ocular changes that occur in space. We measured eye parameters during fluid shifts produced by lower body negative pressure (LBNP) and lower body positive pressure (LBPP) and changes in hydrostatic gradient direction (supine-prone) in normal subjects to assess the relative effects of fluid shifts and hydrostatic gradient changes on the eye. Methods: Ocular parameters (intraocular pressure (IOP), ocular geometry, and optical coherence tomography measures) were measured in the seated, supine, and prone positions. To create a fluid shift in the supine and prone positions, the lower body chamber pressure ranged from -40 mmHg to +40 mmHg. Subjects maintained each posture and LBNP/LBPP combination for 15 min prior to data collection. A linear mixed-effects model was used to determine the effects of fluid shifts (as reflected by LBNP/LBPP) and hydrostatic gradient changes (as reflected by the change from seated to supine and from seated to prone) on eye parameters. Results: Chamber pressure was positively correlated with both increased choroidal thickness (β = 0.11 ,p = 0.01) and IOP (β = 0.06 p < 0.001). The change in posture increased IOP compared to seated IOP (supine β = 2.1, p = 0.01, prone β = 9.5, p < 0.001 prone) but not choroidal thickness. IOP changes correlated with axial length (R = 0.72, p < 0.001). Discussion: The effects of hydrostatic gradients and fluids shifts on the eye were investigated by inducing a fluid shift in both the supine and prone postures. Both hydrostatic gradients (posture) and fluid shifts (chamber pressure) affected IOP, but only hydrostatic gradients affected axial length and aqueous depth. Changes in choroidal thickness were only significant for the fluid shifts. Changes in hydrostatic gradients can produce significant changes in both IOP and axial length. Fluid shifts are often cited as important factors in the pathophysiology of SANS, but the local loss of hydrostatic gradients in the head may also play an important role in these ocular findings.
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Affiliation(s)
- M. P. Van Akin
- University of Colorado Boulder, Ann and H.J. Smead Department of Aerospace Engineering Sciences, Boulder, CO, United States
| | - O. M. Lantz
- Geisel School of Medicine at Dartmouth College, Hanover, NH, United States
| | - A. M. Fellows
- Geisel School of Medicine at Dartmouth College, Hanover, NH, United States
| | | | - Michael Zegans
- Geisel School of Medicine at Dartmouth College, Hanover, NH, United States
| | - J. C. Buckey
- Geisel School of Medicine at Dartmouth College, Hanover, NH, United States
| | - A. P. Anderson
- University of Colorado Boulder, Ann and H.J. Smead Department of Aerospace Engineering Sciences, Boulder, CO, United States
- *Correspondence: A. P. Anderson,
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11
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Seidler RD, Stern C, Basner M, Stahn AC, Wuyts FL, zu Eulenburg P. Future research directions to identify risks and mitigation strategies for neurostructural, ocular, and behavioral changes induced by human spaceflight: A NASA-ESA expert group consensus report. Front Neural Circuits 2022; 16:876789. [PMID: 35991346 PMCID: PMC9387435 DOI: 10.3389/fncir.2022.876789] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 06/27/2022] [Indexed: 11/13/2022] Open
Abstract
A team of experts on the effects of the spaceflight environment on the brain and eye (SANS: Spaceflight-Associated Neuro-ocular Syndrome) was convened by NASA and ESA to (1) review spaceflight-associated structural and functional changes of the human brain and eye, and any interactions between the two; and (2) identify critical future research directions in this area to help characterize the risk and identify possible countermeasures and strategies to mitigate the spaceflight-induced brain and eye alterations. The experts identified 14 critical future research directions that would substantially advance our knowledge of the effects of spending prolonged periods of time in the spaceflight environment on SANS, as well as brain structure and function. They used a paired comparison approach to rank the relative importance of these 14 recommendations, which are discussed in detail in the main report and are summarized briefly below.
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Affiliation(s)
- Rachael D. Seidler
- Department of Applied Physiology & Kinesiology, Health and Human Performance, University of Florida, Gainesville, FL, United States
| | - Claudia Stern
- Department of Clinical Aerospace Medicine, German Aerospace Center (DLR) and ISS Operations and Astronauts Group, European Astronaut Centre, European Space Agency (ESA), Cologne, Germany
- *Correspondence: Claudia Stern,
| | - Mathias Basner
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Alexander C. Stahn
- Department of Psychiatry, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Floris L. Wuyts
- Department of Physics, University of Antwerp, Antwerp, Belgium
- Laboratory for Equilibrium Investigations and Aerospace (LEIA), Antwerp, Belgium
| | - Peter zu Eulenburg
- German Vertigo and Balance Center, University Hospital, Ludwig-Maximilians-Universität München (LMU), Munich, Germany
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12
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Whittle RS, Keller N, Hall EA, Vellore HS, Stapleton LM, Findlay KH, Dunbar BJ, Diaz‐Artiles A. Gravitational Dose‐Response Curves for Acute Cardiovascular Hemodynamics and Autonomic Responses in a Tilt Paradigm. J Am Heart Assoc 2022; 11:e024175. [PMID: 35861832 PMCID: PMC9707822 DOI: 10.1161/jaha.121.024175] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background
The cardiovascular system is strongly dependent on the gravitational environment. Gravitational changes cause mechanical fluid shifts and, in turn, autonomic effectors influence systemic circulation and cardiac control. We implemented a tilt paradigm to (1) investigate the acute hemodynamic response across a range of directions of the gravitational vector, and (2) to generate specific dose‐response relationships of this gravitational dependency.
Methods and Results
Twelve male subjects were tilted from 45° head‐up tilt to 45° head‐down tilt in 15° increments, in both supine and prone postures. We measured the steady‐state hemodynamic response in a range of variables including heart rate, stroke volume, cardiac output, oxygen consumption, total peripheral resistance, blood pressure, and autonomic indices derived from heart rate variability analysis. There is a strong gravitational dependence in almost all variables considered, with the exception of oxygen consumption, whereas systolic blood pressure remained controlled to within ≈3% across the tilt range. Hemodynamic responses are primarily driven by differential loading on the baroreflex receptors, combined with differences in venous return to the heart. Thorax compression in the prone position leads to reduced venous return and increased sympathetic nervous activity, raising heart rate, and systemic vascular resistance while lowering cardiac output and stroke volume.
Conclusions
Gravitational dose‐response curves generated from these data provide a comprehensive baseline from which to assess the efficacy of potential spaceflight countermeasures. Results also assist clinical management of terrestrial surgery in prone posture or head‐down tilt positions.
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Affiliation(s)
- Richard S. Whittle
- Department of Aerospace Engineering Texas A&M University College Station TX
| | - Nathan Keller
- Department of Health and Kinesiology Texas A&M University College Station TX
| | - Eric A. Hall
- Department of Biomedical Engineering Texas A&M University College Station TX
| | | | | | | | - Bonnie J. Dunbar
- Department of Aerospace Engineering Texas A&M University College Station TX
| | - Ana Diaz‐Artiles
- Department of Aerospace Engineering Texas A&M University College Station TX
- Department of Health and Kinesiology Texas A&M University College Station TX
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13
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Wostyn P, Mader TH, Gibson CR, Nedergaard M. Does Long-Duration Exposure to Microgravity Lead to Dysregulation of the Brain and Ocular Glymphatic Systems? Eye Brain 2022; 14:49-58. [PMID: 35546965 PMCID: PMC9081191 DOI: 10.2147/eb.s354710] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 04/27/2022] [Indexed: 02/05/2023] Open
Abstract
Spaceflight-associated neuro-ocular syndrome (SANS) has been well documented in astronauts both during and after long-duration spaceflight and is characterized by the development of optic disc edema, globe flattening, choroidal folds, and hyperopic refractive error shifts. The exact mechanisms underlying these ophthalmic abnormalities remain unclear. New findings regarding spaceflight-associated alterations in cerebrospinal fluid spaces, specifically perivascular spaces, may shed more light on the pathophysiology of SANS. The preliminary results of a recent brain magnetic resonance imaging study show that perivascular spaces enlarge under prolonged microgravity conditions, and that the amount of fluid in perivascular spaces is linked to SANS. The exact pathophysiological mechanisms underlying enlargement of perivascular spaces in space crews are currently unclear. Here, we speculate that the dilation of perivascular spaces observed in long-duration space travelers may result from impaired cerebral venous outflow and compromised cerebrospinal fluid resorption, leading to obstruction of glymphatic perivenous outflow and increased periarterial cerebrospinal fluid inflow, respectively. Further, we provide a possible explanation for how dilated perivascular spaces can be associated with SANS. Given that enlarged perivascular spaces in space crews may be a marker of altered venous hemodynamics and reduced cerebrospinal fluid outflow, at the level of the optic nerve and eye, these disturbances may contribute to SANS. If confirmed by further studies, brain glymphatic dysfunction in space crews could potentially be considered a risk factor for the development of neurodegenerative diseases, such as Alzheimer’s disease. Furthermore, long-duration exposure to microgravity might contribute to SANS through dysregulation of the ocular glymphatic system. If prolonged spaceflight exposure causes disruption of the glymphatic systems, this might affect the ability to conduct future exploration missions, for example, to Mars. The considerations outlined in the present paper further stress the crucial need to develop effective long-term countermeasures to mitigate SANS-related physiologic changes during long-duration spaceflight.
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Affiliation(s)
- Peter Wostyn
- Department of Psychiatry, PC Sint-Amandus, Beernem, Belgium
- Correspondence: Peter Wostyn, Department of Psychiatry, PC Sint-Amandus, Reigerlostraat 10, Beernem, 8730, Belgium, Tel +32-472713719, Fax +32-50-819720, Email
| | | | - Charles Robert Gibson
- Coastal Eye Associates, Webster, TX, USA
- KBR, NASA Space Medicine Operations Division, Houston, TX, USA
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, USA
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14
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The effect of prolonged spaceflight on cerebrospinal fluid and perivascular spaces of astronauts and cosmonauts. Proc Natl Acad Sci U S A 2022; 119:e2120439119. [PMID: 35412862 PMCID: PMC9169932 DOI: 10.1073/pnas.2120439119] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Long-duration spaceflight induces changes to the brain and cerebrospinal fluid compartments and visual acuity problems known as spaceflight-associated neuro-ocular syndrome (SANS). The clinical relevance of these changes and whether they equally affect crews of different space agencies remain unknown. We used MRI to analyze the alterations occurring in the perivascular spaces (PVS) in NASA and European Space Agency astronauts and Roscosmos cosmonauts after a 6-mo spaceflight on the International Space Station (ISS). We found increased volume of basal ganglia PVS and white matter PVS (WM-PVS) after spaceflight, which was more prominent in the NASA crew than the Roscosmos crew. Moreover, both crews demonstrated a similar degree of lateral ventricle enlargement and decreased subarachnoid space at the vertex, which was correlated with WM-PVS enlargement. As all crews experienced the same environment aboard the ISS, the differences in WM-PVS enlargement may have been due to, among other factors, differences in the use of countermeasures and high-resistive exercise regimes, which can influence brain fluid redistribution. Moreover, NASA astronauts who developed SANS had greater pre- and postflight WM-PVS volumes than those unaffected. These results provide evidence for a potential link between WM-PVS fluid and SANS.
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15
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Buckey JC, Lan M, Phillips SD, Archambault-Leger V, Fellows AM. A theory for why the spaceflight-associated neuro-ocular syndrome develops. J Appl Physiol (1985) 2022; 132:1201-1203. [PMID: 35201930 PMCID: PMC9054259 DOI: 10.1152/japplphysiol.00854.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Affiliation(s)
- Jay C Buckey
- Geisel School of Medicine, Dartmouth College, Lebanon, NH, United States
| | - Mimi Lan
- Thayer School of Engineering, Dartmouth College, Hanover, NH, United States
| | | | | | - Abigail M Fellows
- Geisel School of Medicine, Dartmouth College, Lebanon, NH, United States
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16
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Khan S, Kirubarajan A, Lee M, Pitha I, Buckey JC. The Correlation Between Body Weight and Intraocular Pressure. Aerosp Med Hum Perform 2021; 92:886-897. [PMID: 34819215 DOI: 10.3357/amhp.5769.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
INTRODUCTION: Preflight body weight is a strong predictor of visual changes in spaceflight. To understand the effect of body weight on the eye, we examined the effect of increased body mass index on intraocular pressure on Earth.METHODS: We conducted a systematic review to summarize the relationship between weight parameters (including body mass index (BMI) and obesity indices), and intraocular pressure (IOP). Study selection and data extraction were performed in duplicate using EMBASE, MEDLINE, and CENTRAL, from database inception to the second week of April 2020.RESULTS: A total of 66 individual studies were included for qualitative analysis from the 1364 studies eligible for title and abstract screening. A total of 39 studies were available for quantitative analysis. The average BMI was 25.9 (range, 20.148.8) and the average IOP was 14.9 mmHg (range, 11.627.8). The overall pooled RR between BMI and elevated intraocular pressure (IOP) was 1.06 (95 CI%, 1.041.07), meaning for each unit increase in BMI one is 6 more likely of having higher IOP than baseline. Two studies assessed the effects of bariatric surgery, and both showed significant decreases in IOP postoperatively.CONCLUSION: A higher BMI was associated with increased IOP in ground-based studies. IOP also decreased with weight loss. These data support the idea that alterations in body weight affect intraocular pressures. Further research is needed to understand the relationship between body weight, IOP, and microgravity-induced visual changes. This finding may also be useful clinically.Khan S, Kirubarajan A, Lee M, Pitha I, Buckey JC Jr. The correlation between body weight and intraocular pressure. Aerosp Med Hum Perform. 2021; 92(11):886-897.
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17
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Taibbi G, Young M, Vyas RJ, Murray MC, Lim S, Predovic M, Jacobs NM, Askin KN, Mason SS, Zanello SB, Vizzeri G, Theriot CA, Parsons-Wingerter P. Opposite response of blood vessels in the retina to 6° head-down tilt and long-duration microgravity. NPJ Microgravity 2021; 7:38. [PMID: 34650071 PMCID: PMC8516890 DOI: 10.1038/s41526-021-00165-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Accepted: 08/19/2021] [Indexed: 01/13/2023] Open
Abstract
The Spaceflight Associated Neuro-ocular Syndrome (SANS), associated with the headward fluid shifts incurred in microgravity during long-duration missions, remains a high-priority health and performance risk for human space exploration. To help characterize the pathophysiology of SANS, NASA's VESsel GENeration Analysis (VESGEN) software was used to map and quantify vascular adaptations in the retina before and after 70 days of bed rest at 6-degree Head-Down Tilt (HDT), a well-studied microgravity analog. Results were compared to the retinal vascular response of astronauts following 6-month missions to the International Space Station (ISS). By mixed effects modeling, the trends of vascular response were opposite. Vascular density decreased significantly in the 16 retinas of eight astronauts and in contrast, increased slightly in the ten retinas of five subjects after HDT (although with limited significance). The one astronaut retina diagnosed with SANS displayed the greatest vascular loss. Results suggest that microgravity is a major variable in the retinal mediation of fluid shifts that is not reproduced in this HDT bed rest model.
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Affiliation(s)
- Giovanni Taibbi
- Department of Ophthalmology and Visual Sciences, The University of Texas Medical Branch at Galveston, Galveston, TX, USA
| | | | - Ruchi J Vyas
- Mori Associates, Ames Research Center, NASA, Moffett Field, Mountain View, CA, USA
| | - Matthew C Murray
- Blue Marble Space Institute of Science, Space Biology Division, Space Technology Mission Directorate, Ames Research Center, NASA, Moffett Field, Mountain View, CA, USA
| | - Shiyin Lim
- Blue Marble Space Institute of Science, Space Biology Division, Space Technology Mission Directorate, Ames Research Center, NASA, Moffett Field, Mountain View, CA, USA
| | - Marina Predovic
- Blue Marble Space Institute of Science, Space Biology Division, Space Technology Mission Directorate, Ames Research Center, NASA, Moffett Field, Mountain View, CA, USA
| | - Nicole M Jacobs
- Blue Marble Space Institute of Science, Space Biology Division, Space Technology Mission Directorate, Ames Research Center, NASA, Moffett Field, Mountain View, CA, USA
| | - Kayleigh N Askin
- National Space Biomedical Research Institute, Ames Research Center, NASA, Moffett Field, Mountain View, CA, USA
| | | | | | - Gianmarco Vizzeri
- Department of Ophthalmology and Visual Sciences, The University of Texas Medical Branch at Galveston, Galveston, TX, USA
| | - Corey A Theriot
- KBR, NASA Johnson Space Center, Houston, TX, USA
- Department of Preventive Medicine and Community Health, The University of Texas Medical Branch, Galveston, TX, USA
| | - Patricia Parsons-Wingerter
- Low Gravity Exploration Technology, Research and Engineering Directorate, John Glenn Research Center, NASA, Cleveland, OH, USA.
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18
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Wostyn P, Gibson CR, Mader TH. Optic nerve sheath stiffness as a predictive biomarker for optic disc edema in astronauts. J Mech Behav Biomed Mater 2021; 124:104846. [PMID: 34555625 DOI: 10.1016/j.jmbbm.2021.104846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 07/24/2021] [Accepted: 09/17/2021] [Indexed: 11/30/2022]
Affiliation(s)
- Peter Wostyn
- Department of Psychiatry, PC Sint-Amandus, Beernem, Belgium.
| | - Charles Robert Gibson
- Coastal Eye Associates, Webster, TX, USA; KBR, NASA Space Medicine Operations Division, Houston, TX, USA.
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19
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Smith TG, Buckey JC. Anaesthetists and aerospace medicine in a new era of human spaceflight. Anaesthesia 2021; 77:384-388. [PMID: 34496029 DOI: 10.1111/anae.15580] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/14/2021] [Indexed: 01/31/2023]
Affiliation(s)
- T G Smith
- Centre for Human and Applied Physiological Sciences, King's College London, UK.,Department of Anaesthesia, Guy's and St Thomas' NHS Foundation Trust, London, UK
| | - J C Buckey
- Space Medicine Innovations Laboratory, Geisel School of Medicine, Dartmouth College, Hanover, NH, USA.,Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA
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20
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Abstract
History books are rife with examples of the role of nutrition in determining either the success or the failure of human exploration on Earth. With planetary exploration in our future, it is imperative that we understand the role of nutrition in optimizing health before humans can safely take the next giant leaps in space exploration.
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Affiliation(s)
- Scott M Smith
- Human Health and Performance Directorate, NASA Johnson Space Center, Houston, Texas
| | - Sara R Zwart
- University of Texas Medical Branch, Galveston, Texas
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21
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Lan M, Phillips SD, Archambault-Leger V, Chepko AB, Lu R, Anderson AP, Masterova KS, Fellows AM, Halter RJ, Buckey JC. Proposed mechanism for reduced jugular vein flow in microgravity. Physiol Rep 2021; 9:e14782. [PMID: 33931957 PMCID: PMC8087922 DOI: 10.14814/phy2.14782] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 01/22/2021] [Accepted: 01/31/2021] [Indexed: 12/03/2022] Open
Abstract
Internal jugular flow is reduced in space compared with supine values, which can be associated with internal jugular vein (IJV) thrombosis. The mechanism is unknown but important to understand to prevent potentially serious vein thromboses on long duration flights. We used a novel, microgravity‐focused numerical model of the cranial vascular circulation to develop hypotheses for the reduced flow. This model includes the effects of removing hydrostatic gradients and tissue compressive forces – unique effects of weightlessness. The IJV in the model incorporates sensitivity to transmural pressure across the vein, which can dramatically affect resistance and flow in the vein. The model predicts reduced IJV flow in space. Although tissue weight in the neck is reduced in weightlessness, increasing transmural pressure, this is more than offset by the reduction in venous pressure produced by the loss of hydrostatic gradients and tissue pressures throughout the body. This results in a negative transmural pressure and increased IJV resistance. Unlike the IJV, the walls of the vertebral plexus are rigid; transmural pressure does not affect its resistance and so its flow increases in microgravity. This overall result is supported by spaceflight measurements, showing reduced IJV area inflight compared with supine values preflight. Significantly, this hypothesis suggests that interventions that further decrease internal IJV pressure (such as lower body negative pressure), which are not assisted by other drainage mechanisms (e.g. gravity), might lead to stagnant flow or IJV collapse with reduced flow, which could increase rather than decrease the risk of venous thrombosis.
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Affiliation(s)
- Mimi Lan
- Thayer School of Engineering at Dartmouth, Hanover, NH, USA
| | | | | | | | | | | | | | | | - Ryan J Halter
- Thayer School of Engineering at Dartmouth, Hanover, NH, USA
| | - Jay C Buckey
- Geisel School of Medicine at Dartmouth College, Lebanon, NH, USA
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22
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Whittle RS, Diaz-Artiles A. Modeling individual differences in cardiovascular response to gravitational stress using a sensitivity analysis. J Appl Physiol (1985) 2021; 130:1983-2001. [PMID: 33914657 DOI: 10.1152/japplphysiol.00727.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The human cardiovascular (CV) system elicits a physiological response to gravitational environments, with significant variation between different individuals. Computational modeling can predict CV response, however model complexity and variation of physiological parameters in a normal population makes it challenging to capture individual responses. We conducted a sensitivity analysis on an existing 21-compartment lumped-parameter hemodynamic model in a range of gravitational conditions to 1) investigate the influence of model parameters on a tilt test CV response and 2) to determine the subset of those parameters with the most influence on systemic physiological outcomes. A supine virtual subject was tilted to upright under the influence of a constant gravitational field ranging from 0 g to 1 g. The sensitivity analysis was conducted using a Latin hypercube sampling/partial rank correlation coefficient methodology with subsets of model parameters varied across a normal physiological range. Sensitivity was determined by variation in outcome measures including heart rate, stroke volume, central venous pressure, systemic blood pressures, and cardiac output. Results showed that model parameters related to the length, resistance, and compliance of the large veins and parameters related to right ventricular function have the most influence on model outcomes. For most outcome measures considered, parameters related to the heart are dominant. Results highlight which model parameters to accurately value in simulations of individual subjects' CV response to gravitational stress, improving the accuracy of predictions. Influential parameters remain largely similar across gravity levels, highlighting that accurate model fitting in 1 g can increase the accuracy of predictive responses in reduced gravity.NEW & NOTEWORTHY Computational modeling is used to predict cardiovascular responses to altered gravitational environments. However, considerable variation between subjects and model complexity makes accurate parameter assignment for individuals challenging. This computational effort studies sensitivity in cardiovascular model outcomes due to varying parameters across a normal physiological range. This allows determination of which parameters have the largest influence on outcomes, i.e., which parameters must be most carefully selected to give accurate predictions of individual responses.
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Affiliation(s)
- Richard S Whittle
- Department of Aerospace Engineering, Texas A&M University, College Station, Texas
| | - Ana Diaz-Artiles
- Department of Aerospace Engineering, Texas A&M University, College Station, Texas.,Department of Health and Kinesiology, Texas A&M University, College Station, Texas
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Abstract
PURPOSE OF REVIEW Several decades of long duration space flight missions by the National Aeronautics and Space Administration has revealed an interesting and unique constellation of neuro-ophthalmic findings now called spaceflight associated neuro-ocular syndrome (SANS). The unique space environment of microgravity produces novel physiological changes and derangements that present a challenge to astronauts in current and future long duration space missions. Although the precise mechanism of SANS is not fully understood, in this review, we examine recent developments that may to help explain possible causes and potential countermeasures. RECENT FINDINGS The cause of SANS is still largely unknown. A growing body of evidence implicates multiple factors that contribute to the development of SANS including cephalad fluid shifts, increased intracranial pressure, venous/lymphatic stasis, inflammation, metabolism, axoplasmic stasis and radiation exposure. SUMMARY The pathologic mechanism behind SANS may be multifactorial and may be amenable to different countermeasures for prevention and management of SANS.
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24
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Scott JPR, Green DA, Weerts G, Cheuvront SN. Body size and its implications upon resource utilization during human space exploration missions. Sci Rep 2020; 10:13836. [PMID: 32796944 PMCID: PMC7429865 DOI: 10.1038/s41598-020-70054-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Accepted: 06/30/2020] [Indexed: 11/09/2022] Open
Abstract
The purpose of this theoretical study was to estimate the effects of body size and countermeasure (CM) exercise in an all-male crew composed of individuals drawn from a height range representative of current space agency requirements upon total energy expenditure (TEE), oxygen (O2) consumption, carbon dioxide (CO2) and metabolic heat (Hprod) production, and water requirements for hydration, during space exploration missions. Using a height range of 1.50- to 1.90-m, and assuming geometric similarity across this range, estimates were derived for a four-person male crew (age: 40-years; BMI: 26.5-kg/m2; resting VO2 and VO2max: 3.3- and 43.4-mL/kg/min) on 30- to 1,080-d missions, without and with, ISS-like CM exercise (modelled as 2 × 30-min aerobic exercise at 75% VO2max, 6-d/week). Where spaceflight-specific data/equations were not available, terrestrial data/equations were used. Body size alone increased 24-h TEE (+ 44%), O2 consumption (+ 60%), CO2 (+ 60%) and Hprod (+ 60%) production, and water requirements (+ 19%). With CM exercise, the increases were + 29 to 32%, + 31%, + 35%, + 42% and + 23 to 33% respectively, across the height range. Compared with a 'small-sized' (1.50-m) crew without CM exercise, a 'large-sized' (1.90-m) crew exercising would require an additional 996-MJ of energy, 52.5 × 103-L of O2 and 183.6-L of water, and produce an additional 44.0 × 103-L of CO2 and 874-MJ of heat each month. This study provides the first insight into the potential implications of body size and the use of ISS-like CM exercise upon the provision of life-support during exploration missions. Whilst closed-loop life-support (O2, water and CO2) systems may be possible, strategies to minimize and meet crew metabolic energy needs, estimated in this study to increase by 996-MJ per month with body size and CM exercise, are required.
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Affiliation(s)
- Jonathan P R Scott
- KBR, 511147, Cologne, Germany.
- Space Medicine Team, European Astronaut Centre, European Space Agency, 51147, Cologne, Germany.
| | - David A Green
- KBR, 511147, Cologne, Germany
- Space Medicine Team, European Astronaut Centre, European Space Agency, 51147, Cologne, Germany
- Centre of Human and Applied Physiological Sciences, King's College London, London, SE1 1UL, UK
| | - Guillaume Weerts
- Space Medicine Team, European Astronaut Centre, European Space Agency, 51147, Cologne, Germany
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Shen G, Link SS, Tao X, Frankfort BJ. Modeling a potential SANS countermeasure by experimental manipulation of the translaminar pressure difference in mice. NPJ Microgravity 2020; 6:19. [PMID: 32821777 PMCID: PMC7395713 DOI: 10.1038/s41526-020-00109-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 07/06/2020] [Indexed: 12/23/2022] Open
Abstract
The spaceflight-associated neuro-ocular syndrome (SANS), which may present after prolonged exposure to microgravity, is thought to occur due to elevated intracranial pressure (ICP). Intracranial pressure interacts with intraocular pressure (IOP) to define the translaminar pressure difference (TLPD; IOP-ICP). We combined inducible models of ICP and IOP elevation in mice to interrogate the relationships among ICP, IOP, and TLPD, and to determine if IOP elevation could mitigate the phenotypes typically caused by elevated ICP and thereby serve as a countermeasure for SANS. Ten C57BL6J mice of both genders underwent experimental elevation of ICP via infusion of artificial cerebrospinal fluid into the subarachnoid space. One eye also underwent experimental elevation of IOP using the bead injection model. Intraocular pressure and ICP were monitored for 2 weeks. Optokinetic-based contrast sensitivity was measured at baseline and after 2 weeks, and post-mortem studies of optic nerve and retina anatomy were performed. Photopic contrast sensitivity was reduced more in IOP elevated than control eyes. Scotopic contrast sensitivity was reduced similarly in IOP elevated and control eyes. However, the pattern of scotopic vision loss was not uniform in IOP elevated eyes; there was minimal loss in eyes that most closely approximated the normal TLPD. Optic nerve axon loss, increased optic nerve disorganization, and retinal ganglion cell loss all occurred similarly between IOP elevated and control eyes. Elevation of IOP in eyes with elevated ICP may counterbalance some effects on vision loss but exacerbate others, suggesting complex relationships among IOP, ICP, and TLPD.
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Affiliation(s)
- Guofu Shen
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX USA
| | - Schuyler S. Link
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX USA
| | - Xiaofeng Tao
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX USA
| | - Benjamin J. Frankfort
- Department of Ophthalmology, Baylor College of Medicine, Houston, TX USA
- Department of Neuroscience, Baylor College of Medicine, Houston, TX USA
- Center for Space Medicine, Baylor College of Medicine, Houston, TX USA
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Wojcik P, Batliwala S, Rowsey T, Galdamez LA, Lee AG. Spaceflight-Associated Neuro-ocular Syndrome (SANS): a review of proposed mechanisms and analogs. EXPERT REVIEW OF OPHTHALMOLOGY 2020. [DOI: 10.1080/17469899.2020.1787155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Peter Wojcik
- Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX, USA
| | - Shehzad Batliwala
- Department of Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | - Tyler Rowsey
- College of Medicine, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | - Laura A. Galdamez
- Department of Emergency Medicine, Memorial Hermann The Woodlands, Shenandoah, TX, USA
| | - Andrew G. Lee
- Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX, USA
- Departments of Ophthalmology, Neurology, and Neurosurgery, Weill Cornell Medicine, New York, NY, USA
- Department of Ophthalmology, University of Texas Medical Branch, Galveston, TX, USA
- Department of Ophthalmology, University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Texas A and M College of Medicine, Bryan, TX, USA
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Wåhlin A, Holmlund P, Fellows AM, Malm J, Buckey JC, Eklund A. Optic Nerve Length before and after Spaceflight. Ophthalmology 2020; 128:309-316. [PMID: 32659310 DOI: 10.1016/j.ophtha.2020.07.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 07/02/2020] [Accepted: 07/06/2020] [Indexed: 10/23/2022] Open
Abstract
PURPOSE The spaceflight-associated neuro-ocular syndrome (SANS) affects astronauts on missions to the International Space Station (ISS). The SANS has blurred vision and ocular changes as typical features. The objective of this study was to investigate if microgravity can create deformations or movements of the eye or optic nerve, and if such changes could be linked to SANS. DESIGN Cohort study. PARTICIPANTS Twenty-two astronauts (age 48 ± 4 years). METHODS The intervention consisted of time in microgravity at the ISS. We co-registered pre- and postspaceflight magnetic resonance imaging (MRI) scans and generated centerline representations of the optic nerve. The coordinates for the optic nerve head (ONH) and optic chiasm (OC) ends of the optic nerve were recorded along with the entire centerline path. MAIN OUTCOME MEASURES Optic nerve length, ONH movement, and OC movement after time in microgravity. RESULTS Optic nerve length increased (0.80 ± 0.74 mm, P < 0.001), primarily reflecting forward ONH displacement (0.63 ± 0.53 mm, P < 0.001). The forward displacement was positively related to mission duration, preflight body weight, and clinical manifestations of SANS. We also detected upward displacement of the OC (0.39 ± 0.50 mm, P = 0.002), indicative of brain movement, but this observation could not be linked to SANS. CONCLUSIONS The spaceflight-induced optic nerve lengthening and anterior movement of the ONH support that SANS is caused by an altered pressure difference between the brain and the eye, leading to a forward push on the posterior of the eye. Body weight is a potential contributing risk factor. Direct assessment of intracranial pressure in space is required to verify the implicated mechanism behind the ocular findings in SANS.
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Affiliation(s)
- Anders Wåhlin
- Department of Radiation Sciences, Umeå University, Umeå, Sweden; Umeå Center for Functional Brain Imaging, Umeå University, Umeå, Sweden
| | - Petter Holmlund
- Department of Radiation Sciences, Umeå University, Umeå, Sweden
| | | | - Jan Malm
- Department of Clinical Science, Umeå University, Umeå, Sweden
| | - Jay C Buckey
- Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire
| | - Anders Eklund
- Department of Radiation Sciences, Umeå University, Umeå, Sweden; Umeå Center for Functional Brain Imaging, Umeå University, Umeå, Sweden.
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Elwy R, Soliman MA, Hasanain AA, Ezzat AA, Elbaroody M, Alsawy MF, El Refaee E. Visual changes after space flight: is it really caused by increased intracranial tension? A systematic review. J Neurosurg Sci 2020; 64:468-479. [PMID: 32347675 DOI: 10.23736/s0390-5616.20.04927-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
INTRODUCTION Spaceflight-Associated Neuro-ocular Syndrome (SANS) was linked to increased intracranial pressure (ICP) attributable to the combined effects of microgravity and environmental conditions encountered during spaceflight. Microgravity countermeasures as lower body negative pressure (LBNP) are potential interventions for SANS. Our aim is to provide a comprehensive qualitative analysis of literature contrasting simulation and spaceflight studies, focusing on the pathophysiology of SANS, and highlighting gaps in current knowledge. EVIDENCE ACQUISITION We systematically searched PubMed electronic database for English primary research published until February 2019 discussing intracranial changes in spaceflight or simulated microgravity, excluding animal and experimental studies. Two authors screened all the abstracts with a third author resolving disagreements. The full-text manuscripts were analyzed in pilot-tested tables. EVIDENCE SYNTHESIS Nineteen studies were reviewed; 13 simulation, and two out of six spaceflight studies were prospective. ICP changes were investigated in 11 simulation studies, where eight demonstrated a significant increase in ICP after variable periods of head-down tilt. three showed a significant increase in intraocular pressure (IOP) in conjunction with ICP elevation. With increasing ambient CO<inf>2</inf>: one showed an increase in IOP without further increase in ICP, while another showed a slight further decrease in ICP. LBNP demonstrated no significant effect on ICP in one and a decrease thereof in another study. After spaceflight, increased ICP on lumbar puncture was demonstrated in five studies. CONCLUSIONS Exposure to microgravity increases ICP possibly precipitating ocular changes. Whether other factors come into play is the subject of investigation. Further randomized studies and methods of direct ICP measurement during spaceflight are needed.
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Affiliation(s)
- Reem Elwy
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Mohamed A Soliman
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt - .,Department of Neurosurgery, Western University, London, ON, Canada
| | - Amr A Hasanain
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Ahmed A Ezzat
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Mohammad Elbaroody
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Mohamed F Alsawy
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Ehab El Refaee
- Department of Neurosurgery, Faculty of Medicine, Cairo University, Cairo, Egypt.,Department of Neurosurgery, University Medicine Greifswald, Greifswald, Germany
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Spaceflight associated neuro-ocular syndrome (SANS) and the neuro-ophthalmologic effects of microgravity: a review and an update. NPJ Microgravity 2020; 6:7. [PMID: 32047839 PMCID: PMC7005826 DOI: 10.1038/s41526-020-0097-9] [Citation(s) in RCA: 107] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 11/11/2019] [Indexed: 11/08/2022] Open
Abstract
Prolonged microgravity exposure during long-duration spaceflight (LDSF) produces unusual physiologic and pathologic neuro-ophthalmic findings in astronauts. These microgravity associated findings collectively define the “Spaceflight Associated Neuro-ocular Syndrome” (SANS). We compare and contrast prior published work on SANS by the National Aeronautics and Space Administration’s (NASA) Space Medicine Operations Division with retrospective and prospective studies from other research groups. In this manuscript, we update and review the clinical manifestations of SANS including: unilateral and bilateral optic disc edema, globe flattening, choroidal and retinal folds, hyperopic refractive error shifts, and focal areas of ischemic retina (i.e., cotton wool spots). We also discuss the knowledge gaps for in-flight and terrestrial human research including potential countermeasures for future study. We recommend that NASA and its research partners continue to study SANS in preparation for future longer duration manned space missions.
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Brain Physiological Response and Adaptation During Spaceflight. Neurosurgery 2019; 85:E815-E821. [DOI: 10.1093/neuros/nyz203] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 02/11/2019] [Indexed: 01/17/2023] Open
Abstract
Abstract
More than half of astronauts returning from long-duration missions on the International Space Station present with neuro-ocular structural and/or functional changes, including optic disc edema, optic nerve sheath distension, globe flattening, choroidal folds, or hyperopic shifts. This spaceflight-associated neuro-ocular syndrome (SANS) represents a major risk to future exploration class human spaceflight missions, including Mars missions. Although the exact pathophysiology of SANS is unknown, evidence thus far suggests that an increase in intracranial pressure (ICP) relative to the upright position on Earth, which is due to the loss of hydrostatic pressure gradients in space, may play a leading role. This review focuses on brain physiology in the spaceflight environment, specifically on how spaceflight may affect ICP and related indicators of cranial compliance, potential factors related to the development of SANS, and findings from spaceflight as well as ground-based spaceflight analog research studies.
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Affiliation(s)
- Jan Stepanek
- From the Aerospace Medicine and Vestibular Research Laboratory, Mayo Clinic, Scottsdale, AZ (J.S., R.S.B.); and Fluidity Technologies, Houston (S.P.)
| | - Rebecca S Blue
- From the Aerospace Medicine and Vestibular Research Laboratory, Mayo Clinic, Scottsdale, AZ (J.S., R.S.B.); and Fluidity Technologies, Houston (S.P.)
| | - Scott Parazynski
- From the Aerospace Medicine and Vestibular Research Laboratory, Mayo Clinic, Scottsdale, AZ (J.S., R.S.B.); and Fluidity Technologies, Houston (S.P.)
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