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Stepanek J, Blue RS, Connolly D. Pulmonary Function in Human Spaceflight. Semin Respir Crit Care Med 2023; 44:696-704. [PMID: 37459884 DOI: 10.1055/s-0043-1770064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/12/2023]
Abstract
Human spaceflight is entering a time of markedly increased activity fueled by collaboration between governmental and private industry entities. This has resulted in successful mission planning for destinations in low Earth orbit, lunar destinations (Artemis program, Gateway station) as well as exploration to Mars. The planned construction of additional commercial space stations will ensure continued low Earth orbit presence and destinations for science but also commercial spaceflight participants. The human in the journey to space is exposed to numerous environmental challenges including increased gravitational forces, microgravity, altered human physiology during adaptation to weightlessness in space, altered ambient pressure, as well as other important stressors contingent on the type of mission and destination. This chapter will cover clinically important aspects relevant to lung function in a normally proceeding mission; emergency scenarios such as decompression, fire, etc., will not be covered as these are beyond the scope of this review. To date, participation in commercial spaceflight by those with pre-existing chronic medical conditions is very limited, and hence, close collaboration between practicing pulmonary specialists and aerospace medicine specialists is of critical importance to guarantee safety, proper clinical management, and hence success in these important endeavors.
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Affiliation(s)
- Jan Stepanek
- Aerospace Medicine Program, Department of Medicine, Mayo Clinic, Scottsdale, Arizona
| | - Rebecca S Blue
- Aerospace Medicine Program Aerospace Medicine and Vestibular Research Laboratory (AMVRL), Mayo Clinic, Scottsdale, Arizona
| | - Desmond Connolly
- Human Performance, Air & Space Division, QinetiQ Plc, Farnborough, United Kingdom
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Karlsson LL, Van Muylem A, Linnarsson D. Lung diffusing capacity for nitric oxide in space: microgravity gas density interactions. Front Physiol 2023; 14:1161062. [PMID: 37228824 PMCID: PMC10203558 DOI: 10.3389/fphys.2023.1161062] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Accepted: 04/19/2023] [Indexed: 05/27/2023] Open
Abstract
Introduction: During manned space exploration lung health is threatened by toxic planetary dust and radiation. Thus, tests such as lung diffusing capacity (DL) are likely be used in planetary habitats to monitor lung health. During a DL maneuver the rate of uptake of an inspired blood-soluble gas such as nitric oxide (NO) is determined (DLNO). The aim of this study was to investigate the influence of altered gravity and reduced atmospheric pressure on the test results, since the atmospheric pressure in a habitat on the moon or on Mars is planned to be lower than on Earth. Changes of gravity are known to alter the blood filling of the lungs which in turn may modify the rate of gas uptake into the blood, and changes of atmospheric pressure may alter the speed of gas transport in the gas phase. Methods: DLNO was determined in 11 subjects on the ground and in microgravity on the International Space Station. Experiments were performed at both normal (1.0 atm absolute, ata) and reduced (0.7 ata) atmospheric pressures. Results: On the ground, DLNO did not differ between pressures, but in microgravity DLNO was increased by 9.8% (9.5) (mean [SD]) and 18.3% (15.8) at 1.0 and 0.7 ata respectively, compared to normal gravity, 1.0 ata. There was a significant interaction between pressure and gravity (p = 0.0135). Discussion: Estimates of the membrane (DmNO) and gas phase (DgNO) components of DLNO suggested that at normal gravity a reduced pressure led to opposing effects in convective and diffusive transport in the gas phase, with no net effect of pressure. In contrast, a DLNO increase with reduced pressure at microgravity is compatible with a substantial increase of DmNO partially offset by reduced DgNO, the latter being compatible with interstitial edema. In microgravity therefore, DmNO would be proportionally underestimated from DLNO. We also conclude that normal values for DL in anticipation of planetary exploration should be determined not only on the ground but also at the gravity and pressure conditions of a future planetary habitat.
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Affiliation(s)
- Lars L. Karlsson
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | | | - Dag Linnarsson
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
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Krittanawong C, Singh NK, Scheuring RA, Urquieta E, Bershad EM, Macaulay TR, Kaplin S, Dunn C, Kry SF, Russomano T, Shepanek M, Stowe RP, Kirkpatrick AW, Broderick TJ, Sibonga JD, Lee AG, Crucian BE. Human Health during Space Travel: State-of-the-Art Review. Cells 2022; 12:cells12010040. [PMID: 36611835 PMCID: PMC9818606 DOI: 10.3390/cells12010040] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 12/05/2022] [Accepted: 12/07/2022] [Indexed: 12/24/2022] Open
Abstract
The field of human space travel is in the midst of a dramatic revolution. Upcoming missions are looking to push the boundaries of space travel, with plans to travel for longer distances and durations than ever before. Both the National Aeronautics and Space Administration (NASA) and several commercial space companies (e.g., Blue Origin, SpaceX, Virgin Galactic) have already started the process of preparing for long-distance, long-duration space exploration and currently plan to explore inner solar planets (e.g., Mars) by the 2030s. With the emergence of space tourism, space travel has materialized as a potential new, exciting frontier of business, hospitality, medicine, and technology in the coming years. However, current evidence regarding human health in space is very limited, particularly pertaining to short-term and long-term space travel. This review synthesizes developments across the continuum of space health including prior studies and unpublished data from NASA related to each individual organ system, and medical screening prior to space travel. We categorized the extraterrestrial environment into exogenous (e.g., space radiation and microgravity) and endogenous processes (e.g., alteration of humans' natural circadian rhythm and mental health due to confinement, isolation, immobilization, and lack of social interaction) and their various effects on human health. The aim of this review is to explore the potential health challenges associated with space travel and how they may be overcome in order to enable new paradigms for space health, as well as the use of emerging Artificial Intelligence based (AI) technology to propel future space health research.
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Affiliation(s)
- Chayakrit Krittanawong
- Department of Medicine and Center for Space Medicine, Section of Cardiology, Baylor College of Medicine, Houston, TX 77030, USA
- Translational Research Institute for Space Health, Houston, TX 77030, USA
- Department of Cardiovascular Diseases, New York University School of Medicine, New York, NY 10016, USA
- Correspondence: or (C.K.); (B.E.C.); Tel.: +1-713-798-4951 (C.K.); +1-281-483-0123 (B.E.C.)
| | - Nitin Kumar Singh
- Biotechnology and Planetary Protection Group, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
| | | | - Emmanuel Urquieta
- Translational Research Institute for Space Health, Houston, TX 77030, USA
- Department of Emergency Medicine and Center for Space Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | - Eric M. Bershad
- Department of Neurology, Center for Space Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | | | - Scott Kaplin
- Department of Cardiovascular Diseases, New York University School of Medicine, New York, NY 10016, USA
| | - Carly Dunn
- Department of Dermatology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Stephen F. Kry
- Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | | | - Marc Shepanek
- Office of the Chief Health and Medical Officer, NASA, Washington, DC 20546, USA
| | | | - Andrew W. Kirkpatrick
- Department of Surgery and Critical Care Medicine, University of Calgary, Calgary, AB T2N 1N4, Canada
| | | | - Jean D. Sibonga
- Division of Biomedical Research and Environmental Sciences, NASA Lyndon B. Johnson Space Center, Houston, TX 77058, USA
| | - Andrew G. Lee
- Department of Ophthalmology, University of Texas Medical Branch School of Medicine, Galveston, TX 77555, USA
- Department of Ophthalmology, Blanton Eye Institute, Houston Methodist Hospital, Houston, TX 77030, USA
- Department of Ophthalmology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
- Department of Ophthalmology, Texas A and M College of Medicine, College Station, TX 77807, USA
- Department of Ophthalmology, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA
- Departments of Ophthalmology, Neurology, and Neurosurgery, Weill Cornell Medicine, New York, NY 10021, USA
| | - Brian E. Crucian
- National Aeronautics and Space Administration (NASA) Johnson Space Center, Human Health and Performance Directorate, Houston, TX 77058, USA
- Correspondence: or (C.K.); (B.E.C.); Tel.: +1-713-798-4951 (C.K.); +1-281-483-0123 (B.E.C.)
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Prisk GK. Pulmonary challenges of prolonged journeys to space: taking your lungs to the moon. Med J Aust 2019; 211:271-276. [PMID: 31420881 DOI: 10.5694/mja2.50312] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Space flight presents a set of physiological challenges to the space explorer which result from the absence of gravity (or in the case of planetary exploration, partial gravity), radiation exposure, isolation and a prolonged period in a confined environment, distance from Earth, the need to venture outside in the hostile environment of the destination, and numerous other factors. Gravity affects regional lung function, and the human lung shows considerable alteration in function in low gravity; however, this alteration does not result in deleterious changes that compromise lung function upon return to Earth. The decompression stress associated with extravehicular activity, or spacewalk, does not appear to compromise lung function, and future habitat (living quarter) designs can be engineered to minimise this stress. Dust exposure is a significant health hazard in occupational settings such as mining, and exposure to extraterrestrial dust is an almost inevitable consequence of planetary exploration. The combination of altered pulmonary deposition of extraterrestrial dust and the potential for the dust to be highly toxic likely makes dust exposure the greatest threat to the lung in planetary exploration.
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Affiliation(s)
- G Kim Prisk
- University of California, San Diego, La Jolla, CA, USA
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Prisk GK. Effects of Partial Gravity on the Function and Particle Handling of the Human Lung. CURRENT PATHOBIOLOGY REPORTS 2019; 6:159-166. [PMID: 30687585 DOI: 10.1007/s40139-018-0174-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Purpose of Review The challenges presented to the lung by the space environment are the effects of prolonged absence of gravity, the challenges of decompression stress associated with spacewalking, and the changes in the deposition of inhaled particulate matter. Recent Findings Although there are substantial changes in the function of the lung in partial gravity, the lung is largely unaffected by sustained exposure, returning rapidly to a normal state after return to 1G. Provided there is adequate denitrogenation prior to a spacewalk, avoiding the development of venous gas emboli, the lung copes well with the low pressure environment of the spacesuit. Particulate deposition is reduced in partial gravity, but where that deposition occurs is likely in the more peripheral airspaces, with associated longer retention times, potentially raising the toxicological potential of toxic dusts. Summary Despite its delicate structure the lung performs well in partial gravity, with the greatest threat likely arising from inhaled particulate matter (extra-terrestrial dusts).
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Affiliation(s)
- G Kim Prisk
- Department of Medicine, University of California, San Diego
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6
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Powell FL. Giants in Chest Medicine: John B. West, MD, PhD, DSc. Chest 2017; 152:10-12. [PMID: 28693761 DOI: 10.1016/j.chest.2016.12.037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 12/14/2016] [Indexed: 11/28/2022] Open
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Ade CJ, Broxterman RM, Moore AD, Barstow TJ. Decreases in maximal oxygen uptake following long-duration spaceflight: Role of convective and diffusive O 2 transport mechanisms. J Appl Physiol (1985) 2017; 122:968-975. [PMID: 28153941 DOI: 10.1152/japplphysiol.00280.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Revised: 12/19/2016] [Accepted: 01/19/2017] [Indexed: 01/22/2023] Open
Abstract
We have previously predicted that the decrease in maximal oxygen uptake (V̇o2max) that accompanies time in microgravity reflects decrements in both convective and diffusive O2 transport to the mitochondria of the contracting myocytes. The aim of this investigation was therefore to quantify the relative changes in convective O2 transport (Q̇o2) and O2 diffusing capacity (Do2) following long-duration spaceflight. In nine astronauts, resting hemoglobin concentration ([Hb]), V̇o2max, maximal cardiac output (Q̇Tmax), and differences in arterial and venous O2 contents ([Formula: see text]-[Formula: see text]) were obtained retrospectively for International Space Station Increments 19-33 (April 2009-November 2012). Q̇o2 and Do2 were calculated from these variables via integration of Fick's Principle of Mass Conservation and Fick's Law of Diffusion. V̇o2max significantly decreased from pre- to postflight (-53.9 ± 45.5%, P = 0.008). The significant decrease in Q̇Tmax (-7.8 ± 9.1%, P = 0.05), despite an unchanged [Hb], resulted in a significantly decreased Q̇o2 (-11.4 ± 10.5%, P = 0.02). Do2 significantly decreased from pre- to postflight by -27.5 ± 24.5% (P = 0.04), as did the peak [Formula: see text]-[Formula: see text] (-9.2 ± 7.5%, P = 0.007). With the use of linear regression analysis, changes in V̇o2max were significantly correlated with changes in Do2 (R2 = 0.47; P = 0.04). These data suggest that spaceflight decreases both convective and diffusive O2 transport. These results have practical implications for future long-duration space missions and highlight the need to resolve the specific mechanisms underlying these spaceflight-induced changes along the O2 transport pathway.NEW & NOTEWORTHY Long-duration spaceflight elicited a significant decrease in maximal oxygen uptake. Given the adverse physiological adaptations to microgravity along the O2 transport pathway that have been reported, an integrative approach to the determinants of postflight maximal oxygen uptake is needed. We demonstrate that both convective and diffusive oxygen transport are decreased following ~6 mo International Space Station missions.
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Affiliation(s)
- C J Ade
- Department of Health and Exercise Science, University of Oklahoma, Norman, Oklahoma; .,Department of Kinesiology, Kansas State University, Manhattan, Kansas
| | - R M Broxterman
- Department of Internal Medicine, University of Utah, Salt Lake City, Utah
| | - A D Moore
- Department of Health and Kinesiology, Lamar University, Beaumont, Texas; and
| | - T J Barstow
- Department of Kinesiology, Kansas State University, Manhattan, Kansas
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Ade CJ, Broxterman RM, Barstow TJ. VO(2max) and Microgravity Exposure: Convective versus Diffusive O(2) Transport. Med Sci Sports Exerc 2016; 47:1351-61. [PMID: 25380479 DOI: 10.1249/mss.0000000000000557] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Exposure to a microgravity environment decreases the maximal rate of O2 uptake (VO(2max)) in healthy individuals returning to a gravitational environment. The magnitude of this decrease in VO(2max) is, in part, dependent on the duration of microgravity exposure, such that long exposure may result in up to a 38% decrease in VO(2max). This review identifies the components within the O(2) transport pathway that determine the decrease in postmicrogravity VO(2max) and highlights the potential contributing physiological mechanisms. A retrospective analysis revealed that the decline in VO(2max) is initially mediated by a decrease in convective and diffusive O(2) transport that occurs as the duration of microgravity exposure is extended. Mechanistically, the attenuation of O(2) transport is the combined result of a deconditioning across multiple organ systems including decreases in total blood volume, red blood cell mass, cardiac function and mass, vascular function, skeletal muscle mass, and, potentially, capillary hemodynamics, which become evident during exercise upon re-exposure to the head-to-foot gravitational forces of upright posture on Earth. In summary, VO(2max) is determined by the integration of central and peripheral O(2) transport mechanisms, which, if not maintained during microgravity, will have a substantial long-term detrimental impact on space mission performance and astronaut health.
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Affiliation(s)
- Carl J Ade
- 1Department of Health and Exercise Science, University of Oklahoma, Norman, OK; 2Department of Kinesiology, Kansas State University, Manhattan, KS; and 3Department of Anatomy and Physiology, Kansas State University, Manhattan, KS
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West JB. Career perspective: John B West. EXTREME PHYSIOLOGY & MEDICINE 2012; 1:11. [PMID: 23849052 PMCID: PMC3710103 DOI: 10.1186/2046-7648-1-11] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2012] [Accepted: 08/08/2012] [Indexed: 11/15/2022]
Abstract
I have been fortunate to work in two areas of extreme physiology and medicine: very high altitude and the microgravity of spaceflight. My introduction to high altitude medicine was as a member of Sir Edmund Hillary's Silver Hut Expedition in 1960-1961 when a small group of physiologists spent the winter and spring at an altitude of 5,800 m just south of Mt. Everest. The physiological objective was to obtain a better understanding of the acclimatization process of lowlanders during exposure to a very high altitude for several months. As far as we knew, no one had ever spent so long at such a high altitude before. The success of this expedition prompted me to organize the 1981 American Medical Research Expedition to Everest where the scientific objective was to determine the physiological changes that allow humans to survive in the extreme hypoxia of the highest point on earth. There is good evidence that this altitude is very near the limit of human tolerance to oxygen deprivation. Much novel information was obtained including an extraordinary degree of hyperventilation which reduced the alveolar partial pressure of carbon dioxide (Pco2) to about 8 mmHg (1.1 kPa) on the summit, and this in turn allowed the alveolar partial pressure of oxygen, PO2, to be maintained at a viable level of about 35 mmHg (4.7 kPa). The low Pco2 caused a severe degree of respiratory alkalosis with an arterial pH exceeding 7.7. These were the first physiological measurements to be made on the Everest summit, and essentially, none has been made since. The second extreme environment is microgravity. We carried out an extensive series of measurements on astronauts in the orbiting laboratory known as SpaceLab in the 1990s. Many aspects of pulmonary function are affected by gravity, so it was not surprising that many changes were found. However, overall gas exchange remained efficient. Some of the findings such as an anomalous behavior of inhaled helium and sulfur hexafluoride have still not been explained. Measurements made after astronauts were exposed to 6 months of microgravity in the International Space Station indicate that the function of the lung returns to its preexposure state within a few days.
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Affiliation(s)
- John B West
- Department of Medicine 0623A, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0623, USA.
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Guo Y, Guo N, Liu C, Wang D, Wang J, Sun X, Fan S, Wang C, Yang C, Zhang Y, Lu D, Yao Y. Effect of artificial gravity with exercise training on lung function during head-down bed rest in humans. Clin Physiol Funct Imaging 2012; 33:24-9. [PMID: 23216762 DOI: 10.1111/j.1475-097x.2012.01155.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 07/02/2012] [Indexed: 11/28/2022]
Affiliation(s)
- Yinghua Guo
- Nanlou Respiratory Department; Chinese PLA General Hospital, Chinese PLA Medical College; Beijing; China
| | - Na Guo
- Nanlou Respiratory Department; Chinese PLA General Hospital, Chinese PLA Medical College; Beijing; China
| | - Changting Liu
- Nanlou Respiratory Department; Chinese PLA General Hospital, Chinese PLA Medical College; Beijing; China
| | - Delong Wang
- Nanlou Respiratory Department; Chinese PLA General Hospital, Chinese PLA Medical College; Beijing; China
| | - Junfeng Wang
- Nanlou Respiratory Department; Chinese PLA General Hospital, Chinese PLA Medical College; Beijing; China
| | - Xiqing Sun
- Department of Aerospace Biodynamics, Faculty of Aerospace Medicine; Fourth Military Medical University; Xi'an; China
| | - Shangchun Fan
- School of Instrumentation, Beijing University of Aeronautics and Astronautics; Beijing; China
| | - Changyong Wang
- Department of Tissue Engineering; Institute of Basic Medical Sciences and Tissue Engineering Research Center, Academy of Military Medical Sciences; Beijing; China
| | - Changbin Yang
- Department of Aerospace Biodynamics, Faculty of Aerospace Medicine; Fourth Military Medical University; Xi'an; China
| | - Yu Zhang
- Department of Aerospace Biodynamics, Faculty of Aerospace Medicine; Fourth Military Medical University; Xi'an; China
| | - Dongyuan Lu
- Department of Aerospace Biodynamics, Faculty of Aerospace Medicine; Fourth Military Medical University; Xi'an; China
| | - Yongjie Yao
- Department of Aerospace Biodynamics, Faculty of Aerospace Medicine; Fourth Military Medical University; Xi'an; China
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Hughson RL, Shoemaker JK, Blaber AP, Arbeille P, Greaves DK, Pereira-Junior PP, Xu D. Cardiovascular regulation during long-duration spaceflights to the International Space Station. J Appl Physiol (1985) 2012; 112:719-27. [DOI: 10.1152/japplphysiol.01196.2011] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Early evidence from long-duration flights indicates general cardiovascular deconditioning, including reduced arterial baroreflex gain. The current study investigated the spontaneous baroreflex and markers of cardiovascular control in six male astronauts living for 2–6 mo on the International Space Station. Measurements were made from the finger arterial pressure waves during spontaneous breathing (SB) in the supine posture pre- and postflight and during SB and paced breathing (PB, 0.1 Hz) in a seated posture pre- and postflight, as well as early and late in the missions. There were no changes in preflight measurements of heart rate (HR), blood pressure (BP), or spontaneous baroreflex compared with in-flight measurements. There were, however, increases in the estimate of left ventricular ejection time index and a late in-flight increase in cardiac output (CO). The high-frequency component of RR interval spectral power, arterial pulse pressure, and stroke volume were reduced in-flight. Postflight there was a small increase compared with preflight in HR (60.0 ± 9.4 vs. 54.9 ± 9.6 beats/min in the seated posture, P < 0.05) and CO (5.6 ± 0.8 vs. 5.0 ± 1.0 l/min, P < 0.01). Arterial baroreflex response slope was not changed during spaceflight, while a 34% reduction from preflight in baroreflex slope during postflight PB was significant (7.1 ± 2.4 vs. 13.4 ± 6.8 ms/mmHg), but a smaller average reduction (25%) during SB (8.0 ± 2.1 vs. 13.6 ± 7.4 ms/mmHg) was not significant. Overall, these data show no change in markers of cardiovascular stability during long-duration spaceflight and only relatively small changes postflight at rest in the seated position. The current program routine of countermeasures on the International Space Station provided sufficient stimulus to maintain cardiovascular stability under resting conditions during long-duration spaceflight.
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Affiliation(s)
- R. L. Hughson
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo,
| | - J. K. Shoemaker
- School of Kinesiology and Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario,
| | - A. P. Blaber
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada; and
| | - P. Arbeille
- Unite Medecine Physiologie Spatiale, CERCOM, EFMP CHU Trousseau, Tours, France
| | - D. K. Greaves
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo,
| | | | - D. Xu
- Faculty of Applied Health Sciences, University of Waterloo, Waterloo,
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