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Schmidt WFJ, Hoffmeister T, Wachsmuth NB, Byrnes WC. The effect of posture and exercise on blood CO kinetics during the optimized carbon monoxide rebreathing procedure. Scand J Clin Lab Invest 2023:1-8. [PMID: 37154842 DOI: 10.1080/00365513.2023.2204402] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
An indispensable precondition for the determination of hemoglobin mass (Hbmass) and blood volume by CO rebreathing is complete mixing of CO in the blood. The aim of this study was to demonstrate the kinetics of CO in capillary and venous blood in different body positions and during moderate exercise. Six young subjects (4 male, 2 female) performed three 2-min CO rebreathing tests in seated (SEA) & supine (SUP) positions as well as during moderate exercise (EX) on a bicycle ergometer. Before, during, and until 15 min after CO rebreathing cubital venous and capillary blood samples were collected simultaneously and COHb% was determined. COHb% kinetics were significantly slower in SEA than in SUP or EX. Identical COHb% in capillary and venous blood were reached in SEA after 5.0 ± 2.3 min, in SUP after 3.2 ± 1.3 min and in EX after 1.9 ± 1.2 min (EX vs. SEA p < .01, SUP vs. SEA p < .05). After 7th min, Hbmass did not differ between the resting positions (capillary: SEA 766 ± 217 g, SUP 761 ± 227 g; venous: SEA 759 ± 224 g, SUP 744 ± 207 g). Under exercise, however, a higher Hbmass (p < .05) was determined (capillary: 823 ± 221 g, venous: 804 ± 226 g). In blood, the CO mixing time in the supine position is significantly shorter than in the seated position. By the 6th minute complete mixing is achieved in either position giving similar Hbmass determinations. CO-rebreathing under exercise conditions, however, leads to ∼7% higher Hbmass values.
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Affiliation(s)
- Walter F J Schmidt
- Department of Sports Medicine/Sports Physiology, University of Bayreuth, Bayreuth, Germany
- Division of Exercise Physiology & Metabolism, University of Bayreuth, Bayreuth, Germany
| | - Torben Hoffmeister
- Department of Sports Medicine/Sports Physiology, University of Bayreuth, Bayreuth, Germany
| | - Nadine B Wachsmuth
- Division of Exercise Physiology & Metabolism, University of Bayreuth, Bayreuth, Germany
| | - William C Byrnes
- Department of Integrative Physiology, University of Colorado, Boulder, CO, USA
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2
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Lee SMC, Martin DS, Miller CA, Scott JM, Laurie SS, Macias BR, Mercaldo ND, Ploutz-Snyder L, Stenger MB. Venous and Arterial Responses to Partial Gravity. Front Physiol 2020; 11:863. [PMID: 32848835 PMCID: PMC7399573 DOI: 10.3389/fphys.2020.00863] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 06/26/2020] [Indexed: 01/25/2023] Open
Abstract
Introduction: Chronic exposure to the weightlessness-induced cephalad fluid shift is hypothesized to be a primary contributor to the development of spaceflight-associated neuro-ocular syndrome (SANS) and may be associated with an increased risk of venous thrombosis in the jugular vein. This study characterized the relationship between gravitational level (Gz-level) and acute vascular changes. Methods: Internal jugular vein (IJV) cross-sectional area, inferior vena cava (IVC) diameter, and common carotid artery (CCA) flow were measured using ultrasound in nine subjects (5F, 4M) while seated when exposed to 1.00-Gz, 0.75-Gz, 0.50-Gz, and 0.25-Gz during parabolic flight and while supine before flight (0-G analog). Additionally, IJV flow patterns were characterized. Results: IJV cross-sectional area progressively increased from 12 (95% CI: 9–16) mm2 during 1.00-Gz seated to 24 (13–35), 34 (21–46), 68 (40–97), and 103 (75–131) mm2 during 0.75-Gz, 0.50-Gz, and 0.25-Gz seated and 1.00-Gz supine, respectively. Also, IJV flow pattern shifted from the continuous forward flow observed during 1.00-Gz and 0.75-Gz seated to pulsatile flow during 0.50-Gz seated, 0.25-Gz seated, and 1.00-Gz supine. In contrast, we were unable to detect differences in IVC diameter measured during 1.00-G seated and any level of partial gravity or during 1.00-Gz supine. CCA blood flow during 1.00-G seated was significantly less than 0.75-Gz and 1.00-Gz supine but differences were not detected at partial gravity levels 0.50-Gz and 0.25-Gz. Conclusions: Acute exposure to decreasing Gz-levels is associated with an expansion of the IJV and flow patterns that become similar to those observed in supine subjects and in astronauts during spaceflight. These data suggest that Gz-levels greater than 0.50-Gz may be required to reduce the weightlessness-induced headward fluid shift that may contribute to the risks of SANS and venous thrombosis during spaceflight.
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Affiliation(s)
| | | | | | - Jessica M Scott
- Memorial Sloan Kettering Cancer Center, New York, NY, United States
| | | | | | | | - Lori Ploutz-Snyder
- School of Kinesiology, University of Michigan, Ann Arbor, MI, United States
| | - Michael B Stenger
- Lyndon B. Johnson Space Center, National Aeronautics and Space Administration, Houston, TX, United States
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Klein T, Sanders M, Wollseiffen P, Carnahan H, Abeln V, Askew CD, Claassen JA, Schneider S. Transient cerebral blood flow responses during microgravity. LIFE SCIENCES IN SPACE RESEARCH 2020; 25:66-71. [PMID: 32414494 DOI: 10.1016/j.lssr.2020.03.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 02/23/2020] [Accepted: 03/07/2020] [Indexed: 06/11/2023]
Abstract
PURPOSE A number of studies has well described central cardiovascular changes caused by changing gravity levels as they occur e.g. during parabolic flight. limited data exists describing the effect of microgravity on the cerebrovascular system and brain perfusion. METHODS In this study middle cerebral artery velocity (MCAv) of 16 participants was continuously monitored on a second-by-second basis during 15 consecutive parabolas (1G, 1,8G, 0G, 1,8G) using doppler ultrasound. Simultaneously central cardiovascular parameters (heart rate, mean arterial blood pressure, cardiac output) were assessed. RESULTS Results revealed an immediate reaction of central cardiovascular parameters to changed gravity levels. In contrast, changes in MCAv only initially were in accordance with a normal cerebral autoregulation. Whereas all of the measured central cardiovascular parameters seemed to have reached a steady state after approximately 8 s of microgravity, MCAv, after an initial decrease with the onset of microgravity, increased again during the second half of the microgravity phase. CONCLUSION It is concluded that this increase in MCAv during the second half of the microgravity period reflects a decrease of cerebrovascular resistance caused by a pressure driven increased venous outflow and/or a contraction of precapillary sphincters in order to avoid hyperperfusion of the brain.
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Affiliation(s)
- Timo Klein
- VasoActive Research Group, School of Health and Sport Sciences, University of the Sunshine Coast, Maroochydore DC, QLD, Australia; Institute of Movement and Neuroscience, German Sport University Cologne, Cologne, Germany
| | - Marit Sanders
- Department of Geriatric Medicine, Radboud Alzheimer Centre, Radboud University Medical Center, Donders Institute for Brain, Nijmegen, The Netherlands
| | - Petra Wollseiffen
- Institute of Movement and Neuroscience, German Sport University Cologne, Cologne, Germany
| | - Heather Carnahan
- Offshore Safety and Survival Centre, Marine Institute, Memorial University of Newfoundland, Canada
| | - Vera Abeln
- VasoActive Research Group, School of Health and Sport Sciences, University of the Sunshine Coast, Maroochydore DC, QLD, Australia
| | - Christopher D Askew
- VasoActive Research Group, School of Health and Sport Sciences, University of the Sunshine Coast, Maroochydore DC, QLD, Australia
| | - Jurgen Ahr Claassen
- Department of Geriatric Medicine, Radboud Alzheimer Centre, Radboud University Medical Center, Donders Institute for Brain, Nijmegen, The Netherlands
| | - Stefan Schneider
- VasoActive Research Group, School of Health and Sport Sciences, University of the Sunshine Coast, Maroochydore DC, QLD, Australia; Institute of Movement and Neuroscience, German Sport University Cologne, Cologne, Germany; Offshore Safety and Survival Centre, Marine Institute, Memorial University of Newfoundland, Canada.
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4
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Martin DS, Lee SMC, Matz TP, Westby CM, Scott JM, Stenger MB, Platts SH. Internal jugular pressure increases during parabolic flight. Physiol Rep 2017; 4:4/24/e13068. [PMID: 28039409 PMCID: PMC5210371 DOI: 10.14814/phy2.13068] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 10/31/2016] [Accepted: 11/03/2016] [Indexed: 11/24/2022] Open
Abstract
One hypothesized contributor to vision changes experienced by >75% of International Space Station astronauts is elevated intracranial pressure (ICP). While no definitive data yet exist, elevated ICP might be secondary to the microgravity-induced cephalad fluid shift, resulting in venous congestion (overfilling and distension) and inhibition of cerebrospinal and lymphatic fluid drainage from the skull. The objective of this study was to measure internal jugular venous pressure (IJVP) during normo- and hypo-gravity as an index of venous congestion. IJVP was measured noninvasively using compression sonography at rest during end-expiration in 11 normal, healthy subjects (3 M, 8 F) during normal gravity (1G; supine) and weightlessness (0G; seated) produced by parabolic flight. IJVP also was measured in two subjects during parabolas approximating Lunar (1/6G) and Martian gravity (1/3G). Finally, IJVP was measured during increased intrathoracic pressure produced using controlled Valsalva maneuvers. IJVP was higher in 0G than 1G (23.9 ± 5.6 vs. 9.9 ± 5.1 mmHg, mean ± SD P < 0.001) in all subjects, and IJVP increased as gravity levels decreased in two subjects. Finally, IJVP was greater in 0G than 1G at all expiration pressures (P < 0.01). Taken together, these data suggest that IJVP is elevated during acute exposure to reduced gravity and may be elevated further by conditions that increase intrathoracic pressure, a strong modulator of central venous pressure and IJVP However, whether elevated IJVP, and perhaps consequent venous congestion, observed during acute microgravity exposure contribute to vision changes during long-duration spaceflight is yet to be determined.
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Affiliation(s)
- David S Martin
- KBRwyle Science, Technology & Engineering Group, Houston, Texas
| | - Stuart M C Lee
- KBRwyle Science, Technology & Engineering Group, Houston, Texas
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Abstract
Ground-based analog facilities have had wide use in mimicking some of the features of spaceflight in a more-controlled and less-expensive manner. One such analog is parabolic flight, in which an aircraft flies repeated parabolic trajectories that provide short-duration periods of free fall (0 g) alternating with high-g pullout or recovery phases. Parabolic flight is unique in being able to provide true 0 g in a ground-based facility. Accordingly, it lends itself well to the investigation of specific areas of human spaceflight that can benefit from this capability, which predominantly includes neurovestibular effects, but also others such as human factors, locomotion, and medical procedures. Applications to research in artificial gravity and to effects likely to occur in upcoming commercial suborbital flights are also possible.
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Affiliation(s)
- Mark Shelhamer
- Department of Otolaryngology-Head and Neck, Department of Surgery, Johns Hopkins University. School of Medicine, Baltimore, Maryland
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Petersen LG, Damgaard M, Petersen JCG, Norsk P. Mechanisms of increase in cardiac output during acute weightlessness in humans. J Appl Physiol (1985) 2011; 111:407-11. [PMID: 21636570 DOI: 10.1152/japplphysiol.01188.2010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Based on previous water immersion results, we tested the hypothesis that the acute 0-G-induced increase in cardiac output (CO) is primarily caused by redistribution of blood from the vasculature above the legs to the cardiopulmonary circulation. In seated subjects (n = 8), 20 s of 0 G induced by parabolic flight increased CO by 1.7 ± 0.4 l/min (P < 0.001). This increase was diminished to 0.8 ± 0.4 l/min (P = 0.028), when venous return from the legs was prevented by bilateral venous thigh-cuff inflation (CI) of 60 mmHg. Because the increase in stroke volume during 0 G was unaffected by CI, the lesser increase in CO during 0 G + CI was entirely caused by a lower heart rate (HR). Thus blood from vascular beds above the legs in seated subjects can alone account for some 50% of the increase in CO during acute 0 G. The remaining increase in CO is caused by a higher HR, of which the origin of blood is unresolved. In supine subjects, CO increased from 7.1 ± 0.7 to 7.9 ± 0.8 l/min (P = 0.037) when entering 0 G, which was solely caused by an increase in HR, because stroke volume was unaffected. In conclusion, blood originating from vascular beds above the legs can alone account for one-half of the increase in CO during acute 0 G in seated humans. A Bainbridge-like reflex could be the mechanism for the HR-induced increase in CO during 0 G in particular in supine subjects.
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Affiliation(s)
- Lonnie G Petersen
- Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen, Denmark.
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7
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Beat-to-beat agreement of noninvasive tonometric and intra-radial arterial blood pressure during microgravity and hypergravity generated by parabolic flights. Blood Press Monit 2007; 12:357-62. [DOI: 10.1097/01.mbp.0000209088.78235.59] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Verheyden B, Beckers F, Aubert AE. Spectral characteristics of heart rate fluctuations during parabolic flight. Eur J Appl Physiol 2005; 95:557-68. [PMID: 16235070 DOI: 10.1007/s00421-005-0016-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2005] [Indexed: 10/25/2022]
Abstract
Parabolic flight is used to create short successive periods of changing gravity in a range between 0 and 1.8 Gz (1 Gz: 9.81 m/s(2)). The purpose of the present study was to evaluate whether cyclic variations in heart rate during +/-20 s periods of stable gravity in parabolic flight reflect autonomic modulation of cardiac chronotropy. During the 29th and 32nd ESA parabolic flight campaign ECG and respiration were recorded in 13 healthy volunteers in both standing and supine postures. We developed and validated a spectral algorithm especially adapted to study frequency components of heart rate among ultrashort (+/-20 s) stable gravity periods of parabolic flight. A low frequency (LF) component, starting from the lowest measurable frequency (+/-0.05 Hz) up to 0.15 Hz was distinguished from a high frequency (HF) component, ranging from 0.16 Hz up to 0.4 Hz. Powers were calculated by integration between corresponding limits and represented in normalized units (nu). With our method, we were able to reproduce normal findings in the upright posture at 1 Gz, i.e., less power in the HF component compared to supine (HFnu: 0.18+/-0.09 vs. 0.40+/-0.16). These postural related differences are shown to be eliminated at 0 Gz (HFnu: 0.30+/-0.12 vs. 0.32+/-0.13) and amplified at 1.8 Gz phases (HFnu: 0.15+/-0.10 vs. 0.39+/-0.16) of parabolic flight. In the supine position no coherent differences were shown in the measured variables among different gravity phases. Our observations strongly indicate that spectral characteristics of heart rate fluctuations among stable gravity periods of parabolic flight reflect parasympathetic nervous system control of cardiac chronotropy. At 1 Gz, there is a normal upright situation with less parasympathetic modulation of heart rate compared to supine. This effect is augmented during 1.8 Gz-conditions due to a suppressed parasympathetic control of heart rate in the upright posture. Alternatively, at 0 Gz, increased parasympathetic control in standing position eliminates differences in cardiac chronotropy compared to supine.
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Affiliation(s)
- Bart Verheyden
- Laboratory of Experimental Cardiology, Department of Molecular and Cardiovascular Research, University Hospital Gasthuisberg, Herestraat 49, 3000, Leuven, Belgium
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Bonnin P, Bailliart O, Kedra AW. Notions d’hémodynamique et techniques ultrasonores pour l’exploration des veines du cou et des membres. ACTA ACUST UNITED AC 2005; 86:629-37. [PMID: 16142026 DOI: 10.1016/s0221-0363(05)81418-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Deep venous thrombosis and venous insufficiency are now easily diagnosed with US imaging. US allows anatomic evaluation of the vessel walls and dynamic evaluation of flow velocities. Knowledge of vascular anatomy and physiology is required to interpret US data. The sensitivity of US for the diagnosis of deep venous thrombosis is up to 95% at the leg level, 98% at the popliteal level, and 100% at the femoral level with a specificity of nearly 100%. Venography is thus rarely performed. The sensitivity for the diagnosis of deep venous thrombosis at the neck level is up to 90%. Follow-up can easily be performed because of the wide availability of US.
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Affiliation(s)
- Ph Bonnin
- Service de Physiologie, Explorations Fonctionnelles, Pr B. Levy, Hôpital Lariboisière, 2 rue A Paré, 75 475 Paris Cedex 10.
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10
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Montmerle S, Linnarsson D. Effects of gravity and blood volume shifts on cardiogenic oscillations in respired gas. J Appl Physiol (1985) 2005; 99:931-6. [PMID: 15845775 DOI: 10.1152/japplphysiol.00252.2005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
During the cardiac cycle, cardiogenic oscillations of expired gas (x) concentrations (COS([x])) are generated. At the same time, there are heart-synchronous cardiogenic oscillations of airway flow (COS(flow)), where inflow occurs during systole. We hypothesized that both phenomena, although primarily generated by the heartbeat, would react differently to the cephalad blood shift caused by inflation of an anti-gravity (anti-G) suit and to changes in gravity. Twelve seated subjects performed a rebreathing-breath-holding-expiration maneuver with a gas mixture containing O2 and He at normal (1 G) and moderately increased gravity (2 G); an anti-G suit was inflated to 85 mmHg in each condition. When the anti-G suit was inflated, COS(flow) amplitude increased (P = 0.0028) at 1 G to 186% of the control value without inflation (1-G control) and at 2 G to 203% of the control value without inflation (2-G control). In contrast, the amplitude of COS of the concentration of the blood-soluble gas O2 (COS([O2/He])), an index of the differences in pulmonary perfusion between lung units, declined to 75% of the 1-G control value and to 74% of the 2-G control value (P = 0.0030). There were no significant changes in COS(flow) or COS([O2/He]) amplitudes with gravity. We conclude that the heart-synchronous mechanical agitation of the lungs, as expressed by COS(flow), is highly dependent on peripheral-to-central blood shifts. In contrast, COS([blood-soluble gas]) appears relatively independent of this mechanical agitation and seems to be determined mainly by differences in intrapulmonary perfusion.
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Affiliation(s)
- Stéphanie Montmerle
- Sect. of Environmental Physiology, Dept. of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
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11
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Etard O, Reber A, Quarck G, Normand H, Mulder P, Denise P. Vestibular control on blood pressure during parabolic flights in awake rats. Neuroreport 2005; 15:2357-60. [PMID: 15640755 DOI: 10.1097/00001756-200410250-00011] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The aim of this study was to evaluate the role of the vestibular system in cardiovascular control in a varying gravito-inertial field induced by parabolic flight. We measured variations in arterial pressure and heart rate in eight awake rats, four of which had undergone bilateral labyrinthectomy 3 months previously. While the control rats showed heart rate and mean arterial pressure modulations depending on gravity level, no such variation was observed in the lesioned rats. This study confirms the role of the vestibular system in cardiovascular control and opens up new prospects for interpreting cardiovascular variations observed during space flights.
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Affiliation(s)
- Olivier Etard
- Laboratoire de Physiologie, UFR de Médecine, 14032 Caen Cedex 1Laboratoire de Neurosciences et Environnement, EA 2122 UFR Sciences, 76821 Mont-Saint-Aignan, France
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12
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Pletser V. Short duration microgravity experiments in physical and life sciences during parabolic flights: the first 30 ESA campaigns. ACTA ASTRONAUTICA 2004; 55:829-54. [PMID: 15806734 DOI: 10.1016/j.actaastro.2004.04.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Aircraft parabolic flights provide repetitively up to 20 s of reduced gravity during ballistic flight manoeuvres. Parabolic flights are used to conduct short microgravity investigations in Physical and Life Sciences, to test instrumentation and to train astronauts before a space flight. The European Space Agency (ESA) has organized since 1984 thirty parabolic flight campaigns for microgravity research experiments utilizing six different airplanes. More than 360 experiments were successfully conducted during more than 2800 parabolas, representing a cumulated weightlessness time of 15 h 30 m. This paper presents the short duration microgravity research programme of ESA. The experiments conducted during these campaigns are summarized, and the different airplanes used by ESA are shortly presented. The technical capabilities of the Airbus A300 'Zero-G' are addressed. Some Physical Science, Technology and Life Science experiments performed during the last ESA campaigns with the Airbus A300 are presented to show the interest of this unique microgravity research tool to complement, support and prepare orbital microgravity investigations.
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Affiliation(s)
- Vladimir Pletser
- Microgravity Projects Division, Manned Spaceflight and Microgravity Directorate, European Space Research and Technology Centre (ESTEC), Noordwijk, The Netherlands.
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Corsi C, Lamberti C, Cerutti S, Laulom JP, Bailliart O, Cholley B, Capderou A, Vaida P, Caiani EG. Quantification of left ventricular modification in weightlessness conditions from the spatio-temporal analysis of 2D echocardiographic images. Med Biol Eng Comput 2004; 42:610-7. [PMID: 15503961 DOI: 10.1007/bf02347542] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Two-dimensional echocardiography (2DE) performed during flights with a parabolic trajectory to simulate weightlessness provides a unique means to study left ventricular (LV) modifications to prevent post-flight orthostatic intolerance in astronauts. However, conventional analysis of 2DE is based on manual tracings and depends on experience. Accordingly, the aim was objectively to quantify, from 2DE images, the LV modifications related to different gravity levels, by applying a semi-automated level-set border detection technique. The algorithm validation was performed by the comparison of manual tracing results, obtained by two independent observers with 20 images, with the semi-automated measurements. To quantify LV modifications, three consecutive cardiac cycles were analysed for each gravity phase (1 Gz, 1.8 Gz, 0 Gz). The level-set procedure was applied frame-by-frame to detect the LV endocardial contours and obtain LV area against time curves, from which end-diastolic (EDA) and end-systolic (ESA) areas were computed and averaged to compensate for respiratory variations. Linear regression (y = 0.91x + 1.47, r = 0.99, SEE:0.80cm2) and Bland-Altman analysis (bias = -0.58 cm2, 95% limits of agreement= +/- 2.14cm2) showed excellent correlation between the semi-automatic and manually traced values. Inter-observer variability was 5.4%, and the inter-technique variability was 4.1%. Modifications in LV dimensions during the parabola were found: compared with 1 Gz values, EDA and ESA were significantly reduced at 1.8 Gz by 8.8 +/- 5.5% and 12.1 +/- 10.1%, respectively, whereas, during 0 Gz, EDA and ESA increased by 13.3 +/- 7.3% and 11.6 +/- 5.1%, respectively, owing to abrupt changes in venous return. The proposed method resulted in fast and reliable estimations of LV dimensions, whose changes caused by different gravity conditions were objectively quantified.
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Affiliation(s)
- C Corsi
- DEIS, Università di Bologna, Bologna, Italy.
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14
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Saltykova M, Capderou A, Atkov O, Gusakov V, Konovalov G, Voronin L, Kaspranskiy R, Morgun V, Bailliart O, Cermack M, Vaïda P. Variations of intrathoracic amount of blood as a reason of ECG voltage changes. Ann Noninvasive Electrocardiol 2004; 8:321-32. [PMID: 14516289 PMCID: PMC7313230 DOI: 10.1046/j.1542-474x.2003.08410.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND It is known that electroconduction of intrathoracic organs and tissues significantly influences the ECG voltage. It changes during therapy or exercise test due to redistribution and/or volume variations of blood and body fluids and their electroconductivity variations. This fact must be taken into consideration during interpretation of corresponding ECG. But there are no quantitative estimations of this influence on human ECG. The goals of this study were to estimate the influence of variations of thoracic electroconduction, and heart volume on QRS voltage in humans, due to gravity change. METHODS ECGs of 26 healthy volunteers were analyzed in upright and supine position. Experimental conditions-acute change of gravity--are created in a special aircraft flying on Kepler's parabola trajectory. Each parabola includes phases of normo-, hypergravity (blood shifts in caudal direction), and microgravity (blood redistributes in cranial direction). Amplitude of QRS in Frank leads in all phases has been analyzed. 2-D echo studies for six subjects were used for estimation of heart volume change. RESULTS In an upright position during hypergravity the amplitude of R wave in Z increases in 95% of cases (mean 0.19 mV). During microgravity amplitude of R wave in Z decreases in 95% (mean 0.24 mV). In supine position changes of QRS voltage are not significantly. CONCLUSION Blood redistribution during gravity change leads to changes of QRS voltage, which is more expressed and steady on R in Z lead: an average near 0.2 mV. It is due to the balance between two factors: (a). changes of degree of short circuiting by variations in the amount of blood in thorax (b). changes of distance between heart and electrodes as a result of change in the position, form, and volume of the heart.
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Yamauchi K, Tsutsui Y, Endo Y, Sagawa S, Yamazaki F, Shiraki K. Sympathetic nervous and hemodynamic responses to lower body negative pressure in hyperbaria in men. Am J Physiol Regul Integr Comp Physiol 2002; 282:R38-45. [PMID: 11742821 DOI: 10.1152/ajpregu.2002.282.1.r38] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The present study was designed to test the hypothesis that sympathetic nerve activity is attenuated in a hyperbaric environment. Response of muscle sympathetic nerve activity (MSNA) to central circulatory hypovolemic stress, lower body negative pressure (LBNP), was measured in nine men at normal and at 3 atm pressures. The stress consisted of 4 min each of control and LBNP at -20 and -40 mmHg. In addition to MSNA, heart rate, stroke volume (SV), forearm blood flow (FBF), and volume of the lower leg were recorded. A reduction of baseline HR occurred with increased forearm vascular resistance at 3 atm abs. The baseline MSNA decreased during hyperbaria. MSNA increased progressively with increasing LBNP in both atmospheric pressures, and the change from the baseline (DeltaMSNA) was similar in both conditions. Changes in SV, FBF, and volume of the lower legs in response to LBNP were not statistically different during exposure to 2 atm pressures. The present study suggests that hyperbaria attenuates sympathetic nerve activity; however, its responsiveness to hypovolemic stress was not affected by hyperbaric exposure.
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Affiliation(s)
- Katsuya Yamauchi
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan
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Montmerle S, Spaak J, Linnarsson D. Lung function during and after prolonged head-down bed rest. J Appl Physiol (1985) 2002; 92:75-83. [PMID: 11744645 DOI: 10.1152/jappl.2002.92.1.75] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We determined the effects of prolonged head-down tilt bed rest (HDT) on lung mechanics and gas exchange. Six subjects were studied in supine and upright postures before (control), during [day 113 (D113)], and after (R + number of days of recovery) 120 days of HDT. Peak expiratory flow (PF) never differed between positions at any time and never differed from controls. Maximal midexpiratory flow (FEF(25-75%)) was lower in the supine than in the upright posture before HDT and was reduced in the supine posture by about 20% between baseline and D113, R + 0, and R + 3. The diffusing capacity for carbon monoxide corrected to a standardized alveolar volume (volume-corrected DL(CO)) was lower in the upright than in the supine posture and decreased in both postures by 20% between baseline and R + 0 and by 15% between baseline and R + 15. Pulmonary blood flow (Q(C)) increased from R + 0 to R + 3 by 20 (supine) and 35% (upright). As PF is mostly effort dependent, our data speak against major respiratory muscle deconditioning after 120 days of HDT. The decrease in FEF(25-75%) suggests a reduction in elastic recoil. Time courses of volume-corrected DL(CO) and Q(C) could be explained by a decrease in central blood volume during and immediately after HDT.
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Affiliation(s)
- Stéphanie Montmerle
- Section of Environmental Physiology, Department of Physiology and Pharmacology, Karolinska Institutet, SE-171 77 Stockholm, Sweden.
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Glenny RW, Lamm WJ, Bernard SL, An D, Chornuk M, Pool SL, Wagner WW, Hlastala MP, Robertson HT. Selected contribution: redistribution of pulmonary perfusion during weightlessness and increased gravity. J Appl Physiol (1985) 2000; 89:1239-48. [PMID: 10956375 DOI: 10.1152/jappl.2000.89.3.1239] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To compare the relative contributions of gravity and vascular structure to the distribution of pulmonary blood flow, we flew with pigs on the National Aeronautics and Space Administration KC-135 aircraft. A series of parabolas created alternating weightlessness and 1.8-G conditions. Fluorescent microspheres of varying colors were injected into the pulmonary circulation to mark regional blood flow during different postural and gravitational conditions. The lungs were subsequently removed, air dried, and sectioned into approximately 2 cm(3) pieces. Flow to each piece was determined for the different conditions. Perfusion heterogeneity did not change significantly during weightlessness compared with normal and increased gravitational forces. Regional blood flow to each lung piece changed little despite alterations in posture and gravitational forces. With the use of multiple stepwise linear regression, the contributions of gravity and vascular structure to regional perfusion were separated. We conclude that both gravity and the geometry of the pulmonary vascular tree influence regional pulmonary blood flow. However, the structure of the vascular tree is the primary determinant of regional perfusion in these animals.
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Affiliation(s)
- R W Glenny
- Department of Medicine, University of Washington School of Medicine, Seattle, Washington 98195, USA.
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Morita H, Fujiki N, Hagiike M, Tsuchiya Y, Miyahara T, Tanaka K. Acute responses of renal nerve activity to microgravity induced by free drop in anesthetized rats. Neurosci Res 2000; 37:221-6. [PMID: 10940456 DOI: 10.1016/s0168-0102(00)00123-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
To examine acute cardiovascular and autonomic responses to microgravity (microG), arterial pressure (AP), aortic flow velocity (AFV), central venous pressure (CVP), and renal nerve activity (RNA) were measured in anesthetized rats during 4.5 s of microG produced by free drop. A smooth and immediate reduction in gravity occurred during free drop, microG being achieved 100 ms after the start of the drop. Acute microG elicited an immediate and striking, but transient, decrease in RNA with no significant change in AP and AFV, but a significant decrease in CVP. The decrease in RNA lasted 2 s, then RNA recovered to the control level despite the G value remaining at < 0.001 for 4.5 s. The RNA decrease was attenuated or completely abolished by sinoaortic denervation, vagotomy, or sinoaortic denervation plus vagotomy. These results suggest that acute microG conditions stimulate sinoaortic and cardiopulmonary mechanoreceptors and suppress RNA.
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Affiliation(s)
- H Morita
- Department of Physiology, Gifu University School of Medicine, Japan.
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