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  • 151.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Prisk, G. Kim
    Something from nothing?: Space research without leaving the planet2016In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 120, no 8, p. 889-890Article in journal (Other academic)
  • 152.
    Sundblad, Patrik
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. Department of Physiology and Pharmacology, Karolinska Institutet, Sweden .
    Spaak, J.
    Kaijser, L.
    Time courses of central hemodynamics during rapid changes in posture.2014In: Journal of applied physiology, ISSN 8750-7587, E-ISSN 1522-1601, Vol. 116, no 9, p. 1182-1188Article in journal (Refereed)
    Abstract [en]

    Changes in posture cause blood volume redistribution, affecting cardiac filling and stroke volume (SV). We hypothesized that the time courses of ventricular filling would differ between the right and left ventricle during a rapid (2 s) tilt and that changes in right ventricular filling pressure would be more swift because of the direct coupling to the systemic circulation. We further hypothesized that the transient imbalance between right and left ventricular filling pressure would influence left ventricular SV changes. Right atrial pressure (RAP), pulmonary capillary wedge pressure (PCWP), left ventricular stroke volume, heart rate, and arterial pressure were recorded beat-by-beat during rapid tilts from supine to upright positions and back again, during rest and dynamic 100-W leg exercise. RAP changes had a faster time course than PCWP during down-tilts, both during rest and exercise (1 +/- 1 vs. 6 +/- 2 s and 2 +/- 2 vs. 6 +/- 2 s, respectively; P < 0.05). This discrepancy caused a transient decrease in the end-diastolic pressure difference between the right and left ventricle. The decreased pressure difference in diastole impeded left ventricular filling because of ventricular interdependence, causing SV to fall transiently. The mechanisms of ventricular interdependence were also involved in reverse during up-tilt, where SV was maintained for 2-3 s despite falling PCWP. Furthermore, the decrease in RAP during up-tilt in the resting condition was biphasic with an initial fast and a second slower component, which might suggest the effect of venous valves. This was not seen during dynamic leg exercise where blood pooling is prevented by the venous muscle pump.

  • 153. Tellez, Helio Fernandez
    et al.
    Morrison, Shawnda A.
    Neyt, Xavier
    Mairesse, Olivier
    Piacentini, Maria Francesca
    Macdonald-Nethercott, Eoin
    Pangerc, Andrej
    Dolenc-Groselj, Leja
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Pattyn, Nathalie
    Mekjavic, Igor B.
    Meeusen, Romain
    Exercise during Short-Term and Long-Term Continuous Exposure to Hypoxia Exacerbates Sleep-Related Periodic Breathing2016In: Sleep, ISSN 0161-8105, E-ISSN 1550-9109, Vol. 39, no 4, p. 773-783Article in journal (Refereed)
    Abstract [en]

    Study Objectives: Exposure to hypoxia elevates chemosensitivity, which can lead to periodic breathing. Exercise impacts gas exchange, altering chemosensitivity; however, interactions between sleep, exercise and chronic hypoxic exposure have not been examined. This study investigated whether exercise exacerbates sleep-related periodic breathing in hypoxia. Methods: Two experimental phases. Short-Term Phase: a laboratory controlled, group-design study in which 16 active, healthy men (age: 25 +/- 3 y, height: 1.79 +/- 0.06 m, mass: 74 +/- 8 kg) were confined to a normobaric hypoxic environment (FIO2 = 0.139 +/- 0.003, 4,000 m) for 10 days, after random assignment to a sedentary (control, CON) or cycle-exercise group (EX). Long-Term Phase: conducted at the Concordia Antarctic Research Station (3,800 m equivalent at the Equator) where 14 men (age: 36 +/- 9 y, height: 1.77 +/- 0.09 m, mass: 75 +/- 10 kg) lived for 12-14 months, continuously confined. Participants were stratified post hoc based on self-reported physical activity levels. We quantified apnea-hypopnea index (AHI) and physical activity variables. Results: Short-Term Phase: mean AHI scores were significantly elevated in the EX group compared to CON (Night1 = CON: 39 +/- 51, EX: 91 +/- 59; Night10 = CON: 32 +/- 32, EX: 92 +/- 48; P = 0.046). Long-Term Phase: AHI was correlated to mean exercise time (R-2 = 0.4857; P = 0.008) and the coefficient of variation in night oxyhemoglobin saturation (SpO(2); R-2 = 0.3062; P = 0.049). Conclusions: Data indicate that exercise (physical activity) per se affects night SpO(2) concentrations and AHI after a minimum of two bouts of moderateintensity hypoxic exercise, while habitual physical activity in hypobaric hypoxic confinement affects breathing during sleep, up to 13+ months' duration

  • 154. Tellez, HF
    et al.
    Morrison, SA
    Neyt, X
    Meeusen, R
    Francesca Piacentini, M
    Pangerc, A
    Dolenc-Groselj, L
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, IB
    Pattyn, N
    Exercise during acute and long-term continuous exposure to hypoxia exacerbates sleep-related periodic breathing2015Article in journal (Refereed)
  • 155. Tellez, H.F.
    et al.
    Pattyn, N.
    Mairesse, O.
    Dolenc-Groselj, L.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, I.B.
    Migeotte, P.F.
    Macdonald-Nethercott, E.
    Meeusen, R.
    Neyt, X.
    eAMI: A Qualitative Quantification of Periodic Breathing Based on Amplitude of Oscillations2015In: Sleep, ISSN 0161-8105, E-ISSN 1550-9109, Vol. 38, no 3, p. 381-389Article in journal (Refereed)
    Abstract [en]

    Study Objectives:

    Periodic breathing is sleep disordered breathing characterized by instability in the respiratory pattern that exhibits an oscillatory behavior. Periodic breathing is associated with increased mortality, and it is observed in a variety of situations, such as acute hypoxia, chronic heart failure, and damage to respiratory centers. The standard quantification for the diagnosis of sleep related breathing disorders is the apnea-hypopnea index (AHI), which measures the proportion of apneic/ hypopneic events during polysomnography. Determining the AHI is labor-intensive and requires the simultaneous recording of airflow and oxygen saturation. In this paper, we propose an automated, simple, and novel methodology for the detection and qualification of periodic breathing: the estimated amplitude modulation index (eAMI).

    Patients or Participants:

    Antarctic Cohort (3800 meters): 13 normal individuals. Sleep Clinic Cohort: 39 different patients suffering from diverse sleep-related pathologies.

    Measurements and Results:

    When tested in a population with high levels of periodic breathing (Antarctic Cohort), eAMI was closely correlated with AHI (r = 0.95, P < 0.001). When tested in the clinical setting, the proposed method was able to detect portions of the signal in which subclinical periodic breathing was validated by an expert (n = 93; accuracy = 0.85). Average eAMI was also correlated with the loop gain for the combined clinical and Antarctica cohorts (r = 0.58, P < 0.001).

    Conclusions:

    In terms of quantification and temporal resolution, the eAMI is able to estimate the strength of periodic breathing and the underlying loop gain at any given time within a record. The impaired prognosis associated with periodic breathing makes its automated detection and early diagnosis of clinical relevance.

  • 156.
    Tribukait, Arne
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    The ability of pilots and non-pilots to perceive angular displacements in centrifuge and helicopter2013In: Proceedings from the Italian Association of Aviation and Space Medicine , XXVI National Meeting, Vatikanstaten 11-14 sep., 2013Conference paper (Refereed)
  • 157.
    Tribukait, Arne
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Visual indicators in the study of spatial orientation in a gondola centrifuge2013In: Italian Journal of Aerospace Medicine, ISSN 2279-8994, Vol. 9, p. 56-69Article in journal (Refereed)
  • 158.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Individual characteristics in the perception of roll tilt during a simulated coordinated turn2013Conference paper (Refereed)
  • 159.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Individuella särdrag i spatial orienteringsförmåga vid en simulerad koordinerad sväng i gondolcentrifug/dfs2013In: Hygiea, 2013Conference paper (Refereed)
    Abstract [sv]

    Individuella särdrag i spatial orienteringsförmåga vid en simulerad koordinerad sväng i gondolcentrifug. Stora skillnader i skattningen av roll-position, dessa var ej slumpmässiga.

  • 160.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Möjligheterna att i dynamisk flygsimulator (DFS) återskapa rörelsemönster som vid flygning är grundläggande. 2. Positionsändring vid hovring2014Conference paper (Refereed)
  • 161.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Pitch-Plane Angular Displacement Perception During Helicopter Flight and Gondola Centrifugation2016In: Aerospace Medicine and Human Performance, ISSN 2375-6314, Vol. 87, no 10, p. 852-861Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: During hovering with a helicopter, an involuntary change in attitude (during brownout) results in reduced lifting force and a horizontal acceleration component. This movement pattern is difficult to perceive via the otolith organs. If the angular displacement occurs rapidly, it will, however, activate the semicircular canals. The major aim of this study was to establish to what extent pitch-plane angular displacements can be perceived based on canal information when there is no tilt stimulus to the otoliths. METHODS: In a helicopter, 9 nonpilots (N) and 8 helicopter pilots (P) underwent 5-6 pitch-forward displacements (magnitude 14-33 degrees, angular velocity 2-7 degrees. s(-1)). In a swing-out gondola centrifuge, 9 N and 3 P were exposed to a similar canal-otolith conflict (acceleration, seated centripetally) with four displacements of 25 degrees and two of 60 degrees. The visually perceived eye level (VPEL) was continuously recorded using an adjustable luminous dot in darkness. For each helicopter dive and centrifuge run the gain was calculated as the ratio (VPEL deflection)/(displacement of helicopter or gondola). RESULTS: In the helicopter there was no difference between N (0.28 +/- 0.13) and P (0.36 +/- 0.22). In the centrifuge the gains were 0.34 +/- 0.18 degrees (25 degrees displacements) and 0.30 +/- 0.16 degrees (60 degrees displacements). Values obtained in the helicopter did not differ significantly from those in the centrifuge. There was a correlation between data obtained during the 25 degrees and 60 degrees displacements in the centrifuge. CONCLUSION: There was a pronounced underestimation of pitch angular displacements in a helicopter. The interindividual variability was considerable. Gains for perceived displacement were similar in helicopter and centrifuge.

  • 162.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Variability in Perceived Tilt During a Roll Plane Canal-Otolith Conflict in a Gondola Centrifuge2013In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 84, no 11, p. 1131-1139Article in journal (Refereed)
    Abstract [en]

    Background: During a simulated coordinated turn in a gondola centrifuge, the perceived roll-tilt, quantified as the subjective visual horizontal (SVH), may differ tenfold between individuals. One aim of this study was to discern whether this variability reflects real individual characteristics or is due to noise or day-to-day variation. We also wanted to establish whether there are any habituation or learning effects of the centrifuge test. Methods: In nine nonpilots (NP) and nine student pilots (SP), with a flight experience of 150 h, the SVH was measured using an adjustable luminous line in darkness. At two test occasions (T1, T2) (interval 5-14 d) subjects underwent two runs (R1, R2; acceleration to 2 G in 10 s, gondola inclination 60 degrees, 5 min at 2 G, deceleration to 1 g in 10 s, interval between runs 5 min) in a centrifuge (r = 9.1 m). Initial and final SVH was determined for each individual run. Results: Acceleration of the centrifuge induced a tilt of the SVH. At T1R1, this SVH tilt was, in NP, initially 24 +/- 18 degrees and finally 8 +/- 10 degrees. The corresponding values for SP were 28 +/- 18 degrees and 31 +/- 33 degrees. The SVH tilt was slightly larger at R2 than at R1. There was no difference between T1 and T2. Reliability coefficients ranged between 0.86 and 0.98 for NP and between 0.78 and 0.99 for SR. Conclusion: The large interindividual variability combined with a very high reproducibility suggests the existence of persistent individual characteristics in the perception of complex vestibular stimuli. Habituation or learning effects of gondola centrifugation appears to be small.

  • 163.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Bergsten, Eddie
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Brink, Andreas
    Möjligheterna att i dynamisk flygsimulator (DFS) återskapa rörelsemönster som vid flygning är grundläggande. 1. Koordinerad kurvtagning2014Conference paper (Refereed)
  • 164.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Flygplanshaveriet vid Oajevagge 8/1 2016 (SRL 2016:01); händelseförloppet med fokus på spatial desorientering.2016Report (Other academic)
  • 165.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    On the time course of short-term forgetting: A human experimental model for the sense of balance2016In: Cognitive Neurodynamics, ISSN 1871-4080, E-ISSN 1871-4099, Vol. 10, no 1, p. 7-22Article in journal (Refereed)
    Abstract [en]

    The primary aim of this study was to establish whether the decline of the memory of an angular displacement, detected by the semicircular canals, is best characterized by an exponential function or by a power function. In 27 subjects a conflict was created between the semicircular canals and the graviceptive systems. Subjects were seated, facing forwards, in the gondola of a large centrifuge. The centrifuge was accelerated from stationary to 2.5Gz. While the swing out of the gondola (66°) during acceleration constitutes a frontal plane angular-displacement stimulus to the semicircular canals, the graviceptive systems persistently signal that the subject is upright. During 6 min at 2.5Gz the perceived head and body position was recorded; in darkness the subject repeatedly adjusted the orientation of a luminous line so that it appeared to be horizontal. Acceleration of the centrifuge induced a sensation of tilt which declined with time in a characteristic way. A three-parameter exponential function (Y = Ae−bt + C) and a power function (Y = At−b + C) were fitted to the data points. The inter-individual variability was considerable. In the vast majority of cases, however, the exponential function provided a better fit (in terms of RMS error) than the power function. The mean exponential function was: y = 27.8e−0.018t + 0.5°, where t is time in seconds. Findings are discussed with connection to possible underlying neural mechanisms; in particular, the head-direction system and short-term potentiation and persistent action potential firing in the hippocampus are considered.

  • 166.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Lemming, D.
    Levin, B.
    Use of an adjustable hand plate in studying the perceived horizontal plane during simulated flight2013In: Aviation, Space and Environmental Medicine, ISSN 0095-6562, E-ISSN 1943-4448, Vol. 84, no 7, p. 739-745Article in journal (Refereed)
    Abstract [en]

    Background: Quantitative data on spatial orientation would be valuable not only in assessing the fidelity of flight simulators, but also in evaluation of spatial orientation training. In this study a manual indicator was used for recording the subjective horizontal plane during simulated flight. Methods: In a six-degrees-of-freedom hexapod hydraulic motion platform simulator, simulating an F-16 aircraft, seven fixed-wing student pilots were passively exposed to two flight sequences. The first consisted in a number of coordinated turns with visual contact with the landscape below. The visually presented roll tilt was up to a maximum 67. The second was a takeoff with a cabin pitch up of 10, whereupon external visual references were lost. The subjects continuously indicated, with the left hand on an adjustable plate, what they perceived as horizontal in roll and pitch. There were two test occasions separated by a 3-d course on spatial disorientation. Results: Responses to changes in simulated roll were, in general, instantaneous. The indicated roll tilt was approximately 30% of the visually presented roll. There was a considerable interindividual variability. However, for the roll response there was a correlation between the two occasions. The amplitude of the response to the pitch up of the cabin was approximately 75%; the response decayed much more slowly than the stimulus. Discussion: With a manual indicator for recording the subjective horizontal plane, individual characteristics in the response to visual tilt stimuli may be detected, suggesting a potential for evaluation of simulation algorithms or training programs.

  • 167.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Ström, A
    Bergsten, Eddie
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Vestibular Stimulus and Perceived Roll Tilt During Coordinated Turns in Aircraft and Gondola Centrifuge2016In: Aerospace Medicine and Human Performance, ISSN 2375-6322, Vol. 87, no 5, p. 454-463Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: One disorienting movement pattern, common during flight, is the entering of a coordinated turn. While the otoliths persistently sense upright head position, the change in roll attitude constitutes a semicircular canal stimulus. This sensory conflict also arises during acceleration in a swing-out gondola centrifuge. From a vestibular viewpoint there are, however, certain differences between the two stimulus situations; the aim of the present study was to elucidate whether these differences are reflected in the perceived roll attitude.METHODS: Eight nonpilots were tested in a centrifuge (four runs) and during flight (two turns). The subjective visual horizontal (SVH) was measured using an adjustable luminous line in darkness. The centrifuge was accelerated from stationary to 1.56 G (roll 50°) within 7 s; the duration of the G plateau was 5 min. With the aircraft, turns with approximately 1.4 G (45°) were entered within 15 s and lasted for 5 min. Tilt perception (TP) was defined as the ratio of SVH/real roll tilt; initial and final values were calculated for each centrifugation/turn.RESULTS: In both systems there was a sensation of tilt that declined with time. The initial TP was (mean ± SD): 0.40 ± 0.27 (centrifuge) and 0.37 ± 0.30 (flight). The final TP was 0.20 ± 0.26 and 0.17 ± 0.19, respectively. Both initial and final TP correlated between the two conditions.CONCLUSION: The physical roll tilt is under-estimated to a similar degree in the centrifuge and aircraft. Also the correspondence at the individual level suggests that the vestibular dilemma of coordinated flight can be recreated in a lifelike manner using a gondola centrifuge.

  • 168.
    Ånell, Rickard
    et al.
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Grönkvist, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Sundblad, Patrik
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Gennser, Mikael
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Vaskulära gasbubblor hos jaktplanspiloter under olika flygprofiler2016Conference paper (Refereed)
  • 169. Šarabon, N
    et al.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, IB
    Babič, J
    PlanHab: Effects of hypoxia and bed rest on postural stability2015Conference paper (Refereed)
  • 170. Šket, R
    et al.
    Treichel, N
    Debevec, T
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, IB
    Schloter, M
    Stres, B
    PlanHab: Human intestinal microflora dynamics in normoxic and hypoxic bedrest studies2015Conference paper (Refereed)
  • 171. Šket, Robert
    et al.
    Treichel, Nicole
    Debevec, Tadej
    Eiken, Ola
    KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
    Mekjavic, Igor
    Schloter, Michael
    Vital, Marius
    Chandler, Jenna
    Tiedje, James M.
    Murovec, Boštjan
    Prevoršek, Zala
    Stres, Blaž
    Hypoxia and Inactivity Related Physiological Changes (Constipation, Inflammation) Are Not Reflected at the Level of Gut Metabolites and Butyrate Producing Microbial Community: The PlanHab Study2017In: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 8, no 4, article id 250Article in journal (Refereed)
    Abstract [en]

    We explored the assembly of intestinal microbiota in healthy male participants during the run-in (5 day) and experimental phases [21-day normoxic bed rest (NBR), hypoxic bedrest (HBR)], and hypoxic ambulation (HAmb) in a strictly controlled laboratory environment, balanced fluid, and dietary intakes, controlled circadian rhythm, microbial ambiental burden, and 24/7 medical surveillance. The fraction of inspired O2 (FiO2) and partial pressure of inspired O2 (PiO2) were 0.209 and 133.1 ± 0.3 mmHg for NBR and 0.141 ± 0.004 and 90.0 ± 0.4 mmHg for both hypoxic variants (HBR and HAmb; ~4,000 m simulated altitude), respectively. A number of parameters linked to intestinal transit spanning Bristol Stool Scale, defecation rates, zonulin, α1-antitrypsin, eosinophil derived neurotoxin, bile acids, reducing sugars, short chain fatty acids, total soluble organic carbon, water content, diet composition, and food intake were measured (167 variables). The abundance, structure, and diversity of butyrate producing microbial community were assessed using the two primary bacterial butyrate synthesis pathways, butyryl-CoA: acetate CoA-transferase (but) and butyrate kinase (buk) genes. Inactivity negatively affected fecal consistency and in combination with hypoxia aggravated the state of gut inflammation (p < 0.05). In contrast, gut permeability, various metabolic markers, the structure, diversity, and abundance of butyrate producing microbial community were not significantly affected. Rearrangements in the butyrate producing microbial community structure were explained by experimental setup (13.4%), experimentally structured metabolites (12.8%), and gut metabolite-immunological markers (11.9%), with 61.9% remaining unexplained. Many of the measured parameters were found to be correlated and were hence omitted from further analyses. The observed progressive increase in two immunological intestinal markers suggested that the transition from healthy physiological state toward the developed symptoms of low magnitude obesity-related syndromes was primarily driven by the onset of inactivity (lack of exercise in NBR) that were exacerbated by systemic hypoxia (HBR) and significantly alleviated by exercise, despite hypoxia (HAmb). Butyrate producing community in colon exhibited apparent resilience toward short-term modifications in host exercise or hypoxia. Progressive constipation (decreased intestinal motility) and increased local inflammation marker suggest that changes in microbial colonization and metabolism were taking place at the location of small intestine.

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