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  • 1. Arvedsen, SK
    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.
    Kölegård, Roger
    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.
    Petersen, L. G.
    Damgaard, M.
    Body height and arterial pressure in seated and supine young males during +2 G centrifugation2015In: American Journal of Physiology. Regulatory Integrative and Comparative Physiology, ISSN 0363-6119, E-ISSN 1522-1490, Vol. 309, no 9Article in journal (Refereed)
    Abstract [en]

    It is known that arterial pressure correlates positively with body height in males and it has been suggested that this is due to the increasing vertical hydrostatic gradient from the heart to the carotid baroreceptors. Therefore we tested the hypothesis that a higher gravitoinertial stress induced by the use of a human centrifuge would increase mean arterial pressure (MAP) more in tall than in short males in the seated position. In short (162-171cm, n=8) and tall (194-203cm, n=10) healthy males (18-41y), brachial arterial pressure, heart rate (HR) and cardiac output were measured during +2G centrifugation, while they were seated upright with the legs kept horizontal (+2Gz). In a separate experiment, the same measurements were done with the subjects supine (+2Gx). During +2Gz MAP increased in the short (22±2 mmHg, p<0.0001) and tall (23±2 mmHg, p<0.0001) males, with no significant difference between the groups. HR increased more (p<0.05) in the tall than in the short group (14±2 versus 7±2 bpm). Stroke volume (SV) decreased in the short group (26±4 mL, p=0.001) and more so in the tall group (39±5 mL, p<0.0001; short vs tall p=0.047). During +2GX, systolic arterial pressure increased (p<0.001) and SV (p=0.012) decreased in the tall group only. In conclusion, during +2Gz MAP increased in both short and tall males with no difference between the groups. However, in the tall group HR increased more during +2Gz which could be caused by a larger hydrostatic pressure gradient from heart to head leading to greater inhibition of the carotid baroreceptors.

  • 2. Bali, TC
    et al.
    Kounalakis, SN
    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
    PlanHab: The effects of 21-day hypoxic confinement and unloading/inactivity on regional body composition and muscle strength2015Conference paper (Refereed)
  • 3. Chowdhury, Helena H
    et al.
    Velebit, Jelena
    Mekjavic, Igor B
    Eiken, Ola
    KTH, School of Technology and Health (STH), Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Kreft, Marko
    Zorec, Robert
    Systemic Hypoxia Increases the Expression of DPP4 in Preadipocytes of Healthy Human Participants2017In: Experimental and clinical endocrinology & diabetes, ISSN 0947-7349, E-ISSN 1439-3646Article in journal (Refereed)
    Abstract [en]

    Dipeptidyl peptidase 4 (DPP4) is a transmembrane glycoprotein involved in protein degradation. Due to its action on incretins, which increase insulin secretion, DPP4 is considered a therapeutic target for type 2 diabetes. Here we have studied the role of single and combined effects of hypoxia and inactivity on the expression of DPP4 in human adipose tissue of 12 adult normal-weight males. Fat biopsies were obtained at baseline and after each of three experimental campaigns. The results revealed that in isolated human preadipocytes the expression of DPP4 was significantly increased by exposure of participants to hypoxia. Physical inactivity per se had no apparent effect on the DPP4 expression. It is concluded that DPP4 may be a marker to monitor indirectly tissue hypoxia, as occurs in obese subjects.

  • 4. Ciuha, U
    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
    PlanHab: Effects of normobaric hypoxic bed rest on behavioural temperature regulation2015Conference paper (Refereed)
  • 5. Ciuha, U
    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, I.B.
    PlanHab: The effect of hypoxic bedrest on behavioural temperature regulation2014In: Proceedings from 35th Annual International Gravitational Physiology Meeting, 2014Conference paper (Other academic)
  • 6. Ciuha, Ursa
    et al.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Mekjavic, Igor B.
    Effects of normobaric hypoxic bed rest on the thermal comfort zone2015In: Journal of Thermal Biology, ISSN 0306-4565, E-ISSN 1879-0992, Vol. 49-50, p. 39-46Article in journal (Refereed)
    Abstract [en]

    Future Lunar and Mars habitats will maintain a hypobaric hypoxic environment to minimise the risk of decompression sickness during the preparation for extra-vehicular activity. This study was part of a larger study investigating the separate and combined effects of inactivity associated with reduced gravity and hypoxia, on the cardiovascular, musculoskeletal, neurohumoural, and thermoregulatory systems. Eleven healthy normothermic young male subjects participated in three trials conducted on separate occasions: (1) Normobaric hypoxic ambulatory confinement, (2) Normobaric hypoxic bedrest and (3) Normobaric normoxic bedrest Normobaric hypoxia was achieved by reduction of the oxygen fraction in the air (FiO2=0.141 +/- 0.004) within the facility, while the effects of reduced gravity were simulated by confining the subjects to a horizontal position in bed, with all daily routines performed in this position for 21 days. The present study investigated the effect of the interventions on behavioural temperature regulation. The characteristics of the thermal comfort zone (TCZ) were assessed by a water-perfused suit, with the subjects instructed to regulate the sinusoidally varying temperature of the suit within a range considered as thermally comfortable. Measurements were performed 5 days prior to the intervention (D-5), and on days 10 (D10) and 20 (D20) of the intervention. no statistically significant differences were found in any of the characteristics of the TCZ between the interventions (HAMB, HBR and NBR), or between different measurement days (D-5, D10, D20) within each intervention. rectal temperature remained stable, whereas skin temperature (T-sk) increased during all interventions throughout the one hour trial, no difference in T-sk between 0-5, D10 and D20, and between HAMB, HBR and NBR were revealed, subjects perceived the regulated temperature as thermally comfortable, and neutral or warm, we conclude that regulation of thermal comfort is not compromised by hypoxic inactivity. (C) 2015 Elsevier Ltd. All rights reserved.

  • 7. De Boever, P
    et al.
    Louwies, T
    Kounalakis, S
    Cox, B
    Jaki Mekjavic, P
    Nawrot, 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, I.B.
    PlanHab: In vivo retinal images for a non-invasive analysis of the microcirculation during hypoxia and unloading/inactivity2014In: Proceedings from 35th Annual International Gravitational Physiology Meeting, Waterloo, Canada, 2014Conference paper (Other academic)
  • 8. Debevec, T
    et al.
    Bali, T
    Simpson, E.J.
    MacDonald, I.A.
    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.
    PlanHab: Effects of simulated planetary habitation on body mass and whole body composition2014Conference paper (Other academic)
  • 9. Debevec, T
    et al.
    Ehrström, S
    Pialoux, V
    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
    Millet, GP
    FemHab: Prooxidant/antioxidant balance during and following a 10-day hypoxic bed rest2015Conference paper (Refereed)
    Abstract [en]

    Introduction:Inhabitants of the envisaged planetary habitats will be continuously exposed to reduced gravity and hypoxia. The combined effects of unloading and hypoxia on prooxidant/antioxidant balance are currently unknown.

    Methods:Healthy female participants underwent the following three, 10-day interventions: i) Normobaric normoxic bed-rest (NBR; n=11; FiO2=0.209) ii) Normobaric hypoxic ambulatory confinement (HAMB; n=9: FiO2~0.141), and iii) Normobaric hypoxic bed-rest (HBR; n=12; FiO2~0.141). Plasma oxidative stress [advanced oxidation protein products (AOPP) and nitrotyrosine], antioxidant markers [superoxide dismutase (SOD) and glutathione peroxidase (GPX)] and nitrites were determined before (Pre), during (Day 2, Day 6), immediately after (Post) and 24-hrs after (Post+1) each campaign.

    Results:Compared to Pre, the AOPP was only higher on Day 2, Day 6 and Post during the HBR and at Post during the NBR (P<0.05) while the nitrotyrosine was significantly reduced at Post+1 only during the HAMB (P<0.05). Higher levels of SOD were observed during the HAMB at Day 6 and Post+1whereas GPX was reduced at Day 6 and Post during the HBR. Nitrites were significantly higher at Post+1 in the HAMB both, compared to Pre and compared to HBR and NBR (P<0.05).

    Conclusion:These data suggest that the unloading-induced oxidative stress is exacerbated by exposure to simulated altitude of ~4000m. In addition, even habitual (low) physical activity, performed during hypoxic exposure, seems to blunt hypoxia-related oxidative stress via antioxidant system upregulation.

  • 10. Debevec, T.
    et al.
    Simpson, E. J.
    Mekjavic, I. B.
    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.
    Macdonald, I. A.
    Effects of prolonged hypoxia and bed rest on appetite and appetite-related hormones2016In: Appetite, ISSN 0195-6663, E-ISSN 1095-8304, Vol. 107, p. 28-37Article in journal (Refereed)
    Abstract [en]

    Environmental hypoxia and inactivity have both been shown to modulate appetite. To elucidate the independent and combined effects of hypoxia and bed rest-induced inactivity on appetite-related hormones and subjective appetite, eleven healthy, non-obese males underwent three experimental interventions in a cross-over and randomized fashion: 1) Hypoxic confinement combined with daily moderate-intensity exercise (HAMB, FiO2 = 0.141 ± 0.004; PiO2 = 90.0 ± 0.4 mmHg) 2) Bed rest in normoxia (NBR, FiO2 = 0.209; PiO2 = 133.1 ± 0.3 mmHg) and 3) Bed rest in hypoxia (HBR, FiO2 = 0.141 ± 0.004; PiO2 = 90.0 ± 0.4 mmHg). A mixed-meal tolerance test (MTT), followed by an ad libitum meal were performed before (Pre) and after 16-days (Post) of each intervention. Composite satiety scores (CSS) during the MTT were calculated from visual analogue scores, while fasting and postprandial concentrations of total ghrelin, peptide YY (PYY), glucagon-like peptide-1 (GLP-1) and leptin were quantified from arterialized-venous samples. Postprandial CSS were significantly lower at Post compared to Pre in NBR only (P &lt; 0.05) with no differences observed in ad libitum meal intakes. Postprandial concentrations and incremental area under the curve (AUC) for total ghrelin and PYY were unchanged following all interventions. Postprandial GLP-1 concentrations were only reduced at Post following HBR (P &lt; 0.05) with resulting AUC changes being significantly lower compared to HAMB (P &lt; 0.01). Fasting leptin was reduced following HAMB (P &lt; 0.05) with no changes observed following NBR and HBR. These findings suggest that independently, 16-day of simulated altitude exposure (∼4000 m) and bed rest-induced inactivity do not significantly alter subjective appetite or ad libitum intakes. The measured appetite-related hormones following both HAMB and HBR point to a situation of hypoxia-induced appetite stimulation, although this did not reflect in higher ad libitum intakes. Clinical Trial Registration Number: NCT02293772.

  • 11. Debevec, T
    et al.
    Simpson, EJ
    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
    Macdonald, IA
    PlanHab: The individual and combined effects of inactivity and hypoxia on insulin resistance2015Conference paper (Refereed)
    Abstract [en]

    Inactivity is know to aggravate insulin resistance. The effects of hypoxia on insulin and glucose metabolism, on the other hand, are not completely understood.

  • 12. Debevec, T
    et al.
    Simpson, T
    MacDonald, I.A.
    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.
    PlanHab: Energy expenditure and appetite sensation during hypoxic bedrest2014Conference paper (Other academic)
  • 13. Debevec, Tadej
    et al.
    Bali, Tarsi C.
    Simpson, Elizabeth J.
    Macdonald, Ian A.
    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, Igor B.
    Separate and combined effects of 21-day bed rest and hypoxic confinement on body composition2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 11, p. 2411-2425Article in journal (Refereed)
    Abstract [en]

    This study tested the hypothesis that hypoxia exacerbates reductions in body mass observed during unloading. To discern the separate and combined effects of simulated microgravity and hypoxia, 11 healthy males underwent three 21-day campaigns in a counterbalanced fashion: (1) normoxic bed rest (NBR; FiO2 = 0.209; PiO2 = 133.1 +/- A 0.3); (2) hypoxic ambulatory confinement (HAMB; FiO2 = 0.141 +/- A 0.004; PiO2 = 90.0 +/- A 0.4; similar to 4,000 m); and (3) hypoxic bed rest (HBR; FiO2 = 0.141 +/- A 0.004; PiO2 = 90.0 +/- A 0.4). The same dietary menu was applied in all campaigns. Targeted energy intakes were estimated individually using the Harris-Benedict equation taking into account whether the subjects were bedridden or ambulatory. Body mass and water balance were assessed throughout the campaigns. Whole body and regional body composition was determined before and after the campaigns using dual-energy X-ray absorptiometry. Before and during the campaigns, indirect calorimetry and visual analogue scores were employed to assess the resting energy expenditure (REE) and perceived appetite sensations, respectively. Energy intakes were lower than targeted in all campaigns (NBR: -5 %; HAMB: -14 %; HBR: -6 %; P < 0.01). Body mass significantly decreased following all campaigns (NBR: -3 %; HAMB: -4 %; HBR: -5 %; P < 0.01). While fat mass was not significantly altered, the whole body fat free mass was reduced (NBR: -4 %; HAMB: -5 %; HBR: -5 %; P < 0.01), secondary to lower limb fat-free mass reduction. Water balance was comparable between the campaigns. No changes were observed in REE and perceived appetite. Exposure to simulated altitude of similar to 4,000 m does not seem to worsen the whole body mass and fat-free mass reductions or alter resting energy expenditure and appetite during a 21-day simulated microgravity.

  • 14. Dolenc Grošelj, L
    et al.
    Morrisson, SA
    Mirnik, D
    Korsic, S
    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
    PlanHab: Periodic breathing during hypoxic bedrest2015Conference paper (Refereed)
  • 15.
    Eiken, Ola
    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.
    Kölegård, Roger
    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, Igor, B
    Keramidas, Michail E
    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.
    PlanHab: Normobaric hypoxia may exaggerate bedrest-induced reductions in peak oxygen uptake2015In: International Society for Gravitational Physiology, 2015Conference paper (Refereed)
  • 16.
    Eiken, Ola
    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.
    Mekjavic, Igor B.
    Kölegård, Roger
    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.
    Blood pressure regulation V: in vivo mechanical properties of precapillary vessels as affected by long-term pressure loading and unloading2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 3, p. 499-509Article, review/survey (Refereed)
    Abstract [en]

    Recent studies are reviewed, concerning the in vivo wall stiffness of arteries and arterioles in healthy humans, and how these properties adapt to iterative increments or sustained reductions in local intravascular pressure. A novel technique was used, by which arterial and arteriolar stiffness were determined as changes in arterial diameter and flow, respectively, during graded increments in distending pressure in the blood vessels of an arm or a leg. Pressure-induced increases in diameter and flow were smaller in the lower leg than in the arm, indicating greater stiffness in the arteries/arterioles of the leg. A 5-wk period of intermittent intravascular pressure elevations in one arm reduced pressure distension and pressure-induced flow in the brachial artery by about 50%. Conversely, prolonged reduction of arterial/arteriolar pressure in the lower body by 5 wks of sustained horizontal bedrest, induced three-fold increases of the pressure-distension and pressure-flow responses in a tibial artery. Thus, the wall stiffness of arteries and arterioles are plastic properties that readily adapt to changes in the prevailing local intravascular pressure. The discussion concerns mechanisms underlying changes in local arterial/arteriolar stiffness as well as whether stiffness is altered by changes in myogenic tone and/or wall structure. As regards implications, regulation of local arterial/arteriolar stiffness may facilitate control of arterial pressure in erect posture and conditions of exaggerated intravascular pressure gradients. That increased intravascular pressure leads to increased arteriolar wall stiffness also supports the notion that local pressure loading may constitute a prime mover in the development of vascular changes in hypertension.

  • 17.
    Gennser, Mikael
    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.
    Blogg, 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.
    Jaki Mekjavic, P
    Mekjavic, IB
    Comparison of venous bubbles and tear film bubbles after decompression during a five week 6° head-down tilt bed rest2015Conference paper (Refereed)
  • 18.
    Grönkvist, Mikael
    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.
    Ciuha, U
    Mekjavic, IB
    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.
    Värmebelastning i helikopter vid simulerat ökenuppdrag2015Conference paper (Refereed)
  • 19.
    Grönkvist, Mikael
    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.
    Keramidas, Michail E.
    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.
    Sundgren, Carl Johan
    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.
    Interaction of anti-G suit and airway pressures on cerebral oxygenation during prolonged headward acceleration.2015Conference paper (Refereed)
  • 20.
    Grönkvist, Mikael
    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.
    Keramidas, Michail E.
    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.
    Taylor, Nigel A.
    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.
    Intraocular pressure and cerebral oxygenation during prolonged headward acceleration2014Conference paper (Refereed)
  • 21.
    Grönkvist, Mikael
    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.
    Keramidas, Michail
    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.
    Samverkan mellan anti-G-dräkt och övertryck i luftvägarna på cerebral syresättning vid långvarig G-belastning i huvud-fot riktning2015Conference paper (Refereed)
  • 22. Jaki Mekjavic, P
    et al.
    Lenassi, E
    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
    FemHab: The effect of acute hypercapnia during hypoxic bedrest on posterior eye structures in females2015Conference paper (Refereed)
  • 23. Jaki Mekjavic, P.
    et al.
    Lenassi, E.
    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.
    The effect of acute hypercapnia during hypoxic bedrest and confinement on the retina2014Conference paper (Refereed)
  • 24.
    Keramidas, Michail E.
    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.
    Mekjavic, Igor B.
    Kölegård, Roger
    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.
    Chouker, Alexander
    Strewe, Claudia
    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.
    PlanHab: Hypoxia counteracts the erythropoietin suppression, but seems to exaggerate the plasma volume reduction induced by 3 weeks of bed rest2016In: Physiological Reports, E-ISSN 2051-817X, Vol. 4, no 3Article in journal (Refereed)
    Abstract [en]

    The study examined the distinct and synergistic effects of hypoxia and bed rest on the erythropoietin (EPO) concentration and relative changes in plasma volume (PV). Eleven healthy male lowlanders underwent three 21‐day confinement periods, in a counterbalanced order: (1) normoxic bed rest (NBR; PIO2: 133.1 ± 0.3 mmHg); (2) hypoxic bed rest (HBR; PIO2: 90.0 ± 0.4 mmHg, ambient simulated altitude of ~4000 m); and (3) hypoxic ambulation (HAMB; PIO2: 90.0 ± 0.4 mmHg). Blood samples were collected before, during (days 2, 5, 14, and 21) and 2 days after each confinement to determine EPO concentration. Qualitative differences in PV changes were also estimated by changes in hematocrit and hemoglobin concentration along with concomitant changes in plasma renin concentration. NBR caused an initial reduction in EPO by ~39% (= 0.04). By contrast, HBR enhanced EPO (= 0.001), but the increase was less than that induced by HAMB (< 0.01). All three confinements caused a significant reduction in PV (< 0.05), with a substantially greater drop in HBR than in the other conditions (< 0.001). Thus, present results suggest that hypoxia prevents the EPO suppression, whereas it seems to exaggerate the PV reduction induced by bed rest.

  • 25.
    Keramidas, Michail E.
    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. Jozef Stefan Institute, Slovenia.
    Stavrou, Nektarios A.M.
    Kounalakis, Stylianos D.
    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.
    Igor B., Mekjavic
    Severe hypoxia during incremental exercise to exhaustion provokes negative post-exercise affects2016In: Physiology and Behavior, ISSN 0031-9384, E-ISSN 1873-507X, Vol. 156Article in journal (Refereed)
    Abstract [en]

    The post-exercise emotional response is mainly dependent on the intensity of the exercise performed; moderate exercise causes positive feelings, whereas maximal exercise may prompt negative affects. Acute hypoxia impairs peak O2 uptake (VO2peak), resulting in a shift to a lower absolute intensity at the point of exhaustion. Hence, the purpose of the study was to examine whether a severe hypoxic stimulus would influence the post-exercise affective state in healthy lowlanders performing an incremental exercise to exhaustion. Thirty-six male lowlanders performed, in a counter-balanced order and separated by a 48-h interval, two incremental exercise trials to exhaustion to determine their VO2peak, while they were breathing either room air (AIR; FiO2: 0.21), or a hypoxic gas mixture (HYPO; FiO2: 0.12). Before and immediately after each trial, subjects were requested to complete two questionnaires, based on how they felt at that particular moment: (i) the Profile of Mood States-Short Form, and (ii) the Activation Deactivation Adjective Check List. During the post-exercise phase, they also completed the Multidimensional Fatigue Inventory. VO2peak was significantly lower in the HYPO than the AIR trial (~15%; p<0.001). Still, after the HYPO trial, energy, calmness and motivation were markedly impaired, whereas tension, confusion, and perception of physical and general fatigue were exaggerated (p≤0.05). Accordingly, present findings suggest that an incremental exercise to exhaustion performed in severe hypoxia provokes negative post-exercise emotions, induces higher levels of perceived fatigue and decreases motivation; the affective responses coincide with the comparatively lower VO2peak than that achieved in normoxic conditions.

  • 26. McDonnell, A
    et al.
    Stavrou, N
    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
    PlanHab: The effect of activity during hypoxic confinement on emotional state2015Conference paper (Refereed)
  • 27. McDonnell, AC
    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
    Peripheral Perfusion and Acute Mountain Sickness: Is There a Link?2015Conference paper (Refereed)
  • 28. McDonnell, A.C.
    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, P.J.
    Mekjavic, I.B.
    Circadian rhythm of peripheral perfusion during 10-day hypoxic confinement and bed rest2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 10, p. 2093-2104Article in journal (Refereed)
    Abstract [en]

    Future planetary habitats will be hypobaric and hypoxic to reduce the risk of decompression sickness during preparation for extra-vehicular activities. This study was part of a research programme investigating the combined effects of hypoxia and microgravity on physiological systems. We tested the hypothesis that hypoxia-induced peripheral vasoconstriction persists at night and is aggravated by bed rest. Since sleep onset has been causally linked to nocturnal vasodilatation, we reasoned that hypoxia-induced vasoconstriction at night may explain sleep disturbances at altitude. Peripheral perfusion alterations as a consequence of bed rest may explain poor sleep quality reported during sojourns on the International Space Station. Eleven males underwent three 10-day interventions in a randomised order: (1) hypoxic ambulatory confinement; (2) hypoxic bed rest; (3) normoxic bed rest. During each intervention we conducted 22-h monitoring of peripheral perfusion, as reflected by the skin temperature gradient. Measurements were conducted on the first (D 1) and last day (D 10) of each intervention. All interventions resulted in a decrease in daytime toe perfusion from D 1 to D 10. There was no difference in the magnitude of the daytime reduction in toe perfusion between the three interventions. There was a significant vasodilatation of the toes in all interventions by 11 pm. The fingertips remained well perfused throughout. Daytime vasoconstriction induced by hypoxia and/or bed rest is abolished at night, lending further support to the theory that changes in peripheral skin temperature may be functionally linked to sleep onset.

  • 29. McDonnell, A.C.
    et al.
    Golemis, A
    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.
    PlanHab: Comparison of the circadian rythm of proximal-distal temperature gradient observed during exposures to normobaric and hypobaric hypoxia2014Conference paper (Refereed)
  • 30. McDonnell, AC
    et al.
    Stavrou, N
    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
    The Effect of a Live-High/Train-High Regimen on Emotional State2015Conference paper (Refereed)
  • 31. Mekjavic, IB
    et al.
    Bali, T
    McDonnell, AC
    Debevec, T
    Simpson, EJ
    MacDonald, IA
    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.
    FemHab: Effects of 10-day planetary habitation simulation on body composition and resting energy expenditure in females2015Conference paper (Refereed)
  • 32. Mekjavic, I.B.
    et al.
    Dolenc-Groselj, L
    Morrison, S.A.
    Mirnik, D
    Korsic, S
    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.
    PlanHab: Sleep and respiration during 21-day hypoxic bedrest2014Conference paper (Refereed)
  • 33. Mekjavic, IB
    et al.
    MacDonald, IA
    Chouker, A
    Rittweger, J
    Grassi, B
    Aliverti, A
    Biolo, G
    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.
    The Planetary Habitat project2015Conference paper (Refereed)
  • 34. Mekjavic, I.B.
    et al.
    McDonnel, A
    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.
    PlanHab: Circadian rythm of proximal-distal temperature gradient during 21-day hypoxic bedrest2014Conference paper (Refereed)
  • 35. Mekjavic, I.B.
    et al.
    Pattyn, N
    Mairesse, O
    Cortoos, A
    Collet, G
    Fernandez, H.T.
    MacDonald-Nethercott, E
    Morrison, S.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.
    Sleep and performance during the winter months in Antarctica2014Conference paper (Refereed)
  • 36. Petrič, M
    et al.
    Jakovljević, M
    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
    FemHab: Effect of 10-day hypoxic bed rest on static balance in females2015Conference paper (Refereed)
  • 37. Potrc, M
    et al.
    Šuštar, M
    Jaki Mekjavic, P
    Hawlina, M
    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
    FemHab: The effect of sustained bedrest and hypoxia on electroretinographic responses2015Conference paper (Refereed)
  • 38. Režen, T.
    et al.
    Kovanda, A.
    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.
    Rogelj, B.
    Expression changes in human skeletal muscle miRNAs following 10 days of bed rest in young healthy males2014In: Acta Physiologica, ISSN 1748-1708, E-ISSN 1748-1716, Vol. 210, no 3, p. 655-666Article in journal (Refereed)
    Abstract [en]

    Aim: Studies in humans show global changes in mRNA and protein expression occur in human skeletal muscle during bed rest. As microRNAs are important regulators of expression, we analysed the global microRNA expression changes in human muscle following 10 days of sustained bed rest, with the rationale that miRNAs play key roles in atrophy of skeletal muscle. Methods: We analysed expression of miRNA and selected target proteins before and after 10 days of bed rest in biopsies obtained from the vastus lateralis muscle of 6 healthy males. Results: Fifteen of 152 miRNAs detected in human muscle tissue were differentially expressed, and all of them with exception of two were downregulated. The downregulated miRNAs include the following: miR-206, a myomir involved in function and maintenance of skeletal muscle; miR-23a, involved in insulin response and atrophy defence; and several members of the let-7 family involved in cell cycle, cell differentiation and glucose homeostasis. Predicted gene targets of these miRNAs are members of the MAPK, TNF receptor, ALK1, TGF-beta receptor and SMAD signalling pathways. All of these pathways were previously indicated to be involved in skeletal muscle response to physical inactivity. We also measured protein expression of selected miRNA targets and observed a decrease in HDAC4. Conclusion: Our data demonstrate that miRNAs in postural muscles are affected by sustained inactivity and unloading, as induced by prolonged bed rest, and hence are potentially involved in regulation of skeletal muscle adjustments to inactivity. We also propose new miRNAs involved in regulation of biological processes in adult human muscle.

  • 39. Salvadego, Desy
    et al.
    Keramidas, Michail E.
    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.
    Domenis, Rossana
    Kölegård, Roger
    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.
    Mavelli, Irene
    Rittweger, Jorn
    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, Igor B.
    Grassi, Bruno
    PlanHab: responses of skeletal muscle oxidative function to bed rest and hypoxia2015Conference paper (Refereed)
  • 40. Stavrou, NAM
    et al.
    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
    PlanHab: Examining the effect of 21-day hypoxic bed rest and confinement on emotional state2015Conference paper (Refereed)
  • 41. Stavrou, N.A.M.
    et al.
    McDonell, A.C.
    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.
    Psychological strain: Examining the effect of hypoxic bedrest and confinement2015In: Physiology and Behavior, ISSN 0031-9384, E-ISSN 1873-507X, Vol. 139, p. 497-504Article in journal (Refereed)
    Abstract [en]

    The aim was to assess the effect of a 10-day exposure to the environmental stressors anticipated in future lunar habitats on indices of psychological strain. In addition to the reduced gravity of the Moon, future habitats on the Moon will likely maintain a hypobaric hypoxic environment. The hypobaric environment will eliminate the need for long decompression profiles prior to each extra-vehicular activity. We investigated the indices of psychological strain during three 10-day conditions, designed to assess the separate and combined effects of inactivity/unloading and normobaric hypoxia on several physiological systems. Eleven male participants underwent three 10-day campaigns in a randomised manner: 1) normobaric normoxic bed rest (NBR), 2) normobaric hypoxic bed rest (HBR) and 3) normobaric hypoxic ambulatory confinement (HAMB). The most negative psychological profile appeared on day 10 of the HBR and HAMB (hypoxic) conditions. Concomitantly, a decrease in positive emotions was observed from baseline to day 10 of the HBR and NBR conditions. Thus, confinement in a hypoxic environment seems to exert a negative effect on an individual's psychological mood.

  • 42.
    Sundblad, Patrik
    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.
    Franberg, Oskar
    Siebenmann, Christoph
    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.
    Gennser, Mikael
    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.
    Measuring Uptake and Elimination of Nitrogen in Humans at Different Ambient Pressures2016In: Aerospace Medicine and Human Performance, ISSN 2375-6314, Vol. 87, no 12, p. 1045-1050Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: To measure nitrogen (N-2) wash-out and uptake requires elaborate set-ups, especially when doing the measurements at increased or decreased ambient pressure. Here we present a transportable device for quantifying N-2 turnover in humans which can be used at different ambient pressures. METHODS: A modified close-circuit electronic rebreather was used to assess N-2 turnover. Changes in N-2 volume within the rebreathing circuit, reflecting N-2 uptake or washout, were derived from the continuously monitored total system volume and the calculated volumes of oxygen and water vapor. The calculation of continuous N-2 volume curves was performed off-line using dedicated computer software. RESULTS: Four subjects participated in the proof-of-concept tests. At steady state, the drift in calculated N-2 volume in the rebreathing circuit over a 1-h duration was minimal. Three of the subjects participated in additional N-2 steady-state measurements where 1019 mL (BTPD) of N-2 was injected into the rebreathing circuit over 20 min and the measured volume increase was 1006 +/- 32 mL. Lastly, N-2 elimination was assessed during decompression to 0.5 atm and while breathing hyperoxic gas. N-2 uptake was measured during compression to 1.8 atm. The elimination and uptake curves were deemed to be realistic. DISCUSSION: A method for assessing N-2 turnover in humans has been developed and a first evaluation has been performed. It is easy to work with operationally and can be used at different ambient pressures. More research is needed in order to further validate it as a method for assessing N-2 turnover in humans.

  • 43.
    Sundblad, Patrik
    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.
    Kölegård, Roger
    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.
    G tolerance and the vasoconstrictor reserve2014In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 114, no 12, p. 2521-2528Article in journal (Refereed)
    Abstract [en]

    Because leg arterial stiffness is higher in subjects with high G tolerance, we hypothesized that subjects with high G tolerance would have larger capacity for vasoconstriction. Sixteen subjects, eight with high and eight with low G tolerance (H and L group, respectively), were exposed to a cold pressor test (CPT) in supine and upright posture. Heart rate (HR), mean arterial pressure (MAP) and cardiac output (CO) were measured, and total peripheral resistance (TPR) and stroke volume (SV) were calculated. In the supine position, CPT increased TPR more in the H group; 31 +/- A 18 % than in the L group; 11 +/- A 7 % (p < 0.05). The L group had larger increases in CO than the H group; 17 +/- A 16 vs. 3.4 +/- A 7 % (p = 0.06). In the upright position, the H group had a larger MAP response to CPT than the L group; 26 +/- A 14 vs. 14 +/- A 7 % (p = 0.06). The H group, but not the L group, had significant increases in TPR whereas the L group had significant increases in CO and SV. In response to CPT, the high G tolerance group elevated MAP by increasing TPR, whereas the low G tolerance group showed a dependency on increased CO. The H group seemed to have a larger vasoconstrictor reserve. The results further suggest that vasoconstrictor reserve capacity could constitute the link between the recent finding that indicates a relationship between G tolerance and arterial distensibility in the legs.

  • 44.
    Sundblad, Patrik
    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.
    Kölegård, Roger
    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.
    Passiv G-tolerans; kardiovaskulära omställningar under G-belastning vis-a-vis under cold-pressor test samt stimulering av arteriella baroreceptorer2014Conference paper (Refereed)
  • 45. 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)
  • 46. 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.

  • 47.
    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)
  • 48.
    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)
  • 49.
    Tribukait, Arne
    et al.
    KTH, School of Technology and Health (STH), Environmental Physiology. KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Eiken, Ola
    KTH, School of Technology and Health (STH), Centres, Swedish Aerospace Physiology Centre, SAPC.
    Instrument Failure, Stress, and Spatial Disorientation Leading to a Fatal Crash With a Large Aircraft2017In: Aerospace Medicine and Human Performance, ISSN 2375-6314, E-ISSN 2375-6322, Vol. 88, no 11, p. 1043-1048Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: An aircraft's orientation relative to the ground cannot be perceived via the sense of balance or the somatosensory system. When devoid of external visual references, the pilot must rely on instruments. A sudden unexpected instrument indication is a challenge to the pilot, who might have to question the instrument instead of responding with the controls. In this case report we analyze, from a human-factors perspective, how a limited instrument failure led to a fatal accident.

    CASE REPORT: During straight-ahead level flight in darkness, at 33,000 ft, the commander of a civil cargo airplane was suddenly confronted by an erroneous pitch-up indication on his primary flight display. He responded by pushing the control column forward, making a bunt maneuver with reduced/negative Gz during approximately 15 s. The pilots did not communicate rationally or cross-check instruments. Recordings of elevator and aileron positions suggest that the commander made intense efforts to correct for several extreme and erroneous roll and pitch indications. Gz displayed an increasing trend with rapid fluctuations and peaks of approximately 3 G. After 50 s the aircraft entered a turn with decreasing radius and finally hit the ground in an inverted attitude.

    DISCUSSION: A precipitate maneuvring response can, even if occurring in a large aircraft at high altitude, result in a seemingly inexorable course of events, ending with a crash. In the present case both pilots were probably incapacitated by acute psychological stress and spatial disorientation. Intense variations in Gz may have impaired the copilot's reading of the functioning primary flight display.Tribukait A, Eiken O. Instrument failure, stress, and spatial disorientation leading to a fatal crash with a large aircraft. Aerosp Med Hum Perform. 2017; 88(11):1043-1048.

  • 50.
    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.

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