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  • 1. Blogg, Lesley
    et al.
    Møllerløkken, A
    Gennser, Mikael
    KTH, Skolan för teknik och hälsa (STH), Omgivningsfysiologi.
    Response: car wrecks and caution: a lament on getting the facts straight in scientific reporting.2017Ingår i: Undersea Hyperb Med, Vol. 44, s. 492-494Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 2. Chowdhury, Helena H
    et al.
    Velebit, Jelena
    Mekjavic, Igor B
    Eiken, Ola
    KTH, Skolan för teknik och hälsa (STH), Omgivningsfysiologi. KTH, Skolan för teknik och hälsa (STH), Centra, Centrum för flyg- och rymdfysiologi, SAPC.
    Kreft, Marko
    Zorec, Robert
    Systemic Hypoxia Increases the Expression of DPP4 in Preadipocytes of Healthy Human Participants2017Ingår i: Experimental and clinical endocrinology & diabetes, ISSN 0947-7349, E-ISSN 1439-3646Artikel i tidskrift (Refereegranskat)
    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.

  • 3.
    Gennser, Mikael
    et al.
    KTH, Skolan för teknik och hälsa (STH), Omgivningsfysiologi.
    Blogg, SL
    Bubble scores after diving according to the new USNavy air decompression tables.2017Konferensbidrag (Refereegranskat)
  • 4.
    Gennser, Mikael
    et al.
    KTH, Skolan för teknik och hälsa (STH), Omgivningsfysiologi.
    Grönkvist, Mikael
    KTH, Skolan för teknik och hälsa (STH), Omgivningsfysiologi.
    No changes in pulmonary function indices after nitrox saturation dives.2017Konferensbidrag (Refereegranskat)
  • 5. Mekjavic, Igor B.
    et al.
    Ciuha, Ursa
    Grönkvist, Mikael
    KTH, Skolan för teknik och hälsa (STH), Omgivningsfysiologi.
    Eiken, Ola
    KTH, Skolan för teknik och hälsa (STH), Omgivningsfysiologi.
    The Effect of Low Ambient Relative Humidity on Physical Performance and Perceptual Responses during Load Carriage2017Ingår i: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 8, nr July, artikel-id 451Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Introduction: The study evaluated the effect of low ambient relative humidity on physical performance and perceptual responses during load carriage in a hot environment. Methods: Ten heat-unacclimatized male subjects participated in three 130-min trials, during which they walked on a treadmill, carrying a load of similar to 35 kg, at a speed of 3.2 km.h(-1), with an incident wind at the same velocity and ambient temperature at 45 degrees C. Each trial commenced with a 10-min baseline at 20 degrees C and 50% relative humidity (RH), the subjects transferred to a climatic chamber and commenced their simulated hike, comprising two 50-min walks separated by a 20-min rest period. In two, full protective equipment (FP) trials, RH was 10% (partial pressure of water vapor, p(H20) = 7.2 mmHg) in one (FP10), and 20% (p(H20) = 14.4 mmHg; FP20) in the other. In the control trial, subjects were semi-nude (SN) and carried the equipment in their backpacks; RH was 20%. Measurements included oxygen uptake, ventilation, heart rate, rectal and skin temperatures, heat flux, temperature perception, and thermal comfort. Results: In FP20, four subjects terminated the trial prematurely due to signs of heat exhaustion; there were no such signs in FP10 or SN. Upon completion of the trials, pulmonary ventilation, heart rate, and rectal temperature were lower in FP10 (33 5 I/min; 128 +/- 21 bpm; 38.2 +/- 0.4 degrees C) and SN (34 4 I/min; 113 +/- 18 bpm; 38.1 +/- 0.4 degrees C than in FP20 (39 +/- 8 l/min; 145 +/- 12 bpm; 38.6 +/- 0.42 degrees C). Evaporation was significantly greater in the SN compared to FPI and FP20 trials. FP10 was rated thermally more comfortable than FP20. Conclusion: A lower ambient partial pressure of water vapor, reflected in a lower ambient relative humidity, improved cardiorespiratory, thermoregulatory, and perceptual responses during load carriage.

  • 6. Morrison, S. A.
    et al.
    Mirnik, D.
    Korsic, S.
    Eiken, Ola
    KTH, Skolan för teknik och hälsa (STH), Omgivningsfysiologi. Swedish Aerospace Physiology Centre.
    Mekjavic, I. B.
    Dolenc-Groselj, L.
    Bed rest and hypoxic exposure affect sleep architecture and breathing stability2017Ingår i: Frontiers in Physiology, ISSN 1664-042X, E-ISSN 1664-042X, Vol. 8, nr June, artikel-id 410Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Objective: Despite over 50 years of research on the physiological effects of sustained bed rest, data characterizing its effects on sleep macrostructure and breathing stability in humans are scarce. This study was conducted to determine the effects of continuous exposure to hypoxia and sustained best rest, both individually and combined, on nocturnal sleep and breathing stability. Methods: Eleven participants completed three randomized, counter-balanced, 21-days trials of: (1) normoxic bed rest (NBR, PIO2 = 133.1 ± 0.3), (2) hypoxic ambulatory confinement (HAMB, PIO2 = 90.0 ± 0.4) and (3) hypoxic bed rest (HBR, PIO2 = 90.0 ± 0.4; ~4,000 m equivalent altitude). Full objective polysomnography was performed at baseline, on Night 1 and Night 21 in each condition. Results: In NBR Night 1, more time was spent in light sleep (10 ± 2%) compared to baseline (8 ± 2%; p = 0.028); Slow-wave sleep (SWS) was reduced from baseline in the hypoxic-only trial by 18% (HAMB Night 21, p = 0.028) and further reduced by 33% (HBR Night 1, p = 0.010), and 36% (HBR Night 21, p = 0.008) when combined with bed rest. The apnea-hypopnea index doubled from Night 1 to Night 21 in HBR (32-62 events·h-1) and HAMB (31-59 events·h-1; p = 0.002). Those who experienced greatest breathing instability from Night 1 to Night 21 (NBR) were correlated to unchanged or higher (+1%) night SpO2 concentrations (R2 = 0.471, p = 0.020). Conclusion: Bed rest negatively affects sleep macrostructure, increases the apnea-hypopnea index, and worsens breathing stability, each independently exacerbated by continuous exposure to hypoxia.

  • 7.
    Tribukait, Arne
    et al.
    KTH, Skolan för teknik och hälsa (STH), Omgivningsfysiologi. KTH, Skolan för teknik och hälsa (STH), Centra, Centrum för flyg- och rymdfysiologi, SAPC.
    Eiken, Ola
    KTH, Skolan för teknik och hälsa (STH), Centra, Centrum för flyg- och rymdfysiologi, SAPC.
    Instrument Failure, Stress, and Spatial Disorientation Leading to a Fatal Crash With a Large Aircraft2017Ingår i: Aerospace Medicine and Human Performance, ISSN 2375-6314, E-ISSN 2375-6322, Vol. 88, nr 11, s. 1043-1048Artikel i tidskrift (Refereegranskat)
    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.

  • 8. Šket, Robert
    et al.
    Treichel, Nicole
    Kublik, Susanne
    Debevec, Tadej
    Eiken, Ola
    KTH, Skolan för teknik och hälsa (STH), Omgivningsfysiologi. KTH, Skolan för teknik och hälsa (STH), Centra, Centrum för flyg- och rymdfysiologi, SAPC.
    Mekjavić, Igor
    Schloter, Michael
    Vital, Marius
    Chandler, Jenna
    Tiedje, James M.
    Murovec, Boštjan
    Prevoršek, Zala
    Likar, Matevž
    Stres, Blaž
    Hypoxia and inactivity related physiological changes precede or take place in absence of significant rearrangements in bacterial community structure: The PlanHab randomized trial pilot study2017Ingår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, nr 12, artikel-id e0188556Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We explored the assembly of intestinal microbiota in healthy male participants during the randomized crossover design of run-in (5 day) and experimental phases (21-day normoxic bed rest (NBR), hypoxic bed rest (HBR) and hypoxic ambulation (HAmb) in a strictly controlled laboratory environment, with 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; ~4000 m simulated altitude), respectively. A number of parameters linked to intestinal environment such as defecation frequency, intestinal electrical conductivity (IEC), sterol and polyphenol content and diversity, indole, aromaticity and spectral characteristics of dissolved organic matter (DOM) were measured (64 variables). The structure and diversity of bacterial microbial community was assessed using 16S rRNA amplicon sequencing. Inactivity negatively affected frequency of defecation and in combination with hypoxia increased IEC (p < 0.05). In contrast, sterol and polyphenol diversity and content, various characteristics of DOM and aromatic compounds, the structure and diversity of bacterial microbial community were not significantly affected over time. A new in-house PlanHab database was established to integrate all measured variables on host physiology, diet, experiment, immune and metabolic markers (n = 231). The observed progressive decrease in defecation frequency and concomitant increase in IEC suggested that the transition from healthy physiological state towards the developed symptoms of low magnitude obesity-related syndromes was dose dependent on the extent of time spent in inactivity and preceded or took place in absence of significant rearrangements in bacterial microbial community. Species B. thetaiotamicron, B. fragilis, B. dorei and other Bacteroides with reported relevance for dysbiotic medical conditions were significantly enriched in HBR, characterized with most severe inflammation symptoms, indicating a shift towards host mucin degradation and proinflammatory immune crosstalk.

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