| 1. |
- Amon, M., et al.
(författare)
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The effect of a sleep high-train low regimen on the finger cold-induced vasodilation response
- 2012
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Ingår i: High Altitude Medicine & Biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 13:1, s. 32-39
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Tidskriftsartikel (refereegranskat)abstract
- The present study evaluated the effect of a sleep high-train low regimen on the finger cold-induced vasodilation (CIVD) response. Seventeen healthy males were assigned to either a control (CON; n=9) or experimental (EXP; n=8) group. Each group participated in a 28-day aerobic training program of daily 1-h exercise (50% of peak power output). During the training period, the EXP group slept at a simulated altitude of 2800 meters (week 1) to 3400 m (week 4) above sea level. Normoxic (CIVD(NOR); CON and EXP groups) and hypoxic (CIVD(HYPO); F(I)O(2)=0.12; EXP group only) CIVD characteristics were assessed before and after the training period during a 30-min immersion of the hand in 8°C water. After the intervention, the EXP group had increased average finger skin temperature (CIVD(NOR): +0.5°C; CIVD(HYPO): +0.5°C), number of waves (CIVD(NOR): +0.5; CIVD(HYPO): +0.6), and CIVD amplitude (CIVD(NOR): +1.5°C; CIVD(HYPO): +3°C) in both CIVD tests (p<0.05). In contrast, the CON group had an increase in only the CIVD amplitude (+0.5°C; p<0.05). Thus, the enhancement of aerobic performance combined with altitude acclimatization achieved with the sleep high-train low regimen contributed to an improved finger CIVD response during cold-water hand immersion in both normoxic and hypoxic conditions.
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| 2. |
- Bjursten, Henrik, et al.
(författare)
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S100B Profiles and Cognitive Function at High Altitude
- 2010
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Ingår i: High Altitude Medicine & Biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 11:1, s. 31-38
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Tidskriftsartikel (refereegranskat)abstract
- Bjursten, Henrik, Per Ederoth, Engilbert Sigurdsson, Magnus Gottfredsson, Ingvar Syk, Orri Einarsson, and Tomas Gudbjartsson. S100B profiles and cognitive function at high altitude. High Alt. Med. Biol. 11:31-38, 2010.-Exposure to high altitude can lead to acute mountain sickness (AMS) and high altitude cerebral edema (HACE). In this study we investigated the effect of high altitude on neurocognitive function and S100B release. Increased S100B release has been hypothesized to signify a loss of integrity in the blood-brain barrier (BBB). Seven healthy volunteers trekked to Capanna Regina Margherita (4554 m above sea level) in the Monte Rosa massif. During ascent and descent, five test events were undertaken; participants underwent neurocognitive testing, Lake Louise scoring (LLS), and blood sampling to measure levels of S100B. The blood tests revealed that S100B levels increased 42% to 122% from baseline, and mean LLS increased from 0.57 to 2.57. A significant correlation was observed between both S100B levels and LLS and S100B and some neurocognitive scores. The study indicates that S100B can be released by a mild hypoxia during AMS. Moreover, an observed correlation between S100B and a lower score on neurocognitive tests suggests that the pathogenetic mechanisms may be linked. The study indicates that a decline in cognitive function is associated with symptoms of AMS.
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| 3. |
- Counter, S. Allen, et al.
(författare)
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Assessment of the Brainstem- Mediated Stapedius Muscle Reflex in Andean Children Living at High Altitudes
- 2017
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Ingår i: High Altitude Medicine & Biology. - : MARY ANN LIEBERT, INC. - 1527-0297 .- 1557-8682. ; 18:1, s. 37-45
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Tidskriftsartikel (refereegranskat)abstract
- This study examined the physiological thresholds, amplitude growth, and contraction duration of the acoustic stapedius reflex (ASR) in Andean children aged 2-17 years living at altitudes of 2850m (Altitude I Group) and 3973m (Altitude II Group) as part of a general medical assessment of the health status of the children. The brainstem-mediated ASR reveals the integrity of the neuronal components of the auditory reflex arc, including the cochlea receptors, eight cranial nerves, and brainstem neural projections to the cochlear nuclei, bilateral superior olivary nuclei, facial nerve nuclei, and facial nerve and its stapedius branch. Uncrossed (ipsilateral) and crossed (contralateral) ASR thresholds (ASRT), ASR amplitude growth (ASRG) function, and ASR muscle contraction duration (decay/ fatigue) (ASRD) were measured noninvasively with 500, 1000 Hz and broadband (bandwidth = 125-4000 Hz) noise stimulus activators using a middle ear immittance system. Oxygen saturation (SaO(2)) level and heart rate were measured in a subsample of the study group. Statistical analyses revealed that the Altitude I and Altitude II groups had ASRT, ASRG function, and ASRD rates comparable to children at sea level and that the two groups were not significantly different for any of the ASR measures. No significant association was found between SaO(2) or heart rate and ASRT, growth, and muscle fatigue rate. In conclusion, the assessment of the ASR in children in the high-altitude groups revealed normal function. Furthermore, the results indicate no adverse oto-physiological effects of altitude on the brainstem-mediated ASR at elevations between 2850 and 4000m and suggest normal middle ear and auditory brainstem function.
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| 4. |
- Counter, S. Allen, et al.
(författare)
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Middle Ear Function and Pathophysiology in Andean Children Living at High Altitudes
- 2017
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Ingår i: High Altitude Medicine & Biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 18:2, s. 163-170
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Tidskriftsartikel (refereegranskat)abstract
- The extent of altitude-related middle ear disorders in children native to high altitudes is unclear. This study examined middle ear pathophysiology in two groups of children living in high-altitude Ecuadorian Andean communities by investigating middle ear pressure (MEP), tympanic membrane compliance (TMC), and ear canal volume (ECV) using tympanometry, and by otological examination. Altitude I Group lived at 2850m, and Altitude II Group resided at around 4000m. The two high-altitude groups were compared with a reference group of children residing at sea level. Mean MEP was -3.6daPa (SD: 39.2), 3.5daPa (SD: 28.7), and 1.3daPa (SD: 13.6) for Altitude I Group, Altitude II Group, and the Sea Level Group, respectively. The MEP was not significantly different among the three groups. Mean TMC was 0.63cm3 (SD: 0.51), 0.60cm3 (SD: 0.43), and 0.60cm3 (SD: 0.24) for Altitude I Group, Altitude II Group, and the Sea Level Group, respectively. The TMC was not significantly different among the three groups. Mean ECV was 1.1 (SD: 0.26), 1.2 (SD: 0.26), and 1.0 (SD: 0.23) for Altitude I Group, Altitude II Group, and the Sea Level Group, respectively. The difference in ECV between Altitude I Group and Altitude II Group was significant (p=0.043), as was the difference between Altitude II Group and the Sea Level Group (p=0.001). ECV did not differ significantly between Altitude I Group and the Sea Level Group. Otological examination revealed a low incidence of ear canal and middle ear pathology. In conclusion, tympanometric and otological findings did not reveal a high incidence of middle ear pathophysiology in children living at altitudes as high as around 4000m.
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| 5. |
- Cristancho, Edgar, et al.
(författare)
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Arterial oxygen saturation and hemoglobin mass in postmenopausal untrained and trained altitude residents.
- 2007
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Ingår i: High altitude medicine & biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 8:4, s. 296-306
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Tidskriftsartikel (refereegranskat)abstract
- Because of lacking ventilatory stimulation by sex hormones in postmenopausal women (PW), one might expect a lowered arterial oxygen saturation (S(O(2))) in hypoxia and therefore a stronger erythropoietic reaction than in young women (YW). Nine untrained (UTRPW) and 11 trained (TRPW) postmenopausal altitude residents (2600 m) were compared to 16 untrained (UTRYW) and 16 trained young women (TRYW) to check this hypothesis and to study the combined response to hypoxia and training. S(O(2)) was decreased in PW (89.2% +/- 2.2 vs. 93.6 +/- 0.7% in YW, p < 0.01). Hb mass, however, was similar in UT (UTRYW: 9.2 +/- 0.9 g/kg(1), UTRPW: 8.7 +/- 1.0 g/kg). But if body fat rise with age was excluded by relation to fat-free mass, Hb mass was increased in UTRPW (+1.2 g/kg, p < 0.05) compared to UTRYW. Training caused a similar rise of Hb mass in PW and YW (0.3 g/kg per mL/kg x min(1) rise in V(O(2peak))). There was no difference in erythropoietin among the groups. Ferritin was higher in PW than YW. The results show that female hormones and fitness level have to be considered in studies on erythropoiesis at altitude. The role of erythropoietin during chronic hypoxia still has to be clarified.
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| 6. |
- Engan, Harald K., et al.
(författare)
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The effect of climbing mount everest on spleen contraction and increase in hemoglobin concentration during breath holding and exercise
- 2014
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Ingår i: High Altitude Medicine & Biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 15:1, s. 52-57
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Tidskriftsartikel (refereegranskat)abstract
- Release of stored red blood cells resulting from spleen contraction improves human performance in various hypoxic situations. This study determined spleen volume resulting from two contraction-evoking stimuli: breath holding and exercise before and after altitude acclimatization during a Mount Everest ascent (8848m). Eight climbers performed the following protocol before and after the climb: 5min ambient air respiration at 1370m during rest, 20min oxygen respiration, 20min ambient air respiration at 1370m, three maximal-effort breath holds spaced by 2min, 10min ambient air respiration, 5min of cycling at 100 W, and finally 10min ambient air respiration. We measured spleen volume by ultrasound and capillary hemoglobin (HB) concentration after each exposure, and heart rate (HR) and arterial oxygen saturation (Sao2) continuously. Mean (SD) baseline spleen volume was unchanged at 213 (101) mL before and 206 (52) mL after the climb. Before the climb, spleen volume was reduced to 184 (83) mL after three breath holds, and after the climb three breath holds resulted in a spleen volume of 132 (26) mL (p=0.032). After exercise, the preclimb spleen volume was 186 (89) mL vs. 112 (389) mL) after the climb (p=0.003). Breath hold duration and cardiovascular responses were unchanged after the climb. We concluded that spleen contraction may be enhanced by altitude acclimatization, probably reflecting both the acclimatization to chronic hypoxic exposure and acute hypoxia during physical work. © Copyright 2014, Mary Ann Liebert, Inc. 2014.
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| 7. |
- Keramidas, Michail E., et al.
(författare)
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Acute effects of normobaric hypoxia on hand-temperature responses during and after local cold stress
- 2014
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Ingår i: High Altitude Medicine & Biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 15:2, s. 183-191
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Tidskriftsartikel (refereegranskat)abstract
- The purpose was to investigate acute effects of normobaric hypoxia on hand-temperature responses during and after a cold-water hand immersion test. Fifteen males performed two right-hand immersion tests in 8 degrees C water, during which they were inspiring either room air (Fio(2): 0.21; AIR), or a hypoxic gas mixture (Fio(2): 0.14; HYPO). The tests were conducted in a counterbalanced order and separated by a 1-hour interval. Throughout the 30-min cold-water immersion (CWI) and the 15-min spontaneous rewarming (RW) phases, finger-skin temperatures were measured continuously with thermocouple probes; infrared thermography was also employed during the RW phase to map all segments of the hand. During the CWI phase, the average skin temperature (Tavg) of the fingers did not differ between the conditions (AIR: 10.2 +/- 0.5 degrees C, HYPO: 10.0 +/- 0.5 degrees C; p = 0.67). However, Tavg was lower in the HYPO than the AIR RW phase (AIR: 24.5 +/- 3.4 degrees C; HYPO: 22.0 +/- 3.8 degrees C; p = 0.002); a response that was alike in all regions of the immersed hand. Accordingly, present findings suggest that acute exposure to normobaric hypoxia does not aggravate the cold-induced drop in hand temperature of normothermic males. Still, hypoxia markedly impairs the rewarming responses of the hand.
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| 8. |
- Keramidas, Michail E., et al.
(författare)
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Effects of two short-term, intermittent hypoxic training protocols on the finger temperature response to local cold stress
- 2015
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Ingår i: High Altitude Medicine & Biology. - : Mary Ann Liebert Inc. - 1527-0297 .- 1557-8682. ; 16:3, s. 251-260
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Tidskriftsartikel (refereegranskat)abstract
- Keramidas, Michail E., Stylianos N. Kounalakis, Ola Eiken, and Igor B. Mekjavic. Effects of two short-Term, intermittent hypoxic training protocols on the finger temperature response to local cold stress. High Alt Med Biol 16:251-260, 2015.-The study examined the effects of two short-Term, intermittent hypoxic training protocols, namely exercising in hypoxia and living in normoxia (LL-TH; n=8), and exercising in normoxia preceded by a series of brief intermittent hypoxic exposures at rest (IHE+NOR; n=8), on the finger temperature response during a sea-level local cold test. In addition, a normoxic group was assigned as a control group (NOR; n=8). All groups trained on a cycle-ergometer 1h/day, 5 days/week for 4 weeks at 50% of peak power output. Pre, post, and 11 days after the last training session, subjects immersed their right hand for 30min in 8°C water. In the NOR group, the average finger temperature was higher in the post (+2.1°C) and 11-day after (+2.6°C) tests than in the pre-Test (p≤0.001). Conversely, the fingers were significantly colder immediately after both hypoxic protocols (LL-TH:-1.1°C, IHE+NOR:-1.8°C; p=0.01). The temperature responses returned to the pre-Training level 11 days after the hypoxic interventions. Ergo, present findings suggest that short-Term intermittent hypoxic training impairs sea-level local cold tolerance; yet, the hypoxic-induced adverse responses seem to be reversible within a period of 11 days.
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