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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Scandinavian journal of medicine & science in sports 13 (2003), S. 0 
    ISSN: 1600-0838
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Sports Science
    Notes: The present study aimed to compare a standard facemask (CM) and a newly modified swimming snorkel and valve system (SV) for breath-by-breath (B×B) gas analysis (K4 b2, Cosmed, Rome, Italy), and to validate the system under controlled laboratory conditions before being used in swimming. Nine healthy males performed two bouts of a stepwise exercise on an electrically braked stationary bicycle on separate days. Ventilatory and gas exchange parameters were analyzed using the same B×B portable system, with subjects breathing alternatively through the two different valves. Agreement between both methods was evaluated by Passing–Bablok regression analysis. The gas exchange values measured using the SV were highly correlated with those obtained using the CM (R2 values 〉0.9). However, differences existed between the two series of measurements so that most ventilatory and gas exchange parameters were lower (3–7%) with the SV. The error when using the SV device was mainly systematic along the whole range of measurement. Accordingly, linear regression equations were developed to further improve the accuracy of the measures when using the SV. Therefore, the modified respiratory SV system can be considered as a valid device for collecting expired gas for B×B analysis, comparable to the standard facemask, with the advantage of being suitable for measurements during swimming.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1439-6327
    Keywords: Brain ; Altitude ; Hypoxia ; Magnetic resonance imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of the present study was to look for anatomical changes in climbers' brains, using magnetic resonance imaging (MRI), after extremely high-altitude climbs and to relate them to possible associated risk factors. Clinical history, neurological examinations and MRI were carried out on a group of nine climbers before and after climbing to over 7500 m without the use of supplementary oxygen. None of the subjects showed any neurological dysfunctions. In five climbers MRI abnormalities (high signal areas, cortical atrophy) were observed before the expedition. After the descent, two of them showed new high intensity signal areas recorded by MRI. Both subjects suffered severe neurological symptoms during the climb. The present study suggested that the brain changes observed by MRI could be related to the severity of clinical events at high altitude. However, we do not know the exact meaning of such MRI findings or the reason for their location, predominantly in posterior regions of the brain. The new evidence that a high percentage of climbers show MRI brain abnormalities, and especially the appearance of changes after the ascent, reinforces the possibility of a potential neurological risk in high-altitude climbing.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1439-6327
    Keywords: Key words Erythropoietin ; Erythropoiesis ; Hypoxia ; Hypobaric chamber ; Altitude
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study aimed to determine whether brief hypoxic stimuli in a hypobaric chamber are able to elicit erythropoietin (EPO) secretion, and to effectively stimulate erythropoiesis in the short term. In two different experiments, a set of haematological, biochemical, haemorheological, aerobic performance, and medical tests were performed in two groups of healthy subjects. In the first experiment, the mean plasma concentration of EPO ([EPO]) increased from 8.7 to 13.5 mU · ml−1 (55.2%; P 〈 0.01) after 90 min of acute exposure at 540 hPa, and continued to rise until a peak was attained 3 h after the termination of hypoxia. In the second experiment, in which subjects were exposed to a simulated altitude of up to 5500 m (504 hPa) for 90 min, three times a week for 3 weeks, all haematological indicators of red cell mass increased significantly, reaching the highest mean values at the end of the programme or during the subsequent 2 weeks, including packed cell volume (from 42.5 to 45.1%; P 〈 0.01), red blood cell count (from 4.55 × 106 to 4.86 × 106 · l−1; P 〈 0.01), reticulocytes (from 0.5 to 1.4%; P 〈 0.01), and haemoglobin concentration (from 14.3 to 16.2 g · dl−1; P 〈 0.01), without an increase in blood viscosity. Arterial blood oxygen saturation during hypoxia was improved (from 60% to 78%; P 〈 0.05). Our most relevant finding is the ability to effectively stimulate erythropoiesis through brief intermittent hypoxic stimuli (90 min), in a short period of time (3 weeks), leading to a lower arterial blood desaturation in hypoxia. The proposed mechanism for these haematological and functional adaptations is the repeated triggering effect of EPO production caused by the intermittent hypoxic stimuli.
    Type of Medium: Electronic Resource
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