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Title: The physiological and renal responses to hydration status in hypoxia
Author: Richardson, Alan J.
ISNI:       0000 0004 2692 5167
Awarding Body: Brighton University
Current Institution: University of Brighton
Date of Award: 2010
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The purpose of this thesis was to examine the physiological responses to hypoxia in resting and exercising conditions and evaluate how these are influenced by changes in hydration and fluid balance. Study one showed that lower inspired oxygen fraction induced greater physiological strain, calculated using heart rate and rectal core temperature, and symptoms of altitude illness, when completing rest and exercise bouts of the intermittent walking test using inspired oxygen fractions ofO.21, 0.15 and 0.12. The second study found that a state of body fluid deficit (hypohydration) induced significant physiological strain and increased altitude illness symptoms, compared to euhydration. While drinking a large bolus of fluid (hyperhydration) induced similar physiological strain to that of hypohydration, with reports of severe headache symptoms. The third study dehydrated participants to different levels of hypohydration (1%,2%,3% of body mass loss) prior to the intermittent walking test. This found significant increases in physiological strain and altitude illness when body mass loss was greater than 2%. While 1% of body mass loss reduced the symptoms of acute mountain sickness (AMS) and headache scores, suggesting minor hypohydration may improve hypoxic tolerance. Study four showed increases in cellular stress, quantified by heat shock protein 70 (HSP70), and alterations to blood brain barrier (BBB) function when participants rested over 6 hrs in hypoxia. Rehydration in the first 2 hrs of the exposure only delayed the onset of AMS symptoms in individuals who either tolerated or dropped out of all hypoxic trials.Study five showed how hypoxia and hypohydration induce similar cardiovascular responses and when combined these effects on physiological strain are exacerbated further. Isotonic (77mmoVL NaC~ 150mmoVL glucose) fluid rehydration in the first 2 hrs of exposure was shown to maintain fluid balance, the integrity of the BBB and reduce cellular physiological strain. Water rehydration induced the most severe Lake Louise questionnaire (LLQ) symptoms and notably severe headaches, which is likely to be a result of increased serum 1OO~values and therefore BBB damage. Study six monitored hydration indices of participants trekking to Everest base camp over a 14 day period. The study showed individuals drinking approximately 45mlkg-1od-1 to have lower self reported symptoms of AMS. Individuals suffering with AMS tended to demonstrate a fluid retention when ascending to altitudes of 3500m.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available