Role of hypobaria in fluid balance response to hypoxia
| Autor: | Lee Gates, Jack A. Loeppky, Damon Maes, Andreas Roessler, E. Royce Fletcher, Helmut Hinghofer-Szalkay, Robert C. Roach, Milton V. Icenogle |
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| Rok vydání: | 2005 |
| Předmět: |
Adult
Male medicine.medical_specialty Physiology Acclimatization New Mexico Water-Electrolyte Imbalance Altitude Sickness Plasma renin activity Plasma electrolytes Norepinephrine Internal medicine Renin medicine Decompression chamber Humans Aldosterone Body fluid Normobaric hypoxia Analysis of Variance Chemistry Altitude Public Health Environmental and Occupational Health General Medicine Hypoxia (medical) Water-Electrolyte Balance Body Fluids Arginine Vasopressin Endocrinology Acute Disease medicine.symptom Atrial Natriuretic Factor |
| Zdroj: | High altitude medicinebiology. 6(1) |
| ISSN: | 1527-0297 |
| Popis: | To estimate the separate and combined effects of reduced P(B) and O2 levels on body fluid balance and regulating hormones, measurements were made during reduced PB (altitude, ALT; P(B) = 432 mm Hg, F(I(O2)) = 0.207), reduced inspired O2 concentration (normobaric hypoxia, HYX; P(B) = 614 mm Hg, F(I(O2)) = 0.142), and lowered ambient pressure without hypoxia (normoxic hypobaria HYB; P(B) = 434 mm Hg, F(I(O2)) = 0.296). Nine fit and healthy young men were exposed to these conditions for 10 h in a decompression chamber. Lake Louise AMS scores, urine collections, and blood samples were obtained every 3 h, with recovery measurements 2 h after exposure. AMS was significantly greater during ALT than HYX, as previously reported (J. Appl. Physiol. 81:1908-1910. 1996), because the combination of reduced P(B) and P(O2) over the 10 h favored fluid retention by reducing urine volume, while plasma volume (PV) remained higher than during HYX. At ALT the plasma Na+ fell significantly at 6 h, probably from dilution of extracellular fluid, and antidiuretic hormone (ADH) was highest (p = 0.006 versus HYB). The PV, urine flow, free water clearance, and plasma renin activity (PRA) rose significantly during recovery from ALT as AMS symptoms subsided, suggesting increased intravascular fluid and reduced adrenergic tone. During HYB, the plasma aldosterone (ALDO) and K+ levels were significantly elevated, and PRA was highest and ADH lowest, without fluid retention. During HYX, fluid balance was similar to HYB, but PV and ALDO were significantly lower, and ALDO increased significantly in recovery from HYX. The fluid retention at ALT in AMS-susceptible subjects appears related to a synergistic interaction involving reduced P(B) and ADH and ALDO. |
| Databáze: | OpenAIRE |
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