Role of Hypobaria in Fluid Balance Response to Hypoxia

Loeppky, Jack A., Robert C. Roach, Damon Maes, Helmut Hinghofer-Szalkay, Andreas Roessler, Lee Gates, E. Royce Fletcher, and Milton V. Icenogle. Role of hypobaria in fluid balance response to hypoxia. High Alt. Med. Biol. 6:60–71, 2004.—To estimate the separate and combined effects of reduced PB and O2 levels on body fluid balance and regulating hormones, measurements were made during reduced PB (altitude, ALT; PB = 432 mm Hg, FIO2 = 0.207), reduced inspired O2 concentration (normobaric hypoxia, HYX; PB = 614 mm Hg, FIO2 = 0.142), and lowered ambient pressure without hypoxia (normoxic hypobaria HYB; PB = 434 mm Hg, FIO2 = 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...