Hypobaric hypoxia (380 Torr) decreases intracellular and total body water in goats.
The effects of prolonged hypoxia on body water distribution was studied in four unanesthetized adult goats (Capra lircus) at sea level and after 16 days in a hypobaric chamber [(380 Torr, 5,500 m, 24 +/- 1 degrees C); arterial PO2 = 27 +/- 2 (SE) Torr]. Total body water (TBW), extracellular fluid volume (ECF), and plasma volume (PV) were determined with 3H2O, [14C]inulin, and indocyanine green dye, respectively. Blood volume (BV) [BV = 100PV/(100 - hematocrit)], erythrocyte volume (RCV) (RCV = BV - PV), and intracellular fluid (ICF) (ICF = TBW - ECF) and interstitial fluid (ISF) (ISF = ECF - PV) volumes were calculated. Hypoxia resulted in increased pulmonary ventilation and arterial pH and decreased arterial PCO2 and PO2 (P less than 0.05). In addition, body mass (-7.1%), TBW (-9.1%), and ICF volume (-14.4%) all decreased, whereas ECF (+11.7%) and ISF (+27.7%) volumes increased (P less than 0.05). The decrease in TBW accounted for 89% of the loss of body mass. Although PV decreased significantly (-15.3%), BV was unchanged because of an offsetting increase in RCV (+39.5%; P less than 0.05). We conclude that, in adult goats, prolonged hypobaric hypoxia results in decreases in TBW volume, ICF volume, and PV, with concomitant increases in ECF and ISF volumes.
Hoyt
R W
RW
US Army Research Institute of Environmental Medicine, Natick, Massachusetts 01760.
Durkot
M J
MJ
Forte
V A
VA
Hubbard
L J
LJ
Trad
L A
LA
Cymerman
A
A
D000818:Animals; D001274:Atmospheric Pressure; D001784:Blood Gas Analysis; D001826:Body Fluids / Q000378:metabolism; D001834:Body Water / Q000378:metabolism*; D001835:Body Weight / Q000502:physiology; D005110:Extracellular Space / Q000502:physiology; D005260:Female; D006041:Goats; D000860:Hypoxia / Q000378:metabolism*; D010953:Plasma Volume / Q000502:physiology; D011659:Pulmonary Gas Exchange