Altitude acclimatization and blood volume: effects of exogenous erythrocyte volume expansion. Sawka, Michael N., Andrew J. Young, Paul B. Rock, Timothy P. Lyons, Robert Boushel, Beau J. Freund, Stephen R. Muza, Allen Cymerman, Richard C. Dennis, Kent B. Pandolf, and C. Robert Valeri. US Army Research Institute of Environmental Medicine, Natick, MA 01760-5007 and Naval Blood Research Laboratory, Boston University Medical Center, Boston MA 02118
APStracts 3:0123A, 1996.
We studied sea-level residents during 13 days of altitude acclimatization to determine: (a) altitude acclimatization effects on erythrocyte volume and plasma volume; (b) if exogenous erythrocyte volume expansion alters subsequent erythrocyte volume and plasma volume adaptations; (c) if an increased blood oxygen content alters erythropoietin responses during altitude acclimatization; and (d) mechanisms responsible for plasma loss at altitude. Sixteen healthy men had a series of hematologic measurements made at sea level, on the first and ninth day of altitude (4,300 m) residence and after returning to sea level. Twenty-four hours before ascent to altitude, one group received a 700 ml infusion of autologous erythrocytes (42% hematocrit), while the other group received only a saline infusion. Erythrocyte infusion increased erythrocyte volume by 10% while saline infusion had no effect; in addition, initially at altitude blood oxygen content was 8% higher in erythrocyte infused than saline infused subjects. The new findings regarding altitude acclimatization are summarized: (a) erythrocyte volume does not change during the first 13 days and is not affected by prior exogenous expansion; (b) a modest increase in blood oxygen content does not modify erythropoietin responses; (c) plasma losses are related to vascular protein losses; and (d) exogenous erythrocyte volume expansion coincides with transient increases in plasma loss, vascular protein loss and mean arterial pressure elevation. These findings better define human blood volume responses during altitude acclimatization. 

Received 16 October 1995; accepted in final form 12 February
1996.
APS Manuscript Number A1111-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 March 96