Please use this identifier to cite or link to this item: http://hdl.handle.net/10553/6557
Title: Plasma volume expansion does not increase maximal cardiac output or VO2 max in lowlanders acclimatized to altitude
Authors: Calbet, JAL 
Radegran, Goran
Boushel, R.
Sondergaard, H.
Saltin, Bengt
Wagner, P.D.
UNESCO Clasification: 241106 Fisiología del ejercicio
Keywords: Hypoxia
Muscle
Cardiac output
Issue Date: 2004
Publisher: 0363-6135
Journal: American Journal of Physiology - Heart and Circulatory Physiology 
Abstract: With altitude acclimatization, blood hemoglobin concentration increases while plasma volume (PV) and maximal cardiac output (Qmax) decrease. This investigation aimed to determine whether reduction of Qmax at altitude is due to low circulating blood volume (BV). Eight Danish lowlanders (3 females, 5 males: age 24.0 +/- 0.6 yr; mean +/- SE) performed submaximal and maximal exercise on a cycle ergometer after 9 wk at 5,260 m altitude (Mt. Chacaltaya, Bolivia). This was done first with BV resulting from acclimatization (BV = 5.40 +/- 0.39 liters) and again 2-4 days later, 1 h after PV expansion with 1 liter of 6% dextran 70 (BV = 6.32 +/- 0.34 liters). PV expansion had no effect on Qmax, maximal O2 consumption (VO2), and exercise capacity. Despite maximal systemic O2 transport being reduced 19% due to hemodilution after PV expansion, whole body VO2 was maintained by greater systemic O2 extraction (P < 0.05). Leg blood flow was elevated (P < 0.05) in hypervolemic conditions, which compensated for hemodilution resulting in similar leg O2 delivery and leg VO2 during exercise regardless of PV. Pulmonary ventilation, gas exchange, and acid-base balance were essentially unaffected by PV expansion. Sea level Qmax and exercise capacity were restored with hyperoxia at altitude independently of BV. Low BV is not a primary cause for reduction of Qmax at altitude when acclimatized. Furthermore, hemodilution caused by PV expansion at altitude is compensated for by increased systemic O2 extraction with similar peak muscular O2 delivery, such that maximal exercise capacity is unaffected.
URI: http://hdl.handle.net/10553/6557
ISSN: 0363-6135
DOI: 10.1152/ajpheart.00840.2003
Source: American Journal Of Physiology-Heart And Circulatory Physiology[ISSN 0363-6135],v. 287 (3), p. H1214-H1224
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