Plasma volume expansion does not increase maximal cardiac output or VO2 max in lowlanders acclimatized to altitude
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Plasma volume expansion does not increase maximal cardiac output or VO2 max in lowlanders acclimatized to altitude. / Calbet, José A L; Rådegran, Göran; Boushel, Robert Christopher; Søndergaard, Hans; Saltin, Bengt; Wagner, Hans Peter.
In: American Journal of Physiology: Heart and Circulatory Physiology, Vol. 287, No. 3, 01.09.2004, p. H1214-24.Research output: Contribution to journal › Journal article › Research › peer-review
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T1 - Plasma volume expansion does not increase maximal cardiac output or VO2 max in lowlanders acclimatized to altitude
AU - Calbet, José A L
AU - Rådegran, Göran
AU - Boushel, Robert Christopher
AU - Søndergaard, Hans
AU - Saltin, Bengt
AU - Wagner, Hans Peter
PY - 2004/9/1
Y1 - 2004/9/1
N2 - 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.
AB - 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.
KW - Acclimatization
KW - Adult
KW - Altitude
KW - Arteries
KW - Biological Availability
KW - Blood Pressure
KW - Carbon Dioxide
KW - Cardiac Output
KW - Catecholamines
KW - Female
KW - Femoral Vein
KW - Hemoglobins
KW - Humans
KW - Leg
KW - Male
KW - Oxygen
KW - Oxygen Consumption
KW - Physical Endurance
KW - Plasma Substitutes
KW - Plasma Volume
KW - Pulmonary Gas Exchange
KW - Regional Blood Flow
KW - Respiration
U2 - 10.1152/ajpheart.00840.2003
DO - 10.1152/ajpheart.00840.2003
M3 - Journal article
C2 - 15142851
VL - 287
SP - H1214-24
JO - American Journal of Physiology: Heart and Circulatory Physiology
JF - American Journal of Physiology: Heart and Circulatory Physiology
SN - 0363-6135
IS - 3
ER -
ID: 33816696