Identificador persistente para citar o vincular este elemento: http://hdl.handle.net/10553/6554
Título: During hypoxic exercise some vasoconstriction is needed to match O2 delivery with O2 demand at the microcirculatory level
Autores/as: Lundby, Carsten
Boushel, R.
Robach, Paul
Moller, Kirsten
Saltin, Bengt
Calbet, José A.L. 
Clasificación UNESCO: 2411 Fisiología humana
241106 Fisiología del ejercicio
Palabras clave: Hypoxia
Oxygen extraction
Exercise
Fecha de publicación: 2007
Editor/a: 0022-3751
Publicación seriada: Journal of Physiology 
Resumen: To test the hypothesis that the increased sympathetic tonus elicited by chronic hypoxia is needed to match O2 delivery with O2 demand at the microvascular level eight male subjects were investigated at 4559 m altitude during maximal exercise with and without infusion of ATP (80 μg (kg body mass)−1 min−1) into the right femoral artery. Compared to sea level peak leg vascular conductance was reduced by 39% at altitude. However, the infusion of ATP at altitude did not alter femoral vein blood flow (7.6 ± 1.0 versus 7.9 ± 1.0 l min−1) and femoral arterial oxygen delivery (1.2 ± 0.2 versus 1.3 ± 0.2 l min−1; control and ATP, respectively). Despite the fact that with ATP mean arterial blood pressure decreased (106.9 ± 14.2 versus 83.3 ± 16.0 mmHg, P < 0.05), peak cardiac output remained unchanged. Arterial oxygen extraction fraction was reduced from 85.9 ± 5.3 to 72.0 ± 10.2% (P < 0.05), and the corresponding venous O2 content was increased from 25.5 ± 10.0 to 46.3 ± 18.5 ml l−1 (control and ATP, respectively, P < 0.05). With ATP, leg arterial–venous O2 difference was decreased (P < 0.05) from 139.3 ± 9.0 to 116.9 ± 8.4−1 and leg inline image was 20% lower compared to the control trial (1.1 ± 0.2 versus 0.9 ± 0.1 l min−1) (P= 0.069). In summary, at altitude, some degree of vasoconstriction is needed to match O2 delivery with O2 demand. Peak cardiac output at altitude is not limited by excessive mean arterial pressure. Exercising leg inline image is not limited by restricted vasodilatation in the altitude‐acclimatized human.
URI: http://hdl.handle.net/10553/6554
ISSN: 0022-3751
DOI: 10.1113/jphysiol.2007.146035
Fuente: Journal of Physiology (2008 Jan 1), [ISSN 0022-3751], v. 586(1), p. 123-30
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