Influence of high altitude on cerebrovascular and ventilatory responsiveness to CO2

摘要: An altered acid–base balance following ascent to high altitude has been well established. Such changes in pH buffering could potentially account for the observed increase ventilatory CO2 sensitivity at altitude. Likewise, if [H+] is main determinant of cerebrovascular tone, then an alteration may also enhance cerebral blood flow (CBF) responsiveness (termed reactivity). However, effect associated with on and remains unclear. We measured ventilation , middle artery velocity (MCAv; index CBF) arterial gases sea level 5050 m 17 healthy participants during modified hyperoxic rebreathing. At m, resting MCAv were higher (P < 0.01), while bicarbonate concentration partial pressures O2 lower 0.01) compared level. Ascent increased hypercapnic reactivity (2.9 ± 1.1 vs. 4.8 1.4% mmHg−1; P (3.6 2.3 5.1 1.7 l min−1 0.01). hypocapnic was (4.2 1.0 2.0 0.6% The correlated (R2= 0.4; central chemoreflex threshold 0.7; These findings indicate that (1) increases elevates hypercapnia hypocapnia, (2) alterations be partly attributed ascent. Collectively, our provide new insights into influence function highlight potential role regulation CBF control.