Steady-state cerebral blood flow regulation at altitude: interaction between oxygen and carbon dioxide.

High-altitude ascent imposes a unique cerebrovascular challenge due to two opposing blood gas chemostimuli. Specifically, hypoxia causes cerebral vasodilation, whereas respiratory-induced hypocapnia causes vasoconstriction. The conflicting nature of these two superimposed chemostimuli presents a challenge in quantifying cerebrovascular reactivity (CVR) in chronic hypoxia.

Renal reactivity: acid-base compensation during incremental ascent to high altitude.

Key Points: Ascent to high altitude imposes an acid-base challenge in which renal compensation is integral for maintaining pH homeostasis, facilitating acclimatization and helping prevent mountain sicknesses. The time-course and extent of plasticity of this important renal response during incremental ascent to altitude is unclear. We created a novel index that accurately quantifies renal acid-base compensation, which may have laboratory, fieldwork and clinical applications.