An altitude-induced PiO2 reduction, consequently leads to less oxygen available at the alveolar level in the lungs (PaO2), which in turn leads to less oxygen in the arterial blood (PaO2).
The altitude-induced decrease in PaO2 also induces a reduction in and kidney oxygenation (5). This reduction in kidney oxygenation is responsible for the stimulation of the production and the release of the hormone erythropoietin (EPO)(6). EPO stimulates red blood cell synthesis in the red bone marrow (7), which induces an increase in blood haemoglobin concentration. Higher haemoglobin concentrations increase the oxygen carrying capacity of the blood, which can therefore help restore endurance performance.
Another effect of altitude-induced decrease in PaO2 is an increase in pulmonary ventilation (Ve). This hyperventilation acts to partly offset the effects of altitude on PaO2 by helping to restore normal O2 delivery to tissues(8).