In a person acclimatized for high altitude, O2 saturation is maintained because of

In acclimatization erythropoietin secretion increases promptly on ascent to high altitude and then falls somewhat over the following 4 d as the ventilatory response increases and the aerial PO2 rises. The increase in circulating red blood cells triggered by the erythropoietin begins in 2 to 3 d and is sustained as long as the individual remains at high altitude. Compensatory changes also occur in the tissues. The mitochondria, which are the site of oxidative reactions, increase in number, and myoglobin increases, which facilitates the movement of O2 into the tissues. The tissue content of cytochrome oxidase also increases.Ref: Ganong review of medical physiology 23rd edition Page no: 619