Under 1 atm total pressure, the partial pressure of
O2 is 159 mmHg and the solubility of O2 in blood
is 44g/100mL.
In Denver (mile high city) PO2 = 132mmHg and
the solubility of O2 in the blood is 37g/100mL
Mt Whitney (2.5miles high) PO2 = 98 mmHg and
the solubility of O2 in the blood is 27g/100mL
Mt Everest (5.8 miles)  PO2 = 52 mmHg and the
solubility of O2 in the blood is 14g/100mL