Respiration In High Altitudes

[Lorenzo]

At high altitudes, atmospheric pressure is reduced from 760 mm Hg of sea level. Because atmospheric pressure is a factor that determines room air and alveolar PO2 (oxygen pressure), these two values are also reduced. These two values are permanently  depressed unless enriched oxygen is inspired.

Therefore,PAO2 < 100 mm Hg, PaO2 < 100 mm Hg and low arterial PO2 will stimulate the peripheral chemo-receptors and increase alveolar ventilation.

At high altitude, then, the main drive for ventilation changes from CO2  on the central chemo-receptors at sea level to a low PO2 drive of the peripheral chemo-receptors and hyperventilation ensues.

[Lorenzo]

Adaptive Response:

At high altitude, hypoxia can develop, resulting in increased circulating levels of erythropoietin. Erythropoetin will increase red blood cell production and eventually cause an adaptive polycythemia.