Simulation of oxygen delivery to tissues: the role of the hemoglobin oxygen equilibrium curve at altitude.

A simplified model is described to estimate the oxygen delivery to tissues as a function of oxygen uptake, gas exchange ratio, 2,3-DPG/Hb concentration ratio, arterial and venous PO2, PCO2 and pH. Due to the complexity of the oxygen delivery system, the aim of this model is to predict relative changes of the oxygen delivery to tissues induced by changes of the other variables, rather than to yield absolute values. In this work, the importance of the observed shifts of the hemoglobin oxygen equilibrium curve at altitude is evaluated in terms of the efficiency of the oxygen transport system. It will be shown that a rightward shift of the oxygen equilibrium curve is beneficial up to 5400 m.a.s.l., while for higher altitudes such shifts lead to less efficient oxygen delivery to tissues.