Effect of shifts of the O2 dissociation curve upon alveolar-arterial O2 gradients in computer models of the lung with ventilation-perfusion mismatching.

The effect of a shift of the blood O2 dissociation curve (ODC) on the alveolar-arterial O2 gradient was studied in computer models of the lung with several degrees of VA/Q inequality during air breathing. A shift to the left decreases and a shift to the right increases not only the mixed-venous but also the arterial PO2. Consequently the alveolar-arterial O2 gradient is larger with a left and smaller with a right shift of the ODC. This effect of a shift of the ODC on the alveolar-arterial O2 gradient is negligible in a healthy lung but becomes quite considerable in a diseased lung with a severe mismatching of VA/Q.