Fig. 4. In this graph, the shunt equation was modified and used to show the dependency of arterial oxygen saturation (Sao²) on mixed venous oxygen saturation (Svo²) at different shunt levels (  dotted lines ). It must be acknowledged that the graph represents a crude mathematical and hence a theoretical construct. However, it is useful in showing that the higher the shunt level is, the greater the effects are of decreasing levels of Svo²in shunted blood on oxygenation. Modified with permission from Dennehy  et al. 89