Figure 1

Comparison of effects of shunt (top) and ventilation/perfusion ratio ({\dot{\text{V}}}_{\text{A}}/\dot{\text{Q}}) inequality (bottom) on calculated physiological dead space. In general, {\dot{\text{V}}}_{\text{A}}/\dot{\text{Q}} inequality leads to greater dead space than shunt does. Log SDQ, second moment (dispersion) of the ventilation/perfusion distribution on a log scale.