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.