Figure 2.

In a sheep model, pulmonary perfusion along a lung-height axis is displayed for both the supine (left side of graph) and prone (right side) positions. The total length of each of the eight bars along the x-axis represents the relative perfusion of each of the eight stacked coronal planes. The red shading within each bar represents the fraction of perfusion that is shunt perfusion, whereas the blue coloring is the nonshunt perfusion. The number adjacent to the bar is the precise value of the shunt fraction for that plane. For example, in the supine position, the most dorsal (dependent) plane receives approximately 13% of total perfusion (x-intercept) and of that perfusion, 91% of it is shunt perfusion. Note that prone positioning does not significantly change the distribution of perfusion but it does markedly reduce the total shunt fraction.

(Adapted with permission from Richter et al.³²)