Figure 5. Trajectory of rib displacement produced by pleural and transdiaphragmatic pressure.

The filled circle (point E) corresponds to the mean ± SEM rib displacement measured during spontaneous breathing in eight dogs, and the open circle (point G) represents the position of the rib that would have occurred if the change in transdiaphragmatic pressure (ΔP_di) were zero. The dashed line O–G, therefore, is the rib displacement produced by the change in pleural pressure (ΔP_pl) alone, and the continuous line G–E is the rib displacement due to ΔP_di alone. Note that the rib trajectories produced by ΔP_pl and ΔP_di lie along the same line.