Figure 2. Interpretation of the relations between esophageal pressure (P^es) and gastric pressure (P^ga) (plots in Figure 1). Negative P sub es is plotted on the ordinate and positive P^gaon the abscissa. Lines of iso-transdiaphragmatic pressure (iso-P^di) (iso-P^ga- P^es) are downward-sloping 45 degrees diagonals (dashed lines). Movement on the plot upward and to the right crosses iso-P^dilines in the direction of increasing transdiaphragmatic pressure (P^di). Movement along a dashed line implies no change in P^di. [14].