Figure 32-23 Ventricular diastolic pressure-volume relationship. Along the flat portion of the curve, a 20-mL increase in ventricular volume causes a small increase in ventricular pressure (A to B). In contrast, the same increase in volume along the steep portion of the ventricular filling curve causes a marked increase in filling pressure (C to D). Another problem associated with the use of filling pressure as a surrogate for filling volume arises when shifts in the pressure-volume relationship occur. At point C, ventricular volume is 100 mL and ventricular pressure is 8 mm Hg. An increase in filling pressure to 15 mm Hg may accompany either increased volume (D) or decreased volume (E). The latter occurs when ventricular compliance changes and shifts the ventricular diastolic pressure-volume relationship up and to the left. (Redrawn from Mark JB: Atlas of Cardiovascular Monitoring. New York, Churchill Livingstone, 1998, Fig. 15-2.)