Pressure-volume curves of systemic and pulmonary circuit.

HARLAN, JAMES C., ELVIN E. SMITH, AND T. Q. RICHARDSON. Pressure-volume curves of the systemic and pulmonary circuit. Am. J. Phvsiol. 213(6): 1499-1503. 1967.-Mean svstemic pressure (klSP) and mean pulmonary pressure (MPP) were measured in eight mongrel dogs immediately after acute changes in blood volume. A decrease in blood volume of only 12 % decreased MPP to 0 mm Hg and decreased MSP to only 2 mm Hg. From the control value of 6.4 mm Hg for MSP, an addition of 6.4 mm Hg was observed for each increase in blood volume of 18 %. MPP rose from its control value of 9.9 mm Hg by an additional 9.9 mm Hg for each 12 y0 increase in blood volume. Thus, the pressure-volume curves for the systemic and pulmonary circulation are very steep indeed. These results support the conclusion that very small changes in blood volume can result in significant changes in hemodynamics. Reflexes tend to minimize these effects.