Fig. 5
From: Venous return and mean systemic filling pressure: physiology and clinical applications
Effects of volume expansion on venous return and its determinants depending on the degree of preload responsiveness. Volume expansion increases the stressed blood volume and, then, increases mean systemic filling pressure (Pmsf). The equilibrium point is shifted to the upper right. A In the case of preload responsiveness (PR), Pmsf increases to a larger extent than right atrial pressure (RAP), inducing an increase in the (Pmsf–RAP) gradient. Venous return and cardiac output (CO) increase. B In the case of preload non-responsiveness (PNR), RAP increases to a similar extent as Pmsf, the (Pmsf–RAP) gradient remains unchanged and CO does not increase significantly