Rise and fall of CVP

The average blood pressure recorded in the superior vena cava near right atrium represents ‘central venous pressure’ (CVP). Traditionally CVP has been used as an indicator for predicting cardiac preload as well as volume responsiveness in critically ill patients. CVP is chiefly dependent on two factors: venous blood volume (venous return) and venous compliance. CVP is not an independent variable in determining cardiac output. Its relationship with cardiac output varies largely with the dynamic changes in the compliance of vascular compartment. The total blood volume in a venous system exists in two forms: Stressed volume (Vs) and Unstressed volume (Vu). The unstressed volume is equivalent to a basal blood volume that occupies the venous system. The stressed volume is the proportion that is dynamic in nature and affects the venous return and cardiac output. In this article, the basic physiology and applications of CVP as well as its limitations when compared to other dynamic parameters in assessing cardiovascular function are discussed.