Central Venous Pressure (CVP) is a measure of the mean pressure within the thoracic vena cava, which is the largest vein in the body and is responsible for returning blood from the systemic circulation to the heart.

CVP is an important physiological parameter used to diagnose patients at risk of heart failure, kidney failure, and internal trauma. With over 5 million patients in the U.S. presenting with heart-failure symptoms and over 20 million with kidney failure symptoms, measuring CVP is an important step in improving diagnostic accuracy and reducing healthcare costs.

Physiology
The circulatory system is divided into two compartments: a) the arterial system, which delivers blood at high pressure throughout the body, and b) the venous system, which drains blood at low pressure back into the heart. Just as mean arterial pressure (commonly referred to as blood pressure) is a key measure of arterial function, CVP is an important indicator of venous function. If the heart is characterized as a fluid pump, CVP is a major determinant of venous blood return to the heart. Low venous return translates into a lower preload and a drop in overall cardiac output, a relationship described by the Frank-Starling Mechanism.

CVP is dependent on the ratio of venous blood volume (V_v) to venous compliance (C_v)


From this relationship, it is clear that an increase in blood volume within the thoracic vena cava will lead to greater pressure exerted on the vessel walls, and that a vessel with low compliance will experience greater pressure from an increase in blood volume than a vessel with high compliance. A variety of physiological conditions that influence blood volume and/or vessel compliance can be detected by measuring CVP.