<P> CVP has been, and often still is, used as a surrogate for preload, and changes in CVP in response to infusions of intravenous fluid have been used to predict volume - responsiveness (i.e. whether more fluid will improve cardiac output). However, there is increasing evidence that CVP, whether as an absolute value or in terms of changes in response to fluid, does not correlate with ventricular volume (i.e. preload) or volume - responsiveness, and so should not be used to guide intravenous fluid therapy . Nevertheless, CVP monitoring is a useful tool to guide hemodynamic therapy . The cardiopulmonary baroreflex responds to an increase in CVP by decreasing systemic vascular resistance while increasing heart rate and ventricular contractility in dogs . </P> <Table> <Tr> <Th_colspan="2"> Site </Th> <Th> Normal pressure range (in mmHg) </Th> </Tr> <Tr> <Td_colspan="2"> Central venous pressure </Td> <Td> 3--8 </Td> </Tr> <Tr> <Td> Right ventricular pressure </Td> <Td> systolic </Td> <Td> 15--30 </Td> </Tr> <Tr> <Td> diastolic </Td> <Td> 3--8 </Td> </Tr> <Tr> <Td> Pulmonary artery pressure </Td> <Td> systolic </Td> <Td> 15--30 </Td> </Tr> <Tr> <Td> diastolic </Td> <Td> 4--12 </Td> </Tr> <Tr> <Td_colspan="2"> Pulmonary vein / <P> Pulmonary capillary wedge pressure </P> </Td> <Td> 2--15 </Td> </Tr> <Tr> <Td> Left ventricular pressure </Td> <Td> systolic </Td> <Td> 100--140 </Td> </Tr> <Tr> <Td> diastolic </Td> <Td> 3 - 12 </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Site </Th> <Th> Normal pressure range (in mmHg) </Th> </Tr> <Tr> <Td_colspan="2"> Central venous pressure </Td> <Td> 3--8 </Td> </Tr>

The two main factors that determine venous pressure are