Central Venous Pressure

Question 1

True or false: ventriular EDV is not very sensitive to small changes in filling pressure.

Answer 1

Flase - it’s very sensitive to filling pressure

cardiac filling pressure is a crucial factor that determines how well the CV system operates

Question 2

What is the mean circulatory filling pressure in the abscence of flow? why does it exist?

Answer 2

because we have about 1 extra liter of volume, which causes pressure to build inside the system - approximatley 7 mmHG

Question 3

Compression of which would have a greater effect on volume movement? arteries or veins?

Answer 3

veins - remember they’re the volume reservoir

arteries and capillaries essentially do not change their volume

Question 4

During cardiac pumping, which has the greatest change in rpessure? arteries or veins?

Answer 4

arteries - veins are very compliant so the pressure doens’t change much.

Question 5

What is cardiac output and venous return in terms of the central venous compartment?

Answer 5

CO = rate at which blood leaves the central venous compartment

VR = rate at which blood is coming back to the central venous compartment

Question 6

What does an increased central venous pressure do to cardiac output? venous return?

Answer 6

high central venous pressure increases SV and CO while decreasing venous return

so under stable conductions, venous return equals cardiac output

Question 7

What is the relationship between peripheral venous pressure and mean circulatory filling pressure?

Answer 7

they’re essentially the same = 7 mmHg

Question 8

Blood flow between the PV and CV compartments is governed by what?

Answer 8

Q=delta P over R

A change in pressure between the peripheral and central compartments are wehat determine the flow
R is the small resistance associated with peripheral veins

Question 9

Why do you want CV compartment pressure to be low?

Answer 9

because if you didn’t have it low, the blood wouldn’t return to it from the peripheral vascular compartment

Question 10

Descreasing central venous pressure will do what to venous return?

Answer 10

It will increase the pressure drop between the CV and the PV, thus increasing venous return

Question 11

What is the minimum central venous pressure that gives the maximum venous return?

Answer 11

0 mmHg. If you go lower than this the veins will just collapse and you don’t get any further increase in venous return

Question 12

If a decrease in central venous pressure increases venous return, what must happen to peripheral vascular compartment pressure to increase venous return?

Answer 12

an increase in peripheral venous pressure

Question 13

What are the main influences on the peripheral venous pressure to alter venous return?

Answer 13

1. change sin blood volume - more volume, more pressure
2. changes in venous tone (mostly through sympathetic vasoconstrictor nerves and external compression by skeletal muscle0

Question 14

At what central venous pressure are CO and VR equal?

Answer 14

at 2 mmHG

lower than that - cardiac output is lower than venous return

higher pressure than that - cardiac output is higher than venous return

Question 15

A patient with abnormally high central venous pressure will have what sort of cardiac function curve? Venous function curve?

Answer 15

a depressed cardiac function curve (heart doesn’t work, so pressure backs up into the CV compartment)

a right-shifted venous function curve or both.(increased venous return causing increased CVP)

or both

Question 16

Very high central venous pressure is a hallmark of what chronic condition?

Answer 16

CHF

Question 17

A patient with abnormally low central venous pressure must have what sort of cardiac function curve? Venous function curve?

Answer 17

An elevated cardiac function curve (heart pumping all the blood out of the CV compartment faster than it can be returned)

a left-shifted venous function curve (venous return just not getting to the CV compartment)

or both

Question 18

In clinical reality, very low CVP is almost always do to which of those mentioned in the previous card?

Answer 18

the left shift of the venous function curve - poor venous return due to low blood volume or lack of venous tone

Question 19

Clinically, how can you estimate CVP?

Answer 19

by looking at the internal jugular veins