Chapter 8: Hemodynamic Interactions

Question 1

What is mean circulatory filling pressure?

Answer 1

pressure within the cardiovacular system if forward flow was stopped - pretty much equal to peripheral venous pressure (around 7 mm Hg)

Question 2

lower central venous pressure increaes venous return, but why does the venous return eventually plateau or even fall toward the left of the venous function curve?

Answer 2

if CVP falls below athmospheric or intrathoracic pressure, vessels may collapse –> impeding forward flow and venous return

Question 3

How does the venous function curve shift when there is either:
* increase in blood volume/increased venous tone
* decrease in blood volume/decreased venous tone

Answer 3

increased blood volume/venous tone –> up and to the right

decreased blood volume/venous tone –> down and to the left

Question 4

Explain why the venous function curve’s and the cardiac function curve’s intersection is the steady state operating point

Answer 4

if CVP decreases –> decrease in CO
but also increase in venous return –> CVP would increase again –> increase in CO –> increase PVP

Question 5

Explain the different steps in the venous and cardiac function curve in a case of acute hemorrhage (volume deficit)

Answer 5

hemorrhage –> decrease in PVP and volume –> venous function curve moves to the left –> compensatory sympathetic tone –> CO increases (HR and contractility)
vasoconstriction –> venous function curve moves up a little

Question 6

How does congestive heart failure change the cardiac and venous function curves?

Answer 6

decreased cardiac function –> cardiac function curve falls down and to the right –> fluid accumulates (exacerbated by renal fluid retention from RAAS system)