Haemodynamics Nov2 M3

Question 1

Instruments used to measure Central venous pressure (CVP) or right atrial pressure (RAP)

Answer 1

Intravenous bag of saline linked to a tube that connects to a three way valve and manometer (glass/plastic tube) also connected to the three way valve + catheter goes from three way valve and pushed in body to the right atrium

Question 2

CVP/RAP measurement: What are we measuring if the catheter sits in the superior vena cava

Answer 2

We measure CVP

Question 3

How CVP and RAP compare

Answer 3

CVP and RAP are very close but CVP > RAP (explained by fact that flow is from higher to lower pressure)

Question 4

CVP/RAP measurement: First step in method

Answer 4

Fill catheter with fluid and fill manometer to a decently high level

Question 5

CVP/RAP measurement: Second step of method (after catheter and manometer filled with fluid)

Answer 5

Disconnect saline bag from three-way valve and insert catheter in the body

Question 6

CVP/RAP measurement: Third step of method (how to read CVP/RAP measurement)

Answer 6

Manometer and catheter fluid are continuous. Manometer fluid will rise (if RAP/CVP is greater) or fall (if lower) until it reaches equilibrium. Read RAP or CVP on manometer

Question 7

CVP/RAP measurement: Method for reading the RAP/CVP nowadays

Answer 7

The whole setup is connected to a screen so you read the pressure off the screen

Question 8

Perfusion pressure definition and which values drives the fluid flow

Answer 8

Difference in P between inlet of fluid and outlet of fluid from a tube/vessel. deltaP = Pin - Pout. Perfusion pressure drives flow and not individual Pin or Pout.

Question 9

Perfusion pressure definition in relation to an organ and assumption made to measure it

Answer 9

Perf. pressure = arterial P - venous P. Pa&raquo_space;»> Pv so deltaP is approx = Pa. (for ex. Pa = 100 mmHg, Pv = 5 mmHg …)

Question 10

What happens to perfusion pressure and flow if Pin=Pout

Answer 10

Perfusion pressure (deltaP) = 0 and flow = 0

Question 11

What happens to perfusion pressure and flow if Pin>Pout and we had the same value to Pin and Pout (ex. Pin + 500 > Pout + 500)

Answer 11

Perfusion pressure (delta P) stays the same and flow stays the same

Question 12

How is atmosepheric pressure taken into account in cardiovascular situations

Answer 12

Considered to be 0 because will have same influence on Pinletand Poutlet. So perfusion pressure is still the same and flow is the same

Question 13

Two things that influence flow

Answer 13

Flow = Perfusion Pressure/Resistance (Resistance determined by length, area, nature of fluid, ..)

Question 14

Resistance formula and how to measure it

Answer 14

Resistance = Perfusion/Flow Can’t be measured

Question 15

What is the use of the notion of laminar flow

Answer 15

Describes internal friction and viscosity of the fluid

Question 16

Laminar flow explanation

Answer 16

In a vessel, outermost layer of fluid flow slower than innermost layers. Layer closest to/on midline of vessel has fastest flowing fluid (velocity)

Question 17

How fluid layers in laminar flow interact with each other

Answer 17

Internal friction between the layers causes viscosity of the fluid -> heat generated ->energy lost ->pressure lost

Question 18

As laminar flow progresses, how does the energy transform

Answer 18

Pressure energy transforms into gradual amounts of energy given to fluid in the form of heat

Question 19

Other names (2) for laminar flow and why

Answer 19

Parabolic flow. Looking from the side, flow velocity at vessel wall is 0 and greater towards center. Smooth flow. Layers move smoothly against each other

Question 20

Poiseuille’s law and Poiseuille’s formula for resistance + to which flow it applies

Answer 20

Flow = deltaP/R. R = 8vL/(Pi)r4, v = viscosity (internal friction of fluid - nu).Applies to laminar flow

Question 21

Why and how resistance decreases in an exercising muscle

Answer 21

Why : Perfusion pressure doesn’t change (Pa and Pv don’t change) but flow must increase . How: Waste products like CO2 + the falling PO2 (local metabolites) in arterioles act on smooth muscle to relax them

Question 22

Which vessels usually adjust their resistance to change flow and special name for such vessels

Answer 22

Arterioles and small arteries. Adjusting vessels are called Resistance vessels.

Question 23

What nervous system controls almost all vessels in the body and what happens if you activate it

Answer 23

Autonomic nervous system (SP and PSS system). Activate sympathetic nervous system = smooth muscles contract, vessels decrease

Question 24

Name of hormones that regulate constriction/dilation of smooth muscle around vessels and example

Answer 24

Vasoactive hormones. ex. epinephrine, norepinephrine, angiotensin, etc.

Question 25

How pulm resistance compares to systemic resistance and why must be so

Answer 25

10 times lower. Bc 10 times lower pressure gradient across but want to keep the same CO

Question 26

Formula for MAP (BP) with the three factors influencing it

Answer 26

MAP = HR x SV x TPR

Question 27

How can get formula for MAP

Answer 27

Assume deltaP in syst circulation is MAP (bc much greater then outlet P, venous). Also, flow is CO which is HR x SV.

Question 28

What can we say about the cardiovascular system when comparing it to electricity concepts + relationship between the components

Answer 28

Is a series-parallel system. 1) Right heart, lungs and left heart in series 2) Left heart, all organs and right heart are in series 3) Organs are in parallel with each other

Question 29

What is common and what is different for two organs in series. Things to consider in Poiseuille's law.

Answer 29

Share same flow but have different perfusion pressures and resistances. R = R1 + R2. deltaP = deltaP1 + deltaP2. (flow = deltaP/R)

Question 30

Organs in _______ send their blood to each other and organs in _________ don't send their blood to each other

Answer 30

series send. parallel do not send.

Question 31

What is common and what is different for two organs in parallel. Things to consider in Poiseuille's law. + Link with vascular tree/branching system

Answer 31

deltaP1 = deltaP2. 1/R = 1/R1 + 1/R2 (combined resistance is smaller than individual ones). Branching system = lower resistance (manageable for the heart)

Question 32

Give cause of arterial stenosis

Answer 32

Atherosclerotic plaque

Question 33

Consequence of arterial stenosis

Answer 33

Lumen size reduced, resistance increases

Question 34

why have pain in heart when stenosis occurs

Answer 34

flow to heart is insufficient, metabolites accumulate and this gives pain. Angina pectoris.

Question 35

graph of R as a function of degree of stenosis

Answer 35

Linear until middle degree of stenosis but then resistance increases drastically with more stenosis

Question 36

Reynold's number and how to understand it

Answer 36

is density x velocity x diameter divided by viscosity. Greater number = more chance of turbulent flow so factors towards turbulent flow on top.

Question 37

why turbulent flow in aorta

Answer 37

high velocity and high diameter

Question 38

problem caused by stenosis (related to turbulent flow)

Answer 38

resistance created by stenosis creates greater drop of flow across stenosis. Not much pressure left to supply blood to vessels even more downstream: problem.

Question 39

resistance factor in turbulent flow that adds to laminar flow

Answer 39

(1 over area of stenosed vessel minus 1 over area of non stenosed vessel) squared

Question 40

why turbulent flow problem after stenosis evolves rapidly

Answer 40

As drops, 1 over As increases, and also, it's squared. The drop of P across stenosis increases a lot.