Unit 4 - Hemodynamic Concepts

Question 1

How is cardiac output or flow measured?

Answer 1

Flow = perfusion pressure difference/Resistance
CO= Delta P/R or Delta P = CO x R

Question 2

What does ohms law measure?

Answer 2

the flow moving out of the ventricles

Question 3

What does delta P in Ohm’s law stand for?

Answer 3

The change between input pressure and output pressure

Question 4

What is the input pressure when measuring CO for systemic circulation?

Answer 4

the aorta

Question 5

What is the output pressure when measuring CO for systemic circulation?

Answer 5

vena cava/RA

Question 6

What is the input pressure when measuring CO for pulmonary circulation?

Answer 6

pulmonary artery

Question 7

What is the output pressure when measuring CO for pulmonary circulation?

Answer 7

the left atrium

Question 8

Where is most of the blood in the cardiovascular system ‘stored’?

Answer 8

veins

Question 9

Why is CO from the left side of the heart and the right side of the heart the same?

Answer 9

Not all blood comes back to the heart at the same time because it is stored in the veins, so the right and left cardiac output can equal each other even though systemic circulation has so much more blood than pulmonary circulation

Question 10

What is cross-sectional area of a vessel?

Answer 10

the total area of ALL vessels of a single type

Question 11

In a vessel with a small cross sectional area, is velocity high or low?

Answer 11

high

Question 12

Where is velocity the highest?

Answer 12

in the aorta

Question 13

In a vessel with a high cross sectional area, is velocity high or low?

Answer 13

low

Question 14

Where is velocity the lowest?

Answer 14

in the capillaries

Question 15

What is viscosity?

Answer 15

internal fluid resistance of a substance

Question 16

Is viscosity the same through out the cardiovascular system?

Answer 16

No, it can change through different vessels

Question 17

What is the main determinant of viscosity?

Answer 17

PCV

Question 18

What does a higher hematocrit indicate in relation to resistance and viscocity?

Answer 18

higher viscosity, more resistance

Question 19

What is erythrocytosis?

Answer 19

abnormally high PCV

Question 20

How does erythrocytosis effect O2 carrying capacity,

viscosity, and cardiac workload?

Answer 20

increases O2 carrying capacity, increases viscosity which increases cardiac workload

Question 21

What is anemia?

Answer 21

abnormally low PCV

Question 22

How does anemia effect O2 carrying capacity, viscosity and cardiac workload?

Answer 22

it decreases O2 carrying capacity, decreases viscosity, and increases cardiac workload

Question 23

What is resistance?

Answer 23

the impediment to blood flow in a vessel

Question 24

How is resistance calculated?

Answer 24

R= Change in Pressure/ Cardiac Output

Question 25

What vessel has the highest resistance and why?

Answer 25

arterioles because they have muscles

Question 26

What is total peripheral resistance?

Answer 26

net resistance of systemic circulation

Question 27

What happens to vascular pressure during exercise?

Answer 27

vascular pressure decreases, vessels dilate, more blood flows to the needed muscles

Question 28

What causes pulmonary hypertension?

Answer 28

the dramatic increase of pulmonary resistance

Question 29

How does the right ventricle respond to pulmonary hypertension?

Answer 29

the right ventricle must generate increased pressure to eject blood

Question 30

What is conductance?

Answer 30

a measure of blood flow through a vessel for a given P difference

Question 31

How is conductance calculated?

Answer 31

1/R

Question 32

What is Poisuelle's Law?

Answer 32

the rate of flow is directly proportional to the 4th power of the vessels radius

Question 33

In respect to vessel length and width, what has the greatest effect on blood flow through it?

Answer 33

vessel width

Question 34

Viscosity and vessel length are ________ proportional to flow.

Answer 34

inversely

Question 35

Viscosity and vessel length are _______ proportional to resistance.

Answer 35

directly

Question 36

Perfusion pressure is ______ proportional to flow

Answer 36

directly

Question 37

What is laminar flow?

Answer 37

the flow of blood in streamlines

Question 38

Where is velocity the highest in laminar blood flow?

Answer 38

in the center

Question 39

Where is pressure the highest in laminar blood flow?

Answer 39

near the wall

Question 40

What is turbulent flow?

Answer 40

disorganized flow

Question 41

What type of currents are present in turbulent flow, and how does that affect the flow?

Answer 41

Eddy currents increase friction (resistance) of flow

Question 42

What are the causes of turbulent flow?

Answer 42

increased flow velocity,, obstruction, vessel turn

Question 43

What is Reynold's number?

Answer 43

a measure of the tendency for turbulence to occur

Question 44

How is Reynold's number calculated?

Answer 44

Reynolds number = (fluid density/fluid viscosity)/(average velocity of fluid x tube diameter)

Question 45

How does an increase in viscosity effect turbulence?

Answer 45

it decreases

Question 46

What causes murmurs?

Answer 46

when critical Reynold's number is exceeded - high turbulence

Question 47

What is post stenotic dilation?

Answer 47

When a vessel bulges

Question 48

How does post stenotic dilation effect turbulence?

Answer 48

A pressure gradient is created and a murmur occurs during the contractile phase

Question 49

What is the Bernoulli relationship?

Answer 49

it quantifies the relation between a pressure gradient and velocity

Question 50

How is the Bernoulli relationship clinically useful?

Answer 50

it can be used to estimate the severity of a stenosis or obstruction in a vessel

Question 51

How is the Bernoulli relationship calculated?

Answer 51

Pressure difference = 4(peak velocity)^2