Haemodynamics

Question 1

Difference between serum and plasma

Answer 1

Plasma- fluid collected from unclotted blood
Serum- fluid collected from clotted blood

Question 2

Units for flow and pressure

Answer 2

Flow- L/min, mL/min (for blood)
Pressure- mmHg (BP), Pascal (SI unit)

Question 3

What is the equation for flow and what is the name of this law?

Answer 3

Flow= ΔP/R
Darcy’s law

Question 4

What does K and R stand for

Answer 4

K- conductance (measure of ease of flow)
R- resistance (measure of difficulty of flow),1/K

Question 5

Define resistance in blood flow

Answer 5

The difference in mean pressure needed to move one unit of flow in steady state (mmHg min/mL)

Question 6

Vascular resistance

Answer 6

Resistance to flow in blood vessels

Question 7

Describe the relationship between resistance (R) and perfusion pressure (ΔP) and flow

Answer 7

Flow and resistance are reciprocally related
Flow UP, ΔP UP
R UP, Δ P UP

Question 8

Laminar flow and turbulent flow

Answer 8

Laminar flow: silent, smooth
Turbulent flow: noisy, disorganised

Question 9

Sketch the graph showing the relationship between flow,resistance and perfusion pressure

Question 10

Draw a sketch describing the relationship between flow and perfusion pressure in laminar and turbulent flow

Question 11

3 factors creating turbulent flow

Answer 11

Branching of vessels
Change in direction of blood flow
Stenosis

Question 12

Name the point at which turbulent flow is created

Answer 12

Critical Reynolds number

Question 13

What is a stenosis

Answer 13

Abnormal discrete narrowing of an artery / open area of a heart valve

Question 14

3 primary factors for flow resistance

Answer 14

Diameter, length of vessel, viscosity

Question 15

What is the most (physiologically) important factor for determining flow resistance

Answer 15

Diameter

Question 16

What doesn’t change resistance flow

Answer 16

Vessels length
Viscosity

Question 17

Give an example on how size of diameter affects flow

Answer 17

~20% decree in radius halves the flow

Question 18

List arteries, ventricle, veins etc. in order of decreasing pressure

Answer 18

Left ventricle
Aorta
Large arteries
Resistance vessels (small lumen diameter)
Capillaries
Venues
Veins
Vena cava

Question 19

Why is the resistance in the aorta low?

Answer 19

Large diameter, relatively short

Question 20

What contributes to the greatest component of total peripheral resistance

Answer 20

Smallest arteries and arterioles

Question 21

Why is lower velocity useful in capillaries ?

Answer 21

Capillaries contain nutrients so slower flow allows absorption of nutrient

Question 22

Equation for Pulse pressure (PP)

Answer 22

Systolic blood pressure (SBP) - Diastolic blood pressure (DBP)

Question 23

Mean arterial pressure (MAP)

Answer 23

DBP + (SBP - DBP)/3) = DBP + 1/3 PP

Question 24

At what pressure will organ perfusion be impaired ?

Answer 24

Below 70mmHg

Question 25

Equation for ΔP (mean arterial pressure)

Answer 25

Mean arterial pressure - Central venous pressure (CVP)

Question 26

Equation for Mean arterial pressure (MAP)

Answer 26

MAP= CO × TPR (Total peripheral resistance)

Question 27

Define ‘pulse’

Answer 27

A shock wave that arrives slightly before the blood itself

Question 28

How does haemorrhage and age change pulse pressure

Answer 28

Decreases (Since volume decreases)

Question 29

What factors increase pulse pressure ?

Answer 29

Elite athletes: systolic increased and diastolic decrease Vasodilation: decreases peripheral resistance Heart block: bradycardia Reason: increased run off and difference in systolic&diastolic pressure

Question 30

What does the principles of indirect BP measurement rely on ?

Answer 30

Changes in type of flow (laminar and turbulent)

Question 31

What causes pathological turbulence ?

Answer 31

Atheroma Stenoses vessel

Question 32

What can be heard and felt over a stenosed vessel?

Answer 32

Heard: Bruit Felt: Thrill

Question 33

What sound do you hear when laminar flow changes to turbulent flow

Answer 33

Korotkoff sounds

Question 34

What happens if cuff size is too small, big

Answer 34

Small: overestimates BP Big: underestimate BP

Question 35

At what level of the body should BP be taken

Answer 35

At the level of heart

Question 36

What is the pressure below and above the heart?

Answer 36

Below level of heart: Greater P Above: Lower P

Question 37

How does postural hypotension affect blood pressure

Answer 37

⬇️ stroke volume Transient arterial hypotension Symptom: dizziness upon standing

Question 38

Describe what can be hear during auscultation of the brachial artery whilst measuring BP (Laminar & turbulent flow, systolic &diastolic pressure)

Question 39

What happens to the velocity of blood through a stenosed vessel

Answer 39

Increases through the stenosis and turbulence occurs beyond stenosis

Question 40

In between which vessel types does the greatest change in BP occur

Answer 40

Between arteriolar and capillaries