Haemodynamics Flashcards

1
Q

Difference between serum and plasma

A

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

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2
Q

Units for flow and pressure

A

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

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3
Q

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

A

Flow= ΔP/R
Darcy’s law

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4
Q

What does K and R stand for

A

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

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5
Q

Define resistance in blood flow

A

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

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6
Q

Vascular resistance

A

Resistance to flow in blood vessels

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7
Q

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

A

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

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8
Q

Laminar flow and turbulent flow

A

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

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9
Q

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

A
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10
Q

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

A
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11
Q

3 factors creating turbulent flow

A

Branching of vessels
Change in direction of blood flow
Stenosis

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12
Q

Name the point at which turbulent flow is created

A

Critical Reynolds number

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13
Q

What is a stenosis

A

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

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14
Q

3 primary factors for flow resistance

A

Diameter, length of vessel, viscosity

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15
Q

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

A

Diameter

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16
Q

What doesn’t change resistance flow

A

Vessels length
Viscosity

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17
Q

Give an example on how size of diameter affects flow

A

~20% decree in radius halves the flow

18
Q

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

A

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

19
Q

Why is the resistance in the aorta low?

A

Large diameter, relatively short

20
Q

What contributes to the greatest component of total peripheral resistance

A

Smallest arteries and arterioles

21
Q

Why is lower velocity useful in capillaries ?

A

Capillaries contain nutrients so slower flow allows absorption of nutrient

22
Q

Equation for Pulse pressure (PP)

A

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

23
Q

Mean arterial pressure (MAP)

A

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

24
Q

At what pressure will organ perfusion be impaired ?

A

Below 70mmHg

25
Q

Equation for ΔP (mean arterial pressure)

A

Mean arterial pressure - Central venous pressure (CVP)

26
Q

Equation for Mean arterial pressure (MAP)

A

MAP= CO × TPR (Total peripheral resistance)

27
Q

Define ‘pulse’

A

A shock wave that arrives slightly before the blood itself

28
Q

How does haemorrhage and age change pulse pressure

A

Decreases
(Since volume decreases)

29
Q

What factors increase pulse pressure ?

A

Elite athletes: systolic increased and diastolic decrease
Vasodilation: decreases peripheral resistance
Heart block: bradycardia

Reason: increased run off and difference in systolic&diastolic pressure

30
Q

What does the principles of indirect BP measurement rely on ?

A

Changes in type of flow (laminar and turbulent)

31
Q

What causes pathological turbulence ?

A

Atheroma
Stenoses vessel

32
Q

What can be heard and felt over a stenosed vessel?

A

Heard: Bruit
Felt: Thrill

33
Q

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

A

Korotkoff sounds

34
Q

What happens if cuff size is too small, big

A

Small: overestimates BP
Big: underestimate BP

35
Q

At what level of the body should BP be taken

A

At the level of heart

36
Q

What is the pressure below and above the heart?

A

Below level of heart: Greater P
Above: Lower P

37
Q

How does postural hypotension affect blood pressure

A

⬇️ stroke volume
Transient arterial hypotension
Symptom: dizziness upon standing

38
Q

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

A
39
Q

What happens to the velocity of blood through a stenosed vessel

A

Increases through the stenosis and turbulence occurs beyond stenosis

40
Q

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

A

Between arteriolar and capillaries