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CVS > Principles of haemodynamics > Flashcards

Principles of haemodynamics Flashcards

1
Q

What is flow determined by?

A

Determined by arterial blood pressure and resistance

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2
Q

What are the 3 different flow patterns?

A

Patterns – laminar, turbulent and bolus

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3
Q

What are the 2 types of arterial pressure?

A

Systolic

Diastolic

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4
Q

What is haemodynamics?

A

Haemodynamics is the relationship between blood flow, blood pressure and resistance to flow

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5
Q

What type of system is the CVS?

A

Closed system

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6
Q

Where is majority of the blood in the CVS?

A

Venous system

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7
Q

Comment on the venous system

A

A low pressure reservoir system

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8
Q

What can the reservoir of venous blood be used to do?

A

Can be used to increase cardiac output

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9
Q

What can reduced blood flow in one area of the CVS cause?

A

Reduced blood flow to one area increases pressure upstream and alters flow to
other areas.

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10
Q

Darcy’s law

A

Flow(Q)=Pressure difference/R

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11
Q

Bernoulli’s law

A 
Role of pressure, kinetic and potential energies in flow
 Kinetic Energy: Momentum of Blood
 Potential energy: effect of gravity
 p = fluid mass
 P = pressure
 V = velocity
 h = height
 g = acceleration due to gravity
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12
Q

What is blood flow?

A

Volume of blood flowing in a given time (ml/min)

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13
Q

What is perfusion?

A

Blood flow per given mass of tissue (ml/min/g)

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14
Q

What is the velocity of blood flow?

A

Blood flow divided by the CSA through which the blood flows (cm/s)

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15
Q

Where is the velocity of blood flow the highest?

A

Velocity of blood flow in the aorta is high

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16
Q

What does branching of the arteries do?

A

Branching of the arteries slows velocity

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17
Q

What happens as cross sectional area increases?

A

Greater the CSA, slower the flow, slowest in capillaries

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18
Q

When does velocity increase?

A

Velocity increases with the veins come together

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19
Q

Equation for volume flow

A

Volume flow(Q)=Velocity(V)xArea(A)

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20
Q

What are the three patterns of blood flow?

A

Laminar
Turbulent
Bolus

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21
Q

Where is laminar blood flow patterns mostly occuring?

A

Most arteries, arterioles, venules veins

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22
Q

How is the laminar pattern said to be as?

A

Concentric shells

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23
Q

What is the velocity at walls in laminar pattern?

A

Zero velocity at walls (molecular interactions)

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24
Q

Where is the maximum velocity in a laminar pattern?

A

Maximum velocity at centre

25
Q

Where does the laminar pattern move RBC to ?

A

Moves RBC’s towards centre

26
Q

What does the laminar pattern do to blood flow through narrow vessels?

A

Speeds up blood flow through narrow vessels

27
Q

How is turbulent pattern blood flow?

A 
Blood does not flow linearly and smoothly in
adjacent layers (whirlpools, eddies, vortices) due to
increased pressure & velocity
28
Q

Where does the bolus pattern of blood flow found?

A

Capillaries

29
Q

How do the RBC’s move through capillaries and why?

A

RBCs have a larger diameter of capillaries so

move in a single file

30
Q

What are trapped between RBC’s in bolus pattern blood flow?

A

Plasma columns are trapped between RBC

31
Q

Comment on velocity in bolus pattern blood flow

A

Uniform velocity

32
Q

What does the reynolds number describe?

A

Describes what determines change from laminar to turbulent flow

33
Q

When does turbulence occur and give examples when this can ouccur?

A

Turbulence occurs when Reynold’s number exceeds a critical value (>2000)
o E.g. bruits, ejection murmur, increased blood velocity

34
Q

Equation for blood flow

A

Blood flow=Arterial blood pressure/TPR

35
Q

Where is blood pressure the highest?

A

Highest in aorta

36
Q

Pressures in aorta during sytole and diastole

A

 120 mmHg during systole

 80 mmHg during diastole

37
Q

What happens to arterial pressure in systemic circulation?

A

Arterial pressure falls steadily in systemic circulation with distance from the left ventricle

38
Q

What are the factors that affect arterial blood pressure?

A

o Cardiac output (SV, HR)
o Properties of arteries
o Peripheral resistance
o Blood viscosity

39
Q

What four key relation ships interact and involved in arterial blood pressure?

A 
o Systolic Pressure
 Pressure when ejecting
o Diastolic Pressure
 Pressure when relaxing
o Pulse pressure
 Difference between diastolic and systolic pressure
o Mean blood pressure
 Average pressure
40
Q

What does the recoil of elastic fibers of aorta and large arteries help to do?

A

Recoil of elastic fibers of the aorta and large arteries helps to propel the blood into
the circulation

41
Q

During LV ejection, what percentage of stroke volume is stored in aorta and arteries and why?

A

60-80% of stroke volume is stored in the aorta and arteries as these
structures expand

42
Q

Where is energy stored in during LV ejection?

A

Energy stored in stretched elastin

43
Q

During LV diastole, what happens to the energy which is stored in stretched elastin?

A

Energy is returned to the blood as the walls of the aorta and arteries contract

44
Q

What does return of energy to blood sustatin?

A

This sustains diastolic blood pressure and blood flow when the heart is
relaxed

45
Q

What is pulse pressure and an example?

A
  • Pulse pressure is that the finger senses

o E.g. at the wrist (radial artery)

46
Q

What does pulse pressure tell us?

A

Tells you about stroke volume and arterial compliance (stretchiness)

47
Q

Pulse pressure equation

A

Pulse pressure=Stroke volume/Compliance

48
Q

During exercise what happens to the compliance curve as the SV increases and what does this lead to?

A 
During exercise, as the SV
increases, the compliance
curve gets very steep
leading to a very high
pulse pressure
49
Q

What happens as more blood is ejected and what does this cause and causes what to increase?

A 
There is a greater stretch
of the arteries as more
blood is ejected
o This causes less compliance and less recoil and the difference between systole
and diastole increases
 So, the pulse pressure increases
50
Q

Arterial compliance

A

Decreased compliance

51
Q

What does SV now do as there’s decreased compliance?

A

o Decreased compliance (steeper curve)

o Stroke volume now increases systolic and pulse pressure disproportionally

52
Q

What does age do to stifness of vessels and what does this mean?

A

Age increases stiffness of the vessels – particularly the aorta
o This means that large pulse pressure is present throughout the arterial tree

53
Q

What happens as you move away from the aorta?

A

As you move away from the aorta, the pulse pressure increases

54
Q

What also happens as age increases to vessels?

A

You also get tapering of the vessels

55
Q

What happens to pulse pressure at arterioles?

A

At arterioles, the pulse pressure disappears due to a drop in velocity

56
Q

What is pulse pressure at aorta and what happens to this pulse pressure further down the arterial tree and why?

A
  • Pulse pressure at the aorta is relatively small but further down the arterial tree it increases
    slightly.
    o This is because the vessels become less compliant
57
Q

Why is the increase not significant?

A

However, you are still getting the effects of the aorta so the increase is not too significant

58
Q

What controls mean blood pressure?

A
  • Age
  • Disease
  • Distance along the arterial tree
  • Blood volume – SV, CO
  • Exercise – SV, CO
  • Emotion – stress, anger, fear, apprehension, pain
59
Q

Mean BP equation

A

Mean BP=diastolic pressure +(1/3)pulse pressure

CVS (17 decks)

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