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ESA 2- Cardiovascular System > 1. Haemodynamics > Flashcards

1. Haemodynamics Flashcards

1
Q

What is the difference between serum and plasma?

A 
Plasma = fluid collected from unclotted blood
Serum = fluid collected from clotted blood

Serum = plasma - clotting factors (esp fibrinogen)

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2
Q

What is peripheral resistance? How does it increase/decrease?

A

The resistance of arteries to blood flow.

  • increases as arteries constrict
  • decreases as arteries dilate
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3
Q

What causes increased whole blood viscosity?

A
  1. Marked increase in plasma viscosity

2. Increase in red blood cells (polycythaemia), leukocytes (leukaemia) or platelets (thrombocythaemia)

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4
Q

What is the result of increased whole blood viscosity?

A

Sludging of blood in peripheries.

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5
Q

What is the commonest cause for marked increase in plasma viscosity?

A

Multiple myeloma (cancer of plasma cells - increased immunoglobulins)

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6
Q

How can the inflammatory response be measured in blood?

A

Inflammation increases concentration of acute phase plasma proteins (e.g. Fibrinogen, complement factors and C-reactive protein), causing MINOR changes in plasma viscosity.

So measure C-reactive protein (CRP) to assess inflammation.

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7
Q

What is the difference between laminar and turbulent blood flow?

A
  • Laminar = blood flows in streamlines with each layer of blood remaining the same distance from the wall.
  • Turbulent = blood flows in all directions in the vessel, and is continually mixing.
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8
Q

What type of blood flow is usually present in vessels?

A

Laminar

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9
Q

Where is blood velocity greatest in laminar flow?

A

Greater in vessel centre than in periphery due to friction of vessel walls (creates a parabolic profile).

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10
Q

What might cause turbulent blood flow?

A
  1. Rate of blood flow becomes too great (e.g. Increased chronotropy in anaemia)
  2. When blood passes by a vessel obstruction (occlusion)
  3. When blood makes a sharp turn
  4. When blood passes over rough surface (atheroma - porridge)
  5. Increases resistance to blood flow (stenosis)
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11
Q

What is the difference between blood flow and velocity?

A

Blood flow = volume of blood moving per unit time (e.g. L/hr)

Blood velocity = distance traveled by blood per unit time

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12
Q

What is the relationship between blood flow and velocity?

A

Flow = mean velocity x cross-sectional area of the vessel

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13
Q

How does blood velocity change according to total cross-sectional area? What is the implications of this in capillaries?

A

Blood velocity varies inversely with total cross-sectional area of blood vessels: velocity decreases as total area increases.

Velocity is slowest in capillaries, allowing time for gas and nutrient exchange.

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14
Q

How does blood flow change according to vessel diameter?

A

As vessel diameter decreases, resistance increases and blood flow decreases.

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15
Q

What is the effect of obstruction/stenosis on blood flow and velocity?

A

Decreases flow but increases velocity.

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16
Q

What is the effect of 2 or more stenoses in 1 blood vessel?

A

Completely inhibits blood flow as each stenosis reduces flow.

17
Q

How can a vessel stenosis cause an aneurysm?

A

Stenosis increases blood velocity… causes blood vessel damage… causes post-stenotic dilation… aneurysm.

18
Q

What is the terminology for the feel and sound cause by a stenosis?

A

Thrill (feel)
Bruit (sound in peripheral artery)
Murmur (sound across valve)

19
Q

Why is it harder to feel a pulse in the elderly?

A

Calcification of arterial tree due to ageing reduces compliance of vessel.

20
Q

How does arterial blood velocity change during systole and diastole?

A

Positive peak during systole, reaching 0 again by start of diastole. Negative during diastole.

21
Q

Why might there be a small increase in arterial blood velocity during diastole?

A

Retrograde flow in the arterial system can occur when peripheral resistance is high.

22
Q

How does blood pressure change during systole and diastole?

A

Peak in blood pressure during systole: anacrotic limb and start of dicrotic limb. Systole ends at dicrotic notch (closing of aortic valve).
Continued decrease in pressure in diastole (end of dicrotic limb).

23
Q

What is mean arterial pressure represented by on a blood pressure trace?

A

Area under the curve

24
Q

What is ‘pulse’?

A

Rhythmic expansion of an artery caused by ejection of blood from the ventricle.

What we feel is a shock wave that arrives slightly before the blood itself.

25
Q

What is pulse pressure and how is it measured?

A

Pulse pressure = peak systolic pressure - end diastolic pressure

Because of the way we measure BP with a sphygomanometer: pulse pressure = systolic pressure - diastolic pressure.
So most commonly, pulse pressure is 120 mmHg - 80 mmHg = 40 mmHg

26
Q

How can mean arterial pressure be estimated?

A

Mean arterial pressure = diastolic pressure + 1/3 pulse pressure.

27
Q

What is the value of mean arterial pressure most commonly?

A

80 mmHg + 13 mmHg = 93 mmHg

28
Q

At which point is MAP too low and what is the consequence of this?

A

If MAP falls below 70 mmHg then organ perfusion is impaired.

29
Q

What is the strength (volume) of the pulse mainly determined by?

A
  1. Force with which the left ventricle is able to eject blood into the arterial system and thus develop a normal shock wave.
  2. The pulse pressure: the greater the pulse pressure, the stronger the pulse.
30
Q

How is a weak or a strong pulse described?

A

‘Thready’ or ‘bounding’

31
Q

Name 3 conditions that can cause a thready pulse.

A
  1. Left ventricular failure
  2. Aortic valve stenosis
  3. Hyopvolaemia (severe dehydration)
32
Q

Name a condition that can cause a bounding pulse.

A

Bradychardia (such as heart block)

33
Q

Why does bradycardia cause a bounding pulse?

A

Widense pulse pressure: diastole has more time to occur… so lower end-diastolic pressure… so increased pulse pressure.

34
Q

Which 4 main factors interact to affect blood pressure?

A
  1. Cardiac output
  2. Blood volume
  3. Peripheral resistance
  4. Blood viscosity
35
Q

Suggest everyday causes for low peripheral resistance and explain the impact of this on diastolic pressure and pulse pressure.

A

Low peripheral resistance (e.g. hot bath, exercise, pregnancy)… lowers diastolic pressure… and thus increases pulse pressure.

36
Q

Why does aortic insufficiency increase pulse pressure?

A

The regurgitant flow of blood through the aortic valve back into the left ventricle… decreases the diastolic blood pressure in the aorta… and therefore increases the pulse pressure.

37
Q

Why must BP be measured at the same level as the heart and when sitting/lying?

A

Venous and arterial blood pressure greatly increase towards the feet or decrease above the heart due to gravity.
This effect is enhanced by standing.

38
Q

How are systolic and diastolic pressure determined when measuring BP?

A

Systolic pressure: when 1st hearing karotkoff sounds (phase 1 sounds)
Diastolic pressure: when sounds disappear (phase 5)

39
Q

What is normal BP?

A

120/80

ESA 2- Cardiovascular System (25 decks)

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