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CVS Revision > 3 - Haemodynamics > Flashcards

3 - Haemodynamics Flashcards

1
Q

What is the difference between plasma and serum?

A

Serum is plasma without the clotting factors

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2
Q

What is polycythaemia?

A

Excess red blood cells leading to increased blood viscosity

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3
Q

What is thrombocythaemia?

A

Excess platelets leading to increased blood viscosity

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4
Q

What is leukaemia?

A

A cancer which starts in blood-forming tissue, usually the bone marrow. It leads to the over-production of abnormal white blood cells

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5
Q

Whole blood viscosity changes are uncommon (e.g. polycythaemia), minor changes to viscosity of the plasma are more typical. What plasma proteins typically change?

A
  • Fibrinogen
  • Compliment
  • C-reactive protein (CRP)
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6
Q

What vessel has the largest diameter lumen?

A

Vena cava

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7
Q

What vessel has the highest thickness wall?

A

Aorta

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8
Q

What type of liquid flow is found in the majority of blood vessels? Describe this type of flow?

A

Laminar flow

Smooth, fast flow (fastest in the centre due to more resistance around the edges of the vessel). Most energy efficient.

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9
Q

What causes turbulent flow?

A

An obstruction/constriction in the vessel, leading to disorganised flow after the obstruction. Energy is lost.

E.g. stenosed arteries, changing direction of vessels (branching)

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10
Q

In laminar flow, flow is …….. ……………. to perfusion pressure.

A

Directly proportional

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11
Q

The point at which laminar flow becomes turbulent flow as pressure increases is called the critical ………….. number.

A

Reynolds

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12
Q

What is the SI unit of pressure?

A

Pascal

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13
Q

What is conductance?

A

Measure of the ease of flow

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14
Q

What is resistance?

A

Measure of the difficulty of flow, reciprocal of conductance.

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15
Q

What is the relationship between flow, pressure and resistance (Darcy’s Law)?

A

Flow = ΔP / R

ΔP = pressure gradient

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16
Q

When blood supply to an organ needs to be changed how is flow altered?

A
  • By changing the vascular resistance.

- Blood pressure does not change

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17
Q

What factors affect vascular resistance?

Which is most important physiologically?

A
  • Diameter of vessel
  • Length of vessel
  • Viscosity of blood

Vessel length and viscosity don’t change so diameter is the most important.

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18
Q

The radius of a vessel has a large impact on flow. Flow is proportional to radius to what power?

A

4

Flow α r^4

19
Q

In which artery is resistance the lowest?

A

The aorta - large diameter and relatively short

20
Q

Which vessels contribute the most to total peripheral resistance?

A

The arterioles

  • Play the biggest role in resistance of the systemic circulation
  • Biggest drop in pressure
21
Q

Resistance in the pulmonary circulation is ………. than in the systemic system. Why is this?

A

Lower - due to shorter and wider vessels

22
Q

How is flow related to the velocity of the blood in the vessel?

A

F = V x A

  • A is the cross-sectional area of the vessel
  • In constant flow, V is inversely proportional to r^2
23
Q

Velocity of blood flow depends on the total ………………… ……….

A

Cross-sectional area

24
Q

In what type of vessel is blood flow the slowest?

A

The capillaries

  • Very large cross-sectional area
  • Velocity is reduced and increases again as they merge into veins
25
Q

What is the pulse pressure?

A

Systolic BP - diastolic BP

26
Q

How is mean arterial pressure calculated?

A

Mean arterial pressure = diastolic BP - (pulse pressure / 3)

  • Time-weighted mean
27
Q

How is mean arterial pressure related to cardiac output and total peripheral resistance?

A

MAP = CO x TPR

28
Q

How is cardiac output calculated?

A

Heart rate x Stroke volume

29
Q

What factors affect the pulse pressure?

A
  • Volume of blood ejected (stroke volume)

- Compliance (stretch) of the arterial system

30
Q

During exercise, what changes to increase the pulse pressure?

A

Stroke volume increases

31
Q

What is the effect on pulse pressure of:

a) Haemorrhage?
b) Age?

A

a) blood volume loss = decreased PP

b) atherosclerosis reduces compliance of vessels - less stretch to account for the pressure change = increase PP

32
Q

What is the pulse?

A

The shock wave that arrives slightly before the blood in a vessel

33
Q

An increased pulse pressure is described as having a …………… pulse

A

Bounding

34
Q

What can cause a bounding pulse?

A
  • Heart block (reduced electrical transmission between atria and ventricles) - bradycardia
  • Vasodilation - decreases peripheral resistance (occurs in pregnancy)
  • Elite athletes - systolic BP increases and diastolic BP decreases (large PP)
35
Q

In pathological turbulent flow, what is the effect on:

a) velocity?
b) flow?

A

a) Velocity increases

b) Flow decreases

36
Q

In terms of turbulent flow is vessels, what is:

a) Thrill?
b) Bruit?

A

Thrill - the feeling of turbulent flow

Bruit - the sound in the vessel of turbulent flow

37
Q

When measuring blood pressure, turbulent flow is created intentionally by compressing a vessel. What type of sounds can be heard?

A

Korotkoff sounds

38
Q

What is the name for a blood pressure cuff?

A

Sphygmomanometer

39
Q

Which artery is used to auscultate for blood pressure?

A

Brachial artery

40
Q

If the blood pressure cuff is too small, what will happen to the estimate of blood pressure?

A

Will overestimate the blood pressure (too high)

41
Q

If the blood pressure cuff is too big, what will happen to the estimate of blood pressure?

A

Will underestimate the blood pressure (too low)

42
Q

How should a patient be positioned for blood pressure measurement?

A
  • Taken at rest
  • Sat comfortably upright, legs uncrossed and feet flat on the floor
  • Arm supported
  • Measurement taken at level of the heart
43
Q

What effect does gravity have on blood pressure?

A
  • Pressure below the level of the heart is greater than above
  • Gravity maintains a pressure gradient that allows blood to flow from the heart to the feet
  • Pooling of blood occurs in the venous system when standing
44
Q

What is postural hypotension?

A
  • Dizziness upon standing due to transient arterial hypotension
  • When standing there is a delay in constriction of resistance vessels in the lower body, blood pools in the lower limbs
  • Less blood returns to the heart causing a transient reduction in cardiac output (Starling’s Law)
  • Less blood is pumped to the brain (dizziness, nausea, fainting)

CVS Revision (8 decks)

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