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CVS > Haemodynamics > Flashcards

Haemodynamics Flashcards

1
Q

What is haemodynamics?

A

The physical factors that control blood flow

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2
Q

What dictates the delivery of blood to different organs?

A

The metabolic demands of the organs

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3
Q

What determines the way that blood moves?

A

The pressure gradient
(High pressure to low pressure)
Flows as a fluid from a high pressure to a low pressure

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4
Q

What is the composition of blood?

A

Red blood cells
White blood cells
Plasma

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5
Q

What is serum?

A

Plasma with no clotting factors (no platelets …)

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6
Q

What is the affect of heparin on the blood?

A

Makes it unable to clot

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7
Q

How can the whole blood viscosity change?
How does this affect the blood?

A

Changes in number of blood cells:
Polycythaemia (more RBCs/higher Haematocrit)
Thrombocythaemia (more platelets)
Leukaemia (more WBCs)

Thicker sludge blood - gangrene in peripheries

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8
Q

How can plasma viscosity change?

A

Plasma protein composition can change
-fibrinogen
-c reactive proteins

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9
Q

What is C-reactive protein used to measure?

A

Inflammation
High usually indicates bacterial infection

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10
Q

What is the FLOW of blood?

A

Volume of blood transferred per unit time
Ml/min or L/min

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11
Q

What is pressure and what is blood pressure measured in?

A

Force per unit area exerted by the blood
(mmHg) mm of mercury

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12
Q

What is cardiac output? (Equation)

A

CO = stroke volume x heart rate

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13
Q

What is stroke volume?

A

Volume of blood squeezed out of the left ventricle every cardiac cycle

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14
Q

What factors influence FLOW of blood?

A

Conductance (ease of flow/resistance)
Pressure gradient/difference

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15
Q

What equation can relate flow to conductance and pressure difference?

A

Flow = conductance x pressure difference

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16
Q

What is vascular resistance?

A

Resistance to blood flow in blood vessels

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17
Q

How are resistance and flow related?

A

Inversely proportional
As resistance increases flow decreases

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18
Q

What factor is normally changed if flow needs to be increased to an area?

A

Resistance decreased

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19
Q

What are the 2 types of blood flow?

A

Laminar flow (smooth/silent and maintains energy, travels in stream lines)

Turbulent flow (disorganised, noisy energy lost)

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20
Q

What is a stenosis?

A

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

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21
Q

What point does laminar flow become turbulent?

A

When flow can not increase proportionally to match the increased pressure in the blood vessel

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22
Q

What is the point called which pressure increases beyond which flow can match it linearly so flow becomes turbulent?

A

Critical Reynolds number

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23
Q

What is the main factor which affects resistance to blood flow?

A

Blood vessel diameter
(Vessel length doesn’t usually change and viscosity is very tightly regulated)

24
Q

What does a drop in pressure indicate in terms of resistance to flow?

A

Changed

25
Q

Why does the aorta have a low resistance?

A

Large diameter
Short

26
Q

Which blood vessel type has the biggest affect of total peripheral resistance?

A

Arterioles

27
Q

What is velocity?

A

Distance fluid (blood moves in a given time

28
Q

The capillaries have a very large cross sectional area, this slows blood flow down, why is this useful?

A

Allows time for nutrients and waste to be exchanged between blood and tissues

29
Q

Does increasing vessel diameter increase or decrease blood velocity?

Why does this happen?

A

Increases

Inc vessel diameter = less resistance (less blood touching vessel wall/less friction) = more blood flow at higher speed

30
Q

What is diastole?

A

When heart is relaxed and filling up with blood

31
Q

What is systole?

A

When heart contracts squeezing out blood

32
Q

What is pulse pressure?

A

Difference between peak systolic pressure and end diastolic pressure

33
Q

What is considered a normal blood pressure?

A

120/80 mmHg or below
(90/60 - 120/80 mmHg)

34
Q

What is the Dicrotic notch on a blood pressure time graph?

A

The point which pressure starts to increase when the atrioventricular valves close

35
Q

What are the 2 equations for Mean Arterial pressure?

A

MAP = Diastolic blood pressure + 1/3(Pulse pressure)
MAP = Diastolic blood pressure + 1/3(Systolic pressure - Diastolic pressure)
OR

MAP = Cardiac output x total peripheral resistance

36
Q

What determines pulse pressure?

A

Volume of blood ejected (SV)
Compliance of the blood vessels

37
Q

How does haemorrhaging affect pulse pressure?

A

Decreases it
Less blood volume ejected

38
Q

How can age affect pulse pressure, what condition of the vessels usually occurs with age?
How does this affect pulse pressure?

A

Atherosclerosis reduces vessel compliance

Increased pulse pressure as vessel compliance reduces

39
Q

What is the pulse?

A

The shock wave that arrives before the blood

40
Q

What does a strong and weak pulse indicate (in terms of stroke volume)?

A

Strong = high stroke volume
Weak = low stroke volume

41
Q

What happens to the velocity of blood in a stenosis?

A

Initially it decreases since the resistance of the vessel increases since its become narrower

So the heart pumps harder increasing stroke volume to increase the velocity to maintain the cardiac output

42
Q

What can be heard from a stenosed vessel?

A

Bruit

43
Q

What can be felt from a stenosed vessel?

A

A thrill

44
Q

Why can a thrill be felt and a bruit be heard from a stenosed vessel?

A

Laminar flow changed to turbulent flow by narrowing of the blood vessel

45
Q

How is blood pressure measured?

A

Using a pressure cuff

46
Q

What artery is targeted and squeezed by the pressure cuff?

A

Brachial artery

47
Q

Describe how a pressure cuff is used to measure blood pressure:

A

Pressure of cuff increased restricting blood flow through the brachial artery occluding it
Pressure is then slowly reduced
blood flow is changed from laminar to turbulent flow causing sounds to be heard called Korotokoff sounds
First point at which Korotokoff sounds can be heard is the systolic blood pressure
Once the blood flow goes from turbulent to laminar/silent this is the diastolic blood pressure

48
Q

What are Korotokoff sounds?

A

The tapping noises created by converting laminar flow into turbulent flow

49
Q

How is systolic pressure determined using a pressure cuff?

A

When the Korotokoff sounds are first heard (tapping noises)

50
Q

How is diastolic pressure determined using a pressure cuff?

A

Pressure at which the Korotokoff sounds stop being heard
(Turbulent flow is now laminar/silent)

51
Q

What is the role of gravity in blood pressure?

A

Maintains a pressure gradient allowing blood to flow from heart to the feet

52
Q

Is blood pressure above the heart greater than below the heart?

A

Blood pressure above the heart is less than below it

53
Q

What is postural hypotension?

A

When blood pools in your feet/ venous system below your heart as you are sitting down
Reduces blood flow to head when you stand up (may faint)

53
Q

What is postural hypotension?

A

When blood pools in your feet/ venous system below your heart as you are sitting down
Reduces blood flow to head when you stand up (may faint)

54
Q

What is the average cardiac output for the average 70kg male?

A

5 L/min

CVS (21 decks)

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