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Semester 2 Cardiovascular System > L3: Haemodynamics > Flashcards

L3: Haemodynamics Flashcards

1
Q

What is serum?

A

Plasma without the clotting factors

Clear yellowish liquid

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2
Q

Does blood viscosity changes much?

A

Changes are relatively uncommon
Diseases –> Polycythaemia (↑RBCs), Thrombocythaemia (↑platelets) leukaemia (↑WBCs)
Thick blood –> dry gangrene in peripheries

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3
Q

What causes plasma viscosity to change?

A

Minor changes
Typically from acute phase proteins (CRP, fibrinogen, complement)
Indicates inflammation

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4
Q

What does haemodynamics mean?

A

Movement of blood

Metabolic demand dictate flow

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5
Q

What causes blood to move?

A

Moves from areas of high pressure to areas of low pressure

Pressure gradient required for movement

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6
Q

Define laminar flow?

A

Smooth flow
Maintaining energy
Most common

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7
Q

Define turbulent flow?

A

Disorganised flow
Loss of energy
Pressure increased beyond point where it can flow linearly- flow decreases

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8
Q

Define flow?

A

volume transferred per unit time (L/min)

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9
Q

Define pressure?

A

Force per unit area (mmHg) –> in blood

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10
Q

Why does the flow and pressure pulsate?

A

To model steady flow and pressure column

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11
Q

What is the relationship between flow and resistance?

A

Inverse relationship ↑resitance ↓flow

Resistance= difficulty of flow

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12
Q

How are pressure, flow and resistance related?

A

Flow= Pressure / resistance

If resistance increases, flow the same, then pressure must increase

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13
Q

What affects the resistance?

A

Diameter, length of vessel and viscosity
Diameter- most important
Length of vessel (constant)
Viscosity (constant)

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14
Q

Why does the diameter have the biggest impact on resistance?

A

Radius raised to 4th power (simplified R= 1/r^4)
19% decrease in radius –> half the blood flow
Small changes= big impact

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15
Q

What causes the radius/diameter of blood vessel to change?

A

Vasoconstriction and vasodilation

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16
Q

What is the relationship between pressure and resistance?

A

Proportional

Change in pressure= change in resistance

17
Q

What structure causes the biggest change in resistance/pressure?

A 
Arterioles--> biggest jump in pressure across vessel class
Small arteries and arterioles contribute greatest component of TPR
18
Q

How does pressure and resistance change in the CVS?

A 
Pulmonary circulation (heart to lungs) lower pressure than systemic
Short and wider vessels

Longer vessel- greater resistance reduced flow
Short- resistance decrease flow increases
Increased diameter, reduced resistance
Reduced diameter, increases resistance

19
Q

Define velocity?

A

The distance fluid moves in a given time (and direction) (cm/s)

20
Q

What is the relationship between flow, velocity and radius?

A

(flow= volume per unit time → therefore the quicker the blood moves more flow)
Flow= Velocity x Area
Area= πr^2
therefore Velocity is inversely related to radius
F= V x r^2
flow is constant
V =1/r^2

Squeeze a hose pipe, radius decreases, velocity that water shoots out increases

21
Q

How is the relationship between flow, velocity and radius demonstrated in the vasculature?

A

Capillaries= largest SA (radius) = slowest velocity
Allows diffusion

Large number of capillaries

22
Q

What is the pulse pressure?

A

Systolic blood pressure - diastolic blood pressure

23
Q

How is the mean arterial pressure calculated?

A 
MAP= Diastolic blood pressure + (systolic blood pressure - diastolic blood pressure)/3) 
MAP = DBP + (SBP-DBP)/3
Time weighted
OR
MAP = CO x TPR
24
Q

What is total peripheral resistance? How is it calculated

A

Total resistance in the systemic circulation

TPR= ( Mean aortic pressure (SBP) - central venous pressure (DBP) ) / Cardiac output

25
Q

What determines pulse pressure?

A

(pulse pressure- pressure of the blood ejected from the heart)
Compliance of arterial system (ability to expand to accommodate increased blood volume)
Volume of blood ejected

26
Q

What actually is your pulse?

A

Shock wave that arrives slightly before the blood itself

27
Q

What causes the pulse pressure to increase?

A

Heart block - brachycardia–> more time in filling phase so larger volume ejected each beat (↑stroke volume)
Vasodilation –> decreased peripheral resistance so diastolic pressure will drop as more of the blood ejected out the heart (more volume to fill)
Elite athletes –> systolic increased (bigger heart muscle so increased output), diastolic decreased (more of the blood ejected out the heart)
Age and atherosclerosis –> stiffening of the vessels, reduced compliancy of vessels

28
Q

To record blood pressure what features of blood flow does it rely on?

A

Smooth laminar flow –> silent

Turbulent flow–> noisy

29
Q

What is the name of the sounds you are listening for when taking a blood pressure?

A

Korotkoffs sounds

30
Q

What is the difference between thrill and bruit

A

Thrill –> felt
Bruit –> heard

Turbulent flow

31
Q

Describe the basis of taking a blood pressure?

A

Pressure cuff–> occludes blood pressure
Release air
Sound–> turbulent flow –> Korotoff sounds –> systolic blood pressure = pressure in cuff
No sound–> laminar flow–> diastolic pressure=pressure in cuff

32
Q

What is important to remember when taking blood pressure?

A

Cuff size –> small = over estimation, large = under estimation
Positioning of cuff
Measure both arms –> use higher as reference point
Safe comfortably, upright, legs uncrossed, feet on ground
Arm supported
Repeat –> mean taken
Taken at level of the heart

33
Q

What are the effects of gravity on blood pressure?

A

Below level of heart–> pressure increased
Above level of the heart–> pressure decreased
Gravity maintains pressure gradient allowing blood to flow from heart to foot when standing
Pooling–> below heart

34
Q

What causes dizziness upon standing?

A

Postural hypotension
↓ SV
transient arterial hypotension
Baroreceptors not detected change

Semester 2 Cardiovascular System (21 decks)

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