Laminar and turbulent flow Flashcards

1
Q

what is the relationship between pressure, flow and resistance in the cardiovascular and respiratory system?

A

Flow = pressure / resistance

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2
Q

How can we calculate the flow of the cardiovascular system?

A

CO = blood pressure (ABP - CVP) / resistance (TPR)

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3
Q

How can we calculate the flow of the respiratory system?

A

Air flow = pressure gradient (PB - PA) / Airway resistance (Raw)

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4
Q

What factors determine flow?

A

Radius (airway/blood vessel)
Viscosity of fluid (air/blood)
Length (of airway or blood vessels)

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5
Q

What is flow proportional to?

A

Driving pressure
RS - dependent on work of chest wall muscles
CVS - dependent on cardiac work

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6
Q

What is flow inversely proportional to?

A

Resistance

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7
Q

What is the haematocrit?

A

Proportion of red blood cells compared to the total volume of blood plasma

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8
Q

What does a change in the radius do to resistance?

A

An increase in the radius from 1 to 2 will reduce the resistance 16 fold (2^4)

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9
Q

How do we physiologically control the radius of airways or blood vessels?

A

RS - bronchoconstriction/dilation

CVS - vasoconstriction/dilation

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10
Q

What does poiseuilles law only apply to?

A

Only applicable to laminar flow

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11
Q

What is laminar flow?

A

Organised parabolic flow profile

Formed through layers being set up within the vessel/airway.

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12
Q

What are the layers that set up laminar flow?

A

Immobile layer
blood layers slipping over each other (each successive layer slips past faster than the previous one)
flow is fastest at the vessel centre

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13
Q

What is turbulent flow?

A

Disorganised flow
No structured pattern
Cross-currents that uses up loads of kinetic energy in the set up of the random flow patterns

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14
Q

Why is turbulent flow less energy efficient?

A

Requires more energy to set up cross-flows and currents to mix the fluid streams and therefore energy is used up. Some energy is lost as sound.

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15
Q

What is the relationship between laminar and turbulent flow and resistance?

A

Laminar flow - Inversely proportional to resistance

Turbulent flow - inversely proportional to the square root of resistance

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16
Q

what factors determine whether flow is laminar or turbulent?

A

Turbulent flow has a high value Reynolds number.

17
Q

What factors decrease turbulence?

A

Viscosity of the fluid.

more viscous makes the flow less turbulent.

18
Q

What does a Reynolds number <2000 mean

A

Most likely to be laminar flow.

>2000 more likely to be turbulent flow

19
Q

Where is turbulent flow found in the respiratory system?

A

Turbulent airflow - Trachea since there is a high velocity and large radius.

20
Q

What is transitional air flow?

A

Mixture of flow types (most of the branchial tree is transitional)

21
Q

Where is laminar flow found in the respiratory system?

A

Very small airways since there is a low velocity of fluid here.

22
Q

Where is laminar flow found in the cardiovascular system

A

in most blood vessels (but vessel branches disrupt causing eddy currents)
RBCs form concentric layers

23
Q

What is the key idea about laminar flow?

A

The idea that laminar flow is highly energy efficient and SILENT

24
Q

Where is turbulent flow found in the cardiovascular system

A

Where there is an irregularity in a blood vessel (eg at the valves)
When the blood velocity is high (aorta)
When there is stenosis (narrowing of blood vessels)
Branch points in vessels

25
Q

What is a murmur?

A

When there is turbulent flow which sets up reverberations in the ventricle which you can hear.
(eg at valves)

26
Q

What can turbulent flow be used to measure?

A

Sounds (murmurs)

Blood pressure

27
Q

What is Poiseuille relationship?

A

Flow rate is proportional to the radiuse^4 of the vessel

28
Q

What is Reynolds number?

A

Determines if you have laminar or turbulent flow
<2000 = laminar flow
> 2000 = more likely to have turbulent
>3000 = definite turbulent flow

29
Q

Where is laminar flow at its maximum velocity?

A

In the centre of the tube

30
Q

What factors increase turbulance?

A

Factors increasing turbulence:
Density of fluid
Diameter of the tube
velocity of the flow

31
Q

What causes Bronchoconstriction?

A

ACh released from parasympathetic nervous system.

32
Q

What causes Brochodilation?

A

Circulating adrenaline binding to the beta 2 receptors on the airway smooth muscle.

33
Q

What causes vasoconstriction?

A

Increasing sympathetic activity releasing Noradrenaline binding to alpha receptors on smooth muscle.
NO released by shear stress.