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CVRS > L12 Laminar and Turbulent flow > Flashcards

L12 Laminar and Turbulent flow Flashcards

1
Q

How to work out Flow

A

Flow = pressure / resistance

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2
Q

from what pressures does the air or the blood flow to

A

from high pressure to low pressure

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3
Q

How to work out BP

A

Arterial blood pressure - cardiac venous pressure

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4
Q

how to work out CO

A

BP/ resistance (TPR)

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5
Q

what is the resistance in the CVRS

A

It’s the vascular resistance in the vascular beds (vessels)

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6
Q

work out Air flow ?

A 
pressure gradient (batometric pressure - alveolar pressure)/ airway resistance 
- the pressure gradient needs to be bigger than the resistance so the air can flow during inspiration
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7
Q

During inspiration, what is the pressure gradient like so is it PB > PA or PA

A

PB > PA

-this allows the air to flow inside

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8
Q

during Expiration, what is the pressure gradient like so is it PB > PA or PA

A

PA>PB

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9
Q

what is the resistance in the RS

A

in the airways of the lungs

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10
Q

is the resistance greater in CVS or RS?

A
  • the resistance is greater in the CVS because there is a greater driving force generated in the CVS.
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11
Q

What is the formula for Poiseuille’s law

A

V dot = change in P x ((pi x r^4)/8nl)

- this formula only applies to laminar flow

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12
Q

what is flow proportional to

A

driving pressure so

  • for RS, it’s PB-PA depending on the chest wall muscles
  • for CVS, it’s ABP-CVP, depending on cardiac work
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13
Q

What is flow inversely proportional to

A

-resistance
so R = 8nl/pi x r^4
- viscosity(n) is constant, can be changed by heliox or haematocrit
- the length of the blood vessels set up by the anatomy so cant change it
- radius (r) is dependent on the smooth muscle so we have physiological control over it so like (bronchodilation/constriction for RS and vasodilation/constriction for CVS)

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14
Q

what is resistance inversely proportional to?

A
  • R = 1/ r^4
  • as the radius increases, the R will decrease
    • radius (r) is dependent on the smooth muscle so we have physiological control over it so like (bronchodilation/constriction for RS and vasodilation/constriction for CVS)
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15
Q

what is laminar flow and describe the velocities of the flow

A
  • It’s a flow where the centre of the flow has the max velocity
  • the outermost layer of the flow nearest to the vessel wall is the fluid that is immobile
  • after that, each successive layers from fluid layer to the centre, it increases in speed
  • it has a parabolic flow pattern
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16
Q

What is LF inversely proportional to ?

A
  • to R

- so it’s energy efficient and in order so it’s silent flow

17
Q

What is turbulent flow (TF)

A
  • it’s a random flow where tje parabolic pattern is lost
    -the fluid and blood mixes so it’s noisy
    -less energy effecient because we lose KE
    so the energy is lost of sound
18
Q

What is TF inervsely proportional to

A

square root of chnage in pressure

19
Q

What factor can determine whether it’s TF or LF

A 
Reynolds number (NR)
- NR =( density x diameter x velocity ) / viscosity
20
Q

What factors can increase occurrence of TF

A
  • density
  • diameter of the tube
  • velocity of the flow
21
Q

What factor can decrease the TF

A
  • viscosity

- so if the viscosity is higher, the TF occurs less often

22
Q
  • Where does TF occur in the RS and why?
A
  • in the trachea
  • because there is a higher velocity and large radius, contributing to an increase of NR
  • Energy is lost so the flow is no longer proportional to change in Pressure
  • but the flow is now proportional to square root of change in Pressure
23
Q

what flow occurs in the bronchial tree

A
  • both TF and LF
24
Q

What flow occurs in small airways

A

LF

25
Q

Where does LF occur in the CVRS

A
  • most blood vessels where the RBCs would be at the centre of the vessel at the max velocity
26
Q

Where does TF occur in CVS

A

in the vessels where there is an irregularity so like valves, clots, blood vessel branches

27
Q

Why does narrowing of blood vessels lead to increases flow velocity

A

Velocity = Flow/ CSA

so if the CSA decreases, the velocity increases

28
Q

normal Indicators for TF

A
  • herat sounds caused by closing of the AV and SLV

-

29
Q

What is a murmur caused by the TF

A
  • it’s when the area of the vessel is smaller than usual like the valves are fused together
  • this leads to higher velocity because it needs to compensate for the same flow
  • causing more TF than usual
30
Q

How can a cuff measures the systolic and diastolic pressure ?

A
  • when the cuff is first used, it stops the flow because it is tight
  • but as the cuff is gradually released, it produces sounds as the flow becomes turbulent due to the tightening of the cuff
  • so the systolic pressure is when the korotkoff sounds start happening and diastolic pressure is when it stops
  • after wards, the cuff becomes loose and the flow becomes laminar soon after

CVRS (19 decks)

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