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BMS 242 - CVS respiratory > Respiration I > Flashcards

Respiration I Flashcards

1
Q

In normal conditions of lamina flow, what is the movement of air proportional to?

A

The PRESSURE GRADIENT

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2
Q

In normal conditions of lamina flow, what is the movement of air inversely proportional to?

A

The RESISTANCE

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3
Q

What is the total volume of air into the lungs at normal lamina flow proportional to?

A

DIFFERENCE in PRESSURE / Resistance

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4
Q

How do you calculate the ‘difference in pressure’?

A

Pressure in the ALVEOLI - pressure in the ATMOSPHERE

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5
Q

What is laminar flow?

A

STEADY flow down a tube in UNIFORM speed and direction

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6
Q

Describe the flow speed in laminar flow?

A

In the centre of the tube - maximum speed

As go to the edge of the tube - flow rate drops off in linear fashion

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7
Q

Where does laminar flow occur?

A

In the smaller airways

  • TERMINAL BRONCHIOLES
  • ALVEOLAR DUCTS
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8
Q

When does turbulent flow occur?

A

When air reaches CRITICAL VELOCITY in a the and starts to become IRREGULAR and TUMBLES

In the higher airways:

  • TRACHEA
  • BRONCHI
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9
Q

What is the flow rate in the turbulent airways proportional to?

A

SQUARE ROOT of the pressure gradient

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10
Q

With what type of air flow is it more difficult to get air into the lungs and why?

A

Turbulent flow:
- Proportional to sq rt and pressure gradient

  • Need larger changes in the pressure gradient to produce same changes in flow rate at laminar flow (proportional to pressure gradient)
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11
Q

With what type of air flow is it more difficult to get air into the lungs and why?

A

Turbulent flow:
- Proportional to sq rt and pressure gradient

  • Need larger changes in the pressure gradient to produce same changes in flow rate at laminar flow (proportional to pressure gradient)
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12
Q

What is the relationship between FLOW under laminar or turbulent conditions?

A

At LOW driving pressures: not much difference between the different flows

As the driving pressure increases:

  • Laminar flow increases in LINEAR fashion
  • Turbulent flow increases at a LOWER rate and PLATEAUS
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13
Q

When does transitional flow occur?

A

In airways that are:

  • Bumpy
  • Continuously BRANCHING
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14
Q

What occurs in terms of flow at a branch point?

A

Movement from laminar flow to transitional flow

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15
Q

How do you determine the flow type?

A

By the Reynolds number

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16
Q

What is the calculation for Reynolds number?

A

Re = 2rvp/n

Where:
2 - radius 
v - velocity 
p - density 
n - viscosity
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17
Q

What is viscosity?

A

How thick/sticky a substance is

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18
Q

What Re determines LAMINAR flow?

A

LOW:

<1000

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19
Q

What Re determines TURBULENT flow?

A

HIGH:

>1500

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20
Q

What Re determines UNSTABLE flow?

A

In between 1000-1500

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21
Q

What is unstable flow?

A

Switching between laminar and turbulent (transitional?)

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22
Q

What is the ‘real’ value for laminar flow in the lungs?

Why?

A

Re = 1

Lungs in the airways aren’t smooth

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23
Q

Describe the air flow in the lungs

A
  • Velocity slightly goes up in the first few branches as the cross-sectional area slightly decreases

As go through the lungs:

  • Cross-sectional area in the lungs INCREASE
  • Velocity of the gas decreases
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24
Q

What happens at generation 16 of branching of the airways?

What does this do to the VELOCITY of flow in the lungs?

Why?

A

Conversion between the CONDUCTING ZONE and the RESPIRATORY ZONE

  • Cross-sectional area INCREASES DRAMATICALLY
  • Huge drop off in VELOCITY

Velocity decrease as easier to get the same volume of gas to the same place - doesn’t have to travel as fast (more travel through at the same time)

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25
Q

Why does the velocity decrease when the cross-sectional area increases?

A

Same volume of blood must get to the same place in the same amount of time - must travel faster

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26
Q

At generation 16 of branching, what speed does the air move at?

A

Moves at 1.5% speed it did when it came into the body

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27
Q

What is the Re in the alveoli?

A

Very low - laminar flow

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28
Q

What is the IMPACT of RESISTANCE on FLOW determined by?

Describe this

A

POISEULLE’S LAW:
Resistance is INVERSELY proportional to r^4
Where r - radius
(Resistance = 1/r^4)

So, very small changes in the radius have a very large impact on the resistance

Large impact on flow rate as flow rate is linked to resistance through V = change in pressure/resistance

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29
Q

What happens to the FLOW RATE when the radius increase?

What happens to the velocity?

A

Flow rate increases

Velocity decrease

30
Q

What happens to the FLOW RATE when the radius decrease?

What happens to the velocity?

A

Flow rate decreases

Velocity increase

31
Q

When is the relationship between radius and flow rate more exaggerated?

A

In TURBULENT flow

32
Q

What is the total airway resistance in a normal person?

A

1.5cm H20 .s.litres^-1

33
Q

Where in the respiratory system does most of the resistance in the lungs come from?

Why is this not the other way around?

A

In the upper airways (where there is a large diameter)

In the large airways - airways are in SERIES, so the resistance adds together (R1 + R2 + R3…)

In the smaller airways - airways are in PARALLEL, so the INVERSE of the resistances are added together (1/R1 + 1/R2 + 1/R3…)

34
Q

What occurs in COPD patients?

What causes this?

A

Large increase in the TOTAL airway resistance

Caused by:

  • Inflammation in the LOWER AIRWAYS
  • Causing a huge increase in the resistance of the SMALLER airways
35
Q

What is the increase in airway resistance in COPD patients?

A

Increase from 1.5 cm H2O .s.litre^-1 to 5.0cm H2O.s.litre^-1

36
Q

What is the increase in the contribution of the lower airways in COPD patients?

A

From 20% contribution to 70% contribution

37
Q

What 2 factors increase resistance of the airways?

How?

A

1) Increased mucus secretin
2) Oedema

Both decrease the diameter - increasing the resistance

38
Q

What is oedema?

A

Increase fluid retention

39
Q

How does oedema increase resistance of the airways?

A

Causes swelling
Build up of interstitial fluid
Compresses the airways

40
Q

What effect does inspiration have on resistance?

Why?

A

REDUCES resistance

Causes DILATION of the airways

41
Q

What effect does expiration have on resistance?

Why?

A

INCREASES resistance

Causes CONSTRICTION of the airways

42
Q

What is FRC?

A

Functional residual capacity

43
Q

When is FRC measured?

A

At the end of a NORMAL expiration

44
Q

Describe the pressure gradient at the end of a normal expiration (at FRC)

A

No pressure gradient:

  • No movement of air (resting state)
  • Alveolar pressure is at 0 (relative to the atmosphere)
45
Q

What is the pressure in the intapleural space at rest?

Why?

A

Subatmospheric (LOWER than that of the atmosphere)

Expansion of the chest wall balances the collapse of the lung

46
Q

What is transpulmonary pressure (Ptp)?

A

The DIFFERENCE between the ALVEOLAR pressure and the INTRAPLEURAL pressure

47
Q

Where is the intrapleural pressure?

A

In the pleural cavity

48
Q

What is the Ptp at residual capacity (no airflow)

A

FIXED at +5 at a specific volume of the alveoli

49
Q

What is the transmural pressure (Ptm)?

A

Difference between the pressure in the BRANCHES of the airways and the pressure in the pleural cavity (INTRAPLEURAL pressure)

50
Q

What is Ptm at residual capacity?

A

+5

51
Q

What is Ptm equal to?

A

Paw (airway pressure) - Pip (intrapleural pressure)

52
Q

What must the Pa (Alveolar pressure) be for inspiration to occur?

A

SUBatmospheric (lower than that of atmospheric pressure)

MINUS value

53
Q

What must the Pa (Alveolar pressure) be for expiration to occur?

A

MORE than the atmosphere

POSITIVE value

54
Q

What is the Ptm fixed at at a specific volume of alveoli?

A

+5

55
Q

What is Pip?

What is it equal to?

A

Intrapleural pressure

Pip = Pa - Ptm
= -Transmural pressure - alveolar pressure

56
Q

What is Ptp?

What is it equal to?

A

Transplural pressure

Ptp = Pa - Pip
= Alveolar pressure - intraplural pressure

57
Q

What is Ptm?

What is it equal to?

A

Transmural pressure

Ptm = Paw - Pip
= Airway pressure - intraplural pressure

58
Q

What is the Pip if Pa is -15?

Why?

A

-20

Ptp = Pa - Pip

As Ptp is fixed at +5

59
Q

What happens to the Paw during INSPIRATION as move from the inside to the outside of the lungs?

What impact does this have on the pressure gradient?

A

It becomes more POSITIVE

Pressure gradient with the atmosphere DECREASES

60
Q

What happens to the Ptm as the Paw becomes positive?

Why?

What does this cause?

A

The Ptm becomes a higher positive

As Ptm = Paw - Pip

Causes:

  • Airways to expand
  • Decrease in resistance
  • Air moves into the lungs
61
Q

What happens to the Paw during EXPIRATION as move from the inside to the outside of the lungs?

What impact does this have on the pressure gradient?

A

It becomes more NEGATIVE

Pressure gradient with the atmosphere INCREASES

62
Q

What happens to the Ptm as the Paw becomes less positive?

Why?

What does this cause?

A

It eventually becomes NEGATIVE

As Ptm = Paw - Pip

Causes:

  • Airways to COMPRESS
  • Increase in resistance
  • Air moves OUT of the lungs
63
Q

What is exaggerated in emphysema?

Why?

A

The compression effect of expiration

Loss of the elastic tissue (elastin) in the alveoli
Loose tethering of the alveoli to the airways - normally keeps the airways open

64
Q

In emphysema what is the resting lung volume in comparison to normal patients?

What is the resistance? Why?

A

HIGHER resting volume

Resistance increases - compression effect of expiration increases

65
Q

In emphysema, what can happen during forced expiration?

A

Airways can collapse

66
Q

What happens to the airway resistance as breath in?

Why?

A

Decreases

Due to the diameter of the tubes increasing

67
Q

What happens to the airway resistance as breath ou?

Why?

A

Increases

Due to the diameter of the tubes decreasing

68
Q

What is the difference between normal patients reaching tidal volume and patients with COPD?

A

After 1 second in normal patient:
- Lungs reach tidal volume

COPD:
- Only 60% tidal volume

69
Q

During inspiration, is the intrapleural pressure positive or negative?

Why?

A

Negative

So that the airways can expand (surrounds the airways)

70
Q

During expiration, is the intrapleural pressure positive or negative?

Why?

A

Positive

So that the airways constrict (surrounds the airways)

71
Q

Why does Paw become more positive during inspiration?

A

So that the aw can expand and fill with air

72
Q

Why does Paw become more negative during expiration?

A

So that the aw can constrict and expel the air out

BMS 242 - CVS respiratory (15 decks)

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