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BMS 242 - CVS respiratory > Respiration I > Flashcards

Respiration I Flashcards

(72 cards)

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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
Why does the velocity decrease when the cross-sectional area increases?
Same volume of blood must get to the same place in the same amount of time - must travel faster
26
At generation 16 of branching, what speed does the air move at?
Moves at 1.5% speed it did when it came into the body
27
What is the Re in the alveoli?
Very low - laminar flow
28
What is the IMPACT of RESISTANCE on FLOW determined by? Describe this
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
29
What happens to the FLOW RATE when the radius increase? What happens to the velocity?
Flow rate increases Velocity decrease
30
What happens to the FLOW RATE when the radius decrease? What happens to the velocity?
Flow rate decreases Velocity increase
31
When is the relationship between radius and flow rate more exaggerated?
In TURBULENT flow
32
What is the total airway resistance in a normal person?
1.5cm H20 .s.litres^-1
33
Where in the respiratory system does most of the resistance in the lungs come from? Why is this not the other way around?
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
What occurs in COPD patients? What causes this?
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
What is the increase in airway resistance in COPD patients?
Increase from 1.5 cm H2O .s.litre^-1 to 5.0cm H2O.s.litre^-1
36
What is the increase in the contribution of the lower airways in COPD patients?
From 20% contribution to 70% contribution
37
What 2 factors increase resistance of the airways? How?
1) Increased mucus secretin 2) Oedema Both decrease the diameter - increasing the resistance
38
What is oedema?
Increase fluid retention
39
How does oedema increase resistance of the airways?
Causes swelling Build up of interstitial fluid Compresses the airways
40
What effect does inspiration have on resistance? Why?
REDUCES resistance Causes DILATION of the airways
41
What effect does expiration have on resistance? Why?
INCREASES resistance Causes CONSTRICTION of the airways
42
What is FRC?
Functional residual capacity
43
When is FRC measured?
At the end of a NORMAL expiration
44
Describe the pressure gradient at the end of a normal expiration (at FRC)
No pressure gradient: - No movement of air (resting state) - Alveolar pressure is at 0 (relative to the atmosphere)
45
What is the pressure in the intapleural space at rest? Why?
Subatmospheric (LOWER than that of the atmosphere) Expansion of the chest wall balances the collapse of the lung
46
What is transpulmonary pressure (Ptp)?
The DIFFERENCE between the ALVEOLAR pressure and the INTRAPLEURAL pressure
47
Where is the intrapleural pressure?
In the pleural cavity
48
What is the Ptp at residual capacity (no airflow)
FIXED at +5 at a specific volume of the alveoli
49
What is the transmural pressure (Ptm)?
Difference between the pressure in the BRANCHES of the airways and the pressure in the pleural cavity (INTRAPLEURAL pressure)
50
What is Ptm at residual capacity?
+5
51
What is Ptm equal to?
Paw (airway pressure) - Pip (intrapleural pressure)
52
What must the Pa (Alveolar pressure) be for inspiration to occur?
SUBatmospheric (lower than that of atmospheric pressure) MINUS value
53
What must the Pa (Alveolar pressure) be for expiration to occur?
MORE than the atmosphere POSITIVE value
54
What is the Ptm fixed at at a specific volume of alveoli?
+5
55
What is Pip? What is it equal to?
Intrapleural pressure Pip = Pa - Ptm = -Transmural pressure - alveolar pressure
56
What is Ptp? What is it equal to?
Transplural pressure Ptp = Pa - Pip = Alveolar pressure - intraplural pressure
57
What is Ptm? What is it equal to?
Transmural pressure Ptm = Paw - Pip = Airway pressure - intraplural pressure
58
What is the Pip if Pa is -15? Why?
-20 Ptp = Pa - Pip As Ptp is fixed at +5
59
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?
It becomes more POSITIVE Pressure gradient with the atmosphere DECREASES
60
What happens to the Ptm as the Paw becomes positive? Why? What does this cause?
The Ptm becomes a higher positive As Ptm = Paw - Pip Causes: - Airways to expand - Decrease in resistance - Air moves into the lungs
61
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?
It becomes more NEGATIVE Pressure gradient with the atmosphere INCREASES
62
What happens to the Ptm as the Paw becomes less positive? Why? What does this cause?
It eventually becomes NEGATIVE As Ptm = Paw - Pip Causes: - Airways to COMPRESS - Increase in resistance - Air moves OUT of the lungs
63
What is exaggerated in emphysema? Why?
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
In emphysema what is the resting lung volume in comparison to normal patients? What is the resistance? Why?
HIGHER resting volume Resistance increases - compression effect of expiration increases
65
In emphysema, what can happen during forced expiration?
Airways can collapse
66
What happens to the airway resistance as breath in? Why?
Decreases Due to the diameter of the tubes increasing
67
What happens to the airway resistance as breath ou? Why?
Increases Due to the diameter of the tubes decreasing
68
What is the difference between normal patients reaching tidal volume and patients with COPD?
After 1 second in normal patient: - Lungs reach tidal volume COPD: - Only 60% tidal volume
69
During inspiration, is the intrapleural pressure positive or negative? Why?
Negative So that the airways can expand (surrounds the airways)
70
During expiration, is the intrapleural pressure positive or negative? Why?
Positive So that the airways constrict (surrounds the airways)
71
Why does Paw become more positive during inspiration?
So that the aw can expand and fill with air
72
Why does Paw become more negative during expiration?
So that the aw can constrict and expel the air out

BMS 242 - CVS respiratory (15 decks)

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