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Mustafa respiratory > 4 Compliance > Flashcards

4 Compliance Flashcards

1
Q

What do type 2 alveolar cells produce?

A

Surfactant, A detergent like fluid

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2
Q

What is the function of surfactant?

A

Reduces surface tension on alveolar surface membranes
Reduces chance they collapse.

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3
Q

What causes alveolar surface tension?

A

Occurs in air-water interface
Attraction between water molecules

Attraction between surface molecules balances out with a net inward pull

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4
Q

How does surfactant affect compliance?

A

It increases compliance (distensibility) effectively making breathing easier

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5
Q

Where is surfactant most effective?

A

On small alveoli
Surfactant molecules get closer & more concentrated

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6
Q

Why is pressure greater in smaller alveoli?

A

P = (2 x surface tension)/radius
Smaller alveoli have smaller radius & same surface tension

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7
Q

When is surfactant produced in embryo?

A

Starts ~25 weeks
Complete by ~36 weeks

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8
Q

What surfactant related syndrome is often suffered by premature babies?

A

IRDS
Infant Respiratory Distress Syndrome

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9
Q

What stimulates surfactant production?

A

Thyroid hormones
Cortisol
Both increase towards end of pregnancy

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10
Q

What is compliance?

A

How much the lung volume changes for any given change in Ip pressure

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11
Q

What does high compliance mean?

A

The lung will have a large volume increase for a small intrapleural pressure decrease

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12
Q

How does compliance relate to elasticity & stretchability?

A

Compliance is a measure of stretchability (how easy the lung is to fill with air)
It doesnt tell you anthing about elasticity (how easily the air is pushed out)

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13
Q

Law of Laplace?

A

P = 2T/r
Inwardly directed pressure of alveoli

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14
Q

What kind of alveoli collapse most easily?

A

Smaller alveoli
Inwardly directed pressure is largest
Surfactant combats this

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15
Q

What hapens in IRDS?

A

No surfactant
Very high inward pressure in alveoli
So lots of small alveoli collapse between breaths
Makes it very hard to breath

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16
Q

What alveoli are most efficient?

A

Small alveoli
Have largest surface area to volume ratio

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17
Q

How does age affect compliance?

A

Compliance decreases with age

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18
Q

How do we determine compliance from graphically?

A

Draw a graph of ip against lung volume with a curve for inspiration and one for expiration.

A straight line between them will give the value for compliance from its slope;

19
Q

Why is a curve for inspiration less steep at the start?

A

At start of inspiration tissue inertia, elasticity and surface tension must be overcome.

20
Q

Why is the curve for expiration less steep at the start?

A

Compressing the chest to push out air also compresses the airways and narrows them

Once chest is quite compressed, pressure is high enough to overcome compression and expiration curve steepens

21
Q

What makes expiration passive

A

elastic recoil of lungs

22
Q

What is emphysema?

A

Tissue loses elasticity
Expiration requires more effort and a larger increase in ip pressure to push out all the air

23
Q

What is fibrosis?

A

excess inert fibrous CT means inspiration requires more effort (decreases compliance)

24
Q

How does compliance vary throughout a lung?

A

Greatest compliance at base of lung
Least compliance at apex

25
Q

Why does compliance vary though the lung?

A

Gravity
Alveoli at lung base are squashed by tissue above so are more empty at the end of expiration than at the apex
Therefore on inspiration they are able to inflate more than ones at the apex

This will vary with position, if patient is lying down or upside down

26
Q

What is an obstructive lung disease?

A

Increased airway resistance, especially on expiration.

27
Q

Whats a restrictive lung disease?

A

Restriction of lung expansion

Increase resistance on inspiration

28
Q

Name some obstructive lung diseases?

A

Asthma
COPD
Chronic bronchitis
Emphysema

29
Q

What happens during a restrictive lung disorder?

A

The lung stiffens and has incomplete expansion

30
Q

Name some restrictive lung disorders?

A

Fibrosis
IRDS
Oedema
Pneumothorax

31
Q

What does asbestosis causes?

A

FIbrosis

32
Q

What are the two types of spirometry?

A

Static or dynamic

33
Q

What is Static spirometry?

A

Only volume exhaled is measured

34
Q

Dynamic spirometry?

A

Volume & time exhaled is emasured.

35
Q

What values can be directly measuered by spirometry?

A

Tidal volume
Expiratory
Inspiratory capacity

36
Q

What values can be determined indirectly by spirometry?

A

Inspiratory reserve volume
Vital capacity

37
Q

What values cant be determined by spirometry?

A

Resiudal vlume
Functional residual capacity

38
Q

What is the nomral forced expiratory volume in 1 second?

A

4L (adult male)

39
Q

What is the normal forced vital capacity?

A

5L (adult male)

40
Q

What is normal FEV1/FVC

A

80% (adult male)

41
Q

How does an obstructive lung disease affect FEV1 & FVC?

A

FEV1 is massively reduced
FVC is only a little reduced
So FEV1:FVC drops

42
Q

How does a restrictive lung disease affect FEV1 & FVC?

A

Reduced both
Usually effects FVC more
The % is often the same or higher than normal.

43
Q

What is FEF25-75?

A

FEF over middle 50% of expiration

(FEF = Forced expiratory flow

44
Q

How does FEF differ to FEV1?

A

FEF correlates with FEV1 but with more changes
Indicates early sign of lung disease
FEF has a wider normal range

Mustafa respiratory (12 decks)

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