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FBS2 > Lung mechanics 2 > Flashcards

Lung mechanics 2 Flashcards

1
Q

How do you measure lung compliance?

A

Work out change in volume (spirometer) and change in pressure
alveolar pressure = 0, intrapleural pressure measured by oesophageal balloon
delta V/delta P

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2
Q

What are the axes for a static pressure volume loop calculating lung compliance?

A

x axis = pressure

y axis = volume

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3
Q

Which of inspiration and expiration causes the lungs to have a greater volume for the same pressure?

A

Expiration

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4
Q

When do the lungs have minimum compliance?

A

High and low volumes

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5
Q

When do the lungs have maximum compliance?

A

Around normal tidal volume

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6
Q

What is a typical value for lung compliance in an adult male?

A

1.5L/kPa

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7
Q

What kind of compliance does a stiff lung have?

A

Low compliance

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8
Q

What kind of compliance does a fibroses lung (e.g. asbestosis) have?

A

Low compliance

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9
Q

What kind of compliance does the lung of an emphysema patient have?

A

High compliance (tissue destruction - becomes floppy)

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10
Q

What diseases make up COPD?

A

Chronic bronchitis

Emphysema

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11
Q

What occurs in bronchiolitis?

A

Thick, narrow bronchioles with excess mucus

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12
Q

What occurs in emphysema?

A

Destruction of alveolar walls

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13
Q

What gives the lung elastic resistance?

A

Elastin and collagen

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14
Q

How can you stretch an air-fluid interface?

A

Overcome its surface tension

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15
Q

What is the La Place equation? (surface tension)

A 
P = 2T/R
(R = radius)
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16
Q

If there is high surface tension on a bubble what does it want to do?

A

Collapse in (more pressure)

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17
Q

If the bubble has a bigger radius, is it more or less likely to collapse inwards?

A

Less likely

Pressure decreases when radius increases

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18
Q

What do we need to do to prevent small alveoli in the lung collapsing inwards?

A

Reduce the surface tension

19
Q

What does surfactant do?

A

Reduces the surface tension and increases compliance (stops alveoli collapsing in on themselves)

20
Q

What is surfactant produced by?

A

Type II alveolar cells

21
Q

What is surfactant made up of?

A

Phospholipids and surfactant proteins

22
Q

How does surfactant work?

A

The phospholipids have a hydrophobic and a hydrophilic end

They stop the water molecules getting close together

23
Q

What kind of alveoli is surfactant at high concentration?

A

Small alveoli

24
Q

What is transudation?

A

Fluid being sucked into alveoli

25
Q

What causes neonatal respiratory distress syndrome?

A

Inadequate surfactant production in premature babies

- increased work of breathing (low lung compliance)

26
Q

What is alveolar dependency?

A

Alveoli join together (also prevents collapse)

27
Q

What is restrictive lung disease?

A

Resistance to stretch of alveoli

28
Q

What is obstructive lung disease?

A

Difficulty in air flowing through tubes (airways resistance)

Tubes narrow

29
Q

Give examples of obstructive lung diseases

A

asthma
bronchiolitis/ chronic bronchitis
emphysema
COPD

30
Q

Give examples of restrictive lung diseases

A

Fibrosis of the lung
Respiratory muscle weakness
Phrenic nerve damage
TB

31
Q

In which obstructive lung diseases are the alveoli fine?

A

Asthma and chronic bronchitis

32
Q

How can you measure lung function in clinic?

A 
Peak flow (forced expiratory flow)
Spirometry
33
Q

What is FEV1?

A

Forced expiratory volume in 1 second

34
Q

What is FVC?

A

Forced vital capacity

35
Q

What is a normal FEV1/FVC ratio?

A

Over 75%

36
Q

What happens to the FEV1/FVC ratio in obstructive disease?

A

Decreases (FEV1 very very low)

37
Q

What happens to the FEV1/FVC ratio in restrictive disease?

A

It is normal (or even higher)

both FEV1 and FVC decrease

38
Q

What is the hallmark of restrictive lung disease?

A

Low vital capacity

39
Q

What does a maximum flow-volume loop look like in COPD patient?

A

Concave inwards

40
Q

What does a maximum flow-volume loop look like in restrictive lung disease patient?

A

No concave section

Just small loop, otherwise normal

41
Q

How does asthma effect compliance?

A

No effect

42
Q

What happens to the FRC in a fibrosed lung?

A

Reduced because increased lung recoil

43
Q

What happens to the FRC in the lung of an emphysema patient?

A

Increased because decreased lung recoil

–> barrel chest

FBS2 (16 decks)

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