Lung mechanics 2

Question 1

How do you measure lung compliance?

Answer 1

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

Question 2

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

Answer 2

x axis = pressure

y axis = volume

Question 3

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

Answer 3

Expiration

Question 4

When do the lungs have minimum compliance?

Answer 4

High and low volumes

Question 5

When do the lungs have maximum compliance?

Answer 5

Around normal tidal volume

Question 6

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

Answer 6

1.5L/kPa

Question 7

What kind of compliance does a stiff lung have?

Answer 7

Low compliance

Question 8

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

Answer 8

Low compliance

Question 9

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

Answer 9

High compliance (tissue destruction - becomes floppy)

Question 10

What diseases make up COPD?

Answer 10

Chronic bronchitis

Emphysema

Question 11

What occurs in bronchiolitis?

Answer 11

Thick, narrow bronchioles with excess mucus

Question 12

What occurs in emphysema?

Answer 12

Destruction of alveolar walls

Question 13

What gives the lung elastic resistance?

Answer 13

Elastin and collagen

Question 14

How can you stretch an air-fluid interface?

Answer 14

Overcome its surface tension

Question 15

What is the La Place equation? (surface tension)

Answer 15

P = 2T/R
(R = radius)

Question 16

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

Answer 16

Collapse in (more pressure)

Question 17

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

Answer 17

Less likely

Pressure decreases when radius increases

Question 18

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

Answer 18

Reduce the surface tension

Question 19

What does surfactant do?

Answer 19

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

Question 20

What is surfactant produced by?

Answer 20

Type II alveolar cells

Question 21

What is surfactant made up of?

Answer 21

Phospholipids and surfactant proteins

Question 22

How does surfactant work?

Answer 22

The phospholipids have a hydrophobic and a hydrophilic end

They stop the water molecules getting close together

Question 23

What kind of alveoli is surfactant at high concentration?

Answer 23

Small alveoli

Question 24

What is transudation?

Answer 24

Fluid being sucked into alveoli

Question 25

What causes neonatal respiratory distress syndrome?

Answer 25

Inadequate surfactant production in premature babies | - increased work of breathing (low lung compliance)

Question 26

What is alveolar dependency?

Answer 26

Alveoli join together (also prevents collapse)

Question 27

What is restrictive lung disease?

Answer 27

Resistance to stretch of alveoli

Question 28

What is obstructive lung disease?

Answer 28

Difficulty in air flowing through tubes (airways resistance) | Tubes narrow

Question 29

Give examples of obstructive lung diseases

Answer 29

asthma bronchiolitis/ chronic bronchitis emphysema COPD

Question 30

Give examples of restrictive lung diseases

Answer 30

Fibrosis of the lung Respiratory muscle weakness Phrenic nerve damage TB

Question 31

In which obstructive lung diseases are the alveoli fine?

Answer 31

Asthma and chronic bronchitis

Question 32

How can you measure lung function in clinic?

Answer 32

``` Peak flow (forced expiratory flow) Spirometry ```

Question 33

What is FEV1?

Answer 33

Forced expiratory volume in 1 second

Question 34

What is FVC?

Answer 34

Forced vital capacity

Question 35

What is a normal FEV1/FVC ratio?

Answer 35

Over 75%

Question 36

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

Answer 36

Decreases (FEV1 very very low)

Question 37

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

Answer 37

It is normal (or even higher) | both FEV1 and FVC decrease

Question 38

What is the hallmark of restrictive lung disease?

Answer 38

Low vital capacity

Question 39

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

Answer 39

Concave inwards

Question 40

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

Answer 40

No concave section | Just small loop, otherwise normal

Question 41

How does asthma effect compliance?

Answer 41

No effect

Question 42

What happens to the FRC in a fibrosed lung?

Answer 42

Reduced because increased lung recoil

Question 43

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

Answer 43

Increased because decreased lung recoil | --> barrel chest