Ventilation and compliance 2

Question 1

What is surfactant?

Answer 1

Detergent like fluid that reduces surface tension on alveolar surface membrane

Question 2

What cells produce surfactant?

Answer 2

Type 2 alveolar cells

Question 3

Describe briefly surface tension

Answer 3

Due to the attraction between water molecules causing an air-water interface

Question 4

Does surface tension cause a net force and movement forwards or backwards?

Answer 4

Forwards

Question 5

What does surfactant reduce? (3)

Answer 5

Tendency for alveoli to collapse
Tendency for alveoli to recoil
Attraction between air and water

Question 6

What does surfactant increase? (1)

Answer 6

Lung compliance => distensibility

Question 7

Does surfactant make breathing easier or more difficult?

Answer 7

Easier

Question 8

Is surfactant more effective in small or large alveoli? Why?

Answer 8

Small

Surfactant molecules come closer together and are more concentrated

Question 9

When does surfactant start in gestation and when is it complete?

Answer 9

About 25 weeks

About 36 weeks

Question 10

What is surfactant production stimulated by which are produced at the later stages of pregnancy?

Answer 10

Cortisol

Thyroid hormone

Question 11

If a baby is premature what may they suffer from and how can this be treated?

Answer 11

Infant respiratory distress syndrome (IRDS)

Synthetic surfactant

Question 12

What is seen when saline is used to demonstrate lung inflation in utero?

Answer 12

Less change in pressure is required as no need to overcome surface tension

Question 13

Compliance

Answer 13

Change in volume relative to change in pressure

Question 14

Does compliance represent stretchability or elasticity?

Answer 14

Stretchability

Question 15

Stretchability

Answer 15

How easy to stretch open the lungs

Question 16

Elasticity

Answer 16

How easy it is to get the air out of the lungs

Question 17

High compliance

Answer 17

Large increase in lung volume for small decrease in Pip

Question 18

Low compliance

Answer 18

Small increase in lung volume for a large decrease in Pip

Question 19

What 2 factors can change Compliance?

Answer 19

Disease states

Age

Question 20

Is more pressure needed to reach a particular lung volume during inspiration or maintain this same volume during expiration?

Answer 20

Inspiration

Question 21

Why does inspiration require a larger pressure change?

Answer 21

Expiration is passive as the effort from inspiration is recovered as elastic recoil and at the start of inspiration the chest cavity is constricted leading to a greater resistance

Question 22

Emphysema

Answer 22

Loss of elastic tissue so expiration takes a lot of effort

Pip becomes positive so PA = -ve

Question 23

Fibrosis

Answer 23

Inert fibrous tissue means effort of inspiration increases

Decreased compliance

Question 24

Is the greatest compliance at the base or apex of the lung?

Answer 24

Base - due to gravity

Volume change is greater for a given change in pressure

Question 25

Does alveolar pressure incline or decline with height from base to apex?

Answer 25

Decline eg most at base

Question 26

Why is the compliance highest at the base?

Answer 26

Alveoli are compressed at the base by the weight of the lung and diaphragm below Small change in Pip leads to a large change in volume Top alveoli are already quite full

Question 27

Obstructive lung disease - brief description and example

Answer 27

Obstruction of flow especially in expiration eg asthma and an increases airway resistance

Question 28

Restrictive lung disease - brief description and example

Answer 28

Restriction of lung expansion eg fibrosis with a loss of compliance

Question 29

COPD

Answer 29

Chronic bronchitis - inflamed bronchi emphysema - destroyed alveoli 80 M word wide with about 1% in UK with 10% over 75s

Question 30

Restrictive lung disease

Answer 30

IRDS, pneumothorax and oedema which is a fluid build up around alveoli

Question 31

Spirometry

Answer 31

Technique used to measure lung function

Question 32

Name the 2 types of spirometry

Answer 32

Static and dynamic

Question 33

Describe the differences between the 2 kinds of spirometry

Answer 33

Static only considers the volume exhaled | Dynamic takes into account the time taken to exhale a certain volume in 1 second

Question 34

Which type of spirometry is more useful?

Answer 34

Dynamic

Question 35

What can be directly measured by spirometry?

Answer 35

Tidal volume, vital capacity, inspiratory capacity, inspiratory reserve volume and expiratory reserve volume

Question 36

What is the reason why not everything can be measured by spirometry

Answer 36

Anything containing residual volume cannot which also includes functional residual capacity and total lung capacity

Question 37

What is the difference between volume and capacity

Answer 37

Capacity are 2 or more volumes added together

Question 38

What does the ratio FEV1/FVC mean?

Answer 38

Forced expiratory volume in 1 second

Question 39

What is the normal FEV1/FVC?

Answer 39

80%

Question 40

Describe the FEV1/FVC ratio in obstructive lung disease

Answer 40

Both volumes fall but FEV1 falls more so the ratio is reduced

Question 41

Describe the FEV1/FVC ratio in restrictive lung disease

Answer 41

Both ratios fall so same ratio or even increases

Question 42

Why is the FEV1/FVC ratio limited?

Answer 42

Not always an indicator of health as in restrictive lung disease there is a severe compromise of function although the ratio does not change much from normal or will even increase

Question 43

Forced expiratory flow rate

Answer 43

The average expired flow over the middle of an FVC

Question 44

Compare FEF25-75 to FEV1

Answer 44

They both correlate but changes are more striking | Greater "normal" range