Ventilation, compliance and lung function tests

Question 1

What is the average total lung capacity? (both lungs)

Answer 1

6L

Question 2

What is tidal volume?

Answer 2

The volume of breath in OR out at rest - 500mls on average

Question 3

What is pulmonary ventilation?

Answer 3

The amount of air moving into/out of the lungs

Question 4

What is Alveolar ventilation?

Answer 4

The amount of fresh air reaching the alveoli - available for gas exchange

Question 5

What is Expiratory Reserve Volume? (ERV)

Answer 5

Extra air that can be pushed out with effort after Tidal Volume

Question 6

What is residual volume?

Answer 6

Air that is always present in the alveoli

Question 7

What would happen to the alveoli without the residual volume of air?

Answer 7

They would collapse and would therefore require more effort to fill than if they were already partially filled

Question 8

What is functional residual capacity?

Answer 8

Volume of air left after an exhale at rest - Residual volume + ERV

Question 9

What is anatomical dead space?

Answer 9

Air sitting in the conducting zone that doesn’t take part in gas exchange

Question 10

What is the volume on average of anatomical dead space?

Answer 10

150mls

Question 11

How efficient is breathing at rest, and what happens to air that isn’t used?

Answer 11

70% efficient, the other 30% is trapped in anatomical dead space

Question 12

What is Hyperventilation?

Answer 12

High alveolar ventilation rate - not just respiratory rate

Question 13

Why is the PatmosO2 higher than PAO2?

Answer 13

O2 is moistened before it reaches the alveoli which saturates it

Question 14

What is the partial pressure of O2 in the Alveoli?

Answer 14

100mmHg or 13.3kPa

Question 15

What is surfactant?

Answer 15

A detergent like substance produced by type II pneumocytes which reduces surface tension

Question 16

What are the main benefits of reduced surface tension?

Answer 16

Prevents alveolar collapse and decreases the work of breathing

Question 17

What is surface tension?

Answer 17

The attraction of water molecules to one another

Question 18

Is surfactant more effective in smaller or larger cells?

Answer 18

Smaller - surfactant molecules are closer together and are therefore more concentrated

Question 19

When do the lungs start producing surfactant?

Answer 19

At around 25 weeks in development and finish around 36 weeks

Question 20

What respiratory condition will a premature baby be likely to suffer from?

Answer 20

Infant Respiratory Distress Syndrome (IRDS)

Question 21

How could an infant with IRDS be treated?

Answer 21

Flushing the lungs with saline or with a surfactant spray

Question 22

What does compliance represent?

Answer 22

Stretchability - not elasticity

Question 23

What is a major cause of low compliance?

Answer 23

Fibrosis

Question 24

What causes high compliance with low elasticity?

Answer 24

Emphysema

Question 25

Why is a larger change in pressure required at the start of inspiration?

Answer 25

To overcome surface tension and elasticity, the stretch of the lungs encourages surfactant to come up

Question 26

Why is more effort required at the start of expiration?

Answer 26

To overcome surfactant

Question 27

What does obstructive lung disease cause difficulty in?

Answer 27

Expiration

Question 28

What does restrictive lung disease cause difficulty in?

Answer 28

Inspiration

Question 29

How can oedema cause restriction?

Answer 29

By forming around alveoli

Question 30

What is FEV1?

Answer 30

The maximum amount of air a person can expire in one second (Forced Expiratory Volume)

Question 31

What is FVC?

Answer 31

The maximum amount of air a person can exhale in total (Forced Vital Capacity

Question 32

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

Answer 32

It decreases