Ventilation

Question 1

Inspiration volume equals?

Answer 1

Expiration volume

The amount we breathe in, equals the amount we breathe out (a simple concept)

Question 2

What is tidal volume (TV)?

Answer 2

Normal volume of air displaced between normal inhalation and exhalation
This is around 500ml in a healthy adult

Question 3

What is residual volume?

Answer 3

What is left in the lungs after breathing out as much as you can
Lung volume is never 0L, only becomes 0L with a pneumothorax (lung collapse)

Question 4

What is vital capacity (VC)?

Answer 4

The greatest volume of air that can be expelled from the lungs after taking the deepest possible breath

Question 5

What is total lung capacity (TLC)?

Answer 5

It is the totality of the capacity of the lung, including residual volume

Question 6

How can ventilation be calculated?

Answer 6

Minute ventilation

Alveolar ventilation

Question 7

What is the equation for minute ventilation?

Answer 7

Tidal volume (ml/breath) x Respiratory rate (breaths/min)

Question 8

What does the term ‘alveolar ventilation’ refer to?

Answer 8

Respiration which is happening deep in the lungs in the alveoli

Question 9

What is the equation for alveolar ventilation?

Answer 9

(Tidal volume – dead space) x respiratory rate

Question 10

What is ‘dead space’?

Answer 10

Conducting airways where no gaseous exchange takes place

Question 11

What is the difference between minute ventilation and alveolar ventilation?

Answer 11

Alveolar ventilation corrects for air in the upper airways, as there is no gaseous exchange there
Alveolar volume is more prescriptive

Question 12

What is the average volume of the conducting airways?

Answer 12

Around 150ml

Question 13

What are the typical lung function tests performed?

Answer 13

Spirometry

Peak flow meter

Question 14

When are lung function tests particularly important?

Answer 14

In asthma diagnosis

Question 15

What are the 2 key volumes used to look at lung function?

Answer 15

Forced vital capacity (FVC)

Forced expiratory volume in 1 sec (FEV1)

Question 16

What is FVC?

Answer 16

Maximum volume exhaled

Gives an indication of the size/capacity of the lungs

Question 17

What is FEV1?

Answer 17

Amount that you can force out of your lungs in 1 second

Around 80% of FVC in a healthy patient

Question 18

What is obstructive lung disease?

Answer 18

Obstructive meaning airways are obstructed

Question 19

What happens to these volumes in obstructive lung disease?

Answer 19

FEV1 is reduced due to increased resistance in the airways
FEV1 is <80% of FVC
FVC is around normal (over time the amount of air you can force out is normal)

Question 20

Give 2 examples of obstructive lung disease.

Answer 20

Asthma, cystic fibrosis

Question 21

What is restrictive lung disease?

Answer 21

Affects how easily the lungs inflate and deflate

Question 22

What happens to these volumes in restrictive lung disease?

Answer 22

FEV1 is reduced
FVC is reduced
FEV1 >80% of FVC (as both are reduced, ratio is not altered)

Question 23

What is lung compliance?

Answer 23

A measure of how easily the lungs and thorax expand
Relationship between ΔV and ΔP
In healthy individuals this happens easily, in some disease states, this is not possible

Question 24

Explain what is happening in high compliance.

Answer 24

When this person has the exact same ΔP, the ΔV is much larger
There is a loss of alveolar and elastic tissue, this loss of elastic recoil means the lungs are floppy/stretchy, like a loose elastic band, they are easily stretched hence the large change in volume

Question 25

In which conditions would you see high compliance?

Answer 25

Emphysema, old age

Question 26

Explain what is happening in low compliance.

Answer 26

When this person has the exact same ΔP, the ΔV is much smaller
There is an increase in collagen expression due to inflammation, this stiffens the lungs and makes them more difficult to inflate

Question 27

In which conditions would you see low compliance?

Answer 27

Oedema, pneumonia, fibrosis
Disorders affecting the movement of the chest, particularly the ribs and spinal column (e.g. arthritis, ankylosing spondylitis)
Premature infants

Question 28

What else can cause reduced compliance?

Answer 28

Normally, type II cells in the lung produce surfactant
This surfactant is a type of phospholipid
Reduced surfactant production leads to problems as it increases surface tension (force across a liquid area)
If we don’t have enough surfactant, this tension pulls on tissues

Question 29

What is new-born respiratory distress syndrome?

Answer 29

Premature infants quite often suffer from this condition
These patients have underdeveloped type II cells in the lungs meaning reduced surfactant production, higher surface tension and alveolar collapse

Question 30

What is the equation for lung compliance?

Answer 30

CL = ΔVL / ΔTP

Question 31

What is the equation for change in transpulmonary pressure?

Answer 31

ΔTP = TP (END) – TP(START)
ΔTP = [Palv – Pip]end - [Palv – Pip]start

Question 32

What is ventilation-perfusion inequality?

Answer 32

A mismatch between ventilation and blood flow, reduces the amount of oxygen entering the body

Question 33

Give an example of where ventilation-perfusion equality can be seen.

Answer 33

Lung diseases where alveoli are in very poor condition, can breath in but oxygen can’t pass through the tissue in the alveoli into blood vessels
There is a mismatch in ventilation and what you can actually take into the body
This is seen in emphysema, where degeneration of alveolar and bronchiole walls and capillaries occurs