Pulmonary Function Testing

Question 1

What are 3 types of pulmonary function test?

Answer 1

• Effort dependent tests
• Effort independent tests
• Gas diffusion tests

Question 2

What are examples of effort dependent tests?

Answer 2

• Forced expiratory volumes/flow rates

Question 3

How are forced expiratory volumes measured?

Answer 3

Spirometry

Question 4

What are examples of effort independent tests?

Answer 4

• Relaxed vital capacity
• Helium/N2 without static lung volumes
• Whole body plethysmography
• Impulse oscillometry
• Exhaled breath nitric oxide

Question 5

What are examples of gas diffusion tests?

Answer 5

• CO transfer factor
• Arterial blood gases (resting)
• SaO2 during exercise

Question 6

How is relaxed vital capacity measured?

Answer 6

Spirometry

Question 7

What is a forced expiratory manoeuvre?

Answer 7

From TLC to RV

Question 8

What is the forced expiratory volume in 1 second?

Answer 8

FEV1 (litres)

Question 9

What is the forced expiratory ratio?

Answer 9

FER = FEV1/FVC

Question 10

What is relaxed vital capacity?

Answer 10

Patient breathes out in their own time

Question 11

What is the normal value of FER?

Answer 11

> 75%

Question 12

In asthma, how does FEV1, FVC and FER compare with a normal individual?

Answer 12

• FEV1 is reduced
• FVC is the same (just takes longer)
• FEV1/FVC is reduced

Question 13

In COPD, how does FEV1, FVC and FER compare with a normal individual?

Answer 13

• FEV1 is reduced
• FVC is reduced
• FEV1/FVC is the same

Question 14

Why is FEV1/FVC ratio preserved in COPD?

Answer 14

FEV1 is reduced in proportion to FVC

Question 15

What is a volume-time curve?

Answer 15

Plots volume in litres (FVC and FEV1) against time (s)

Question 16

What is a flow-volume curve?

Answer 16

Flow rate (l/s) plotted against forced expiratory volume (l)

Question 17

What affects the shape of the expiratory flow-volume curve?

Answer 17

• Volume dependent expiratory airway closure - asthma, chronic bronchitis
• Pressure dependent expiratory airway closure - emphysema

Question 18

What causes volume dependent expiratory airway closure in asthma?

Answer 18

Small airways close off earlier in expiration (wheeze)

Question 19

What causes pressure dependent expiratory airway closure in COPD?

Answer 19

Small airways close off extremely early in expiration

Question 20

How is peak expiratory flow rate (PEF) measured?

Answer 20

Peak flow meter

Question 21

What are the units of peak expiratory flow rate?

Answer 21

l/min

Question 22

How does obstructive airway disease affect peak expiratory flow rate?

Answer 22

Peak expiratory flow rate is reduced in obstructive disease

Question 23

What is the FEV1/FVC ratio of someone with asthma?

Answer 23

<75%

Question 24

What is the FEV1 response to B2-agonist in asthma?

Answer 24

Increases by approx 15%

Question 25

How does restrictive airway disease affect peak expiratory flow rate?

Answer 25

Peak expiratory flow rate is normal in restrictive airway disease

Question 26

Why is peak expiratory flow rate not affected in restive airway disease?

Answer 26

In restrictive disease, no problem with conducting airways so flow rate is normal

Question 27

Why is there no FEV1 response to B2 agonist (e.g. salbutamol) in restrictive airway disease?

Answer 27

Conducting airways are normal

Question 28

What are methods of bronchial challenge testing?

Answer 28

* Exercise (will produce bronchoconstriction - cold air) * Metacholine/histamine/mannitol (markers of airway hyper-responsiveness) * Allergens/chemicals (early and late responses)

Question 29

How is metacholine/histamine/mannitol used in bronchial challenge testing?

Answer 29

Provocative dose to produce 20% fall in FEV1

Question 30

How is exercise testing used to diagnose respiratory disease?

Answer 30

* Fall in FEV1 or peak expiratory flow rate = asthma * Decrease in SaO2 during exercise in interstitial lung disease - to monitor treatment response * Full cardiopulmonary exercise test (CPET) - differentiate cardiac vs respiratory dyspnoea (HR vs oxygen uptake vs ventilatory rate)

Question 31

What type of test is the measurement of static lung volumes?

Answer 31

Effort independent test

Question 32

What information can helium dilution/N2 washout provide?

Answer 32

Functional residual capacity

Question 33

What is the equation for residual volume?

Answer 33

RV = FRC - ERV

Question 34

What is the equation for total lung capacity?

Answer 34

TLC = VC + RV

Question 35

When does TLC increase beyond normal values?

Answer 35

In hyperinflation - emphysema

Question 36

When does TLC decrease below normal values?

Answer 36

In restrictive lung disease - ILD

Question 37

What is the equation for gas trapping in COPD?

Answer 37

RV/TLC x 100

Question 38

What is CO transfer factor?

Answer 38

Co diffusion across alveolar-capillary barrier

Question 39

What is TLCO?

Answer 39

Total lung transfer for CO (diffusing capacity)

Question 40

What conditions can cause TLCO to decrease?

Answer 40

* Anaemia * Emphysema * Interstitial lung disease * Pulmonary oedema * Pulmonary embolus * Bronchiectesis

Question 41

What can TLCO be used for?

Answer 41

To monitor treatment response in lung disease

Question 42

How is airway resistance measured?

Answer 42

* Whole body plethysmography | * Impulse oscillometry (more common)

Question 43

What is impulse oscillometry?

Answer 43

Measures airway resistance during quiet tidal breathing at different resonant frequencies to give: * total resistance (5Hz) * central resistance (20Hz) * and hence peripheral airway resistance by subtraction

Question 44

What is a non-invasive marker of eosinophilic airway inflammation in asthma?

Answer 44

Exhaled breath nitric oxide measured at flow of 50ml/s (FeNO)

Question 45

Why is exhaled breath nitric oxide measurement not useful in COPD?

Answer 45

Nitric oxide suppressed by smoking

Question 46

What do high levels of NO (>35ppb) measured in exhaled breath indicate?

Answer 46

Uncontrolled asthmatic inflammation

Question 47

When is exhaled breath nitric oxide measured?

Answer 47

In adjunct to bronchial challenge to assess asthmatic inflammation - especially when spirometry is normal