Lung Function Testing

Question 1

What are the four main goals of lung function testing?

Answer 1

Diagnose disease
classify obstructive vs restrictive
assess severity
monitor progression & pre-operative risk.

Question 2

What does peak expiratory flow (PEF) measure?

Answer 2

Maximum speed of expiration.

Question 3

What does a reduction in PEF indicate?

Answer 3

Large airway obstruction (e.g., asthma).

Question 4

Why is PEF limited as a diagnostic tool?

Answer 4

Strongly effort-dependent and cannot diagnose disease alone.

Question 5

How is PEF used in asthma?

Answer 5

Monitoring severity and detecting early deterioration (green/amber/red zones).

Question 6

What is FVC?

Answer 6

Forced Vital Capacity — total volume exhaled forcefully after full inspiration.

Question 7

What is FEV₁?

Answer 7

Forced Expiratory Volume in the first second.

Question 8

What is the purpose of the FEV₁/FVC ratio?

Answer 8

Determine obstructive vs restrictive patterns.

Question 9

What does a normal spirometry curve look like?

Answer 9

Rapid rise to peak → gradual plateau.

Question 10

What FEV₁/FVC ratio indicates obstruction?

Answer 10

< 70%.

Question 11

How does the FEV₁/FVC ratio appear in restrictive disease?

Answer 11

Normal or increased.

Question 12

What happens to FEV₁ and FVC in obstructive lung disease?

Answer 12

FEV₁ ↓↓↓, FVC ↓ → ratio ↓.

Question 13

What happens to FEV₁ and FVC in restrictive lung disease?

Answer 13

Both ↓ proportionally → ratio normal or ↑.

Question 14

Give examples of obstructive lung diseases.

Answer 14

Asthma, COPD, bronchiectasis.

Question 15

What is the classic shape of the flow–volume loop in obstruction?

Answer 15

Scooped-out / concave expiratory limb.

Question 16

What lung volumes increase in obstruction?

Answer 16

RV, FRC, TLC (air trapping and hyperinflation).

Question 17

Give examples of restrictive lung disease.

Answer 17

Pulmonary fibrosis, scoliosis, obesity, neuromuscular disorders.

Question 18

What is the flow–volume loop shape in restriction?

Answer 18

Normal shape but smaller and narrower.

Question 19

What happens to TLC in restrictive disease?

Answer 19

Decreased.

Question 20

What flow–volume loop feature indicates obstruction?

Answer 20

Reduced peak flow + scooped expiratory limb.

Question 21

What flow–volume loop feature indicates restriction?

Answer 21

Narrow, tall loop with reduced lung volumes.

Question 22

What is residual volume (RV)?

Answer 22

Air remaining after maximal expiration.

Question 23

What is functional residual capacity (FRC)?

Answer 23

Volume in lungs at end of normal expiration.

Question 24

What happens to RV and FRC in obstructive disease?

Answer 24

Both increase (air trapping).

Question 25

What happens to all lung volumes in restrictive disease?

Answer 25

All decrease (reduced lung expansion).

Question 26

FRC is decreased by what factors?

Answer 26

Supine position, obesity, pregnancy, anaesthesia, fibrosis.

Question 27

FRC is increased by what conditions?

Answer 27

Emphysema and ageing.

Question 28

Why is FRC important clinically?

Answer 28

Prevents alveolar collapse & provides oxygen reserve during apnoea.

Question 29

What does DLCO measure? ## Footnote diffusion capacity

Answer 29

Gas transfer efficiency across the alveolar–capillary membrane.

Question 30

What gas is used to measure DLCO?

Answer 30

Carbon monoxide (CO).

Question 31

DLCO is reduced in which conditions?

Answer 31

Emphysema, pulmonary fibrosis, pulmonary hypertension, anaemia.

Question 32

DLCO is increased in which conditions?

Answer 32

Polycythaemia, pulmonary haemorrhage, left-to-right shunts.

Question 33

How does DLCO help differentiate asthma from emphysema?

Answer 33

Asthma = normal DLCO; emphysema = reduced DLCO.

Question 34

Why are lung function tests used pre-operatively?

Answer 34

Predict risk of respiratory complications under anaesthesia.

Question 35

What FEV₁ value is concerning for major surgery?

Answer 35

< 1.5 L.

Question 36

What happens to FRC under general anaesthesia?

Answer 36

Decreases → increased atelectasis risk.

Question 37

What conditions increase risk of postoperative ventilation failure?

Answer 37

Severe COPD, low DLCO, restriction with low TLC

Question 38

What pattern does fibrosis show on LFTs?

Answer 38

Restrictive: ↓FVC, ↓TLC, normal ratio.

Question 39

What pattern does COPD show on LFTs?

Answer 39

Obstructive: ↓FEV₁, ↓ratio, ↑RV, ↑FRC.

Question 40

What LFT pattern is typical in obesity?

Answer 40

Restrictive (reduced FVC and TLC).

Question 41

What FEV₁ % predicted corresponds to mild COPD?

Answer 41

≥ 80%.

Question 42

What FEV₁ % predicted corresponds to severe COPD?

Answer 42

30–49%.

Question 43

What FEV₁ % predicted corresponds to very severe COPD?

Answer 43

< 30%.

Question 44

Obese patient with ↓FVC, ↓TLC, normal ratio — diagnosis?

Answer 44

Restrictive pattern from obesity.

Question 45

Smoker with ↓FEV₁, ↓ratio, scooped loop — diagnosis?

Answer 45

COPD (obstructive).

Question 46

Patient with scoliosis and ↓TLC — diagnosis?

Answer 46

Restrictive lung disease from thoracic deformity.

Question 47

Which test differentiates obstruction vs restriction?

Answer 47

Spirometry (FEV₁/FVC ratio).

Question 48

Which test detects hyperinflation and air trapping?

Answer 48

Lung volumes (RV, FRC, TLC).

Question 49

Which test assesses gas exchange across alveoli?

Answer 49

DLCO

Question 50

Which measurement is most effort-dependent?

Answer 50

Peak Expiratory Flow (PEF).