Basic lung function tests

Question 1

Why are lung function tests useful?

Answer 1

Diagnosis, symptom analysis, treatment monitoring

Useful in both symptomatic patients and those at risk of pulmonary disease

Question 2

What are the 3 commonly assessed functions of the respiratory system?

Answer 2

Diameter of airways (air flow rate)
Total lung volume (vital capacity)
Effectiveness of oxygen diffusion into blood

Question 3

How can you measure the diameter of airways?

Answer 3

Peak flow and FEV1

Question 4

How do you measure the total lung capacity?

Answer 4

FVC

Question 5

How can you measure how well oxygen diffuses into the blood?

Answer 5

DLCO (Diffusion capacity for carbon monoxide)

- assesses permeability of respiratory system

Question 6

What are the advantages of spirometry?

Answer 6

Readily available
No risk to patient (or clinician)
Instant results
Easily repeatable

Question 7

What are the disadvantages of spirometry?

Answer 7

Expensive equipment
Requires patient compliance
Requires training

Question 8

Give examples of obstructive lung diseases

Answer 8

COPD (emphysema, bronchitis)
Asthma
Cystic Fibrosis
Bronchiectasis

Question 9

What is the difference between obstructive and restrictive lung disease?

Answer 9

Obstructive - patients tend to have difficulty emptying their lungs due to narrowing or airways or damage to lungs - leads to increased RV

Restrictive - patients tend to have difficulty filling their lungs - leads to reduced inspiratory capacity

Question 10

Give examples of restrictive lung diseases

Answer 10

Pulmonary Fibrosis
Obesity
Scoliosis

Question 11

How do spirometry results differ in obstructive and restrictive lung diseases?

Answer 11

FEV1:FVC <0.7 = obstructive

FEV1:FVC >0.7 (but with significantly reduced FVC) = restrictive

Question 12

What are the contraindications of spirometry?

Answer 12

Haemoptysis 
Pneumothorax
Unstable CV status 
Aneurysms 
Acute illness
Recent thoracic, abdominal or ENT surgery
Pain
Pregnancy

Question 13

What is the inspiratory reserve volume?

Answer 13

The maximum amount of additional air that can be drawn into the lungs by forced inspiration (after normal inspiration)

Question 14

What is the tidal volume?

Answer 14

The amount of air breathed in and out during normal (quiet) respiration

Question 15

What is the expiratory reserve volume?

Answer 15

The maximum amount of additional air that can be expired from the lungs by forced expiration (after normal expiration)

Question 16

What is the residual volume?

Answer 16

The amount of air left in the lungs following normal tidal respiration

Question 17

What is the functional residual capacity?

Answer 17

ERV + RV

Amount of air left in lungs following passive expiration

Question 18

What is inspiratory capacity?

Answer 18

TV + IRV

The total amount of air that can be drawn into the lungs after normal expiration

Question 19

What is vital capacity?

Answer 19

The maximum amount of air that can be expired from the lungs following deep inspiration (e.g. peak flow)
[Measured from maximum inspiration to maximum expiration]

Reduction in vital capacity indicates lung restriction

Question 20

What is total lung capacity?

Answer 20

The total amount of air contained in the lungs following maximal forced inspiration

Question 21

What differences on a peak flow chart is indicative of asthma?

Answer 21

> 20% variability between morning and evening

[Slight variability is normal]

Question 22

What does spirometry measure?

Answer 22

Measurement of forced expiratory volume in one second (FEV1) and forced vital capacity (FVC)

Question 23

What causes a wheeze?

Answer 23

Turbulent flow on expiration due to airway narrowing