Spirometry

Question 1

What does spirometry measures?

Answer 1

It measures airflow and functional lung changes.

Question 2

What is spirometry used for?

Answer 2

This can aid the diagnosis of a number of respiratory conditions, but it is primarily used to distinguish between restrictive and obstructive lung diseases.

Question 3

How do you use a spirometer?

Answer 3

Patients are asked to blow into a mouthpiece attached to a spirometer to measure different values.

Question 4

What are the key values in spirometry?

Answer 4

FEV1 (forced expiratory volume) in the first second.

FVC (forced vital capacity)- total lung volume from maximum inspiration to maximum expiration in forced exhalation.

Question 5

Common patterns in obstructive conditions

Answer 5

When airflow is obstructed, FVC may be reduced.
FEV1 is much more reduced, hence the FEV1/FVC ratio falls.
It takes much longer to exhale in obstructive conditions but FVC can be normal in mild/moderate obstructive conditions.
FEV1/FVC ratio < 0.7

Question 6

Conditions causing an obstructive defect

Answer 6

Conditions causing an obstructive defect include: 
COPD 
Asthma 
Bronchiectasis 
Foreign bodies 
Tumours 
Stenosis following tracheostomy

Question 7

Common patterns in restrictive conditions

Answer 7

FEV1 and FVC are reduced as the lung can’t expand.

FEV1/FVC ratio >0.7

Question 8

Conditions causing a restrictive defect

Answer 8

Lung fibrosis 
Skeletal abnormalities 
Neuromuscular diseases 
Pleural effusion
Pleural thickening