S7: pulmonary function tests

Question 1

What do peak flow meters measure?

Answer 1

The highest velocity of airflow that can transiently be achieved during a maximal expiration from total lung capacity

Question 2

What does spirometry measure?

Answer 2

Some lung volumes
Calculates airflow as volumes are measured over time
Produces graphical representations

Question 3

What is FEV1?

Answer 3

Forced expiratory volume in 1 second: maximum volume of air that can be forcefully expired within 1 second after maximal inspiration

Question 4

What is FVC?

Answer 4

Forced vital capacity: total amount of air exhaled after maximal inspiration during entire FEV test – occurs over 6 seconds

Question 5

Describe the significance of the FEV1/FVC ratio

Answer 5

Represents the proportion of patient’s forced vital capacity that they are able to expire in the first second of forced expiration
FEV1:FVC < 0.7 = obstructive problem

Question 6

Describe how obstructive lung disease would be seen in spirometry

Answer 6

FEV1 decreased
COPD – FVC initially normal, will decrease in severe disease; asthma – FVC typically decreases
FEV1:FVC < 0.7

Question 7

Describe how restrictive lung disease would be seen in spirometry

Answer 7

FEV1 may be normal/decreased
FVC decreased
FRC & TLC always decreased

Question 8

What is DLCO?

Answer 8

Diffusing capacity carbon monoxide – lets us determine how much oxygen travels from alveoli of lungs to bloodstream by measuring CO diffusion
Provides information on alveolar-capillary membrane
Can be decreased in many conditions including emphysema, alveolar inflammation & pulmonary fibrosis

Question 9

How do you differentiate between restrictive lung diseases?

Answer 9

Parenchymal lung diseases – restrictive pattern & abnormal DLCO
Restrictive lung diseases related to chest wall abnormalities & neuromuscular disease – normal DLCO