11 Spirometry

Question 1

Why should spirometry be done sitting down even though FVC standing > FVC seated?

Answer 1

Don’t want patient to faint

High intrathoracic pressure- reduced CO and reduced cerebral blood flow

Question 2

From this graph, how do we work out Inspiratory Capacity and Functional Residual Capacity?

Answer 2

Question 3

What can forced flow measurements show us?

Answer 3

• Response to treatment
• Change with age/growth
• Progression of disease

Question 4

What are each of the following : FVC, FEV1 and PEF?

Answer 4

Functional vital capacity

Maximum volume of air that can be inhaled following a maximum exhalation

FEV1 (Forced Expiratory Volume)

Volume exhaled in first second

PEF (Peak Expiratory Flow)

Maximal speed of airflow as patient exhales (can use FLOWMETER)

Question 5

Why is FEV1 useful?

Answer 5

Most reproducible parameter

Useful for diagnosing and managing patients with obstructive pulmonary diseases eg COPD or Asthma

Question 6

Explain why the volume time graph for an obstructive pulmonary disease would give the following trace? What would be the expected FEV1/FVC ratio for this type of disease?

Answer 6

• FVC not markedly reduced
• Narrowing of airways
  
  • So FEV1 reduced

FEV1/FVC ratio <70% compared to expected (from Nomogram)

Question 7

How would you expect the volume time graph to appear in a restrictive pulmonary disease? What would you expect the FEV1/FVC ratio to be?

Answer 7

• FVC markedly reduced- lungs can’t expand properly
• Fraction of air expelled in 1 second is normal but total FEV1 is reduced

Low FVC

Low FEV1

But FEV1/FVC ratio >70%

Question 8

Where on this flow volume loop is there air coming out of the smaller airways? Indicate the Total lung capacity and the vital capacity

Answer 8

Question 9

What does the scalloping of the graph on the right indicate?

Answer 9

Question 10

What pathology may be causing each of these flow volume loops?

Answer 10

Question 11

For reference: Flow volume loops with restrictive and obstructive pulmonary diseases.

Answer 11

Question 12

When carrying out spirometry, how many recording should you aim for?

Answer 12

3

More than 3= fatigue will begin to affect results

Question 13

What lung function test can be used to measure:

• Residual volume
• Dead space
• Diffusion capacity

Answer 13

• Residual volume: helium dilution test
• Dead space: nitrogen washout method
• Diffusion capacity: Carbon monoxide transfer factor (TLCO)