Why should spirometry be done sitting down even though FVC standing > FVC seated?
Don't want patient to faint
High intrathoracic pressure- reduced CO and reduced cerebral blood flow
From this graph, how do we work out Inspiratory Capacity and Functional Residual Capacity?
What can forced flow measurements show us?
- Response to treatment
- Change with age/growth
- Progression of disease
What are each of the following : FVC, FEV1 and PEF?
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)
Why is FEV1 useful?
Most reproducible parameter
Useful for diagnosing and managing patients with obstructive pulmonary diseases eg COPD or Asthma
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?
- FVC not markedly reduced
- Narrowing of airways
- So FEV1 reduced
- So FEV1 reduced
FEV1/FVC ratio <70% compared to expected (from Nomogram)
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?
- FVC markedly reduced- lungs can't expand properly
- Fraction of air expelled in 1 second is normal but total FEV1 is reduced
But FEV1/FVC ratio >70%
Where on this flow volume loop is there air coming out of the smaller airways? Indicate the Total lung capacity and the vital capacity
What does the scalloping of the graph on the right indicate?
What pathology may be causing each of these flow volume loops?
For reference: Flow volume loops with restrictive and obstructive pulmonary diseases.
When carrying out spirometry, how many recording should you aim for?
More than 3= fatigue will begin to affect results
What lung function test can be used to measure:
- Residual volume
- Dead space
- Diffusion capacity