Flashcards in 6.1 Lung Function Testing FINISH Deck (29):
Name three reasons for pulmonary function tests?
When in breathing would an extrathoracic abnormality be evident?
When in breathing would an intrathoracic abnormality be evident?
What may cause a variable upper airway obstruction?
What could cause a fixed upper airway obstruction?
What can the tracings produced by spirometry be used to calculate?
What is a time-volume graph useful for measuring?
Forced vital capacity
What is an example of an obstructive disorder?
Why is FEV1 decreased in obstructive disorders?
Narrowed airway reduces the speed that air can be breathed out
What spirometry results would you expect in obstructive airways?
FVC nearly normal
FEV1/FVC reduced <70%
What is an example of a disease that restricts the airways?
Why is FVC reduced in restrictive airways?
Because the lungs are stiff so cant be expanded adequately
Why is speed normal in restrictive airways?
Because there is no narrowing
What spirometry results would you expect in restrictive airways?
FEV1/FVC normal or improved >70%
What should a flow volume loop show?
Maximum flow occurs early in expiration
Then small airways become narrowed by compression of the lungs
Results in an early fall in expiratory flow rate
Why should PEFR be plotted on a chart?
Because it varies according to height and weight
Why is there scalloping of curve in an obstructive defect?
Airways collapse on expiration
This dramatically reduces flow
What does vital capacity depend on?
Maximal expiration and maximal inspiration
What sort of defect is more sensitively revealed by an expiratory flow-volume loop?
What would a mild obstruction of the small airways produce on a flow volume curve?
What would indicate a severe obstruction on the flow volume curve?
How can we measure residual volume?
Helium dilution test
How can you measure dead space?
Nitrogen wash out method
How can diffusion capacity be estimated?
Carbon monoxide transfer factor
What is diffusion conductance?
The resistance to diffusion across the alveolar membrane
What is another name for the nitrogen washout technique?
In addition to measuring dead space, what can the nitrogen washout technique be used to assess?
Mixing efficiency within the lungs
How is anatomical dead space determined?
By measuring the volume of gas that is in the conducting airways