Flashcards in Pulmonary Function Testing Deck (47)
What are 3 types of pulmonary function test?
* Effort dependent tests
* Effort independent tests
* Gas diffusion tests
What are examples of effort dependent tests?
* Forced expiratory volumes/flow rates
How are forced expiratory volumes measured?
What are examples of effort independent tests?
* Relaxed vital capacity
* Helium/N2 without static lung volumes
* Whole body plethysmography
* Impulse oscillometry
* Exhaled breath nitric oxide
What are examples of gas diffusion tests?
* CO transfer factor
* Arterial blood gases (resting)
* SaO2 during exercise
How is relaxed vital capacity measured?
What is a forced expiratory manoeuvre?
From TLC to RV
What is the forced expiratory volume in 1 second?
What is the forced expiratory ratio?
FER = FEV1/FVC
What is relaxed vital capacity?
Patient breathes out in their own time
What is the normal value of FER?
In asthma, how does FEV1, FVC and FER compare with a normal individual?
* FEV1 is reduced
* FVC is the same (just takes longer)
* FEV1/FVC is reduced
In COPD, how does FEV1, FVC and FER compare with a normal individual?
* FEV1 is reduced
* FVC is reduced
* FEV1/FVC is the same
Why is FEV1/FVC ratio preserved in COPD?
FEV1 is reduced in proportion to FVC
What is a volume-time curve?
Plots volume in litres (FVC and FEV1) against time (s)
What is a flow-volume curve?
Flow rate (l/s) plotted against forced expiratory volume (l)
What affects the shape of the expiratory flow-volume curve?
* Volume dependent expiratory airway closure - asthma, chronic bronchitis
* Pressure dependent expiratory airway closure - emphysema
What causes volume dependent expiratory airway closure in asthma?
Small airways close off earlier in expiration (wheeze)
What causes pressure dependent expiratory airway closure in COPD?
Small airways close off extremely early in expiration
How is peak expiratory flow rate (PEF) measured?
Peak flow meter
What are the units of peak expiratory flow rate?
How does obstructive airway disease affect peak expiratory flow rate?
Peak expiratory flow rate is reduced in obstructive disease
What is the FEV1/FVC ratio of someone with asthma?
What is the FEV1 response to B2-agonist in asthma?
Increases by approx 15%
How does restrictive airway disease affect peak expiratory flow rate?
Peak expiratory flow rate is normal in restrictive airway disease
Why is peak expiratory flow rate not affected in restive airway disease?
In restrictive disease, no problem with conducting airways so flow rate is normal
Why is there no FEV1 response to B2 agonist (e.g. salbutamol) in restrictive airway disease?
Conducting airways are normal
What are methods of bronchial challenge testing?
* Exercise (will produce bronchoconstriction - cold air)
* Metacholine/histamine/mannitol (markers of airway hyper-responsiveness)
* Allergens/chemicals (early and late responses)
How is metacholine/histamine/mannitol used in bronchial challenge testing?
Provocative dose to produce 20% fall in FEV1