PFTs Flashcards
How do you measure residual volume?
Helium dilution method
Restrictive disease PFT changes
FVC = decrease*
TLC = normal/decrease*
FEV1/FVC ratio = increased/normal*
RV = decrease*
FEV1 = normal/increased
Obstructive disease PFT changes
FVC = normal or decreased*
TLC = increased*
FEV1/FVC ratio = decreased*
RV = increased *
Normal -> severe benchmark measurements for obstructive disorders
1) FEV1 % compared to predicted
- normal = > 75
- mild = 60-75
- moderate = 40-60
- severe = <40
* decreases as it gets worse
2) RV % compared to predicted
- normal = 80-120
- mild = 120-150
- moderate = 150-175
- severe >200
* increases as it gets worse*
Normal -> severe benchmark measurements for restrictive disorders
1) FEV1 % compared to predicted
* DOESN’T CHANGE*
2) RV % compared to predicted
- normal = 80-120
- mild = 80-120
- moderate = 70-80
- severe <70
* decreases as it gets worse*
3) FVC % of predicted
- normal = >80
- mild = 60-80
- moderate = 50-60
- Severe = <50
* decreases as it gets worse (generally 70 or above is fine though)*
How to tell what is a significant Change from pre to post Bronchiodilator in pulmonary disorders?
At least 12% increase in FVC or FEV1 = significant
What is used most commonly in adults to determine asthma?
Methylcholine challenges will show obstructive disorder based FVC and FEV1 values
Methylcholine challenged is used to induce symptoms and then measure PFT measurements
How to determine if something is hyperinflation and air-trapping?
Air trapping = Residual volume is higher than 120%
Hyperinflation = TLC is higher than 120%
DLCO
Measurement that shows the diffuse of carbon monoxide across alveoli to the blood stream during inspiration and expiration
this is used since carbon monoxide VERY easily diffuses across the alveoli and blood stream= so if its low that clearly signifies a perfusion/ diffusion issue*
Can fixed or variable be reversed w/ bronchodilation?
Variable can be reversible
Fixed disorders cannot be reversed with bronchodilators
