PFTs Flashcards
define obstructive disease
air can’t get out
2 subtypes of obstructive
- asthma
2. COPD
2 subtypes of COPD
- emphysema
2. chronic bronchitis
formula for resistance
^P/flow
key to asthma
- reversible
- narrowing by smooth muscle
- mucous hypersecretion
2 key things to look for in asthma with broncodilator
- FEV1 > 12%
2. > 180cc
define chronic bronch.
cough with sputum most days > 3month/year, 2 years in row
what happens to inflation in emphysema
hyperinflation - TLC increases
2 types of restriction causes
- chest wall
2. lung scarring
3 things measured with PFT
- volume
- flow
- diffusion
3 measures of volume
- TLC - total inspiration
- FRC - end of quiet expiration
- RV - end of hard expiration
2 ways to measure FRC
- He dilution
2. body box
what does a large diff between He and body box measures
gas trapping
what do the curves of an FT curve represent
flow vs. volume
when is flow normally bigger, before or after FEV50
before
what happens on expiration in extrathoracic obstruction?
pushes airway open
what happens on expiration in extrathoracic obstruction?
closes airway
what suggest obstruction
FEV1/FVC < 0.7
what does a high flow with low volume suggest?
restriction
what is happening if FEV1/FVC is normal but FEV50 and 75 are low
small airway disease - not sure what it means
3 causes of lowered diffusion
- decreased surface area
- thicker walls
- low Hb
what is obs with low DLCO
emphysema
what is obs with good DLCO
CB or asthma
what does DLCO tell us about restriction
low - interstitial
good - chest wall
how does methacholine test work?
slowly increase until FEV1 hits 20%
how to do walk test
walk 6 minutes and compare O2 from before and after
what is first step of PFT?
look at demos
what is normal for FEV, FRC, FVC, VC, RV
+/-20% of normal
what is normal for DLCO
+/-25% of normal
normal for FEV50 and 75
+/-50% of normal
requirement for athma reversibility
12% FEV1 change or increase of 180 cc
