pft Flashcards
pft is to assess disease severity w progression in what?
copd, sarcoidosis
CHF, pul htn
neurological disorders
what is forced vital capacity
the max amount of air a person can exhale in 6 seconds
what is the percentage of predicted is normal valve in FVC
80-120%
what is FEV1
it is part of FVC but amount of air exhaled in first second
> 80-120 is normal of predicted
fev1 /fvc ?
% of fvc that can be expired in 1 second
what is the meaning of terms predicted and actual
predicted number given in machine based on gender, age, weight , height
actual: the value the patient actually scores
what is the first thing u look at to know if obstructive or restrictive ?
if the % predicted is < 80% = OBSTRUCTIVE
if % predicted is norm or high = norm or RESTRICTIVE pattern determine by fev1 and fvc ratio
how do u differ btwn normal or restrictive if fev1/fvc ratio is normal or high
we look at both fev1/fvc percentages alone
if % predicted of both are normal = NORMAL
if % predicted of both is low = RESTRICTIVE
how do u determine if restrictive is due to pulmonary or extra pulmonary cause ?
DLCO
what is the mechanism of DLCO
pt inhales small trace of CO
CO enters alveolar bed much faster and therefore most of co inhaled must be absorbed
so low absorbtion indicates pulmonary scarring, fibrosis (ILD)
what if DLCO is low or normal
if low : pulmonary cause (ILD)
normal: extra pulmonary ( neuromuscular)
what is a pure obstructive pattern
low FEV1/FVC
low FEV1
norm or slightly low FVC
what to do next if obstructive
bronchodilator challenge
if obstruction is reversible after bronchodilator FEV1 would increase by 12% and fev1 or fvc by 200ml -NEED BOTH)
reversible airway obstruction = asthma ( some copd have degree of reversibility)
what is a metacholine challenge test
it is done if asthma is suspected and all other tests are normal
or if occupational or exercice imduced asthma is suspected as well
what would confirm a positive metacholine test
a 20% decrease in fev 1 w metacholine
