# Pulmonary Function Tests – PFT Interpretation Explained (Pulmonology)

Okay so based on everything that we know

now we’re gonna go ahead and show you how to interpret PFDs first thing you

want to do is you want to look at the F the C and you want to see whether or not

it’s greater than 80% of predicted that’s the this is the first thing that

I look at and you really want to look at just any FEC if any FEC is greater than

80% of predicted the answer is yes or if the answer is no and this is the

algorithm that we’re going to look at here if the FEC is greater than 80% of

predicted then what you can say here is that you have no restriction no

restriction and that’s our first diagnosis that we can come up with right

off the bat if however the FEC is less than 80 percent of predictor or the

answer is no then we can say that we either have restriction or obstruction

with air trapping okay so it’s one or the other restriction or obstruction

with air trapping the next thing you do in either one of these cases as you move

on in this case you’re going to ask the question is the fev1 divided by the F

the C greater than 0.7 and again you’re going to have a yes and you’re going to

have a no if the answer is yes then there is no obstruction so by definition if the fev1 divided by

the FEC is greater than 0.7 there is no obstruction if however it’s less than

that then you have obstruction okay the next thing let’s go back here if the FEC

is not greater than 80% of predicted then you either have restriction or

obstruction with air trapping the next question that you ask in this situation

is is the total lung capacity greater than 80 percent predicted if the answer

is yes then you have obstruction with air trapping if the answer is no in

other words if it’s less than 80 percent of predicted then you have guess why

restriction now there’s something you should know

about in terms of obstruction and the severity there’s different there used to

be gold classifications in terms of Roman numerals they now used severity

and also symptomatology but if they’re ever talking to you about the gold

stages there’s gold stage 1 stage 2 stage 3 and stage 4 and for that we look

at the fev1 only the FEV 1% predicted 1 is 80 to 100 2 is 50 to 80 3 is 30 to 50

and 4 is 0 to 30 it’s also you go right to stage 4 if there is respiratory

failure with an elevated P co2 level the other thing that you should know about

when you have obstruction is you really should be able to classify if there is

reactivity or not and the 80s criteria for reactivity is fev1 or FV c change in

pre and post bronchodilator in comparison to pre bronchodilator of

greater than 12% and 200 milliliters if you don’t have either of those two or if

you have neither of those two then it is non reactive this doesn’t tell you

whether or not you should give Runkel dilators it is helpful though when

telling you whether or not this has if there is reactive Airways disease the

other thing to look at is the DLC o dl c o and whether or not is greater than 80%

of predicted okay if the DLC o is greater than 80% of predicted then you

have normal membrane surface area if it is less than 80% of

predicted then of course it’s abnormal surface membrane or membrane surface

area okay however the next thing to look at is the dlco divided by the alveolar

ventilation and if it is greater than 80% of predicted now remember what we’re

looking at here we’re seeing whether or not the dlco

divided by the Alvar ventilation is still pretty good this is an indication

and distinguishing characteristic between extrinsic and intrinsic lung

disease of course for yes it would be x trinsic and for no it would be in

trinsic so what are some examples this would be like scoliosis or Gyan Bray

syndrome and this would be for instance pulmonary fibrosis or for instance COPD

okay so let’s go over this again if you’ve got a forced vital capacity of

greater than 80 percent of predicted no restriction you can say that right off

the bat then you look at the FE v1 divided by the FEC if it’s greater than

0.7 then no obstruction you’re done you’ve got no restriction you’ve got no

obstruction if the fev1 divided by the FEC is less than 0.7 however then you’ve

got obstruction no restriction let’s go back to the very beginning if you don’t

have an FEC if of greater than 80% are predicted then you could have

restriction or obstructive with air trapping the way you tell the difference

between the two is by looking at spirometry if your total lung capacity

is greater than 80% of predicted then you know you don’t have restriction

going on but it’s more of an air trapping situation and that’s where the

obstruction comes in if your total lung capacity is less than 80% of predicted

then there’s a good chance that at restriction that’s causing both the

total lung capacity to be low and the FEC to be low once you’ve diagnosed

obstruction then you can break it two different severity and say whether

or not there’s reactivity or no reactivity in a separate situation

you’ve got the dlco if the dlco is normal that’s great if it’s not it could

be because of extrinsic disease or intrinsic disease by looking at the dlco

divided by the alveolar ventilation you can make a distinguishing characteristic

once you know if this is extrinsic disease or intrinsic disease you can put

it together with your other diagnosis up above which are in double squares and

figure out which way your diagnosis goes so keep this written down we’re going to

go over some actual examples and we’ll be able to tell what the diagnosis is by

interpreting the PFDs correctly

Nice

Amazing video! Thank you so much!

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