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