We’ll now take a look at the category of
restrictive lung diseases. When we continue
through our differentials of restrictive lung
diseases dealing with idiopathic pulmonary
fibrosis or, well, we'll give you the definition
and criteria of Usual Interstitial Pneumonia,
often times abbreviated as IPF or UIP, as
you shall see repeatedly, then it’s the
fact that the lung here is extremely non-compliant,
it is stiff and we’ll go through a number
of differentials in which it will give you
this clinical picture.
Now, with restrictive, what is happening?
The fact that the lung is not expanding properly,
why? Maybe there is increased fibrosis.
So therefore, first and foremost, whenever
there’s lung disease, tell me about your
forced vital capacity? It is always decreased.
What does that mean? Well, in obstructive,
you tell me about FVC. It is also decreased.
In obstructive, tell me about TLC. In obstructive,
it is increased. In restrictive, your TLC
is in fact, decreased. Your first major differentiation
point between restrictive and obstructive.
Let us take a look at your pulmonary function
test. Whenever your FEV1 to FVC ratio is
decreased, for a fact you have obstructive.
If however, you don’t find your FEV1 to
FVC ratio to be decreased, then you know that
you’re probably in the realm of? Good,
restrictive. So what becomes really important
here, of paramount importance, would be then
Let’s take a look at two different types,
but what’s more important, once again, is
understanding as to what kind of test are
you performing or what kind of test is being
presented to you so that you’re able to
properly interpret your situation. Type 1,
here, poor breathing mechanics considered
to be extrapulmonary. Stop there. What do
you mean by extrapulmonary? Well, there might
be issues with maybe perhaps the respiratory
centre. Maybe it was a nerve conduction
problem. Maybe such as Guillain-Barré. Or
maybe it was actual mechanical handicap, meaning
to say you have something like kyphoscoliosis
in which now your thoracic cage becomes quite
small, restricting the lung from expanding.
Now, as a rule of thumb, when you have extrapulmonary
issues, your A-a gradient or A-a widening
is normal. Keep in mind, some of the parameters
that we looked at for A-a gradient to the
fact where, well, if a patient is getting
older, then you can expect their normal A-a
gradient, well, to still be normal, but it
increases. And then secondly, if there’s
a hospital setting in which your FiO2 has
been given with oxygen, so, therefore, there
also you would expect your A-a gradient to
then increase, but usually, you want to keep
your A-a gradient in mind as being between
10 and 20.
Okay. Now, why is it that extrapulmonary would
then be normal if it’s extrapulmonary. It's
a pathology. Well, the reason for that,
let me give you real quick, something like
your respiratory centre that has been knocked
out by a opioid. So, the patient’s been
taking opioid, maybe perhaps to deal with
his or her pain, which, of course, is a big
industry. And so, therefore, knocking out
the respiratory centre then does what?
Results in what kind of breathing pattern?
Good, hypoventilation. Bring everything together
now. If you have hypoventilation, what then
happens to your carbon dioxide? You’re going
to retain more, so increased carbon dioxide.
Good. Next, what happens to your pH? Your
pH is going to decrease, we have now our primary
respiratory acidosis. What’s my point? Well,
I have just taken you from knocking out the
respiratory centre which is your extrapulmonary.
As far as the alveoli is concerned, well,
its oxygen is going to be decreased, hypoventilation.
And then if that oxygen in the alveoli is
decreased, well will there be a decrease in
your PO2 meaning to say in your artery?
Of course, and they will give that to you, correct?
And so therefore, if you have a decreased in
both of those compartments, what does the big “A”
mean? Alveoli. What does the little “a”
mean? Arterial. Do you remember that discussion?
So, if both are decreased, understand there’s
no widening, thus a normal A-a gradient. But
yet you have a pathology. What caused
this pathology? Was it drug induced inhibition
of your respiratory centre?
What else? Well, extrapulmonary poor muscle
effect. I told you about nerve conduction
issues, demyelinating disorders including
polio, myasthenia gravis, Guillain-Barré syndrome
or as we have mentioned earlier what
if there was a condition which was then resulting
your patient having a compromised chest cavity
making it difficult for the lung to then expand?
Welcome to things like scoliosis or morbid
obesity. Obesity has a whole host of issues
as you know. If that the type in which your
A-a gradient was normal but still restrictive,
what do we have here? Another type of restrictive
lung disease. This is damage within the lung
and by within the lung we’re referring to
it as being what? Interstitial lung disease.
What does interstitial mean? It is not the
alveoli, are we clear? Because once you start
destroying the alveoli it really wouldn’t
make sense initially to call this restrictive.
With alveoli destructions taking place remember
emphysema, that’s obstructive more so.
So, as a general rule of thumb you want to
keep yourself outside of the alveoli maybe
in the interstitium. What’s going on in
the interstitium? We’ll walk through a bunch
of differentials upcoming. Before I get
to any of that please understand that say
for example there’s fibrosis taking place
in your interstitium, you’re going to make
it difficult for carbon monoxide to then?
Good, pass through the membrane into the pulmonary
capillaries, are we clear? Therefore what
happens to DLCO? It decreases.
Next, what if you’re able to fill up the
alveoli which you can if the interstitium
has now become fibrosed, but that oxygen doesn’t
want to diffuse into the artery, the little
“a” what am I increasing in this
equation? The little bit equation what are
you increasing? Good, the big “A” is increasing,
the little “a” think of that as remaining
constant so therefore, what happens to A-a
gradient? Take a look please, widened or
increased A-a gradient. Where is my problem?
As a rule of thumb when you have an increase
in the A-a gradient, pulmonary. Good. In
the pulmonary what kind of diseases are we
looking at in terms of differentials? Maybe
there is idiopathic pulmonary fibrosis. What
happened in this patient perhaps? Well, the
patient began by having acute lung injury,
okay, acute. Ask you something, what if
something occurred over and over.
Would you call that acute?
At some point when you have enough
acute what then happens? It becomes chronic.
Becomes chronic for example, pancreatitis.
Acute pancreatitis, well may
lead into chronic pancreatitis. What does
chronicity mean to you? Chronicity to you
should mean repair, repair, repair. Fibroblast,
fibroblast, fibroblast. Collagen, collagen,
collagen and fibrosis, right? Good. So say
that you have repeated cycles of lung injury.
Lots of healing taking place, attempting
to. You’re laying down a lot of collagen,
there you go. That fibrosis that you’re
then depositing in the septae is your honeycomb
lung. So, what’s your honeycomb lung mean
to you? You know what a honeycomb looks like?
Close your eyes. It’s a lovely place where
the bees go to live and it fills up with honey.
You ever had honeycomb honey? It is the best.
Anyhow, so now that’s what your lung looks
like. The septae are very thickened, right?
Why? Because of fibrosis. Did that occur
quickly? No, repeated cycles of lung injury.
Now, if you’re having a hard time now, crossing,
exchanging your oxygen if hypoxemia, what
do the digits look like? The digits, the nails,
clubbing. Clear. So, if you have
hypoxemia you take a look at the digits and
nails, how would you know that your patient
over a long period of time is suffering from
hypoxemia? What’s clubbing mean? Looks like
the nail is then moving upward,
isn’t it? Good, move on.
What are the differentials? We will be spending
more time here not to worry. Sarcoidosis,
excellent in terms of its differential causing
interstitial lung disease. Should be thinking
non-caseating granuloma, you should be thinking
about African-American female, right? We’ll
talk more about that later right off the back.
Next, give you little clues here. Respiratory
distress syndrome, what’s happening here?
What’s NRDS mean to you? Neonatal respiratory
distress syndrome and for the most part by
definition a premature baby less
than 27 weeks would be the most common here
causing lack of surfactant we’ll talk more
about that later. Respiratory distress syndrome,
neonatal more so.
Pneumoconioses is a big topic for us, we’ll
talk about those individuals that are exposed,
and exposed and exposed to different occupations
and in that occupation maybe they’re working
in a mine and they were exposed to coal; maybe
they’re working in a mine and apart from
coal they were also exposed to silica, are
we clear? So these are pneumoconiosis. Take
a look at ANCA+. ANCA+ means GPA. Formerly
known as Wegener’s, it’s granulomatosis
with polyangiitis. What’s MPA? microscopic
polyangiitis and what’s EG? Eosinophilic
granulomatosis. Do you have every single one
of these? Oh yeah, right. So, two of these
are going to be pANCA and then one of these
will be cANCA. Which two are pANCA? Real quick,
MPA and Churg-Strauss. Dr. Raj, you didn’t
say Churg-Strauss, yeah I did. I said eosinophilic
granulomatosis, got you, joking. Anyhow
so keep that in mind eosinophilic granulomatosis,
Churg-Strauss that’s pANCA, with me? What
about cANCA? GPA. Continue.
What other differentials, what’s my topic?
Interstitial lung disease, your A-a gradient is
widened with a decrease in DLCO. Eosinophilic
pneumonia we’ll spend time with. Hypersensitivity
pneumonitis we’ll be spending time with.
Important differentials. Students tend to
get these confused, you will no longer do
that. So, if you were having issues with obstructive,
I hope that is clear as we went through the
classifications, current day practice and
such and with restrictive you’ll be clear
here as well with the various differentials
or maybe the interstitial lung disease and
restrictive was caused by drugs. For example,
bleomycin, nitrofurantoin, amiodarone all
these drugs that you should know about in
different settings. Maybe your patient required
antineoplastic, maybe your patient required treatment
for rheumatoid arthritis, maybe your patient
required some type of cardioversion right,
and so therefore, amiodarone becomes important.