A 62 year old man presents
to the emergency department
because of a 2-year history of
increasing shortness of breath.
He also has had occasional
His symptoms get worse with exertion.
His medical history is significant for
hypertension for which he takes chlorthalidone.
Of note, he is a smoker with a
40 pack year smoking history.
On physical examination, the patient is afebrile, blood pressure
is 125/78, pulse is 90 respiratory rate is 18 and BMI is 31.
Oxygen saturation test
on room air is 94%.
Pulmonary examination reveals
decreased breath sounds bilaterally
but is otherwise normal with no whezes or crackles.
The remainder of the examination in unremarkable.
Chest radiograph reveals hyperinflation of both lungs with
mildly increased lung markings but no focal findings.
Based on this patient's clinical presentation, which of
the following is most likely to be found in this patient?
Answer choice (A) - FEV1 to FVC ratio of 65%
Answer choice (B) - decreased
total lung capacity
Answer choice (C) - increased DLCO
Answer choice (D) - metabolic acidosis
and Answer choice (E) - FEV1 of 82%
Now take a moment to come to the answer by
yourself before we go through it together.
Now let's jump right in to this question.
Let's discuss the question characteristics.
Now this is a pathology question,
we have someone who's smoking,
with shortness of breath and
cough, and is affecting the lungs.
So this is rspiratory pathology.
This is a 2-step question.
We have to determine the diagnosis of the patient
and the lung function test result we would expect.
And the stem is absolutely required.
Not only get history but also get laboratory findings and
radiograph findings to better understand the condition.
Now let's walk through this question together.
The first thing we need ot do is
determine the likely diagnosis.
Now this patient's characteristic signs and
symptoms are consistent with emphysema,
a chronic obstructive
pulmonary disease or COPD.
Now smoking is the leading cause of COPD and
this patient has a significant smoking history
of a 40-pack year smoking
history which is very high.
Now let's refer to our image here of COPD, 2
subtypes of chronic bronchitis and emphysema
to better understand the condition before we
go through the rest of our answer walkthough
and pick our answer to better
understand this condition.
Now COPD has 2 subtypes - chronic
bronchitis and emphysema.
Starting with chronic bronchitis, we can see
an image there first of a healthy bronchi.
Now bronchitis breaks down to the word bronchi-
which means the bronchioles or the airway
and -itis which is inflammation and
chronic is the chronicity of this event.
So in the healthy case, the airway is
open and there is not much mucus.
below we see the case of chronic bronchitis in which
we see inflammation and excess mucus production
which is gonna lead to cough
and difficulty expiring air.
Now on the right there, we see emphysema.
Now the image there of a healthy alveoli is often described
as grapes on a vine, that's kind of what it looks like.
But below we see alveolar
membranes break down in emphysema
and we no longer have that nice delineation of the alveoli
and we actually have a change in our total surface area
leading to decreased gas transfer and also as we have breakdown of the alveolar membranes
we actually have lots of recoil in our alveoli
which also makes it difficult to expire air,
both very important to understand this condition.
Now let's go back to step 2 of our walkthrough.
Now that we have determined this patient's condtion as
COPD and we've reviewed the 2 clinical subtypes of COPD,
let's determine the likely lung function
test we would expect in this patient.
Now, COPD is characterized - this is very
important, by a reduction in FEV1 by FVC ratio
but it is important to understand why.
This reduction in the ratio is due to a reduced
FEV1 which is due to compromised expiratory flow
and that due to both inflammation, the increased
mucus and also to the decreased lung recoil
from alveolar membrane breakdown.
The patients will have a normal vital capacity,
thus the numerator in this case will decrease
while the denominator stay the same
and thus the ratio is reduced overall.
Now in emphysem, the alveolar walls are destroyed which
actually decreases the overall surface area for gas transfer
and that will result in a decreased diffusion capacity or
DLCO, not increased as it was noted in answer choice (C)
so it is wrong.
And total lung capacity is increased in emphysema due to
hyperinflation not decreased as noted in answer choice (B).
So the correct answer here is answer choice (A)
FEV1 over FVC ratio of 65 percent,
which is how we characterized COPD.
And we've also described the physiological background
as to why vital capacity would stay the same
in our forced expiratory volume
over one interval will decrease.
Now let's review our high-yield
facts regarding COPD.
And the leading cause of COPD is smoking .
And COPD as we've discussed has two subtypes
- chronic bronchitis and emphysema.
Bothof these types of COPD are characterized by increased
shortness of breath due to airways obstruction,
with spirometry showing a reduced FEV1 to FVC ratio
below 70% which is the lower limit of normal.
Now emphysema is characterizd by destrcution of alveolar
walls with the loss of elastic recoil of the lungs
resulting in hyperinflation and
increased total lung capacity.
And chronic bronchitis is characterized by increase in
mucus production and inflammation resulting in cough
and total lung capacity is also increased.