0:01

Okay, it's Mark and we're going

0:03

to keep going with a bit of the

0:04

ground glass sort of motif here.

0:07

We're going to talk about the things

0:08

that sort of mimic ground glass.

0:12

Now, we're going to look at mainly a lot

0:14

of things about expiratory views because

0:16

that, to me, is one of the more common

0:17

causes, like how can you tell something

0:19

is an expiration on CT or on radiograph.

0:23

And also kind of introduce you to the

0:25

concept of using the DLCO, that's diffusing

0:27

capacity or diffusing measurement

0:30

of the pulmonary parenchyma, and that

0:32

can be very helpful in distinguishing

0:34

normal versus subtle ground glass.

0:36

And then we'll kind of look at the

0:38

differences of pleural effusion or

0:39

underexposure from ground glass.

0:42

There's a subtle difference

0:43

that you can usually tell.

0:45

So here's where we're going to be.

0:48

So when we talked about ground

0:49

glass, we said, here are the five

0:51

things that we should be doing.

0:52

But the very first thing before we even

0:53

get started is, is it really ground glass?

0:56

Or is this a mimic?

0:58

So, the problem with ground glass, and I'm

1:02

going to tell you this to write up,

1:03

there are people who are in sort of

1:05

mid-expiration on like CTAs, and there's

1:08

some subtle increased opacity. Is

1:11

that ground glass or is that normal?

1:12

And it's very

1:14

no, I don't want to say embarrassing, but you

1:16

know, it happens, you know, you don't want to

1:17

tell a clinician, “Well, it could be ground glass

1:19

diffuse lung disease or it could be normal.”

1:21

No, no, so you kind of say, what are

1:24

some ways we can figure this out?

1:26

And the first is truly to kind of get

1:28

an idea about what does it normally

1:29

look like on CT or in radiograph

1:32

during expiration. And then if you're still not

1:36

sure, then you just, you kind of go, well, suggest

1:39

a DLCO measurement or a repeat CT of full

1:42

inspiration, and we'll see if this is real,

1:45

and I think that's very reasonable as well.

1:47

So, this is me, uh, consider me the gold

1:51

standard. Got me all imaged, my lungs.

1:54

So this is me in inspiration.

1:55

Notice the bronchi. Then this is

1:58

the key now: the posterior wall, the

1:59

bronchi, and the trachea are rounded.

2:01

When we breathe out,

2:03

it flattens and even becomes a little

2:05

concave. When it's concave, that tells

2:08

you this is obtained during expiration.

2:11

What happens to the lung

2:12

parenchyma in expiration?

2:13

Well, notice how it kind of looks

2:15

like, oh, that's the dark bronchus sign.

2:17

This is ground glass.

2:19

Slow down.

2:20

It's an expiration, and in normal expiration,

2:23

the lung density gets higher, but it

2:25

gets disproportionately higher as you go

2:28

dependently, and that's kind of a key.

2:31

As you go down, it should be brighter.

2:35

That, to me, if I see that, I go, this is

2:38

consistent with a normal expiratory period.

2:41

Exam: so inspiration with trachea.

2:45

It's rounded posteriorly. With expiration,

2:48

it'll flatten or even indent. That's

2:51

expiration, and when you see something that

2:53

may be expiration, look for this gradual

2:56

increasing density posteriorly.

3:01

That's all, that's all expected.

3:03

What about for the radiograph?

3:05

Well, first of all, don't count ribs.

3:07

My God, people are like snowflakes.

3:09

My lungs go down to T12.

3:11

What does that tell you?

3:11

Well, you know, I got big lungs.

3:14

I have a rounded, uh, diaphragm.

3:16

It's not hyperinflated, but what you do want

3:19

to do is understand that the diaphragm is

3:21

actually a weak muscle, but when we take a

3:25

breath in, those stronger intercostal muscles

3:30

just kind of widen out; they pull the ribs out.

3:33

Now that is a lot less affected by what

3:37

lung diseases and various other problems.

3:39

So you want to start kind of looking at these

3:43

exams, making sure they're the same view,

3:47

AP to AP. Don't measure this intrathoracic

3:51

width from a PA and apply it to the AP.

3:53

That doesn't work.

3:55

And you measure it from the

3:56

inner rib, the widest part.

3:58

If you have that comparison,

4:00

this is the same patient.

4:01

This is an expiration.

4:03

This is not ground glass.

4:05

It's expected increasing

4:06

density and vascular crowding.

4:09

Okay.

4:10

Milne et al., uh, did a study in 1993 where they

4:13

looked at all of these radiographs and they

4:15

identified 120 patients with low lung volumes.

4:18

When they dove in deeper to see why, they

4:21

found that 105 of them had low lung volumes

4:23

because of intra-abdominal changes,

4:26

such as weight gain, pregnancy, or ascites.

4:29

They also found 11 that were reduced

4:31

because lung compliance was reduced.

4:33

When you, say, have congestive heart failure

4:35

or diffuse lung disease, the lungs stiffen.

4:38

You breathe in.

4:39

The intrathoracic cavity will still expand to

4:42

the same amount, but the diaphragm, the weaker

4:44

muscle, cannot descend to the same amount.

4:47

And then they only found four patients

4:49

where they felt, yep, this was actually a

4:51

person who did not take a deep breath in.

4:54

Uh, please avoid the term

4:55

poor inspiratory effort.

4:56

Looking at this, you'll find

4:59

that of all of these patients, only

5:01

four didn't take a deep breath in.

5:03

If the lung volumes are low, there's

5:05

an explanation there most likely.

5:08

This patient has acute dyspnea and hypoxia.

5:10

What's the main finding?

5:11

Well, this person's lung volumes are low.

5:13

Maybe it's

5:14

you know, they didn't take as deep a breath.

5:16

Well, when you measure the intrathoracic

5:17

width, they're exactly the same.

5:20

So they took in the same degree,

5:22

but the diaphragm would not descend.

5:25

The answer came about in 10 hours because they

5:28

developed diffuse, sort of a patchy or, say,

5:31

nodular but relatively uniform consolidation.

5:35

This was an acute lung injury

5:37

and this radiograph is the early

5:40

manifestation of acute lung injury

5:42

before the ground glass consolidation.

5:44

It's the reduced lung compliance.

5:47

If you had said poor inspiratory

5:48

effort, you would have missed it.

5:50

This patient has gradual increasing,

5:52

shortness of breath over a year.

5:55

You look and it's like, wow,

5:56

is that the same patient?

5:58

Must be an expiration scan.

6:01

Is that ground glass?

6:02

Or is that, Alexis?

6:05

And it turns out the

6:07

intrathoracic width is the same.

6:08

They took the same breath in.

6:10

That turned out to be ground glass.

6:12

It was biopsied, and it was DIP,

6:14

desquamative interstitial pneumonitis.

6:18

A patient who's got extrinsic allergic

6:19

alveolitis, look at the 10th rib,

6:21

that's where the diaphragm is.

6:22

These intrathoracic widths are exactly the same.

6:26

After the treatment, when the compliance

6:28

of the lungs returned to normal, the

6:29

diaphragm descended to a lower level.

6:33

Now we'll kind of apply it here.

6:35

A 49-year-old got a CTA.

6:37

This is what I'm talking about.

6:38

You'll notice the posterior

6:40

wall is sort of straightened.

6:41

So it's sort of like mid-expiration.

6:45

There is a dark bronchi sign.

6:46

Is this ground glass?

6:48

Is this expiration?

6:50

Um, hmm.

6:51

Well, shoot, that's hard.

6:53

What's one of the clues?

6:55

Does it get brighter as you go down?

6:58

No, it doesn't, does it?

7:00

This is relatively uniform.

7:02

So in your report, you would favor that this

7:04

is a ground glass process because there's

7:07

not that increasing density as you go down.

7:10

This patient did get a 76% of

7:14

predicted and they turned out that they

7:16

had basically hypersensitivity and

7:17

pneumonitis with some cellular NSIP.

7:20

So that was real ground glass.

7:22

It can be tricky and it can be tough.

7:26

So, last one, underexposed, large

7:29

patients, or pleural effusions.

7:32

This is an abnormality that's

7:33

outside the lung that can cause an

7:35

opacification and can mimic ground glass.

7:38

The key here is to look at the vessels.

7:41

These vessels are sharp.

7:42

That means that there is air around them.

7:46

Therefore, the opacification

7:48

is probably outside the lung.

7:50

In this case, it's pretty evident

7:51

because you can see that pleural effusion,

7:53

but that pleural effusion wraps around.

7:56

So if you have an increased area of

7:58

opacification, can you see the vessels sharply?

8:00

Yes.

8:01

Let's think that this is a mimic and it's

8:03

something outside the lung, like pleural fluid

8:06

or an underexposed exam.

8:09

So the mimics, they still occur.

8:12

You're going to encounter them.

8:13

It can be confusing sometimes to tell if this

8:15

is a ground glass process or normal lungs.

8:18

Look at the increasing density of the

8:21

density and look for the intrathoracic width.

8:23

Is it the same?

8:25

If you're not sure, consider doing a CT scan

8:30

of full inspiration or referral for a diffusing

8:34

PFT measurement because that's pretty helpful.

8:36

If it's normal, it was probably just normal lung.

8:39

And as always, don't say

8:40

poor inspiratory effort.

8:42

With that, I thank you very much.