0:01

Okay, cardiopulmonary imaging,

0:02

atelectasis session two.

0:04

This one's going to be a

0:05

little bit of a myth-buster.

0:07

If you're still teaching that atelectasis

0:09

causes fever, you need to stop.

0:12

So let me show you why.

0:14

This is, it's based on some false,

0:17

uh, false information and a lot

0:19

of dogma that got carried through.

0:21

Um, but it does not cause fever.

0:24

And the other thing we're going to look

0:25

at after that is that understanding

0:28

that atelectasis and consolidation look

0:30

very different on CT with convalescence.

0:33

Contrast atelectasis enhances differently.

0:36

So there's no real reason to just say,

0:38

well, it could be atelectasis or consolid.

0:40

No, you can tell between the two.

0:43

So again, morphologic patterns were

0:46

in the increased capacity atelectasis.

0:47

This is the second session.

0:50

And we'll start you right off by seeing that

0:52

there is a pacification here, sharply marginated.

0:56

You can see the minor fissures deviated

0:58

inferiorly, no bronchograms.

1:00

And there's no fever.

1:01

This is a mucous plug and atelectasis within

1:04

the right lower lobe, post-obstructive.

1:07

Now, if this patient's on the I.C.

1:08

or, um, medicine service and they

1:09

see this and they go, Huh, atelectasis,

1:11

I thought that caused fever.

1:13

No, no, people don't tend to do that.

1:15

They just kind of, they have fever and then

1:18

they look and they go, oh, it's the atelectasis.

1:22

When in fact,

1:24

you got to keep looking at something else.

1:27

So, uh, Chest Volume, uh, Chest Volume 107,

1:32

you can go see this paper, 1995, prospectively

1:35

evaluated 100 postcardiac patients,

1:37

and they demonstrated an inverse relationship

1:39

between post-op fever and atelectasis.

1:41

That is, as the atelectasis improved,

1:44

a lot of people were getting fevers.

1:46

Okay, so there was no association there.

1:49

Again, we have patients with hypoxia because

1:52

atelectasis does give hypoxia because essentially

1:54

it's shunting blood through without being

1:57

oxygenated, but it does not cause fever.

2:00

Another one came out of Chest in April,

2:02

2011, where they evaluated the studies

2:06

and it, yeah, they could not find any

2:09

pathophysiologic explanation or any,

2:12

uh, studies to really support it.

2:15

So where did it come from?

2:17

Well, this whole atelectasis causes fevers

2:19

from the early 1900s and 1950s when many

2:22

physicians, especially surgeons, did not

2:24

distinguish between atelectasis or pneumonia.

2:26

They used them interchangeably.

2:29

And then in 1963, these folks did a study and

2:32

they placed nonsterile, nonsterile cotton

2:35

plugs in the left main bronchus and 30 docs.

2:37

Most developed fever in 12 hours.

2:39

How about that?

2:40

Uh, on autopsy, inflammation,

2:42

obstructive pneumonia were actually seen.

2:45

Six became septic.

2:47

That's right, septic from atelectasis.

2:49

No, that's all post-obstructive pneumonia.

2:52

And in the same paper, they actually

2:54

stated, it's interesting the antibiotics

2:56

improve the fever, not the atelectasis.

2:59

In conclusion, atelectasis is the cause for fever.

3:02

Okay, you can see there that those don't connect.

3:05

Okay, what else?

3:07

Well, this one gets quoted to me

3:08

from surgeons from time to time.

3:10

Rats were given one atelectatic lung.

3:12

The contralateral lung was normal.

3:14

And then they bronc the atelectatic lung,

3:16

and they found, "Hey, look, there's more

3:18

cytokines and tumor necrosis factor."

3:21

Our theory is that hypoxia-induced activation

3:24

of the alveolar macrophages induces the fever.

3:27

Therefore, this is the likely

3:28

mechanism, but one line in the results.

3:32

None of the rats became febrile.

3:35

None of the rats became febrile.

3:37

That was just skipped over.

3:39

Okay, right lower lobe collapse,

3:42

no air bronchograms, bronchial cutoff.

3:44

I've shown this one before.

3:45

There's no fever.

3:47

Okay, atelectasis does not cause fever.

3:49

Now this person, notice this,

3:52

it's a little different.

3:53

The atelectasis is not sharply marginated.

3:55

It's a bit more ill-defined.

3:57

It is kind of triangular, but it

3:59

does extend pretty far and this

4:01

one extends down to the lower lobe.

4:03

Because it's ill-defined, I start to wonder

4:05

about the possibility of aspiration pneumonitis,

4:08

which is a cause of low-grade fever.

4:10

So if a person's got something that looks

4:12

like atelectasis, maybe a little ill-defined,

4:15

dependent, low-grade fever, you could

4:17

suggest retained secretions or aspiration.

4:21

As opposed to this person,

4:22

who has high spiking fevers.

4:24

And high white count.

4:26

Well, this doesn't look like atelectasis at all.

4:28

Anyway, it's very ill-defined.

4:30

It's peripheral, it's not triangular,

4:32

doesn't radiate from the hilum.

4:34

This is bacterial or nosocomial pneumonia.

4:39

So they look different now quickly CT enhancement

4:42

um Consolidation because the vessels are all

4:46

spread apart tends to enhance but not to a

4:49

great degree atelectasis like here Everything is

4:55

crowded together It will in fact enhance brightly.

5:00

So one way to do this is just take a look at what

5:03

you're seeing and then look at the paraspinal

5:06

muscle. Okay, is it the same? It's going to

5:09

be consolidation. Atelectasis will blush much

5:13

brighter and will be much brighter than the

5:16

paraspinal muscle. So if it looks a lot brighter,

5:19

it's atelectasis most likely. If it's about the

5:22

same, that's consolidation. Another nice example

5:27

Consolidation. Atelectasis enhances much more.

5:31

And there's what the pleural fluid looks like.

5:33

So based on enhancement and comparing it

5:35

to the paraspinal, you should come down

5:37

pretty hard on one or the other and not kind

5:41

of just put them all always in the same.

5:43

Well, it could be atelectasis or pneumonia.

5:45

You don't have to do that.

5:46

You don't have to do that.

5:48

So, uh, summary, atelectasis

5:51

is not a cause for fever.

5:52

If someone's teaching you this, uh, walk away.

5:58

If the patient has fever, look elsewhere.

6:01

Aspiration, when it does occur, will be a little

6:03

more ill-defined, tends to be a low-grade fever.

6:06

If it's a high-grade fever, an elevated

6:08

white count, infectious pneumonia.

6:10

And on CT with contrast, atelectasis will

6:13

blush and enhance much greater than

6:15

consolidation, and you can use the paraspinal

6:17

muscles as your standard of reference.

6:20

With that, thank you very much.